Core Science 4 Book

core science Stage 4 Complete course

Paul ARENA Pascale WARNANT ahni BURROWS Graeme LOFTS Merrin J EVERGREEN

First published 2009 by John Wiley & Sons Australia, Ltd 42 McDougall Street, Milton, Qld 4064 First edition published 2009 Typeset in 10.25/13pt ITC Giovanni LT Book © Paul Arena, Kahni Burrows, Pascale Warnant, Clynton Educational Services Pty Ltd, Evergreen Quest Pty Ltd 2009 The moral rights of the authors have been asserted. National Library of Australia Cataloguing-in-publication data Title:

Core science stage 4 complete course/ Paul Arena [et al.]

ISBN:

978 0 7314 0873 3 (pbk.) 978 1 7421 6135 8 (web).

Notes:

Includes index.

Target audience:

For secondary school age.

Subjects:

Science — Textbooks.

Other authors/contributors:

Arena, Paul.

Dewey number:

500

Reproduction and communication for educational purposes The Australian Copyright Act 1968 (the Act) allows a maximum of one chapter or 10% of the pages of this work, whichever is the greater, to be reproduced and/or communicated by any educational institution for its educational purposes provided that the educational institution (or the body that administers it) has given a remuneration notice to Copyright Agency Limited (CAL). Reproduction and communication for other purposes Except as permitted under the Act (for example, a fair dealing for the purposes of study, research, criticism or review), no part of this book may be reproduced, stored in a retrieval system, communicated or transmitted in any form or by any means without prior written permission. All inquiries should be made to the publisher. All activities have been written with the safety of both teacher and student in mind. Some, however, involve physical activity or the use of equipment or tools. All due care should be taken when performing such activities. Neither the publisher nor the authors can accept responsibility for any injury that may be sustained when completing activities described in this textbook. Cover images: © Digital Vision, © Photodisc, © Viewfinder Australia Photo Library Internal design images: © Digital Stock/Corbis Corporation, © Digital Vision, © Digital Vision/Martin Child, © Photodisc, Inc., © Stockbyte Cartography by MAPgraphics Pty Ltd, Brisbane Illustrated by Robert Allen, Susy Boyer, Geoff Cook, Dr Levent Efe, Mike Gorman, Steve Hunter, Craig Jackson, Alan Laver, Paul Lennon, Glenn Lumsden, Janice McCormack, Terry St Ledger, Bronwyn Searle and the Wiley Art Studio Printed in Singapore by Craft Print International Ltd 10 9 8 7 6 5 4

contents About eBookPLUS

vii

3.6

About this book viii Core Science and the Science Stage 4 syllabus Useful verbs

3.7

xiii

Fit to drink? 78

4 Classification

2

What do scientists do? 4 The science laboratory 7 Observing and inferring 14 Reporting on investigations 20 Designing investigations 25 PRESCRIBED FOCUS AREA NATURE AND PRACTICE OF SCIENCE AND HISTORY OF SCIENCE

4.1 4.2 4.3 4.4 4.5 4.6 4.7

Famous scientists 29 Looking back 32 Study checklist/ICT

36

What s the matter? 38 Changing states 40 The particle model 43 Change of state and the particle model Density 48 Expansion and contraction 50 Under pressure! 52

46

Other states of matter? 54 58

3 Separating mixtures

83

Is it alive? 85 Identification keys 89 In a class of its own 92 Which animal is that? 95 Vertebrates 97 Australian mammals 100 PRESCRIBED FOCUS AREA CURRENT ISSUES, RESEARCH AND DEVELOPMENT

Looking back 111 Study checklist/ICT

PRESCRIBED FOCUS AREA CURRENT ISSUES, RESEARCH AND DEVELOPMENT IN SCIENCE

Looking back 56 Study checklist/ICT

82

Australian scientists at work 102 4.8 Invertebrates 104 4.9 The other kingdoms 108 4.10 PRESCRIBED FOCUS AREA CLASSIFICATION IN OTHER CULTURES Is it a bird? Is it a plane? No, it s a yakt! 110

35

2 States of matter 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8

PRESCRIBED FOCUS AREA APPLICATIONS AND USES OF SCIENCE

Looking back 80 Study checklist/ICT

1 Investigating 1.1 1.2 1.3 1.4 1.5 1.6

x

xii

Acknowledgements

PRESCRIBED FOCUS AREA APPLICATIONS AND USES OF SCIENCE

Down the S-bend 76

59

3.1 Separating substances 61 3.2 Looking for solutions 64 3.3 Separate ways 67 3.4 PRESCRIBED FOCUS AREA APPLICATIONS AND USES OF SCIENCE Separating blood 70 3.5 Separating solutions 72

5 Cells 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9

113

114

Using a microscope 116 A whole new world 119 Living things are made up of cells 122 Zooming in on life 124 Revisiting the five kingdoms 127 Cells of all shapes and sizes 130 Focus on plants 133 Tissues and organs 135 PRESCRIBED FOCUS AREA IMPLICATIONS OF SCIENCE FOR SOCIETY AND THE ENVIRONMENT

Stem cells

a matter of opinion

Looking back 140 Study checklist/ICT

142

137

6 Forces in action 6.1 6.2 6.3 6.4 6.5 6.6

What are forces? 145 Friction 149 Magnetic forces 154 Gravitational forces 160 Buoyancy and surface tension

167

Looking back 169 Study checklist/ICT

7 Planet Earth

172

PRESCRIBED FOCUS AREA CURRENT ISSUES, RESEARCH AND DEVELOPMENT

185

188

Looking back 190 Study checklist/ICT

193

The planets: then there were eight 195 Terrestrial neighbours and gas giants 197 A very important star 203 The Earth in motion 205 The moon in motion 209 Ocean tides ebb and flow 212 Lunar and solar eclipses 214 PRESCRIBED FOCUS AREA HISTORY OF SCIENCE

Early ideas in astronomy 217 8.9 Rocks in space 222 Looking back 224 Study checklist/ICT

iv

Contents

Looking back 255 Study checklist/ICT

10.1 10.2 10.3 10.4 10.5 10.6 10.7 10.8

257

part 1

Energy for living 260 All systems go 263 Breathe in, breathe out Short of breath? 271 Up in smoke 273 Blood highways 275 Have a heart 277

258

267

PRESCRIBED FOCUS AREA APPLICATIONS AND USES OF SCIENCE

226

Looking back 285 Study checklist/ICT

11 Bits of matter

192

8 The solar system 8.1 8.2 8.3 8.4 8.5 8.6 8.7 8.8

9.1 Energy transformations 229 9.2 Heat and temperature 235 9.3 Light and sound energy 244 9.4 PRESCRIBED FOCUS AREA APPLICATIONS AND USES OF SCIENCE Sound technology 253

Transport technology 282

PRESCRIBED FOCUS AREA CURRENT ISSUES, RESEARCH AND DEVELOPMENT

Rising salt

227

10 Body systems

171

Introducing the Earth 174 Water world 177 The air up there 180 Under pressure 183

Wild weather

7.6

165

PRESCRIBED FOCUS AREA APPLICATIONS AND USES OF SCIENCE

Staying alive

7.1 7.2 7.3 7.4 7.5

9 Energy

143

11.1 11.2 11.3 11.4 11.5 11.6 11.7 11.8

287

288

Atoms 290 It s elementary! 293 Grouping elements 295 Compounds 297 Mixed up metals 300 Making molecules 301 Carbon the stuff of life 303 PRESCRIBED FOCUS AREA HISTORY OF SCIENCE

Development of the atomic model Looking back 308 Study checklist/ICT

310

306

12 Chemical reactions 12.1 12.2 12.3 12.4 12.5 12.6 12.7

Time for a change? 313 Describing chemical changes 316 Faster and slower 318 Rusting is a chemical reaction 321 Burning is a chemical reaction 323 Acids and bases 325 PRESCRIBED FOCUS AREA CURRENT ISSUES, RESEARCH AND DEVELOPMENT

Acid rain

328

Looking back 330 Study checklist/ICT

13 Plants 13.1 13.2 13.3 13.4 13.5 13.6 13.7

15 Ecology

311

15.1 15.2 15.3 15.4 15.5 15.6 15.7 15.8 15.9

332

387

A place to call home 389 Investigating the environment You scratch my back 396 Food chains and webs 398 Natural recyclers 402 It s getting hot in here 405 Fired up for change 409 Floods and droughts 412

PRESCRIBED FOCUS AREA CURRENT ISSUES, RESEARCH AND DEVELOPMENT

Being part of the solution Looking back 418 Study checklist/ICT

333

Plants have organs too! 335 Hold and carry 338 Leafy exchanges 340 Investigating photosynthesis 343 The sex life of plants 346 Plants and parenthood 348 PRESCRIBED FOCUS AREA NATURE AND PRACTICE OF SCIENCE

16 Electricity

421

16.1 Static electricity 423 16.2 Electric circuits 429 16.3 Electricity at work 434 16.4 PRESCRIBED FOCUS AREA APPLICATIONS AND USES OF SCIENCE The next generation of motor cars 440 Looking back 442 Study checklist/ICT

Looking back 356 Study checklist/ICT

17 Staying healthy

14 Body systems

part 2

359

14.1 Food as a fuel 361 14.2 Essential intake 364 14.3 Healthy eating 367 14.4 PRESCRIBED FOCUS AREA CURRENT ISSUES, RESEARCH AND DEVELOPMENT

14.5 14.6 14.7 14.8 14.9

Science careers: dietitian 369 The digestive system 370 Mechanical digestion 373 Chemical digestion 375 Bodies on the move 378 Getting rid of waste 382

Looking back 385 Study checklist/ICT

414

420

Plant research project 350 13.8 Which plant? 353 358

392

17.1 17.2 17.3 17.4 17.5

444

445

Catch us if you can 447 Germs everywhere 449 The good, the bad and the ugly Viruses living or not? 453

451

PRESCRIBED FOCUS AREA APPLICATIONS AND USES OF SCIENCE

A weapon against germs 455 17.6 Skin deep 457 17.7 Skin cancer 459 17.8 PRESCRIBED FOCUS AREA CURRENT ISSUES, RESEARCH AND DEVELOPMENT

Healthy careers Looking back 464 Study checklist/ICT

462 465

386

Contents v

18 The night sky

466

18.1 A sense of perspective 468 18.2 Stars and constellations 472 18.3 PRESCRIBED FOCUS AREA APPLICATIONS AND USES OF SCIENCE Probing the universe 478 Looking back 483 Study checklist/ICT

484

19 The changing Earth 19.1 19.2 19.3 19.4 19.5 19.6 19.7

Solid rock 487 Fiery rocks 489 Wearing away 492 It s sedimentary, Watson! 495 Rocky changes 497 Tracking changes in rock 500 PRESCRIBED FOCUS AREA CURRENT ISSUES, RESEARCH AND DEVELOPMENT

Human-made erosion 503 Looking back 505 Study checklist/ICT

vi

485

Contents

507

20 Student research project and skills 508 20.1 20.2 20.3 20.4 20.5 20.6 20.7 20.8 20.9

Choosing a problem 510 Thinking about your problem 513 Organising your thinking 518 Research and record keeping 521 Designing your method 524 Presenting your results 528 Using technology: spreadsheets 533 Using technology: databases 535 Writing your report 538

Looking back Text types Glossary Index

542 543

559

540

Next generation teaching and learning About eBookPLUS This book features eBookPLUS: an electronic version of the entire textbook and supporting multimedia resources. It is available for you online at the JacarandaPLUS website (www.jacplus.com.au).

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About eBookPLUS vii

About this book The Core Science Stage 4 textbook, eBookPLUS and student workbook are designed for students who come to the science classroom with a range of interests, backgrounds and learning styles. The topic units provide an in-depth coverage of essential and additional syllabus content. Each unit provides a range of investigations, stimulus material and activities to engage and challenge students, as outlined in this summary of Core Science features. Thought-provoking chapter openings, including a summary of the key content covered in each unit

2

States of matter

All substances on Earth can be grouped as solids, liquids or gases. By comparing the properties of solids, liquids and gases, you can begin to answer questions like ‘what are substances made of?’ This question has fascinated people for thousands of years, and scientists are still looking for more answers to that same question.

Ranking substances

Bathroom science

1. In small groups, rank the following substances in order from most solid-like to most liquid-like to most gas-like. a brick steam jelly plasticine sugar tomato sauce Vegemite® air orange cordial green slime

1. Why does the mirror fog up in the bathroom after someone has had a hot shower? 2. On really hot days, you may have a cold shower to cool down. Does the bathroom mirror fog up when you do this? 3. Some showers have shower curtains rather than glass shower screens. When people have warm showers, the curtain tends to move in towards the person in the shower and stick to them — it’s almost as if the shower curtain is chasing them! Give possible explanations for why this happens. 4. When you have a hot shower, the bathroom fills with steam. Is this steam a gas or a liquid or both? Explain your reasoning.

In this chapter, students will: 2.1 W investigate the nature of matter and

look at the properties of the different states of matter

Green slime — is it solid or liquid? How do you know?

2.2 W explore the processes by which

2. Compare your rankings with those of other groups. Comment on any differences between the rankings. 3. Which substances were most difficult to classify as solid, liquid or gas? Explain why they were difficult to classify. 4. Draw a three-column table, like the one below, and separate the substances into three categories — solid, liquid or gas.

substances change state

2.3 W use the particle model of matter to

understand the behaviour of the different states of matter

2.4 W use the particle model to show the

interaction of particles and energy when substances change state

Solid

2.5 W use an equation to calculate density

Liquid

Gas

and explain why some substances sink in water while others float

What is steam — a gas, a liquid, or both?

2.6 W observe how heating and cooling of

5. How hot does water have to be before it can burn you? 6. Does steam always rise? 7. Are water vapour and steam the same thing?

substances causes expansion and contraction 2.7

W learn how the expansion of gases

affects the pressure of the gas

2.8 W discuss the continuing research into

other states of matter.

Water is the only substance found in three different states at normal air temperatures. It exists as a liquid in oceans, lakes and rivers, as solid icebergs in the oceans, and as water vapour in the air. Without it, plants and animals could not exist. Each of the forms of water has its own different properties and uses.

Activities at the end of each unit cover a full range of lower to higher order activities, including eBookPLUS interactivities. The blue bolded words in questions highlight use of the key verbs that are applied in HSC exam questions. These questions give students some practice in answering this style of question, using the key words most relevant to stage 4 students.

2.7 ‘The firefighter charged through the doors just in time, pointed the extinguisher at the electrical fire and pressed the trigger. A huge burst of carbon dioxide gas came squirting out of the nozzle, putting out the flames.’ The carbon dioxide in the story above could be used in this way only because huge amounts of it can be compressed, or squeezed, into a container. Gases can be compressed because there is a lot of space between the particles. Gases compressed into cylinders are used for barbecues, scuba diving, natural gas in cars, and aerosol cans. Hot-air balloons work on the idea that gases expand when heated. The particles in the heated gas move about more and take up more space. This makes each cubic centimetre of hot air in the balloon lighter than each cubic centimetre of air outside the balloon, so it rises, taking the balloon with it.

Fighting fire

1. Gases, including carbon dioxide, have lots of space between their particles.

52

viii

Core Science | Stage 4 Complete course

About this book

Fluids can float on top of other fluids, with the less dense fluid on the top. Oil is less dense than water. This is why oil spilled from wrecked tankers floats on the top of the ocean.

INVESTIGATION 2.6

sit undisturbed for 30 minutes.

Sinking and floating

DISCUSSION

You will need: 250 mL beaker 3 test tubes test-tube rack 20 mL measuring cylinder brown vinegar water olive oil honey W Pour 20 mL each of vinegar, olive

oil and honey into separate test tubes.

W Add 20 mL of water to each test

tube.

W Pour 20 mL each of vinegar, olive

Cooking oil is less dense than water so it floats on top.

oil and honey into the beaker.

Activities REMEMBER 1 Identify what the units of density would be if: (a) mass is in kilograms and volume is in cubic metres (b) mass is in grams and volume is in millimetres (c) volume is in cubic centimetres and mass is in kilograms. (Note: This density unit is usually used only with extremely dense objects such as neutron stars!)

Investigations in each chapter reinforce the topic concepts and provide a comprehensive practical program for stage 4 students. Investigations are placed in context, to help students relate their practical work findings to topic concepts.

W Let the test tubes and the beaker

1

How could you tell if a particular liquid was less dense or more dense than water?

2

Which of the liquids were denser than water?

3

Which of the liquids were less dense than water?

4

Draw a labelled diagram showing the order of the layers formed in the beaker.

5

Based on what you saw in the beaker, which was the: (a) densest liquid (b) least dense liquid?

CHAPTER 2: States of matter

Worksheet 2.4

Accompanying worksheets can be found in the student workbook and as Word files in eGuidePLUS.

CALCULATE 8 Use the density equation on the previous page to calculate the missing values in the following table. Mass (g) 10

Volume (cm3)

Density (g/cm3)

5 40

600

0.5 15

9 Explain why this ship is sinking in the water when the boats in the background of the photo are still afloat.

2 If you take a bottle of salad dressing out of the fridge, you may notice that the oil and the vinegar have separated into different layers. Explain why this occurs.

Under pressure! eLesson

eles-0058

7 When divers breathe out under water, the air bubbles head straight to the surface. Deduce why this happens.

3. The carbon dioxide particles are now under increased pressure. This means that the particles in the gas collide frequently with the walls of the cylinder. The particles push outwards on the walls of the cylinder. The particles are trying to escape, but are held in by the container.

5. The particles of gas quickly spread out over the fire. The gas smothers the fire, stopping oxygen from the air getting to it. Fires cannot burn without oxygen, so the fire goes out.

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10 Select liquids and solids in the Density interactivity in your eBookPLUS and see what sinks and what floats. int-0221 work sheets

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2.4 Density 2.5 Density and flotation

2 States of matter

4. When the nozzle is opened, the pressure forces the carbon dioxide gas out very quickly through the opening.

2. The carbon dioxide is compressed into the cylinder. The particles are squashed closer together.

6 Equal amounts of vegetable oil, water and methylated spirits are poured into a jar. Identify which liquid will form: (a) the top layer (b) the lowest layer.

Date:

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4 Explain why balloons filled with helium float upwards.

Under pressure Learn about the factors that affect the pressure of a gas and how compressed gases are used to make fire extinguishers and aerosol cans.

Class:

1. Heating and density

HjWhiVcXZ

3 Explain why most people float in water. 5 Describe the general relationship you notice between a substance’s state of matter and its density. (Use the table of densities on the previous page as a guide.)

Core Science Stage 4: page 49

Density Student:

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THINK

eBook plus

Chapter opening activities and investigations can be used to: • show connections between science and students’ own experiences • provide opportunities for students to demonstrate their current thinking on topic concepts.

Units include descriptions of eLessons, interactivities and weblink-based activities available in eBookPLUS.

49

© John Wiley & Sons Australia, Ltd 2009

Core Science Stage 4 Student Workbook

1

2.8

Other states of matter? In the past, scientists believed that everything around us was either a solid, a liquid or a gas. But scientists now believe that there are other states of matter that are not very common on Earth. The earliest of these additional states of matter to be identified is called plasma. It is currently estimated that more than 99 per cent of all matter in the universe is actually plasma. Plasma occurs everywhere. The sun and all the other stars are made of plasma, as is lightning and the aurora australis (also known as the southern lights). Temperatures higher than 1 000 000 °C are needed to form

these plasmas. Lightning bolts actually form plasma from the surrounding air. In an ordinary gas, each atom contains an equal number of protons and electrons. (We will learn more about the particles that make up the atom in chapter 11.) This makes each atom neutral. The positively charged protons are surrounded by an equal number of negatively charged electrons. A gas becomes plasma when energy or heat is added. This energy or heat causes the atoms to release all or some of the electrons. This means that the remaining atoms now have fewer electrons and the atoms have

a positive charge. The removed electrons are free to move about. Energy knocks electrons off atoms. –

2.3

Prescribed focus area units in each chapter provide highinterest content that explicitly links particular areas of the Science syllabus.

PRESCRIBED FOCUS AREA Current issues, research and development in science

The particle model How do you explain why ice has properties that are different from those of water or steam? Scientists use a model to explain the different properties of solids, liquids and gases. This model is called the particle model. According to the particle model: sõ all substances are made up of tiny particles sõ the particles are attracted towards other surrounding particles sõ the particles are always moving sõ the hotter the substance is, the faster the particles move.

–

Protons

–

–

++ ++

–

Nucleus

Liquid

Gas

Solid

A particle model for different states

Neutrons –

Particles in a gas

Incoming energy removes electrons from gas atoms, changing them into a plasma state.

The forces between the particles in a gas are very weak. The particles are in constant motion. This means that gases have no fixed shape or volume. There are large spaces between the particles. The spaces allow the gas to be compressed. A gas can flow and diffuse easily since its particles are always moving. Particles in a gas have much more energy than particles in a solid or liquid. They move around and collide with other particles and the walls of the container they are in.

Concepts are explored through visually stimulating and detailed diagrams that engage visual and linguistic learners.

Particles in a solid

Solids cannot be compressed because the particles inside them are held closely together. There is no space between them. Bonds also hold the particles tightly together in a rigid crystal-like structure. This gives solids their fixed shape and constant volume. The particles in solids cannot move freely; they vibrate in a fixed position. This means that solids are unable to flow.

Particles in a liquid

The particles in a liquid are close together, so there is no room for compression between them. The particles are also held tightly by bonds, but not in the same rigid structure as solids. This gives liquids their fixed volume, but allows the particles to roll over each other. This rolling allows liquids to flow. The movement of the particles explains why liquids take the shape of their container. The particles roll over each other until they fill the bottom of the container.

Lightning turns gases in the air into plasma at temperatures higher than 1 000 000 °C.

54

Core Science | Stage 4 Complete course

2 States of matter

43

LOOKING BACK

Looking back spreads provide a range of chapter review activities.

1 Use the particle model to explain why steam takes up more space than liquid water.

7 Copy and complete the diagram, labelling the missing state and changes of state.

2 Recall in which state the forces of attraction between the particles are likely to be greatest.

11 Graphite (used in pencils) and diamond are both made of the same type of particle, yet graphite has a density of 1.46 g/cm3 while diamond has a density of 3.52 g/cm3. Give possible explanations for how they can have different densities yet be made of identical particles.

?

3 Identify in which state — solid, liquid or gas — the particles have: (a) the most energy (b) the least energy. 4 Explain why perfume and aftershave lotion evaporate more quickly than water.

Solid

Liquid

Gas

Has a definite shape that is difficult to change

?

Freezing

?

Solid

5 Copy and complete the table below to summarise the properties of solids, liquids and gases. Use a tick to indicate which properties each state usually has. Property

Melting

12 A mysterious substance is developed in a laboratory. The sample has a mass of 10 g and has a volume of 2.3 cm3. (a) Calculate its density. (b) What is the mystery substance’s most likely state of matter?

TEST YOURSELF

Gas

1 ‘Compression’ is a term that describes A squeezing the particles of a substance closer together. B pulling particles further apart. C removing the heat energy from the particles of a substance. D the releasing of air from a car tyre. (1 mark)

8 Fully explain the process that is occurring in the following diagrams.

2 Ice cubes float in soft drink because A the bubbles in the soft drink hold them up. B the ice is less dense than the soft drink. C the ice is denser than the soft drink. D water and soft drink do not mix.

Takes up a fixed amount of space Can be poured Takes up all of the space available Can be compressed Is made of particles that are strongly attracted to each other and can’t move past each other Is made of particles that are not held together by attraction 6 Copy and label the three diagrams below to identify which represent solids, liquids and gases. Make an improvement to each of the diagrams so that they describe the particle model more fully. (a)

(b)

(1 mark)

3 Gaps are left between sections of railway track so that A more track can easily be laid later. B bugs can cross the railway lines safely. C the steel tracks can expand in cold weather without buckling the track. D the steel tracks can expand in hot weather without buckling the track. (1 mark)

9 Identify which of these diagrams (A, B or C) correctly shows a solid after expanding.

4 According to the particle model, the attractive forces between particles are strongest in A solids. B liquids. C gases. D plasma. (1 mark)

Original solid

(c)

5 Read the information in the box above right. (a) Use the words in bold to label the diagram of the refrigerator below. (2 marks) B

A

C

G

E

10 (a) Copy the table below and rewrite it to correctly match the substances to their properties and uses. (b) Identify whether the substance would be a solid, liquid or gas.

R

Properties and uses of various substances Name of substance Air

56

Property

Use

Waterproof, hard, strong

Horseshoe

Tin

Particles able to mix easily with other particles

Balloon

Neon

Particles absorb energy and turn it into light

Sign, light

Oil

Hard, strong

Driveways

Iron

Hard, strong, easily shaped when heated

Lubricant

Concrete

Particles slip past each other

Roofing

C

Outside fridge

Inside fridge

Solid, liquid or gas?

C

How a refrigerator works Evaporation occurs when a liquid gains enough heat energy to change into a gas. Refrigeration is possible because of this. The pipes in a refrigerator contain a substance called a refrigerant. (A refrigerant is a substance that changes from a liquid to a gas and back again.) Near the expansion device, the refrigerant is in the liquid state. As it passes through the expansion device, the liquid is made to expand (the pressure drops). As a result of the drop in pressure, the refrigerant cools down to a very low temperature. (You may have experienced this cooling effect if you have ever used a fire extinguisher.) The liquid refrigerant then passes through the part of the pipe that is inside the fridge. This part of the pipe is called the evaporator. Heat energy travels from the objects and air inside the fridge to the very cold refrigerant. The inside of the fridge cools down. The liquid refrigerant heats up and turns to gas (evaporates). (Note: Heat energy travels from a hotter to a colder substance.) The refrigerant, which is now a gas, passes into the compressor. This puts the refrigerant under pressure again. Under pressure, the refrigerant becomes even hotter. (You may have experienced this when you pumped up the tyres on your bike. Under increased pressure, the air in the tyres feels warmer.) The compressor pushes the refrigerant into the next part of the pipe, the condenser. The condenser is on the outside of the fridge. Here, heat from the gas is transferred to the air outside the fridge. The air outside the fridge warms up. The refrigerant in the pipe cools down and becomes a liquid again (condenses). The liquid flows back towards the expansion device. The cycle is repeated. (b) Use the information in the box above to construct a flow chart that describes the changes of state that take place during the refrigeration process. Colour each state a different colour. For example, when the refrigerant is in the liquid state, you may choose to colour the relevant section blue. The flow chart has been started for you. (4 marks) Refrigerant is under pressure and in the liquid state.

Refrigerant passes through expansion device.

L V

L

T

E

D

Core Science | Stage 4 Complete course

work sheets

2.8 States of matter puzzles 2.9 States of matter summary

2 States of matter

STUDY CHECKLIST States of matter

ICT eBook plus

N identify the three most common states of matter 2.1 N describe the physical properties of solids, liquids and gases 2.1 N explain what is meant by the term fluid 2.1 N explain density in terms of the particle model 2.5 N describe the changes in pressure of gases in terms of the increase or decrease of frequency of particle collisions 2.7

Study checklist gives students a detailed outline of the key content covered in the chapter.

Test yourself multiple choice and extended response questions are included at the end of each chapter.

SUMMARY

Under pressure

ICT provides a summary of each chapter’s eBookPLUS eLessons, interactivities and weblinks.

The particle model of matter

2.3

N use the particle model to explain expansion and

contraction of materials during heating and cooling 2.6 N discuss how increasing and decreasing the energy of particles affects their movement 2.3, 2.4 N describe what happens during the process of diffusion 2.3

Changes of state N describe the physical changes that occur during

observations of evaporation, condensation, boiling, melting and freezing 2.2

N relate changes of state to the motion of particles as energy is added or removed 2.4 N explain the changing behaviour of particles during changes of state 2.4

Current issues, research and development in science

Puzzle and summary worksheets can be found in the student workbook and as Word files in eGuidePLUS.

In this video lesson, you will see animations that reflect the behaviour of gas particles and learn about the factors that affect the pressure of a gas. You will also learn how compressed gases are used to make fire extinguishers and aerosol cans. A worksheet is attached to further your understanding.

N state the main assumptions of the particle model 2.3 N describe the difference in behaviour of particles in solids, liquids and gases.

57

Searchlight ID: eles-0058

Interactivities Changes of state This interactivity allows you to simulate heating an ice cube over a Bunsen burner. As you add more heat, you will see the effect on the particles as the ice changes state to become boiling water. A worksheet is attached to further your understanding.

N describe the state of matter called plasma 2.8 N describe current research on the use of plasma in energy production

2.8

Searchlight ID: int-0222 Density This interactivity helps you to delve into the world of density. Select a liquid to fill your virtual flotation tank, and then choose a solid to release into it. This interactivity will let you discover the combinations that cause your solid to sink and to float. A worksheet is attached to further your understanding. Searchlight ID: int-0221

58

Core Science | Stage 4 Complete course

About this book ix

Core Science and the Science Stage 4 syllabus A full grid showing Core Science Stage 4 links to all essential content points is available on the Core Science Stage 4 eGuidePLUS.

Core Science Stage 4 references for Prescribed Focus Areas outcomes Outcomes 4.1 identifies historical examples of how scientific knowledge has changed people’s understanding of the world 4.2 uses examples to illustrate how models, theories and laws contribute to an understanding of phenomena 4.3 identifies areas of everyday life that have been affected by scientific developments 4.4 identifies choices made by people with regard to scientific developments 4.5 describes areas of current scientific research

Essential content: Students learn about: 4/5.1 the history of science

Student text units

Student worksheets

1.6, 2.8, 4.10, 5.2, 5.9, 8.7, 8.8, 10.1, 11.1, 11.8, 13.4, 17.5, 18.2

8.5, 8.7

4/5.2 the nature and practice of science

1.5, 1.6, 5.2, 6.4, 8.1, 8.3, 8.4, 8.5, 9.2, 9.3, 10.1, 10.4, 11.8, 15.6, 17.5 + investigations 4/5.3 the applications and uses 2.8, 3.4, 3.6, 3.7, 5.2, 5.9, 6.6, of science 9.4. 10.8, 11.1, 12.7, 16.4, 17.5, 17.8, 18.3, 18.6 4/5.4 the implications of 5.9, Ch 10 opening science for society and the environment 4/5.5 current issues, research 1.1, 1.6, 2.8, 4.7, 5.9, 7.6, 10.8, and developments in science 14.4, 15.6, 15.9, 17.8, 18.3, 19.7

eBookPLUS

eles-0032, eles-0068

eles-0053, eles-0059, eles-0068, eles-0070, eles-0071, int-0054, int-0226 eles-0053, eles-0065, eles-0068 eles-0053, eles-0057, eles-0068, eles-0069, eles-0070, int-0217

Core Science Stage 4 references for Knowledge and Understanding outcomes Outcomes 4.6 identifies and describes energy changes and the action of forces in common situations

4.7 describes observed properties of substances and theories using scientific models

Essential content: Students learn about: 4.6.1 the law of conservation of energy 4.6.2 forces 4.6.3 electrical energy 4.6.4 sound energy 4.6.5 light energy 4.6.6 heat energy 4.6.7 frictional force 4.6.8 electrostatic force 4.6.9 magnetic force 4.6.10 gravitational force 4.7.1 the particle model of matter 4.7.2 properties of solids, liquids and gases 4.7.3 change of state 4.7.4 elements 4.7.5 mixtures

4.7.6 compounds and reactions 4.8 describes features of living things 4.8.1 cell theory 4.8.2 classification 4.8.3 unicellular organisms 4.8.4 multicellular organisms 4.8.5 humans 4.9 describes the dynamic structure of Earth and its relationship to other parts of our solar system and the universe

x

Syllabus grid

4.9.1 the Newtonian model of the solar system 4.9.2 components of the universe 4.9.3 the structure of Earth

Student text units

Student worksheets

eBookPLUS

9.1, 9.2, 9.3

9.1

6.1–6.5 16.2, 16.3 9.3 9.3 9.2 6.2 16.1 6.1, 6.3 6.4, 8.3, 8.6, 18.1 2.3, 2.4, 2.6, 3.1

6.1

eles-0032, eles-0063, int-0226, int-0226

6.3

2.3

eles-0032, int-0054 eles-0067 int-0225, int-0226 eles-0058

2.1, 2.2, 2.3, 2.5, 2.7, 3.1, 3.2, 12.1 2.4, 2.7

eles-0058, eles-0062

2.4 11.2, 11.3 3.1–3.7, 11.4

eles-0062 int-0229 eles-0059, eles-0060, eles-0061, int-0223, int-0224 int-0224, int-0228, int-0230 eles-0054, eles-0056, eles-0070, int-0206 int-0204, int-0206 eles-0055 eles-0055, eles-0056, eles-0069, int-0211, eles-0056, int-0214, int-0216 int-0006, int-0207, int-0225, int-0232 int-0207, int-0232

3.1

11.4, 11.5, 12.1 5.3, 5.4, 5.5, 10.2 4.2, 4.4, 4.8, 4.9, 13.8, 14.1–14.9 4.9, 5.5, 15.5, 17.1, 17.2, 17.3 5.6, 5.8, 10.1, 10.2, 13.1, 13.2, 13.3, 14.1–14.9 10.1, 10.2, 10.3, 10.6, 10.7, 14.5–14.9 8.1–8.5, 8.7, 8.9

4.1, 4.2, 4.6, 4.7 5.5, 13.1 10.3, 10.6, 10.7 8.3, 8.4, 8.5, 8.7

18.1, 18.2 7.1, 19.1

7.1

Outcomes 4.9 (continued)

4.10 identifies factors affecting survival of organisms in an ecosystem 4.11 identifies where resources are found, and describes ways in which they are used by humans 4.12 identifies, using examples, common simple devices and explains why they are used

Essential content: Students learn about:

Student text units

4.9.4 atmosphere 4.9.5 the hydrosphere 4.9.6 lithosphere 4.10 ecosystems

7.3, 15.6 7.2, 8.6 19.1–19.5 15.4, 15.7, 15.8

eles-0057, eles-0071 eles-0062, int-0225 int-0233, int-0234 int-0211

4.11 natural resources

12.7, Ch 11 opening, 11.6, 11.7, Ch 13 opening, 15.9, 19.3

eles-0057

4.12 technology

6.2, 6.3, 9.1, 9.2, 9.3, 9.4, 10.8, 16.2, 16.3, 18.2

Student worksheets

eBookPLUS

Core Science Stage 4 references for Skills outcomes

Students’ coverage of Skills outcomes are supported throughout the text through Investigations and Activities in every chapter. In this table, text references refer to units where essential content relating to skills is specifically introduced or discussed. Outcomes 4.13 clarifies the purpose of an investigation and, with guidance, produces a plan to investigate a problem

4.14 4.15 4.16 4.17

Essential content: Students learn about: 4/5.13.1 identifying data sources

4/5.13.2 planning first-hand investigations 4/5.13.3 choosing equipment or resources follows a sequence of instructions 4/5.14 performing first-hand to undertake a first-hand investigations investigation uses given criteria to gather first- 4/5.15 gathering first-hand hand data information accesses information from 4/5.16 gathering information identified secondary sources from secondary sources evaluates the relevance of data 4/5.17 processing information and information

4.18 with guidance, presents information to an audience to achieve a particular purpose 4.19 draws conclusions based on information available

4.20 uses an identified strategy to solve problems 4.21 uses creativity and imagination to suggest plausible solutions to familiar problems 4.22 undertakes a variety of individual and team tasks with guidance

Student text units

Student worksheets

1.2, 1.3, 1.5, 13.7, 20.1, 20.4, 20.5, 20.6, 20.7, 20.8 + investigations and activities

20.1

1.5, 13.7, 20.3, 20.5 + investigations and activities 1.2, 5.1, 20.5 + investigations 1.2, 1.3, 5.1, 13.7, 20.5, 20.6

1.6, 1.7, 4.3, 5.3, 6.4, 9.5, 9.6, 15.4, 16.7, 20.1 1.1, 1.2, 3.3, 3.4, 11.5

1.3, 20.5 + investigations 20.4, 20.6 + activities 1.4, 1.5, 5.9, 7.6, 9.4, 10.4, 10.5, Ch 14 opening, 15.8, 15.9, 17.7, 19.7, 20.2, 20.4, 20.5, 20.6, 20.7, 20.8 + investigations and activities

1.2, 3.5, 16.3, 20.2

eBookPLUS

eles-0060, eles-0061, int-0200, int-0101

int-0201 activities in all worksheets

all eBookPLUS eLessons, interactivities, and weblinks

1.1, 1.5, 2.1, 2.2, 2.4, 2.5, 2.6, 3.2, 3.3, 3.4, 4.1, 4.2, 4.3, 4.6, 4.7, 5.1, 5.2, 5.4, 6.1, 6.7, 7.1, 7.4, 7.5, 7.7, 8.1, 8.2, 8.4, 8.6, 8.7, 9.1, 9.2, 9.3, 9.4, 10.1, 10.4, 10.6, 10.7, 11.1, 11.2, 11.3, 12.1, 12.2, 12.5, 12.6, 12.7, 13.5, 13.7, 14.1, 14.2, 14.3, 14.4, 14.6, 15.1, 15.2, 15.3, 15.5, 16.1, 16.2, 16.4, 16.5, 17.1, 18.1, 17.2, 17.4, 18.5, 19.1, 19.2, 19.5 4/5.18 presenting information 1.4, 20.2, 20.3, 20.6, 20.7, 20.8, 1.4, 1.6, 2.1, 6.2, 7.1, 7.3, 9.5, 10.4, int-0101, int-0214 20.9, Text types appendix 13.4, 15.4, 15.7, 16.6, 17.5, 18.3, + investigations and activities 19.4, 20.3 4/5.19 thinking critically 1.5, 2.3, 2.4, 6.1–6.5, 7.1, 8.7, 1.3, 1.6, 2.1, 2.4, 2.5, 3.1, 3.4, 3.5, int-0006, int-0225 9.1–9.3, 11.1, 11.8, 14.1, 4.1, 6.2, 9.2, 9.3, 9.4, 9.6, 10.5, 12.2, 16.1–16.3, 20.5, 20.9 12.3, 12.4, 13.3, 13.4, 15.7, 16.3, 17.5, + investigations and activities 18.3, 20.3 4/5.20 problem-solving 1.5, 20.1, 20.2 int-0223 + investigations and activities 4/5.21 the use of creativity and 1.5, 20.2, 20.5 int-0223 imagination + investigations and activities 4/5.22.1 working individually 4/5.22.2 working in teams

20.1–20.9 + investigations and activities all investigations and activities done in teams

Syllabus grid xi

About JacarandaPLUS Ab Useful verbs S Verbs used in Activities and Looking back questions In many cases, questions in Activities and Looking back use the following verbs, which come from the New Higher School Certificate Assessment Support Document: ‘A Glossary of Key Words’. Students will find that becoming familiar with these verbs is useful, since they are designed to help them understand the type of response that is expected in exam papers and assessment tasks.

xii

Account for

State reasons for; report on

Assess

Make a judgement of value, quality, outcomes, results or size

Calculate

Ascertain/determine from given facts, figures or information

Classify

Arrange or include in classes/categories

Compare

Show how things are similar or different

Construct

Make; build; put together items or arguments

Contrast

Show how things are different or opposite

Deduce

Draw conclusions

Define

State meaning and identify essential qualities

Demonstrate

Show by example

Describe

Provide characteristics and features

Discuss

Identify issues and provide points for and/or against

Distinguish

Recognise or note/indicate as being distinct or different from; to note differences between

Evaluate

Make a judgement based on criteria; determine the value of

Explain

Relate cause and effect; make the relationships between things evident; provide why and/or how

Extrapolate

Infer from what is known

Identify

Recognise and name

Interpret

Draw meaning from

Investigate

Plan, inquire into and draw conclusions about

Justify

Support an argument or conclusion

Outline

Sketch in general terms; indicate the main features of

Predict

Suggest what may happen based on available information

Propose

Put forward (for example a point of view, idea, argument, suggestion) for consideration or action

Recall

Present remembered ideas, facts or experiences

Summarise

Express, concisely, the relevant details

Useful verbs

Acknowledgements The publisher would like to thank the following copyright holders, organisations and individuals for their assistance and for permission to reproduce copyright material in this book. Images: • AAP Image: /AFP 83; /AFP/Australian Antarctic Division/Hosung Chung 181; /AFP/HO/NASA/Getty OUT 187; /AFP/Kazuhiro Nogi 312 (bottom); /AFP/Torsten Blackwood 227; /AFP/William West 424; /AP/ Jacques Boissinot 416 (right); /Dean Lewins 284; /Eugene Hoshiko 243; /Paul Miller 435; /Richard Durham 337; /Wildlight/David Moore 248 (bottom); /Wildlight/John Frederick White 110 (right); /Wildlight/ Richard Woldendorp 300 • ANTPhoto.com.au: /Bill Bachman 188, 223, 412; /Colin Blobel 427; /Cyril Webster 397 (centre); /Dave Watts 110 (left), 98 (echidna); /Denis and Theresa O’Byrne 496 (top); /Fredy Mercay 419; /Jurgen Otto 390 (top left); /Karen Cianelli 396 (right); / Ken Griffiths 235 (top); /Otto Rogge 353 (right), 495 (right); /Pavel German 485; /Peter McDonald 100 (centre); /R & D Keller 353 (left) • Ardea London 326 • Asics Oceania Pty Ltd 167 (right) • Austral International 328 (2 images) • Australian Academy of Science 416 (left) • Australian Antarctic Division photo by Mandy Holmes © Commonwealth of Australia/2183D6: Handling an ice core at Law Dome, near Casey station 406 • Australian Bureau of Meteorology 178 (8 images); /Australian Radiation Protection and Nuclear Safety Agency, Cancer Council and SunSmart copyright Commonwealth of Australia, reproduced by permission. www.cancer.org.au/Home.htm and Sun Smart, www.cancer.org.au/cancersmartlifestyle/SunSmart.htm 204 • Biopure Corporation 283 • Brand X Pictures 266 (ant), 357 (centre left) • Coo-ee Picture Library 15 (top), 66, 69, 75, 80, 100 (right), 492 (bottom) • Cooperative Research Centre for Cochlear Implant and Hearing Aid Innovation, The Bionic Ear Institute, Australia 253 • Corbis: 174; /Andy Hibbert 503 (left); /Bettmann 4 (top right), 29 (left), 30 (right), 31, 119 (bottom right), 221 (left), 470 (centre left), 480 (right); /Bob Krist 496 (bottom); /Car Culture 440; / Chris Hellier 108 (right); /epa/Evertt Kennedy Brown 87; /Francesca Muntada 357 (top right); /Galen Rowell 16; /Gallo Images/Nigel J Dennis 250; /Joe McDonald 123 (right); /Michael & Patricia Fogden 390 (top right); /Museum of the City of New York 29 (right); /NASA/ STScI 471; /Noeline Kelly 318; /Ric Ergenbright 490 (top right); / Richard T Nowitz 105 (cockroach); /Roger Ressmeyer – Starlight 479 (left); /Roger Ressmeyer 4 (top left, bottom right), 225 (right), 486 (bottom right), 490 (centre); /Ron Watts 330 (bottom right); /Science Picture Libraries/David Spears 105 (nematode); /Sergio Dorantes 246 (bottom); /Sygma/Ira Wyman 282; /Visuals Unlimited 145 • Corbis Royalty Free 232 (bottom left), 270, 303 (diamond), 431, 436 • David Malin Images 206; /© Akira Fujii 470 (top right); /© Anglo-Australian Observatory 480 (left) • Digital Stock: /Corbis Corporation 43, 50 (left), 52 (right), 104 (butterfly), 330 (centre left), 354 (second top), 367 (peanut), 486 (bottom left), 497 (top right), 498, 505 (bottom); / Marty Snyderman 104 (sponge) • Digital Vision: 55, 70, 108 (left), 224, 324, 354 (top), 362, 414 (top), 418 (grasshopper), 447 (mosquito) • Emerald City Images: /Minden Digital/Flip Nicklin 14 (top) • Fairfax Photo Library: 321; /Helen Nezdropa 165 (left); /Joe Armao 138 • Colleen Foelz 93 (cat), 354 (second bottom) • Future Farm Industries CRC/www.futurefarmcrc.com.au 189 (2 images) • Getty Images: /National Geographic/Luis Marden 27; /Rischgitz 30 (left); /Taxi Japan/Masaaki Toyoura 37 (right); /Redferns/Fin Costello 41; /Stone/Davies and Starr 53; /Stone/David Burder 105 (tapeworm); /Dr George Chapman 123 (bottom left); /Peter Ginter 144 (bottom); / Allsport/Robert Cianflone 147 (2 images); /Allsport/Jeff Gross 150; / The Image Bank/John Kelly 167 (left); /Stringer/Otto Greule Jr 168; / Photonica/Kim Steele 244 (firefly); /Taxi/Peter David 244 (fish); / Aurora 245; /Hulton Archive 261; /Botanica/Ann Cutting 357 (bottom right); /Botanica 357 (centre right); /Asia Images/Yukmin 429; /Visuals

Unlimited/SIU 447 (hand); /Stone/Charles Gupton 449 (right); /J A Hampton 455 (right); 520 (centre right); /Royalty-Free 520 (dog sitting) • Goodshoot 486 (top right); • Carol Grabham 166 (bottom) • Image Addict (© imageaddict.com.au): 71 (centre left and top); 108 (centre); 158; • Image Disk Photography: 402 (top right); 418 (kookaburra); 503 (bottom right) • Image Source: 447 (meat) • JCSMR, ANU: /The John Curtin School of Medical Research, ANU 455 (left, 3 images) • JF Heron 274 (left) • John Wiley & Sons Australia: /AbsolutVision 541; /Renee Bryon 59, 61 (bottom left), 61 (top left), 78, 234 (bottom), 246 (top), 434; /Photo by Coo-ee Picture Library 295 (top), 297; /Werner Langer 314, 325 (6 images), 437 (4 images), 495 (left), 497 (left); /Janusz Molinksi 302 (3 images); / Daniela Nardelli 319 (top right) 463 (left), 463 (right); /Julie Stanton 535 (left); /Kari-Ann Tapp 64, 520 (bottom right), 524 (top) • John Wiley & Sons, Inc: /Corbis Digital Stock 98 (crocodile) • Lochman Transparencies: /Lochman Transparencies/Brett Dennis 409; / Lochman Transparencies/Mike Braham 411 • Microsoft Corporation: / Screen shot reprinted by permission from Microsoft Corporation 200, 201 (4 images), 202 (5 images), 518, 533 (left, right), 534 (bottom), 534 (centre left, right, top left), 536 (3 images), 537 (8 images) • NASA: 199 (left), 222 (left), 222 (right), 479 (centre); /NASA/JPL/ University of Colorado 193; /NASA/JPL-Caltech 466; /NASA/Thomas M Brown, Charles W Bowers, Randy A Kimble, V Allen 469 (bottom right), 474 (middle left), 483 (bottom left); /HEASARC/ASD/NASA/ GSFC; /NASA © Yuri Beletsky 476; /Courtesy of SOHO consortium. SOHO is a project of international cooperation between ESA and NASA 479 (right); /NASA/A.Caulet St-ECF, ESA 481 (left); /NASA/JSC 481 (top right), 482 (top) • National Sport Information: /Ausport Image Library 33 (bottom) • Natural Resources & Water: © The State of Queensland (Department of Natural Resources & Mines) 2003. Based on or contains data provided by the State of Queensland (Department of Natural Resources and Water) 2009. In consideration of the State permitting use of this data you acknowledge and agree that the State gives no warranty in relation to the data (including accuracy, reliability, completeness, currency or suitability) and accepts no liability (including without limitation, liability in negligence) for any loss, damage or costs (including consequential damage) relating to any use of the data. Data must not be used for direct marketing or be used in breach of the privacy laws. 504 • New Brunswick Government: /Government of New Brunswick 212 (2 images) • Newspix: 139; / Newspix/Peter Bennett 2; /Newspix/Colleen Petch 5 (bottom), 6; / Newspix/Ian Cugley 14 (bottom); /Newspix/Craig Greenhill 70–1; / Newspix/Sarah Rhodes 86 (bottom right); /Newspix/Cameron Tandy 105 (squid); /© Newspix/Michael Dodge 153; /Newspix/AFP 190; / Newspix/AFP Photo/Torsten Blackwood 215 (bottom 3 images); / Newspix/Brett Hartwig 311; /© Newspix /Colin Murty 393; /Newspix/ Matthew Newton 416 (top centre); /Newspix/Ian Munro 462 (bottom) • Ray Norris 217 (2 images), 218 (left) • Olive Images 86 (top right) • out of copyright: 221 (right 2 images); /USA Government National Cencer Institute 274 (right); /From Alice’s Adventures in Wonderland by Lewis Carroll. Illustration by John Tenniel. Macmillan & Co Ltd, 1938 (first edition 1865) 294 • Pearson Education US: /Fig. 42.6, p. 876 from Biology, 6th ed. by Neil A Campbell and Jane B Reece. Copyright © 2002 by Pearson Education, Inc. Used by permission 279 • Photodisc 1, 4 (bottom left), 5 (centre), 5 (top), 6 (ball), 18, 33 (top), 36, 54, 61 (right), 71 (centre right), 85 (left, right), 86 (bottom left), 89 (duck, horse, pig, rabbits, rooster, sheep), 93 (tomatoes), 95 (2 images), 98 (parrot), 104 (jellyfish, snail, starfish), 104–5 (earthworms), 109 (bacteria), 131, 136, 144 (centre), 144 (top), 155, 162, 170, 172, 197 (left, right), 198 (bottom, top), 199 (bottom right, top right), 207, 209, 225 (left), 234 (top), 244 (moon, statue), 248 (top), 252, 254, 260, 266 (jellyfish, worms), 279 (bottom, top), 303 (pencil), 316, 323 (left, right), 330 (bottom left, centre right, top), 331, 347 (centre), 354 (bottom), 355 (bottom),

Acknowledgements xiii

364 (bread, pasta, potato, rice), 367 (apples, bread, cereal, cheese, chocolate, eggs, hamburger, ice-cream, milk, strawberries, yoghurt), 369 (left), 390 (bottom right), 396 (centre), 397 (right), 402 (bottom right, centre left), 418 (grass, heron, mouse, rabbits, snake), 447 (bacteria, boy, nurse), 452 (bottom), 475, 478, 481 (bottom right), 482 (bottom, 3 images), 486 (top left), 487 (centre right), 491 (bottom, top), 492 (centre, top), 497 (bottom), 499 (right), 500, 503 (top), 505 (top right), 508, 513, 520 (clock, lamp, top right), 525, 526, 535 (right) • Photolibrary: 49 (bottom), 52 (left), 93 (liger), 360; /Photolibrary/Foodpix/Eric Futran 60; /Photolibrary/SPL/ Celltech/James Holmes 74; /Photolibrary/Lightscapes Inc 86 (top left); /Photolibrary/SPL/Laguna Design 95; /Photolibrary/SPL/Astrid & Hanns-Frieder Michler 109 (amoeba); /Photolibrary/SPL/Alfred Pasieka 109 (spiral bacterium); /Photolibrary/SPL/Dr Brian Brain 114; /Photolibrary/SPL/SNI 115 (bottom); /Photolibrary/SPL/Andrew Syred 115 (top), 140 (right), 335, 396 (left); /Photolibrary/SPL/Steve Gschmeissner 116 (centre), 140 (bottom left); /Photolibrary/Mary Evans Picture Library 119 (bottom left); /Photolibrary/SPL/Adam Hart-Davis 119 (top); /Photolibrary/SPL/John Durham 123 (top left); /Photolibrary/SPL/Dr Gopal Murti 126; /Photolibrary/SPL/Astrid & Hanns-Frieder Michler 127; /Photolibrary/SPL/A.B. Dowsett 128; / Photolibrary/SPL/Dr Jeremy Burgess 140 (top left), 219, 336, 448, 451 (right); /Photolibrary/Dennis Hallinan 143; /Photolibrary/age fotostock/Xavier Subias 148; /Photolibrary/Photo Researchers, Inc./ Hermann Eisenbeiss 166 (top); /Photolibrary/Foodpix 176; / Photolibrary/SPL/Dr Fred Espenak 215 (top); /Photolibrary/The Bridgeman Art Library/Portrait by Pomeranie/Musee de Torun, Poland 220 (left); /Photolibrary/SPL 220 (right), 272, 291, 306 (left), 306 (right), 307 (right), 447 (ringworm), 471 (bottom right); / Photolibrary/Claver Carroll 228 (bottom); /Photolibrary/Frank Chmura 228 (top); /Photolibrary/SPL/Andrew Lambert Photography 230; /Photolibrary/SPL/Lawrence Lawry 232 (bottom right); / Photolibrary/Index Stock Imagery 232 (top); /Photolibrary/Sheila Terry 237; /Photolibrary/SPL/Dr Arthur Tucker 241; /Photolibrary/ SPL/National Cancer Institute 260; /Photolibrary/OSF/Tobias Bernard 263 (left); /Photolibrary/Andrew J Martinez 263 (right); / Photolibrary/SPL/Prof. M Brauner 268 (left, right); /Photolibrary/ SPL/Damien Lovegrove 271; /Photolibrary/SPL/Klaus Guldbrandsen 275; /Photolibrary/SPL/Eric Grave 276; /Photolibrary/SPL/Bo Veisland 278; /Photolibrary/SPL/Laguna Design 288; /Photolibrary/ SPL/Astrid & Hanns-Frieder Michler 295 (bottom); /Photolibrary/ SPL/Kaj R Svensson 303 (coal); /Photolibrary/SPL/Professor Peter Fowler 307 (left); /Photolibrary/SPL/Geroge Steinmetz 312 (top); / Photolibrary/SPL/Cordelia Molloy 319 (bottom), 364 (fish); / Photolibrary/Richard T Nowitz 319 (top left); /Photolibrary/SPL/Dr Keith Wheeler 339; /Photolibrary/Ed Reschke 340; /Photolibrary/SPL/ Helmut Partsch 347 (bottom); /Photolibrary/Japack Photo Library 347 (top); /Photolibrary/Michele Lamontagne 355 (centre); / Photolibrary/Harley Seaway 355 (top); /Photolibrary/Botanica/Mark Turner 357 (bottom left); /Photolibrary/Bildhuset Ab/Bengt Olof Olsson 357 (top centre); /Photolibrary/Peter Arnold Images Inc/ Reschke Ed 357 (top left); /Photolibrary/Fresh Food Images 359; / Photolibrary/SPL/Bodenham LTH NSH Trust 369 (right); / Photolibrary/SPL/P M Motta 372; /Photolibrary/Cromorange 378; / Photolibrary/SPL/Dr Keith Wheeler 387, 390 (bottom left); / Photolibrary/SPL/Peter Scoones 396 (left); /Photolibrary/SPL/ Francoise Sauze 402 (bottom centre); /Photolibrary/SPL/David Scharf 402 (bottom left); /Photolibrary/SPL/Garry Watson 402 (top left); / Photolibrary/Luis Alonso Ocana 416 (bottom centre); /Photolibrary/ SPL/Adam Hart-Davis 421; /Photolibrary/Peter Harrison 423; / Photolibrary/SPL/Southampton General Hospital 445; /Photolibrary/ Phillip Hayson 447 (car); /Photolibrary/SPL/Eye of Science 447 (fluke); /Photolibrary/SPL/Dr MA Ansary 447 (goitre); /Photolibrary

xiv

Acknowledgements

SPL/Eric Grave 447 (louse); /Photolibrary/SPL/Alfred Pasieka 447 (osteoporosis); /Photolibrary/SPL/A.B. Dowsett 449 (left); / Photolibrary/SPL/John Radcliffe Hospital 451 (left); /Photolibrary/ SPL/Gusto Gusto 452 (top); /Photolibrary/SPL/Scott Cazamine 453 (left); /Photolibrary/SPL/CNRI 453 (right); /Photolibrary/SPL/Russell Kightley 454; /Photolibrary/SPL/James Stevenson 459 (bottom); / Photolibrary/SPL/Dr P Marazzi 459 (centre); /Photolibrary/Dr P Marazzi 459 (top); /Photolibrary/SPL/Gusto Productions 462 (top); /Photolibrary/SPL/Chris Butler 468; /Photolibrary/SPL/European Southern Observatory 469 (left); /Photolibrary/SPL/European Southern Observatory 483 (top right); /Photolibrary/SPL/Telescope Science Institute/NASA Space 469 (top); /Photolibrary/SPL/NASA/ CFA/CXC/M Markevitch 470 (bottom left); /Photolibrary/SPL/NASA/ ESA/STSCI 470 (top left); /Photolibrary/SPL/John Sanford 472; / Photolibrary/SPL/Fes 474; /Photolibrary/SPL/Dr Rudolph Schild 483 (bottom right); /Photolibrary/SPL/Telescope Science Institute/NASA Space 483 (top left); /Photolibrary/John Fairfax Publications Pty Ltd/ Erin Jonasson 486 (centre left); /Photolibrary/Oxford Scientific Films/ Martyn Chillmaid 490 (bottom centre); /Photolibrary/SPL/Vaughan Fleming 501 • PureStock 165 (right) • Quill Graphics 456 (4 images) • QUT Marketing &Communications: /Queensland University of Technology/Anne Musser 101 • Rubberball Productions 289 • South American Pictures: /South American Pictures/National Museum of Anthropology 218 (right) • Shutterstock.com: /© GeoM, 2009 Used under license from Shutterstock.com 257; /© Sandra Cunningham, 2009 Used under license from Shutterstock.com 358; © Jack Cronkhite, 2009 Used under license from Shutterstock.com 444 • Julie Stanton 235 (bottom), 333, 494, 521 (bottom); /John Wiley & Sons/Julie Stanton 49 (top) • Stockbyte 367 (beef, broccoli, zucchini), 428 • Sydney Water: /Courtesy of Sydney Water Corporation 76 • Taronga Zoo: /Courtesy: Taronga Zoo 540 • Thinkstock 98 (shark) • Brett Thomas 354 (centre), 499 (top), 505 (top), 524 (bottom) • Jackie Tracy 37 (left) • Lyn Treadwell: /Lyn Trounson 487, 490 (bottom right, left, top centre), 499 (left), 505 (top left) • Peter Trusler 103 • University of Florida — IFAS: /Thomas Wright University of Florida/IFAS 403 • Vernier Software & Technology 24 • Viewfinder Australia Photo Library 98 (frog), 100 (left) • Visy Recycling 62 3 • Pascale Warnant: 15 (bottom), 509, 510, 511, 522, 526, 539; /Pascale Warnant. Photograph in banner © Julie Stanton 521 (top)

Text: • Eileen Kennedy, Peter Rozanski, Daniela Nardelli, Peter Saffin, Paula Taylor, Ross Phillips, Collette Ballantyne, Marion van Gameron, Tim Byrne, Patricia Christies • Australian Institute of Health 446 • Cancer Institute NSW: /© Cancer Institute NSW. Source: Incidence and mortality data, NSW Central Cancer Registry. Population estimates HOIST, Epidemiology and Surveillance Branch, NSW Health Department 461 • Dept of Ed. & Training WA: /From ‘Helping students to do open investigations in science by Mark Hackling and Robert Fairbrother, Australian Science Teachers Journal, December 1996 Vol. 42 No. 4 © Department of Education & Training WA 25 • NSW Board of Studies: /Outcomes statements from Science 7 10 Syllabus © Board of Studies New South Wales for and on behalf of the Crown in right of the State of New South Wales, 2003. The most up-to-date version of this document can be found at www.boardofstudies.nsw. edu.au/syllabus_sc/pdf_doc/science_710_syl.pdf x xi • Sports Data Pty Ltd 349 • Taronga Zoo: /Courtesy: Taronga Zoo 540 Every effort has been made to trace the ownership of copyright material. Information that will enable the publisher to rectify any error or omission in subsequent editions will be welcome. In such cases, please contact the Permissions Section of John Wiley & Sons Australia, Ltd.

The important thing in science is not so much to obtain new facts as to discover new ways of thinking about them. Sir William Bragg (1862–1942)

1

Investigating

The word science comes from the Latin word scientia, meaning knowledge. Scientists have been seeking knowledge for many thousands of years. Before the 1600s, early scientists were often called philosophers, because they had limited technology to investigate the world around them; they merely applied their reasoning to make sense of what they saw. Today, scientists use sophisticated equipment to carry out investigations and build on the body of knowledge that is science. But science is more than a collection of important facts. It is about exploring and, as an explorer, you will be trained to investigate scientifically so the conclusions you arrive at are based on sound information.

In this chapter, students will: 1.1 ◗ identify the branches of science and

some careers in science 1.2 ◗ identify appropriate laboratory

equipment for experiments and use it safely 1.3 ◗ record observations and

measurements accurately 1.4 ◗ organise and present data clearly

using tables and graphs and produce a scientific report of investigations 1.5 ◗ design controlled experiments

and identify trends, patterns and contradictions in data collected 1.6 ◗ describe contributions made by

scientists and outline examples showing how scientists make observations, identify trends and patterns and construct hypotheses.

Forensic scientists use their knowledge to help solve crimes.

Careful observations are required before any conclusions can be drawn. Look carefully at the drawing below and describe what you think has happened.

Thinking about investigating

1. Look around the laboratory. Identify five features special to this working environment. 2. Identify five everyday devices that have been invented with the assistance of science. 3. Do you know anyone working in science? Describe what they do. 4. Think of a really important scientific discovery. Discuss with a partner why you think it is so significant. In your workbook, describe the discovery and its significance. 5. These two pieces of equipment are used for measuring volumes of liquids. Identify an important difference between them, other than their Beaker Measuring cylinder 7. If you were asked to draw a picture of a scientist, shape. Outline when what would you draw? Draw your image of a each should be used. scientist on A4 paper. Underneath your drawing, 6. Some of the skills that scientists use are the same as those used by detectives in solving a crime. write a brief description of the scientist. 100ml

50ml

100ml

50ml

0ml

think about the properties of each part of the mixture that will make separation possible.

InveStIgatIon 1.1 Design and separate Your task is to separate the four components of a mixture of dead matches, pebbles, steel paper clips and sand. You will need: sand (about 250 mL) dead matches small pebbles steel paper clips plastic container (about 500 mL) A3 paper other equipment and water as required

◗ Make a list of all of the equipment

◗ Devise and write a step-by-step

plan of a method to separate the four parts. You will need to

Step 1

that you will need. ◗ Gather the equipment and perform

the separation.

Discussion 1

◗ Mix the matches, pebbles and

paper clips evenly in a plastic container of sand.

Matches, pebbles, paperclips, sand

2

Copy and complete the following flow chart in your workbook. Outline each step you followed and, in each of the boxes, list the items separated. Identify the unique property or feature of each item that allowed it to be separated from the other items.

Step 2

Step 3

1.1

What do scientists do? The branches of science You can find scientists just about anywhere. They could be in a desert finding out how plants survive without water. They could be digging deep into the ice in Antarctica. You might find a scientist searching for fossils on a rocky shore, counting rare animals in a rainforest or monitoring electricity in a power station. Some scientists work in laboratories, searching for a cure for a disease. Others work in the chemical industry. You might even find a scientist in space. There are many branches of study in science. A few are shown on these pages. Earth science Earth scientists, or geologists, study the Earth. They investigate and explain how rocks and mountains form. Some specialised geologists, called seismologists, study earthquakes. Palaeontologists study fossils and ancient rocks. Vulcanologists study volcanoes.

Biology Biologists study living things. They investigate how living things function and how they live together. Some biologists, like botanists and horticulturists, study plants. Zoologists and veterinarians study animals. Microbiologists study microscopic living things. People like doctors and dentists use their knowledge of biology to help keep people and their teeth healthy.

4

Core Science | Stage 4 Complete course

eBook plus

eLesson

Career spotlight: scientist Meet marine biologist Jodie Haig and learn about this exciting career in marine science. eles-0053

not all scientists were high achievers at school. some very famous scientists were average or below average school students. Albert Einstein is probably the most famous example. He did not talk until he was three years old. He left school at the age Fig. 1.1.8 of 15 and went back head of later. He passed his university exams by Einstein studying the notes of his classmates.

Astronomy Astronomers study the sky. They are concerned with planets, moons, stars, comets and other objects in space.

A mix of science Physics P Physicists study different ttypes of energy. They investigate and explain tthings like movement, heat, nnuclear energy, light and eelectricity. Some engineers uuse their knowledge of pphysics to make sure bbuildings are strong and ccars are safe. A knowledge of physics is also used iin electronics, computer design and even special effects in movies.

The boundaries between the different sciences are often crossed. Biophysicists and biochemists work in more than one field. Also, scientists from different fields often work together to solve problems. Physicists worked with medical staff to design the bionic ear. Physicists and geologists work together to locate underground mineral deposits using soundwaves. Chemists work with biologists to find cures for diseases.

specialising Within each field of science, scientists specialise in a specific area. For example, in psychology, neuropsychologists work with physiologists to study the different areas of the brain to better understand brain functions like memory and learning. Sports psychologists advise athletes on self-image and on maintaining the motivation to persist and succeed in their chosen sport.

Chemistry Chemists study how substances react with other substances. They investigate and explain why some substances behave differently from others and how they can best be used. Industrial chemists might look for ways to make better paints or special plastics. Pharmacists are chemists too. They work with chemicals that are used to treat illness and disease.

science and technology

Psychology Psychology is the study of human behaviour. Psychologists study the causes of behaviour, including the emotional, social and developmental factors involved. In general, psychology is concerned with how people perceive the world around them and how they react to it, how they grow, how they learn and how they relate to others and function in groups.

Scientific discoveries have helped improve our quality of life. Whenever you turn on a light, fly in a plane, play tennis or flush a toilet, you are using a product of scientific knowledge. The word technology refers to devices that use scientific ideas to make life easier.

Some scientific discoveries happen by accident. Bacteriologist Alexander Fleming discovered the first antibiotic, which he called penicillin. He observed that a tiny piece of mould that had fallen into his experiment stopped the growth of bacteria.

1 Investigating 5

Chemical engineers have been responsible for producing a lightweight but powerful tennis racquet for modern tennis players. Lleyton Hewitt s racquet frame is constructed of graphite, elastomer and Kevlar. The strings are made of nylon. Tennis racquet technology has changed greatly from the timber and catgut tennis racquets of the 1950s and the 1960s.

Sports psychology helps athletes train their minds for greater success in the sports arena. Lleyton has received advice from sports psychologists on setting goals, motivation and concentration.

Industrial chemists look for ways to make better materials. Lleyton s tennis outfit is made of a blend of polyester and cotton. The blend of these two fibres makes the fabric more breathable and durable. The branch of biology that studies the function of the human body is physiology. Lleyton suffered a hip injury leading up to the Olympic Games in 2008. Lleyton travelled with a physiotherapist to Beijing so that he could get through the games and continue on to the US Open. Physicists study how objects move and the importance of forces such as friction. They research the performance of the different types of balls. For example, tennis balls with coarser covers slow down more quickly in their flight through the air. The branch of physics that studies how people move is called biomechanics. Scientists use modern video and computer technology to analyse every part of Lleyton s swing to help suggest improvements. Researchers in physics have helped modern tennis players adjust their game to suit different playing surfaces. On a grass court, tennis players are encouraged to serve as fast as possible to produce a fast, low bounce. On clay courts, a player needs to reduce the speed of the serve and put more spin on the ball. This produces a slower, higher bounce that is difficult to return.

activities

6 How might these people use science in their daily work? (a) Doctor (b) Mechanic (c) Farmer (d) Firefighter (e) Architect

REMEMBER 1 Describe what scientists do.

inVEsTiGATE

2 Define the term technology .

7 Read the main section of a daily newspaper. Count the number of times that a scientist is referred to or quoted. Select any one of these scientists and make notes for each to identify: ◗ the scientist s name ◗ the branch or specific field of science they study ◗ which organisation they work for ◗ what the newspaper article is about and why the scientist has been included in the article.

THinK 3 What type of scientist would investigate rocks to see how old they are? 4 Give an example of the work that a biophysicist and a biochemist might do. 5 Look at the photograph of Australian tennis player, Lleyton Hewitt. Propose how each of the following scientists might improve his performance. (a) Nutritionist (b) Psychologist (c) Physicist

6

Core Science | Stage 4 Complete course

eBook plus

8 Use the Da Vinci s machines weblink in your eBookPLUS to learn about some of the important machines that Leonardo da Vinci invented.

1.2

the science laboratory Getting to know the science lab Scientists conduct experiments in a laboratory. The science laboratory is different from other classrooms in the school. It is filled with a range of equipment to help you undertake scientific investigations safely. • Sit quietly for a minute or two and look around the science laboratory. • List as many differences as you can between the science laboratory and other general classrooms at your school. • Draw a map of the science laboratory, labelling each of the following items present in your laboratory. Student tables and work benches Teacher s desk or demonstration bench Gas taps Sinks Fume cupboard Eye wash and safety shower Fire extinguishers Fire blanket Broken glass bin Rubbish bin Doors

Laboratory equipment Some of the equipment that you are likely to use in science is listed on the right. Use the illustrations on the following page to find each item in the laboratory.

Equipment

Use

Beaker

Container for mixing or heating substances

Bosshead

Holds the clamp to a retort stand

Bunsen burner

Heats substances

Clamp

Holds objects at the required height on a retort stand

Conical flask

Container for mixing substances or collecting filtered substances

Evaporating dish

Container for heating small amounts of substances over a Bunsen burner

Filter funnel

Used with filter paper to filter substances

Gauze mat

Supports a container over a Bunsen burner while it is heated; spreads heat evenly under the container

Heatproof mat

Protects benches from damage

Measuring cylinder

Used to measure volume accurately

Retort stand

Used with clamps and bossheads to hold substances at the required height

Safety glasses

Protects eyes

Spatula

Used to pick up small amounts of solid substances

Stirring rod

Used to stir mixtures

Test tube

Container for holding, heating or mixing small amounts of substances

Test-tube holder

Holds a test tube while it is being heated

Test-tube rack

Holds test tubes upright

Thermometer

Measures temperature

Tongs

Used to pick up and hold small objects while they are heated

Tripod

Supports a gauze mat over a Bunsen burner

Watchglass

Holds small quantities of solids

1 Investigating 7

Some equipment that you are likely to use in the science laboratory Watchglass

Gauze mat Bunsen burner Filter funnel Tripod

Evaporating dish Heatproof mat

Thermometer

Clamp

Safety glasses

Bosshead

Conical flask Retort stand

Test-tube holder

Stirring rod Test tube

Spatula

Measuring cylinder

Test-tube rack Tongs

Beaker

8

Core Science | Stage 4 Complete course

investigating safely

Handy hints

Doing experiments in science can be exciting, but accidents can happen if investigations are not carried out carefully. There are certain rules that must be followed for your own safety and the safety of others.

• Use a filter funnel when pouring from a bottle or container without a lip. • Never put wooden test-tube holders near a flame. • Always turn the tap on before putting a beaker, test tube or measuring cylinder under the stream of water. • Remember that most objects get very hot when exposed to heat or a naked flame. • Do not use tongs to lift or move beakers.

ALWAYs • follow the teacher’s instructions • wear safety glasses and a laboratory coat or apron, and tie back long hair when mixing or heating substances • point test tubes away from your eyes and away from your fellow students • push in chairs and keep walkways clear • inform your teacher if you break equipment, spill chemicals or cut or burn yourself • wait until hot equipment has cooled before putting it away • clean your workspace — don’t leave any equipment on the bench • dispose of waste as instructed by your teacher • wash your hands thoroughly after handling any substances in the laboratory.

nEVER • enter the laboratory without your teacher s permission • run or push in the laboratory • eat or drink in the laboratory • smell or taste chemicals unless your teacher says it s ok. When you do need to smell substances, fan the odour to your nose with your hand • leave an experiment unattended • conduct your own experiments without the teacher’s approval • put solid materials down the sink • pour hazardous chemicals down the sink (check with your teacher) • put hot objects or broken glass in the bin.

Working with dangerous chemicals Your teacher will tell you how to handle the chemicals in each experiment. At times, you may come across warning labels on the substances you are using. Always wear gloves and safety glasses when using chemicals with this symbol. Corrosive substances can cause severe damage to skin and eyes. Acid CORROSIVE is an example of a corrosive 8 substance. These substances are easily set on fire so keep them away from flames. FLAMMABLE Methylated spirits GAS is flammable. 2 Chemicals with this label can cause death or serious injury if swallowed or breathed in. They are also dangerous when touched without gloves because they can be absorbed by the skin. Mercury is a toxic substance.

1 Investigating 9

Heating substances Many experiments that you will conduct in the laboratory require heating. In school laboratories, heating is usually done with a Bunsen burner. A Bunsen burner provides heat when a mixture of air and gas is lit. Bunsen burners heat objects or liquids with a naked flame. Always tie hair back, and wear safety glasses and a laboratory coat or apron when using a Bunsen burner.

Use a gauze mat over a tripod to hold containers over a Bunsen burner flame. Beaker

Gauze mat

Bunsen burner Tripod

Heating containers Beakers and evaporating dishes can be placed straight onto a gauze mat for heating. Never look directly into a container while it is being heated. Wait until the equipment has cooled properly before handling it.

Heatproof mat Evaporating dish

A guide to using the Bunsen burner 1 Place the Bunsen burner on a heatproof mat.

Barrel

6 Turn on the gas tap and a yellow flame will appear.

2 Check that the gas tap is in the off position.

Gas hose Collar

3 Connect the rubber hose to the gas tap. 4 Close the air hole of the Bunsen burner collar.

Air hole (gas jet inside)

8 Remember to close the collar to return the flame to yellow when the Bunsen burner is not in use.

Base

5 Light a match and hold it a few centimetres above the barrel.

◗ Close the air hole.

InveStIgatIon 1.2

◗ Hold the porcelain in the yellow flame for a few minutes.

Which flame is hotter? You will need: Bunsen burner matches pieces of porcelain clock or watch

heatproof mat tongs safety glasses

Discussion 1

Describe the flame when the air hole is open. What colour is it? Does it make a noise?

2

Describe the flame when the air hole is closed. Is it easy to see?

3

Does the porcelain turn red-hot in the yellow flame when the air hole is closed?

4

Do you notice anything else about the porcelain after heating in the yellow flame?

5

Which is the hotter flame? What observations did you make that support your answer?

◗ Light the Bunsen burner according to the guide above. ◗ Open the air hole. ◗ Hold a piece of porcelain over the flame with the air hole

open. ◗ Record roughly how long it takes for the porcelain to turn

red-hot. ◗ Let the porcelain cool on the heatproof mat.

10

Core Science | Stage 4 Complete course

7 Adjust the flame by moving the collar until the air hole is open and a blue flame appears. (A blue flame is hotter than a yellow flame.)

InveStIgatIon 1.3 Where is the hottest part of the flame? You will need: Bunsen burner heatproof mat matches safety glasses

nichrome wire tongs pin

Part A ◗ Use a pin to hang an unburnt match over the barrel

of a Bunsen burner. ◗ Light the Bunsen

burner according to the guide on the opposite page. ◗ Turn the collar to

produce a blue flame.

Discussion 1

What happens to the match hanging over the barrel? Explain why.

2

What colour does the wire become when held across the flame?

3

Is the colour of the wire different when it is held at the top of the flame?

4

Draw a diagram of the Bunsen-burner flame, labelling the parts that are hottest.

5

Students often heat substances in a test tube with a Bunsen burner. Why would it be unwise to:

Unburnt match Pin

◗ Turn the Bunsen

burner off and remove the match and pin with tongs. Part B ◗ Re-light the Bunsen burner and turn the collar to produce

a blue flame again.

(a) use a yellow flame rather than a blue flame

◗ Use the tongs to hold the wire across the flame, close to

(b) position the test tube at the base of a blue flame?

the barrel of the Bunsen burner and observe the wire. ◗ Move the wire up a little and continue observing.

6

Why is the yellow flame often called the safety flame?

InveStIgatIon 1.4 Heating a substance in a test tube You will need: 100 mL beaker Bunsen burner and heatproof mat matches safety glasses test tube test-tube rack test-tube holder food colouring CAUTION Before you start heating, check the following: • If you have long hair, is it tied back? • Are you wearing safety glasses? • Is the Bunsen burner on a heatproof mat? ◗ Carefully pour water from a beaker into a test tube to a

depth of about 2 cm as shown in the diagram at right. Add a drop of food colouring to make it easier to see.

Pouring a liquid into a test tube

1 Investigating 11

◗ Light the Bunsen burner correctly

and heat the test tube gently in the blue flame as shown below. Remember that the open end of the test tube should be pointing away from you and your fellow students. The base of the test tube should be moved gently in and out of the flame. This prevents the liquid from splashing out of the test tube. Make sure that the test tube points away from you and other students. Move the base of the test tube in and out of the flame.

Keep the test-tube holder away from above the flame. Heating a test tube ◗ Once the water has started

boiling, stop heating and turn off the gas to the Bunsen burner. Place the test tube in the testtube rack. Leave it there until it has cooled before emptying it and cleaning up.

Discussion

12

1

Why is the test tube placed in a test-tube rack rather than in your hand?

2

Make a list of any changes you observed inside the test tube as you heated the water.

Core Science | Stage 4 Complete course

Danger in the laboratory

activities REMEMBER 1 outline the purpose of each of the following pieces of equipment. (a) Heatproof mat (b) Evaporating dish (c) Test-tube rack (d) Retort stand 2 Give three examples of equipment used when heating objects. 3 Explain why you should always wear gloves when working with corrosive substances. 4 If the teacher says it is safe to smell a chemical, outline the technique you should use. 5 identify which colour is the hottest flame in a Bunsen burner. How do you obtain this coloured flame?

THinK 6 identify which item of equipment you would use to: (a) hold a test tube that is to be heated (b) measure a volume of water exactly (c) transfer a small sample of a powder to a beaker (d) mix a sample of powder with water so it dissolves. 7 Look carefully at the picture of students in a laboratory on these two pages. (a) identify at least five dangerous situations you can see. (b) Explain why each situation is dangerous. 8 The following statements are all incorrect. Rewrite them so that they are correct. (a) Matches can be safely washed down the sink. (b) Always point a test tube towards you when heating so you can see what is happening inside it.

(c) Safety glasses need to be worn only when heating over a blue Bunsen burner flame. (d) Water spills do not need to be cleaned up because they are not dangerous.

cREATE 9 Select one of the safety rules and choose a strategy for publicising your message to the class. You might create a safety play poster, video clip or play. eBook e eBoo k plus l s Book Boo

10 Identify the equipment you will need to perform a number of laboratory processes by completing the Using equipment interactivity in your eBookPLUS. int-0200 11 Use the Robert Bunsen weblink to learn about the man after whom the Bunsen Burner was named. work sheets

1.1 Safety in the laboratory 1.2 Safety rules

1 Investigating 13

1.3

observing and inferring As scientists conduct their experiments, it is important to keep a record of all the measurements and observations made. Some observations are qualitative, meaning that they describe the results of an investigation: for example, The red kangaroo sheltered under a tree during the hottest part of the day. Quantitative observations are those where a measurement is made: for example. The male red kangaroo had a mass of 85.3 kg.

Measuring length Scientists measure the lengths of different objects accurately to compare sizes and estimate growth. The biologists in the photograph below are measuring the size and condition of a tranquillised polar bear as part of a study aimed at conserving these animals in their Arctic home.

Measuring Experiments conducted in science often involve measuring quantities such as length and mass. Measuring gives us an accurate way of knowing whether quantities change and, if so, by how much. This helps scientists to make conclusions from their experiments and to develop new ideas. Scientists all around the world use the metric system of units for their measurements.

The standard unit for measuring length is the metre (m). But length can also be measured in millimetres (mm), centimetres (cm) or kilometres (km). The following table shows how to convert between some common units of measurement. Measurement conversions 1 kilogram (kg) = 1000 grams (g) 1 kilometre (km) = 1000 metres (m) 1 metre (m) = 100 centimetres (cm) 1 centimetre (cm) = 10 millimetres (mm) 1 litre (L) = 1000 millilitres (mL) 1 cubic centimetre (cm3) = 1 millilitre (mL) 1 minute (min) = 60 seconds (s) 1 hour (h) = 60 minutes (min)

Sri Lankan spin bowler, Muttiah Muralitharan, has his bowling action carefully measured and analysed by Dr Jacque Alderson, a biomechanist from the University of Western Australia.

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Core Science | Stage 4 Complete course

Parallax error Measurements should always be made with your eye level with the reading you are taking. When scales are read from a different angle, the reading is not accurate. This type of reading error is called parallax error. Measuring correctly

• Never use the thermometer as a stirring rod. • Read the thermometer with your eye level with the top of the alcohol column. • Do not rest a thermometer near the edge of a bench where it is likely to fall off.

using data loggers

Measuring incorrectly results in a parallax error.

Measuring volume Liquids in tubes such as measuring cylinders are often curved at the top edge. The curve is called a meniscus. The edges of the meniscus may curve up or down. We always measure the volume of liquids from the middle flat section of the meniscus. 60 mL

60 mL

55

55

50

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40

Reading = 57 mL

A data logger is an electronic device that collects and records scientific measurements, which we call data. The measurement recorded by a data logger depends on the sensor that is connected to it. The sensor does the measuring and sends the information to the data logger. There are a number of different sensors available; for example, if a temperature sensor is attached to the data logger, temperature is measured and recorded. Data loggers are useful devices because they generally measure quantities very accurately. For example, they may record temperature accurate to 0.1 °C. Some data loggers can also store thousands of individual measurements and allow them to be downloaded to a computer to be converted to tables and graphs.

Reading = 56 mL

Measuring temperature A thermometer is used to measure temperature. The unit of measurement is commonly degrees Celsius (°C). The thermometers used in schools are filled with alcohol, dyed red so that it is easier to read. When using thermometers, remember these points. • Never rest the bulb of the thermometer on the bottom of a container being heated as the bottom may be hotter than the rest of its contents. • Ensure that the liquid you are measuring the temperature of fully covers the thermometer bulb.

A data logger and temperature sensor

1 Investigating 15

Reading scales In science, a scale or set of numbered markings generally accompanies each measuring device. For example, your ruler measures length, and its scale has markings enabling you to measure with an accuracy of 0.1 cm. A laboratory thermometer has a scale that measures temperature with an accuracy of 0.5 °C.

When reading a scale, it is important to determine what each of the markings on the scale represents. Practise reading the scales below. A

50

B

C

D

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Hot and cold G

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H

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I

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E 24

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The highest air temperature ever measured on Earth is 58 c. The measurement was taken in 1922 in Libya. The lowest temperature ever measured was in 1983 in Antarctica. That temperature was 86.6 c.

50

70

The temperatures measured by the thermometers A and B are 39 C and 23.6 C, respectively. What are the temperatures measured by thermometers C to J?

InveStIgatIon 1.5 Measuring temperature You will need: laboratory thermometer or data logger and temperature sensor 250 mL beaker paper towel ◗ Use the thermometer or data logger to measure the

temperature of: (a) the air inside the school laboratory (b) the air outside the school laboratory (c) refrigerated water in a small beaker (d) cold tap water in a small beaker (e) warm tap water in a small beaker

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Core Science | Stage 4 Complete course

(f) your armpit (take care, the thermometer is a delicate instrument). CAUTION Do not put the thermometer in your mouth! ◗ Copy and complete the following table so that you can

record your measurements neatly. Measuring temperature Substance or location Air inside the school laboratory Air outside the school laboratory Refrigerated water in a small beaker Cold tap water in a small beaker Warm tap water in a small beaker My armpit

Temperature ( C)

Measuring mass Mass is usually measured in kilograms (kg); however, in the science laboratory, you will often measure mass in grams (g). You will use either a beam balance or electronic scales to measure mass accurately. Electronic scales are the easiest to use. Simply adjust the balance reading to zero by pressing the tare button, place the object to be measured on the scales, and read the mass from the digital display. Follow these steps to measure mass using a beam balance:

‘zeroing’ the pointer. Do this by moving the heaviest sliding mass towards the pointer. Slide it until it just overbalances the pointer, and then slide it back to the nearest notch. Repeat this with the smaller masses in turn, except the one with the smallest sliding mass. The smallest mass should balance the pointer, so that it lines up with the zero (balance) mark.

Step 2: Put the object to be measured on the pan of the beam balance. Liquids and grains should not be placed directly on the pan. To find the mass of these substances, they need to be poured into a container. The dry, empty container should be measured first, and its mass should later be subtracted from the mass of the container with the substance in it.

Step 4: Add the masses on each of the arms to determine the total mass. The tomato in the diagram below has a mass of 126.3 grams.

Step 3: When an object is put on the pan, the pointer moves. You can determine the object s mass by

Step 1: Make sure that the balance is ‘zeroed’ before using it by moving all of the sliding masses to the zero notches and checking that the pointer on the arm of the balance lines up with zero.

Sliding masses

Pan

InveStIgatIon 1.6 Estimating mass You will need: beam balance or electronic scales pen watch safety glasses 100 mL beaker jar lid 50 mL water teaspoon sugar ◗ Record your estimates of the masses of each of the

Arms

0 0

100 10

0

1

Pointer

200g

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Estimating and measuring mass Estimated mass (g)

Item

Measured mass (g)

Difference (g)

Pen Watch Safety glasses 100 mL water 2 teaspoons of sugar

items in a table like the one at right. ◗ Measure the masses of the pen, watch and safety glasses

◗ Determine the degree to which your estimates were

incorrect by calculating them as a percentage error. For each item, calculate the percentage error using:

using a beam balance or electronic scales. ◗ The water and the sugar cannot be put directly on the

pan. Record the masses of the beaker and the jar lid on their own.

difference (g) × 100 = % error measured mass (g)

◗ Add 50 mL of water to the beaker. Record the combined

mass of the water and the beaker. Subtract the mass of the beaker alone from the combined mass. Do the same with 2 teaspoons of sugar in the jar lid. Alternatively, put the empty container on the electronic scales before adding the water or sugar, and press tare .

Discussion 1

Which was your most accurate estimation?

2

By how much did your least accurate estimation vary from the measured mass?

3

Is it easier to estimate larger or smaller masses? Explain why you think this is the case.

◗ Record in the table whether your estimated mass was

higher or lower than the measured mass, and by how many grams. This is called the difference.

1 Investigating 17

Measuring time

Making observations

We use clocks and watches to tell the time, but scientists often need to record how long an event takes. To do this accurately, they use stopwatches or electronic counters. The standard unit for measuring time is the second(s). Familiarise yourself with a stopwatch. There is generally a start/stop button and a reset button. Push the reset button when you wish to start timing in a new experiment and when you have finished timing your experiment and need to return your stopwatch to zero.

Some of the most important scientific discoveries have come about through simple scientific observations. For example, in 1928, Alexander Fleming accidentally discovered the first antibiotic when he was observing mould (read more about this on page 29).

A typical stopwatch used to record time accurately

InveStIgatIon 1.8 How observant are you? You will need: large beaker short candle lid or watchglass matches electronic scales

Watchglass

of the candle and lid (or watchglass) using electronic scales and record your results.

Timing a fall

◗ Light the candle.

You will need: stopwatch metre ruler pen

as many observations as you can while it is alight. (Interestingly, Michael Faraday, a nineteenth century scientist famous for his discoveries in electricity and chemistry, was able to make 53 observations of a burning candle!)

surface to the ground using a metre ruler. ◗ Time how long it takes for a pen to fall from the top of

◗ After several minutes, place an upturned beaker over

the candle and continue to record your observations.

the bench to the ground. Repeat two more times. ◗ Calculate the average time taken in the three trials.

◗ Weigh the candle and lid (or watchglass) again and

record your results.

◗ Repeat your experiment but swap roles within

your group so that each member has a turn timing, recording and managing (such as saying go when it s time to start the drop). ◗ Record your results in a table like that below.

18

Place a beaker over the burning candle after several minutes.

◗ Observe the candle for several minutes and record

◗ Measure the length from the top of a lab bench

Discussion 1

How many observations did you record? What was the greatest number recorded by a member of your class?

2

What change occurred in the mass of the candle and lid?

3

Can you suggest why the mass of the candle may have changed?

Time taken (s) Length (cm)

Candle

◗ Weigh the initial mass

InveStIgatIon 1.7

Name of student timing

Beaker

1

2

3

Average

Discussion

inferring and hypothesising

1

Was the time taken to fall the same in each trial? Can you explain why?

2

Explain why it is useful to calculate an average.

3

Explain why you used a stopwatch in this experiment instead of the second hand of a clock or watch.

After making some initial observations, scientists may make an inference or suggested explanation about what has happened. For example, you may have inferred in Investigation 1.8 that the wax of the candle was burnt in the experiment, causing the candle to lose mass.

Core Science | Stage 4 Complete course

Scientists wishing to investigate further often come up with a hypothesis or suggestion describing what may happen. Hypotheses should be measurable so that they can be tested. For example, in Investigation 1.8, you might hypothesise that the mass lost by the candle goes into producing the mass of smoke observed. You might conduct further experiments to produce quantitative observations (or data) that support or reject your hypothesis. If the observations support your hypothesis, you might be able to make the conclusion that the mass lost by the candle was converted to smoke. You might like to re-design Investigation 1.8 to test this hypothesis. A summary of the process of investigating is shown on the right.

activities REMEMBER 1 Describe what you must be sure to do when measuring the volume of a liquid accurately. 2 Explain why you should not rest the bulb of a thermometer on the bottom of the container when measuring the temperature of a liquid while heating.

Initial observations are made.

An inference is based on these observations.

A hypothesis is made.

Data is collected in experiments.

Conclusions are made.

9 Look at the following diagrams of measurements obtained from a beam balance. (a) What is the mass of object A? (b) What is the mass of object B? (c) What is the largest mass that could be measured on this beam balance? Object A 0 20

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3 identify the standard unit of mass.

0

4 identify a device used to measure mass in a school laboratory.

Object B 0

THinK 5 Look at the figure on page 15 showing parallax error. (a) What is the real length of the matchstick shown? (b) What approximate length of the matchstick would you get due to parallax error? 6 Convert the following lengths into millimetres. (a) 25 centimetres (b) 2.5 metres 7 Luke measured the mass of a beaker of water as 240 grams. He tipped out the water and measured the mass of the beaker as 105 grams. (a) calculate the mass of the water in grams. (b) Express the mass of water in kilograms. (c) Explain how Luke could have improved the procedure in his experiment to achieve a more accurate reading. 8 Decide whether each of the following statements is an observation, hypothesis or conclusion. (a) Candles require oxygen from the air to burn. (b) The candle went out when I placed a glass over it. (c) Without oxygen from the air, a candle would quickly go out.

0

200 g

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10

100 g

200 g

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100 g

inVEsTiGATE 10 Sit quietly in a nearby outdoor location and write down as many observations as you can within five minutes. Use as many senses as you can, except taste. (a) identify the sense that you used the most. (b) Which other senses did you use? (c) compare your observations with those of other classmates. What interesting observations did others make? eBook plus

11 Identify the temperature on a number of different thermometers by completing the Reading scales interactivity in your eBookPLUS. int-0201 work sheet

1.3 Observations and inferences

1 Investigating 19

1.4

Reporting on investigations Once scientists have completed their investigation, they need to communicate to other scientists what they did, their qualitative and quantitative observations and their conclusions. This is done using a scientific report. You may have some experience in writing reports in other subjects. However, a scientific report takes the format outlined below. Aim This is what you intended to do in the investigation. Materials This is a list of all the equipment and chemicals that were used. Method This is the procedure followed in the investigation and described as a series of steps. It may be useful to include a labelled diagram of the set-up of equipment used. Be sure to include what you are actually recording in the experiment. Results This is a presentation of your data, and it may include qualitative observations. Data is usually organised into tables and presented as graphs. Discussion In this section, scientists explain their results: why they think they obtained the results they did. They may refer to the research of other scientists. They may also describe any problems encountered in the investigation and make suggestions on improvements. Conclusion This is a summary of the overall findings. The conclusion must relate to the aim of the investigation.

Drawing laboratory equipment Scientific drawings can be used in laboratory reports to show how equipment was set up. It is important for the drawings to be clear and easy to understand. When drawing scientific diagrams, you should: • always draw in pencil • use a ruler to draw straight lines • label the equipment drawn • draw only a cross-section of the equipment • not put lines closing the top of open glassware. Some examples of equipment drawn scientifically are shown above right.

20

Core Science | Stage 4 Complete course

Tripod and gauze mat

Beaker

Test tube

Bunsen burner and heatproof mat

Conical flask

Retort stand, bosshead and clamp

Filter funnel and filter paper

Keeping a record When making observations, it is helpful to organise the data in a table. Information presented in this way is often easier to read. Graphs can then be constructed from the table to make it even easier to see patterns in the data. The heading for each column is a clear label of what has been measured. Always include the units used in the headings.

Distance (cm) 0 2 4 6 8

Time for ant to travel between markers (s) 0 3 7 8 12

Enter the data in the body of the table. Do not include units in this part of the table. Use a ruler to draw lines for rows, columns and borders.

Pie charts are useful for showing the parts that make up a whole. For example, a pie chart can be used to show the percentages of different substances in the Earth s crust. Other (10%) Oxygen (46%)

Calcium (4%) Iron (5%) Aluminium (8%)

Silicon (27%)

Number of students

Bar and column graphs are used to display data that is not continuous; this means that one piece of data does not relate to the next. For example, a bar graph can be used to show the number of students in a class with a particular hair colour. 10 8 6 4 2 0 Black

Brown

Red

Blond

Colour of hair

Line graphs have a horizontal x-axis and a vertical y-axis. They are often used to represent continuous or connected data. A line graph is used to show how something changes. For example, line graphs could be used to show how quickly a plant grows over time. A line graph can be used to predict what might happen in the future.

Height of plant (cm)

1.5

An example of a good quality report of an experiment

1.0

Line graphs are useful for predicting values between those that you actually observed.

0.5

Graphing Graphs are used to make data easier to interpret. The type of graph used depends on the type of data to be displayed.

0.0 0

10

20 30 Number of weeks

40

1 Investigating 21

Activity 3

InveStIgatIon 1.9

◗ Use an eye-dropper to put one drop of methylated spirits

onto the back of your hand. Blow air gently across the back of your hand.

Recording observations in a table You will need: test tubes 50 mL beaker eye-dropper vinegar sodium carbonate methylated spirits starch suspension safety glasses

test-tube rack spatula drinking straw sodium bicarbonate copper sulfate limewater iodine solution

Activity 4 ◗ Quarter-fill a very small beaker with limewater. Gently

blow out through a drinking straw into the limewater. Be careful not to share straws.

CAUTION Safety glasses should be worn while conducting these experiments. ◗ Draw a table like the one below to record your

observations in of each of the following activities. Activity Summary of what was done

Observations

1 2 3 4

Activity 5 ◗ Put a few drops of starch suspension in a clean test

5

tube. Add a drop of iodine solution.

Activity 1 ◗ Pour vinegar into a clean test tube to a depth of about 1 cm. Add a spatula full of sodium bicarbonate.

CAUTION Take care not to get iodine solution on your skin or clothes.

Activity 2 ◗ Quarter-fill two clean test tubes with water. Add a dry

spatula full of sodium carbonate to one test tube. Shake the tube until the sodium carbonate dissolves. Add a dry spatula full of copper sulfate to the other test tube and shake it until the crystals dissolve. Pour the contents of the second test tube into the first.

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Core Science | Stage 4 Complete course

Discussion 1

What senses did you use in making your observations?

2

Outline two safety precautions involved in this investigation.

3

Explain why it is important to use small quantities of chemicals when doing experiments like these.

4

Explain why it is useful to present the observations in a table.

5

In activity 4, you had to pour limewater into the beaker. If you took more limewater than required, explain why it is not a good idea to return any unused limewater to the original bottle.

InveStIgatIon 1.10

Clamp

Bosshead

Temperature graphs

Thermometer

A line graph is a useful way to present the results of an experiment and gives an overall picture of the results. A line graph can also be used to predict values that occur between, or outside, those measured during an experiment. The aim of this experiment is to observe how the temperature of water changes while it is heated over a Bunsen burner. You will need: 100 mL measuring cylinder 250 mL beaker Bunsen burner heatproof mat matches tripod gauze mat retort stand, bosshead and clamp thermometer or data logger and temperature sensor stopwatch safety glasses

Retort stand Beaker

Gauze mat Tripod Bunsen burner Matches

Heatproof mat ◗ Plot a line graph of the data you have collected on a

sheet of graph paper using labels like those below. ◗ Use a measuring cylinder to measure 100 mL of water. ◗ Pour the water into the beaker.

100 90

sure that the bulb of the thermometer is not on the bottom of the beaker or out of the water.

80

◗ Wait for a minute to allow the thermometer to adjust to

the water temperature. ◗ Measure the initial temperature of the water and record

it in a table. The initial temperature is recorded when time is 0 minutes. Time (min)

Temp ( C)

Time (min)

Temp ( C)

Temperature ( C)

◗ Set up the equipment as shown in the diagram. Make

70 60 50 40 30 20

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5 ◗ Put your safety glasses on. ◗ Light the Bunsen burner according to the guide on

page 10. ◗ Open the air hole and heat the beaker over a blue flame. ◗ Measure and record the temperature of the water every

minute for 10 minutes. ◗ Turn off the Bunsen burner and allow the equipment to

cool.

1

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Time (minutes) ◗ Draw a smooth line near as many points as possible to

show the overall trend in the water temperature over time.

Discussion 1 Why didn t you record the starting temperature of the water as soon as you poured the water into the beaker? 2 Describe in words how the temperature increases. 3 How does your graph compare with those of other groups? 4 Predict what would happen to the temperature of the water if you continued heating for another two minutes.

1 Investigating 23

Activities REMEMBER 1 Explain why scientists write reports about the experiments they conduct. 2 Identify the part of a laboratory report where a graph of temperature vs time would be drawn. 3 Distinguish between the results of an experiment and the conclusions made. 4 Identify the heading of your report of an experiment under which the following information should be included. (a) Suggestions for improvements to your experiment (b) Graphs and tables (c) A description of what you did (d) A statement saying what you found out by doing the experiment 5 A hypothesis is often included in a scientific report, usually after the ‘aim’ heading. Define the term ‘hypothesis’.

THINK 6 A student measured the temperature in each of the classrooms at her school so she could compare them. Identify the type of graph that the student should select to display her results. 7 Construct a neat, labelled, scientific diagram of the two sets of equipment that would be needed to perform the following activity safely. ◗ Part 1: Muddy salt water is being poured from a beaker into a filter funnel (with filter paper). The filter funnel is resting in the opening of a conical flask. ◗ Part 2: The filtered salt water, now in an

24

Core Science | Stage 4 Complete course

evaporating dish, is being heated by a Bunsen burner. The evaporating dish is supported by a gauze mat on a tripod.

INVESTIGATE 8 Investigate whether adding salt to water changes how the temperature rises when the water is heated. Design an experiment to test your answer. Write a scientific report outlining the design of your investigation.

ANALYSE AND EVALUATE The computer screen below shows data collected by a data logger for the experiment in which water is heated to boiling in a beaker. A temperature sensor was used to take the measurements. If you were at this computer, you could scroll through every temperature measurement in the table. The computer has graphed all these data. Now let’s see how much you’ve learned about interpreting line graphs. 9 How often did the data logger collect temperature readings?

10 How long did the whole experiment go for? 11 Identify the number of individual temperature readings the data logger has stored. 12 Identify when the heating of the water began. 13 Identify the temperature of the water when heating began. 14 Identify the temperature of the water when heating finished. 15 Identify when the water began to boil. 16 Calculate the rate (in degrees per second) that the water temperature rose between 100 and 400 seconds. 17 The water continued to be heated even when its temperature reached boiling point, yet its temperature did not rise beyond 100 °C. What has happened to all the energy that was being put into the water if it isn’t causing the water temperature to rise? (Hint: Think about what happens to water while it is boiling.) work sheets

1.4 Scientific reports 1.5 Scientific drawing skills 1.6 Data analysis

1.5

Designing investigations When carrying out investigations, it is important to do so scientifically. This means, for example, using the most accurate equipment available. In many of the experiments you will do, the procedure you need to follow will be provided for you. In some cases though, you will need to design your own experiments as part of your investigation. Let s look at some important principles to consider when designing investigations.

Fair tests Experiments are generally designed to test hypotheses. A hypothesis is a testable idea developed from previous observations. For example, David loved playing handball in the playground, and it seemed to him that tennis balls falling from greater heights bounced higher. He wanted to test his hypothesis. An important part of any investigation is to consider all the factors, or variables, that may affect the outcome of an experiment. David thought that the most important variable to affect the bounce of a ball was the height it fell from. In most cases, many factors may affect the outcome of an experiment. For example, the height that a ball bounces might depend not only on the height from which it fell but also on the type of ball; after all, would you expect a cricket ball to bounce as much as a tennis ball? The amount of air in a ball might also affect its bounce; a fully inflated basketball usually bounces higher than a partially deflated one. When designing investigations in science, it is important to design a fair test. In a fair test, only one variable is changed at a time, and all other variables are controlled, or kept the same. If this wasn t the case, it would be impossible to tell which variable caused the effect we are studying.

The phrase Cows Moo Softly is useful in remembering how to plan a fair test: • Change one thing. • Measure something. • Keep everything else the same. In David s case, he will vary the height that a tennis ball is dropped from but will keep everything else the same, such as the type of ball, how much air is in the ball and the type of surface it is dropped onto. To enable him to make conclusions from his investigation, he collected quantitative data; that is, he measured the height of the tennis ball s bounce and repeated his experiment several times for each height tested. When designing fair tests, you might find it helpful to use a table like the one below to identify all the variables.

Investigating whether the height from which a ball is dropped affects the height of the bounce

Investigation: Does the height from which a ball is bounced affect the height of its bounce? Controlled variables (What I will keep the same) • The type of ball • How much air is in the ball • The type of surface it is dropped onto • Dropping the ball from a stationary point

Independent variable (What I will change) • The height from which the ball is dropped

Dependent variable (What I will measure) • The height of the ball’s bounce

1 Investigating 25

including a control In some investigations, it is important to include a control. A control is a repetition of the experiment in which the independent variable being tested is not applied and so all the variables are controlled. Results from the control are compared with those obtained when the independent variable has been included. This allows us to test whether the independent variable we are investigating really has an effect, or whether other variables that we may not have thought of could be playing a part. For example, if we want to investigate whether a ball being wet affects how high it bounces, we might compare the height of a wet ball s bounce with that of a dry ball dropped from the same height. The results obtained using the dry ball act as a control, or comparison.

Reliability The results obtained from experiments are used to make conclusions, but what if the measurements made are incorrect? Errors often arise in experiments; sometimes they are one-off errors, perhaps because the experiment was not done carefully. Other times the errors may be more difficult to eradicate because the equipment we used is not as accurate as it should be, or the samples we are testing are faulty. To prevent one-off errors from affecting your conclusions, experiments should be repeated a number of times. When repeating experiments, they should be done in the exact same way each time. For example, when comparing

26

Core Science | Stage 4 Complete course

Including a control (left) to test whether wetting a ball (below) affects how high it bounces

the bounce of a wet ball with that of a dry ball, it would be sensible to repeat the experiment, say, five times with the same ball and with the same controlled variables. If the results obtained are similar each time, then we say the results are reliable. If there was a significant difference between your results for each test, you may need to review the way in which the experiment was done. Would you say the results presented in the table below are reliable? Height of bounce (m) Trial

Dry tennis ball (control)

Wet tennis ball

1

0.9

0.7

2

1.0

1.0

3

0.8

0.8

4

1.0

1.2

5

1.1

1.1

Average

1.0

1.0

What conclusion would you make based on the average results? Would you have drawn the same conclusion based on the results of trial 1 only?

InveStIgatIon 1.11

◗ Put the diving bell in the measuring cylinder and mark

the position of the bottom of the diving bell on the measuring cylinder s scale. Record this value in a suitable table.

Floating in salty water The water in the Dead Sea, a lake near Jordan in the Middle East, has an unusually high salinity; in fact, it is nine times higher than that of the ocean. Tourists flock to the lake because it is believed the water has health benefits and to experience the water s unusually high buoyancy.

◗ Carefully remove the diving bell. ◗ Add a level teaspoon of table salt to the measuring

cylinder and dissolve it in the water by shaking carefully or stirring. ◗ Put the diving bell back in and mark and record its

position. ◗ Repeat this experiment using a second, a third, and

finally a fourth teaspoon of salt. ◗ Design a suitable table to record your results

you will need a column indicating the number of teaspoons of salt added and a column listing the position of the diving bell (using the scale on the measuring cylinder).

◗ Draw a line graph of salinity (teaspoons of salt added)

on the x-axis versus the height of the diving bell (reading on the measuring cylinder) on the y-axis, and draw a smooth line of best fit.

Measuring cylinder

Cotton thread Tourists demonstrate the unusual buoyancy caused by high salinity in the Dead Sea.

Diving bell

Investigate whether the salinity of water affects how high an object floats in water.

Water and dissolved salt

You will need: 100 mL measuring cylinder small test tube cork or rubber stopper elastic band permanent marker scissors table salt teaspoon or spatula ◗ Fill the measuring cylinder to the 100 mL mark with tap

water. ◗ Make a diving bell by half-filling a test tube with tap

water; seal the top with a stopper.

The diving bell

Discussion 1

Write a conclusion to the experiment about whether the salinity of water affects how high an object floats in water.

2

Identify the control in this experiment.

3

Explain how these results support your conclusion.

4

Repeating this experiment would be very time consuming so, to check the reliability of your findings, compare your results with those of other groups. The easiest way to do that is to compare others graphs with yours.

5

Extrapolate (extend) your graph to predict the position of the diving bell if six teaspoons of salt were added.

◗ Tie a piece of cotton thread securely around the top of

the test tube so it can be carefully moved in and out of the measuring cylinder. ◗ Check that the test tube floats off the bottom but not

higher than halfway up the measuring cylinder. If not, adjust the volume of water in the test tube.

1 Investigating 27

activities REMEMBER 1 Define the term variable . 2 Explain the difference between the independent and dependent variables in an experiment. 3 Explain why only one variable at a time should be changed in experiments.

THinK 4 identify some variables that might affect: (a) how quickly a pot plant grows (b) the cost of an airfare overseas (c) the time it takes you to travel to school in the morning. 5 Advertisements for washing powders and liquids often claim that they are more effective than others. Imagine you are conducting an experiment to test a range of washing powders and liquids. (a) Prepare an outline of a procedure for your experiment. (b) List the variables that you will need to control. (c) Which variable will you change? (d) How will you compare the results of your tests? 6 Catherine and Celine are trying to find out whether ceramic or glass cups are better for keeping water hot. The illustration below shows their experiment in progress.

(a) identify at least two errors in their experimental design. (b) identify all the variables that could affect the results of Catherine and Celine s experiment. (c) identify any variables that Catherine and Celine do not need to control. (d) Write a step-by-step outline of the procedure that they could use to find out which cup keeps water hotter.

AnALYsE 7 Simon and Jessie did an experiment to find out how effectively two plastic cups maintain the temperature of near boiling water. Their data is shown below. Comparing plastic cups Temperature ( C) Time (min)

Core Science | Stage 4 Complete course

DEsiGn 8 Design and carry out an experiment to investigate one of the following. ◗ What conditions affect the germination of seeds? ◗ Which conditions lead to the greatest plant growth? ◗ Which colour cloth is the warmest? ◗ How can a vase of flowers be kept fresh longer? ◗ Which brand of paper towel is the most absorbent? ◗ What affects how quickly objects fall? ◗ Which brand of batteries lasts the longest?

Simon s cup

Jessie s cup

0

90

90

inVEsTiGATE

10

47

58

20

29

39

30

22

31

40

20

26

50

20

23

9 The aim of this experiment is to find out whether distances are easier to judge with two eyes than just one. You can do this by shooting for goal with a basketball or netball from a particular spot under three conditions: ◗ left eye closed ◗ right eye closed ◗ both eyes open. To produce reliable results, more than one person should take the shooting test and each goal shooter should have several attempts. Plan and carry out your experiment. Write a formal report for the experiment including a table of results and a conclusion. In your discussion section: ◗ identify the independent and dependent variables ◗ describe the strategies you used to ensure that this was a fair test.

(a) construct an appropriate graph to display the data. (b) identify which cup maintained the temperature of the water more effectively.

Catherine and Celine s experiment in progress

28

(c) Estimate the temperature of the water in Simon s cup 15 minutes after timing commenced. (d) Use your graph to predict how long it would have taken the water in Jessie s cup to drop to a temperature of 20 C.

work sheet

1.7 Fair testing

1.6

PREscRiBED Focus AREA nature and practice of science History of science

Famous scientists Scientists use scientific investigations to help us understand our world. They look for ways of improving our lives by developing and testing their ideas. Many of the important scientific discoveries of the past began as questions, observations and experiments from famous scientists such as Alexander Fleming, Benjamin Franklin, Louis Pasteur, Albert Einstein, Galileo Galilei, Marie Curie and Isaac Newton. Although our knowledge of science is advancing every day, a number of fundamental scientific ideas were developed some time ago. As well as coming up with new theories and ideas, modern-day scientists build on the knowledge of pioneering scientists.

Alexander Fleming A scientific discovery can start from a simple observation. In 1928, Alexander Fleming made an accidental discovery that was to change medicine. He was working on a completely different experiment when he discovered that some mould spores in the air had contaminated a petri dish growing bacteria. He noticed that the bacteria had stopped developing where the mould had landed. The mould contained a substance called penicillin. Just over ten years later, Australian-born scientist Howard Florey and his colleagues successfully purified the mould so that it could be used as a commercial antibiotic. Penicillin was the first antibiotic to be used, and it is still used for the treatment of serious bacterial infections.

Benjamin Franklin Many scientific theories are initially prompted by observations. From an observation, a scientist can create a hypothesis — an educated guess about what is happening. Benjamin Franklin, a famous American scientist, observed lightning and developed a hypothesis that lightning bolts were actually powerful electric currents. To test his hypothesis, Franklin flew a kite during a thunderstorm in 1752. He attached a metal wire to the tip of the kite as a conductor, and a key to the string. When Franklin placed his knuckle near the key, he observed a spark jump from the key to the knuckle. The test result helped to confirm his hypothesis. Franklin was lucky to have survived his experiment — several other attempts at the kite experiment electrocuted other scientists! His work led to the invention of the lightning rod, which is a metal spike attached to the top of a building. When hit by lightning, the lightning rod diverts the electricity down the spike and to the ground (through the path of least resistance). This helped solve the problem of buildings catching fire after being struck by lightning.

Scottish bacteriologist Alexander Fleming discovered the first antibiotic, which he called penicillin. He observed that a tiny piece of mould that had contaminated his experiment stopped the growth of bacteria.

Artist s impression of Benjamin Franklin and his son performing the kite experiment

1 Investigating 29

Although his research and calculations were used in the development of the atomic bomb, No microbial Boil growth Einstein himself was a pacifist, strongly against the use of nuclear weapons. Albert Einstein was one of the Stem broken, Microbial Boil greatest thinkers in science history. allowing air to growth His theories form the basis of a enter flask large portion of modern physics, Pasteur s experiment particularly in the study of the A control is an experiment universe. where each part is controlled or kept constant. Controls are used to compare against those experiments that have introduced a variable. For example, in further experiments, Pasteur selected different variables. He exposed meat broth to clean mountain air and dirty city air. However, in this experiment Pasteur also included a control — broth that was not exposed to air. He found that a lot of bacteria grew in the dirty city air and only a small number of bacteria Albert Einstein writing an equation on a grew in the clean mountain air. blackboard The use of a control helped Pasteur determine that the appearance of bacteria must have had something to do with air, because bacteria grew Galileo Galilei was born in Italy only in the broth exposed to the air. in 1564. In his younger days he studied physics and mathematics. In 1609, Galileo used his technical and mathematical skills to build Albert Einstein was born in his own telescope. He was the first Germany in 1879. At 26, he began person to use a telescope to study to publish his ideas on science, the night sky. In 1610 he published and he won the Nobel prize for the book Starry Messenger. In it he physics in 1921. claimed to have seen mountains One of Einstein s most 2 on the moon and four small recognised equations is E = mc . bodies orbiting Jupiter, and to have This rule describes how a large demonstrated that the Milky Way amount of energy (E) can be was made up of stars. In 1632, released from a small amount of Galileo published work supporting matter (of mass m). For example, the theory of Copernicus that the this equation shows that the sun, not the Earth, was the centre of amount of energy released when our galaxy. Galileo was found guilty a mass equivalent to that of a golf of heresy (contradicting the church) ball is converted into energy is and sentenced to life imprisonment, enough to power the lights of the but he served the sentence under Sydney Cricket Ground, and keep supervision in his home. He died in them running continuously for over 50 years. January 1642. Time elapsed

Louis Pasteur To properly test an idea, a fair test of a hypothesis needs to be made. In a fair test, all factors should remain the same except one: the independent variable. In a simple experiment you change one independent variable at a time and observe what happens. One of the greatest biologists of the nineteenth century was the French scientist Louis Pasteur. In 1859 he designed an experiment to test his hypothesis that bacteria growing on old food came from the air. At the time it was believed that life forms could generate spontaneously from non-living matter. Pasteur boiled meat broth in flasks to sterilise the flask and broth. To create a variable, Pasteur used one normal flask and one flask with a very thin, S-shaped neck that prevented dust in the air from entering the flask. The result was that micro-organisms grew in the meat broth in the flask open to the air, but not in the one with the S-shaped neck. The micro-organisms in the air became trapped in the bent section of the neck. Because micro-organisms grew in the flask exposed to the air but not in the other, this experiment supported Pasteur s hypothesis that germs arrived from the air outside the flask.

30

Core Science | Stage 4 Complete course

Galileo Galilei

Albert Einstein

of his work was done at home when Cambridge was closed for two years due to the plague. He is well known for his law explaining gravity, his laws of motion, his study of light, and for inventing calculus (a branch of mathematics). A unit of force, the newton, has been named after him. Newton died in London in March 1727. Much of modern physics is based on his work.

Marie Curie Marie Curie was born in Warsaw in 1867. She studied mathematics and physics. In 1903, she shared the Nobel prize in physics with her husband Pierre Curie and Antoine Henri Becquerel for their work studying radiation. In 1911, she won the Nobel prize in chemistry for discovering the elements radium (used in the treatment of cancer) and polonium. Curie was the first person ever to win the Nobel prize twice, and the first woman ever to win. Curie was a great humanitarian. She promoted the medical uses of radiation and X-rays. During World War I she created ‘X-ray vans’ and travelled to where soldiers needed medical help. When Curie died in July 1934, her body had been severely affected by the radiation she had been working with.

INVESTIGATION 1.12

REMEMBER Marie Curie conducting an experiment

Isaac Newton Sir Isaac Newton was born in England in 1642. He attended Cambridge University, but much

◗ Label the third beaker ‘control’.

Do preservatives stop the growth of bacteria? You will need: chicken stock cube beaker (1 L) hot tap water (750 mL) stirring rod 3 beakers (250 mL) teaspoon

Activities

◗ Place the three small beakers on a

warm windowsill for two days.

DISCUSSION vinegar salt masking tape pen or marker

◗ Place a chicken stock cube in a

1

2

1 L beaker and add 750 mL hot tap water. ◗ Stir the solution with a stirring rod

until it is consistent. ◗ Pour 200 mL of the mixture into

3

each of three 250 mL beakers. ◗ Add one teaspoon of vinegar to a

small beaker and use the pen and masking tape to label the solution ‘vinegar’. ◗ Add one teaspoon of salt to a small

beaker and label the solution ‘salt’.

Salt is one of the most widely used of all food preservatives. Suggest a hypothesis relating to salt that could be tested by this experiment. Observe the three solutions after two days. Large amounts of bacteria make the solutions go cloudy. Describe the degree of cloudiness of each solution and record in a suitable table. Which preservative was the most effective at stopping bacterial growth?

4

What role did the control play in this experiment?

5

Was your hypothesis supported by the results of this experiment? Explain.

1 Outline the important observation that Alexander Fleming made that led to the development of the first antibiotic. 2 Recall the hypothesis regarding lightning that Benjamin Franklin put forward. 3 Outline the scientific discoveries that Sir Isaac Newton made. 4 Explain what the equation E = mc 2 represents. What did this scientific discovery lead to? 5 Describe how the work of Marie Curie is important in medical science today.

THINK 6 Identify the senses that Franklin used to make observations during his kite experiment. 7 Identify the control that Louis Pasteur used in his experiment. Why was it important in helping support his hypothesis? eBook plus

8 Use the Louis Pasteur weblink in your eBookPLUS to learn about a process he invented to extend the life of liquids. What is this process called? How is it used today?

1 Investigating 31

LooKIng BaCK 1 Match the following scientists with their work. Scientist

4 Name these pieces of equipment and describe what they are used for.

Work (a)

(a) Physicist

A Investigates how rocks and mountains form

(b) Chemist

B Studies living things

(c) Biologist

C Explains things like movement, heat and light

(d) Astronomer

D Studies how substances react with others

(e) Earth scientist

(b)

(c)

(f)

(d) (e)

E Studies the sky

2 Match the scientist with the discovery in the list below. Scientist

Discovery

(a) Isaac Newton

A Lightning bolts are electric currents.

(b) Louis Pasteur

B Micro-organisms are carried in the air.

(c) Marie Curie

C Four moons that orbited Jupiter

(d) Galileo Galilei

D Penicillin

(e) Alexander Fleming and Howard Florey

E Gravity

(f) Benjamin Franklin

F Radium

3 Copy this diagram of a Bunsen burner and complete all of the missing labels.

5 Identify the temperature measured by each of the two thermometers shown below. (a)

(b) 90

18

80

17

70

16

6 List two safety rules and explain why they are important. (a) (e) (b) (f)

(c) (d)

32

Core Science | Stage 4 Complete course

7 Rewrite the following sentences correctly by selecting the appropriate words in italics. (a) When lighting a Bunsen burner, light the match before/immediately after turning on the gas. (b) When using a thermometer to measure the temperature of a liquid as it is heated, place the bulb of the thermometer on the bottom/near the centre of the beaker. (c) When heating a test tube, hold the test tube using tongs/a test-tube holder at the top/middle of the test tube and keep it steady/move it back and forth over the flame.

8 The steps used to light a Bunsen burner can be displayed as a flow chart, as shown below. Use the information in the flow chart to construct a storyboard with six scenes to show how a Bunsen burner is lit correctly and safely.

10 Four students each measured the temperature in the same classroom using a thermometer. Their results were:

LIGHTING A BUNSEN BURNER Place the Bunsen burner on a heatproof mat.

Student

Temperature ( C)

1

23.5

2

24.0

3

25.0

4

22.0

(a) Construct a bar graph of these results. (b) Propose some possible reasons for the differences between measurements.

Ensure that the air hole is closed.

Light the match.

Open the gas tap.

Hold the burning match just above the top of the barrel.

9 Construct a table with three columns headed Observation , Hypothesis and Prediction . In the table, write each of the statements below under the correct heading and in their correct sequence, so that a scenario is followed across each row. • I am afraid of heights. • A snail has eaten holes in the leaves of my African violet plant, but hasn t touched the flowers. • I will experience similar symptoms if I stand at the top of another building, a cliff or bridge. • My CD has been damaged. • Snails eat leaves, but not flowers. • My CD skips (briefly stops playing) when I play it. • When visiting the top deck of Sydney Tower, my heart started beating more quickly and loudly, my palms sweated and I felt a bit dizzy. • If I put a different flowering plant in place of my African violet each night, the snail will eat only the leaves of each plant, and ignore the flowers. • If I try playing my CD in someone else s CD player, it will still skip.

11 The following graph shows how far from the starting point a snail moves in an experiment.

Distance from starting point (cm)

Check that the rubber tubing is connected properly to the gas tap.

30 25 20 15 10 5 0 0

1

2

3

4 5 Time (min)

6

7

8

(a) Calculate how far from the starting point the snail was 7 minutes after timing began. (b) During what times did the snail not move at all? (c) What does the graph tell us about the snail s movement between 7 and 8 minutes after timing began? (d) Propose why a smooth line was not drawn in this graph. 12 Look at the photograph below.

(a) What qualitative observations do you think the scientist can make from this experiment? (b) Propose two different quantitative observations the scientist might make from this experiment. (c) Propose what might be the aim of this experiment.

1 Investigating 33

13 The following table shows the winning times for the men s 400 m freestyle swimming event. The data is from various Olympic games from 1896 to 2008. Time (min:s)

Year

Name, country

1896

Paul Neumann, Austria

8:12.60

1908

Henry Taylor, Great Britain

5:36.80

1920

Norman Ross, USA

5:26.80

TEsT YouRsELF

1932

Buster Crabbe, USA

4:48.40

1948

Bill Smith, USA

4:41.00

1960

Murray Rose, Australia

4:18.30

1972

Bradford Cooper, Australia

4:00.27

1984

George DiCarlo, USA

3:51.23

1996

Danyon Loader, New Zealand

3:47.97

2000

Ian Thorpe, Australia

3:40.59

1 Identify which of the following is an important safety rule in science. A When smelling chemicals, place your nose carefully over the container. B Dispose of all materials in the rubbish bin. C When reading the volume of a liquid, always read the bottom of the meniscus. D Point test tubes away from your eyes and away from (1 mark) your fellow students.

2004

Ian Thorpe, Australia

3:43.10

2008

Taehwan Park, Korea

3:41:86

(a) Is data available for each Olympics every 4 years? (b) Construct a line graph of the times for the men s 400 m freestyle over these years. Take into account your answer to part (a). (c) Use your graph to estimate the winning time for this event in the 1956 Melbourne Olympic games. (d) Discuss how the winning times have changed over the 112-year period. (e) Suggest some reasons for the change in winning times. (f) Discuss how you believe the times for the men s 400 m freestyle might change over the next 40 years. 14 The affinity diagram below organises some of the ideas used by scientists into four groups. Each category name is a single word and represents an important part of scientific investigations. However, the category names have been jumbled up. What are the correct categories for groups A, B, C and D? (See page 516 in chapter 20 to learn how to use affinity diagrams.) Scientific investigation Group A Observation Educated guess

Not certain

Prediction

Sensible

Group C Hypothesis

34

15 Construct a storyboard that tells the story of the main events in the life of one of these famous scientists. (See pages 518 19 to learn how to use storyboards.) (a) Albert Einstein (b) Sir Isaac Newton (c) Marie Curie (d) Louis Pasteur

Group B Conclusion Seeing

Tasting

Hearing

Feeling

Smelling

Noticing

Group D Measurement

Beam balance

Ruler

Outcome

Findings

Thermometer

Stopwatch

Final

Fairly certain

Core Science | Stage 4 Complete course

2 Some important steps in using a Bunsen burner are listed below but the sequence is incorrect. 1. Light a match and hold it over the barrel. 2. Adjust the flame by moving the collar until the air hole is open. 3. Connect the rubber hose to the gas tap. 4. Turn on the gas tap and a yellow flame will appear. 5. Close the air hole of the Bunsen burner collar. The correct sequence is A 3, 5, 4, 1, 2. B 3, 5, 1, 4, 2. C 5, 3, 4, 1, 2. (1 mark) D 1, 3, 5, 4, 2. 3 Equipment used for measuring the volume of liquids includes A conical flask, beaker, measuring cylinder. B measuring cylinder, crucible, beaker. C watchglass, filter funnel, conical flask. (1 mark) D evaporating basin, test tube, beaker. 4 A thermometer scale is shown at right. The temperature indicated is A 26 C B 24.4 C C 24.2 C (1 mark) D 24.5 C 5 Luke was sick and tired of being bitten by mosquitoes. He counted several bites each evening when he sat outside to have dinner. He had heard that a burning citronella candle was a good way to keep mosquitoes away. Design an experiment to test Luke s idea. Identify the independent and dependent variables and the controlled variables needed to make this a fair test. Suggest a control for (6 marks) your experiment. work sheets

1.8 Investigations puzzle 1.9 Investigations summary

24

23

22

StUDY CHeCKLISt

ICt

The laboratory

eBook plus

■ outline some of the branches of science 1.1 ■ identify the appropriate equipment to perform an

SUMMaRY

eLessons

investigation 1.2 ■ use appropriate units for measured quantities 1.3 ■ describe ways to reduce the risk to yourself and others when working in the laboratory 1.2

investigating

Career spotlight: scientist In this video lesson, you will meet marine biologist Jodie Haig and learn what it takes to be a scientist working in the marine environment. With insight into her work in the lab and in the field, you will get some useful advice to help you decide if this could be an attractive career for you.

■ use a range of equipment, including data loggers, for collecting data

1.3

■ make and record observations and measurements accurately over a number of trials

1.3

■ use diagrams to present information clearly 1.4 ■ organise and present data clearly using tables 1.4 ■ select and construct the appropriate type of graph (column graph, sector or line graph) to convey information and relationships clearly 1.4 ■ extract information from a variety of graph types, including column graph, pie chart and line graph 1.4

Designing investigations ■ make inferences and testable hypotheses in light of ■ ■ ■ ■ ■ ■ ■

observations made 1.3 describe a logical procedure for undertaking a controlled experiment 1.4 identify the dependent and independent variables when planning controlled experiments 1.5 identify variables that need to be held constant if reliable first-hand data is to be collected 1.5 check the reliability of gathered data and information by comparing them with other observations or data 1.5 identify trends, patterns and contradictions in data collected 1.4, 1.5 identify data that supports or discounts a hypothesis 1.5 make conclusions from experimental results, and base predictions on those conclusions 1.5

Searchlight ID: eles-0053

interactivities Using equipment In this interactivity, you are given a number of scientific processes and you must indicate which equipment from a selection of items commonly found within a laboratory you would use to complete the processes. Instant feedback is provided.

History of science ■ describe historical cases where developments in science have led to the development of new technologies

1.6

nature and practice of science ■ use examples to show how scientists make observations, identify trends and patterns and construct hypotheses 1.5, 1.6 ■ apply scientific processes to test hypotheses 1.5

current issues, research and developments in science ■ identify scientific skills that can be useful in a range of careers

1.1

■ identify possible career paths in science 1.1

Searchlight ID: int-0200 Reading scales This interactivity challenges your knowledge of scales by testing your skill in identifying temperatures on a number of different thermometers. Instant feedback is provided. Searchlight ID: int-0201

1 Investigating 35

2

States of matter

All substances on Earth can be grouped as solids, liquids or gases. By comparing the properties of solids, liquids and gases, you can begin to answer questions like what are substances made of? This question has fascinated people for thousands of years, and scientists are still looking for more answers to that same question.

In this chapter, students will: 2.1 ◗ investigate the nature of matter and

look at the properties of the different states of matter 2.2 ◗ explore the processes by which

substances change state 2.3 ◗ use the particle model of matter to

understand the behaviour of the different states of matter 2.4 ◗ use the particle model to show the

interaction of particles and energy when substances change state 2.5 ◗ use an equation to calculate density

and explain why some substances sink in water while others float 2.6 ◗ observe how heating and cooling of

substances causes expansion and contraction 2.7 ◗ learn how the expansion of gases

affects the pressure of the gas 2.8 ◗ discuss the continuing research into

other states of matter.

Water is the only substance found in three different states at normal air temperatures. It exists as a liquid in oceans, lakes and rivers, as solid icebergs in the oceans, and as water vapour in the air. Without it, plants and animals could not exist. Each of the forms of water has its own different properties and uses.

ranking substances

bathroom science

1. In small groups, rank the following substances in order from most solid-like to most liquid-like to most gas-like. a brick steam jelly plasticine sugar tomato sauce Vegemite air orange cordial green slime

1. Why does the mirror fog up in the bathroom after someone has had a hot shower? 2. On really hot days, you may have a cold shower to cool down. Does the bathroom mirror fog up when you do this? 3. Some showers have shower curtains rather than glass shower screens. When people have warm showers, the curtain tends to move in towards the person in the shower and stick to them it s almost as if the shower curtain is chasing them! Give possible explanations for why this happens. 4. When you have a hot shower, the bathroom fills with steam. Is this steam a gas or a liquid or both? Explain your reasoning.

Green slime

is it solid or liquid? How do you know?

2. Compare your rankings with those of other groups. Comment on any differences between the rankings. 3. Which substances were most difficult to classify as solid, liquid or gas? Explain why they were difficult to classify. 4. Draw a three-column table, like the one below, and separate the substances into three categories solid, liquid or gas. Solid

Liquid

Gas

What is steam

a gas, a liquid, or both?

5. How hot does water have to be before it can burn you? 6. Does steam always rise? 7. Are water vapour and steam the same thing?

2.1

What s the matter? Everything in the universe is made up of matter that can be found in a variety of different forms. The main forms (or states) of matter that we encounter are solids, liquids and gases. These states of matter have very different properties in the way that they behave and the way that they appear. The amount of matter that there is in an object is called the mass of the object. Mass is generally measured in either grams (g) or kilograms (kg).

The states of matter Water is the only material on Earth that can be found naturally in all three states at normal temperatures. Solid water (ice), liquid water and water in the form of gas (called

water vapour) are all made of the same kinds of particles, but they look very different, don t they?

solids Solids such as ice have a very definite shape that cannot easily be changed. They take up a fixed amount of space and are generally not able to be compressed; that is, they cannot be squeezed so that they have less volume. Most solids cannot be poured, but there are some, such as salt, sand and sugar, that can be poured.

Liquids Water is a liquid and its shape changes to that of the container in which it is kept. Like solids, liquids take up a fixed amount of space.

at the end of the syringe and press down on the plunger.

InveStIgatIon 2.1 comparing solids, liquids and gases You will need: ice cube spatula beaker of water

plastic syringe balloon

◗ Pick up an ice cube and place it on

the bench. Using a spatula, try to squash it or compress it to make it smaller. ◗ Take the beaker of water and draw

up a small amount into the syringe. Place your finger over the opening

◗ Partially inflate a balloon with

air and hold the opening tightly closed. Try to squeeze the balloon.

38

State of substance Solid Liquid Gas

Gases Gases spread out and will not stay in a container unless it has a lid. Gases move around, taking up all of the available space. This movement is called diffusion. In the illustration below, iodine gas is being formed and is spreading, or diffusing, throughout the gas jar.

of the balloon.

DIscussIon 1

Copy the table below and use your observations to complete it.

2

Where did the air in the balloon go when you released the opening?

Can the shape be changed easily?

Core Science | Stage 4 Complete course

If a liquid is poured into a glass, it will take up the shape of the glass. If you continue to pour, it will eventually overflow onto the bench or floor.

◗ Release your hold on the opening

Properties of solids, liquids and gases Substance Ice Water Air

While we generally refer to only the three states of matter that are most usually encountered naturally on earth solid, liquid and gas scientists have actually defined other states that matter in the universe may be found in. These include plasma, superfluid, super-solid, degenerate matter, strange matter and bose einstein condensate (bec).

Does it take up space?

Can it be compressed?

The purple iodine gas diffuses, taking up all of the available space. What will happen to the gas if the lid is removed?

Gases, unlike solids and liquids, can be compressed, making them take up less space. An inflated balloon can be compressed by squeezing it.

How much space? The amount of space taken up by a solid, liquid or gas is called its volume. The volume of solids and some other substances is measured in cubic metres (m3) or cubic centimetres (cm3). A volume of one cubic centimetre (1 cm3) occupies as much space as the cube below. The same amount of space is occupied by one millilitre (1 mL) of a fluid. Any substance that flows is a fluid. 1 cm 1 cm

This cube has a volume of 3 1 cm 1 cm and can hold 1 mL of a fluid.

All liquids and gases are fluids. Their volume is usually measured in units of litres (L) or millilitres (mL). In a laboratory, volume is usually measured with a measuring cylinder.

InveStIgatIon 2.2 Volume is 52 mL.

Measuring the volume of an irregular shaped solid You will need: 100 mL beaker 100 mL measuring cylinder stone or pebble that will fit into the measuring cylinder ◗ Half-fill (approximately) a 100 mL

beaker with water. ◗ Carefully pour the water into the

Meniscus

50 Reading the volume of a liquid in a measuring cylinder. The curved upper surface is called the meniscus. Your eye should be level with the flat part in the centre of the meniscus.

measuring cylinder. ◗ Read and record the volume of

water in the measuring cylinder using the technique shown in the diagram above. ◗ Carefully place the pebble into

the measuring cylinder. Take care not to spill any water out of the measuring cylinder. ◗ Read and record the new

volume.

activities reMeMber 1 Identify as many as you can remember of the solids, liquids and gases you came in contact with before leaving for school today. Organise them into a table under headings Solids , Liquids and Gases , or into a cluster, mind or concept map. 2 (a) recall three properties that most solids have in common. (b) Would liquids have the same three properties? If not, describe the differences that might be expected. 3 compare the properties of gases and liquids. 4 recall which unit is used for measuring small volumes such as that of liquid medicines. explain how you could measure such a volume.

THInK 5 Both steel and chalk are solids. Describe the properties of steel that make it more useful than chalk for building bridges. 6 Are plasticine and playdough solids or liquids? explain why.

DIscussIon 1

What was the volume of the solid in millilitres (mL)?

2

What was the volume of the solid in cubic centimetres (cm3)?

3

Suggest another method of measuring the volume of the solid object.

7 Define the term diffusion . Give two examples of this occurring around your house. 8 Is it possible for a solid to behave like a fluid? explain your answer. 9 At the petrol station, the safety sign asks for the car engine to be switched off before you fill the petrol tank. explain why this is necessary.

IMaGIne 10 You are designing a new type of armchair. It needs to be comfortable and capable of fitting in different positions or spaces around the room. Describe the properties you would want in the chair. Would you need to develop a new material to match these properties? If so, explain whether it would be a solid or a liquid, or perhaps a combination of states.

InVesTIGaTe 11 Different liquids pour or flow in different ways. Test this by pouring honey, shampoo, cooking oil and water from one container to another. Time how long they take to pour. Make sure it is a fair test. Record the results in a table and write a conclusion based on your observations and results.

2 States of matter

39

2.2

Changing states Many substances are usually found in one state of matter rather than another. For example, we are more likely to see table salt in its solid form rather than as a liquid or a gas, and we encounter gaseous oxygen a lot more often than we do solid oxygen. However, this does not mean that the state of a substance must remain the same all the time. Most substances can be changed from one state of matter to another by either heating or cooling. Each of these

changes has a particular term to describe it. Let s look at the changes of state that water undergoes when it is heated and cooled. Some substances change from gas to solid or from solid to gas without first turning into a liquid. This unusual change of state is called sublimation. Iodine, diamond and dry ice (solid carbon dioxide) sublimate. Dry ice sublimates at a temperature of 78.5 C. Diamonds sublimate at 3550 C.

Melting The change of state from solid to liquid is called melting. A solid melts when heat is transferred to it. The melting point of water is 0 C.

Freezing The change of state from a liquid to a solid is called freezing. A liquid turns into a solid when heat is transferred away from it. Water freezes at 0 C.

40

Core Science | Stage 4 Complete course

Evaporating Evaporation occurs when a liquid changes to a gas. When water evaporates at temperatures less than 100 C, it forms water vapour. When it evaporates at temperatures greater than 100 C, it forms steam. Water vapour and steam cannot be seen.

Condensing Condensation is the opposite of evaporation. If a gas comes into contact with a cold surface, it can turn into a liquid.

Boiling During boiling, the change from liquid to gas (evaporation) happens quickly. The change is so fast that bubbles form in the liquid as the gas rises through it and escapes. During boiling, the entire substance is heated. A liquid remains at its boiling point until it has all turned into a gas. The boiling point of water is 100 C.

◗ Light the Bunsen burner and begin

InveStIgatIon 2.3

heating the ice cubes. Record the temperature each minute. Continue heating while the ice melts into water and while the water heats up. Stop when the temperature remains steady for three minutes.

observing changes of state You will need: Bunsen burner, heatproof mat and matches tripod and gauze mat thermometer ( 10 to 110 C) watch (with a second hand) spoon 100 mL beaker ice cubes safety glasses

◗ Hold the spoon in the vapour

above the water and observe the effect. CAUTION Take care not to scald yourself with the hot water vapour.

◗ Copy the table below into your

workbook.

DIscussIon

◗ Place four ice cubes (about 50 mL)

in the beaker. ◗ Place the beaker containing the

ice cubes on a gauze mat and tripod. ◗ Place the thermometer into the

ice cubes and let it remain for a minute or so until the temperature stops changing. Take a reading and record this in your table under 0 minutes . At a concert, the thick smoke that is often used for effect is produced by dry ice as it changes state from solid directly to a gas (sublimation). The smoke is actually tiny droplets of water that condense from the air as the cold dry ice sublimates.

1

At what temperature was all the ice melted?

2

At what temperature did the liquid begin to bubble?

3

At what temperature did it boil?

4

What happened when the cold spoon was placed near the vapour?

5

What do you think was in the bubbles?

Heating water Time (minutes) Temperature ( C )

Melting point and boiling point The state of matter of a substance depends on what temperature it is at, and how this temperature compares with its melting point and its boiling point. The melting point is the temperature at which a solid substance turns into a liquid (melts) or a liquid turns into a solid (freezes). The melting point of water is 0 C, so water needs to be cooled to this temperature

0

1

2

3

4

5

6

7

8

9

10

to turn it into ice. If you want to turn ice into water, you need to heat the ice until it is at 0 C. At the other end of the scale, the boiling point of a substance is the temperature at which it turns from a liquid to a gas quickly (boils) or turns from a gas into a liquid (condenses). The boiling point of water is 100 C. The melting points and boiling points of substances can differ quite a lot as you can see in the table below.

Melting and boiling points of some common substances at sea level Substance Melting and boiling points change with the height above sea level. This is because the air gets thinner as you move away from the earth s surface. If you were climbing Mount everest and made a cup of coffee, you would find that the water would boil at about 70 c.

Water

Melting point ( C)

Boiling point ( C)

0

100

804

1413

1535

2750

660

1800

Oxygen

–218

–183

Nitrogen

–210

–196

Table salt Iron Aluminium

2 States of matter

41

Bosshead

InveStIgatIon 2.4 changing the boiling point of water

Thermometer

◗ After 10 minutes, turn off the

Retort stand

You will need: water Bunsen burner safety glasses 2 × 250 mL beakers heatproof mat thermometer salt matches retort stand sugar tripod bosshead and clamp vinegar gauze mat teaspoon 100 mL measuring cylinder

Bunsen burner and allow the equipment to cool.

Beaker Gauze mat Tripod

of water with two teaspoons of salt stirred in, then 100 mL of water with two teaspoons of sugar stirred in, and lastly with 80 mL of water with 20 mL of vinegar stirred in.

DIscussIon Heatproof mat

1

Draw a line graph of your results. Use a different coloured line for each water mixture. Plot time on the horizontal axis and temperature on the vertical axis.

2

How can you tell when the water has reached its boiling point?

3

Is there any part of the graph that shows that the liquid has reached its boiling point?

4

What effect does adding substances to the water have on its boiling point?

5

What would happen to the temperature of each water sample if you continued to heat it past the 10-minute mark?

◗ Measure 100 mL of water with the

measuring cylinder and pour it into the beaker. ◗ Measure the starting temperature

of the water (time = 0 min).

◗ Set up the equipment as shown

◗ Light the Bunsen burner and place

above. Put on your safety glasses.

it under the beaker. Measure the Time (min)

0

◗ Repeat the steps above with 100 mL

Bunsen burner

Matches

◗ Copy the following table.

Water mixture

temperature of the water every minute for 10 minutes. Record your observations in the table.

Clamp

1

2

3

4

5

6

7

8

9

10

Tap water Salt water Sugar water Vinegar water

activities reMeMber 1 Copy and complete the diagram on the right, identifying the changes of state. 2 recall the name given to the change of state from liquid water to steam. Describe how this happens. 3 explain what happens to liquid water when it is cooled below 0 C. Has heat moved into or out of the liquid?

anaLYse 4 Use the table at the bottom of the previous page to answer these questions. (a) Identify the temperature at which you would expect table salt to melt.

42

Core Science | Stage 4 Complete course

(b) Identify the temperature at which it would freeze. 5 Would you expect aluminium to be found as a solid, liquid or gas at: (a) 200 C (b) 680 C (c) 1900 C?

?

6 Identify which substance oxygen or nitrogen would freeze first if the temperature were gradually lowered.

? ?

THInK 7 explain why dry ice is useful to produce a smoke effect. What other uses are there for dry ice? 8 explain why solid blocks of air freshener disappear without a trace after a few weeks. 9 Identify what is in the bubbles that you see when water is boiling.

LI UID

S LID

GAS

Changes of state

work sheet

LI UID

? 2.1 Boiling liquids

2.3

the particle model How do you explain why ice has properties that are different from those of water or steam? Scientists use a model to explain the different properties of solids, liquids and gases. This model is called the particle model. According to the particle model: • all substances are made up of tiny particles • the particles are attracted towards other surrounding particles • the particles are always moving • the hotter the substance is, the faster the particles move.

Liquid

Gas

Solid

A particle model for different states

Particles in a gas The forces between the particles in a gas are very weak. The particles are in constant motion. This means that gases have no fixed shape or volume. There are large spaces between the particles. The spaces allow the gas to be compressed. A gas can flow and diffuse easily since its particles are always moving. Particles in a gas have much more energy than particles in a solid or liquid. They move around and collide with other particles and the walls of the container they are in.

Particles in a solid Solids cannot be compressed because the particles inside them are held closely together. There is no space between them. Bonds also hold the particles tightly together in a rigid crystal-like structure. This gives solids their fixed shape and constant volume. The particles in solids cannot move freely; they vibrate in a fixed position. This means that solids are unable to flow.

Particles in a liquid The particles in a liquid are close together, so there is no room for compression between them. The particles are also held tightly by bonds, but not in the same rigid structure as solids. This gives liquids their fixed volume, but allows the particles to roll over each other. This rolling allows liquids to flow. The movement of the particles explains why liquids take the shape of their container. The particles roll over each other until they fill the bottom of the container.

2 States of matter

43

Getting into shape

Diffusion

In solids, the particles are very close together, so they cannot be compressed. The attraction between neighbouring particles in a solid is usually strong. Because there are strong attractions between the particles, solids usually have a fixed shape. In liquids, the particles are held together by attraction, but it is not as strong as the attraction found in solids. The weak particle attraction allows the particles to move past one another so they can be rearranged and take a different shape. As in solids, the particles in liquids are still very close together, so they cannot be compressed into smaller spaces.

Diffusion is the spreading of one substance through another. The spreading occurs because the particles of each substance become mixed together. The movement of the particles in liquids and gases makes diffusion possible. As the particles in a gas move faster than in liquids, diffusion happens faster in Much later a gas. Particles are not free to move in a solid, so diffusion cannot occur at all.

A little later

At time 0 The spreading starts in an area where there is a concentration of one of the substances. The particles keep mixing through until they are evenly spread through each other. The same number of marbles poured into two different shaped containers shows what happens to particles in a liquid.

InveStIgatIon 2.5

Air deodoriser

Hold straw

DIscussIon Crystal

Investigating diffusion You will need: 500 mL beaker water straw potassium permanganate crystals fragrant spray protective mat safety glasses

44

Core Science | Stage 4 Complete course

Draw a diagram of the movement of the potassium permanganate through the water.

2

How do you think the fragrant spray moved through the air?

3

This experiment shows diffusion in a liquid (water) and diffusion in a gas (air).

Water Beaker

(a) Which state diffuses faster liquid or gas?

◗ Using the straw as a guide, put a

crystal of potassium permanganate in the bottom of a beaker of water. Remove the straw and record your observations.

1

◗ Release some of the fragrant

spray in one corner of the classroom. Move away and observe by smell.

(b) Why do you think this is?

10 Describe what happens to the particles in a gas when it becomes a liquid. recall what this change of state is called.

activities reMeMber 1 recall the basis of the particle model. 2 Define the term diffusion . 3 Give an everyday example of diffusion at work. 4 Copy and complete the table below. Property

Solid

Liquid

Gas

Particle arrangement

11 Use the particle model to explain why: (a) perfume can be smelled from a few metres away (b) steam can be compressed while ice cannot (c) an ice cube melts and changes shape when it is taken out of the freezer (d) water vapour takes up more space than the same amount of liquid (e) solids do not mix well, but gases and liquids mix easily in most cases. 12 explain why wet clothes dry more quickly on a windy day than on a still day.

Force of attraction between particles Movement of particles Ability to diffuse 5 The following statements are incorrect. Rewrite them correctly. (a) To change a liquid to a solid you have to heat it. (b) Heating a liquid might make the particles stick closer together. (c) Solids do not have a definite shape because the particles are free to move around. (d) You can compress a gas because its particles are close together.

THInK 6 explain why solids have a fixed shape.

13 The concept map below represents some of our knowledge about the states of matter. This concept map is just one way of representing ideas about matter and how they are linked. However, all but one of the key terms in the ellipses are missing. Copy the concept map and complete it by writing in suitable keywords in the ellipses. Select the keywords from the list below. One keyword is used three times. fill space fixed shape free gas

liquid particles pour

sliding solid vibrating

eBook plus

7 explain why gases can be compressed. 8 explain why gases fill their containers. 9 When you pour cordial into water, the two liquids slowly mix together even though you don t stir them. explain how this happens. Matter

work sheet

2.2 States of matter

that is made up of is m

ade

that a

re

up o

f

is

ma

de u

po

f

that

14 Use the Phases of matter in containers weblink in your eBookPLUS to watch how solids, liquids and gases behave differently within a container.

th at

so und can o r a you is k

a

is kno

melt

now na

s

evaporate

wn as

freeze

is known as

up a

d

ake nd t

an

are

ve mo

that

to

that are

condense

2 States of matter

45

2.4

Change of state and the particle model Imagine a very cold day. On days like this, you probably sit inside without moving around too much. As the weather gets warmer, you start to move around a little more. On warm, sunny days, you probably have a lot more energy. On these days, you might feel like moving about more. Much like you, the particles inside matter also change the way they move when they are heated or cooled.

Solid When a solid is heated, its particles start to move more quickly. The increased movement of its particles makes the solid expand.

Gas As in solids and liquids, the particles in gases move faster and faster when they are heated. The increased movement of the particles means that they take up more space and the gas expands. If the gas is heated in a closed container, the increased movement of the particles means that they collide more often with the sides of the container and with each other.

46

Core Science | Stage 4 Complete course

changing state A change of state involves the heating or cooling of matter. As a substance is heated, energy is transferred to it. When a substance cools, energy moves away from it to another substance or to the environment. The change in energy causes the particles in the substance to move at different speeds.

Melting As more heat is transferred to the solid, its particles vibrate more violently. Eventually the particles move so much that the bonds holding them in their fixed positions break. The particles start to roll over each other. Melting continues until the entire solid becomes a liquid.

Liquid As a liquid is heated, its particles move and roll over each other faster and faster. The liquid begins to expand.

Boiling If the liquid continues to be heated, the particles will eventually have enough energy to break the bonds holding them together. The particles can break away from the liquid and begin to move around freely. This process is called boiling. Boiling continues until the entire liquid becomes a gas.

foggy mirrors Have you noticed how the mirror in the bathroom fogs up after a hot shower? The fog is actually formed when water vapour that evaporates from the hot water cools down.

Invisible gas Water vapour forms when particles in the hot water gain enough energy to escape and become a gas. You can t see water vapour. The particles in the water vapour move around freely. They have more energy than the particles in the liquid water.

Fog in the air Some of the energy of the particles in the water vapour is transferred away from the vapour to the air. The transfer of energy leaves the water vapour with less energy so much less energy that its particles slow down. The transfer of energy away from the water vapour means it cools down and turns into tiny droplets of water. These tiny droplets form clouds. This process is called condensation.

Fog on the mirror The energy from some of the water vapour is transferred to the cold mirror. This causes the water vapour to condense on the mirror.

activities reMeMber 1 Describe what happens to the movement of particles as a substance changes from a solid to a liquid. 2 Describe what happens to the movement of particles as a substance changes from a gas to a liquid. 3 recall why substances often expand when they are heated.

THInK

6 For each of the following changes of state of a substance, identify whether it involves adding energy to the particles or transferring energy away from the particles. (a) Melting (b) Condensation (c) Boiling (d) Freezing (e) Sublimation (f) Evaporation eBook plus

4 In movies, you sometimes see a mirror being held up to the mouth and nose of someone who is unconscious to check if they are breathing. explain why this would work.

7 Simulate heating matter over a Bunsen burner by using the Changes of state interactivity in your eBookPLUS. int-0222

5 recall the relationship between the amount of energy the particles in a substance have and the state (phase) of the substance.

work sheet

2.3 Changes of state

2 States of matter

47

2.5

Density If you had a 1 kg bag of feathers and a 1 kg bar of lead, which do you think would take up more room? The bag of feathers and the bar of lead have the same mass, which means that they are made up of the same amount of matter. However, while a kilogram of lead may fit on your hand, you d be ankle deep in the same mass of feathers! So why do they have such different volumes if they have the same amount of matter in them?

Kg

calculating density You can determine the density of an object by dividing its mass by its volume: density =

mass volume

The units that we use for the density of an object depend on the units used for its mass and for its volume. • If the mass is in grams (g) and the volume is in cubic centimetres (cm3), the density is measured in g/cm3. • If the mass is in kilograms (kg) and the volume is in cubic metres (m3), the density is measured in kg/m3. You may also see density for fluids given in g/mL, where the fluid s mass has been measured in grams and the fluid s volume in mL.

example A piece of steel has a volume of 12 cm3 and a mass of 91.2 grams. What is the density of steel?

How can objects with such different volumes have the same amount of matter?

The answer has to do with how closely packed together the particles in the lead and the feathers are compared with their size. This quantity is referred to as density. The denser a material is, the more closely packed together its particles are. Different materials have different densities. The densities of some common materials are shown in the table below. Material

Density (g/cm3)

Gold

19.3

Copper

8.96

Diamond

3.52

Window glass

2.8

Water

1.00

Vegetable oil

0.92

Methylated spirits

0.8

Air*

0.001 2

Helium*

0.000 18

*At standard atmospheric pressure

48

Core Science | Stage 4 Complete course

mass volume 91.2 = 12 = 7.6

Density of steel =

As the mass was given in grams and the volume in cm3, the density is in g/cm3. So, we say that the density of steel is 7.6 g/cm3.

sinking and floating In general, objects float in fluids that have a higher density than they do, and they sink in fluids that have a lower density. For example, corks have a density of 0.24 g/cm3, while water has a density of 1 g/cm3. Therefore, as corks are less dense, they float on the water. A lump of copper with a density of 8.96 g/cm3 sinks in water.

Cork

Rock

The cork is less dense than water so it floats. Why does the rock sink?

Fluids can float on top of other fluids, with the less dense fluid on the top. Oil is less dense than water. This is why oil spilled from wrecked tankers floats on the top of the ocean.

◗ Let the test tubes and the beaker

InveStIgatIon 2.6

sit undisturbed for 30 minutes.

sinking and floating DIscussIon

You will need: 250 mL beaker 3 test tubes test-tube rack 20 mL measuring cylinder brown vinegar water olive oil honey ◗ Pour 20 mL each of vinegar, olive

1

How could you tell if a particular liquid was less dense or more dense than water?

2

Which of the liquids were denser than water?

3

Which of the liquids were less dense than water?

4

Draw a labelled diagram showing the order of the layers formed in the beaker.

5

Based on what you saw in the beaker, which was the:

oil and honey into separate test tubes. ◗ Add 20 mL of water to each test

tube. ◗ Pour 20 mL each of vinegar, olive

Cooking oil is less dense than water so it floats on top.

oil and honey into the beaker.

activities reMeMber 1 Identify what the units of density would be if: (a) mass is in kilograms and volume is in cubic metres (b) mass is in grams and volume is in millimetres (c) volume is in cubic centimetres and mass is in kilograms. (Note: This density unit is usually used only with extremely dense objects such as neutron stars!)

(a) densest liquid (b) least dense liquid?

caLcuLaTe 8 Use the density equation on the previous page to calculate the missing values in the following table. Mass (g) 10

Volume (cm3)

Density (g/cm3)

5 40

600

0.5 15

9 explain why this ship is sinking in the water when the boats in the background of the photo are still afloat.

2 If you take a bottle of salad dressing out of the fridge, you may notice that the oil and the vinegar have separated into different layers. explain why this occurs.

THInK 3 explain why most people float in water. 4 explain why balloons filled with helium float upwards. 5 Describe the general relationship you notice between a substance s state of matter and its density. (Use the table of densities on the previous page as a guide.) 6 Equal amounts of vegetable oil, water and methylated spirits are poured into a jar. Identify which liquid will form: (a) the top layer (b) the lowest layer. 7 When divers breathe out under water, the air bubbles head straight to the surface. Deduce why this happens.

eBook plus

10 Select liquids and solids in the Density interactivity in your eBookPLUS and see what sinks and what floats. int-0221 work sheets

2.4 Density 2.5 Density and flotation

2 States of matter

49

2.6

expansion and contraction The particle model can be used to explain changes in the size of substances as well as changes in state. When a substance is heated, the particles move faster, becoming further apart and taking up more space. The substance expands. The tyres on a moving car get quite hot. This makes the air inside expand. This may even cause a blowout in extreme circumstances. Gases usually expand much more than solids or liquids. Gases expand easily because the particles are spread out and not attracted to each other strongly. Solids, liquids and gases contract when they are cooled again because the particles slow down, need less space to move in and become more strongly attracted to each other.

Th These hhot-air t i bballoons ll rise i when h th the air i inside them expands. How do they get back down to the ground?

50

Core Science | Stage 4 Complete course

Architects and engineers allow for expansion and contraction of materials when designing bridges and buildings. Bridges have gaps at each end of large sections so that in hot weather, when the metal and concrete expand, they do not buckle. Railway lines also have gaps to allow for expansion in hot weather. Electrical wires are hung from poles loosely so that, when the weather cools, they do not become too tight and break as they contract. The amount by which each structure will expand or contract depends on the material it is made from; so, when choosing a material for a special purpose, it is important to find out how much that material will expand or contract. The table on the next page shows how much some commonly used materials expand when the temperature increases by 10 C.

On the other hand, alcohol boils at 79 C so it cannot be used for measuring higher temperatures. The temperature of the human body ranges between 34 C and 42 C; it is normally about 37 C. A clinical thermometer is especially designed to measure human body temperature.

InveStIgatIon 2.7 expansion of solids You will need: metal ball and ring set Bunsen burner heatproof mat tongs

Metal ball

Metal ring

Thermometers

A ball and ring set

Liquids expand more than solids. This property makes them useful to use in thermometers. Most thermometers consist of thin tubes, and a bulb that contains a liquid. As the temperature rises, the liquid expands, moving up the tube. In a expands thermometer, the tube is sealed at thermometer the top. The two most commonly used liquids for thermometers are mercury and alcohol. Mercury has a low freezing point ( 39 C) and a high boiling point (357 C). Alcohol, however, is much more useful in very cold conditions because it does not freeze until the temperature drops to 117 C.

◗ Try to put the ball through the

ring. ◗ Use the Bunsen burner to

heat the ring and use tongs to try to put the ball through it. Take care not to touch the hot metal. ◗ Let the ring cool and try to

put the ball through the ring again.

DIscsussIon 1 What has happened to change the size of the ring? 2 Use the particle model to explain the change that took place in the ring.

Glass tube

InveStIgatIon 2.8 expansion of liquids

water should rise into the glass tube. Mark the level of the liquid in the tube with the marking pen.

Stopper

You will need: 500 mL conical flask narrow glass tube rubber stopper with one hole to fit the tube Bunsen burner heatproof mat and matches tripod gauze mat food colouring eye-dropper marking pen ◗ Use an eye-dropper to put two or

three drops of food colouring in the conical flask and fill it with water right to the top.

◗ Place the flask on the tripod and

Coloured water

gauze mat, light the Bunsen burner and gently heat the liquid.

Gauze mat

◗ After about five minutes of heating,

turn off the Bunsen burner and watch what happens to the level of the liquid in the glass tube.

Tripod Bunsen burner

DIscussIon

◗ Place the stopper in the flask with

the tube fitted. Some coloured

1 When a substance is heated, its temperature increases. Describe what other change might be observed.

8 A jar with the lid jammed on tightly can be hard to open. If hot water is run over the lid, it becomes easier to open. Deduce why.

anaLYse Use the table below to answer questions 5 to 7. 5 If a steel rod of 10 metres in length is heated so that its temperature

Use the particle model to explain why liquids expand.

eBook plus

9 Hot-air balloons have a gas heater connected to them. The pilot can turn the heater on and the balloon will go higher. (a) explain why. (b) Describe how the balloon could be brought lower.

4 Give one reason why overhead electric power lines are not hung tightly.

3

12 explain why icebergs float in Arctic and Antarctic waters. Do you think there is much of the iceberg under the water, or is it mostly above? How could you test out your hypothesis? Design a suitable experiment.

THInK

3 Give two examples of structures that contain gaps to prevent them from buckling in hot weather.

What happens to the level of the liquid while it is cooling down?

11 The mercury thermometer was invented by a German named Gabriel Fahrenheit (1686 1736). A different set of markings is used to scale Fahrenheit thermometers. Investigate the temperatures at which water boils and freezes on this scale.

7 Concrete is often reinforced with steel bars or mesh to make it stronger. explain why steel is a better choice than another metal, such as aluminium or lead.

2 (a) recall what change you would expect to see when hot metal objects are cooling. (b) Why does this happen? explain, using the particle model.

2

InVesTIGaTe

6 explain why Pyrex, rather than soda glass, is used in cooking glassware such as casserole dishes and vision saucepans.

reMeMber

What happens to the level of the liquid while it is being heated?

Investigating the expansion of liquids

rose by 10 C, calculate how long the rod would become.

activities

1

13 All materials expand when heated and contract when cooled, right? Use the Mystery expansion weblink in your eBookPLUS to learn about a substance that breaks all the rules.

10 Under what conditions might you use an alcohol thermometer rather than a mercury thermometer?

work sheet

2.6 Expansion of liquids

Expansion of 100 m length of materials when temperature increases by 10 C Substance Expansion (mm)

Steel 11

Iron Platinum Brass Concrete Glass — soda 12

9

19

11

9

Glass — Pyrex Lead 3

29

Tin 21

Aluminium Bronze 23

18

2 States of matter

51

2.7

Under pressure! The firefighter charged through the doors just in time, pointed the extinguisher at the electrical fire and pressed the trigger. A huge burst of carbon dioxide gas came squirting out of the nozzle, putting out the flames. The carbon dioxide in the story above could be used in this way only because huge amounts of it can be compressed, or squeezed, into a container. Gases can be compressed because there is a lot of space between the particles. Gases compressed into cylinders are used for barbecues, scuba diving, natural gas in cars, and aerosol cans. Hot-air balloons work on the idea that gases expand when heated. The particles in the heated gas move about more and take up more space. This makes each cubic centimetre of hot air in the balloon lighter than each cubic centimetre of air outside the balloon, so it rises, taking the balloon with it.

fighting fire

1. Gases, including carbon dioxide, have lots of space between their particles.

52

Core Science | Stage 4 Complete course

eBook plus

eLesson

Under pressure Learn about the factors that affect the pressure of a gas and how compressed gases are used to make fire extinguishers and aerosol cans. eles-0058

4. When the nozzle is opened, the pressure forces the carbon dioxide gas out very quickly through the opening.

2. The carbon dioxide is compressed into the cylinder. The particles are squashed closer together.

3. The carbon dioxide particles are now under increased pressure. This means that the particles in the gas collide frequently with the walls of the cylinder. The particles push outwards on the walls of the cylinder. The particles are trying to escape, but are held in by the container.

5. The particles of gas quickly spread out over the fire. The gas smothers the fire, stopping oxygen from the air getting to it. Fires cannot burn without oxygen, so the fire goes out.

fizzing drinks All carbonated soft drinks contain carbon dioxide gas. The gas is dissolved in the liquid under high pressure. The gas stays dissolved in the liquid as long as the pressure inside the can is higher than outside the can. When the can is opened, it is de-pressurised and the carbon dioxide starts rising to the surface (because it is less dense than the liquid). In its hurry to escape, the carbon dioxide often pushes the top layer of liquid out as well, causing it to fizz and spill.

Well-known gases There are many gases we use for different purposes. Here are some of the more well-known ones. Famous gas

Use

Property

Neon

Neon lights

Absorbs electrical energy and turns it into light

Helium

Party balloons, blimps

Lighter than air

Methane (in natural gas)

Cooking, heating

Flammable

Argon

Fluorescent lights

Absorbs electrical energy and turns it into light

Ozone

Cleaning water in pools and spas

Highly reactive; kills bacteria

Nitrous oxide (laughing gas)

Anaesthetic

Affects nervous system in humans

InveStIgatIon 2.9 exploring gases You will need: small balloon string ruler large beaker warm water cold water or fridge ◗ Blow up the balloon until it is

firm.

activities reMeMber 1 recall why gases can be compressed. 2 Describe what happens to a gas that is heated. 3 explain how a carbon dioxide fire extinguisher works.

THInK 4 Draw a diagram of a gas before and after heating to show what happens to the particles. 5 explain why aerosol cans have Do not dispose of in fire printed on the can. 6 Infer which would last longer: a scuba diver s tank filled with compressed air or one filled with air at normal pressure.

7 explain what would happen to the pressure in a car tyre after it has been driven on a hot road and then parked on some cool grass.

◗ Measure the circumference

of the balloon with a piece of string and record your results in a table. ◗ Put the balloon in warm water

for 10 minutes and re-measure the circumference.

InVesTIGaTe 8 Many gases, including oxygen, nitrogen, chlorine and hydrogen, have important uses. Choose one of these gases and investigate what it is used for and why. 9 Investigate which gases are found in the air and how much of each gas there is. 10 Many gases in the air are pollutants put there by humans. Investigate the problem one of the following gases causes to the environment. sulfur dioxide, chlorofluorocarbons (CFCs), nitrogen dioxide, ozone work sheet

2.7 Particles in our lives

◗ Put the balloon into the

cold water or a fridge for 10 minutes and measure the circumference of the balloon again.

DIscussIon 1

Did the balloon expand or contract in warm water?

2

Did the balloon expand or contract in the cold water or a fridge?

3

Explain, in terms of particles, what happened when the balloon was heated and cooled.

2 States of matter

53

2.8

prescrIbeD focus area current issues, research and development in science

other states of matter? In the past, scientists believed that everything around us was either a solid, a liquid or a gas. But scientists now believe that there are other states of matter that are not very common on Earth. The earliest of these additional states of matter to be identified is called plasma. It is currently estimated that more than 99 per cent of all matter in the universe is actually plasma. Plasma occurs everywhere. The sun and all the other stars are made of plasma, as is lightning and the aurora australis (also known as the southern lights). Temperatures higher than 1 000 000 C are needed to form

these plasmas. Lightning bolts actually form plasma from the surrounding air. In an ordinary gas, each atom contains an equal number of protons and electrons. (We will learn more about the particles that make up the atom in chapter 11.) This makes each atom neutral. The positively charged protons are surrounded by an equal number of negatively charged electrons. A gas becomes plasma when energy or heat is added. This energy or heat causes the atoms to release all or some of the electrons. This means that the remaining atoms now have fewer electrons and the atoms have

Lightning turns gases in the air into plasma at temperatures higher than 1 000 000 C.

54

Core Science | Stage 4 Complete course

a positive charge. The removed electrons are free to move about. Energy knocks electrons off atoms.

Protons Nucleus Neutrons

Incoming energy removes electrons from gas atoms, changing them into a plasma state.

Plasmas have different properties from gases. For example, oxygen gas is not affected by magnetic fields and cannot conduct electricity. However, if oxygen gas is turned into plasma, it can be contained in a magnetic field and can conduct electricity. Different atoms form different types of plasma. Each type of plasma can be used for different purposes, such as in neon lights and fluorescent tubes. Plasmas are also used in lasers, high-powered microwaves, water purification and some semiconductors in computers.

Fusion technology comes to Earth!

Plasmas are used in lasers.

Test drive the new plasma-powered car. With speeds of up to 5000 km/h it is a ride to die for!

Scientists are currently studying how plasmas could be used to release energy from sea water without creating pollution. A possible solution is, firstly, to use sea water to make hydrogen gas. The atoms of hydrogen gas could then be joined together (fused), a process that releases large amounts of energy. However, this fusion occurs at such high temperatures that there is currently no container on Earth that could hold the plasma without being destroyed. The good news though is that, because plasma is affected by magnetic fields, a special magnetic container may be able to hold the plasma.

See your local plasma dealer today!

activities reMeMber 1 recall an example of naturally occurring plasma. 2 Atoms in solids, liquids and gases are neutral. explain what this means. 3 What happens to the atoms in a gas to make them into plasma? explain this in terms of protons and electrons.

THInK 6 Distinguish between the properties of a plasma and those of a gas. 7 Draw a diagram using particles to demonstrate what happens if a substance changes from a solid to a liquid to a gas to a plasma. 8 explain why scientists think that plasma would be a good energy source in the future.

4 Describe a current use of plasma.

InVesTIGaTe

5 recall some examples of how plasma may be used in the future.

9 Investigate how a neon light works. Present your findings as an advertisement to sell a new neon light.

2 States of matter

55

LooKIng BaCK 1 Use the particle model to explain why steam takes up more space than liquid water.

7 Copy and complete the diagram, labelling the missing state and changes of state.

2 Recall in which state the forces of attraction between the particles are likely to be greatest. 3 Identify in which state particles have: (a) the most energy (b) the least energy.

solid, liquid or gas

?

the

Melting

4 Explain why perfume and aftershave lotion evaporate more quickly than water. Solid

5 Copy and complete the table below to summarise the properties of solids, liquids and gases. Use a tick to indicate which properties each state usually has. Property

Solid

Liquid

Gas

Has a definite shape that is difficult to change

? Gas

Freezing

?

8 Fully explain the process that is occurring in the following diagrams.

Takes up a fixed amount of space Can be poured Takes up all of the space available Can be compressed Is made of particles that are strongly attracted to each other and can’t move past each other

9 Identify which of these diagrams (A, B or C) correctly shows a solid after expanding.

Is made of particles that are not held together by attraction 6 Copy and label the three diagrams below to identify which represent solids, liquids and gases. Make an improvement to each of the diagrams so that they describe the particle model more fully. (a)

(b)

Original solid

(c)

B

A

C

10 (a) Copy the table below and rewrite it to correctly match the substances to their properties and uses. (b) Identify whether the substance would be a solid, liquid or gas. Properties and uses of various substances Name of substance

56

Property

Use

Air

Waterproof, hard, strong

Horseshoe

Tin

Particles able to mix easily with other particles

Balloon

Neon

Particles absorb energy and turn it into light

Sign, light

Oil

Hard, strong

Driveways

Iron

Hard, strong, easily shaped when heated

Lubricant

Concrete

Particles slip past each other

Roofing

Core Science | Stage 4 Complete course

Solid, liquid or gas?

11 Graphite (used in pencils) and diamond are both made of the same type of particle, yet graphite has a density of 1.46 g/cm3 while diamond has a density of 3.52 g/cm3. Give possible explanations for how they can have different densities yet be made of identical particles. 12 A mysterious substance is developed in a laboratory. The sample has a mass of 10 g and has a volume of 2.3 cm3. (a) Calculate its density. (b) What is the mystery substance s most likely state of matter?

TesT YourseLf 1 Compression is a term that describes A squeezing the particles of a substance closer together. B pulling particles further apart. C removing the heat energy from the particles of a substance. D the releasing of air from a car tyre. (1 mark) 2 Ice cubes float in soft drink because A the bubbles in the soft drink hold them up. B the ice is less dense than the soft drink. C the ice is denser than the soft drink. D water and soft drink do not mix.

(1 mark)

3 Gaps are left between sections of railway track so that A more track can easily be laid later. B bugs can cross the railway lines safely. C the steel tracks can expand in cold weather without buckling the track. D the steel tracks can expand in hot weather without buckling the track. (1 mark) 4 According to the particle model, the attractive forces between particles are strongest in A solids. B liquids. C gases. D plasma. (1 mark) 5 Read the information in the box above right. (a) Use the words in bold to label the diagram of the refrigerator below. (2 marks) G

E

C

R

How a refrigerator works Evaporation occurs when a liquid gains enough heat energy to change into a gas. Refrigeration is possible because of this. The pipes in a refrigerator contain a substance called a refrigerant. (A refrigerant is a substance that changes from a liquid to a gas and back again.) Near the expansion device, the refrigerant is in the liquid state. As it passes through the expansion device, the liquid is made to expand (the pressure drops). As a result of the drop in pressure, the refrigerant cools down to a very low temperature. (You may have experienced this cooling effect if you have ever used a fire extinguisher.) The liquid refrigerant then passes through the part of the pipe that is inside the fridge. This part of the pipe is called the evaporator. Heat energy travels from the objects and air inside the fridge to the very cold refrigerant. The inside of the fridge cools down. The liquid refrigerant heats up and turns to gas (evaporates). (Note: Heat energy travels from a hotter to a colder substance.) The refrigerant, which is now a gas, passes into the compressor. This puts the refrigerant under pressure again. Under pressure, the refrigerant becomes even hotter. (You may have experienced this when you pumped up the tyres on your bike. Under increased pressure, the air in the tyres feels warmer.) The compressor pushes the refrigerant into the next part of the pipe, the condenser. The condenser is on the outside of the fridge. Here, heat from the gas is transferred to the air outside the fridge. The air outside the fridge warms up. The refrigerant in the pipe cools down and becomes a liquid again (condenses). The liquid flows back towards the expansion device. The cycle is repeated. (b) Use the information in the box above to construct a flow chart that describes the changes of state that take place during the refrigeration process. Colour each state a different colour. For example, when the refrigerant is in the liquid state, you may choose to colour the relevant section blue. The flow chart has been started for you. (4 marks)

Outside fridge

Inside fridge

Refrigerant is under pressure and in the liquid state.

C

Refrigerant passes through expansion device.

L

L

T

E

D

work sheets

2.8 States of matter puzzles 2.9 States of matter summary

2 States of matter

57

StUDY CHeCKLISt

ICt

states of matter

eBook plus

■ identify the three most common states of matter 2.1 ■ describe the physical properties of solids, liquids and

SUMMaRY

under pressure

gases 2.1 ■ explain what is meant by the term fluid 2.1 ■ explain density in terms of the particle model 2.5 ■ describe the changes in pressure of gases in terms of the increase or decrease of frequency of particle collisions 2.7

In this video lesson, you will see animations that reflect the behaviour of gas particles and learn about the factors that affect the pressure of a gas. You will also learn how compressed gases are used to make fire extinguishers and aerosol cans. A worksheet is attached to further your understanding.

The particle model of matter ■ state the main assumptions of the particle model 2.3 ■ describe the difference in behaviour of particles in solids, liquids and gases.

2.3

■ use the particle model to explain expansion and contraction of materials during heating and cooling

2.6

■ discuss how increasing and decreasing the energy of particles affects their movement

2.3, 2.4

■ describe what happens during the process of diffusion

2.3

changes of state ■ describe the physical changes that occur during observations of evaporation, condensation, boiling, melting and freezing 2.2 ■ relate changes of state to the motion of particles as energy is added or removed 2.4 ■ explain the changing behaviour of particles during changes of state 2.4

Searchlight ID: eles-0058

Interactivities Changes of state This interactivity allows you to simulate heating an ice cube over a Bunsen burner. As you add more heat, you will see the effect on the particles as the ice changes state to become boiling water. A worksheet is attached to further your understanding.

current issues, research and development in science ■ describe the state of matter called plasma 2.8 ■ describe current research on the use of plasma in energy production

2.8

Searchlight ID: int-0222 Density This interactivity helps you to delve into the world of density. Select a liquid to fill your virtual flotation tank, and then choose a solid to release into it. This interactivity will let you discover the combinations that cause your solid to sink and to float. A worksheet is attached to further your understanding. Searchlight ID: int-0221

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Core Science | Stage 4 Complete course

3

Separating mixtures

This mixture of chocolate can be separated easily into different colours. We can make piles of red ones, blue ones and so on. But each pile is not pure chocolate. Each sweet is a mixture of a chocolate centre and a sugary coating. If we separate the centre from the coating, we still won t have pure substances. Chocolate is a mixture of ingredients cocoa, butter, sugar, milk and flavours blended to give a great taste. The sugary coating is a mixture too. Even the colouring can be a combination of many different colours. Chocolate isn t the only substance that can be made by combining different ingredients. Many substances are made this way. And, the individual ingredients in some substances can also be separated further into parts.

In this chapter, students will: 3.1 ◗ distinguish between pure substances

and mixtures and identify some common mixtures 3.2 ◗ learn about solutions and compare

soluble and insoluble substances 3.3 ◗ compare different methods such as

filtering, decanting, centrifuging and using separating funnels to separate insoluble substances from suspensions 3.4 ◗ appreciate the use of separation methods

in preparing blood donations for use 3.5 ◗ use processes such as distillation,

evaporation, crystallisation and chromatography to separate the solutes from the solvents in solutions 3.6 ◗ apply knowledge of separation

techniques to develop an understanding of how sewage is treated 3.7 ◗ examine how water supplies are treated

before reaching a population as drinking water.

Each of these sweets contains a mixture of ingredients including cocoa, butter, sugar, milk, flavours and colours.

3 Separating mixtures Separating mixtures Imagine that a few small iron nails have been dropped into a child s sandpit and have sunk into the sand so that they can t be seen. One way of separating the nails from the sand is to use a magnet. This works because the nails and sand have different properties, or features. The nails are made from a substance Mixture of sand, nails that is attracted to magnets, and plastic beads but the sand is not attracted to magnets. But what if plastic beads had been dropped into the sandpit instead of nails? They can t be separated from the sand with a magnet. The key to separating them is recognising the different properties of the plastic beads and the sand. An obvious difference is size. The plastic beads are much bigger than grains of sand. A child s sand sieve would do the trick. Sand grains pass through but the plastic beads don t. The flow chart above shows one way of separating the parts of a mixture of sand, nails and plastic beads. 1. Suggest another method of separating the nails from the sand. 2. What difference in properties does your suggested method use to separate the substances? Chocolate is a mixture of cocoa, butter, sugar, milk and flavours.

Sand

Mixture of sand and plastic

Plastic beads too large to fall through sieve

Nails attached to magnet

Plastic beads

Nails

3. Draw a flow chart to show a different method of separating the sand, nails and plastic beads from the one shown in the flow chart above.

InveStIgatIon 3.1 Design and separate Your task is to separate the parts of a mixture of matches, pebbles, steel paperclips and sand. You will need: sand (about 250 mL) dead matches small pebbles steel paperclips plastic container (about 500 mL) A3 paper other equipment and water as required ◗ Mix the matches, pebbles and paperclips evenly in a

plastic container of sand. ◗ Devise and write a step-by-step plan of a method to

separate the four parts. You will need to think about the properties of each part of the mixture that will make separation possible. ◗ Make a list of all of the equipment that you will need. ◗ Check your plan with your teacher, and then gather the

equipment and perform the separation. ◗ On A3 paper, draw a flow chart like the one above to

show how each part was separated from the mixture.

3.1

Separating substances Consider the two glasses of orange juice that are shown below. The one on the left is orange juice that has been squeezed fresh from the orange, while the other has come from a carton of orange juice that was bought at the supermarket. They look pretty much the same, don t they?

Mixture

Made up of

Salt water

Water, salt

White coffee

Water, coffee, milk (may have sugar)

Chocolate

Cocoa, milk, sugar, cocoa butter

Cola drink

Water, carbon dioxide, sugar, caramel, colouring agents, flavouring agents

Soil

Silica, iron oxide, organic matter, nitrogen

Bread

Flour, yeast, water, egg, sugar

In most cases, it can be difficult to tell whether a substance is a pure substance or a mixture just by looking at it. This is because the individual particles in the substance are usually too small to see, so it is hard to tell if they all look the same or if there are different types of particles present.

Separating mixtures Now, let s look at the ingredients of the orange juice from the carton. As you can see, the orange juice from the carton seems to contain ingredients other than just orange juice. In fact, it is a mixture.

Substances in our world can generally be classified as being either pure substances or mixtures. A pure substance is made up of the same type of particle throughout. White table sugar that you put on your breakfast cereal, for example, is a pure substance and is made up of nothing except identical particles of sucrose. Pure water, salt, plain flour and methylated spirits are also examples of pure substances. A mixture, on the other hand, is made up of at least two different pure substances, and so it contains several different kinds of particles. Chocolate milk is an example of a mixture, because it is made up of particles of milk, sugar and cocoa. Some other common mixtures are shown in the following table.

Many mixtures can be separated into the basic substances that they are made of. There are a number of different ways of doing this, but all of these methods rely on the fact that the individual substances that make up a mixture have different properties. For example, after you ve cooked pasta, you separate the cooked pasta (solid and in hollow cylinders) from the water (liquid) using a strainer. Water passes easily through the strainer, but the pasta is caught.

If you are doing woodwork and you drop some nails in the sawdust, there are several ways to separate them because their properties are so different.

3 Separating mixtures

61

Recycling plants Most local councils have a recycling program. Items such as paper, all plastic bottles and containers, glass, aluminium and steel can be recycled and made into new products. Recycling reduces the amount of waste that

goes to landfill and saves precious resources such as trees and bushland. Many manufacturing processes pollute the environment. Recycling and reusing materials reduces the need to manufacture from raw materials.

Paper sorting facility All paper and cardboard is manually sorted to ensure that there are no plastic bags or other non-paper items in the mixture. Paper and cardboard is baled and sent to paper mills for reprocessing. At the mill, paper is shredded and mixed with water (pulped) to make new paper products such as cardboard boxes.

Newsprint baler Mixed paper baler

Paper sorting facility

Rubbish

Trommel The trommel is a large rotating cylinder with holes along its sides, similar to the inside of a washing machine. Heavy recyclables, such as plastic, glass, cartons, steel and aluminium, fall through the holes in the trommel, while lightweight material, such as paper and cardboard, continue along the conveyor to be sorted separately.

Air classifier Plastic, aluminium and paper cartons are lighter than glass. A blast of air blows these lighter materials to a separate conveyor belt.

Trommel

Air classifier Plastics optical sorting facility Plastic containers and cartons are sorted using optical sorting technology. A bright light detects each item and sorts it by type using air jets that blow it away from the other materials. Each type of plastic is then baled individually and sent to a plastics reprocessing plant. Cartons are baled and sent to a paper reprocessing plant.

PET baler Mixed plastic baler Carton baler

Green Glass sorting facility

Clear Amber

Fines

62

Eddy current

Aluminium baler Glass sorting facility Glass is sent to processing plants where it is sorted by colour. The glass is then crushed, melted and made into new glass bottles and jars.

Core Science | Stage 4 Complete course

Steel magnet

Eddy current As you may know from playing with fridge magnets, aluminium is not attracted to the same magnets that steel is attracted to. Aluminium cans and foil wrap are sorted from plastic and carton material by the eddy current separator. This machine uses rare earth magnets, which operate in reverse to the steel magnet and actually repel the cans rather than attract them. The cans are repelled over the conveyor belt, baled and sent to a reprocessing plant.

Steel baler

Magnet Steel cans are separated from other containers using a magnet. The steel is collected in a separate container, ready to be sent to steel manufacturers. Material that is not attracted to a magnet continues along the conveyor belt.

Separating by sight Household rubbish is usually a mixture of food scraps, recyclable materials and other waste. The first step in recycling is to separate the recyclable items from other household rubbish. We can see the differences between the types of rubbish, and we know which items can be recycled. Big recycling plants use this knowledge to separate the tonnes of recycled goods they receive. Pre-sort When the mixture of goods arrives at the sorting facility, it is sent along a conveyor belt. Staff sort through the materials by hand to remove any non-recyclable material that they can see in the mixture, such as plastic bags, foam, garden waste and household rubbish.

activities RemembeR 1 Define a mixture. 2 explain why some mixtures are easier to separate than others. 3 How can you distinguish pure substances from mixtures? 4 Recall two reasons why recycling is good for the environment. 5 explain why recyclable materials need to be separated.

Think 6 Describe all the properties you can think of for: (a) salt (b) sand (c) water. 7 explain how you would separate the parts of a mixture of salt, sand and water. Use the properties that you considered in question 6. 8 Imagine you dropped nails in the sawdust in woodwork class. Propose two reliable ways of separating the nails from the sawdust. 9 Construct a table with two columns with the headings Pure substance and Mixture . List the following substances under the appropriate heading: freshly made apple juice, tap water, soft drink, cake batter, sterling silver, distilled water, gold nugget, glass, cornflakes. You may have to research some of these substances to find out which column they belong to. 10 Construct a table like the one below and complete it with information on separating recyclable rubbish. Method

What is removed?

Properties

(a) Record the methods used to separate different types of material in a recycling plant. (b) For each method, record which material is removed from the flow of rubbish. (c) What properties of this material allowed it to be separated from the mixture? 11 Deduce why the same magnets are not used for separating both aluminium and steel cans. 12 explain why people, rather than machines, need to manually separate some of the recycling mixture.

inveSTigaTe 13 How would you separate the sand from a mixture of sand and sawdust? Construct a flow chart to show the steps you would use. Check your method with your teacher before trying out your experiment.

CReaTe 14 Design and construct a poster or brochure that explains which items can be recycled. Check with your local council about how they prefer recycling materials to be separated ready for collection. Include this in your brochure or poster.

3 Separating mixtures

63

3.2

Looking for solutions When you add a teaspoon of sugar to a cup of hot water and stir it, the sugar crystals seem to disappear. Where have they gone? Actually, the sugar is still there; the sugar particles have been separated away from each other and have spread out among the water particles. As the individual particles of sugar are so small, they appear to be invisible to the naked eye. We say that the sugar has dissolved in the hot water and has formed a sugar solution. A solution is a mixture made up of one substance dissolved in another. The substance that is dissolved is called the solute, and this can be a solid, a liquid or even a gas. The substance that the solute is dissolved in is called the solvent; this is usually a liquid. In the case of our sugar and hot water, the sugar is the solute and the water is the solvent. Water is considered to be a very good solvent because many chemicals will dissolve in it quite easily. Solutions in which water is the solvent are said to be aqueous solutions.

pumped into bottles or cans at high pressure. The bottles and cans are then sealed to keep the carbon dioxide dissolved in the solution. When you open the drink, the pressure is reduced and the carbon dioxide bubbles out of solution.

Solute

Solvent

Solution

A solute dissolves in a solvent and creates a solution.

The solute in a solution can be any state of matter. When we dissolve things such as sugar or salt, the solute is a solid. When we add cordial to water, the cordial dissolves in the water; in this case, the solute is in a liquid form. Gases can also be dissolved in solvents. The fizz in fizzy drinks is the carbon dioxide gas that is dissolved in the flavoured liquid. Carbon dioxide is

64

Core Science | Stage 4 Complete course

When the carbon dioxide is dissolved, you can t see that it s there. When you open the container, the pressure is reduced. The carbon dioxide is separated from the mixture and bubbles to the surface.

Soluble or insoluble? Substances that dissolve in a particular solvent are said to be soluble in that solvent. Remember that, just because a substance is soluble in one solvent, doesn t mean that it is soluble in all solvents. For example, waterproof ink (which you will find in permanent markers) is soluble in alcohol but it is not soluble in water. We use the word insoluble when a substance does not dissolve in a particular solvent.

When an insoluble substance is added to a solvent, particles of the undissolved substance cause the solvent to look cloudy. We say that the mixture of the solvent and the undissolved substance form a suspension. Over time, the insoluble substance may sink to the bottom of the solvent to form a layer of sediment. In other cases, the insoluble substance may float on the top of the solvent.

InveStIgatIon 3.2 Soluble or insoluble? Substances that dissolve are said to be soluble. Those that do not are insoluble. This experiment investigates the solubility of some common substances in water. You will need: safety glasses and laboratory coat heatproof mat 7 test tubes test-tube rack spatula samples of salt, sugar, flour, coffee, sand, copper sulfate and copper carbonate

Adding a soluble substance to a liquid Solute dissolves, forming a solution.

Adding an insoluble substance to a liquid

◗ Half-fill each of the test tubes with cold water. ◗ Label the test tubes: salt, sugar, flour, coffee and so on.

An insoluble substance may form a suspension.

◗ Use a spatula to add a very small amount of each substance to its labelled

test tube. Do not use more than a quarter of a spatula full. ◗ Draw up a table of your results like this incomplete one:

Substance mixed with water

Clear or cloudy?

Solution? (yes/no)

Salt Sugar Flour An insoluble substance may float on top of the liquid.

Coffee

◗ Hold each test tube up to the light. Decide whether the mixture is clear or

cloudy. Record your results in the table. ◗ Decide whether each mixture is a solution or a suspension. Record this in

the table.

An insoluble substance may form a sediment.

DiSCuSSion 1

Which of the substances dissolved in water?

2

How can you tell if a substance has dissolved?

3

Read the information on filtration on pages 67 8. Which of the mixtures could be separated by filtration?

Mixing solids with liquids

3 Separating mixtures

65

more mixtures Another type of mixture is a colloid. Particles of one substance are spread evenly throughout another. Substances that form colloids can be solids, liquids or gases. These mixtures are not clear, like solutions, but do not settle to form sediment like suspensions. An emulsion is a special type of colloid. Emulsions are formed when one liquid is spread evenly through another liquid and does not settle in a layer. Fresh pumpkin soup is a colloid. Small bits of pumpkin are spread through water and do not settle in a layer.

activities RemembeR 1 identify a single word that can replace each of the following expressions: (a) Liquid in which a substance dissolves (b) Insoluble particles dispersed in a liquid (c) Substance that dissolves in a liquid (d) What is formed when a solute dissolves in a solvent (e) An insoluble substance that sinks to the bottom 2 Recall which two types of substances mix to form emulsions. 3 identify the solvent, solute and solution in the photo below.

Marshmallows are colloids. They are mixtures of air spread through sugar and other ingredients.

Homogenised milk is an emulsion. It is made from butterfat (oil) spread through water. Both parts of this mixture are liquids.

5 Non-homogenised milk separates into two parts if it is left to stand. But homogenised milk does not settle. It is an emulsion. (a) Deduce what type of mixture is untreated milk. (b) Cream and butter are both made from milk. identify what types of mixtures cream and butter are.

inveSTigaTe 6 Some substances dissolve better in hot water than in cold water. Design an experiment to compare the amount of copper sulfate that can be dissolved in cold tap water and hot tap water.

CLaSSiFY 7 Distinguish which of the following substances are suspensions, solutions, colloids or combinations of these. explain each decision. Muddy water Cup of coffee Mayonnaise Whipped cream Hot chocolate Cup of tea with tea-leaves in it eBook plus

8 Identify a series of liquid mixtures as suspensions, solutions or emulsions by completing the Time Out mixtures interactivity in your eBookPLUS. int-0224

Think 4 Is fog a solution, suspension or colloid? explain your answer.

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work sheet

3.1 Solutions and suspensions

3.3

Separate ways There are a number of ways to separate undissolved substances from a liquid; you use many of these every day. The simplest method of separating a mixture of a liquid and a sediment is called decanting. In this process, the mixture is poured into a container and, once the sediment settles to the bottom, the liquid is carefully poured off the top. You use the decanting method whenever you pour the hot water off cooked vegies for dinner!

eBook plus

eles-0061

Stirring rod

Filtering What do a vacuum cleaner, tea strainer and protective face mask have in common? They are all devices for separating mixtures by filtration. In the laboratory, filtration is done using filter paper, but there are many other useful methods of filtration that are used in the home and in industry. During filtration, solutions or gases pass through the filter but particles that cannot fit through the filter are trapped by it. Insoluble particles can be separated from a solution using filter paper in a funnel as shown on the right.

(a)

eLesson

Centrifuging Watch this video lesson to learn how to separate a solid from a liquid: in this case, lead oxide from water.

Beaker Mixture with insoluble particles

Filter funnel containing folded filter paper

Filtrate

Conical flask

Equipment used to filter a mixture that contains insoluble particles

(b)

(c)

(d)

(a) A face mask filters dust from the air. (b) A car air filter removes dust particles from the air. (c) A vacuum cleaner contains a filter bag that traps the dust as air is sucked through it. (d) A food strainer separates the chips from the oil.

Indigenous Australians combine sieving (a type of filtration) and decanting to prepare native yams, which contain a poison. The yams are boiled and placed into a dilly bag. The bag is squashed and the softer parts of the yam are strained through the bag into a can of water. The bag acts as a sieve, allowing some substances to pass through but not others. The skins and harder parts of the yam that are left in the bag are thrown away. The water is decanted from the can, and repeated washing with water removes more poison. The yam is then placed into another dilly bag and hung up overnight before being ready to eat.

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67

Separating funnel

InveStIgatIon 3.3 Filtration in the laboratory You will need: 100 mL beaker funnel filter paper glass stirring rod conical flask insoluble substance, such as soil, chalk dust, charcoal

When one liquid does not mix with another but floats on top of it, a separating funnel can be used to separate the two liquids. Oil floats on water. This mixture can be separated using a separating funnel as shown below. Separating funnel

◗ Half-fill your 100 mL beaker with water.

Oil

◗ Add your insoluble substance to the water and stir with the stirring rod. ◗ Set up the equipment for filtering as shown in the top diagram on the

Retort stand Water

previous page. ◗ Fold the filter paper as shown in the diagram below.

Tap

◗ Place the filter paper in the funnel and moisten with clean water to hold the

filter paper in place. ◗ Pour your mixture into the filter paper.

Separated water

DiSCuSSion 1

Describe the appearance of your mixture in the beaker before filtration. Did it form a suspension or sediment, or float on top?

2

The liquid passing through the filter into the conical flask is called the filtrate. Describe your filtrate.

3

Examine your filter paper. The material trapped by the filter paper is called the residue. Describe your residue.

4

Filter paper is like a sieve with small holes in it. Explain how the filter paper worked like a sieve in this experiment. First fold

Forming the cone

Folding filter paper

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Second fold

50 mL beaker

Using a separating funnel to separate oil from water

Centrifuging A mixture can be separated by spinning it very quickly. This method is called centrifuging. The spin-dry cycle of a washing machine acts as a centrifuge and a filter. As it spins at high speed, the clothes are forced to the sides of the tub and the water passes out through the holes in the tub. The clothes cannot fit through the holes and so much of the water is removed from them. In the laboratory, centrifuging is used to separate solid or liquid substances from liquids. The mixture is placed in special test tubes that are spun in a circle at high speeds. The heavier substances are forced to the bottom of the tube and the lighter substances are left near the top.

InveStIgatIon 3.4 making billy tea no camping trip would be complete without billy tea. billy tea was traditionally made in a metal can that was heated over a campfire. Then a handful of dry tea-leaves was tossed into the boiling water and left to brew for a few minutes. For extra flavour, early settlers sometimes added gum leaves to the water as it boiled. To make the leaves settle to the bottom, the billy was swung in full circles at arm s length. Three anticlockwise spins and the tea was ready to drink. but they had to be careful. a timid swing or one ending in the wrong spot could result in a hot and painful soaking and no billy tea!

using a centrifuge (teacher demonstration) You will need: centrifuge mixture containing iron oxide, lead oxide (red lead) and water CAUTION Use red lead in a wellventilated room. Avoid contact with skin and eyes. Do not dispose of down the sink.

◗ Allow the centrifuge to spin for

about a minute. ◗ Observe the mixture after

centrifuging.

DiSCuSSion 1

Describe the mixture after centrifuging.

2

Why must the test tubes be placed on opposite sides of the centrifuge?

3

Could the separated substances form a mixture again? Explain your answer.

4

What type of mixture was the iron oxide, lead oxide and water before centrifuging?

◗ Stir the mixture and then pour

equal amounts into two separate centrifuge test tubes. ◗ Put the test tubes on opposite

sides of the centrifuge.

activities RemembeR 1 When filtration is used to separate a mixture of muddy water, identify: (a) which part is the filtrate (b) which is the residue. 2 Recall what happens to a suspension if it is left to stand for a long time. 3 Recall which method of separation uses spinning to separate the parts of the mixture.

Think 4 Describe the properties of water and dirt that make them ideal to separate using filtration. 5 Describe the properties of tea-leaves and water that make them ideal to separate by centrifuging. 6 Early settlers would spin the billy three times in an anticlockwise direction before drinking their tea. Would it make any difference if the billy was spun in a clockwise direction? explain your answer. 7 During filtration, explain why it is important that the mixture is poured carefully.

CReaTe 8 Make your own billy tea. Instead of centrifuging the tea, use another method to separate the tea-leaves from the tea. Write down your method for separating the tea-leaves. Was it an effective method? explain your answer. 9 Design and construct a machine to separate a mixture of three substances. Create a brochure to advertise your separating machine. Include: ◗ the name of your separating machine ◗ a diagram of the machine ◗ what mixture your machine will separate ◗ instructions for using the machine ◗ an explanation of how the machine works ◗ the advantages that your machine has for its particular use. eBook plus

10 See if you can identify which mixtures can be separated by filtration by completing the Filtration interactivity in your eBookPLUS. int-0223 work sheet

3.2 Filtration

3 Separating mixtures

69

3.4

PReSCRibeD FoCuS aRea applications and uses of science

Separating blood About one million donations of blood are made in Australia each year. Some of the donations are given to people who have lost blood during surgery, accidents or disasters. Blood is also given to people during the treatment of many diseases, including cancer. These people need to be given a regular supply of blood.

The blood mixture Blood is a life-giving mixture. It can be separated into four parts: plasma, a clear, yellowish liquid; red blood cells, which carry oxygen; white blood cells, which fight disease; and platelets, which clot blood. Because each part of the blood has a special job to do in our bodies, different problems can be treated with different parts of the blood. In Australia, blood is collected and separated by the Australian Red Cross Blood Service. Separation allows doctors to treat a larger number of patients and save many lives.

Red blood cells

White blood cells not used

Filtration The mixture of red and white blood cells can be separated by a special kind of filtration. Red cells are used to treat people who have lost blood in an accident or surgery.

Red and white blood cells

Centrifuge Blood cells are suspended in the plasma. Like other suspensions, blood donations can be separated into parts by spinning. Red and white blood cells are heavier than plasma and platelets, so they are forced to the outside edge of the containers in the centrifuge.

Separating by centrifuging The parts that make up the blood mixture have different properties; the red and white blood cells are heavier than the plasma and platelets. The difference in the mass of these parts means that they can be separated using the process of centrifuging. Centrifuging involves spinning the mixture very quickly. The heavier parts of the mixture are forced to the outer edge of the centrifuge. The lighter parts can then be decanted from the heavier parts.

Standard whole blood donation

Once blood is separated, each part has to be stored differently. • In a normal week, the Australian Red Cross Blood Service needs about 21 000 blood donations to meet the demand for blood and blood products. Public holidays put a strain on the blood service, with fewer working days in the week to take that number of donations. The demand for blood is also likely to increase, due to the increase in accidents that can occur on long weekends. • The amount of blood in your body depends on how much you weigh. The blood volume of an adult of average weight is about 5 litres, so the standard donation of 470 mL is less than 10% of the donor s total blood volume. This amount is easily replenished by the body. To help avoid fainting during or after a donation, you must be over 18 and weigh more than 50 kg to be a blood donor.

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• Red blood cells can be stored for 42 days at 2 6 C. • Plasma can be frozen for 12 months at 40 C. • Platelets are stored for 5 days at 20 24 C. During this time they have to be moved at least every 12 hours, to stop them clumping. (Platelets seal wounds in our bodies by sticking together.)

Plasma

Platelets

activities RemembeR

Centrifuge Further centrifuging separates the plasma solution from the platelets. Plasma is used to treat many diseases.

Plasma and platelets

1 explain why blood is separated into different parts. 2 Recall why blood clots do not form in a blood donation. 3 identify which technique is used to separate the different parts of blood. 4 Describe which separation technique is used to separate red and white blood cells.

Think 5 explain why blood is separated in a centrifuge rather than left to settle by itself. 6 Deduce what property of plasma and platelets allows them to be separated with a centrifuge.

Plasma donation Some donors give only the plasma from their blood. As the blood is taken out of the donor, it passes through a machine that separates the plasma from the rest of the blood. The blood cells are pumped back into the donor.

CReaTe 7 Create and construct an advertisement to encourage people to donate blood. The advertisement could be in the form of a poster, a song, a set of digital photos or part of a multimedia presentation.

ReSeaRCh

Red Cross blood donor

8 investigate the following facts about blood donation: (a) how old you need to be to donate blood (b) the minimum weight blood donors must be (c) why you cannot donate blood if you have recently had a tattoo done.

3 Separating mixtures

71

3.5

Separating solutions Separating undissolved substances from a liquid is easier than separating substances that have been dissolved into a solution. To do this, you need to make use of the fact that the solute and the solvent have different chemical and physical properties. Many methods of separating a solute from the solvent in a solution rely on the fact that they have different boiling points.

Distillation Some laboratory experiments require the use of pure water. This water is produced by a process called distillation. Tap water is placed in the boiling flask (see the diagram at right) and heated to the boiling temperature for water, 100 C. The water boils, evaporates and becomes steam. The steam travels along the water condenser. The steam inside the condenser is cooled to below 100 C and condenses to form liquid water. The condenser is kept cool by running cold water through its outer jacket. The pure water collected in the conical flask is called the distillate and can be rightly labelled distilled water. The impurities in the water are left behind in the boiling flask.

Black tray The black tray warms up when the sun shines on it. The salty water in the tray heats up as well. The water begins to evaporate, leaving the salt behind.

Clean water trough The liquid water trickles down along the glass cover and falls into a trough. This water is free of salt and other impurities. The salt remains in the black tray, where it can be collected and used for other purposes.

Equipment for solar distillation

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Core Science | Stage 4 Complete course

eBook plus

eLesson

Distillation Watch this video lesson to learn how distillation can be used to turn salty water into pure water. eles-0060

Distillation can be used to separate pure water from sea water. It can also be used to separate a mixture of two liquids, as long as they boil at different temperatures. Thermometer

Equipment used for distillation in the laboratory Cooling water out Cooling water

Steam

Steam condenses

Condenser

Water

Boiling flask Cooling water in Conical flask

Reflector The reflector helps to direct sunlight onto the tray.

Glass cover The glass cover stops the evaporated water from escaping. When the water vapour reaches the glass, it begins to cool down. The vapour turns back into liquid water.

evaporation

Chromatography

Evaporation works in a similar way to distillation, except that evaporation does not require the solution to reach boiling point and tends to take longer. In places where fresh water is scarce, the evaporation method is used in the form of water stills to turn salty or otherwise undrinkable water into a purer drinkable form. Water stills heat the impure water solution to the point where the pure water evaporates from the mixture, leaving behind salt and other impurities. The chief advantage of the evaporation method of purifying water is that it can be done with very simple equipment.

Paints, inks, dyes and food colourings are often mixtures of substances that have different colours. You can separate a mixture of different colours using paper chromatography. In paper chromatography, a liquid soaks through the paper and carries the mixture with it. Some substances in the mixture are carried through the paper faster than others. In this way, the substances in the mixture are separated along the paper. Chromatography works because different colours have different solubilities. Some colours dissolve more easily than others. Water is a very good solvent for many food colours. However, to separate the colours, they are not all placed straight into the water. For paper chromatography, the food colouring is placed on paper just above the solvent. The colours dissolve as the solvent soaks up the paper column. The colours separate because they are washed along the paper at different rates. The less soluble colours move more slowly and travel less distance up the paper. More soluble colours move more quickly up the paper.

Crystallisation In Investigation 3.5, you may have found very small salt crystals on the wall of the bowl. This is the solute left behind when the solvent (water) evaporated from the salt water solution. Crystallisation can be used if it is more important to collect the solute than the solvent. The solvent is usually lost to the atmosphere during this process and not collected.

InveStIgatIon 3.5

◗ Leave undisturbed for a couple of hours then examine

the contents of the bowl and the cup.

making a simple water still Plastic sheet

You will need: trowel cup bowl salt water solution scissors plastic bag some small stones

Rocks

Bowl Cup

◗ Dig a shallow hole in the ground outside. The hole should

be a few centimetres deeper than the height of the cup and should be in a spot that gets a lot of sun.

Salt water

◗ Put the bowl in the bottom of the hole and put the cup in

the middle of the bowl. ◗ Pour the salt water into the bowl. Don t allow any to get

into the cup. ◗ Cut the side seams of the plastic bag and open it up so

that it forms a flat sheet of plastic. Place the plastic over the hole, using small rocks to anchor it in place. Make sure that the hole is completely covered. ◗ Place a small stone in the middle of the plastic sheet, just

above the mouth of the cup.

DiSCuSSion 1

How has the water level in the bowl changed?

2

Is there any residue on the walls of the bowl? What do you expect this is made of?

3

How is the water in the cup different from the water in the bowl? You may need to taste it to tell the difference check with your teacher first!

3 Separating mixtures

73

How chromatography works Separated colours The colours that dissolve more easily are carried further up the filter paper by the solvent. The colours become separated along the paper strip. Sample of foodcolour mixture A small amount of food colour is placed on the paper, above the level of the solvent. Solvent The filter paper is hung so that it just dips into the solvent. The solvent soaks up the strip of filter paper, taking the food colours with it. A chromatograph automatically separates mixtures by chromatography.

InveStIgatIon 3.6 Fun with crystals This activity must be done in class with your teacher. You will need: 2 test tubes solid copper sulfate (or alum) a balance 150 mL beaker 3 glass stirring rods hot water string test-tube rack forceps microscope (optional) piece of filter paper filter funnel conical flask or beaker 2 paperclips ◗ Weigh 28 g of the copper sulfate in

the beaker.

◗ Pour the blue copper sulfate

◗ Quickly pour equal volumes of the

solution into two test tubes. Cool one test tube by putting it under cold running water. Glass stirring rod

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Core Science | Stage 4 Complete course

Attach the paperclip to the end of the string and arrange it as shown below. Do the same for the other test tube. ◗ Leave both test tubes to cool

overnight in the test-tube rack. ◗ Remove some crystals using

forceps. ◗ You may wish to view the crystals

under a microscope. ◗ Crystals with interesting shapes

can also be made using alum (potassium aluminium sulfate). String

DiSCuSSion

Copper sulfate solution

1

What can you see in the test tubes?

2

Is there any difference in the size of the crystals between the two test tubes?

3

How could you make bigger crystals?

Paperclip

◗ Prepare a hot concentrated solution

of the copper sulfate by pouring 20 mL of hot water into the beaker. Stir the solution until no more solid will dissolve.

◗ Tie the string to the glass rod.

solution through the filter paper into the conical flask or beaker. The undissolved copper sulfate will remain on the paper.

Test tube

◗ Stand the filter paper so that the

InveStIgatIon 3.7

end just dips into the water. Make sure that you keep the dot of food colouring out of the water.

Separating colours Pencil

◗ Fix the filter paper to a pencil to

hold it in the beaker.

Food colouring Each one of the food colourings that cover these chocolates is a mixture of different colours. How can the different colours be separated?

You will need: food colouring toothpick filter paper scissors 250 mL beaker pencil ruler

activities RemembeR 1 Recall which methods of separation can be used to separate the parts of a solution. 2 explain the purpose of the glass cover on a solar water still. 3 Recall why water is used as a solvent to separate food colours. 4 identify the colours found in this ink, from: (a) the fastest moving to the slowest moving (b) the most soluble to the least soluble.

Think 5 Describe the difference in properties that distillation relies on.

Filter paper

◗ Leave the filter paper to stand until

Water

◗ Repeat the experiment with

◗ Cut a piece of filter paper

approximately 10 cm by 3 cm.

the water has risen almost to the end near the pencil. different food colourings.

DiSCuSSion 1

What colours were in the first food colouring tested?

2

How do you think the colours are actually separated using this method?

3

List the different food colourings that you tested. For each one, write down the colours that made up the food colouring.

◗ Rule a pencil line 2 cm from the end

of the paper. ◗ Use the flat end of a toothpick to

place a small dot of food colouring in the centre of the pencil line on the filter paper. ◗ Pour tap water into the beaker to a

depth of 1 cm.

6 explain why crystallisation would not be suitable for purifying water. 7 Deduce why cool running water is passed through the distillation equipment. 8 explain why the mixture is placed above the level of the solvent in chromatography. (Hint: What would happen if the mixture was put in the solvent?) 9 Zoe performs a chromatography experiment on waterproof markers using water as a solvent. Will her experiment work? explain your answer.

DeSign anD CReaTe 10 Use chromatography to create colourful designs that can be displayed as scientific art. Fold the filter paper and use different colours to make your designs unique.

inveSTigaTe 11 An oil spill at sea can ruin the local environment and kill wildlife.

investigate when and where the worst oil spill disasters have occurred and how the oil was separated from the water. 12 investigate how to distil perfume. 13 investigate different types of solvents that could be used to separate pen ink and ink from waterproof markers. Before running the experiment, have your choice of solvents approved by your teacher. As a starting point, you may wish to use methylated spirits. 14 Does the colour of food affect whether people choose to buy and eat it? Design an experiment to test your answer. eBook plus

15 Use the Chromatography weblink in your eBookPLUS to watch a simple time-lapse chromatography animation. work sheets

3.3 Distillation 3.4 Evaporation and crystallisation 3.5 Chromatography

3 Separating mixtures

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3.6

PReSCRibeD FoCuS aRea applications and uses of science

Down the S-bend Every time you flush the toilet, have a shower, wash the dishes or your clothes or even clean your teeth, the waste water travels into an underground sewerage drain.

eBook plus

eLesson

Treating sewage Watch this video lesson to learn about water and sewage treatment and the use of recycled water in Australia. eles-0059

Flush pipe

out into the surrounding area. The sludge needs to be removed from time to time.

S-bend trap

To the sewerage drain

The S-bend trap in the toilet fills with clean water to prevent smelly gases from the sewer travelling back into the house.

The waste water is a mixture of human body waste flushed down the toilet, and detergent, dirt, toothpaste, food scraps and other materials washed down the drains. The mixture, which is mostly water, is called sewage. If you live in a major city, the sewage in the drain under your house flows into a larger drain under your street and travels through the sewerage system to a treatment plant. The waste water needs to be treated before it can be returned to the environment. Sydney is presently serviced by 31 sewage treatment plants, which are located along the coast and inland. The three largest coastal plants at Bondi, Malabar and North Head process three-quarters of the city s sewage. Between them, they process nearly 1 billion litres of waste water every day! Of this, over 35 million litres of water is recycled. All of the collected biosolids are treated and then turned over for agricultural use, mostly as fertiliser, and the remaining treated waste water is piped 3 kilometres or so offshore where it is emptied deep in the ocean. In country centres, treatment plants are usually located on the edge of the town. These plants may discharge treated water into nearby rivers. If there is no local treatment plant, the waste water will flow into a personal sewage treatment system a septic tank buried in the backyard. A septic tank contains bacteria that break down the sewage. A thick, smelly sludge is formed. The sludge sinks to the bottom of the tank and clear water flows

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Waste water treatment Waste water contains suspended solids, such as bacteria, grit and dirt, as well as some large items like rags and sticks. It also contains many dissolved substances.

The Tank Stream was Sydney s first water supply. It still flows beneath the city s streets.

When the waste water arrives at the sewage treatment plant, it passes through a screen (a wire mesh filter) that removes the larger items. The sewage then flows into settling tanks where it is kept for about two hours. In the settling tanks, suspended solids settle to form a sediment, and floatables such as oil and plastic collect on top of the sewage and are removed. The watery part of the sewage flows from the settling tank into secondary treatment. This waste water still contains dissolved substances and bacteria.

Secondary treatment takes place by filtering the water though soil and grass or by storing it in a series of one-metre-deep lagoons for two to four months. In the secondary treatment, the bacteria in the waste water break down the dissolved substances to purify the water further. In the lagoons, sedimentation also takes place. The treated water looks clear but it is still not safe to drink.

be poisonous or harmful to living things. Some things that can go down the sink at home in small amounts are: • drain cleaners • window cleaners • kitchen and bathroom cleaners • disinfectants (unless you have a septic tank). At school, you should not tip anything down the sink except water, unless your teacher instructs you to.

Think first! There are many materials that should not be tipped down kitchen, bathroom, laundry or school laboratory sinks. The treated water is eventually released into the sea, but there are many substances that the sewerage system is not designed to treat.

activities RemembeR 1 Recall what substances are found in waste water. 2 explain how a septic system works. 3 identify substances that should not be tipped down the kitchen sink.

Think 4 Propose why disinfectants that kill bacteria cannot be poured down a septic system. 5 A certain type of shower provides water at a rate of 11 litres per minute. (a) If you have a five-minute shower, calculate how much water you would use. (b) Calculate how much water you would use showering in a year. (c) Calculate how much water your family would use showering in a year.

These substances include: • chemicals such as oven cleaners and insect sprays that are poisonous • substances like fat and oil that don t dissolve in water. These substances can eventually find their way to the sea, polluting it and killing or harming animals, plants and other living things (like algae) that live there. Substances like these should be saved for collection by local councils. Small objects like cotton buds and tampons should not be flushed down the toilet because they can block the filters at treatment plants. These objects can be put out with other household garbage.

Play it safe The best policy at home is to avoid putting down the sink anything solid or oily, or that you suspect may

6 (a) Make a list of the many ways that people use water in their homes. (b) Propose ways to reduce water usage.

inveSTigaTe 7 investigate where your sewage goes. If you live in the country, ask your local shire or locate your septic system. 8 Find out the kind of treatment (primary or secondary) that is used for Sydney s sewerage system. Where does the treated water go? assess how suitable this system is for a large city like Sydney. 9 Find out more about the Tank Stream that runs below Sydney. What might be the difference between today s water supplies and those of Old Sydney? 10 investigate who is responsible in your area for the collection of waste that cannot be tipped down the kitchen, bathroom or laundry sinks, and how often it is collected.

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77

3.7

PReSCRibeD FoCuS aRea applications and uses of science

Fit to drink? unwanted substances Water used for drinking and washing needs to be clean and free of harmful substances. Water supplies can be contaminated by dissolved substances or substances suspended in the water. Besides clay, there are a number of other contaminants. • Human and other animal body wastes contain disease-causing micro-organisms. • Algal blooms can release poisonous substances into the water. They can also affect the taste and cause odour problems. • Pesticides and detergents can be washed into rivers and contaminate water supplies. • Poisonous chemicals may also be washed into rivers. • Salt dissolved in water can make it unfit for drinking. • Iron dissolved in water can contaminate it. This is common in bore water. • High levels of calcium and magnesium salts can cause water to be hard , making it difficult to lather. This causes problems in laundries, bathrooms and kitchens.

Sydney s water The tap water that we drink in Sydney is slightly alkaline (the opposite of an acid) because of the chemicals that have been added to it during the filtration process or that have leached into it from the pipe systems being used. A litre of tap water can contain as much as 150 milligrams of undissolved solids and, on average, 20 mg of calcium, 5 mg of magnesium, 1 mg of fluoride, 10 20 mg of sodium and a lot of other inorganic chemicals, all of which contribute to making Sydney s water much harder than tank water. However, many of these chemicals are there for a good reason! The calcium in the water supply is mainly in the form of a compound called lime. Lime is added to balance the acidity of the water caused by adding chlorine and fluoride. A litre of water also contains about 0.8 mg of chlorine and between 0.05 and 1.45 mg of monochloramine. These are disinfectants that are used to kill any dangerous bacteria or micro-organisms

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that may enter the water supply. The amount of disinfectant added to the water varies widely depending on a number of factors. For example, in summer, the warmer water tends to allow bacteria and microbes to increase faster, so more disinfectant is added to kill them. Fluoride is also added to help prevent tooth decay.

Would you drink this water? Would you like your water to come out of the tap looking like this? Would you bathe or shower in it? Imagine your clothes after washing them! The cloudiness of the muddy water is caused by tiny clay particles. Muddy water is an example of a colloid. A colloid is a cloudy mixture that contains suspended particles too small to be removed by filtering.

Country water supplies If you live in a country town, your water probably comes from a nearby river or lake. It is quite likely you would not want to drink that water unless it had been purified. Many country towns have their own water treatment plants. Water is pumped from the river or lake into the treatment plant. The cloudy water contains mud and other substances in suspension, which can be settled out of the water by a process called flocculation. The suspended particles would take a long time to settle if the water were just left standing, and so the chemical alum (potassium aluminium sulfate) is added to the cloudy water to make the small particles clump together. These clumps are called floc. The floc is heavy enough to settle to the bottom of the tank and form a sediment. The water above the sediment is clear and flows off to the filtering stage. After flocculation, the clear water is filtered through sand and gravel to remove any leftover suspended substances in the water. Chlorine is added to kill harmful bacteria. The purified water is then pumped to the local water tower, which then supplies the town with drinking water.

◗ Add two drops of bleach (which

InveStIgatIon 3.8 Treating your own dirty water You will need: muddy water (muddy water made with clay is best) alum (aluminium sulfate) limewater bleach flowerpot tripod sand gravel two 250 mL beakers stirring rod

Muddy water mixture

contains chlorine) to your filtrate.

DiSCuSSion 1

Sand

Flowerpot

Gravel Tripod

◗ Add half a teaspoon of alum

Beaker

and 10 drops of limewater.

Filtrate (water)

◗ Stir the water to mix the

A flowerpot water filter

allow the water to stand and the floc to settle to the bottom. ◗ Add gravel and sand to the

flowerpot to make the water filter as shown in the diagram above.

activities RemembeR 1 identify the chemicals that are added to Sydney s water and explain why they are added. 2 explain why chlorine is added to water. 3 Recall five substances that can contaminate drinking water.

Think 4 If you live in a country town that does not fluoridate the water, describe how you could obtain your fluoride. 5 Describe a natural method of separating mixtures that takes place in reservoirs over a long period of time.

Treatment stage

Description of water

Water after flocculation

into the beaker.

◗ Once you can see the floc forming,

Treating dirty water

Untreated water

◗ Pour 150 mL muddy water

chemicals and allow the floc to form.

Use a table like the one below to describe your water at each stage of the process. Include the appearance and odour of the water.

◗ Decant the water from the beaker

into your water filter. Collect the filtrate in a clean beaker.

6 At Taronga Zoo in Sydney, the seal pool s water is chlorinated to a maximum of 1 part per million, which is less than the amount in swimming pools. explain why such a small amount of chlorine is added to the water.

inveSTigaTe 7 Waste water in Taronga Zoo is generated by: ◗ hosing down animal exhibits ◗ filling animal and ornamental moats ◗ flushing toilets ◗ irrigating lawns. In 1998, it became the first zoo in the world to recycle its own waste water. investigate the methods it uses to recycle the water.

Water after filtering Water after chlorination 2

Which separation techniques did you use to purify the water?

3

Prepare a series of picture diagrams to explain the steps you have taken to purify the water.

vacuumed using a pool vacuum cleaner. investigate how this type of vacuum cleaner works. 9 The seal pool at Taronga Zoo is also contaminated by the seals own waste (the seals sewage). investigate how the amount of seal waste going into the main seal pool is minimised. 10 Compare the different brands of water filters available. Report on their cost, efficiency and ease of use. Also explain why people consider the use of these filters to be necessary. work sheet

3.6 Water treatment

8 The seal pool at Taronga Zoo and many swimming pools are

3 Separating mixtures

79

LooKIng BaCK 1 Copy and complete the table below to summarise what you know about separation techniques. Method

An example of its use

How it works

Filtration

7 Describe what properties allow the following substances to be separated from a mixture. (a) Peas from a mixture of peas and water (b) Oil from a mixture of oil and water (c) Gold particles from a mixture of sand and creek water (d) Cream from cow s milk

Decanting Crystallisation Distillation Centrifuging Separating funnel Chromatography 2 You have been asked to analyse some salt-contaminated soil and to propose a method for separating the salt from the soil. (a) Write out the method that you would use to obtain pure dry salt and pure dry soil. (b) Draw a labelled diagram showing how your equipment would be set up for each stage of your separation. 3 During an experiment, a teacher accidentally dropped some steel drawing pins into a bowl of sugar. Propose two methods that could be used to remove the drawing pins from the sugar. Briefly explain each method. 4 Black instant coffee is a mixture of coffee powder and hot water. Identify which substance is: (a) the solute (b) the solvent (c) the solution. 5 The diagram below shows a mixture being filtered in a school laboratory. (a) Identify each of the items or substances labelled (i) to (vii).

(i)

(v) (vi)

(ii)

(vii)

(iv)

(b) Explain the purpose of the stirring rod. 6 Pasta is cooked by boiling it in water. It sinks to the bottom of the saucepan when it is left to stand.

Core Science | Stage 4 Complete course

8 Recall one good reason why each of the following objects or substances should not be tipped down the sink or flushed in a toilet. (a) Fat and oil (b) Cotton buds (c) Oven cleaner 9 Assess whether each of the following statements is true. If the statement is false, replace the word in italics with the correct word. (a) Chromatography can be used to separate substances with different solubilities. (b) The heavier parts of a mixture are forced to the outer edge of a centrifuge when it spins. (c) Suspensions contain soluble particles in a liquid. (d) A suspension can be separated in a centrifuge. (e) Milk is a solution. (f) Emulsions are a type of colloid. 10 Explain why blood collected from the Red Cross Blood Service needs to be separated before it is used. 11 Describe the purpose of an S-bend in a kitchen sink pipe. 12 Identify which of the following separation techniques are used in a water treatment plant. You may select more than one answer. A Filtration B Chromatography C Centrifuging D Sedimentation E Crystallisation 13 Oil floats on water. When detergent is added, the oil forms droplets in the water that do not settle. What type of mixture has been formed? Justify your answer.

(iii)

80

(a) Identify what type of mixture the pasta and water is. (b) Describe two different methods that could be used to separate the pasta. (c) Which of the two techniques is best for separating the pasta and water? Explain your answer.

14 Blue-green algae has grown in a lake. It forms a fine, green suspension in the water. The local council wants to make the water clear again so that fish and other living organisms can safely inhabit the lake. Propose a method that you would use to solve the local council s problem. Remember, your method should not harm the fish already in the lake.

TeST YouRSeLF 1 Identify which of the following substances is a mixture. A Gold B Distilled water C Air D Carbon dioxide gas (1 mark) 2 Identify what would be the best method to use to separate iron filings from a mixture of sand, iron filings and salt. A Filtering B Magnetic separation C Sieving D Add water to the mixture and then filter it. (1 mark)

An ocean of salt Salt has been used by civilisations for centuries to preserve meats, cure hides, make cheese and other foods and as flavouring in cooking. Salt was essential for life. Some communities even used salt instead of money as a form of payment. A community grew wealthy from its ability to produce salt. Salt was mined from the ground, in the form of rock salt, or collected from sea water. The sea water, sometimes called brine, was evaporated and the salt collected. The brine was either heated over a wood fire or collected in shallow pools and left to heat in the sun. There s a whole ocean out there full of salt we just need to get it out of the water! , Marco remembered his grandfather saying. Marco lived during ancient Roman times. He lived in a town off the coast of the Mediterranean Sea. Marco himself now worked in the business his grandfather had started. He, too, marvelled at how he used the sun and winds to separate salt from sea water.

3 A sample of muddy river water can be described as A an emulsion. B a solution. C a colloid. D a suspension. (1 mark) 4 Centrifuging works best to separate substances with particles that have different A solubilities. B masses. C colours. D temperatures. (1 mark) 5 Read the story at right and use the information to answer the questions below. (a) Write down what you think Marco would have said to his son. Explain the two methods clearly. (3 marks) (b) Propose three questions that would Flavius have asked in return. (3 marks) (c) Extension Construct a flow chart that shows the steps involved in each salt harvest process using appropriate scientific terminology to describe changes of state and separation techniques. Spend some time researching ancient methods of salt separation before creating your flow chart. If using the internet, use search words such as ancient salt production , Roman times salt or salt evaporation . work sheets

3.7 Separating mixtures puzzle 3.8 Separating mixtures summary

This day was special; it marked the day his son, Flavius, would first work at the salt business. As they reached the hill, they smelled smoke from the wood fires and looked out over the flat natural basin where salty water collected in shallow pools. Flavius saw that the smoke was from fires burning under large rectangular lead pans. Marco turned to his son and explained the two ways they separated salt from sea water.

3 Separating mixtures

81

StUDY CHeCKLISt

ICt

mixtures

eBook plus

■ distinguish between pure substances and mixtures and give examples of each

3.1

■ recall that a mixture can be separated according to specific properties of its components

3.1

■ identify some common mixtures 3.1, 3.2

SUMMaRY

eLessons Centrifuging Learn how to separate a solid from a liquid using a centrifuge in a step-by-step process as a scientist demonstrates how to separate lead oxide from water.

Solutions ■ identify the solute and solvent in common solutions 3.2 ■ appreciate that water is a common solvent in solutions

3.2, 3.3, 3.5

■ distinguish between solutions and suspensions 3.2 ■ define the terms colloid and emulsion 3.2 Separating suspensions ■ describe the processes of filtering, sieving, decanting and centrifuging 3.3 ■ compare the effectiveness and limitations of these processes 3.3 ■ describe common household uses of these separation techniques 3.3 ■ recall how filtering and centrifuging are used in the isolation of blood products 3.4

Separating solutions ■ describe the processes of distillation, evaporation, crystallisation and chromatography

3.5

■ explain how distillation and evaporation may be used to purify water

3.5

Searchlight ID: eles-0061 Distillation Watch a scientist guide you through the process of distillation, which can be used to turn salty water into pure water. Searchlight ID: eles-0060 Treating sewage Be swept down the plug hole and learn about the processes of sewage treatment, as well as the many uses of recycled water in Australia. A worksheet is attached to further your understanding. Searchlight ID: eles-0059

interactivities applications and uses of science ■ describe the processes used to separate materials in recycling plants

3.1

■ describe the processes by which sewage is treated 3.6 ■ evaluate the appropriateness of current sewage treatment systems

Time Out mixtures This exciting interactivity challenges you to identify whether a series of liquid mixtures are suspensions, solutions or emulsions. You must answer quickly before your time runs out.

3.6

■ appreciate that water often needs treating before it is drinkable

3.7

■ recall common contaminants found in water 3.7 ■ identify chemicals that are often added to water supplies and their purpose 3.7 ■ describe how blood is separated into its components 3.4

Searchlight ID: int-0224 Filtration This interactivity tests your skills in recognising which commonly used mixtures can be separated by the process of filtration. Searchlight ID: int-0223

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Core Science | Stage 4 Complete course

4

Classification

The Great Barrier Reef is home to thousands of species of plants and animals. But how much do we know about them? The first step in learning about an organism is to classify it and give it a name. By sorting living things into groups, we can find out which species are closely related and begin to understand more about them.

In this chapter, students will: 4.1 ◗ learn about the characteristics of

living things 4.2 ◗ construct and use dichotomous

keys 4.3 ◗ learn about classification

hierarchy 4.4 ◗ differentiate between vertebrates

and invertebrates 4.5 ◗ learn about the characteristics of

vertebrate groups 4.6 ◗ learn about the three groups of

Australian mammals 4.7 ◗ investigate the work of some

Australian scientists in the field of classification 4.8 ◗ learn about the characteristics of

invertebrate groups 4.9 ◗ investigate useful and harmful

microbes 4.10 ◗ learn about classification in other

cultures.

A classification system helps us sort living things into groups and begin to understand more about them.

4 Classification Thinking about classification Classifying means putting things into groups. You classify things all the time. For example, when you organise your school bag, you are classifying things: •  Which types of items do you put in your pencil case? •  Which items go in your sports bag? •  What goes in your wallet? •  What do you store in your lunch box? •  Do you use particular parts of your school bag to store certain items? 1. Imagine that the contents of all the bags you take to school were tipped onto the floor. Write down some rules that would help your friends decide what to put where in your school bag; for example, all the things you can use to write go in the pencil case. 2. The pictures below show some living things found in the ocean. Work with a partner. Organise the living things first into two groups, and then into three groups. Present your answer in the form of a table.

A

B

3.

4. 5. 6.

Compare your answer with the students next to you. Did you use the same criteria to classify the living things? One of the pictures below shows coral. Is coral actually a living thing? What features make something living rather than non-living? Which picture(s) shows a fish? Justify (give reasons for) your answer. What features does an animal need to be classified as a fish? What features does a living thing need to be classified into each of the following groups? (a) Plant (b) Insect (c) Mammal (d) Homo sapiens (human) C

D

E F

G

4.1

Is it alive? Classification means sorting things into groups. We can sort all things into two groups: living and non-living. Trees are living things but rocks are not. What about a piece of bark that has fallen from the tree, or some lichen growing on the rock? Are they living things? To find out, we need to consider the following characteristics.

move Many living things move independently. That means that they can move without having something pushing or pulling them. Animals move in many different ways. Some walk or run, some swim and some fly. The movement of plants is less obvious. Certain plants can open and close their flowers; others such as sunflowers turn towards the sun. Movement is not an essential feature of living things. Some living things such as lichen and some bacteria cannot move independently. Screaming is one way to respond to something frightening.

Respire All living things need energy to survive. Most living things get their energy from a process called respiration. This is a chemical reaction where glucose reacts with oxygen to form carbon dioxide and water. Energy is released in the process. Animals get the glucose they need for respiration from the food they eat. Plants make glucose using a process called photosynthesis. Glucose Oxygen Jellyfish can propel themselves through the water.

Respond All living things respond to changes in their environment. Humans shiver if it is cold and run away if they can see danger ahead. Plants grow towards light and close the pores in their leaves when it is hot. Kangaroos lie in the shade on hot days and lick their forearms to keep cool.

Mitochondrion

Carbon dioxide Water Energy

Respiration

4 Classification 85

Assimilate

Excrete

Living things assimilate (take in and process) substances. Animals assimilate food. They eat food. The food is then broken down inside their bodies and chemicals from the food, such as glucose, amino acids and vitamins, are used for various processes inside the body. Plants do not eat food. When they photosynthesise, they can make their own food using sunlight. However, plants do assimilate some substances, including water and minerals from the soil and carbon dioxide from the air.

Organisms produce and excrete (get rid of) waste. Humans breathe out carbon dioxide, which is a waste product of respiration, and urine, a waste product of the breakdown of proteins. We also excrete water and salts in the form of sweat. Just like animals, plants respire throughout the day and night. During the day, plants also photosynthesise. This process uses carbon dioxide and releases oxygen. So, during the day, plants actually excrete oxygen.

A dog excreting waste

Reproduce

Animals assimilate food.

Grow Organisms grow and develop as they age. Some living things grow throughout their whole life. Humans, elephants and other animals grow until they reach a certain height, and then they stop growing. As they get older, organisms may change in ways other than just increasing in size. Tadpoles lose their tails and grow legs as they turn into frogs. Caterpillars become butterflies, and male lions grow a mane as they reach adulthood. Humans grow rapidly in their first year of life.

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Core Science | Stage 4 Complete course

All living things reproduce. They can make copies of themselves. Bacteria and other single-celled organisms reproduce by dividing into two. In some cases, two organisms (a male and a female) are needed for reproduction. The male and female both produce sex cells, which need to combine to produce a new living thing. The sex cells of mammals are called eggs and sperm. They combine to start a new life. Plants can reproduce in a number of ways. Some plants produce seeds as part of their reproductive cycle. When animals have babies, they are reproducing.

is it non-living or dead? Something that is dead was once living. At some stage, it had all the features of living things but it has now stopped living. A squashed fly, the plant you forgot to water and the egg you had for breakfast are all dead. Non-living things do not have and never have had all the characteristics of living things. A Tamagochi, a car and a stereo all have some of the features of living things but they lack important features such as the ability to reproduce. They are non-living.

hiroshi ishiguro has designed robots that are so life like they are often confused for humans. he teaches at a university in Japan. The university is one hour away from his home so, to avoid travelling to and from work, he has made a robot that looks just like him. he controls the robot remotely from home and his own voice comes out of the robot s mouth. it usually takes a little while for his students to work out whether they are being taught by hiroshi or his robot. The robot is so like a human that many people find themselves apologising to the robot if they stare at it for a little too long.

Hiroshi Ishiguro and his robot twin

InveStIgAtIon 4.1 ◗ Construct another table the same

living, non-living or dead

as the one on the left but replace the bilbies with (a) paper (b) fire (c) a tree.

◗ Copy and complete the table below.

◗ Complete the table.

discussion 1

Which of the three bilbies is non-living? Which characteristics does it have?

2

Responds to changes in its environment

Which of the three bilbies is dead? Which characteristics does it have?

3

Respires (uses oxygen to process glucose and release energy)

Which, of the paper, fire and tree, is non-living?

4

Does the living thing have all of the characteristics listed?

5

Which characteristics does the living thing have that the non-living thing does not?

Characteristics

Robo-bilby (electronic toy)

Bilby

Bilby fossil

Can move

Assimilates (takes in) substances such as food and water Grows and develops as it gets older Produces and excretes waste Reproduces itself

4 Classification 87

Activities REmEmbER

Orchid

1 Match each of the words in column 1 with its correct meaning from column 2. Word

Kookaburra

Meaning

(a) Respire

A Make more copies of itself

(b) Grow

B React to a change in the environment

(c) Assimilate

C Get bigger

(d) Reproduce

D Take in and process substances

Roast dinner

Sun

(e) Move E Get rid of waste independently (f) Respond

F Get energy, usually by a chemical reaction between glucose and oxygen

(g) Excrete

G Change position from one place to another without being pushed or pulled

Leaf Boat

Water

Tomato

Glass of milk

2 Imagine that a funnel-web spider walked across your desk right now. outline three ways in which your body would respond.

Banana

3 Most living things need oxygen to survive. Explain why. 4 The words respiration and breathing are often confused. Explain the difference between these two terms. 5 outline how each of the following reproduces. (a) Magpie (b) Eucalyptus tree (c) Bacteria 6 Recall three waste products that humans excrete. 7 distinguish between dead things and non-living things.

Think And discuss 8 If we put together the first letters of the characteristics of living things (move, respond, respire, assimilate, grow, excrete, reproduce), they spell Mr Rager . Think of another way to remember the characteristics of living things. For example, you might find a sentence where each word starts with the first letter of one of the characteristics of living things. 9 Use Venn diagrams or double bubble maps to compare and contrast the features of living, non-living and dead things. Compare only two things at a time. 10 (a) classify each of the items shown in the following drawings as living, non-living or dead. Present your answer as a table. (b) Which of the things were difficult to classify? Why? (c) For the items you classified as non-living or dead, list the characteristics of living things they do not display.

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Core Science | Stage 4 Complete course

Boiled egg Emu egg Living, non-living or dead?

11 Non-living things often have some, but not all, of the features of living things. identify the features of living things that the following share. (a) Hot-air balloon (b) Television set eBook plus

12 Robots are becoming increasingly life like. Use the Asimo robot weblink in your eBookPLUS to find out about the Asimo robot and the androids designed by Hiroshi Ishiguro. (a) In what ways are these robots like living things? In what ways are they different? (b) What can the Asimo robot do? How could robots such as Asimo be used to help humans in the future? (c) Which features make the androids designed by Hiroshi Ishiguro so life like? work sheets

4.1 Is it alive? 4.2 Creatures from a parallel universe 4.3 Responding

4.2

Identification keys Once the features of an organism have been noted, the information can be used to identify it using identification keys.

branch (dichotomous = cutting in two ). It shows how some farm animals may be divided on the basis of similarities and differences in their features.

dichotomous keys

Features such as size, colour, behaviour and habitat are not good for classification because they can change throughout the life of the organism. Using the structure of an organism is much better.

The information that is used to classify organisms is sometimes put into a key. The key shown below is called a dichotomous key, because there are only two choices at each

Has four legs Does not have four legs

Has hooves

Does not have hooves Has a red comb

Has a woolly coat

Does not have a red comb

Does not have a woolly coat

Has four toes on each foot

Does not have four toes on each foot

In a dichotomous key, you always select from two choices. In this key, you decide whether or not an organism has a particular feature.

4 Classification 89

InveStIgAtIon 4.2 making a class key You will need: tape measures or string and rulers ◗ Measure, observe and record at

least 10 different characteristics for each member of the class. You may like to include some of the following: wrist size (cm) distance from elbow to shoulder (cm) foot length (cm) height (cm)

The dichotomous key at right is a branching key. Such keys are quite easy to create but, if there are many organisms to classify, they take up a lot of space. Another way of presenting a dichotomous key is in tabular format. To change a branching key into a tabular key, you just give each fork of the dichotomous key a number. This number becomes the step number in your tabular key. The diagrams on this page show the same key presented as a branching key at right and a tabular key below.

◗ Have someone from outside the

eye colour hair colour wears watch pierced ears

class use the key to find the identity of one of the class members.

◗ Have each member of the class

discussion

select a secret code name. ◗ Use some of these recorded class

characteristics to construct a key (tree map or dichotomous key) that will separate as many individuals (using their code name) as possible. (Hint: You may find it best to describe measurements as greater than or less than a particular measurement).

Wings

1

How successful was your key?

2

If you were to do the activity again, what would you do differently to improve its success?

3

Were some characteristics of more use than others? Explain.

No wings

Pterosaurus

Bony plates on back

No bony plates on back

Stegosaurus Horns

No horns

Triceratops

A branching key

Walks on two legs

Walks on four legs

Tyrannosaurus

Apatosaurus

B C A

1. Wings ....................................Pterosaurus No wings ....................................... Go to 2 2. Bony plates on back ......... Stegosaurus No bony plates on back ............. Go to 3 3. Horns.......................................Triceratops No horns........................................ Go to 4 4. Walks on two legs ......... Tyrannosaurus Walks on four legs ............Apatosaurus A tabular key

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Core Science | Stage 4 Complete course

D

E

Circular keys Circular keys are also very useful. To read a circular key, start in the middle and work outwards. As you go, choose one of the options given at each layer. When you get to the outer layer of the circle, you will have identified the organism. The diagram on the right shows the same information as the key on page 89, but it is presented as a circular key.

Sheep Has a woolly coat

Pig

Has four toes on each foot Does not Does have Horse not have woollya four toes on each coat foot

Duck Does not have a red Does comb

Has hooves

Has four legs

not have four legs

Farm animals

Does not have hooves

Has a red comb

Rabbit

Rooster

A circular key

Activities REMEMBER 1 Recall what a dichotomous key is used for. Why is it called dichotomous? 2 Propose why keys are sometimes presented in tabular rather than branching format.

THINK AND DISCUSS 3 Use the key on the previous page to classify the dinosaurs labelled A, B, C, D and E. 4 Imagine that you have landed on another planet. Weird creatures live there. You noted the characteristics of some that you saw and prepared the circular key shown at right. Use it to help you classify the creatures A and B you have just found, shown here.

Googly

Rosy snoz Huge red nose

Four eyes No antennae

Eight arms Frog conk Little green Six nose arms

A

Four legs

One leg

Zotter One eye Plant Four anten- Two head nae eyes

Alien Forked Two Three legs tongue arms Splitz

Four arms Big floppy tongue Slobber

Claws Long Dragon tail No claws Bloop

Two legs Short tail

B

Sharp teeth Chomper

5 Construct a tabular key using the branching key on page 89. 6 Collect a leaf from each of eight different plants in the school grounds. (a) On an A3 sheet of paper, create a branching dichotomous key to classify the leaves. (b) Construct the key in your exercise book as a tabular key.

work sheets

4.4 Branching keys 4.5 Tabular keys

4 Classification 91

4.3

In a class of its own Imagine how difficult it would be to identify one of the millions of living things in the world if people couldn t agree on one system for classifying (or grouping) them. Fortunately, there is a worldwide classification system that most scientists do agree on. It groups living things according to the structural features they have in common. Structural features include skull shape, teeth, number of legs, as well as the structure of the cells that they are made from.

Why classify things into groups?

ANIMALIA

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Core Science | Stage 4 Complete course

TAE AN PL

MON ER A

Classifying things into groups makes them easier to remember, describe and identify. For example, if you went to a supermarket to buy cornflakes, it would take you ages if the products in the supermarket were not classified into groups. Because cornflakes are classified as a breakfast cereal, you know where to look. Scientific curiosity has resulted in the discovery of an increasing number of living things. This has led to the increased need to classify living things into groups. All living things are called organisms. If you were to find an unknown organism, you could describe it on the basis of the sorts of features it shares with members of a particular group. However, it is not always easy to decide which group an organism fits into. For example, a French poodle looks very different from a sheepdog but they are both dogs. A wolf looks very much like a dog, yet it is not a dog. Today, almost two million living things have been classified PR by scientists. Back in the OT eighteenth century, as scientists IS TA were exploring new worlds and finding new examples to classify, they used a simple system an organism

was either in the plant kingdom or the animal kingdom. Eventually, living things were discovered that did not fit easily into these two groups. A new system was needed. Carl Linnaeus (1707 1778), a Swedish biologist, came up with a system that allows all living things to be classified on the basis of their similarities and differences. The original system developed by Linnaeus had three main kingdoms. Since then, scientists have learned more, and now use five kingdoms, plus extra groups for viruses, viroids and prions. It is likely that this system will continue to evolve as new discoveries are made.

F

The five kingdoms

UN

I G

The five kingdoms

classification hierarchy

The five kingdoms that most scientists recognise today are Animalia, Plantae, Monera, Protista and Fungi. Animalia contains many groups including worms, molluscs, fish, frogs, insects, reptiles, birds and mammals (such as dogs, camels and humans). They are complex organisms made up of many, often millions, of cells. They obtain food by eating or absorbing other living (alive or dead) things. Plantae includes mosses, grasses, flowering plants, shrubs and trees. They are made up of many cells that contain chlorophyll. Chlorophyll allows plants to use the energy of sunlight to make their own food from carbon dioxide and water. Oxygen is released as a waste product. This food-making process is called photosynthesis. Fungi includes mushrooms, toadstools, moulds, mildew and yeasts. They are usually made up of many cells, but some have only one cell. Unlike plants, they have no true leaves, flowers or stems and do not photosynthesise. They obtain their food by growing on other dead or living organisms. Protista includes single-celled organisms that have a nucleus. Amoeba and Euglena belong to this group. They live mostly in water. Monera includes bacteria and cyanobacteria. They are the simplest organisms on Earth, being made up of one cell. Most get their food from other organisms such as dead animals and plants. Some bacteria cause disease; other bacteria are used to make foods such as yoghurt. In chapter 15, you will find out more about the differences between the five kingdoms at the cellular level.

Kingdom is the highest level of classification. It can be broken down into smaller groups called phyla, which in turn can be broken down into groups called classes. Classes are made up of orders that themselves may contain a number of families. Families can be made up of a number of genera. ( Genera is the plural of genus.) Each genus may include a number of species. Kingdoms are very large groups that contain many species. A genus is a much smaller group. It contains only a few species. Species that belong to the same genus are very similar. A species is defined as a group of organisms that can interbreed and produce fertile offspring. When a species is given a scientific name,

the name consists of two words: the genus name followed by the species name.

sometimes, animals from different species interbreed, although the offspring they produce are usually not fertile. for example, a horse and a donkey can mate to produce a mule. however, the mule cannot reproduce; it is not fertile. A lion and a tiger can mate to produce a liger.

A liger is the result of a tiger and a lion interbreeding.

House cat Animalia Chordata

Tomato kingdom phylum or division

Plantae Magnoliophyta

Mammalia

class

Magnoliopsida

Carnivora

order

Solanales

Felidae

family

Solanaceae

elis

genus

ycopersicon

catus

species

lycopersicum

Phylum for Kingdom Animalia Division for Kingdom Plantae How living things are classified, using the Linnaean system

4 Classification 93

Activities

(c) Chimpanzees and humans are closely related. Which of the groups listed in the table do chimps belong to?

REmEmbER 1 define the term organism . 2 In the eighteenth century, which two kingdoms were used to classify all organisms?

Classification

3 identify the kingdoms that: (a) consist mostly of multicellular organisms (multicellular = made up of more than one cell) (b) consist only of unicellular organisms (unicellular = made up of only one cell).

Kingdom

Animalia

Made up of more than one cell; eat food

Phylum

Vertebrate

Have backbone

Class

Mammal

Have hair or fur; feed its young milk

Order

Primates

Have opposable thumb; nails instead of claws; binocular vision

Family

Homidae

Arms shorter than legs; nails flattened; upright stance

Genus

Homo

Walk upright on feet only; care for young for a long time

Species

sapiens

Large brain; can talk and think abstractly; have complex social structures

4 identify the five kingdoms that are now recognised, and give two examples of organisms that belong to each kingdom.

Group

5 List the levels of classification in order from the highest level to the lowest level. 6 define the term species . 7 A species name is made up of two words. What do these words indicate?

Think 8 A mnemonic is a trick that can be used to remember a list of words. For example, the following mnemonic can be used to remember the levels of classification: King Kingdom Phil Phylum Classed Class Ordinary Order Families as Family Generous and Genus Special Species Create another mnemonic to remember the levels of classification. You could use just the first letter of each level rather than the first syllable. 9 describe one way in which members of the kingdom Fungi are different from members of the kingdom Plantae. 10 classify each of the following organisms into its kingdom: dog, whale, wattle tree, mould, grass, spider, ant, jellyfish, bacteria, clover, yeast, moss. 11 The full classification for humans is shown below. (a) identify which group contains more living things, the kingdom Animalia or the order Primates. (b) Dogs belong to the kingdom Animalia; they are vertebrate and they are also mammals. Use the table to list some characteristics that dogs and humans have in common.

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What all living things in the group have in common

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icT 12 Search the internet to find more information (including pictures) about each of the five kingdoms. Use this information to construct, on a sheet of A3 paper, your own kingdom wheel similar to that on page 92. eBook plus

13 Use the Inspiration weblink in your eBookPLUS to download a trial copy of this visual thinking and learning software. Use the program to create a dichotomous key that can be used to sort organisms into the five kingdoms. 14 Test your ability to classify the world s living creatures by completing the Time Out kingdom interactivity in your eBookPLUS. int-0204

work sheet

4.6 Five kingdom classification

4.4

Which animal is that? Animals can be most easily grouped on the basis of whether they have an internal skeleton, an external skeleton or no skeleton at all. Animals with internal skeletons or backbones are grouped together and called vertebrates. Animals with external skeletons or no skeletons are called invertebrates. Only five per cent of animals are vertebrates whereas 95 per cent are invertebrates. Most of the invertebrates are insects.

Endoskeletons and exoskeletons Did you know that 75 per cent of all animals in the world have a skeleton on the outside of the body? These external skeletons are called exoskeletons. They may be thick and hard like those of crabs and lobsters or as thin and tough as those of ants and centipedes. As these animals grow, they sometimes moult or discard their old exoskeleton before growing a bigger one.

with an endoskeleton are connected onto the outside of the skeleton. The human endoskeleton is an internal skeleton that is made of bone or cartilage and covered in muscle and skin.

no skeleton at all Some animals, such as worms and jellyfish, have no skeleton at all. The body is supported by the pressure of fluid within it. What do you think would happen if a lot of fluid was lost? How can animals without skeletons move? Earthworms expand and contract their bodies to burrow through the soil. They use two sets of muscles to do this. One set of muscles wraps around the body. When these contract, the body becomes long and thin, enabling the worm to poke into crevices in the soil. The second set of muscles runs along the length of the body. When these contract, the worm becomes short and fat. This helps to anchor the worm in place, pushing the soil apart to form a burrow. By shortening the rest of its body, the worm pulls itself up and moves through the soil.

The largest animal on Earth, the blue whale, feeds on some of the smallest animals on Earth. Every day in the summer feeding season, an average-sized blue whale eats up to 4 tonnes of tiny animals like those shown below. Crabs have exoskeletons.

Frogs have endoskeletons made of bone or cartilage.

Although exoskeletons are good for jumping and swimming, they do not allow flexibility for the twisting and turning actions that are possible for animals with an inside skeleton (endoskeleton). In an animal with an exoskeleton, the muscles are attached inside the skeleton, whereas the muscles in an animal

4 Classification 95

ANIMALS

Has no backbone

Has a backbone

INVERTEBRATES

VERTEBRATES

Legs with joints

No legs

Body temperature is constant

Body temperature is not constant

ARTHROPODS (e.g. ant, scorpion, butterfly)

Has lungs when fully grown

Body covered with a shell or rough spiny skin Soft body usually covered with a shell ECHINODERMS (e.g. sea urchin)

Body not covered with a shell or rough spiny skin

FISH

Body covered with a rough, spiny skin MOLLUSCS (e.g. oyster, slug, octopus)

Moist skin with no scales

Scaly skin

AMPHIBIANS (e.g. frog)

REPTILES (e.g. crocodile, lizard)

Has tentacles

Has no tentacles

Has feathers

Has no feathers

CNIDARIANS (e.g. jellyfish, anemone)

WORMS(a) (e.g. earthworm, leech)

BIRDS

MAMMALS

(a) See page 105 for more information on worms.

Activities REmEmbER 1 describe the difference between vertebrates and invertebrates. 2 define the terms exoskeleton and endoskeleton . 3 identify the largest group of animals with an exoskeleton.

Think 4 identify which group of animals is the more common vertebrates or invertebrates. 5 Is a snail a vertebrate or an invertebrate? Explain your answer.

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Has gills when fully grown

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PORIFERA (sponge)

Classification of vertebrates and invertebrates into their main groups

6 Worms have muscles around and along their bodies. These allow them to become long and thin one moment and shorter and fatter the next. propose how this might help them move through the soil. 7 The key above starts by dividing animals into those with and without a backbone. propose at least one other way to divide them into two groups. 8 For the following group of animals dolphin, slug, beetle, horse, dog, jellyfish, spider, ant select a characteristic to divide it into: (a) two groups (b) three groups. Explain your choice of characteristic in each case.

9 interpret the dichotomous key above to answer the following questions. (a) identify which group each of the following animals belongs to. (i) One with a backbone and a changing body temperature and that has gills (ii) One with no backbone, legs or covering shell and that has tentacles with stinging cells (b) Work through the key backwards to identify as many characteristics as you can for: (i) birds (ii) molluscs (iii) reptiles.

4.5

vertebrates If you were asked to very quickly write down the names of ten animals, you would probably come up with the names of ten vertebrates. Even though most of the animals that live on Earth do not have a backbone (they are invertebrates), we tend to be more familiar with the vertebrates, the animals that do have a backbone. This may be because humans are vertebrates but also because many vertebrates are big animals and very difficult to ignore. Vertebrates have the following characteristics: •  a rod in their back called a notochord. In developing animals (embryos), the notochord is made of cartilage. Cartilage is softer than bone. Your nose and ears are made of cartilage. As animals develop, the notochord is replaced by a hollow tube called the vertebral column. It is made up of parts called vertebrae. Vertebrae are usually made of bone but, in sharks and some other fish, they are made of cartilage.

•  a nerve cord that runs through the middle of the vertebral column •  muscles attached to the vertebrae •  a brain protected by plates made of bone or cartilage (a skull) •  bones or cartilage in other parts of their bodies and muscles that are attached to these.

Vertebra

The backbone is not a single bone. It is made up of many small bones called vertebrae. The vertebrae are stacked on top of each other to form a hollow column called the vertebral column.

Spinal cord

Nerve

Dimetrodon was a meat-eating pelycosaur. The pelycosaurs were the most successful reptiles of the permian period. They looked like big lizards with huge sail-like fins on their backs. The pelycosaurs used this sail to regulate their body temperature. They could stand in the early morning sun with the sail arranged towards the sun to warm them up. They could turn it into the wind to cool off. it is thought that this fin arrangement was an early stage in the development of temperature regulation of mammals.

Vertebra The spinal cord runs through the middle of the vertebral column.

The body temperature of poikilothermic animals varies with their environment, but it stays relatively constant in homeothermic animals.

Dimetrodon

a mammal-like reptile

vertebrate groups

Vertebrates can be divided up into five main groups: fish, amphibians, reptiles, birds and mammals. The fish group is actually made up of a number of groups including the bony fishes and the cartilaginous fishes (fish with a skeleton made of cartilage). Some important differences between the groups of vertebrates are their body covering, their mode of reproduction and whether they are endotherms or ectotherms. Reptiles and fish have scales covering their bodies, birds are covered in feathers, mammals have

4 Classification 97

hair or fur and amphibians have moist skin. Most vertebrates hatch out of eggs. Birds produce eggs with a hard shell. Reptile eggs have a leathery shell whereas amphibian and fish eggs lack a shell and dry out unless they are in water. Most mammals, except monotremes, do

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not hatch out of eggs. Mammals have another important difference they feed their babies milk. All vertebrates except mammals and birds are ectotherms. That means that they do not maintain a constant body temperature. Lizards are ectotherms. On cold

+OOKABURRA EMU PENGUIN COCKATOO GALAH PARROT SEAGULL

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sæ3KINæWITHæSCALES sæ%GGSæWITHæ æææMEMBRANOUSæOR æææLEATHERYæSHELLSæLAID æææONæLANDæ sæ,UNGSæFORæBREATHINGæ sæ#HANGINGæBODYæ æææTEMPERATURE

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mornings, their bodies are cold and the chemical reactions inside their bodies occur slowly. After lying in the sun, their bodies warm up. Humans are endotherms. Our body temperature remains at a steady 37 C unless we are sick and have a fever.

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sææ&OUNDæONLYæIN æ WATER sææ#HANGINGæBODY æææTEMPERATURE sææ'ILLSæFORæBREATHING sææ-OSTæHAVEæEGGS ææææWITHOUTæAæSHELL sææ3KINæWITHæSCALES

Vertebrates can be classified into five main groups: fish, amphibians, reptiles, birds and mammals.

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#HARACTERISTICS

sæ3OFTæMOISTæSKIN æææWITHOUTæSCALES sæ%GGSæWITHOUTæAæSHELL ææUSUALLYæLAIDæINæWATER sæ,ARVAEæUSUALLYæLIVE ææINæWATER sæ!DULTSæUSUALLYæLIVE ææONæLANDæANDæHAVE æææLUNGS sæ#HANGINGæBODY ææ TEMPERATURE

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8 Explain why it is thought that the pelycosaurs were a link between reptiles and mammals.

Activities

9 In the table below, match the English translations to the scientific names.

REmEmbER 1 define the terms cartilage , vertebra , ectotherm and endotherm . 2 The following features are found in many vertebrates. The words have been scrambled. Unscramble the words and write them in your workbook under the heading Vertebrate features . kllus, bainr, cdhnooort, cdeenorrv, abceellmnourrtv, celmus, benos 3 Which group of vertebrates do humans belong to? Explain why. 4 identify the group of vertebrates that each of the following animals belongs to. (a) Snake (b) Cane toad (c) Goldfish (d) Whale (e) Emu (f) Shark

English translation

Scientific name

(a) Greek: living a double life

A Reptilia

(b) Latin: creeping

B Aves

(c) Latin: birds

C Amphibia

10 Amphibians start their lives in water. For example, many frog species start as tadpoles living in ponds and streams. However, adult frogs breathe air using lungs and can travel some distance away from water. Explain why amphibians need to come back to the water to lay eggs.

invEsTiGATE

5 outline the function of the huge sail-like fin on a pelycosaur s back. 6 Copy and complete the table at the bottom of the page.

11 Fish can be divided into a number of groups. investigate what the groups are, the characteristics of each group and list two examples from each group.

Think 7 Who am I? identify the vertebrate group that each of the following animals belongs to. (a) I have lungs but no legs. My offspring are found in membranous-shelled eggs and use lungs to breathe. (b) I have moist skin but no scales, and two pairs of legs. Although I have lungs and live on land, my young usually live in water and use gills to breathe. (c) I have a constant body temperature and feathers and lay eggs with a hard shell. (d) I have scales, I breathe using gills and I live in water. Fish

eBook plus

12 Design a dichotomous key to separate and classify the vertebrates into the five groups described on page 98. Use the Inspiration weblink in your eBookPLUS to download a trial version of this visual thinking and learning software. work sheet

4.7 Classifying vertebrates

Amphibians

Reptiles

Birds

Mammals

Is body temperature constant or changing? What is the body covered with? Does it lay eggs? If so, what type of shell do the eggs have? Does it feed its young milk? Give three examples.

4 Classification 99

4.6

Australian mammals There are three different types of mammals: placentals, marsupials and monotremes. These groups differ in how they give birth to their young. •  Most mammals are placental mammals. Their young grow and develop inside the body of the mother, receiving nutrition and oxygen via a structure called the placenta. •  The other two groups of mammals, the marsupials and monotremes, are found mainly

in Australia. The following diagram explains how they give birth to their young.

What kind of creature is this? When European explorers returned from Australia with stories of strange animals such as kangaroos, wallabies, koalas and wombats, people were surprised. Australian animals seemed so different from those

common in Europe and other countries. Imagine their disbelief when the platypus was first described to them. This strange animal had webbed feet and a bill like a duck, but it had no feathers. It laid leathery eggs like lizards and crocodiles, but it did not have scales on its skin. It also had fur and a large tail like that of an otter but, like a reptile, it had only one opening for ejecting faeces and urine.

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0LACENTALæMAMMALS

sææ9OUNGæGROWæINSIDEæTHEæBODYæOF ææææTHEIRæMOTHERæANDæAREæATTACHEDæ ææææBYæAæCORDæTOæTHEæPLACENTA æWHICH ææææSUPPLIESæTHEIRæFOOD sææ4HEYæAREæWELLæDEVELOPEDæWHEN ææææTHEYæAREæBORN sææ-OSTæMAMMALSæAREæPLACENTAL æææ MAMMALSæ%XAMPLESæINCLUDE æææ HORSES æMICE æHUMANS æCATS æææCOWSæANDæPIGS

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-ARSUPIALS

sææ!LTHOUGHæBLINDæANDæNAKED æææNEWBORNæMARSUPIALSæCRAWLæFROM æææTHEIRæMOTHERSæBIRTHæCANALæTOæHER æææPOUCHæANDæATTACHæTHEMSELVESæTO æææTHEæNIPPLEæTOæFEED sææ9OUNGæAREæBORNæATæAæVERYæEARLY æææSTAGEæOFæDEVELOPMENT sææ4WO THIRDSæOFæTHEæWORLDS æææMARSUPIALSæLIVEæINæ!USTRALIA æææ%XAMPLESæINCLUDEæKANGAROOS æææWOMBATS æPOSSUMSæANDæKOALAS

-ONOTREMES

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In London in 1799, an Australian sailor presented a platypus specimen to Dr George Shaw, a prominent biologist of the time. It was so different that Shaw considered it a hoax and tried to cut off the duck-bill with scissors. The scissor-marks are still visible on the preserved platypus skin in the British Museum (Natural History) in London. It is thought that the reason for the existence of Australia s unique animals like the platypus is Australia s isolation from the other continents after they separated millions of years ago. The animals evolved over time to be well suited to the unique Australian environment.

largest kangaroos of today. They had a short face and deep skull with huge molar teeth. Their molars may have helped them to eat tough plant foods. Procoptodons may have used their very long forelimbs to pull down the branches of trees and shrubs.

diprotodons The members of this group are all extinct. They were the largest of all the marsupials. Diprotodon optatum, often referred to as the diprotodon, was the largest known marsupial to have ever lived. The skeleton of the diprotodon suggests that the animal was about the size of a rhinoceros, being about three metres long and possibly weighing about two tonnes.

Giant mammals Australia was once inhabited by megafauna: giant mammals including wombats the size of cars and lion-like marsupials called Thylacoleo carnifex. There were also giant flightless birds called Genyornis and a seven-metre long lizard by the name of Megalania.

Giant kangaroo The extinct giant kangaroo, Procoptodon, was heavily built and stood about 2.5 metres high. Procoptodons may have weighed about four times as much as the

Activities REmEmbER 1 construct a three-column table and use it to summarise the main characteristics of each of the three groups of mammals. 2 outline how marsupials differ from all other mammals. 3 How did placental mammals get their name? 4 identify which group of mammals the echidna belongs to. What other animal belongs to this group? 5 describe two features of each of the following animals. (a) Diprotodon optatum (b) Procoptodon

Think 6 State the differences between Procoptodon and the largest of today s kangaroos. Suggest reasons for the differences.

7 identify which features of the platypus and other monotremes are: (a) like those of placental mammals (b) unlike those of placental mammals.

invEsTiGATE 8 Find out about dugongs and why they are thought to be the basis of mermaid myths. 9 Elephant calves may drink 11.4 litres of milk a day. Find out: (a) whether an elephant baby uses its trunk or its mouth when suckling (b) how much milk some other mammals drink per day, and then summarise your results in a table or graph. 10 Did you know that adult hedgehogs have 5000 spines? So that the birth canal is not damaged when the mother is giving birth, the initial spines of a newborn are covered

Diprotodons were larger than humans.

with a layer of skin. The spines pop through hours after birth. Although hedgehogs are mammals and they look a little like echidnas because of their spines, they are not classified as monotremes. (a) Find out whether hedgehogs are placental mammals or marsupials. (b) outline how hedgehogs differ from echidnas. (c) A porcupine also has spines. identify the group of mammals a porcupine belongs to. (d) How are porcupines different from hedgehogs and echidnas?

eBook plus

11 Use the Platypus weblink in your eBookPLUS to look for facts about where the platypus is found, what it eats and what sort of home it makes. Complete a poster that includes diagrams, sketches, a map and, if possible, pictures.

4 Classification 101

4.7

pREscRibEd focus AREA current issues, research and development

Australian scientists at work Some Australian scientists are hard at work finding out more about the unique mammals of Australia and their ancestors. Among them are Julie Sharp, Christophe Lefevre and Kevin Nicholas at the University of Melbourne and KE Hopper and HA McKenzie at the Australian National University. These teams of scientists have been studying the composition of the milk produced

by various mammals. Their research has shown that the milk of monotremes is quite different from the milk of other mammals, including marsupials. This suggests that marsupials are probably more closely related to placental mammals than to monotremes. John Magee and Michael Gagan from the Australian National University have been searching for

Epoch

Some marsupial fossil finds and events

(millions of years ago)

Most of the large Pleistocene marsupials became extinct about 15 000 30 000 years ago.

PLEISTOCENE 1.64 0.01 mya

Many giant browsing marsupials became extinct; there were grazing kangaroos and lots of diprotodons.

Lots of marsupial fossils of this age were found in South and North America.

Dinosaurs became extinct about 65 million years ago.

OLIGOCENE 35.5 23.5 mya

EOCENE 56.5 35.5 mya

PALAEOCENE 65 56.5 mya

A timeline of some marsupial fossil finds and major mammal events

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Lots of marsupial mammals were living in Australia and South America.

MIOCENE 23.5 5.2 mya Tertiary period

First Australian marsupials occurred about 23 million years ago. Diprotodons and a relative of pygmy possum fossils were found in Tasmania.

Aborigines arrived in Australia about 55 000 years ago.

Homo habilis, the earliest known human, appeared in East Africa.

PLIOCENE 5.2 1.64 mya Cenozoic era

Primitive marsupial mice and tapirs were found at Lake Eyre, South Australia and diprotodons at Bullock Creek, Northern Territory.

Major mammal events

Humans investigate Earth s history.

HOLOCENE 0.01 present

uaternary period

Present

an answer to a question that has baffled scientists for a long time: Why did the megafauna become extinct? A number of theories have been put forward. Some scientists believe that humans played a part. Australia s megafauna disappeared around the time that humans first arrived in Australia. Aborigines may have hunted the large animals for food, or they may have brought

First marsupials appeared in Australia. First primates appeared.

Swimming and flying mammals appeared.

More mammals appeared after dinosaurs became extinct.

diseases with them that caused the megafauna to become sick and die. Perhaps the fires they lit as part of their hunting practices played a part in the large animals disappearance. Another theory is that the climate changed; it became drier and the vegetation changed so that the megafauna s habitat changed and their food supply dwindled. Magee and Gagan analysed the shells of ancient emu eggs and the teeth of wombats to find out if the diet of these animals changed over the past 140 000 years. They found that the type of plants they fed on changed significantly around the time that humans first arrived

in Australia. Nutritious grass was replaced by shrubs and less nutritious vegetation. Emus and wombats survived because they adapted to the change in diet. The giant bird Genyornis became extinct because it could not adapt to a different food source. Since the climate did not change at that particular time, the researchers suggested that the fires lit by early Aborigines caused the vegetation to change and resulted in the eventual extinction of many species of megafauna. The research does not support the theory that the megafauna died out as a result of being hunted by humans or due to the introduction of disease by humans.

The work of Magee and Gagan is bringing us one step closer to finding out why Genyornis became extinct.

Activities REmEmbER 1 Name a female Australian scientist described on these two pages and describe one piece of research she has been involved with. 2 outline three theories that have been put forward to explain why the megafauna became extinct.

Think 3 Magee and Gagan s work has provided evidence that supports the hypothesis that fires lit by humans probably contributed to the extinction of the megafauna. Explain what the terms hypothesis and evidence mean. 4 Scientists have discovered more evidence relating to the extinction

of the megafauna. identify which theory each of the following groups of evidence supports. (a) Megafauna fossils have been found. Marks resembling those caused by spears and other cutting instruments could be seen on some of the bones. (b) The discovery of fossilised pollen grains shows that many parts of Australia were covered by rainforest when the megafauna roamed Australia. As rainforest species became extinct, they were replaced by grassland and shrubland better suited to dry conditions.

AnAlysE And EvAluATE 5 interpret the timeline on the opposite page to answer the following questions.

(a) List the seven epochs in the table in order of most recent to least recent. (b) In which epoch did marsupials appear in Australia? How do we know this? (c) Earth s greatest ice age was in the Pliocene epoch. When was this? What other events occurred then?

icT 6 Use the internet to find more examples of Australian megafauna and prepare two PowerPoint slides about one of these examples (or one of the examples discussed on these two pages). On one slide, include a picture of what the animal may have looked like. On the other slide, include any interesting facts you find, such as the size of the animal and its diet.

4 Classification 103

4.8

Invertebrates The main characteristic of invertebrates is that they don t have a backbone. Many have an exoskeleton a skeleton on the outside of their body. Some have no skeleton at all. Some, like sea stars, have a skeleton (but no backbone) inside their bodies.

No-one knows how many species of animals there are on Earth. What is known for sure is that most of them are invertebrates. The dichotomous key below describes some of the characteristics of the main groups of invertebrates.

INVERTEBRATES

Paired, aired, jointed legs

No legs

ARTHROPODS

Body covered with a shell or rough, spiny skin

Soft outer body

Soft body, usually covered with a shell

Body covered with a rough, spiny skin

MOLLUSCS

ECHINODERMS

Spongy body with holes PORIFERA

Arthropods • Body divided into segments • Exoskeleton • Paired, jointed legs • Most have antennae • Include centipedes, spiders, crabs, ants, grasshoppers, moths

Molluscs • Most have a shell • Soft body, not divided into segments • No legs, but may have tentacles • Have a strong foot muscle to help them move • Include oysters, octopus, scallops, slugs, snails

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Has tentacles CNIDARIANS

Echinoderms • (pronounced ee-KAI-noderms) • Most have a soft body over an internal skeleton • Rough, often spinecovered skin • Body has a five-part pattern • Move through water by taking water in and pushing it out of tubes in their bodies • Include sea stars, sea urchins, sea cucumbers

Porifera • Spongy body with no body organs or tissue • Exoskeleton made of fibres or pointed needles • Water and food enter through tiny pores (holes) in body • Wastes pass out through one big opening • Include barrel sponges, glass sponges, tube sponges

Cnidarians (pronounced nyDAIR-ee-ins the C is silent) • Hollow, soft body • No body organs • Take in food and pass out waste through one opening • Have tentacles containing stinging cells, which fire shots of toxin • Include box jellyfish, sea anemone, Portuguese manof-war, coral

The largest invertebrate is a mollusc called the giant squid. its scientific name is Architeuthis dux. it lives in the very deep parts of the ocean. its eyes are as large as soccer balls. its beak-like mouth can cut through steel cables. The giant squid can be as long as 18 metres. Two of its ten tentacles are much longer than the others. These are used to catch food. in 1966, two lighthouse keepers in south Africa watched a giant squid wrap its tentacles around a baby whale to drown it. The whale s mother could do nothing to save her calf.

The cockroach is an amazing insect. it has been around for about 350 million years. if you cut off its head, it will stay alive for about a week. it dies only because it has no mouth to drink through. it can run faster than any other insect almost 4 kilometres per hour. it can also change direction very quickly. if a cockroach loses a leg, a replacement will appear next time it sheds its exoskeleton. Body without holes

Has no tentacles

Body segmented internally

Platyhelminthes (pronounced plat-ee-hel-MIN-theez; also known as flatworms) • Soft, flat, usually unsegmented bodies • No exoskeleton • Mouth but no anus • Include tapeworm, fluke

Body not segmented internally

ANNELIDS orm-shaped body Worm-shaped

Flat body

NEMATODES

PLATYHELMINTHES

Annelids (also known as segmented worms) • Internal segments with some repeated organs • Soft bodies with an obvious head • No exoskeleton • Mouth and anus • Include earthworms, leeches

Nematodes (also known as roundworms) • Soft, unsegmented bodies • No exoskeleton • Worm-shaped • Mouth and anus • Include threadworms, roundworms

4 Classification 105

Arthropods About 80 per cent of invertebrates are arthropods. Mosquito The insect is the most common arthropod. There are about six million known insect species. Many insects pollinate flowers. Some provide us with food (for example, bees provide honey). Insects are a food Spider source for many animals such as fish, birds and other insects. Some insects feed by chewing; others, like the mosquito, suck up their food (sometimes human blood!) through a long thin tube called a proboscis. The proboscis of some insects rolls Crab up at the end when not in use (a bit like a party whistle). All insects have three pairs of legs. An insect s legs are connected to the middle section of its body, called a thorax. Like the mosquito, all other insects have: Centipede •   an exoskeleton •  a body made up of three segments head, thorax and abdomen •  one pair of  Millipede antennae. Most insects smell using their antennae. (Some insects use their feet to taste things.) •  internal tubes that end in openings in their sides, through which they breathe. The other arthropods shown in this column are not insects. The spider, crab, centipede and millipede all have more legs than insects. There are also other significant differences.

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InveStIgAtIon 4.3 What body features can i see on an insect? You will need: preserved or freshly killed cockroach or grasshopper hand lens or binocular microscope disposable gloves probe

Antenna

Head Mouth Leg

◗ Place the insect upside down on a

viewing slide. With the unaided eye, see if you can identify all the body parts shown in the diagram on the right.

Wing

◗ Try to identify the three main segments of

Thorax

the insect the head, the thorax and the abdomen. Remember that the insect s legs are attached to its thorax.

Cerci

Abdomen

◗ Some insects have cerci, which look like

antennae on the rear of the insect. The cerci of a cockroach are very large. They detect the tiniest motion and help warn the cockroach of approaching danger. Some insects have cerci that are more like stumps than hairs. The cerci of some insects are too small to see or are not present at all. ◗ Now use a hand lens or binocular microscope to look at the back legs. Look

closely at the hair-like projections. ◗ Use the hand lens or binocular microscope

Wing

to look at the head of the insect. ◗ Insects breathe through tiny holes called

spiracles. Look at the side of your insect with a hand lens to see if you can find a line of spiracles. You are more likely to see these on a grasshopper.

Antenna Spiracle

Eye

Abdomen

◗ Look at one of the eyes of the insect.

There are many lenses in each eye. (You have only one in each eye.)

Mouth

◗ Hold the insect with two hands.

Thorax

Leg

Without snapping it in two, see if you can gently bend the tail end of the body sideways (not upwards) towards the head.

discussion 1

Does your insect have cerci that you can see with a hand lens? If it does, sketch them.

2

Based on what you see without the hand lens, sketch the detail of one of the insect s back legs.

3

What purpose do you think the hair-like projections serve on your insect?

4

Does your insect have a proboscis or chewing mouthparts? Draw a labelled diagram of the insect s feeding parts.

5

How do you think these extra lenses in the eyes might help the insect s vision?

6

What feature of the insect makes it difficult to bend its body?

8 The key shown on pages 104 5 is just one of many possible dichotomous keys used to classify invertebrates into their groups. Create a different key that starts as follows:

Activities REmEmbER 1 Five animals are shown in the left-hand column on the opposite page. construct a table listing the name of each animal, whether it is an insect and, for those that do not belong to the insect group, a feature that makes that animal different from insects.

Invertebrates

2 classify each of the following animals into one of the invertebrate groups shown on pages 104 5. (a) Spider (b) Leech (c) Sea star (d) Moth

Segmented body

Body not segmented

Test your key by using it to classify a snail, a starfish and an earthworm. Does your key work?

3 outline the main characteristics of insects.

Think 4 A snail is a mollusc; so is the giant squid. In what ways are they alike and in what ways are they different? 5 (a) Use the key below to classify the five arthropods shown in the left column on the opposite page. (b) Explain why the key below is not a dichotomous key. 6 Use the dichotomous key on pages 104 5 to describe the characteristics of coral, earthworms, flukes and centipedes. 7 If you found an animal with a soft, segmented body, but no legs or tentacles or hard external covering, how would you classify it, based on the data given in the dichotomous key on pages 104 5?

invEsTiGATE 9 Your teacher will provide you with preserved specimens or pictures of invertebrates. Use the key on pages 104 5 to classify them. eBook plus

10 Use the Giant squid and Cockroach weblinks in your eBookPLUS to discover more about these amazing creatures.

ARTHROPODS

Legs on every segment except head and last segment

Legs only on thorax

1 pair of legs on each segment; flattened body

2 pairs of legs on each segment; tubular body

3 pairs of legs

4 pairs of legs

5 or more pairs of legs

CHILOPODS

DIPLOPODS

INSECTS

ARACHNIDS

CRUSTACEANS

4 Classification 107

4.9

the other kingdoms Most of the living things that we recognise are plants or animals. But some of the most spectacular and unusual living things belong to the other three kingdoms of living things Kingdom Fungi, Kingdom Monera and Kingdom Protista. Within these lesser known kingdoms are organisms that can keep us alive, make us sick or even kill us.

kingdom fungi Fungi come in an amazing variety of shapes and colours. Perhaps the most familiar are the mushrooms we eat. But fungi also include toadstools, truffles, mould, mildew and yeast. Fungi used to be classified as plants. However, unlike plants, they have no true roots, leaves, stems or flowers. Also, they do not contain chlorophyll. This means they cannot make their own food. Instead, they produce chemicals to break down food from outside sources. The broken-down food is then absorbed into the fungi. Different sorts of fungi feed on different sorts of food. Some grow

on or in dead animal or plant matter (such as vegetable scraps, cow dung and decaying fruit) and slowly break it down (or decompose it). Some grow on or in living organisms. Such fungi are called parasites. Fungi grow from tiny spores released by a parent fungus. These are blown through the air, or carried by animals. Some fungi have interesting ways of releasing their spores. The Pilobolus, which lives in cow dung, releases its spores by exploding. Spores can be shot up to two metres high by the force of the explosion, which is set off by sunlight. Some fungi cause plant diseases such as stem rot, and painful infections such as tinea and ringworm. The antibiotic penicillin is made from a fungus. Yeast, which is used in making bread and beer, is a fungus.

did you know that some toothpaste contains the remains of lots of crushed diatom shells? When diatoms die, their microscopic shells pack down in layers to form diatomaceous earth (which is used in toothpaste). This is why toothpaste is a bit gritty.

under the microscope Members of two of the kingdoms Monera and Protista are generally so small that they can be seen properly only under a microscope. To see some monerans you would even need to use the more powerful electron microscope.

kingdom monera Monerans are thought to be the first form of life to exist on Earth. They are very simple organisms consisting of one cell without a nucleus. They are everywhere in water, in soil, in the air and in your body. You might know them as bacteria. Monerans can be both helpful and harmful. Some cause illnesses such as cholera and pneumonia. Some cause tooth decay. Some, such as Salmonella, can give you

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food poisoning. On the positive side, other monerans that live in your intestine help you to digest food and make vitamins. Others are used to make foods such as yoghurt and vinegar. Cyanobacteria, sometimes called blue-green algae,, are another member of Kingdom Monera. Like some plants, this group makes its own food using photosynthesis. Bacteria are classified by their shape. Some are shaped like rods, some like spirals and some like spheres (shown (sho at right).

kingdom protista

InveStIgAtIon 4.4

Protists are made up of only one cell. Unlike bacterial cells, the cells of protists have a nucleus. Some protists (such as diatoms and Euglena) have features that are a bit like plants. Euglena, for example, can make its own food using photosynthesis, like a plant. Other protists, such as the blob-like Amoeba and Plasmodium, which causes malaria, are more animal-like. They can move and need to ingest food.

how do i classify lichen? You will need: piece of lichen (You will find it growing on rocks and tree trunks in colder, wetter areas, especially towards the tops of ranges and hills.) stereomicroscope probe

An amoeba animal-like, but only one cell

◗ Look carefully at the lichen

under a microscope.

Activities

◗ Identify any true roots, stems,

leaves or flowers.

REmEmbER

◗ Identify any thread-like parts.

1 Copy and complete the following table. Fungi Are they unicellular or multicellular?

Monera Protista Plantae

Animalia

Some are unicellular and some are multicellular.

discussion 1

Describe the appearance of the lichen. Can you see two different sorts of organism?

2

Lichen is actually made up of a fungus and an alga, growing together. Which part do you think is the fungus, and which the alga? Why?

3

What benefits do you think the algal cells in lichen provide for the fungus part?

4

What benefits do you think the fungus provides for the algal cells?

5

How would you classify lichen? Why?

6

What does this suggest about the difficulties that scientists sometimes face in trying to classify organisms?

Do their cell(s) contain a nucleus? Do they photosynthesise?

Some do Some do

Give two examples.

Think 2 Use the information in the table above to construct a dichotomous key for the five kingdoms. 3 In the sixteenth century, only two kingdoms were recognised: animals and plants. Organisms that could move and needed to ingest food were called animals. Organisms that could not move and could photosynthesise were classified as plants. (a) Explain why it is difficult to classify mushrooms and mould into either of these groups. Which kingdom do they belong to now? (b) Explain why the kingdoms Protista and Monera had not been discovered in the sixteenth century.

4 Classification 109

4.10

pREscRibEd focus AREA classification in other cultures

Is it a bird? Is it a plane? no, it s a yakt! When scientists come up with a classification system, they base it on features that are important to them. For example, the way we classify vertebrates into their major groups is based mostly on their body covering and their mode of reproduction. In some cultures, other features are a lot more important, so living things are classified using different criteria. The Karam people of Papua New Guinea live in a rainforest environment. They have a different

Cassowary

Activities REmEmbER 1 When classifying organisms, which features do scientists mostly rely on? 2 In which group would a Western scientist place both the cassowary and the magpie? 3 Do the Karam people put the cassowary and the magpie in the same group? Explain your answer.

Think 4 Explain why scientists classify the masked finch, long-tailed finch and double-barred finch as

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classification system from ours. It includes a group called yakt, which is made up of flying animals such as birds and bats. The cassowary, a large flightless bird, is not classified as a yakt. It is classified as a kobity because it walks on two legs and does not fly. Some Australian Aborigines may also use different criteria to classify living things. One important difference is that scientists try to give a name to everything. When Western scientists discover a new species, they give it a unique name. In traditional Aboriginal culture, only things that have a special use or are in some other way significant to humans tend to be named. Some organisms that scientists classify as belonging to different species have the same Aboriginal name. For example, the masked finch, long-tailed finch and doublebarred finch are all called lidjilidji by the Yolngu people of the Milingbi. belonging to different species. (Hint: Look at the definition of a species on page 93.) 5 In the English language, we classify things using words that are not based on scientific classification. For example, we classify some plant parts as vegetables. According to scientists, the main parts of plants are roots, stem, leaves, fruit and flowers. (a) Which part of a plant is each of the following vegetables? tomato, lettuce, carrot, capsicum, asparagus, celery stick, potato, beans, Brussels sprout (b) How would you explain the difference between a fruit and a vegetable to the Karam people?

Some Aboriginal words refer to different groups of organisms depending on the age of the person using that word. When the word warrakan is used by children up to 10 years old, it means large birds. Children call small birds djikay. Teenagers and young adults on the other hand use the word warrakan to refer to both large and small birds. For older adults, the word warrakan can refer to large land animals, reptiles, bats, echidnas or birds.

Bat

(c) Justify why it is difficult to define the term vegetable . 6 Explain why Yolngu people of the Milingbi might classify the masked finch, long-tailed finch and doublebarred finch as belonging to the same species. 7 The word miyapunu is used by some adult Aboriginal men for turtles, dugongs and dolphins and whales. (a) In which vertebrate group would you classify each of these animals? (b) propose why all the animals may be classified in the same group by some cultures. (Hint: Think about the similarities between these animals.)

LooKIng BACK 1 Match the clues in the first column of the table below with the correct terms in the second column.

7 When scientists discover a new organism they give it a unique scientific name. Describe how that name is created.

Clues

8 Define the term species .

Terms

(a) These animals have no backbone.

A Field guide

(b) These mammals lay eggs.

B Exoskeleton

(c) These mammals have pouches.

C Invertebrates

(d) Insects and spiders belong to this group.

D Marsupials

(e) Flatworms belong to this group.

E Proboscis

(f) This group of invertebrates contains internally segmented worms.

F Porifera

(g) An animal with a backbone

G Reptiles

(h) Snails belong to this group of invertebrates.

H Monotremes

(i) Sponges belong to this group of invertebrates.

I Key

(j) These mammals have a placenta.

J Arthropods

(k) Snakes and lizards belong to this group.

K Platyhelminthes

(l) This is used to identify wildlife.

L Vertebrate

(m) The tough, external skeleton of insects

M Placentals

(n) The internal skeleton of vertebrates

N Annelids

(o) A monotreme with a duck-like bill

O Platypus

(p) Insects may have this to suck up nectar, sap and blood.

P Endoskeleton

(q) This unlocks the door to classification.

Q Amphibian

(r) The adults have lungs and live on land, whereas the young have gills and live in water.

R Molluscs

9 Explain why a tiger and a lion do not belong to the same species. 10 Compare an endoskeleton with an exoskeleton. 11 Outline the features of vertebrates. 12 Identify one Australian scientist and outline an investigation this scientist has been involved with. 13 Classify the following invertebrates using the key on pages 104 5. (a)

(b)

(c)

(d)

15 Demonstrate, using at least one example, that the classification system used by Western scientists is not adopted by all cultures.

2 Outline the seven characteristics of living things. 3 Explain why the Asimo robot is not a living organism. 4 Explain why it is useful to classify organisms. 5 Identify the seven levels of classification in order from the highest level to the lowest level. 6 Use the key shown below to classify the people to the right of the key. 1. Glasses ........................................ Go to 2 No glasses .................................. Go to 3 2. Female .............................................Anna Male ...................................................Tom 3. Nose ring.........................................Emily No nose ring ............................... Go to 4 4. Beard ............................................. Jason No beard ...................................... Jossie

(a)

(b)

(d)

(c)

(e)

4 Classification 111

14 Construct a dichotomous key to classify the aliens shown below.

TEsT youRsElf 1 Identify which of the following lists contains only living things. A Tree, bird, crystal, orange B Dog, rose, book, caterpillar C Duck, snake, wattle tree, fish D Coin, jellyfish, diamond, human (1 mark) 2 Identify which group of vertebrates consists of animals that have moist skin and breathe using gills when fully developed. A Reptiles B Amphibians C Mammals D Fish (1 mark) 3 Identify which kingdom moss belongs to. A Animalia B Plantae C Fungi D Protista

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4 Identify which group of mammals the koala belongs to. A Placentals B Monotremes C Marsupials D Megafauna (1 mark) 5 Compare the following groups of organisms. (a) Birds and reptiles (b) Vertebrates and invertebrates (c) Monotremes and placental mammals (d) Amphibians and fish (e) Animals and plants (f) Fungi and plants (g) Monera and protista

work sheets (1 mark)

4.8 Classification puzzles 4.9 Classification summary

(6 marks)

StUDY CHeCKLISt

ICt

characteristics of living things

eBook plus

■ describe the characteristics of living things 4.1 ■ define the terms respiration , assimilation , response , growth and reproduction 4.1 ■ interpret and construct dichotomous keys including branching keys, tabular keys and circular keys 4.2, 4.3, 4.4, 4.8, 4.9

SUMMARY

interactivities Time Out kingdoms This exciting interactivity tests your ability to classify a series of the world s living creatures into their correct kingdoms. You must answer quickly before your time runs out.

levels of classification ■ ■ ■ ■ ■ ■

explain why biologists classify living things 4.3 describe the hierarchy of classification 4.3 distinguish between the five kingdoms 4.3 distinguish between vertebrates and invertebrates 4.4 describe the features of vertebrates 4.5 classify vertebrates as birds, mammals, reptiles, amphibians or fish based on their characteristics 4.5 ■ distinguish between placental, monotreme and marsupial mammals 4.6

other groups ■ classify invertebrates into their phyla using a dichotomous key

4.8

Searchlight ID: int-0204

■ outline the characteristics of arthropods 4.8 ■ distinguish between the different classes of arthropods

4.8

■ describe the characteristics of fungi, monerans and protists

4.9

■ describe some useful and harmful effects of fungi and bacteria

4.9

current issues, research and development ■ describe research carried by Australian scientists in the field of taxonomy

4.7

■ define the term megafauna 4.6 ■ outline some theories that have been proposed to explain the extinction of many species of megafauna

4.7

The history of science ■ describe examples of classification systems used by other cultures

4.10

4 Classification 113

5

Cells

Microscopes allow us to zoom in on life. The images on these pages were produced using a scanning electron microscope and then coloured. At school, you will use a light microscope, which enables you to see the cells that make up living things. Some living things are just one cell. Others are made up of many different types of cells of various sizes and shapes. Each type of cell has a particular job to do to keep the organism alive. The cells of animals are quite different from those of plants, and plant cells contain parts that are not found in animal cells. You will see this and a lot more by looking through the microscope.

In this chapter, students will: 5.1 ◗ use a microscope to examine

prepared specimens 5.2 ◗ learn about the history of microscopy 5.3 ◗ identify the parts that make up cells 5.4 ◗ prepare specimens for viewing under

the microscope 5.5 ◗ examine the differences between

unicellular and multicellular organisms 5.6 ◗ investigate different types of animal

cells 5.7 ◗ investigate different types of plant

cells 5.8 ◗ investigate tissues and organs 5.9 ◗ discuss stem cell research.

Electron micrograph of an insect s head

Who am i? Microscopes are responsible for opening a whole new world to us. They have allowed us to see beyond our own vision. The more developed these microscopes become, the more detail and wonder we are able to observe but often, rather than answering our questions, they provide us with many more. The three photos at right show parts of different animals. They were taken with a scanning electron microscope, which allows us to see more detail of the surface of specimens. 1. Look carefully at the photos of each animal part and think about: (a) what they could be (b) what they may do (c) which animals they may belong to. 2. Discuss your suggestions with your partner, writing all of the details that you have both observed on a sheet of paper. 3. Two of these photos show parts of one type of animal, and the other one is of a different animal. Does that information change the way that you look at the details? Which animal do you think two of the parts belong to? Brainstorm to decide which animal the other part could belong to. 4. Suggest other sorts of information that may be helpful in determining which animals these parts belong to and what they are used for.

5.1

Using a microscope Microscopes make small objects appear bigger. With a microscope you can zoom in and see the cells that make up living things. You can see the features of tiny creatures such as fleas and ticks. Even everyday objects, such as paper and onion skin, can take on a completely different appearance when viewed under a microscope.

Types of microscopes There are two main types of microscopes: light microscopes and electron microscopes. Light microscopes are used in schools. They pass a beam of light through the sample. Your school may have two types of light microscopes: monocular microscopes and binocular microscopes. Monocular microscopes have only one eyepiece so you use only one eye to

look down the microscope. The specimen needs to be thin and placed on a piece of glass called a microscope slide for viewing. A binocular microscope has two eyepieces, so you use both eyes to look at the object. Most school binocular microscopes are stereomicroscopes. The specimen does not need to be thin and it does not have to be on a microscope slide. These microscopes are often used for dissections. Electron microscopes are not usually found in schools because they are very expensive. They pass a beam of particles called electrons through the sample. They can magnify objects a lot more than a light microscope and provide much greater detail. Preparing samples for viewing can be quite difficult though; for example, the sample may need to be coated with a thin layer of metal.

Some comparisons between light microscopes and electron microscopes Magnification (how many times bigger)

Type of microscope

Resolution (how much detail we can see)

Advantage(s)

Disadvantage(s)

Examples of detail that can be seen

Light microscope

Up to ×1500

Up to about 500 times Samples prepared better than the quickly; coloured stains human eye can be used; living cells can be viewed.

Limited visible detail

Bacteria; shape of cells; some parts inside cells

Electron microscope

×1 000 000

Up to about 5 million times better than the human eye

Only dead sections can be viewed.

All parts of cells; viruses

Eyepiece

High magnification and resolution

Source of electrons Beam deflectors

Tube Condenser lens Projector lens Lens Focus knob

Detector

Light Specimen Stage

Switch

Stereo light microscope

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Core science | stage 4 Complete course

Image on TV screen

Scanning electron microscope

Using a microscope Microscopes make small objects easier to see. The microscopes commonly used in schools can magnify objects up to 400 times. The total magnification of a microscope can be calculated by multiplying the magnification of the eyepiece lens by the magnification of the objective lens. For example, a 10× eyepiece and a 20× objective lens would provide 10 multiplied by 20 = 200 times magnification. Microscopes are very expensive and are easily damaged if they are not handled carefully. Light travels through microscope to eye Eyepiece lens (ocular)

Body tube

Coarse focus knob

Fine focus knob

Rules for handling a microscope: • Always use two hands when carrying a microscope: one on the arm of the microscope and the other under the base. • Place the microscope securely on a flat surface, away from the edge. • Never shine sunlight directly up the microscope tube. You could damage your eyes. • Use only lens tissues to clean microscope lenses: never use your fingers. More hints for using a microscope: • Look down the microscope with one eye, but keep both eyes open don t squint. • Begin focusing a microscope on the lowest magnification. • Focus a microscope by beginning with the coarse focus. Look from the side and adjust the objective lens so that it is just above the microscope slide. • Turn the coarse focus knob to move the tube up until the object comes into view. • Turn the fine focus to make the image of the object as clear as possible.

Revolving nosepiece Objective lenses Stage slide clip

Slide

Iris adjustment Stage

Field of view 4 mm (4000 Mm) magnification x40

Mirror

Light Base

Monocular light microscope

The microscopes at your school may look slightly different from this one. Some microscopes have a built-in light. Microscopes with built-in lights do not have a mirror and do not require a separate microscope lamp.

Field of view 1.6 mm (1600 Mm) magnification x100

Field of view 0.4 mm (400 Mm) magnification x400

Field of view your window to a tiny world: as the field of view gets smaller, the magnification gets larger.

5 Cells

117

the lowest power objective lens (smallest magnification).

InvestIgatIon 5.1 getting into focus with an e You will need: 1 cm square piece of newsprint containing the letter e monocular light microscope microscope slide clear sticky tape 1 cm square piece of colour picture from a magazine or newspaper a hair salt

◗ Using the guidelines on the previous

page, get the paper into focus using the coarse focus knob and

◗ Change to a higher level of

3

Record the magnification that you are using, and estimate how much of the viewed area is covered by the letter e at this magnification.

4

Suggest what the letters P and R would look like under the microscope. Sketch your predictions, and then view examples of these under the microscope. Were your predictions correct?

5

Summarise your results in a table with the following headings: Object , Magnification , Pencil sketch , Description .

magnification by rotating to a higher power objective lens. ◗ Using sticky tape, stick a small

section of a colour photograph, a hair, some salt crystals and any other objects your teacher has provided onto microscope slides. View each specimen under the microscope on low power.

DiScUSSion 1

In which direction did the paper under the microscope move when you moved the slide

RemembeR 1 compare the following microscopes. (a) Light microscope and electron microscope (b) Monocular microscope and stereomicroscope 2 Recall the following steps for using a microscope in the correct order. (a) Adjust the fine focus. (b) Place the slide on the stage. (c) Twist the revolving nosepiece to switch to the high-power objective lens. (d) Adjust the coarse focus. (e) Select the lowest power objective lens. (f) Use the fine focus knob as necessary to focus the image.

Think 3 When you are looking down the microscope, identify what happens when you move the microscope slide (a) to the left, (b) to the right, (c) towards you and (d) away from you. 4 If you are using an eyepiece with a magnification of ×10 and an objective lens of ×10, calculate how many times the specimen viewed under the microscope will be magnified. 5 If a specimen is 1 mm long, how long will it appear if it is magnified 100 times? 6 If a specimen takes up the entire field of view at ×100, calculate how much of it will be seen at ×400.

Core science | stage 4 Complete course

What does the letter e look like under the microscope? Draw a pencil sketch of what you see.

have a letter e in focus.

activities

118

2

◗ Carefully move the slide until you

◗ Carefully stick the 1 cm square of

newsprint onto a clean microscope slide using sticky tape.

(a) towards you or (b) to the left?

7 (a) Sketch a line diagram of your school microscope and label as many of its parts as you can, using the diagram on page 117 to help you. (b) identify how your school microscope differs from the one shown on page 117. 8 Copy and complete the table below. Ocular lens (eyepiece)

Objective lens

Magnification

×5

×5

×25

×5

×10

×10

×100 ×40

×400

inveSTigATe 9 Use a stereomicroscope to look at a range of small objects such as a small flower, a dead insect, some salt or sugar crystals and a blade of grass. Describe the advantages and disadvantages of this type of microscope over a monocular microscope. eBook plus

10 Test your knowledge of the functions of different parts of a microscope by completing the Microscope parts interactivity in your eBookPLUS. int-0205 11 Use the Electron microscope weblink in your eBookPLUS to view some electron micrographs. Analyse how the images produced by an electron microscope are different from those produced by a light microscope.

5.2

a whole new world The invention of the microscope just over 400 years ago had a huge impact on biology. It became possible to see cells, the building blocks of living things, and whole kingdoms of living things were discovered. As microscopes improved, biologists could learn a whole lot more about cells and microbes.

eBook plus

eLesson

Inside cells Learn about cells and organelles in this animated video lesson.

The discovery of cells In the seventeenth century, Robert Hooke looked at thin slices of cork under a microscope (= very small + view) that he had designed himself. He observed small boxlike shapes inside the cork. He called the little boxes that he saw cells. Microscopes opened up a whole new world that had never been seen before. Using microscopes to carefully observe different living things Robert Hooke showed that they also were made of these tiny basic units. As the magnification provided by microscopes increased, it could be seen that, although the basic structure of cells was similar, there were quite a few differences. Different groups of organisms often contained different types of cells. It was also discovered that different types of cells could be found within an individual organism.

eles-0054

van Leeuwenhoek was the first person to observe bacteria, red blood cells, sperm cells and muscle fibres under the microscope. he started his working life as a draper, selling fabric. he used magnifying lenses to count the threads in cloth. he became interested in microscopy after seeing a book by Robert hooke with illustrations and descriptions of specimens observed using a microscope. van Leeuwenhoek made many microscopes during his life, and he observed all kinds of specimens, including plaque he scraped off his own and other people s teeth. he was meticulous in recording his observations and made detailed descriptions of specimens. he was not very good at drawing though, so he employed an illustrator to complete many of his diagrams. Some of the personal attributes that made him a successful microbiologist included a natural curiosity and very good eyesight, the patience and persistence needed to grind the highquality lenses for his microscopes and the attention to detail required to painstakingly record all his observations.

An early microscope used by Robert Hooke A replica of Van Leeuwenhoek s microscope

5 Cells

119

Little, littler, littlest 10 m Human height Length of some nerve and muscle cells Chicken egg

1m Unaided eye

0.1 m 1 cm

Frog egg

Light microscope

1 mm

Electron microscope

Bacteria and the cells of animals and plants are tiny. Most plant and animal cells are less than 0.0001 m long. It is not convenient to express their size in metres or even millimetres. Microscopic things are usually measured in micrometres (µm, also called microns). One micrometre = 0.000 001 m (or 10 6 m).

Hair width

100 Mm

Plant and animal cells 10 Mm Most bacteria 1 Mm Smallest bacteria

100 nm

Viruses

10 nm

Proteins

1 nm Small molecules Atoms

0.1 nm

1 millimetre = 1/1000th of a metre 1 micrometre = 1/1 000 000th of a metre 1 nanometre = 1/1 000 000 000th of a metre

1665

Robert Hooke uses the term cell to describe the tiny box-like units in a thin slice of cork.

1683

1600

1675

Antonie van Leeuwenhoek (1 32 1723) discovers unicellular microscopic organisms in stagnant water, which he calls animalcules . (We now call these bacteria.)

Leeuwenhoek discovers bacteria in saliva.

1824

1700

1831

Timeline showing the development of microscope and cell theory

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Core science | stage 4 Complete course

Ren Dutrochet (177 1847) states that all plants and animals are made up of cells.

1839

Theodor Schwann suggests that all animals are also made of one or more cells and that the cell is the basic unit of structure for all living things.

1800

Robert Brown (1773 1858) reports on his observation of the nucleus in both plant and animal cells.

1858

Rudolf Virchow (1821 1 02) suggests that all cells arise from cells that already exist.

activities

7 Antonie Van Leuwoenhoek was very curious. explain how this contributed to his success as a microbiologist.

RemembeR

8 Use the timeline on these two pages to answer the following questions. (a) In which year did Hooke use the term cells to describe his observations of cork slices? (b) What did Virchow suggest in 1858? (c) In which substance did Leeuwenhoek discover bacteria? (d) When did Ruska build the first electron microscope? (e) Recall the differences between cell observations made with a scanning electron microscope and those with a transmission electron microscope.

1 outline why the invention of the microscope had a significant impact on biology. 2 Describe the appearance of the cells that Hooke observed in thin sections of cork. 3 Deduce whether all cells look the same. 4 identify what microbiologists study. 5 Define the term micron .

Think AnD ReASon 6 Use the diagram on the opposite page to answer the following questions: (a) compare the sizes of animal cells and bacteria. (b) identify three things that can be seen with an electron microscope but not a light microscope. (c) Deduce whether you would need a microscope to see a frog egg. (d) Complete the table below.

Size in microns

Object

Size in mm (1 micron = 0.001 mm)

9 Research one of the scientists in the timeline on these two pages and present your information in a poster. eBook plus

Size in metres (1 micron = 0.000 0001 m)

Plant and animal cells Hair (width)

10 Visit the Robert Hooke weblink in your eBookPLUS and investigate why he used the term cells for the little box-shaped structures he observed in cork. What did people think living things consisted of before Hooke s discovery of cells? Write a story about your findings. work sheet

Frog egg

20th century

inveSTigATe

Development of the microscope continues.

1900

PRESENT DA

Ernst Ruska builds the first electron microscope.

Development of: sæ TRANSMISSIONæELECTRON microscopes, which show the internal structures of cells

2000

1933

5.1 History of the light microscope

sæ SCANNINGæELECTRONæ microscopes, which show images of the surface features (often involve coating the specimen with a very thin layer of metal atoms) sæ SUPERFASTæELECTRON microscopy, which enables scientists to capture the movement of atoms (visit the Electron strobe weblink in your eBookPLUS).

5 Cells

121

5.3

Living things are made up of cells When we look at cells with a microscope, we can see that they contain little organs or organelles. There are many different types of organelles, and each organelle has a particular function or job. Plant and animal cells appear quite different and contain different organelles. All plant and animal cells have a cell membrane, cytoplasm and a nucleus at some stage in their life. That s because all plant and animal cells need food for energy, water and a control centre. Plant cells also have cell walls, chloroplasts and vacuoles. Plants need

those extra features in their cells to make and store food, and to keep their shape. Some animal cells have vacuoles, but they are very small. Some organelles are too small to see with a light microscope. They can be seen only with an electron microscope. Mitochondria are organelles that cannot be seen with a light microscope. These are the power stations of cells and are where respiration occurs. During respiration, glucose and oxygen react to form carbon dioxide and water, and energy is released.

Plant cell

Animal cell

Cell membrane The thin layer that encloses the cytoplasm is the cell membrane. It keeps the cell together and gives it its shape. Some substances, such as water and oxygen, can pass through the cell membrane but other substances cannot. The cell membrane controls what enters and leaves the cell. Nucleus The nucleus is the control centre of the cell. It contains DNA in the form of chromosomes and it controls what the cell does and when. Cytoplasm The jelly-like substance inside cells is the cytoplasm. It contains many important substances, such as glucose, that are needed for chemical reactions that occur inside cells. Cell wall The tough covering around plant cells is the cell wall. It gives plant cells strength and holds them in shape. Cell walls are made of a substance called cellulose. Water and dissolved substances can pass through the cell wall. Animal cells do not have a cell wall.

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Core science | stage 4 Complete course

Chloroplasts Chloroplasts are the oval-shaped organelles found only in plant cells. Chloroplasts contain a green substance called chlorophyll. Chloroplasts use energy from the sun to make food. Not all plant cells contain chloroplasts. They are found only in leaf and stem cells.

Vacuole The vacuole is an organelle used to store water and dissolved substances. Vacuoles can look empty, like an air bubble. Plant cells usually have one large vacuole. The mixture inside a plant s vacuoles is called cell sap. The red, blue and violet colours that you often see in plant leaves and flowers are due to the substances stored in vacuoles. Most animal cells don t have vacuoles.

Why are cells so small? Cells have to be very small because they must be able to take up the substances they need and remove wastes quickly. The bigger a cell is, the further the centre is from the edge and the longer it takes to move material in and out. Larger cells also have a smaller surface area to volume ratio. This slows down the movement of substances in and out of large cells. If a cell was too big, it would not be able to take up or remove materials fast enough to support itself, and the nucleus would ould not be able to pass on information and control the whole cell.

Vacuole

When cells die most of the cells in your body don t live for as long as you do. Usually, when they die they are replaced. The cells that make up your skin live for only between 20 and 35 days. Skin cells can replace themselves before they die. Luckily they don t all die at the same time! The dead cells are rubbed off, or just fall from your body. They land on the floor, on furniture and in your bed. in fact, most of the dust that you sweep up or vacuum is actually dead skin cells. Snakes, on the other hand, usually shed their dead skin cells all at once. Young snakes shed their skin every six to eight weeks. Adult snakes shed their skin only once every year or two.

Mitochondrion

Chloroplast Starch granule

Nucleus

activities

A cell viewed under a light microscope (top) and an electron microscope (centre and bottom). Notice that some organelles can be seen only with an electron microscope.

7 explain what happens inside chloroplasts.

RemembeR

8 identify which organelles are found in both animal and plant cells.

1 Define the term organelle . List two examples of organelles.

9 identify which organelles are found in plant cells but not in animal cells.

2 Recall which substance fills a cell. 3 outline why the nucleus is important to a cell. 4 Recall the role of the cell membrane. 5 explain why cells need to be so small. 6 Recall what cell walls are made of.

Think AnD ReASon 10 outline why most plants are green. 11 The cellulose cell wall that surrounds plant cells makes these cells rigid. explain why animals may find it difficult to move if their cells had cell walls.

12 Justify why it is important for animals to be able to move whereas plants can survive without moving about.

cReATe 13 construct a model of a plant or animal cell. Use materials available at home, such as drink bottles, egg cartons, cottonwool, wool, cotton and dry foods. Add labels or a key to indicate all the organelles in your model. work sheet

5.2 Cells and microscopes

5 Cells

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5.4

Zooming in on life Now that you know the names of the organelles found in cells, let s look at them.

InvestIgatIon 5.2 making a wet mount: onion cells Read all the instructions before you begin. You can read more about using a microscope on page 117. You will need: microscope clean microscope slide coverslip dropper bottle of water forceps (tweezers) scalpel toothpick small section of a peeled onion blotting paper CAUTION The scalpel has a sharp blade. Handle it with care. ◗ Use the dropper to put a drop of water on a microscope

slide. ◗ Use a scalpel to peel a small piece of the very thin,

almost transparent onion skin from the inside surface of the onion. ◗ Use the forceps to put the piece of the onion skin into the

drop of water on the microscope slide. ◗ Place a coverslip over the top of the water containing the

onion skin. Use a toothpick to lower the coverslip gently to avoid air bubbles. Use blotting paper to soak up any excess water outside the coverslip. ◗ Prepare another slide of onion skin but, instead of putting

a drop of water on the slide, put a drop of methylene blue on the onion skin before adding a coverslip.

DiScUSSion

124

1

Set the microscope to low magnification (see page 117). What is the total magnification?

2

Draw and label a group of cells. Is your drawing large enough to see clearly?

3

Set the microscope to a higher magnification. What is the total magnification?

4

View the same group of cells using high magnification. Draw them again at this higher magnification. Add any extra detail that you can now see.

Core science | stage 4 Complete course

Sketching what you see under the microscope Some points to remember 1. Use a sharp lead pencil. 2. Draw only the lines that you see (no shading or colouring). 3. Your diagrams should take up about a third to half a page each. 4. Record the magnification next to each diagram. 5. State the name of the specimen and the date of observation. 6. A written description is also often of considerable value. 7. When you are viewing many cells at one time, it is often useful to select and draw only two or three representative cells for each observation.

Staining a specimen Many objects are colourless when viewed down the microscope, so specimens are often stained to make them easier to see. Methylene blue, iodine and eosin are some examples of commonly used stains. Each stain reacts with different chemicals in the specimen. For example, iodine stains starch a blue-black colour. Take care when using these stains, because they can stain you as well!

An example of a sketch of a microscope specimen

This in and this out Useful substances need to move into cells, and waste products need to move out of cells. The cell membrane controls what can enter and leave a cell. Substances such as water and oxygen can pass through the cell membrane. When a substances moves into a cell, we say that it diffuses into the cell. Oxygen diffuses into cells. Carbon dioxide diffuses out of cells. There is a special word for the diffusion of water; when water diffuses in or out of a cell, it is called osmosis.

InvestIgatIon 5.3 InvestIgatIon 5.4

Pond water You will need: light microscope microscope slides coverslips

Peel or squash and stain pond water pipette

◗ Prepare a wet mount of the

pond water on a microscope slide. ◗ Examine the pond water under

the microscope. ◗ Draw sketches and describe

what you see.

You will need: light microscope microscope slides coverslips pipette celery stick, banana water, methylene blue, iodine ◗ Peel a piece of celery skin and

carefully place it on a slide with a drop of methylene blue.

◗ Cover carefully with a coverslip. ◗ Squash a small piece of banana on

a slide and add a drop of iodine. ◗ Cover with a coverslip.

DiScUSSion 1

Record what you see of the banana and celery cells under the microscope.

2

Describe the similarities and differences between your observations of the banana and the celery cells.

5 Cells

125

◗ Put bag A in a beaker of starch

InvestIgatIon 5.5 moving in or out? You will need two 20 cm lengths of dialysis tubing starch solution iodine solution scales 2 beakers

solution. Add enough iodine to the starch solution to produce a dark blue colour. ◗ Put bag B in a beaker of water. ◗ Leave the two bags undisturbed for at least two hours (or overnight). ◗ Weigh the bags again.

5

(a) Starch (b) Water

DiScUSSion

◗ Soak the dialysis tubing in water so

1

that it becomes soft. ◗ Tie a knot at one end of each piece

of dialysis tubing. This will form two small bags.

2

◗ Pour water into bag A until it is one-

3

third full. Pour the same amount of starch solution into bag B and add 10 drops of iodine solution. ◗ Tie a knot at the top of each bag to

4

seal them. ◗ Weigh both bags.

Dialysis tubing allows some substances, but not others, to pass through. Which of the following substances could pass through the dialysis tubing and which could not? What evidence supports this?

Draw up a table to record the weights of the bags before and after being left in the beakers. What happens to iodine when it is added to starch solution? Draw bags A and B in the beakers they were left in. On your diagram, label where blue and yellow colour can be seen. In this experiment, we made a model of a cell. Which part represented the cell membrane?

(c) Iodine 6

Did the mass of the two bags change? What caused it to change?

7

When water moves in or out of cells by osmosis, it moves in the direction that balances the concentrations of substances inside and outside the cell. Use this information to explain why the masses of the bags changed.

6 Make a sketch of these human cheek cells.

activities RemembeR 1 Recall three things you must do when sketching what you see under the microscope. 2 (a) Define the term stain . (b) explain why stains are used. (c) Give two examples of stains you have used in class. 3 Recall which part of a cell controls the movement of substances in and out of the cell. 4 Complete the following sentences: (a) The movement of substances in and out of cells is called ______________. (b) Water moves in and out of cells by ____________.

Think 5 explain what is wrong with each of the diagrams shown below.

7 calculate the total magnification when using a ×10 eyepiece and a ×40 objective. 8 Human cheek cells are about 0.05 mm wide. calculate the magnification used to create the picture above.

inveSTigATe 9 View some prepared slides of human cheek cells and leaf epidermis under the microscope. Draw labelled diagrams of each type of cell.

Nucleus Cytoplasm Cell membrane

(a)

126

x40

Core science | stage 4 Complete course

(b)

x10

(c)

work sheet

5.3 Preparing a stained wet mount

5.5

Revisiting the five kingdoms In chapter 4, you learned that living things can be classified into five kingdoms: Plantae, Animalia, Fungi, Protista and Monera. There are important differences between the cells of organisms belonging to each of the five kingdoms.

One amoeba. Amoebas are unicelluar organisms.

Nucleus divides

Two wo amoebas

Cytoplasm divides

Protista and monera

Unicellular organisms reproduce simply by dividing into two cells. This is called binary fission.

Nucleus Vacuole containing water The food is digested inside the food vacuole. Nutrients diffuse out of the food vacuole into the cytoplasm of the amoeba.

Food (a unicellular organism called a desmid) Ingested food (inside a food vacuole)

An amoeba feeding

Amoeba

Paramecium

100 µm

300 µm

Two of the kingdoms (Monera and Protista) consist of unicellular organisms. When an organism is made of only one cell, that one cell must do all the jobs needed to keep the organism alive. The cell cannot specialise. You could compare this to a single-teacher school where one teacher has to teach all subjects, take phone calls, operate the canteen and write the weekly newsletter. The teacher would need to be good at lots of things but could not become an expert at any one thing. Unicellular organisms reproduce by dividing into two cells using a process called binary fission. The main difference between the protists and the monerans is that protists have a nucleus and monerans do not. Examples of protists include Amoeba, Paramecium and Euglena. Amoebas look like blobs but they can move about. They can engulf food by wrapping themselves around the food. Paramecia have small hairs that beat to allow them to move. Euglenas are interesting; depending on the availability of food and sunlight, they can take in food (like animals) or photosynthesise (like plants).

Euglena

Protists have a nucleus; they include Amoeba, Paramecium and Euglena.

5 Cells

127

Cyanobacterium Monera do not have a nucleus; they include bacteria and cyanobacteria (blue-green algae).

InvestIgatIon 5.6 observing unicellular organisms You will need: microscope slides (preferably with a well) coverslips live paramecium culture yeast culture prepared slides of Amoeba, Euglena and Paramecium If you have a fish tank at school, scrape a sample of algae off the sides.

The plant and animal kingdoms contain only multicellular organisms. Most fungi are also multicellular, but there are some exceptions such as yeast. Most multicellular organisms contain many cells and their cells are specialised for different jobs. For example, red blood cells are very different from muscle cells and sperm cells. Each type of cell has a particular structure that makes it well suited to its particular job. This is similar to a large high school hiring a person with good secretarial skills to run the office, a trained chef to prepare food for the canteen and a teacher with a science degree to teach science. The characteristic that sets plants apart from all other types of organisms is that some of their cells contain chloroplasts, where photosynthesis occurs. Chloroplasts are present in the parts exposed to light, such as leaves and stems. Both fungal and plant cells have a cell wall, but fungi cannot make their own food by photosynthesis. Fungi take in food from their surroundings; the nutrients diffuse into the cell through the cell wall and cell membrane. Animals cannot photosynthesise and most move about to find or catch food to eat. A cell wall would make it difficult to move about so it makes sense that animal cells lack a cell wall.

◗ Put one drop of Paramecium culture on a microscope

slide and cover with a coverslip. ◗ Observe under the microscope using low power at

first, and then increase to high power. ◗ Copy the table below into your workbook and record

50 µm

Bacterium

Plantae, Animalia and Fungi

100 µm

3 µm

Monera includes bacteria and a type of algae called blue-green algae or cyanobacteria. They do not have a nucleus but they do contain DNA. Moneran cells are smaller than all other types of cells. They are believed to be the first type of life forms to have evolved on Earth. Humans, other animals and plants probably all evolved from bacteria.

Plant leaf cell

Human cheek cell

all your observations in the table. ◗ Repeat the steps above using the yeast culture and

the sample of algae from the fish tank. Also, view the prepared slides and complete the information in the table.

Mitochondrion

Organism

Sketch

Description

50 µm

Observations of unicellular organisms Nucleus

Cell membrane Cell wall

Fungal cell

128

Core science | stage 4 Complete course

Some differences in the basic cell design in the five kingdoms Kingdom

Characteristic

Animalia (animals: e.g. lizards, fish, spiders, earthworms, sponges)

Number of cells

Multicellular

Usually multicellular but some unicellular

Most multicellular

Unicellular

Unicellular or multicellular

Nucleus

Present

Present; some fungi have several nuclei per cell

Present

DNA is not contained in a membranebound nucleus.

Present

Cell wall

Absent

Present

Present

Present

Present in some

Large vacuole

Absent

Absent

Present

Absent

Present in some

Chloroplasts

Absent

Absent

Present in leaf and stem cells

Some contain chlorophyll but no chloroplasts.

Present in some

Fungi (e.g. yeasts, moulds, mushrooms, toadstools)

activities RemembeR 1 identify which kingdoms contain only unicellular organisms. 2 Recall the main difference between Protista and Monera. 3 identify which kingdoms contain only multicellular organisms.

Plantae (plants: e.g. ferns, mosses, conifers, flowering plants)

Monera (bacteria and cyanobacteria)

Protista (e.g. algae, protozoa)

8 Recall one example of each of the five kingdoms. 9 Copy the table below and use the diagrams of cells on pages 127 8 to complete it. Type of cell

Kingdom

Size (µm)

Euglena Paramecium Bacterium

4 compare plant and fungal cells. 5 explain the difference between unicellular and multicellular organisms.

Think AnD ReASon 6 construct a dichotomous key to classify living things into the five kingdoms. (Hint: Use the table above.) Use the table above to answer the following questions. 7 identify in which kingdom(s) the cells of an organism: (a) do not have a cell wall, large vacuole or chloroplasts (b) have a cell wall, large vacuole and chloroplasts (c) have a cell wall, but no large vacuole or chloroplasts (d) have a cell wall but lack a membrane-bound nucleus.

Human cheek cell Plant leaf cell Fungal cell 10 construct a column graph of the data shown in the table above. The type of cell should be on the horizontal axis and cell size on the vertical axis. 11 calculate the average size of the cells listed in the table above. 12 List the kingdoms in order from smallest to largest cell size. work sheet

5.4 Cells and the five kingdoms

5 Cells

129

5.6

Cells of all shapes and sizes Your body is made up of many different types of cells. Each type of cell is best suited to its particular function or job.

Muscle cells Muscle cells are long and elastic. Long thin cells can slide further over each other to allow you to move. There are different types of muscle cells. The walls of your 50 blood vessels and parts of your digestive µm system have smooth muscle cells. The muscles that are joined to your bones are called skeletal muscles . Skeletal muscles work in pairs one muscle contracts (shortens) and pulls the bone in one direction while the other muscle relaxes. 10 µm

15

µm

Red blood cells Red blood cells carry oxygen around the body. Their small size helps them move easily through blood vessels. The nucleus in a red blood cell dies soon after the cell is made. Without a nucleus, red blood cells live for only a few weeks. The body keeps making new blood cells to replace those that have died. Red blood cells are made in bone marrow at the rate of 17 million cells per minute! This is why most people can donate some of their blood to the Red Cross without harm. White blood cells, which are larger than red blood cells, are also made in the bone marrow. Their job is to rid the body of disease-causing organisms and foreign material.

130

Bone cells Minerals such as calcium surround your bone cells. The minerals help make bone cells hard and strong. Bone cells need to be hard so that they can keep you upright.

Core science | stage 4 Complete course

m 100 µ

Tail up to 1 m long

Nerve cells Nerve cells are very long and have a star shape at one end. The long shape of nerve cells helps them detect and send electrical messages through the body at the speed of a Formula 1 racing car. There are nerve cells all over your body. They allow you to detect touch, smell, taste, sound, light and, unfortunately, pain.

m 40 µ

Lung epithelial cells The cells that line your nose, windpipe and lungs are a type of lining cell. They have hair-like tips called cilia. These cells help protect you by stopping dust and fluid from getting down your windpipe. The cilia can also move these substances away from your lungs. You remove some of these unwanted substances whenever you sneeze, cough or blow your nose.

30

µm

Adipose tissue cells Some cells store fat. Fat stores a lot of energy for cells to use later. Round shapes are good for holding a lot of material in a small space. Fat cells are mostly found underneath your skin, especially in the chest, waist and buttocks.

Skin cells Special cells line the outside surfaces of your body. These are the cells that form your skin. These cells have a flattened shape so they can better cover and protect your body.

100 µm

45

µm

15 µm

Did you know these facts about human cells? • Hair and nails are made of dead cells, and because they are not fed by blood or nerves you can cut them without it hurting. • A human baby grows from one cell to 2000 million cells in just nine months. • Red blood cells live for one to four months and each cell travels around your body up to 172 000 times.

Sperm Sperm cells have long tails that help them swim towards egg cells. Only males have sperm cells.

Egg cells Egg cells are some of the largest cells in a human body. Their large round shape helps them store plenty of food. Only females have egg cells. When a sperm cell moves into an egg cell, the egg cell is fertilised.

• Some of the nerve cells in the human body can be one metre long. but that s small compared with the nerve cells in a giraffe s neck. They are two to three metres long!

5 Cells

131

DiScUSSion

InvestIgatIon 5.7 Animal cells

what s the difference?

You will need: light microscope prepared animal slides: blood cells, muscle cells, cheek cells, nerve cells ◗ Construct a table like the one below, making it large

1

Which features did the animal cells have in common?

2

In what ways did the animal cells differ from each other?

3

Why are there some features that all cells possess?

4

Find out the functions of the different types of cells examined.

5

Suggest how the shape or size of the cells may assist the cell in doing its job.

6

Suggest reasons for some of the differences observed between the cells.

enough for all of your results. ◗ Use a microscope to observe the prepared slides,

recording your observations in the table as you make them. ◗ Prepare a summary table that describes the similarities

and differences observed between the different cells examined. Source of specimen Animal

Type of specimen Cheek cells

activities

Description of specimen

[Allow as much space as you can; [Describe in words what the draw only two or three cells, in specimen looked like.] pencil, and include magnification and estimated size.]

Type of cell

Shape

(a) Muscle cell

A Disc shaped

RemembeR

(b) Egg cell

B Star shaped with long tail

1 identify which features most cells have in common.

(c) Red blood cell

C Flat

(d) Nerve cell

D Long and thin

2 Describe some ways in which cells may differ.

(e) Skin cell

E Spherical

3 Recall which type of animal cell spends most of its life without a nucleus.

8 explain how the shape of each of the cells in the table above helps the cell do its job.

4 Recall which type of cell is found in the walls of blood vessels.

9 (a) Use the illustrations on pages 130 1 to find the sizes of the following different types of animal cells. Present the data in a table.

5 Describe how the cilia in your nose, throat and windpipe protect your lungs. 6 Recall why egg cells are so large.

Think 7 Match each type of cell in the table above with its shape.

132

Sketch of specimen

Core science | stage 4 Complete course

(i) (ii) (iii) (iv) (v) (vi)

Adipose tissue cell Red blood cell Lung epithelial cell Muscle cell Skin cell Sperm cell

(vii) Bone cell (viii) Egg cell (b) calculate the average size of the cells listed in part (a). (c) construct a column graph showing the sizes of the cells listed in part (a). eBook plus

10 Match each cell with its purpose in the body by completing the Cell jobs interactivity in your eBookPLUS. int-0206

5.7

Focus on plants Plants are made up of different types of cells, each suited to a particular function.

25 Mm

Guard cell

Leaf cells (palisade cells) The main function of leaf palisade cells is to photosynthesise, so they are packed with chloroplasts and are usually green.

65 Mm

Leaf cell

Epidermal cells 150 Mm

Guard cells Guard cells are kidney-shaped cells found on the surface of leaves. They can change shape to either open or close the small hole between them. The small holes, called stomata (or stomates), allow substances such as carbon dioxide to enter the leaf. They also let water out of the leaf. Most plants open their stomata at night; they close their stomata during the day (when it is hotter) to conserve water. 100 Mm

Epidermal cells Epidermal cells are found on the outside of the plant. They form an outer skin for the plant and protect the cells underneath. This explains why they need a flat shape and why they interlock like tiles. Epidermal cells do not usually photosynthesise so they lack chloroplasts. Light needs to pass through them, and they are usually transparent. The cells in the diagram above are onion epidermal cells.

Xylem cells Xylem cells form xylem tubes, which carry water and dissolved minerals from the roots to all parts of the plant. They are made up of dead xylem cells joined end to end. When xylem cells die, the cell walls at each end of the cells dissolve, forming a long straw-like tube. They have thick cell walls with lots of cellulose to make the xylem tubes strong.

Xylem cells

100 Mm

Root hair cell Some of the types of cells found in plants

Phloem cells

300 Mm

Root hair cells Root hair cells absorb water and dissolved minerals from the soil. They have small hairs, called root hairs, on their surface. This increases the surface area of the root cells so that they can soak up water more quickly.

Phloem cells Like xylem cells, phloem cell cells form tubes.Phloem The tubes formed by phloem cells carry the food made in the leaves to all parts of the plant. Phloem cells do not need to die to do this job. The ends of phloem cells have holes and look like sieves.

5 Cells

133

◗ Use a microscope to observe the

InvestIgatIon 5.8 Plant cells in view You will need: light microscope prepared plant slides: leaf epidermal cells, root hair cells, stomata/guard cells ◗ Construct a table like the one

Find out the functions of the different types of cells examined.

5

Suggest how the shape or size of the cells may assist the cell in doing its job.

6

Suggest reasons for some of the differences observed between the cells.

Sketch of specimen

Description of specimen

Which features did the plant cells have in common?

2

In what ways did the plant cells differ from each other?

Leaf epidermal cells

[Allow as much space as you can; [Describe in words what the draw only two or three cells, in specimen looked like.] pencil, and include magnification and estimated size.]

6 (a) Copy and complete the table below using the information in the diagram on the previous page.

activities RemembeR

Type of cell

1 Match each type of cell with its function.

Guard cell

Length =

Phloem cell

Length = Length =

Type of cell

Function

(a) Root hair cell

A Changes shape to open and close pores in the leaf

Palisade cell

(b) Xylem cell

B Increases surface area for efficient absorption of water and minerals

Xylem cell

(c) Guard cell

C Carries water and minerals up the plant

2 Deduce why the epidermal cells in leaves have a flattened shape. 3 outline how xylem cells form into long tubes.

Size (µm)

Onion epidermal cell Length = Width =

(b) calculate the average size of the cells listed in the table in part (a). (c) construct a column graph of the data in part (a), showing cell type on the horizontal axis and cell size on the vertical axis. 7 Deduce how guard cells got their name. 8 Guard cells and stomata usually occur only on the lower part of the leaf, away from direct sunlight. explain why.

4 Recall which cells make up the tubes that transport food in the leaves down through the stem.

9 Why are all plant cells not the same?

Think AnD ReASon

cReATe

5 explain whether you would expect to find chloroplasts in roots.

134

4

1

Type of specimen

Plant

Why are there some features that all cells possess?

DiScUSSion

below, making it large enough for all of your results. Source of specimen

3

prepared slides, recording your observations in the table as you make them.

Core science | stage 4 Complete course

10 construct a working model of a pair of guard cells, using balloons.

5.8

tissues and organs In animals and plants, cells work in teams. Each team has a particular job to do. If all of the teams do their jobs properly, the animal or plant stays alive and healthy. If one or more of the teams doesn t do its job, the animal or plant becomes sick. It could even die. All animals and plants are multicellular. That means that they have many cells. Plants and animals can have billions of cells. Cells of the same type form teams of cells called tissue. For example, your muscle cells form muscle tissue. Smooth muscle cells form the smooth muscular tissue in your blood vessels and your digestive system. Other types of muscle cells form the cardiac muscle that keeps your heart beating, and your nerve cells form nerve tissue.

Cells

Tissues

Teams working together Organs Your organs are made of different types of tissue. Your brain, heart, liver and stomach are just some of the organs in your body. Each organ has a very important job to do. The tissues in the organ work together so that the job is done properly. For example, your heart is an organ that pumps blood around your body. It is made up of cardiac muscle tissue and connective tissue. The blood that the heart pumps is also a type of connective tissue. Nerve tissue sends messages from your brain to your heart to Digestive system control your heart rate. Organs make up systems. Your heart, blood vessels and blood make up the The different types of cell in the human body are grouped into four main types of tissue. circulatory system. Your lungs, Type of tissue What it does Example windpipe and the sheet of Forms a lining around other body Skin surface (epidermis), Epithelial tissue muscle under your lungs, parts to protect them stomach lining, lung lining (or lining tissue) called the diaphragm, are part Muscle tissue Tightens and loosens itself to Biceps in your arm, cardiac of the respiratory system. move other body parts muscle (heart muscle) Your stomach, intestine, liver, Nerve tissue Carries messages around your Optic nerve (from your eye), pancreas and oesophagus are body spinal cord organs of the digestive system. Connective tissue Holds other tissues together and Bone, cartilage, blood Systems work together to keep provides support and structure organisms alive.

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Some systems in the human body System Digestive system

Main organs Stomach, liver, intestines

Job To break down food into particles small enough to pass through the walls of the intestine and into the bloodstream

Respiratory system

Trachea (windpipe), lungs

To take oxygen from the air and return carbon dioxide to the air

Circulatory system

Heart, blood vessels

To move nutrients and gases around the body

Nervous system

Brain, spinal cord, nerves

To send messages around the body

Plants have organs too! It s not just animals that have organs. Each leaf, flower, stem and root is an organ. Each organ is made up of different types of tissue. Each type of tissue has its own job that helps the organ work properly. Food-making tissue is usually found on the top side of the leaf. It contains most of the chloroplasts.

Lining tissue (a layer of epidermal cells) forms a lining around the leaf to protect it.

The largest organ of the body Your skin is the largest organ in your body. it protects your body from germs and weather, helps control your body temperature and releases some of your waste products. it senses warmth (or lack of it), pressure and pain. it even uses sunlight to make a vitamin. Your skin contains lining tissue, nerve tissue and connective tissue. The skin of an adult human weighs about 5 kg. The thinnest part of your skin is on your eyelids (about 0.5 mm thick). The thickest part of your skin is on the soles of your feet (about 4 mm thick). The elephant and rhinoceros are the most thick-skinned animals the skin on their back can be 2.5 cm thick.

Support tissue gives the leaf its shape. The spongy cells that make up this support tissue are surrounded by air spaces. The air spaces allow gases like carbon dioxide and oxygen to flow into and out of these cells. Transport tissue includes the bundles of xylem and phloem cells, which carry water and minerals from the roots to the rest of the plant, and food from the leaves to the rest of the plant.

Cross-section of a leaf, greatly magnified. Each leaf of a plant is an organ.

activities RemembeR 1 Define the term multicellular . 2 List following in order from smallest to largest: organism, cell, system, organ, tissue. 3 Complete the following sentences about animals and plants. (a) work together to form tissues. (b) Tissues work together to form . (c) work together to form systems.

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4 Describe the main job of your: (a) respiratory system (b) circulatory system. 5 Recall two of the organs that make up your: (a) digestive system (b) nervous system. 6 Recall the job of the digestive system in animals.

Think 7 explain why skin is an organ rather than a tissue.

8 Deduce why the food-making tissue in a leaf is usually found on its top side.

imAgine 9 Imagine that you are a tree. You need to get as much water and as much sunlight as you can but you can t move to another location. Describe the features your organs need to help you survive.

5.9

PReScRibeD FocUS AReA implications of science for society and the environment

stem cells a matter of opinion You might have heard about stem cell research in the news. Various groups in society have strong opinions about whether stem cell research should be done.

What are stem cells? Stem cells are cells that are not specialised. However, under the right conditions, they can develop into various types of specialised cells. There are different types of stem cells including adult stem cells, cord blood stem cells and embryonic stem cells.

Adult stem cells Adult stem cells include a type of cell found in the bone marrow. These cells can develop into many kinds of blood cells (red blood cells and many types of white blood cells). Adult stem cells have been found in other parts of the body also, but each type of adult stem cell that has been discovered can develop into only a few kinds of cells, so their use is limited. The use of adult stem cells is not controversial as they can be obtained from consenting adult donors.

disease). Cord stem cells may, however, turn out to be more versatile than adult stem cells. Teams of scientists around the world are trying to find out if cord stem cells can be made into many other types of cells. Currently cord stem cells can be useful in the treatment of some diseases such as leukaemia (cancer of the blood). Some parents make the decision to freeze their baby s cord blood. The cord blood can be kept frozen in case it is needed by the child or the parents later on. This is a costly procedure. Alternatively, the cord blood can be donated to a cord blood bank, where it may be use to treat anyone who might benefit from it. However, the donated cord blood will not be as close a match as a person s own cord blood. With continued research, cord stem cells may one day be used to treat a range of life-threatening diseases.

Baby

Bone marrow stem cells

Red blood cells

Platelets

Placenta

White blood cells

Umbilical cord Bone marrow stem cells can develop into different types of blood cells.

Adult stem cells can be obtained from umbilical cord blood.

cord blood stem cells

embryonic stem cells

Another source of stem cells is umbilical cords. An umbilical cord is the cord through which an unborn baby gets nutrients and oxygen from its mother. When the baby is born, the cord comes out of the mother s body along with the baby. The blood from the cord contains stem cells. The stem cells found in cord blood can develop into only a few types of cells (mainly blood cells and cells involved in fighting

Embryonic stem cells come from embryos. An embryo is formed when a sperm cell fertilises an egg, which then divides into many cells. If fertilisation occurs in the body of a woman, the embryo can attach itself to the wall of the uterus and develop into a baby. If fertilisation occurs in a dish in a laboratory (in-vitro fertilisation, IVF), the embryo cannot develop into a baby unless it is then implanted into the uterus

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of a woman. However, because an in-vitro embryo has the potential to become a human, it is considered by many people to be human life. In Australia, embryonic stem cells are obtained from in-vitro embryos. Removing the stem cells destroys the embryo, which is why many groups Fertilised Egg Fertilisation Sperm object to the egg divides use of embryonic stem cells for research and medicine. An embryo is the result of a sperm fertilising an egg. If this happens outside a woman s body, it is called in-vitro fertilisation.

Embryo

Embryo implants into the womb and develops into a baby.

Embryos are used as a source of stem cells.

Why use embryonic stem cells? If they are grown under the right conditions, embryonic stem cells can remain unspecialised and keep dividing. If embryonic stem cells are allowed to clump, they can spontaneously develop into groups of specialised cells, such as muscle cells and nerve cells. Scientists can control the type of cells they will develop into by providing the stem cells with exactly the right growing conditions. One day, stem cells may be used to treat diseases caused by the death or damage of particular cells. For example, new nerve cells could be grown to replace the damaged nerve cells in people with a spinal cord injury, which is one of the main causes of paralysis. It may even In-vitro embryo Embryonic stem cell be possible to make entire replacement organs from stem cells. Stem cells may be also used Embryonic stem to treat Alzheimer s cell removed disease, Parkinson s Cultured in disease, diabetes and laboratory arthritis.

Professor Alan Trounson is an Australian scientist who has spent a great part of his working life perfecting the technique for creating embryos outside the human body. he was part of the team that produced the first testtube baby in Australia in 1980. he has also done a lot of work on embryonic stem cells. in 2000, his team showed that it was possible to produce nerve cells from embryonic stem cells. he was recently appointed as the president of a californian institute that specialises in stem cell research. it is the best-funded facility of its kind in the world, so Trounson will have the best facilities at his disposal to move stem cell research forwards.

Clump of embryonic stem cells Specific growing conditions

Embryonic stem cells can develop into many different types of cells.

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Alan Trounson, an Australian scientist who is one of the world s top stem cell research scientists Nerve cells

Core science | stage 4 Complete course

Muscle cells

Gut cells

Whole organs

There are many good reasons for stem cell research, but there are also valid arguments for not using embryonic stem cells. A solution would be an alternative source of stem cells that are just as versatile as embryonic stem cells, and many scientists are currently working towards that. In the meantime, the use of embryonic stem cells for research and medicine remains a controversial issue. Christopher Reeve, the actor who played the role of Superman, became quadriplegic as a result of a spinal injury caused by a horse riding accident. He could not move any part of his body below his neck. Stem cell research may one day lead to a way of re-growing nerve cells to cure spinal injury.

activities RemembeR 1 Describe stem cells. 2 Define the term umbilical cord . 3 explain why some parents choose to have their baby s cord blood frozen. 4 Define the term embryo . 5 Describe the work of an Australian scientist involved in stem cell research.

Think 6 Justify why the use of adult stem cells is not as controversial as the use of embryonic stem cells. 7 compare the likely usefulness of embryonic stem cells and adult stem cells in treating disease.

inveSTigATe 8 Go to Weblinks on eBookPLUS at www.jacplus.com.au and click on the Stem Cell link to investigate the views of the major world religions on stem cell research. 9 Cancer cells are also cells that are not specialised. contrast cancer cells and stem cells. 10 Choose one of the following, Parkinson s disease, type I diabetes, spinal cord injury, stroke, rheumatoid arthritis, and investigate: (a) what causes the condition (b) which cells stop working properly (c) what problems result (d) how stem cells might be useful in treating the problem.

11 Michael J Fox and the late Christopher Reeve are two celebrities who have played an active role in supporting stem cell research in the US. investigate why they became involved in this work and some of the initiatives they have been involved with. 12 Find out more about the work of Alan Trounson and some of the important discoveries he has been involved with.

DiScUSS 13 Discuss whether you would have your baby s cord blood frozen and kept for your own family s use if you have a child later in life. 14 explain the difference between adult stem cells and embryonic stem cells. 15 List some arguments for and against embryonic stem cell research. 16 Form six groups. Each group then nominates a student to act out one of the following roles (your teacher will assign one role per group). The other students in the group help the actor write their script. Each of the actors makes a brief presentation to the government (your class) about whether embryonic stem cell research should be allowed in Australia. At the end of the presentations, all the ministers (your classmates) will vote on whether to allow embryonic stem cell research in Australia. Catholic priest: You are against embryonic stem cell research. In accordance with your church s teachings, you believe that life

starts when a sperm fertilises an egg and, destroying embryos to obtain embryonic stem cells is destroying a human life. Teenager: You are paraplegic as a result of a car accident. You hope that stem cell research will lead to a treatment for spinal cord injury so that, one day, you can walk again. Mother of a child with type I diabetes: You hope that stem cell research will lead to a cure for diabetes so that your daughter can have a healthy life free of diabetes. Scientist: You would like to do embryonic stem cell research so that you can help a lot of people, perhaps finding a cure for a disease such as Parkinson s. Mother who has frozen embryos in storage at an embryo bank: You and your husband could not have children the natural way so you had fertility treatment. Ten of your eggs were fertilised with your husband s sperm. Two of these embryos were implanted in your uterus and you had twins. You do not want any more children, but eight frozen embryos remain. With your permission, these embryos could be used as a source of embryonic stem cells. The health minister: You have your own opinion on embryonic stem cell research, but you also need to listen carefully to the views of the above people. After listening to their views, make a short speech to the government (your class) about stem cell research.

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LooKIng BaCK 1 Deduce which of the following types of microscopes were used to take the photos shown below. • Scanning electron microscope • Light microscope • Transmission electron microscope Explain your answers. (a)

(b)

7 Read the following story. Charlotte has a small pond in her backyard. The weather has been warm and sunny and the pond has turned green. Charlotte suspects that algae may be growing in the water. (a) Describe how Charlotte could use a microscope to find out if there are algae growing in the water. Write your answer as a procedure. (b) When Charlotte looked at a sample of pond water under the microscope, she saw various organisms. A sketch of one of the organisms is shown below.

(c)

2 Calculate the magnification when a ×10 eyepiece is used with a ×10 objective lens in a microscope. 3 Explain why a microscope is needed to see cells and the parts inside them. 4 Draw an animal cell and a plant cell, showing and labelling the parts that can be seen with a normal school microscope. 5 Unscramble the letters using the clues provided. (a) SEUNCLU: Control centre of the cell (b) ERAMMBNE: Surrounds the cell (c) OCVAUEL: Contains cell sap (d) CATOPLMYS: Part of the cell between the cell membrane and the nucleus

(i) Is the organism unicellular or multicellular? Justify your answer. (ii) Which kingdom does the organism belong to? Justify your answer. 8 Complete the flow chart below to show how systems, cells, organs and tissues are related to each other. Work together to form

Work together to form

Work together to form

Cells

9 Investigate how specimens are prepared for examination under an electron microscope.

6 (a) Match the following cell names to the diagrams below. Euglena (a) (b) Paramecium onion epidermal cell nerve cell sperm cell guard cells root hair cell bacterium (f)

(b) Recall which kingdom each of these cells belongs to. (c)

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(d)

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(e)

(g)

(h)

10 Groups of similar cells that carry out the same job are called —————————.

3 A diagram of a cell is shown below.

11 The main jobs in the table below have been placed incorrectly. Redraw the table so that the jobs correctly match the tissue. Tissue

Main job

(a) Lining tissue

A To move

(b) Bone tissue

B To send messages

(c) Muscle tissue

C To support

(d) Nerve tissue

D To protect

TEST YOURSELF 1 A microscope is shown below. 1.

4 Identify which of the following statements is true. (a) Tissues are made of different types of organs. (b) A system is made of organs working together. (c) The skin is made up of one type of tissue. (d) Blood is an example of lining tissue. (1 mark)

11.

10.

2.

3.

4.

Which of the following statements is true of this cell? A It is an animal cell because it has a nucleus. B It is a plant cell because it has a cell membrane. C It is an animal cell because it has a large vacuole. D It is a plant cell because it has chloroplasts. (1 mark)

5. 7.

5 The diagram below shows a plant organ viewed under the microscope. (a) Deduce which plant organ is shown. (2 marks) (b) The cells labelled A contain lots of small green dots. What are these green dots called and why are there so many in these cells? (2 marks) (c) The cells labelled B are transparent. Why do they need to be transparent? (2 marks)

6.

B

8.

9.

A

Which of the following magnifies the image? A Parts 1 and 8 B Parts 1 and 3 C Part 3 only D Part 8 only

(1 mark)

2 What is the function of the cell membrane? A It controls the cell. B It gives the cell its shape and supports the cell. C It regulates what can enter and leave the cell. D It is where respiration occurs. (1 mark)

work sheets

5.5 5.6 5.7 5.8

Cells, tissues and organs Classifying cells Cells puzzles Cells summary

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stUDY CHeCKLIst

ICt

The microscope

eBook plus

■ explain the difference between a light and an electron microscope and the advantages of each

5.1

■ explain the difference between a monocular microscope ■ ■ ■ ■ ■ ■ ■

and a binocular microscope 5.1 recall the parts of a school microscope and state their function 5.1 prepare a specimen for viewing under a school microscope 5.4 explain why stains are used when preparing microscope slides 5.4 use a microscope to obtain a focused image of a specimen 5.4 explain why the invention of the microscope had a significant impact on biology 5.2 describe Van Leeuwenhoek s contribution to the field of microbiology 5.2 interpret a timeline such as the one on pages 120 1 5.2

sUMMaRY

eLessons Inside cells Learn about the building blocks of life called cells and organelles in this animated video lesson, looking closely at the difference between the make-up of animal and plant cells. A worksheet is attached to further your understanding.

Looking at cells ■ recall that a micrometre is 1/1 000 000th of a metre, and convert measurements from micrometres into millimetres and metres 5.2 ■ draw a labelled diagram of an animal and plant cell viewed under a light microscope 5.3, 5.4 ■ describe the function of the following cell parts: nucleus, cell membrane, cell wall, chloroplast, cytoplasm, mitochondrion 5.3 ■ draw labelled diagrams of a specimen viewed under the microscope 5.4, 5.6, 5.7

Searchlight ID: eles-0054

interactivities Microscope parts This interactivity focuses on the microscope. You must select the parts of the microscope that best fit a series of descriptions. Instant feedback is provided.

Unicellular and multicellular organisms ■ explain the difference between unicellular and multicellular organisms, and list examples of each

5.5

■ explain how things move in and out of cells 5.4 ■ explain how unicellular organisms reproduce 5.5 ■ recall examples of different types of cells found in animals, such as humans, and their function

5.6

■ explain how the structure of cells is related to their function, using examples

5.6, 5.7

■ recall examples of cells found in plants and their function

5.7

■ explain the meaning of the terms tissue , organ and system , and give examples of each in both plants and animals 5.8 Searchlight ID: int-0205

implications of science for society and the environment ■ define the terms adult stem cells , cord blood stem cells and embryonic stem cells

5.9

■ discuss whether embryonic stem cell research should be done in Australia

5.9

■ give an example of an Australian scientist involved with stem cell research and list some of his achievements

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5.9

Cell jobs This interactivity tests your ability to match a number of different types of cells with their roles in the body. Instant feedback is provided. Searchlight ID: int-0206

6

Forces in action

Skydivers can reach speeds of 200 kilometres per hour as they fall through the air. Once the parachute is open, the descent rate reduces to around 20 kilometres per hour. What force causes the skydiver to descend? How does a parachute slow the rate of descent?

In this chapter, students will: 6.1 ◗ identify the forces acting around

us ◗ identify changes that occur when forces act 6.2 ◗ observe and understand how

friction works in common situations 6.3 ◗ describe the way magnetic poles

behave ◗ outline how we use magnets and

electromagnets 6.4 ◗ explain how the force of gravity

affects all objects in the universe 6.5 ◗ investigate the forces of buoyancy

and surface tension 6. 6 ◗ learn how an understanding of

forces can help to keep us safe.

Both upward and downward forces are acting on a skydiver falling to Earth.

6 Forces in action Thinking about forces 1. Work in small groups of three to four students and try the following activity. (a) Using a large piece of butcher s paper, draw up a table with terms listed in the left column (see below). (b) Discuss each term and what you all think it might mean. (c) In column two of your table, write the possible meaning that your group proposes for each term. If your group finds a term difficult, you can write don t know , but don t be afraid to have an educated guess. (d) Share your group s responses with the class. Term

Possible meaning

Force Friction Magnet Magnetic field Mass Gravity Weight Lubricant Buoyancy Surface tension Aerodynamic

2. 3. 4. 5. 6. 7. 8. 9. 10 .

Identify the forces acting as you stretch a rubber band. Why are bicycle helmets necessary? Explain how a seatbelt protects you in a car accident. Is there gravity on the moon? If so, is it the same as the gravity on Earth? Is it easier to slide a heavy box over concrete or vinyl? Explain why. Why are modern cars designed to be sleek and streamlined? Give some examples of magnets used in household devices. Are all metals magnetic? Elaborate. Explain how heavy cargo ships can float on water.

6.1

What are forces? A force is a push, a pull or a twist. A force can change the speed, direction or shape of an object. For example, when a racquet strikes a tennis ball, it can cause the ball to change speed and direction. It can temporarily change the shape of the ball too.

InveStIgatIon 6.1 What can a force do? You will need: rubber band plasticine tennis ball coin nylon or wool cloth plastic ruler or rod ◗ Copy the following table into your workbook and write down your

observations. ◗ Take notice of any changes in the motion or shape of each object and what

caused the change in the motion or shape. Observations What to do

Changes in motion or shape

What caused the change

Stretch a rubber band. Squash a lump of plasticine. Push down on the floor with one foot. Drop a tennis ball. Observe what happens: (a) at the moment that you drop it (b) as it falls (c) as it hits the ground (d) as it goes up again. A force can change the speed, direction or shape of an object. In this high-speed image, the force of impact between the racquet and ball changes their shape.

Flick a coin with one finger so that it slides along the surface of a table. Observe what happens after the coin is flicked.

Types of forces

Charge a plastic ruler or rod by rubbing it with a nylon or wool cloth. Hold it close to a thin stream of tap water.

Forces are acting around you all the time and they can cause changes to occur. Sometimes the effects are obvious and sometimes they are not. At this moment, forces are acting inside your body to pump blood around. When you write, you use a force to push the pen or pencil. The many examples of forces that affect our daily lives can be classified as either a contact force or a non-contact force.

Discussion 1

When you squash a lump of plasticine and stretch a rubber band, a change in shape is observed. Explain what is different about the behaviour of these two materials after you have applied a force.

2

Does the tennis ball change its shape at all when it hits the ground? What would happen to a falling lump of plasticine when it hits the ground? Would it bounce? Check your prediction.

3

In which two experiments were you able to change the motion of objects without making contact with them?

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contact forces Often, forces can act between two objects that are in contact with one another. Familiar examples of contact force include the force of your hand pulling your shoelaces, the force of your hand on a bottle top as you unscrew it, and the force of your schoolbag pulling down on your shoulders. Forces can act between two objects that are in contact with each other.

Other examples of contact forces include friction and buoyancy. Friction is a contact force between two surfaces that are sliding, or attempting to slide, over one another. For example, there is friction between the tyres of your bike and the ground when you pedal. Without friction, the tyre would just slip and you would not move forward. You cannot walk on water, but water does provide an upward force on you when you step in. This upward force is called buoyancy and it is the force that enables you, and ships, to float.

motion of an object they can get the object moving, slow it down or stop it altogether. Gravity is a non-contact force. We can see the effects of the force of gravity acting between an apple and the Earth when the apple drops from a tree. The force of gravity acting on us is often called our weight. Gravitational forces also hold the moon in orbit around the Earth, and the planets in our solar system in orbit around the sun. Magnetic forces can act without contact too. These forces act between two or more magnets, or between magnets and some metals, such as iron. Magnets have two ends or poles. When two magnets are brought together, they either attract (pull) each other or repel (push), depending on the positions of the poles of the magnets. Electrostatic forces sometimes cause your hair to stand on end immediately after you pull off a sweater. If you rub the end of your pen or ruler through your hair, you might even be able to pick up some small pieces of paper using this electrostatic force.

Measuring forces The standard unit for force is the newton (N), which is named after Sir Isaac Newton (1643 1727), an English physicist famous for his discoveries about how forces affect motion. He was also the author of many scientific laws about light and astronomy. A spring balance is a device used to measure forces. An internal spring stretches as a force is applied to the spring balance, and we can read the force (in newtons) on the scale provided. Spring balances that contain stronger springs can measure larger forces. More sensitive spring balances have weaker springs and measure smaller forces.

Kilograms Newtons 0 0 0.1

1

0.2

2

0.3

3

0.4

4

0.5

5

0.6

6

0.7

7

0.8

8

0.9

9

1.0

10

Kilograms Newtons 0 0 1 2

10 20

3

30

4

40

5

50

6

60 70

7 8 9 10

80 90 100

non-contact forces Forces can occur even between two objects that are not touching each other. These forces are called noncontact forces. Like all other forces, non-contact forces can affect the

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POTATOES

You may experience an electrostatic force when you pull off a sweater.

Spring balances are used to measure forces.

InveStIgatIon 6.2

◗ Commence creating the scale for

your spring balance by marking the starting position on your window. Mark it as 0 masses.

Build your own spring balance You will need: cardboard sticky tape short coil or spring mass carrier and masses

◗ Suspend the mass carrier on your

spring and then mark the new position as 1 mass.

3

Why was it useful to work in teams in this investigation?

Sticky tape Cardboard Spring

◗ Add a mass to the carrier and mark

it as 2 masses. ◗ Working in small teams, cut a

window out of your piece of cardboard to match the dimensions of your fully stretched spring. ◗ Attach your spring firmly to the top

of the window. ◗ Cut out a small arrow from the

remaining cardboard to act as a marker for your spring and attach it to the bottom of the spring.

◗ Continue till the spring is fully

Force 0 masses 1 mass 2 masses 3 masses 4 masses

Window

stretched or you have run out of masses.

Discussion 1

Explain how a spring balance works.

2

Outline any problems you encountered.

Cardboard pointer

Masses and mass carrier

Representing forces

Balanced and unbalanced forces

Scientists use arrows in diagrams to represent forces. The direction of the arrow shows which way the force is acting. The length of the arrow shows how big the force is. A long arrow represents a larger, stronger force than a short arrow. The arrows that represent forces acting on an object should be drawn from the object s centre of gravity. All objects, including your body, have a centre of gravity. Picture a point in your body where your weight would be concentrated if your body was a single point. That point is called your centre of gravity.

Forces act on us all the time when we are moving and even when we are stopped. More than one force is acting on us all the time. The forces acting on us can be balanced or unbalanced.

Your centre of gravity changes with your position. When standing, your centre of gravity is at about bellybutton height.

Balanced forces The arrows describing the up and down forces acting on the kayaker are the same length. That shows that the forces are the same size. But these forces are acting in opposite directions. The mass of the kayaker (and the kayak) pushes down, but the buoyancy force pushes up. The two forces are balanced and so the kayaker does not move up or down.

unbalanced forces The arrows describing the forward and backward forces on the kayaker are not the same length. The forward force comes from the kayaker using a paddle to push forwards. The backward force is the drag from the water slowing the kayak down. These forces are unbalanced. The forward force is larger than the backward force, so the kayaker and his kayak ak move forwards faster and faster. Eventually they cannot move anyy faster because drag increases when speed increases.

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The effect of balanced and unbalanced forces Unbalanced forces cause things to start moving like a kayak in the water. Unbalanced forces can increase or decrease the speed of the kayak as well. If the forward and backward forces are balanced, there is no increase or decrease in speed; the kayak moves at a steady speed or stays at rest.

These forces are unbalanced. Why?

(b) While your finger is still pushing the coin, there are four forces acting on the coin. What are they? Draw a diagram with arrows showing the direction in which each of the four forces pushes or pulls. (c) How many forces are acting on the coin after your finger stops pushing?

activities REMEMBER 1 Define the term force . 2 identify the three possible results of a force acting on an object. 3 Which of the following forces are non-contact forces? friction, electrostatic force, magnetic force, gravity

9 Air resistance is the force that results as objects move through the air. Is air resistance a contact or a noncontact force? Explain your answer. 10 There are four forces acting on the person in this diagram.

4 outline how the size of a force is represented in a diagram. 5 Imagine a moving object. List three things that an unbalanced force could change about the object and its motion. 6 identify the force that slows down movement through water.

THinK 7 Copy the following table into your workbook. Complete it by thinking of one or two everyday examples of forces that produce the effect in the first column. You can complete your table with diagrams or words. Everyday effects of forces Effect

Examples of forces in everyday life

Starting motion Stopping motion Speeding up motion Slowing down motion Changing the direction of motion

11 Redraw the force arrows in question 10 to show the forces acting when the bike rider is slowing down.

Changing the shape of an object

12 Choose two objects around you. Use arrows to draw the forces you think are acting on the objects. (Hint: You can tell if forces are balanced or unbalanced by looking at the object s motion.)

Having no visible effect 8 When you flick a coin so that it slides across a table, it slows down. (a) identify the force that slows the coin down.

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(a) identify which forces are balanced. (b) identify which forces are unbalanced. (c) Is the rider s speed increasing, decreasing or constant?

Core Science | Stage 4 Complete course

work sheets

6.1 Types of forces 6.2 Measuring forces

6.2

Friction Have you ever tried to walk across ice? It s difficult to start moving because you can t easily push off from the slippery surface. Once you re moving, it s then hard to stop. Walking along a concrete path is much easier. The rough concrete provides far more friction than slippery ice, allowing a better grip.

eBook plus

eles-0032

What affects friction? The size of a friction force changes depending on the objects that are rubbing against each other. Friction is usually greatest between two rough surfaces. It also increases when the objects are pressed together tightly.

Friction Friction is a force that acts against the movement of an object. It occurs between any surfaces that are touching and trying to move past each other. Objects travelling through air or water also experience friction. Friction can occur between solid objects if the surfaces that are in contact are rough. Small bumps on the surface of one object catch on bumps on the surface of the other object and slow down the movement.

using friction At times, friction can be a nuisance. For example: • Try sliding a heavy object across a rough surface. Before an object will move, you need to push or pull it with a force greater than the friction force. • Swimmers have to work hard to overcome the drag of the water. In other sports, like motor racing, cars need to be specially designed to keep drag from the air as small as possible. • When engine parts rub together, they can cause the engine to overheat.

eLesson

Friction as a driving force Watch this video lesson to learn about friction and why you couldn’t drive a car or even walk without it.

A scanning electron microscope image of the surface of polished stainless steel. Even surfaces that seem smooth still have small bumps in them. The bumps on a surface get caught on, or grip, the bumps on another surface that is rubbing against it. That s why friction is often called grip.

At other times, we need friction. For example: • The friction between our feet and the ground means that we can push off and start walking. It also means we can stop without sliding. • On a flat road, the friction between a tyre and the road is needed to start the car moving. Without it, the tyres would spin on the spot and the car wouldn t move. Tyres are designed with tread patterns that optimise friction on the road. • Rubbing your hands together on a cold day helps to keep you warm. Whenever friction occurs, the temperature of the two interacting surfaces increases.

This box is easy to slide across the floor. Only a small force is needed to overcome the friction between the box and the floor.

This box is much harder to push. A big force is needed to overcome the friction between the heavy box and the floor. The friction has increased because the bumps along the surfaces of the box and the floor are pressed together more tightly.

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InveStIgatIon 6.3

◗ Repeat this procedure on several other surfaces of

your choice. Surfaces that you might test are vinyl floor, carpet, doormat, concrete and bitumen.

Measuring friction

Friction on different surfaces

You will need: block of wood with hook attached several identical blocks of wood spring balance

Force of friction (newtons) Trial Surface

◗ Copy the table on the right into your workbook.

1

2

3

Average

◗ Use a spring balance to pull a block of wood across your

desktop. As long as you pull steadily, the reading on the spring balance will be equal to the force of friction on the moving block. ◗ Record your reading in the table.

◗ Summarise your average results in a bar or column graph. ◗ Design and carry out an experiment to find out the effect

of mass on the size of the friction force. Record your results in a table and display them on a line graph.

Discussion 1

List the surfaces in order, from greatest friction force to least.

2

What feature of a surface seems to determine the amount of friction?

3

Why was it a good idea to repeat each measurement three times?

Use a spring balance to pull a block of wood across a surface. ◗ Repeat your measurement two more times on the

desktop and calculate the average force of friction. Record all data in the table.

Friction at work Friction might seem like the last thing you would want if you were in a bike race. Many bikes have a streamlined design to reduce the air resistance acting on the bike and the rider. But, if you were in a downhill mountain-bike race, you might want to reconsider. Traction in this sport is very important.

What is traction? Traction and friction are closely related. Traction describes how an object sticks to another. Tyres with good traction grip the road and turn without sliding or spinning on the spot. Downhill mountain-bike riding requires good traction. The downhill surface is steep, bumpy and has many loose particles that slide over the ground surface easily. Without good traction, downhill mountain bikes could slide out of control, all the way down a mountain. Traction helps to keep the tyres in contact with the surface and gives the rider control. It also means that the bike can slow down or stop if the rider needs to do so.

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4 Do heavier objects experience more friction?

Traction is also important when walking. To walk forwards, your foot needs to push back on the ground. If you have good soles on your shoes and a rough surface to walk across, you can move forwards. When walking across a slippery surface, such as ice, it is possible for your foot to slip backwards because there is less traction.

Downhill mountain bikers stay in control with the help of bike tyres that are designed to provide good traction on dirt tracks.

Your joints contain a lubricant called synovial fluid to help stop bones from scraping against each other.

InveStIgatIon 6.4 investigating the friction of shoes Design an experiment to compare the friction of a variety of shoes and a particular floor surface.

Femur

◗ Collect a variety of shoes to test. Include different brands of school shoes

and runners.

oint capsule

◗ Identify the equipment you will need to measure the friction that exists

between each shoe and a particular floor surface. ◗ Collect information about each shoe to be tested, such as length, mass, sole

material and tread. ◗ Write up the method used in your investigation using a scientific report format. ◗ Record your results in a suitable table.

Synovial fluid

Discussion 1

Write a suitable conclusion to your experiment.

2

Identify the variables that you controlled and the variables that you would have liked to control but could not.

Fibula Tibia

Reducing friction Friction is useful if you want to get moving or if you want to stop. However, friction is a problem for moving parts in machines and other equipment. Wheels, like those on a skateboard, need to move freely around an axle. To achieve this, steel balls, called ball bearings, are inserted into the hub of the wheel. The bearings help the wheel roll around the axle, rather than slide over it. The rolling motion of the ball bearings helps to reduce friction rolling objects experience less friction than sliding objects. Lubricants, such as grease, can be applied to the ball bearings to reduce friction even further. The grease provides a slippery layer between the surfaces so that they move more easily. Without ball bearings and grease, the wheels would be difficult to turn and the components would wear out very quickly.

Wheel

Synovial fluid lubricates joints, like this one in the knee, and so reduces friction.

Friction in fluids Axle

Wheel hub

Axle Ball bearings help to reduce friction between the axle and the wheel hub of a skateboard.

Friction between moving parts causes them to heat up; this is not good for a machine with moving parts, but great if you are cold. Campers in the cold rub their hands together to warm them.

Any substance that is able to take up the shape of its container and can flow is called a fluid. Air and water are both fluids. Objects travelling through air and water experience fluid friction. Fluid friction in air is commonly called air resistance or drag. The term drag can also be applied to fluid friction in water. Like rolling friction and sliding friction, fluid friction acts against the motion of objects. Fluid friction limits the speed of objects travelling through air and water. It increases the amount of fuel needed by cars, planes, motorised boats and submarines. Cars, planes, watercraft and bicycles are streamlined to reduce fluid friction. The faster a vehicle needs to travel, the more important streamlining becomes. Some athletes even shave their bodies to streamline them.

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Friction and the space shuttle One of the most dangerous stages of a space shuttle mission is the re-entry into the Earth s atmosphere. After travelling through space with almost no friction at all, the shuttle fires its engines to slow it down. It enters the atmosphere at a speed of about 26 000 km/h. Because it is travelling so fast, the atmospheric drag is large enough to slow it down to about 2000 km/h within minutes. The temperature on the surface of the wings reaches 1500 C. Over 25 000 special ceramic tiles on the surface of the shuttle prevent it from burning up. They protect the astronauts inside from the incredible heat. As it slows down, the size of the drag force on the shuttle decreases and it gradually cools down. About one hour after leaving its orbit, the shuttle lands at a speed of about 300 km/h.

The dangers of the high friction re-entry of spacecraft into the atmosphere were highlighted on 1 February 2003, when the space shuttle Columbia broke up 16 minutes before it was due to land. All seven crew members were killed. nAsA scientists found the tragedy was probably caused by minor damage to some of the ceramic tiles on the shuttle s surface during launch. This left a very small part of the surface unprotected from the high temperatures caused by friction. The resulting fire quickly reached Columbia’ s fuel tanks, causing a huge explosion.

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InveStIgatIon 6.5

Retort stand

investigating shape and air resistance You will need: hair dryer plasticine string protractor thumb tack sticky tape electronic balance retort stand, bosshead and clamp

Bosshead Clamp String

Protractor Hair dryer

Thumb tack

◗ Set up the equipment as

shown in the diagram. ◗ Make different shapes with the plasticine to compare the air resistance. ◗ Attach each shape in turn to the device using a thumb tack. ◗ Turn on the hair dryer and measure the angle of deflection from the vertical

(90 ) position for each shape. ◗ Record your results in a suitable table.

Discussion 1

Which shape produces the greatest angle of deflection?

2

Which shape would you recommend using for a helmet? Explain.

3

Identify each of the following for this investigation: (a) the independent variable (b) the dependent variable (c) important controlled variables.

Damage to Columbia s ceramic tiles was believed to have caused it to overheat and explode on re-entry.

activities REMEMBER 1 Define the term friction . 2 Explain why friction is important when you walk. 3 identify the name of the friction force that acts on an object moving through the air.

8 For each of the unfriendly friction sketches below, state: (i) how the friction force is being a nuisance (ii) what could be done to reduce the effect of the force of friction (iii) what could be done to reduce the force of friction. (a)

4 Apart from the roughness of the surfaces rubbing together, identify one other thing that increases the size of a friction force. 5 identify three ways in which friction can be reduced. Give an example of each method. 6 What is fluid friction and why is it important to streamline?

12 Explain how lubricants protect moving surfaces from wear and tear. 13 Olympic swimmers wear smooth, tight-fitting suits, streamlining their bodies to reduce friction. Some of them even shave their heads. (a) Do you think that shaving heads or legs could give athletes an advantage? Why? (b) identify other sports in which athletes shave parts of their bodies or wear clothing that reduces fluid friction.

(b)

THinK 7 For each of the friendly friction sketches below, state: (i) how the friction force is being helpful (ii) what would happen if the friction force was absent.

(c)

(a) Swimmers streamline their bodies to reduce friction. Unfriendly friction

cREATE

(b)

(c)

Friendly friction

9 In Investigation 6.3 (page 150), the block needed to be pulled at constant speed. (a) Draw a diagram of the block and the surface it is moving along. Add arrows to represent the forward and backward forces. (b) What size must the arrows be, compared with each other, if the block is speeding up? 10 Motorists are advised that they will waste fuel if their tyres are underinflated. Explain why this is so. 11 The force stopping a mountain bike from sliding out of control down a hill is traction. identify the force that pulls the rider and the bike down the mountain.

14 Imagine a world without friction. Write a story about how your life would be different without friction. What things would be easier to do? What things would become almost impossible? eBook plus

15 Using the Friction as a driving force interactivity in your eBookPLUS, match different car tyres to the right weather conditions. Run simulations to see if you can achieve the perfect amount of friction. int-0054 work sheet

6.3 Friction

6 Forces in action

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6.3

Magnetic forces Make a list of all the things that you come into contact with every day that use magnets. The pictures below will give you some clues. You might like to share your ideas with others and compile a class list.

InveStIgatIon 6.6 What does a magnet attract? You will need: magnet selection of materials to be tested (see the list below) ◗ Place a magnet close to

a range of materials to find out which ones are attracted to it. Record your observations in a table like the one below. Attracted

Not attracted

Magnets that might be found at home

Almost every time you North pole push or pull an object, you have to touch it. Magnets can pull objects without actually touching them; the force between a magnet and an South pole attracted object is an example of a non-contact force. The closer Even when a magnet is cut in the magnet is to the object, the half, each half still has a north greater the size of the pulling pole and a south pole. If you could force. keep cutting a magnet in half over Magnets that retain their and over again, each half would magnetism when removed from always have both a north pole and other magnets are called permanent a south pole. magnets. Temporary magnets are objects that lose their magnetism when removed from another magnet.

◗ Test as many of the following

items as possible: pencil, paper, plastic straw, coins, iron nail, stainless steel spoon, aluminium foil, paperclip, copper wire. ◗ Investigate whether some

materials block the magnetic force.

Discussion 1

Which materials were attracted to the magnet?

2

Are all metals attracted to magnets?

3

Of the materials that were attracted to the magnet, which one was attracted the most? Why do you think this was so?

4

Discuss whether some materials block the magnetic force.

Poles The pulling force of a magnet is strongest at its ends, or poles. All magnets have a north pole and a south pole.

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Magnets always have a north and south pole, even if broken in half.

InveStIgatIon 6.7 Poles apart You will need: 2 bar magnets ◗ Take two bar magnets and identify the north and

south pole of each. Position the magnets near each other as shown below. Record whether the magnets attract or repel each other in each case. (a)

N S

(b)

N N

(c)

S S

(d)

S N

Iron filings sprinkled around a magnet

Attraction or repulsion? ◗ Complete the sentences to form your conclusion:

Like poles Unlike poles

. .

opposites attract When the north poles of two magnets are brought close together, the magnets push away or repel each other. This same repulsion force is felt between two south poles. When the north pole of a magnet comes close to the south pole of another magnet, the opposite happens. They pull on each other, or attract.

The magnetic field can be drawn like a map, as shown in S N this diagram. The lines show the direction of the Magnetic fields can be drawn as maps. magnetic force. The lines are closest together where the magnetic force is greatest and are furthest apart where the magnetic force is weakest. Just as iron filings align with the magnetic field, the needle of a compass lines up with the magnetic field. The north pole of the compass points in the direction of a magnet s magnetic field.

InveStIgatIon 6.8 Mapping the magnetic field

Like poles repel.

You will need: horseshoe magnet overhead transparency 2 bar magnets iron filings sheet of A4 paper small compass

Unlike poles attract.

◗ Place a bar magnet in the centre of a sheet of white

Magnetic fields The metallic objects attracted to a magnet lie within the magnet s magnetic field. The magnetic field is the area around a magnet where its magnetic force acts. Although magnetic fields are invisible, we can visualise what they look like by sprinkling iron filings around a magnet. Each of the tiny iron filings in the photograph above is attracted to the magnet. The filings line up in the direction of the magnetic force around the magnet.

paper. Cover the paper and magnet with an overhead transparency. ◗ Carefully sprinkle iron filings over the transparency,

gently tapping it to spread the filings out. Take care not to let iron filings get under the transparency. ◗ Draw a diagram of the pattern made by the iron

filings. Label the north pole and south pole of your magnet on the diagram. The pattern in your diagram is a map of the magnetic field around the bar magnet. ◗ Use the iron filings to investigate the magnetic fields

around a horseshoe magnet and the pairs of magnets shown on the next page.

6 Forces in action

155

(a)

Geographic North Pole

N (b) (c) (d)

Axis of rotation Magnetic North Pole

S

S

N

S

N

S

N

N

S

N

S

S

N

S

Use the iron filings to investigate the magnetic fields around these magnets.

N

Discussion 1

Where does the magnetic field appear to be strongest? How do you know this?

2

What happens to the strength of the magnetic field as you get further from the magnet?

3

Place a compass at several positions around the magnet. The direction in which the north-pointing needle of the compass points shows the direction of the magnetic field lines. Draw a diagram of the magnetic fields around the magnets in the figures above. Add arrows to your diagram to show the direction of the magnetic field.

4

Do the magnetic field lines run from north pole to south pole or from south pole to north pole around the magnet?

The Earth s magnetic field If you hang a magnet from its middle, it always lines up with the North and South Poles of the Earth. The Earth, like the sun and some planets, has its own magnetic field. It is very much like the magnetic field of a bar magnet. Scientists have proposed a number of different theories to explain what causes the Earth s magnetic field. One popular theory is that, as the Earth spins, the movement of molten iron in the Earth s outer core creates electric currents in the core that generate the magnetic field. Notice that there are two north poles and two south poles marked on the diagram above right. The magnetic North Pole is located nearly 1000 km from the geographic North Pole. Similarly, the magnetic South Pole is found just over 1000 km from the geographic South Pole.

Which way is north? A compass is a simple tool for letting us know where north is. The compass needle moves freely around

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Magnetic South Pole

Geographic South Pole

The Earth s magnetic field

the centre point until it N points north. It is pushed and pulled by magnetic forces so that it lines up with the Earth s magnetic field, just like a hanging magnet. W E In fact, a compass needle is a magnet. The tip of the needle that points or seeks north must be the north pole of the magnet. The north S pole of a compass actually gets its name from the term north-seeking pole because it lines up or seeks the magnetic North Pole of the Earth. For the north pole of a magnet to point to the Earth s North Pole, it must really be acting as the south pole of a magnet remember that opposites attract!

Three special metals Not all objects are attracted to magnets. Magnets affect only materials containing iron, nickel or cobalt. Scientists have developed a model or visual representation to explain what causes these metals to be magnetic. In their model, the metals are thought to be made up of small parts that behave like minimagnets. These small parts are called domains. Each of these domains or mini-magnets has a north pole and a south pole.

InveStIgatIon 6.9 Making your own compass You will need: large iron nail (about 50 mm long) strong magnet paperclips or small nails container of water styrofoam cup

As well as being affected by magnets, iron, nickel and cobalt can also be made into magnets. When the domains inside the metals face the same direction, the metal acts as a magnet. If the domains inside magnetic materials are facing different directions, the pushes and pulls of the mini-magnets are cancelled out. It results in the material not being a magnet.

S N N

N

S

S

N

N

S

S

N

N

S

N

N

S

S

permanent magnet. After each stroke, lift the magnet high above the nail before commencing the next one. You need to make sure that each stroke is in the same direction and made with the same end of the magnet.

N

◗ Take a large iron nail and stroke it with a strong

S

N

N

S N

S

N

S

N

S

N

N

S

S

N S

S S N

N

N

S

S S

◗ After a total of 40 strokes, test your new magnet by

trying to attract paperclips or small nails. ◗ Compare the strength of your magnet with that of

others in your class.

If the domains are lined up facing the same direction, the material has an overall north pole and an overall south pole. The material will behave like a magnet.

◗ Use your magnet to make a compass like the one

shown below. You will need a container of water and a float. The bottom of a styrofoam cup will make a good float.

Make your own compass. ◗ Try dropping your homemade magnet on the floor

several times. Test it to see if it still works.

Discussion 1 Is your magnet a permanent magnet or a temporary

magnet? 2 Which end of your magnet is the north pole? How

do you know?

We have seen that a needle or nail can be magnetised by stroking it with a bar magnet in the same direction many times. The domains in the needle are lined up only temporarily and eventually they go back to their original directions. Such objects are called temporary magnets. Bar and horseshoe magnets are permanent magnets. They do not lose their magnetism easily, except by being dropped or by being heated to very high temperatures. Most permanent magnets are alloys, or mixtures, of the metals iron, nickel or cobalt with other elements. Items made of steel are attracted to magnets because steel is an alloy of iron, carbon and other substances.

switched on magnets A magnet s pulling force can be very useful, but sometimes it gets in the way. An electromagnet is a magnet that can be turned on and off with the flick of a switch. It is made up of a coil of wire wrapped around a piece of iron. The piece of iron turns into a magnet when electricity passes through the coil. The iron stops being magnetic as soon as the electricity is turned off.

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157

Electromagnets are used in many machines and appliances. The photograph at right shows one such use. The electromagnet is attached to a giant crane. The electric current is turned off while the electromagnet is lowered into a position over the load of scrap metal to be lifted. When the current is switched on, the iron or steel in the scrap is attracted to the electromagnet and lifted to a container. The electric current is switched off and the metal falls into the container. However, if the metal was not mostly iron or steel, the electromagnet would be of little or no use. Electromagnets like the one in the photograph are also useful in separating iron and steel from other scrap metal. The scrap metal is first shredded into small pieces.

The electromagnet attached to the crane attracts iron and steel objects when the electric current is switched on.

using magnets Permanent magnets and electromagnets are commonly used in our daily lives. The microphones and speakers in devices like telephones contain both permanent magnets and electromagnets. Doorbells and metal detectors also rely on electromagnets. High-speed trains in Europe and China use electromagnets to elevate the train to reduce friction. The voice we hear through the telephone or the music that comes from our stereo or mp3 player is produced by a speaker. The sound is generated when electricity passes into a coil of wire causing it to become an electromagnet. The electric current in the electromagnet changes direction causing it to be attracted and repelled by a ring-shaped permanent magnet around it. This makes the diaphragm of the speaker vibrate, which produces the sound.

InveStIgatIon 6.10 Making electromagnets You will need: power supply 2 insulated wires, one short, the other 1.5 m long Power supply large nail switch paperclips

Insulated copper wire

Switch (open)

◗ Wind the long wire neatly around the nail 15 times. ◗ Set the power supply to 2 volts and close the switch.

Test the nail to see if it will pick up any paperclips.

2

15

2

20

2

25

2

30

4

15

4

20

4

25

4

30

Number of paperclips picked up

of paperclips picked up for 25 and 30 turns of wire. ◗ Raise the voltage to 4 volts. Repeat the previous steps.

Discussion 1

What effect does increasing the number of turns of wire have?

◗ Wind five more turns of wire onto the nail.

2

What is the effect of raising the voltage?

◗ How many paperclips does the electromagnet pick up

3

Did the iron nail retain its magnetism when the current was switched off? Explain.

◗ Record your results in a table like the one above.

now?

158

Number of turns of wire

◗ Keep winding the wire onto the nail. Record the number

Nail ◗ Set up the circuit shown above.

Voltage of power supply (V)

Core Science | Stage 4 Complete course

7 Explain why hanging magnets line up with the North and South Poles of the Earth. 8 Describe what an electromagnet is and explain how it works. 9 List some everyday devices that use electromagnets.

THinK

Electromagnets

The maglev train seems to float above the train tracks. The train touches the track only while it is building up speed before moving.

10 Make a list of as many items as you can that are, or contain, permanent magnets. 11 The magnetic North Pole of the Earth can be considered as one pole of a bar magnet. Is it acting as the south pole or the north pole of a magnet? Explain your answer. 12 Which way would the coloured end of a compass point if you were in a plane flying directly above the Earth s magnetic North Pole?

activities

13 State the advantage of an electromagnet over a permanent magnet. Use an example to illustrate your answer.

REMEMBER

14 Explain why a maglev train is able to travel so fast.

1 identify which of the following statements is correct. (a) Permanent magnets never lose their magnetism. (b) All metals are strongly attracted to magnets. (c) All permanent magnets have a north pole and a south pole. (d) Iron is the only substance attracted to magnets. 2 outline the difference between a permanent magnet and a temporary magnet. 3 How should two bar magnets be placed on a table so that they repel each other? 4 Define the term magnetic field . 5 How can you tell where the magnetic field is strongest around a magnet?

inVEsTiGATE 15 Design and carry out an experiment to measure the strength of different magnets. Record your measurements in a table and display them using a bar or column graph.

DEsiGn AnD cREATE 16 Design a poster to illustrate the variety of common devices that use permanent magnets and electromagnets.

AnALYsE 18 Arianna made her own electromagnet to find out how the number of windings around a nail affected the number of paperclips that the nail could pick up. She used the circuit shown in Investigation 6.10 with the power supply set to 2 volts. Arianna then repeated her measurements with the power supply set to 4 volts and 6 volts. She recorded her observations in a table. Then she constructed the graph below. 16

6 volts

14 Number of paperclips lifted

The maglev train gets its name from MAGnetic LEVitation. it reaches speeds of up to 500 km/h and doesn t even need a normal engine to run! it uses pushing forces between electromagnets on the track and on the train to keep them apart. Electromagnets also propel the train forwards. Magnets ahead of the train pull the train forwards. Magnets behind the train push it forwards.

6 outline how the direction of a magnetic field is determined.

12

4 volts

10 8

2 volts

6 4 2 0

0

10 20 30 40 50 Number of windings

(a) How many paperclips did Arianna lift with 20 windings and the power supply set to 6 volts? (b) Arianna lifted 12 paperclips when the power supply was set to 4 volts. How many windings were there around the nail? (c) How many paperclips could Arianna expect to lift with 50 windings around the nail and the power supply set to 2 volts? (d) Suggest a way that Arianna would be able to improve the reliability of her results. work sheets

6.4 Magnetic forces 6.5 Electromagnetism

17 construct a device that uses an electromagnet to make a noise when you close a switch or push a button.

6 Forces in action

159

6.4

gravitational forces Gravity is the force that ensures that what goes up must come down. It pulls us towards the Earth, pressing our feet onto the ground, which results in the friction that gives us traction. Gravity also dominates the universe, holding the moon in orbit around the Earth, and the Earth in orbit around the sun. It is a force that acts between any pair of objects, whether they are in contact or not. Gravity is therefore a noncontact force.

Gravity everywhere No matter how large or how small, all objects attract each other. This force of attraction is called gravity. Believe it or not, gravity is a very, very small force. Even though all objects are attracted to each other, the effect is felt only when at least one of the objects is massive as massive as a planet, moon or star. The bigger the mass of an object, the greater the gravitational force it pulls with.

the Earth, moon or Mars, your mass does not change. Mass is usually measured in kilograms (kg), although other units such as tonnes and grams are often used. Weight is a measure of the size of the gravitational force pulling you down. Weight is a force so, like other forces, it is measured in newtons (N). Objects of greater mass have a greater weight. For example, a student with a mass of 60 kg has a weight of almost 600 N, while a student of mass 50 kg has a weight close to 500 N. Wherever you go in the universe, your mass is always the same, but your weight depends on the gravitational force acting on you. This gravitational force depends on: • the mass of the object pulling on you. Your weight on Earth is greater than it would be on the moon because the Earth is so much larger than the moon. • how close you are to the object pulling on you. The weight of an astronaut, for example, decreases with increasing altitude. Weight can be measured with a spring balance like the ones shown on page 146. The weight of the object being measured pulls down on the spring and stretches it, moving the pointer. 200 kg

Moon

If it weren t for gravity, the moon would fly right past us. The gravitational attraction between the Earth and the moon keeps the moon in orbit around the Earth.

The force of gravity between you and your desk is very small because both you and the desk have very small masses. You can t see the effect of gravity in this case. The force that attracts you to the Earth and the Earth to you is much bigger. You can see the effect of this force, especially if you fall! The pull of the Earth s gravity is directed towards the centre of the Earth.

Weight and mass You might be surprised to know that mass and weight are two different things. Mass measures how much of a substance there is. No matter where you go on

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40 0 0

0 km

Communication satellite

40 N

! , 4 ) 4 5 $ %

200 kg

km 400

Space station

1740 N 200 kg

Aircraft Earth

10

Earth

1950 N 200 kg

km

1960 N

Weight decreases with altitude while mass stays constant.

Measuring weight

InveStIgatIon 6.11 Measuring weight You will need: 5.0 N spring balance set of slotted 50 g masses retort stand, bosshead and clamp

Mass (g)

Mass (kg)

50

0.05

100

0.10

150

0.15

Weight (N)

◗ Pull down on the hook of a 5.0 N spring balance until it

reads 1.0 N. There are two forces acting on the hook. As long as the hook is not changing its motion, the upward force of tension is the same as the downward pull of your hand.

Tension

Newtons

0

0

100

1

200

2

300

3

400

4

500

5

1

Why is it better to hang the spring balance from a rod rather than hold it in your hand?

2

Does the spring increase its stretch by the same amount each time a 50 g mass is added?

3

How would your results be different if you conducted this activity on Mars?

4

Use your results to complete a copy of the graph below.

5.0

4.0 Weight (newtons)

Force applied by hand

Grams

Discussion

3.0

2.0

A spring balance. There are two forces acting on the hook. ◗ Pull the hook down until the spring balance reads 2.0 N.

1.0

The downward pull has doubled. ◗ What is the tension in the spring?

0

◗ What has happened to the amount that the spring has

0.1

stretched? A spring is a good force measurer because, if the pulling force on it doubles, the amount of stretch doubles. If the pulling force triples, the amount of stretch triples.

Draw a line through the points that you have plotted and continue your line to where you think it should be if you measured the weight of a mass of 500 g. This process is called extrapolation.

6

Is your line straight? Should it be straight?

7

What does your graph tell you should be the weight of a 500 g mass? Measure it and see how accurate your prediction is.

8

How could you predict the weight of an object if you knew its mass?

◗ Add 50 g masses, one at a time, until you have a total

mass of 400 g. Record the mass in kilograms and weight in newtons as you go.

0.5

5

stand and adjust the pointer so that it reads zero. record its weight in newtons in the table above right. Also calculate and record the mass in kilograms by dividing the mass in grams by 1000.

0.4

Graph of weight measured on a spring balance versus mass

◗ Hang the spring balance from a rod fixed to a retort ◗ Attach a 50 g mass to the hook of the spring balance and

0.2 0.3 Mass (kilograms)

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161

Bungee forces The staff at bungee jumping venues must understand the effect of gravity and how forces work. For each jump, they select appropriate equipment for the size of the jumper. The mass of the person jumping determines which cord will be used. The cords are different thicknesses to suit the weight of the jumper.

isaac newton (1643 1727) was an English mathematician, physicist, astronomer and philosopher. You might know him as the guy who sat under the apple tree and, after being struck on the head by a falling apple, discovered gravity. While this is a commonly believed story, scientists aren t convinced it happened that way. Many scientists and historians believe that newton was looking out of the window when he saw the apple fall. At this point he was struck with a realisation apples (and everything else) always fall down, not up or sideways. He wondered about the force that caused this to happen. He wondered what would happen if the tree were much taller. in fact, he was able to deduce, after much time and many calculations, that the force that caused the apple to fall was the same force (gravity) that kept the moon in orbit around the Earth. From these ideas, newton wrote his Law of universal Gravitation, which describes how gravity acts in all places, not just on Earth.

newton was able to explain many observations, including falling apples, tides and orbiting planets with a single law of gravity.

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While in free fall, gravity is the main force acting on the jumper; however, as the rope starts to stretch, it pulls upwards. The upward force increases as the rope stretches, eventually becoming greater than gravity and slowing the jumper to a stop. But the rope force and gravity are not balanced, so the jumper bounces up, reducing the rope force. Eventually, the jumper stops when the rope force is equal to gravity.

Gravity is the force that pulls a bungee jumper towards the ground. The size of the gravity force depends on the mass of the jumper. The size of the gravity force acting on a person is called the person s weight.

The faster the jumper falls, the more air resistance he or she feels. Air resistance is a force that acts on an object moving against air. The air resistance on a bungee jumper is much smaller than the pull of gravity and the pull of the rope.

Forces involved in skydiving There is something about falling through the air at 190 km/h that really gets the adrenalin pumping! Skydiving is an activity that is enjoyed by thousands of thrill seekers around the world and is an important part of military and rescue services. 1. Skydivers can jump from various heights, but most beginners jump from about 4 kilometres above the ground. When the plane is over the jump site, the skydiver leaps from the plane. Beginners are taught to release their parachute as soon as they are clear of the plane. More experienced divers free-fall for some time before opening their parachute.

2. When skydivers jump from a plane, the Earth s pull of gravity causes them to fall towards the ground. Near the start of the jump, a diver does not fall very quickly. At this point in the jump, the diver does not experience much air resistance. But, as the diver s speed increases during the fall, so does the size of the air resistance pushing against him or her.

3. Skydivers can change the amount of air resistance pushing against them by moving their arms and legs and changing the position of their body. By lying flat, with their arms and legs out, divers increase the air resistance pushing against them. This position slows the diver down. With their legs straight up and their head down, a diver falls faster. This explains how one skydiver can catch up with another.

4. During a jump, a skydiver falls faster and faster. The air resistance pushing against a diver gets bigger and bigger as the speed increases. Eventually, the upward push of the air resistance and the downward pull of gravity balance out. There is no overall force acting on the diver any more. When this happens, the diver falls at a steady speed. The steady speed is called terminal velocity. The terminal velocity of a skydiver without a parachute is very fast. A diver could not land safely at this speed, so a parachute is needed.

6. The skydiver lands safely at the drop zone.

5. When the parachute opens, a huge air-resistance force pushes against it. When the parachute first opens, the air resistance is bigger than the gravity force pulling the skydiver down, so the diver slows down. The skydiver reaches a new, slower terminal velocity soon afer the parachute opens.

6 Forces in action

163

◗ Draw up a table like the one below in which to record

InveStIgatIon 6.12

your results from testing the mass of the skydiver, the area of the canopy and the shape of the canopy.

The landing time of a parachute You will need: plastic from freezer bags large paperclips stopwatch metre ruler

scissors plasticine cotton or nylon thread

Area of canopy (square centimetres)

Time taken to land (seconds) Trial 1

Trial 2

Trial 3

Average

Your task is to investigate the effect of one of the following factors on the landing time of a parachute. (a) Mass of the skydiver (b) Size (area) of the canopy (c) Shape of the canopy

Discussion

Use plastic from freezer bags to make the canopy. Cotton or nylon thread can be used to hold a model skydiver, which could be represented by paperclips and plasticine. Ensure that you do each of the following:

1

Write a report of your investigation using the headings Aim, Materials, Method, Results, Discussion and Conclusion.

2

In your discussion, analyse your results and comment on how your design could be improved.

3

As an extra challenge after the investigation has been completed, see who can make the parachute that takes longest to reach the floor with a standard load of, say, five paperclips from a height of 2 metres.

◗ Keep all things constant except the factor that you are

deliberately changing, so that your tests are fair. This is called controlling variables. ◗ Repeat your measurement of landing time at least three

times and calculate an average.

activities REMEMBER 1 Explain the difference between mass and weight. 2 identify the units of measurement for: (a) mass (b) weight. 3 The force of gravity is not the same on all objects. What does it depend on? 4 In which direction does the Earth s gravitational force act? 5 Explain whether your mass would change if you were to visit the moon. What about your weight? 6 identify what causes the moon to orbit the Earth.

THinK 7 When you drop a nail and a feather from the same height, they reach the ground at different times. Explain, with the aid of a diagram, why this is the case.

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8 A falling table tennis ball reaches its terminal speed quite quickly. A falling golf ball takes a long time to reach its terminal speed. Explain why. 9 Gravity exists between two objects only if at least one of them is massive. Is this statement true or false? Explain your answer. 10 identify the largest force acting on a bungee jumper: (a) when the rope is slack (b) while slowing down. 11 The weight of a 3 kg brick is 30 newtons. Predict the weight of a 6 kg brick.

inVEsTiGATE 12 Would a rubber band be as effective as a spring in a force measurer? Design and conduct an experiment to find out. You will need to construct a table and a graph.

The pull of gravity is a little more than one-third of what it is on Earth. Write a diary entry for your very first working day in the laboratory. Your diary entry should be an account of your day from 6 am when your alarm rings until 10 pm when you go to bed. Emphasise the effects of less gravity and don t forget that you need to keep physically fit. eBook plus

14 Use the Bungee game weblink in your eBookPLUS to simulate a successful bungee jump. Set your mass, rope length and dimensions, and try to achieve the right drop. 15 Use the Coaster game weblink in your eBookPLUS to design your own roller coaster. Set the sizes of your hills and loops, the initial speed and mass of your coaster, and the amount of gravity and friction at work.

iMAGinE 13 Imagine that you are working on the first space laboratory on Mars.

work sheet

6.6 Gravity

6.5

Buoyancy and surface tension Buoyancy

Helium-filled party balloons have a large buoyancy force.

Large ferries and cruise ships can carry hundreds of passengers and the ferry itself can have a mass of several thousand kilograms. How are they able to stay afloat? The weight of the ship is balanced by a buoyancy force. The buoyancy force helps this heavy cruise ship, the Queen Victoria, to stay afloat.

InveStIgatIon 6.13 Are things really lighter in water?

The buoyancy force is the upward push on an object that is at least partially submerged in a fluid like a liquid or a gas. The hull of the ship is hollow, making the ship and passengers lighter than the mass of the water that it displaces (takes the place of). Helium-filled party balloons float in air because the buoyancy force is greater than the gravitational force on the balloons.

Discussion 1

You will need: 500 g mass length of string spring balance bucket 500 gram mass

Use the following diagram to work out the size of the buoyancy force on the 500 g mass. Upward forces upward pull of spring balance (a) buoyancy force of water (a) total upward force (a)

N N N

◗ Tie some string around a 500 g mass.

Suspend the mass in a bucket of water without letting it touch the bottom. ◗ Does the mass feel any lighter?

Downward forces weight of 500 g mass (a) total downward force (a)

◗ Use a spring balance to find

the weight in newtons of a 500 g mass suspended in air (a) and record it. ◗ Without removing the mass from the spring balance,

carefully lower it into the bucket so that it sits just under the surface of the water. Record the force measured by the spring balance (b).

N N

The total upward force must be equal to the total downward force while the 500 g mass is stationary under the surface of the water. 2

Is the 500 g mass really lighter when it is under the surface of the water? Explain.

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165

◗ Fill the plastic bottle almost to the

InveStIgatIon 6.14

top with water.

Make a cartesian diver

◗ Attach a small piece of Blu-Tack to

You will need: clear plastic soft-drink bottle and screw cap Blu-Tack plastic pen cap Screw

the clip of a plastic pen cap. ◗ Place the cap in the bottle so it

floats, and seal the bottle tightly. ◗ Squeeze the sides of the bottle

and observe the motion of the suspended diver . You may need to readjust the size of the piece of Blu-Tack attached to the pen cap.

cap

Air space Blu-Tack weight

Plastic pen cap Water

Clear plastic bottle

◗ Record your observations.

Try your hand You will need: eye-dropper a large coin Compete with others in the class to see how many drops of water you can fit on a coin without it spilling off.

1

Draw and label the forces on the Cartesian diver before and after the bottle is squeezed.

2

Explain how the Cartesian diver works.

◗ Swap roles so your partner takes a

turn. Record your team s average. ◗ Tabulate the average of each team

in the class.

Discussion 1

For this to be a fair competition, what variables must be controlled?

2

Explain why you can fit so many drops on the coin without it overflowing.

3

Select an appropriate type of graph to present the class results.

◗ Work in pairs. One partner

carefully adds water to the surface of a large coin, drop by drop. The other partner counts the drops until the water spills off the coin.

activities REMEMBER 1 Name two forces acting on you when you float on your back in a swimming pool. 2 Name the force that keeps a water strider on the surface of water. 3 Explain the difference between buoyancy and surface tension.

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Have you ever seen an insect make its way along the surface of a pool of water? Water striders are particularly good at this. What prevents insects like water striders from sinking into the water? The water particles have a force of attraction between them called cohesion. This force of attraction on the surface of water is called surface tension.

Discussion

The Cartesian diver

InveStIgatIon 6.15

surface tension

THinK 4 Which fluid produces the greater buoyancy force air or water? How do you know? 5 outline what happens to an object when you plunge it into a fluid and let go: (a) if the buoyancy force is the same as its weight (b) if the buoyancy force is less than its weight.

Water striders use surface tension to walk on water.

Surface tension sometimes gives water the appearance of having a transparent skin. While the surface tension is not very strong, it is strong enough to prevent light objects from falling through the surface of the water.

Surface tension prevents water on this coin from overflowing.

6 Explain, in terms of gravity, buoyancy and surface tension, why humans can t walk on water.

inVEsTiGATE 7 Design and carry out an experiment to compare the buoyancy and surface tension of water, olive oil and vinegar. work sheet

6.7 Buoyancy

6.6

PREscRiBED Focus AREA Applications and uses of science

Staying alive Every year in Australia, about 1800 people die as a result of road accidents. Many of the deaths and injuries can be avoided.

safer cycling Bicycle riders account for well over one-third of the road accident injuries in people aged from 10 to 14 years. The most serious injuries tend to be to the head and face. The wearing of bicycle helmets has greatly decreased the number of head injuries to cyclists.

speeds of up to 20 kilometres per hour. Without a helmet, a sudden impact with the ground can cause serious head injuries. With a helmet, the impact force on the head is smaller as the plastic shell and polystyrene foam are crushed, and so the injuries are less severe. Cycling isn t the only sport where you need a helmet. Other activities in which helmets soften the impact of a fall or collision include motorcycling, horse riding and a wide range of sporting activities.

In cars, padded dashboards, collapsible steering wheels and airbags reduce injuries by allowing the upper body to come to a stop more gradually when a car crashes.

The rubber soles and air pockets of some sports shoes are designed to soften the impact when the wearer lands on the ground. This decreases the amount of jarring to the knees, ankles and the rest of the leg. The pockets in these shoes contain a mixture of gases designed to slow the foot down more gradually as it hits the ground and help push it back up again.

A bicycle helmet is required by law.

A bicycle helmet has a layer of polystyrene foam at least one centimetre thick inside a shell of hard plastic. A cyclist s head falling to the road hits the ground at

InveStIgatIon 6.16 Egghead You will need: hard-boiled egg selection of packing materials, such as bubble wrap, foam rubber and newspaper sticky tape cardboard wire

in these shoes, air chambers in the sole offer cushioning and stability. Air flows back and forth between the chambers during the heel-to-toe walking action.

The plastic shell and polystyrene foam of a helmet soften the impact on the head in an accident.

◗ Design, build and test a container

that will protect a hard-boiled egg in a collision. Your aim is to create an egg container that will prevent the shell from cracking when it is dropped from a height of 2.5 metres onto a hard floor. You are actually creating a model of a bicycle accident. The egg represents the head of a cyclist. Your container represents the helmet.

Discussion 1

Draw a neat, labelled diagram of your egg container.

2

Explain how each feature included protected the shell from cracking.

3

If your egg head was injured , suggest how you could improve the effectiveness of your helmet .

6 Forces in action

167

Bend your knees

InveStIgatIon 6.17

In some sports, like basketball and volleyball, you need to jump high above the ground. But, of course, what goes up, must come down. When you land on the ground, you stop because the surface provides a large upward force on you. If you land on your feet with your legs straight and rigid, you stop very quickly, but the upward force on your legs is large enough to cause damage to your knees and other joints. However, if you bend your knees as you land, you stop more slowly and the upward force on your body is reduced.

crash test dummy You will need: pencil sharpener or eraser toy car rubber band aluminium foil ◗ Place a pencil sharpener

or eraser on the toy car to represent a crash test dummy. Push the toy car towards a wall as fast as you can without your crash test dummy falling off. Observe the motion of the crash test dummy after the car collides with the wall. ◗ Modify this experiment to

Belt up When a car collides head-on It s best to bend your knees when landing with an obstacle or another car, after a high leap. the occupants continue to move forwards after the car stops until they are stopped by a force. Without seatbelts the occupants would fly forwards through the windscreen, or their bodies would be stopped suddenly by the steering wheel, dashboard or other parts of the inside of the car. Most deaths and injuries in car accidents are caused by a collision between the occupants and the inside of the car. With properly fitted seatbelts, car occupants stop as the car stops and so are less likely to be killed or injured. Your body is not the only thing that will keep moving once the car stops as a result of a collision. Any loose objects in the car will continue to move after the car stops. You should therefore never leave any large loose objects in the car. They are much safer in the boot!

activities REMEMBER 1 Explain how bicycle helmets protect the head in an accident.

2 Explain why you should bend your knees when landing after leaping high to shoot in basketball. 3 Describe the likely motion of an unrestrained rear seat passenger in a car which collides with a tree at 60 kilometres per hour.

THinK 4 Bicycle helmets are compulsory in New South Wales. Explain why you think it was necessary to make a law to force people to wear them and describe the benefits to society.

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include seatbelts (by using a rubber band) or a crumple zone (by using aluminium foil) at the front of the car.

Discussion 1

Describe the motion of both the car and the crash test dummy after the collision.

2

Explain what difference the rubber band or foil make to the motion of the crash test dummy during and after the collision.

5 When a stationary car is hit from the rear by another vehicle, it is pushed forwards rapidly. Describe the likely motion of a front seat passenger: (a) with a head rest fitted to the seat (b) without a head rest fitted to the seat. 6 List as many sports as you can in which helmets are worn to protect participants from head injuries.

cREATE 7 Design a poster with the title Don t be an egghead. Wear a helmet.

inVEsTiGATE 8 Find out about Newton s First Law of Motion and how it is relevant to seatbelts in cars.

LOOKING BACK 1 Identify the forces missing in each of the diagrams below.

(c)

(b)

Ground (a) Gravity

Gravity Gravity (d)

(g) (e)

Gravity

2 The arrows in the following diagram represent four of the forces acting on a cyclist riding on a smooth, flat surface.

(f)

B

Gravity

3 Name the force that acts against objects that are sliding past each other.

C

A

4 (a) Copy and complete the concept map below to show the links between the types of forces described in this chapter. Add as many links as you can to the map. Don’t forget that you can sometimes make links between the different ‘arms’ of your concept map. Friction

Buoyancy Contact forces

Forces

D (a) Which two forces are equal in size? (b) Which arrow could represent air resistance? (c) Is the cyclist speeding up, slowing down or travelling at a steady speed? Explain your answer.

Non-contact forces Electrostatic

Gravity

6 Forces in action

169

5

(b) Compare and discuss your map with others in the class. (c) Add any further details you wish to your map following the discussion. (d) Comment on what you enjoyed most during your learning in this chapter.

2 The concept of a field is useful in explaining the A elastic force in a spring. B attraction of opposite magnetic poles. C push force on a shopping trolley. D unbalanced vertical forces on a kayak.

Friction can be useful or it can be a nuisance. List three situations in which: (a) friction is necessary. (b) friction is a nuisance.

3 The Earth s gravitational field would be best represented as

6

Explain why the pull of gravity is less on the moon than on Earth.

7

Redraw this diagram. On your sketch, include arrows to represent the forces acting on the book while it is at rest on the desk.

(1 mark)

A

B

C 8

Identify the units used to measure: (a) mass (b) weight (c) force.

D

TEsT YouRsELF 1 The four forces on the cyclist and bike, labelled P, Q, R and S, are respectively P

(1 mark)

Q

S

R

A force of the ground, forward push, weight and air resistance. B air resistance, force of the ground, forward push and weight. C air resistance, forward push, magnetic attraction and road friction. D force of the ground, road friction, weight and air resistance. (1 mark)

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4 A rock was found to have a weight of 5.4 newtons. When submerged in water, its weight was found to be 4.2 newtons. The buoyancy force on the rock is A 1.2 N B 4.2 N C 5.4 N D 9.6 N (1 mark) 5 Discuss the role of forces in your daily life. In your response, identify the different types of forces that you experience and give examples of each. Outline whether forces play a useful role or whether they hinder your activities. (6 marks)

work sheets

6.8 Forces puzzle 6.9 Forces summary

StUDY CHeCKLISt

ICt

Forces

eBook plus

■ identify changes that take place when forces are acting

6.1 6.5

eLessons

■ use the term field in describing forces acting at a ■ ■ ■ ■

SUMMaRY

distance 6.3 classify forces as contact or non-contact forces 6.1 use a spring balance to measure forces 6.1, 6.4 represent forces acting on an object 6.1 identify balanced and unbalanced forces 6.1

Friction as a driving force In this video lesson, you will learn about friction and discover its importance in everyday life. You will see practical examples of friction and learn why you couldn t drive a car or even walk without it.

Friction ■ describe friction as a contact force that opposes motion

6.2

■ identify everyday situations where friction is useful 6.2 ■ identify everyday situations where friction is a hindrance 6.2 ■ outline strategies to reduce friction

6.2

Magnetism ■ outline the behaviour of magnetic poles when they are brought close to each other

6.1, 6.3

■ identify everyday situations in which magnets and

Searchlight ID: eles-0032

electromagnets are used 6.3 ■ identify the strongest part of a magnetic field 6.3 ■ use a scientific model to explain how a material becomes magnetic 6.3 ■ compare permanent magnets and electromagnets 6.3

interactivities Friction as a driving force This interactivity helps you to apply your knowledge of friction to driving. Match the right tyres to the weather conditions, and see if you can achieve the perfect amount of friction.

Gravity ■ recall that all objects exert a force of gravity on all other ■ ■ ■ ■

objects 6.4 explain the difference between mass and weight identify that gravity decreases with altitude 6.4 outline the forces acting on a falling object 6.4 identify Isaac Newton s contribution to our understanding of gravity 6.4

6.4

Buoyancy and surface tension ■ describe forces that allow some objects to float and stand on water

6.5

Applications and uses of science ■ identify recent scientific developments that have improved safety

Searchlight ID: int-0054

6.6

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7

Planet Earth

The Earth is one of eight planets that revolve around the sun. The solid outer crust of our planet is covered mostly with water and surrounded by a layer of gases that support life. Beneath the crust are layers of rock and molten rock at temperatures of up to 7000 C.

Vital statistics of the Earth include: • Age — about 4.5 billion years • Diameter at equator — 12 800 kilometres • Mass — about 6 million billion billion kilograms.

In this chapter, students will: 7.1 ◗ learn about the size, shape and inner

composition of the Earth 7.2 ◗ appreciate the importance of the

water cycle to life on Earth and examine aspects of the hydrosphere 7.3 ◗ identify the gases that form the

atmosphere and describe features of the atmosphere 7.4 ◗ learn about air pressure and examine

the factors that influence it 7.5 ◗ apply knowledge of air pressure

variation to the formation of cyclones 7.6 ◗ look at the changes to our use of

water and soil that cause salinity.

Earth from space Imagine that you are an alien from another galaxy, approaching the Earth in your spacecraft. As you get closer, you steer your spacecraft around the planet so that the sun is behind you. The view in front of you is breathtaking just like the picture on the left. 1. (a) What three features of the Earth are easy to see from your spacecraft? (b) Write a description of the Earth as you see it from your spacecraft. The description should be detailed enough so that you can report your first impressions when you get back to your own galaxy. 2. What do you already know about the planet you re living on? In a group of two to four, brainstorm what you know about planet Earth and then draw a mind map to summarise the ideas and information you have collected. An example of a planet Earth mind map is shown below. To start your mind map, draw the Earth in the centre of a large sheet of paper. Then use words, pictures and colour to add your own ideas. As the example shows, one idea can lead to many others.

An example of a mind map

7.1

Introducing the Earth Welcome to planet Earth! Our home planet was formed just under 4.5 billion years ago and it is located approximately 150 million km from our sun. While this seems like a very long way away (after all, even light takes 8 minutes to get here), we are in just the right place for life to flourish: close enough to provide enough light and heat but not so close that all of our water evaporates and our surface bakes with heat and radiation. The Earth is about 13 000 km across at the equator, and it has a surface area of about 500 million square kilometres. Of this, 360 million square kilometres is ocean with the rest being made of landmasses. Its surface temperature ranges between 90 C and 60 C, with an average of about 15 C. When studying the physical Earth, Astronauts repairing the Hubble Space Telescope while orbiting the Earth scientists look at three main areas: • geosphere: the rocks and material was the celestial chariot of the sun god Apollo. The that make up the Earth, from the surface to the inner ancient Hindus, on the other hand, theorised that the core Earth disc was supported on the backs of four huge • hydrosphere: the water on the surface of the Earth, elephants that stood on the back of a giant turtle that including its oceans, rivers and rainfall. swam through a cosmic sea. • atmosphere: the thin layer of gases bound to the It may surprise you to learn that the idea that the outer surface of the Earth. Earth was a sphere was put forward as early as 600 BC There is a great deal of interaction between these by Thales of Miletus. A hundred years later, the areas of study, as we will see in this chapter. famous mathematician Pythagoras expanded on this, suggesting that this spherical Earth revolved around the sun, rather than the sun revolving around the Earth, as many thought. Aristotle (350 BC) was also From a spacecraft, our planet appears as a blue and in favour of a spherical Earth but, unlike Pythagoras, white sphere. However, this is not so obvious from the he believed that the planets, the moon, the sun and ground and, from mankind s earliest times, there was the stars were mounted on invisible, crystal spheres speculation about the shape of the Earth. arranged concentrically with the Earth at the centre. Early civilisations favoured the idea that the Earth There were, he believed, eight of these spheres. The was a flat disc. Three thousand years ago, the Greek closest sphere held the moon while the furthest poet Homer thought that this disc floated on an ocean carried all of the stars; in between were spheres while the sun, which moved overhead every day, carrying Mercury, Venus, the sun, Mars, Jupiter and

Earth in the round

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Saturn (remember that, in that time, Uranus, Neptune and Pluto hadn t been discovered). By the time Eratosthenes used the sun s location to help him calculate the radius of Earth in the third century BC, the belief in a spherical Earth was widely held, even if people still disagreed about whether the Earth went around the sun or vice versa. In fact, this argument was not really settled until Copernicus published his great work De Revolutionibus Orbium in 1543 in which he provided a reasoned argument that Pythagoras had been correct over two thousand years before. Of course, unequivocal proof did not come until the twentieth century when, with the advent of space travel, humans for the first time could look down on the Earth from space and see it in all its big, blue and definitely spherical glory! The interesting thing is that careful scientific measurements have revealed that the Earth is not exactly spherical. The Northern Hemisphere is slightly smaller than the Southern Hemisphere, and its circumference around the equator is bigger than the circle drawn around the poles.

Inside the Earth The Earth is composed of a number of different substances, including mainly iron, oxygen, silicon, magnesium, nickel and sulfur. When the Earth was formed, this material was molten. This later separated

into distinct layers, with most of the metallic iron and nickel sinking into the core of the planet and the lighter silicates rising to form the mantle and the crust. As yet, humans have travelled only a short way into the Earth s crust. Some goldmines in South Africa reach a depth of 3.5 km, while the deepest hole ever drilled in the crust is 11.3 km deep. This is not far, considering that the crust is up to 70 km thick in places. Even though we have not penetrated very far into the interior, we can get a pretty good idea of what lies underneath the crust in a number of ways. When volcanoes erupt, magma from under the crust flows onto the surface of the Earth and then cools to form igneous rocks. By examining these rocks and analysing the gases that escape from volcanic vents, we can learn a great deal about the mantle, the layer underneath the crust. Scientists also use seismograph readings collected during earthquakes to make predictions about the innermost parts of the Earth. An earthquake produces different types of seismic waves. Many travel through the body of the Earth itself. As they go through the various layers, they slow down or speed up or even bounce off layer boundaries, depending on what the layer is made of. As the paths and speeds of seismic waves can be determined from seismograms, we can make an educated guess about the make-up of the inside of the Earth. Our present model of the structure of the Earth s interior is shown in the diagram below.

Structure of the Earth Crust The crust is the outermost layer of the Earth and is made mostly of rocky material. All of our landforms and soil lie on the top of the crust. All of the Earth s rocks are actually formed in the crust. The crust is at its thinnest below the oceans (about 8 kilometres thick) and reaches a thickness of 40 kilometres or more below the continents. Mantle The mantle is the region of partially molten rock that lies beneath the crust. It is about 2900 kilometres thick and has a temperature that ranges from 500 C near the crust to over 2000 C at its deepest part. The crust and the top section of the mantle make up a region called the lithosphere. Outer core The outer core is made of molten iron and nickel with a temperature of between 4000 C and 6000 C. This layer is believed to be approximately 2300 kilometres thick.

North Pole Northern Hemisphere

Equator

The Earth s surface Two-thirds of the Earth s surface is covered by water of some kind. Ninety-seven per cent of this water is salt water found in the oceans and seas while the rest of the water is fresh water found in the icecaps, streams, rivers and lakes. Scientists estimate that 75 per cent of the Earth s fresh water is in the form of polar ice and glaciers. The Earth s surface water is called the hydrosphere.

Southern Hemisphere South Pole

Inner core The inner core is made up of iron and nickel but, because of the extreme pressure in this layer, it forms a solid even though it is at a temperature of 7000 C. The inner core has a diameter of 2400 kilometres.

Above the surface The atmosphere is a region of gases that are found above the Earth s surface. These gases (which we refer to as the air) are a mixture of mostly nitrogen and oxygen. It is at its densest closest to the Earth s surface, and gets gradually thinner further away. In fact, 99 per cent of our air is found within 80 kilometres of the surface.

The structure of the Earth

7 Planet Earth

175

into a volcano in Iceland. In fact, the deepest mines go down only 3.5 kilometres into the Earth and the deepest drill hole is 11.3 kilometres deep. The following table shows the temperature measured at different depths in a drill hole.

To get an idea of how thin the Earth s crust is, take a medium-sized apple and cut it half. now imagine that the apple is the Earth the crust by comparison is as thin as the apple skin!

Temperatures at different depths of a drill hole

activities REmEmbER 1 Identify and describe the four major regions below the Earth s surface. 2 Recall which layer of the Earth rocks form in. Give both names for the layer. 3 What term is used to describe the part of the Earth s surface covered by water? 4 Describe the mixture you would find in the layer of the Earth known as the atmosphere. 5 Recall how much of the water on the Earth s surface is salt water.

THInk 6 Members of the Flat Earth Society believe that the Earth is flat and shaped like a dinner plate. They believe that photographs taken from space that show the Earth to be a sphere are part of a giant hoax. What do you think? outline some observations that support your opinion. 7 Even though the inner core of the Earth is hotter than the molten outer core, it is believed to be solid. Explain how this is possible. 8 The Earth is travelling through space at a speed of about 110 000 kilometres per hour. This means that it covers about 30 kilometres every second. Calculate how far the Earth travels in: (a) a week (b) a year.

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Depth (km)

Temperature (°C)

0

15

1

44

2

73

3

102

4

130

5

158

6

187

7

215

8

242

9

270

10

297

CREATE 9 Construct a scale diagram of the Earth using the following instructions. You will need a compass, a pencil and a sheet of A4 paper. ◗ Open up the compass so that the ends are 10 centimetres apart. Use it to draw a circle with a radius of 10 centimetres. ◗ Using the same centre, draw two more circles, one of radius 5.5 centimetres and one of radius 1.9 centimetres. ◗ You have now drawn three of the regions below the Earth s surface. Label the three regions. ◗ On your scale diagram, the crust would need to be represented by a pencil line on the surface. Use a thick pencil line to represent the thickest part of the crust and a thin pencil line to represent the thinnest part. ◗ On your scale diagram, the atmosphere would be about 2 millimetres thick. Use a thick blue line to represent the atmosphere. ◗ Label your diagram and then colour it.

usE DATA 10 The centre of the Earth is about 6370 kilometres from the surface. In 1864, the science fiction author Jules Verne wrote the novel Journey to the centre of the Earth. It tells of an amazing journey through the inside of the Earth that begins with a descent

(a) Plot a graph to show how the temperature increases with depth. Label the horizontal axis Depth (km) and the vertical axis Temperature ( C) . (b) Use your graph to predict the temperature at: (i) 2.5 kilometres (ii) 11 kilometres. (c) Calculate roughly how many degrees the temperature increases for each kilometre below the surface. (d) Use your graph to predict the temperature at the centre of the Earth. (e) Scientists estimate the temperature at the centre of the Earth to be about 7000 C. Explain why use of the data above gives such a high prediction. (Hint: What assumptions did you make in part (d)?) work sheet

7.1 Inside the Earth

7.2

Water world We use the word hydrosphere to describe the water on the Earth s surface. This water may be liquid water in the oceans, rivers and lakes, ice in the polar regions or water vapour in the atmosphere.

Water everywhere Two-thirds of the Earth s surface is covered with water. Not all the water is in a liquid form. A significant amount exists as ice in the Arctic and Antarctic regions; 91 per cent of the world s ice can be found in Antarctica. Water is constantly moving and changing states. It is in the oceans, in the icecaps and also in the air as water vapour. Heat from the sun makes water from the oceans evaporate slowly and form water vapour. The invisible water

InvEStIgatIon 7.1 Water in the air You will need: very cold can of soft drink towel ◗ Dry the outside of the can and

allow it to stand on a bench or table. ◗ Observe what happens to the

outside of the dry can.

vapour rises with the warm air. When the water vapour becomes cold enough, it condenses to form clouds of tiny water droplets. The clouds are visible and are kept up by the air moving around them. If a cloud is close to the ground it is known as fog.

eBook plus

eles-0062

Clouds form.

Water droplets fall as rain. Water evaporates.

Rainwater run-off

Sea or lake The water cycle

the beaker with a watchglass containing ice cubes.

InvEStIgatIon 7.2 forming clouds You will need: 250 mL beaker ice cubes watchglass heatproof mat, Bunsen burner and matches tripod and gauze mat safety glasses

◗ Observe the area under the

watchglass.

DIsCussIon 1

Describe what happened to the bottom of the watchglass when you first boiled the water.

2

Describe what happened in the beaker just below the watchglass containing ice cubes.

3

What changes of state took place?

◗ Half-fill the beaker with water and

heat it until the water is boiling.

DIsCussIon

◗ Stop heating and cover the beaker

carefully with a watchglass. Observe the bottom of the watchglass.

1

What change occurred on the outside of the can?

2

Where did the water come from?

◗ Remove the watchglass and heat

What change of state has occurred?

◗ Stop heating and turn off the gas

3

eLesson

The water cycle Did you ever wonder why it rains or where all the water comes from? This video lesson will show you the amazing cycle of water as it is transferred from the oceans to the sky.

the water again until it boils. supply. Quickly but carefully, cover

Forming clouds in a beaker

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At high altitudes the air is very cold. When thick clouds reach this very cold area, the water droplets in them join together to form larger droplets, which are too heavy to be held up by moving air. The large droplets fall to the ground as rain. Rainwater falls into the sea or runs over the ground into rivers and streams, eventually reaching the sea. This constant movement of water between the various states is called the water cycle.

Currents and gyres Ocean currents are the movements of sea water in the Earth s oceans, and they have a critical effect on the Earth s climate. The larger surface currents in the ocean work with the atmosphere to circulate heat energy between the tropics and the polar regions. The amount of cloud cover and type of cloud affect how much sunlight and rain reaches the Earth s surface.

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The movement of the water is very complicated and is affected by many factors including: • movement of wind across the surface of the ocean • evaporation of water from the upper layers of the water • sinking of colder, denser water near the poles • warming of water near the equator • variation in salinity (saltiness) in different parts of the ocean • shape of the ocean bottom • tides (see pages 212 13) • rotation of the Earth around its axis (see pages 205 6). There are two main types of current: surface currents and deep water currents. Surface currents affect the water to a depth of about 400 metres, about 10 per cent of the ocean s water. The other 90 per cent moves in deep water currents. These are very complex currents that move water in the basins of the oceans.

Cumulus Puffy clouds that look like cottonwool. They form at a low altitude but may get thicker and extend into higher levels. They may produce showers of rain.

Altocumulus Middle-level clouds that are rippled and mostly white. They produce light showers.

Stratocumulus Low-level clouds that are generally white. They form groups or rolls of cloud. They produce drizzle.

Cirrus Wispy, fine clouds found at high altitudes. They consist of ice crystals. They do not produce rain.

Stratus Low-level clouds that are found in layers, often grey in colour. They produce drizzle or fine rain. At very low levels, they form fog.

Cumulonimbus Low-level cumulus-type clouds but grey in colour. They produce thunderstorms with lightning. They may stretch from low levels up to 13 kilometres into the atmosphere.

Nimbostratus Sheets of thicker, darker cloud at low altitudes. They produce heavy rain or snow.

Cirrocumulus High-level clouds with many ripples. They do not produce rain.

Core Science | Stage 4 Complete course

Some of these ocean currents are permanent and enclose huge areas of water. They form circular patterns called gyres between continents. Gyres move anticlockwise in the Southern Hemisphere and clockwise in the Northern Hemisphere. The diagram below shows the major ocean currents and gyres.

The movie The Day After Tomorrow depicts the disastrous consequences of the major ocean currents, such as the Gulf stream, ceasing to flow as a result of global warming. The northern Hemisphere enters an ice age. surprisingly, unlike many movies, this one has been praised by environmental scientists for the accuracy of its predictions, although the effects would take much longer to be felt than just the 10 days suggested in the movie.

The world s major currents and gyres Warm current Cool current

North Pacific gyre

North Atlantic gyre

South Pacific gyre

Indian Ocean gyre

South Atlantic gyre

N

Antarctic circumpolar current Antarctic subpolar current Antarctic subpolar current

activities REmEmbER 1 Recall why sea water evaporates.

0

2000

4000 km

9 Examine the diagram of ocean currents above. Deduce why the water in the gyres changes temperature. 10 Explain why we can see clouds but not water vapour in the air.

2 Explain what clouds are and how they form.

11 Rain is produced from very thick cumulus clouds, but not from thinner cumulus clouds. Account for this.

3 Identify which groups of cloud produce rain.

12 Discuss how humans could alter the water cycle.

4 Distinguish between surface currents and deep water currents. 5 Recall at least four factors that affect the formation of ocean currents.

THInk 6 Explain why some clouds pass over without producing rain. 7 Identify the changes of state that can be seen in the water cycle. 8 Explain why the water vapour in clouds condenses.

InvEsTIGATE 13 Use the library and the internet to investigate the importance of the Aboriginal rain dance. eBook plus

14 Visit the Weather zone weblink in your eBookPLUS to see today s weather and forecasts for the coming week all over Australia. work sheet

7.2 Clouds

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7.3

the air up there something in the air? We use the term atmosphere to describe the layer of gases surrounding the Earth, held there by gravity. This mixture of gases is called air. Most of our air is made up of nitrogen and oxygen, with other gases including carbon dioxide, water vapour, methane and argon. Small quantities of poisonous ozone can also be found, with larger amounts located higher up in the atmosphere.

Exosphere 500

1700 Thermosphere

Ionosphere

Mesosphere Nitrogen 78%

Oxygen 21%

Other gases 1%

Dry air near the Earth s surface consists mostly of nitrogen and oxygen.

Although the Earth is about 4.5 billion years old, our atmosphere has been suitable for sustaining life only in the last 1 billion years. The oxygen that is so important to us was produced mainly as the result of photosynthesis by early plants (ocean algae). While oxygen is very important for life, it is not the most common gas in our air. Nearly 80 per cent of our air is made up of the inert gas nitrogen, most of which was released from molten rock early in Earth s history.

Layers of the atmosphere The air particles in the atmosphere are not evenly spread but form a series of layers, each of which has different characteristics. The boundaries between these layers are not very distinct, with one layer merging into another. The layer closest to the surface of the Earth is called the troposphere, and it contains nearly 75 per cent of the air in the atmosphere. The troposphere is not uniform in height around the Earth; it is about 8 km thick above the poles and about 16 km thick at the equator. This is the layer in which all weather happens. Close to the ground, the air is quite warm, but as you go up through the troposphere the

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erature C

ltitude

Te 90

80

0

50 Stratosphere

Ozone layer

25 15

55 Troposphere

0

15

Layers in the Earth s atmosphere

temperature gets colder as the gas particles move further apart we say that the air gets thinner. In the highest sections of the troposphere, the temperature can get as low as 55 C. Above the troposphere is the stratosphere. The air in the stratosphere is much thinner than that in the troposphere, and it gets warmer as you go up. At the top of the stratosphere (about 50 55 km above the Earth s surface), the temperature is around 0 C. About 25 km above the Earth is the region known as the ozone layer. The stratosphere merges into the next layer, the mesosphere (or middle layer ). In this region, the air again starts to get colder as you go higher. At the top of the mesosphere (about 80 km from the ground), the temperature is down to about 90 C.

Above the mesosphere is the thermosphere, a region of the atmosphere that extends to about 400 km above the Earth. While there are very few particles in this region, they receive large amounts of energy from the sun. This means that the temperature in this layer rises rapidly as you go higher. At the top of the thermosphere, the temperature can be as high as 1700 C! The thermosphere gradually gives way to what is known as the exosphere, the region where the Earth s atmosphere meets space. There are very few particles at the edge of the atmosphere, although there are still particles of air as high up as 1500 km. In the thermosphere and exosphere, the gases are not mixed but separate into layers. There is very little nitrogen above 200 km: between 300 and 1000 km most of the air is made up of oxygen; Aurora australis is visible only in higher altitudes of the Southern Hemisphere.

between 1000 and 2000 km the atmosphere is mostly helium, with hydrogen found beyond this. The ionosphere, which extends from the mesosphere, through the thermosphere to the exosphere, is a region where solar radiation gives electric charge to the particles. When the ionosphere is very highly charged, Earth-based communications such as mobile phones, radio and satellite transmissions can be disrupted. The motion of charged particles in the ionosphere causes the aurorae, which are visible in the night sky near the poles.

Greenhouse effect During daylight hours, heat from the sun enters the atmosphere and warms up the Earth s surface. At night, heat from the surface escapes through the atmosphere. If the Earth had no atmosphere, too much heat would escape and it would be bitterly cold

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at night. The gases in the atmosphere trap some of the heat. This trapping of heat is called the greenhouse effect. Carbon dioxide traps more heat than most of the other gases in the atmosphere. Many people are concerned that the increasing amount of carbon dioxide in the atmosphere will cause the Earth to heat up enough to change the climate and sea levels.

ozone layer

Sun

One of the gases that exists in small amounts is ozone. Most of the ozone in the atmosphere is in the region called the stratosphere. Even though ozone makes up only a small part of the stratosphere, it is often referred to as the ozone layer. Ozone is especially important to life on Earth because it blocks out more than 95 per cent of the sun s ultraviolet (UV) rays. These rays cause sunburn and skin cancer. Any decrease in the amount of ozone in the stratosphere is damaging to all living things because more UV rays reach the surface. For humans, this means a greater risk of sunburn and skin cancer. Some chemicals used by humans drift up into the stratosphere, causing chemical reactions that reduce the amount of ozone. These chemicals include CFCs (chlorofluorocarbons), which were once used in aerosol spray cans and older airconditioners and refrigerators.

Heat Solar radiation Heat

Atmosphere

The highest altitude ever reached by a hot-air balloon is 21 km. This is higher than the altitude that jumbo jets travel at!

The greenhouse effect

Some heat escapes but clouds and greenhouse gases trap the rest.

Atmosphere

activities REmEmbER 1 Define the terms atmosphere and air . 2 Recall the two most abundant gases in the Earth s atmosphere.

182

THInk 5 Identify the atmospheric layers in which the temperature increases as you go higher. 6 Suggest why most of the air in the atmosphere is close to the Earth s surface.

3 Explain why the amount of carbon dioxide in the Earth s atmosphere is increasing.

7 Long-distance passenger planes fly above the troposphere where possible. Explain the benefits of flying at this height.

4 Identify which layer most of the atmosphere s ozone is in.

8 Explain why the oxygen in the Earth s atmosphere is not used up

Core Science | Stage 4 Complete course

Earth

by the breathing of humans and other animals.

InvEsTIGATE 9 The gases that trap heat in the Earth s atmosphere are called greenhouse gases. What gases other than carbon dioxide are greenhouse gases? Investigate the greenhouse effect. work sheets

7.3 The atmosphere 7.4 Ozone layer

7.4

Under pressure The air in our atmosphere presses down towards the Earth as a result of gravity. While we often talk about something being as light as air , the truth is that air is a lot heavier than you may think. In fact, at sea level, air exerts a force equivalent to just over a kilogram on every square centimetre of surface. Doesn t seem like much? Well, this works out to about 18 tons being spread out over the entire surface of your skin, which is quite a lot! Of course, keep in mind that the same pressure is being exerted outwards by bodies, so we don t collapse under the weight of all that air. Air pressure is measured in units called kilopascals (kPa). On average, atmospheric pressure at sea level is 101.325 kPa, but the atmospheric pressure at a particular region or location may be higher or lower than this. Changes in air pressure are the result of variations in how closely packed the air particles are. These variations can be caused by altitude, temperature and wind.

Altitude We saw on page 180 that the density of the air decreases as you get higher in the atmosphere. This means that the air pressure also decreases as you get higher. On top of Mount Everest, which is nearly 9 kilometres high, the atmospheric pressure is only 30 kPa less than a third of what it is on the ground. By the time you rise into the exosphere, there are so few particles and they are spread so far apart that there is virtually no air pressure at all.

Heat from the sun Air pressure is affected by how much heat energy is transferred from the sun to the air. You will recall from chapter 2 that adding heat to a substance causes its particles to spread further apart. This increases its volume, and so its density decreases. The same thing happens to air as it is heated. When air is heated, its density decreases. Less dense air rises, pulling air particles upwards. This leaves fewer air particles close to the ground in that location, so the air pressure decreases. When air cools, it becomes denser, so the air particles fall. This causes more air particles to crowd together close to the ground in that location, so the air pressure increases. Heat from the sun is absorbed by the Earth’s surface. Air close to the surface becomes hotter and less dense.

The Earth’s surface transfers heat to air particles.

Warm air rises.

Region of low air pressure

How a region of low air pressure develops

Note that heat from the sun does not heat air particles directly. The sun heats the area on the surface, which then transfers heat energy to the air particles above it. The amount of heat absorbed by the surface depends on the type of terrain (ocean, forest, grazing land, mountains), the time of day and how close the area is to the equator.

Wind Wind is the flow of air particles as they move from an area of higher air pressure to an area of lower air pressure. The speed of the wind depends on the difference in air pressure; the larger the difference in the air pressure, the faster and stronger the wind. You may have noticed that the wind is often stronger near the coast. This is caused by the differences in air pressure over the water and the land. During the day, the land and the ocean are heated by the sun. However, land tends to heat up and cool down faster than the ocean does. As the air particles over the land get warmer and rise, the air pressure over the land becomes lower than that over the ocean. The movement of the air particles from the ocean to the land causes a sea breeze.

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At night, the land cools down faster than the ocean. As the air particles over the land fall, the air pressure over the land becomes higher than that over the ocean. The warmer air over the ocean rises, causing lower air pressure over the water. As a result, air particles flow from the land to the ocean, creating a land breeze.

Air particles move from the land to the ocean.

Air particles move from the ocean to the land.

Higher pressure

Lower pressure Lower pressure

Higher pressure

Coastal winds

activities

InvEStIgatIon 7.3 making a simple barometer You will need: jar large piece of balloon rubber rubber band ruler bamboo skewer sticky tape

REmEmbER

Balloon rubber

Ruler

1 Define the term air pressure .

Skewer

2 Recall how areas of high pressure and low pressure are formed.

Rubber band

◗ Stretch the balloon rubber

over the jar and secure it with a rubber band.

Jar

◗ Hold the ruler upright in front

Making a simple barometer

of the pointed end of the skewer. Make sure that the bottom of the ruler is level with the bottom of the jar. ◗ Carefully note the position of the skewer point on the ruler. Write down the

height (in cm) of this position. ◗ Over the next few days, observe the position of the skewer against the ruler

and write down the height. (Note: Make sure that you use the same ruler each time.)

DIsCussIon

184

1

How do you think this instrument measures air pressure?

2

If the skewer pointer gets higher, does this correspond to an increase or a decrease in air pressure? Explain.

3

Why was it important to use the same ruler each time?

4

It is also important that the jar remains sealed tightly. Why do you think this is important?

Core Science | Stage 4 Complete course

4 Distinguish between a sea breeze and a land breeze.

THInk

◗ Cut a piece of skewer 10 cm

long, including a pointed end. Tape the blunt end of the skewer to the centre of the balloon rubber.

3 Explain how a sea breeze forms at a coastline.

5 Air pressure tends to be higher over the poles and lower over the equator. Explain why this is the case. 6 The air above a ploughed paddock tends to be warmer than over a grassy plain. (a) Explain why you think this happens. (b) Would you expect air particles to rise or fall over a ploughed paddock? Justify your answer. 7 The cabin pressure inside a passenger plane flying at an altitude of 10 km is always adjusted so that it is lower than normal air pressure on the ground. Account for this adjustment. work sheets

7.5 Atmospheric pressure 7.6 Moving air 7.7 Air pressure systems

7.5

PRESCRIBED FOCUS AREA Current issues, research and development

Wild weather Here comes the rain High and low pressure regions do not stay in the same place. They move over the Earth’s surface, changing the weather. When an area of high air pressure (called a high or a high pressure system) moves across the land, it tends to bring fine weather: dry with very few clouds. Highs tend to move fairly slowly and cover a large area. Areas of low air pressure (lows, depressions or low pressure systems) develop where warmer air is rising from the Earth’s surface. As this warmer air cools, it allows cloud to form; so, a low pressure system usually brings rain and strong winds.

upper air even colder. This, in turn, causes the warm air to rise faster and the winds spiralling into the A cyclone can be as wide as low pressure system speed up. This 500 kilometres, have wind speeds process is called intensification. As over 200 km/h inside it and move up to 30 km/h. the air pressure continues to drop and the winds travel faster, the low pressure system moves over the ocean continuing to intensify. When the average wind speed is higher than 60 km/h, the low is called a cyclone. The central low pressure region of the cyclone is called the eye. There is very little wind in the eye of the cyclone. Cyclones usually form between the tropics where the oceans are consistently warm and the effect of the Earth’s rotation is greatest.

Rising air

Cyclones Cyclones form over water in regions where the air pressure is very low and the air temperature is greater than about 27 °C. The warm, moist air in these regions rises and air particles move in from the sides. Because the Earth rotates on its axis, air does not move in a straight line from the high pressure area to the low pressure area. Instead, the air curves as it moves into the low pressure area. This curvature is strongest near the equator. The air entering a cyclone moves in a clockwise direction in the Southern Hemisphere and in an anticlockwise direction in the Northern Hemisphere. When moist, warm rising air meets colder air, the water vapour condenses into rain, making this

Rising air leaves the cyclone anticlockwise in the Southern Hemisphere.

Winds decreasing in speed Gale-force winds

Winds increasing in speed Eye

Gale-force winds

Direction of air flow

Formation of a cyclone

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InvEStIgatIon 7.4 Cyclone in a bottle You will need: two 2 litre PET bottles with lids water food colouring superglue drill with a 5 mm bit

Bottle joiner

Part A: Making the joiner ◗ Take the lids off the two bottles and glue their flat tops

together with superglue. Make sure that they are lined up exactly. Set the lids aside until the glue is completely dry. CAUTION Be careful that you do not stick your fingers together with superglue.

◗ Place the bottles on the bench. A vortex should form in

the top bottle. (If it doesn t, repeat the previous step.) Measure how long the top bottle takes to empty this time.

◗ Use the drill to make a 5 mm hole through the middle of

the joined lids. Part B ◗ Half-fill one of the bottles with water and add some food

colouring. ◗ Screw the joiner tightly onto the half-filled bottle. ◗ Turn the second (empty) bottle upside down and screw it

tightly into the upper half of the joiner. ◗ Turn the joined bottles over so that the coloured water

flows through the joiner from the top bottle into the bottom bottle. Measure how long it takes the top bottle to empty. ◗ Turn the bottles upside down again. This time, as the

water flows from the top bottle into the bottom one, spin them very quickly in an anticlockwise direction. Make sure that you hold both bottles while you do this.

DIsCussIon 1

What effect does the formation of the vortex have on the time it takes the top bottle to empty?

2

What do you think would happen to the emptying time if you made a faster vortex?

3

Did water fow smoothly from the top bottle into the bottom when they were not spun? Explain.

4

Hypothesise whether the direction in which the bottles are spun would affect the emptying speed.

5

What effect do you think the size of the hole in the joiner has on the vortex created? Design an experiment to test this.

Cyclone classification In Australia, cyclones are classified into cyclone severity categories. The table below describes the winds typical of each category. Average wind speed (km/h)

Strongest gusts (km/h)

Central pressure (kPa)

1

60 90

125

98.5

2

90 120

125 170

97 98.5

Minor house damage; heavy damage to crops and trees; small boats break moorings

3

120 160

170 225

94.5 97

Roof and structural damage; some power failures

4

160 200

225 280

92 94.5

Loss of roof; airborne debris; widespread power failure

5

Over 200

Over 280

Under 92

Widespread destruction

Category

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Effects Little damage to houses; some damage to crops and trees

Cyclone Larry caused widespread damage in 2006.

activities REmEmbER 1 Recall what type of pressure system tends to be associated with cloudy skies and rain. 2 Describe how cyclones form. 3 Recall the conditions needed for a cyclone to develop.

8 Describe what effects you think global warming will have on the severity of cyclones in the future.

InvEsTIGATE 9 Use the library and the internet to investigate the differences between cyclones, hurricanes and typhoons. 10 Investigate how the names of cyclones are assigned.

THInk 4 Explain why you are more likely to experience a cyclone if you live in Cairns than if you live in Sydney. 5 Deduce why cyclones break up when they cross the coastline onto land. Use diagrams to help you. 6 Explain why cyclones are more likely in January and February than in June and July. 7 The Bureau of Meteorology warns people to beware of the eye of the cyclone, and advises them to remain inside their houses when the winds first start to drop. Deduce why this warning is given.

usE DATA Use the table on the previous page to help you answer the following questions. 11 The following measurements were recorded for a tropical cyclone as it crossed the Queensland coast. Average wind speed = 120 km/h Maximum wind speed = 160 km/h Lowest central air pressure = 97 kPa (a) Identify the category of this cyclone. (b) Predict the effect this cyclone would have on a house in its path.

(c) Predict the effect the cyclone would have on sugar cane and banana crops in the path of the cyclone. 12 Read the following description of Cyclone Tracy, which struck Darwin on Christmas Day 1974. During the cyclone, wind gusts of more than 200 km/h were recorded. Fifty people were killed in Darwin itself. Some were killed when they tried to get away from their homes. Cars were picked up and thrown off the roads by the wind. Some people were killed when they were hit by flying debris such as roofing iron. Others were drowned in floods caused by storm surge. During the cyclone, about 90 per cent of the city s buildings were damaged. Five vessels were lifted ashore in the harbour. All power supplies were cut and all communications were lost soon after the cyclone struck. On the basis of this description, deduce the category of Cyclone Tracy. Use information from the paragraph to justify your decision.

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7.6

PREsCRIbED foCus AREA Current issues, research and development

Rising salt One of the most pressing problems facing Australia is that of soil salinity or dryland salinity. The term salinity is another way of talking about the saltiness of something. While saltiness may be a good thing when you are talking about salted peanuts, it is not a good thing at all when you are looking at salt in the soil. Interestingly enough, the salt involved in both cases is the same sort sodium chloride. Soil salinity occurs when salt in the soil layers and rocks deep below the surface is brought up to the surface. The salt that is in the lower soil layers has accumulated over a very long time and has come from two possible major sources. • You may recall from your earlier studies that this continent has at different times over millions of years either been covered by the ocean or has contained a vast inland sea. The sediment that accumulated in these salty waters later became dry land, and the rock layers retained a lot of the salt from when they were under sea water. • Geologists and geographers believe that most of the salt trapped in the lower depths of the rocks is the result of hundreds of thousands of years of saltfall a process in which salt water from the ocean evaporates into the atmosphere and returns to the land s interior as rain. Water that reaches the soil from rainfall either runs off back into the waterways or is taken up by the deep roots of the native vegetation. The small amounts of water that continue to move downwards soak into the lower levels of the soil. This water-saturated soil is called ground water. The top surface of the ground water (called the watertable) normally lies far below the roots of the native trees. However, the balance was shifted when European settlers started to use the farming techniques that they

The devastation of the rising watertable and salinity threatens much of Australia s farmland.

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had used in Europe. They cleared the native plants and trees from vast areas of land to make pasture land and crop fields, and, later, set up irrigation systems to water the crops they had planted. The new crops and pasture grasses have much shallower root systems than the native plants and do not cover anywhere near as much of the soil. So now, when rain falls, much more water enters the ground water, causing the watertable to rise. This rising watertable carries with it a lot of the salt that had been locked in the rocks and soil below. The watertable rises even faster on irrigated land. After many years of this type of farming, the salt has reached the upper soil layers near the surface.

The removal of deep-rooted trees has caused the watertable to rise.

Salinity affects the land in a number of different ways: • Where the soil is rich in salt, few plants can survive. This has meant that many crops and many grasses established for herds have died. The native species that originally inhabited the cleared regions cannot tolerate the salt either, so they can t be replanted. • Where water runs off into waterways, they have taken the salt with it, causing increased salinity of waterways. This means that they cannot be used for drinking, and the populations of animals that depend on these fresh water sources have decreased. The Murray River, one of the major sources of fresh water in this country for humans and animals, has been badly affected by salinity. • The reduced supply of drinkable water has led to a decrease in biodiversity of plants and wildlife in saline regions.

The soil in cleared regions has been further degraded by heavy erosion; the deep roots of native plants and trees not only helped maintain the level of the watertable, but also helped keep the soil on the surface in place. Heavy rainfall washes the topsoil into waterways leaving behind land on which little can grow. At present, the problem of salinity is being treated with increased planting of salt-tolerant plants and trees and a massive decrease in land clearing practices. However, it will be many years before we are able to fix this major problem that we have caused. Salinity of water Description of water

Salinity (g/L)

Distilled water

0

Murray River, Albury (NSW)

0.05

Desirable limit for drinking water

0.5

Murray River, Morgan (SA)

0.8

Upper limit for citrus trees

1.0

Upper limit for drinking water

1.5

Upper limit for dairy cows and ewes

6.0

Ground water, Loddon Plain North (Victoria)

15

Pacific Ocean

35

The salinity of water is a measure of the amount of salt dissolved in it. It can be expressed as the number of grams of salt per litre (g/L) of water.

Australian research to reduce soil salinity

in NSW. They aim to reduce soil salinity by reducing the amount of ground water by 50%. The trial focuses on plants that can thrive over spring, summer and autumn, such as lucerne and chicory. Lucerne plants have roots down to 3 metres below the soil surface. This means that the plants dry the soil to a greater depth so, when it rains, most of the water is used by the plant. This keeps the watertable low and, therefore, helps to reduce soil salinity.

saltbush Scientists in Western Australia are studying the use of saltbush for sheep grazing. Many species of saltbush are found in arid regions in the world. However, none of these are common in grazing regions in Western Australia. Scientists, including research scientist Dr Hayley Norman, have discovered that saltbush could be a valuable plant in managing dryland salinity. Unlike other plants, saltbush has an extremely high tolerance to salt and retains salt in its leaves. As an unexpected bonus, sheep grazed on saltbush have health benefits; their meat has a lower fat content. Dr Hayley Norman, CSIRO research scientist, is showing that saltbush is a nutritional feed source.

activities

Evergraze

REmEmbER

Scientists and farmers working on the Evergraze trial are studying a range of plants for grazing pastures at a number of experimental sites, including Wagga Wagga

1 Define the term watertable .

Dr Ralph Behrendt and farmer David Robertson are key researchers in Evergraze trials.

2 Explain why the watertable has risen throughout much of Australia during the past 200 years. 3 Explain why the rising watertable is a threat to farm crops.

THInk 4 Describe how soil degradation due to salinity could be reduced.

InvEsTIGATE 5 Design and carry out an experiment to investigate the effect of the salinity of water on the growth of one type of plant. 6 Some plants are more tolerant to salty water than others. Design and carry out an experiment to identify some plants that might be more suited to areas affected by salinity.

7 Planet Earth

189

LooKIng BaCK 1 The diagram below shows the layers of the Earth from its centre to the surface. (a) Identify the imaginary line around the Earth shown as a dotted line and labelled A. (b) Recall the names of the layers labelled B, C, D and E. (c) Identify which of the layers labelled B, C, D and E has the highest temperature. B

(b) Recall in which layer of the atmosphere you would find the least air. (c) Ozone gas is important to living things because it blocks out most of the ultraviolet (UV) rays reaching the Earth. Recall in which layer is the ozone layer, which contains most of the ozone in the atmosphere. 3 The sun is always shining on some part of the Earth, heating up the area that it falls on. Explain why the temperature of the Earth remains fairly constant.

North Pole

4 Standing on the Earth s surface, it would be easy to think that the Earth is flat. Describe at least three pieces of evidence that indicate that the Earth is round.

C D

E

A

South Pole

2 (a) Recall in which layer of the atmosphere you would find the most air.

5 A hot-air balloon is floating across grasslands at a constant height of 100 metres, and is heading towards a series of freshly ploughed paddocks. Predict what will happen to the altitude of the balloon when it passes over the paddocks, and justify your answer. (Hint: Ploughed land absorbs more heat than grassy plains.) 6 A mountaineer used a digital barometer to measure the change in air pressure that she experienced as she climbed up a mountain. The values she measured are shown in the table below. Altitude (m)

Exosphere

Thermosphere

Mesosphere

Stratosphere

Troposphere

Air pressure (kPa)

0

101

250

98

500

95

750

92

1000

89

1250

86

1500

83

1750

80

Ionosphere

(a) Construct a line graph showing how air pressure changes with altitude. Put altitude on the horizontal axis. (b) Use the line graph to predict the height at which the mountaineer measured an air pressure of 90 kPa. (c) Mount Kosciuszko is the highest mountain in Australia, with an altitude of 2228 metres. Predict the air pressure that would be experienced at the peak. 7 (a) Describe how clouds are formed. (b) Explain the part clouds play in the water cycle. (c) Describe the kind of weather you could expect if you see cumulonimbus clouds in the sky. 8 Explain how a gyre differs from an ocean current.

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9 The picture below shows a satellite image of a cyclone on the Australian coast. Using your ruler and the fact that the straight-line distance between Sydney and Melbourne

is 716 km, extrapolate the diameter of: (a) the cyclone and (b) the eye.

TEsT YouRsELf 1 The term hydrosphere describes A the air that is found in a layer around the Earth. B the rocks that make up the crust and the upper mantle. C the water that is found in streams and rivers only. D all of the water on the Earth s surface. (1 mark) 2 The layer of the Earth s atmosphere that reaches the lowest temperature is the A troposphere. B thermosphere. C mesosphere. D stratosphere. (1 mark) 3 Which of the following clouds do not form rain? A Cirrus B Cumulus C Stratus D Cumulonimbus

4 In which of these locations would you most likely experience the lowest air pressure? A In the eye of a cyclone B On top of Mount Everest C At sea level D On the edge of a cyclone

(1 mark)

5 Describe your planet as if to an alien from a distant galaxy. You must write between 100 and 200 words and you cannot use diagrams. (6 marks) work sheets

7.8 Planet Earth puzzle 7.9 Planet Earth summary

(1 mark)

7 Planet Earth

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StUDY CHECKLISt

ICt

Earth s structure

eBook plus

■ identify the four layers of the Earth s interior and describe the characteristics of each layer

7.1

■ describe the theories developed in the last few thousand years that predicted the shape of the Earth

7.1

The hydrosphere ■ define the term hydrosphere 7.2 ■ describe the water cycle in terms of the physical

SUMMaRY

eLessons The water cycle This video lesson will show you the amazing continuous cycle of water in the Earth s hydrosphere. Through the processes of evaporation, condensation, run-off and rain, water is moving constantly as it transfers between the oceans and the sky.

processes involved 7.2 ■ recall the major types of cloud formation 7.2 ■ describe how the major types of clouds are formed 7.2 ■ recall the factors that contribute to the formation of ocean currents and explain how currents transfer water and energy through the oceans 7.2

The atmosphere ■ identify the gases that make up most of the air 7.3 ■ describe the difference between Earth s atmosphere and space

7.3

■ describe the importance of atmospheric gases, including ozone and greenhouse gases, to life on Earth

7.3

■ identify and describe the layers of the atmosphere 7.3 ■ explain how air pressure depends on local conditions 7.4 ■ explain how cyclones are formed

7.5

Current issues, research and development ■ describe how salinity affects the ecosystem 7.6 ■ describe current Australian research aimed at reducing soil salinity

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7.6

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Searchlight ID: eles-0062

8

the solar system

Until recently, the solar system was considered to contain nine planets in orbit around the sun. But, in 2006, Pluto was stripped of its status as a planet when astronomers from around the world redefined it as a dwarf planet, leaving just eight major planets in the solar system. Pluto had previously been considered the ninth planet. This chapter will take you on a journey through the solar system and explain important phenomena such as the seasons and the day night cycle.

In this chapter, students will: 8.1 ◗ identify the planets in our solar system ◗ compare the sizes of the planets and

their distances from the sun 8.2 ◗ describe the terrestrial planets and gas

giants 8.3 ◗ explain the importance of the sun in our

solar system 8.4 ◗ explain how the movement of the Earth

causes day and night and the seasons 8.5 ◗ explain why the appearance of the

moon changes 8.6 ◗ explain how ocean tides are produced 8.7 ◗ explain what causes lunar and solar

eclipses 8.8 ◗ describe how our understanding of the

solar system has changed over the years 8.9 ◗ describe other features of the solar

system including meteors, meteorites and comets

A close-up of Saturn s rings. Four NASA spacecraft have been sent to explore Saturn. Pioneer 11 was the first to fly past Saturn in 1979. Voyager 1 flew past a year later, followed by Voyager 2 in 1981. More recently, in 2004, the Cassini spacecraft was sent into orbit around Saturn to explore its rings. Saturn s rings are made up of ice and ice-coated rock particles that reflect sunlight to give a variety of colours from reds to blues.

8 the solar system What do you already know about the solar system? 1. Before you start working on this chapter, draw a diagram on A3 paper of the sun and planets of the solar system. Draw the planets in order of their distance from the sun. Label each planet with its name.

2. Write down your answers to each of the following questions. There is no need to use any books or the internet to help. Your answers should be based on what you already know. (a) Which is the largest planet? (b) Which is the smallest planet? (c) Which two planets are closest to Earth? (d) Which planets have moons? (e) Which planets have rings? (f) Which planet has a surface that is frozen solid? (g) What else is there in the solar system apart from planets and moons? 3. Discuss the following questions with others in your class and write down answers to each after your discussion. (a) What do you think a shooting star is? (b) Can we see any planets from Earth? If so, which ones? (c) Why can you see more stars when you are out in the country than when you are in the city? (d) If our Earth is shaped like a sphere, why don t we fall off? (e) How is the moon different from Earth? 4. A friendly alien has landed near your house. He asks you the two questions below to try to understand our part of the universe. How would you answer him? Draw diagrams that help explain your answers. (a) Why can you Earth people see the moon but not the sun at night? (b) What makes your moon shine?

How do you explain to an alien why the moon shines?

8.1

the planets: then there were eight The solar system consists of eight planets travelling around a central star that we know as the sun. These planets travel around the sun in an almost circular path called an orbit. The orbits are actually in the shape of an ellipse, which is an oval shape. The orbits of some planets are more circular than others. Until 2006, our solar system was considered to contain nine planets. The four inner planets Mercury, Venus, Earth and Mars are classified as terrestrial planets (terrestrial means like Earth ). They are small and solid. The next four Jupiter, Saturn, Uranus and Neptune are classified as gas giants. These huge planets do not have a solid surface. Pluto was considered the ninth and outermost planet. However, in 2003, the discovery of an orbiting object, nicknamed Xena,

which is larger than Pluto but further away from the sun, created debate about what defines a planet. In 2006, astronomers agreed that, to be called a planet, a celestial body must: • be in orbit around a star, while not itself being a star • be large enough in mass for its own gravity to cause it to be nearly spherical in shape • travel in an orbit that does not overlap with other objects, including planets. As a result, Pluto and Xena were disqualified as planets and instead were classified as dwarf planets. In the case of Pluto, the main reason for this was that its orbit overlaps Neptune s. The planets Mercury, Venus, Mars, Jupiter and Saturn can all be seen without using a telescope. All of these planets were discovered in

ancient times. They were noticed among the many stars in the sky because they moved in regular patterns against the background of stars. In fact, the word planet comes from a Greek word meaning wanderer. The most distant planets, however, cannot be seen without telescopes and were discovered more recently. Uranus was discovered by accident with a telescope in 1791. Neptune was discovered in 1846 and the dwarf planet Pluto in 1930. All of the planets spin, or rotate, as they orbit the sun. The Earth rotates once every 24 hours. This period is called one day. Jupiter takes only about 10 hours to rotate. That means that a day on Jupiter is only 10 hours long. The planet Venus takes 243 Earth days to complete one full rotation.

Neptune

Uranus

Saturn

Jupiter The eight planets of the solar system. This diagram is not drawn to scale. The planets are really much further apart.

Mars

Earth

Venus

Mercury

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Activities

InveStIgAtIon 8.1 The scale of the solar system

REMEMbER

You will need: cardboard marking pens trundle wheel basketball 2 golf balls (or table tennis balls) 2 marbles 2 peas 2 silver cachous (the small shiny spheres used to decorate cakes) ◗ Make 9 large cardboard labels for your class: one for

the sun and one for each planet. ◗ Collect a basketball to represent the sun, and each

of the items listed in the table below to represent the planets, and move to a large outdoor area.

1 Construct a mnemonic to remember the eight planets in order from the sun. 2 Identify the: (a) terrestrial planets (b) gas giants. 3 Propose why Uranus, Neptune and the dwarf planet Pluto were discovered much later than the other planets.

ThINk 4 The table below shows how the size and distance from the sun of other planets compare with the dimensions for Earth. How the other planets compare with Earth

◗ One student should be selected to hold the sun

and its label. Eight teams of students should also be selected to carry the planets and their labels to the correct distances from the sun . If you don t have a trundle wheel, assume that each of your paces is 1 metre long. (The model created here is not quite to scale for both planet size and distance from the sun. The distances from the sun to the planets listed in the table below are one-tenth of what is consistent with the size of the items representing the plants.)

Planet

Item representing planet

Distance from the sun (metres)

Mercury

Silver cachou

1.5

Venus

Pea

2.7

Earth

Pea

3.7

Mars

Silver cachou

5.7

Jupiter

Golf ball

20

Saturn

Golf ball

36

Uranus

Marble

72

Neptune

Marble

110

DISCUSSION 1

Describe your model in words. Does it surprise you in any way?

2

Outline why this modelling exercise is useful in understanding the solar system.

Core Science | Stage 4 Complete course

Average distance from the sun (Earth = 1 unit)

Mercury

0.38

0.39

Venus

0.95

0.72

Earth

1.00

1.00

Mars

0.53

1.52

Jupiter

A model of the solar system

196

Planet

Diameter at equator (Earth = 1 unit)

11.2

5.19

Saturn

9.41

9.43

Uranus

3.98

19.1

Neptune

3.81

29.9

Follow the instructions below to construct two scale drawings of the solar system. The first drawing will show how the sizes of the planets compare with each other. The second drawing will show how far the planets are from the sun. (a) On a sheet of A3 paper, draw a circle to represent the size of each of the planets in the order listed above. Use the diameter in Earth units from the table above and a scale of 1 cm = 1 Earth unit. Colour and label each planet. (b) Turn the sheet over and rule a 40 cm line across the centre. At one end of the line, draw a large dot and label it as the sun. Use the distances in Earth units from the table to draw a dot representing each planet on your line. Again, use a scale of 1 cm = 1 Earth unit. Label each planet. work sheet

8.1 The solar system

8.2

terrestrial neighbours and gas giants Terrestrial planets Our knowledge of the terrestrial planets Mars, Mercury and Venus has increased rapidly since 1962. It was in that year that the first visit to another planet by a space probe took place when Mariner 2 flew above the clouds of Venus. Since then, space probes have landed on Venus and Mars, sending back data and pictures of their atmospheres and surfaces. Before the space probe missions, our knowledge of these planets was based on observations with telescopes from Earth.

MERCURY PROFILE • Named after Mercury, Roman messenger of the gods • Average distance from the sun: 58 million kilometres • Diameter at equator: 4900 kilometres • Period of rotation (length of day): 59 Earth days • Period of orbit around sun (length of year): 88 Earth days • Surface gravity: 0.38 times that of Earth • Surface temperature: believed to range from 180 C to 420 C • Satellites: none

Mercury is the closest planet to the sun and quite small compared with Earth. The surface of Mercury is very much like that of the moon. It is very heavily cratered and has mountains, valleys and flat plains just like the seas on the moon. Until 1974, when the space probe Mariner 10 flew close to Mercury, the planet was believed to have no atmosphere. Mariner 10 found traces of the gases helium and hydrogen and even smaller amounts of several other gases. Because the pull of gravity on Mercury is much smaller than that on Earth, gases tend to escape into space. The temperatures on Mercury are extreme, generally ranging from 180 C to 420 C. The very thin atmosphere allows heat to escape quickly, so the part of Mercury not facing the sun gets very cold. There is recent evidence to suggest that temperatures on the side of Mercury facing the sun could get as high as 700 C at times.

vENUS PROFILE • Named after venus, Roman goddess of love and beauty • Average distance from the sun: 108 million kilometres • Diameter at equator: 12 100 kilometres • Period of rotation (length of day): 243 Earth days • Period of orbit around sun (length of year): 225 Earth days • Surface gravity: 0.91 times that of Earth • Surface temperature: average about 450 C • Satellites: none

Venus is the closest planet to the Earth and the second-closest planet to the sun. Venus is about the same size as Earth. It is the brightest object in the night sky apart from the moon. The thick clouds above the planet made the surface of Venus a mystery until space probes were able to take photographs in 1974 and 1975. Even though space probes first flew past Venus in 1962, very little knowledge was gained. The atmosphere of Venus was so heavy and hot that early spacecraft and their instruments were crushed or melted. The atmosphere of Venus is almost entirely carbon dioxide. This means that heat does not escape easily. As a result, the range of temperatures is small and the average temperature is much higher than that of Mercury even though Venus is almost twice as far from the sun. The surface of Venus is mostly flat and rocky with two large areas of mountains. It is not very hospitable because of the high temperature, heavy atmosphere and the presence of sulfuric acid in the atmosphere.

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MARS PROFILE • Named after Mars, Roman god of war • Average distance from the sun: 228 million kilometres • Diameter at equator: 6800 kilometres • Period of rotation (length of day): 24.5 hours • Period of orbit around sun (length of year): 687 Earth days • Surface gravity: 0.38 times that of Earth • Surface temperature: usually ranges from about 120 C to about 30 C • Satellites: two

Mars is about half the diameter of Earth. After Earth, its orbit is next furthest from the sun. Like Mercury, it has a small pull of gravity and a thin atmosphere that consists almost entirely of carbon dioxide. The thin atmosphere and lack of clouds made it possible to observe the surface from Earth using telescopes. In fact, in 1877, one astronomer observed what appeared to be canals on the surface. This observation led to the widely held belief that there was life on Mars. In 1976, space probes Viking 1 and Viking 2 sent clear, close-up pictures from the surface of Mars. The pictures showed a dry, barren surface with no evidence of any form of life but what appear to be dried-up river beds. It is believed that these river beds were formed by water millions of years ago and that there is still a lot of frozen water beneath the surface. The most prominent features of the Martian surface are icecaps at the poles, and large volcanoes. The icecaps are believed to be made of frozen carbon dioxide (dry ice) and frozen water. The largest volcano, Olympus Mons, towers 25 kilometres above the surface, with a diameter of 600 kilometres. It is well over double the height of Mount Everest. There is a lot of dust blown about by light winds, giving the planet a red appearance. Mars has two natural satellites, or moons, Phobos and Deimos. They are both quite small. Phobos has a diameter of about 20 kilometres and orbits Mars once every 7.5 hours. Deimos, with a diameter of only 10 kilometres, travels around the planet once every 30 hours.

Gas giants The four largest planets, Jupiter, Saturn, Uranus and Neptune, lie well beyond the planet Mars. These planets are called the gas giants because they are like huge balls of gas. They do not have a solid surface like the terrestrial planets Mercury, Venus, Earth and Mars. The gas giants gradually change from gases in their deep atmospheres to liquids and solids closer to the centre. They are composed mainly of hydrogen, helium and methane. The space probes Voyager 1 and Voyager 2 flew past the gas giants between 1979 and 1989, discovering many new moons. These space probes also sent back pictures showing that all of the gas giants had ring systems around them. Until 1979, it was believed that Saturn was the only planet with rings. In 1995 the space probe Galileo lowered a smaller probe into the atmosphere of Jupiter to gather new data. Jupiter can be seen from Earth without a telescope and its largest four moons can be seen with a small pair of binoculars. Jupiter is heavier than all of the other planets put together. It has a giant hurricane, called the Great Red Spot, which is over twice the size of the Earth. This hurricane was first observed over 300 years ago! Jupiter rotates so quickly that it bulges at its equator. A thin ring of fine dust was detected around Jupiter by both of the Voyager space probes in 1979.

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JUPITER PROFILE • Named after Jupiter, king of the Roman gods • Average distance from the sun: 778 million kilometres • Diameter at equator: 142 700 kilometres • Period of rotation (length of day): 10 hours • Period of orbit around sun (length of year): about 12 Earth years • Pull of gravity: 2.9 times that of Earth • Temperature: average about 140 C • Satellites: at least 62

Saturn has a system of rings around its equator that is several kilometres thick. The rings are difficult to see when their edge faces the Earth. There are seven rings, which consist of thousands of smaller ringlets. The ringlets appear to be made up of small particles of ice-coated rock revolving around the planet like tiny moons. Like Jupiter, it bulges at its equator because of its rapid rotation. Uranus appears blue from the Earth due to methane gas in its atmosphere. The axis of rotation of Uranus is almost in line with the sun. This means that light from the sun falls on one pole for a very long time. Like Jupiter and Saturn, Uranus bulges at the equator because of its rapid rotation. This rapid rotation also creates very strong winds in its atmosphere. Uranus has a system of about 11 rings that are smaller and fainter than those of Saturn.

SATURN PROFILE • Named after Saturn, Roman god of agriculture • Average distance from the sun: 1425 million kilometres • Diameter at equator: 120 000 km • Period of rotation (length of day): 10.7 hours • Period of orbit around sun (length of year): 29.5 Earth years • Pull of gravity: 1.3 times that of Earth • Temperature: average about 170 C • Satellites: at least 33

URANUS PROFILE • Named after the Roman god Uranus, father of Saturn and grandfather of Jupiter • Average distance from the sun: 2867 million kilometres • Diameter at equator: 50 800 kilometres • Period of rotation (length of day): 16 hours • Period of orbit around sun (length of year): 84 Earth years • Pull of gravity: 0.93 times that of Earth • Temperature: average about 210 C • Satellites: at least 27

Neptune, like Uranus, appears blue from the Earth due to the methane gas in its atmosphere. It has a system of five faint rings that appear to consist of dust particles. It has a large dark spot similar to Jupiter s Great Red Spot. This dark blue spot, which is larger than Earth, is believed to be a giant storm. It was discovered in 1989 by the space probe Voyager 2, which also discovered six of the planet s moons. One of Neptune s moons, Triton, is the coldest known body in the solar system.

NEPTUNE PROFILE • Named after Neptune, Roman god of the sea and navigators • Average distance from the sun: 4486 million kilometres • Diameter at equator: 48 600 kilometres • Period of rotation (length of day): 16 hours • Period of orbit around sun (length of year): 165 Earth years • Pull of gravity: 1.2 times that of Earth • Temperature: average about 220 C • Satellites: at least 13

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Activities REMEMbER 1 Construct a table to demonstrate the similarities and differences between the terrestrial planets. 2 Identify which gas makes up most of the atmosphere on the planet Venus.

ThINk 3 Explain why scientists have thought it possible for life to exist on Mars. 4 The atmospheres of Mercury and Mars are very thin. Explain how a thin atmosphere affects the temperature of the planets. 5 Explain why our knowledge of the gas giants increased so dramatically between 1979 and 1989.

CREATE 6 Draw a column graph to compare the time taken for an orbit by the four gas giants. Identify whether there is a trend in the orbital time for these planets. 7 Create a PowerPoint or Flash presentation or a tourist brochure to entice people to visit the planet Mars. You should include information about: ◗ the trip to and from Mars ◗ accommodation on Mars ◗ weather conditions and atmosphere ◗ the surface, including sights to see ◗ how to get around while on the planet ◗ leisure activities, especially those that would be different from those on Earth ◗ excursions to the two moons.

USE DATA 10 Now that you have studied the planets of the solar system, you know quite a lot about each one. Much of this information has been summarised on pages 197 8 but it would be useful to incorporate it into a database. If you don t already have the program installed, use the Microsoft Access weblink to download a free trial of this popular database software. Follow the instructions below to create a database of the planets in our solar system. Before you begin designing a database, you must plan your fields (columns). Set up the following fields: ◗ order from the sun ◗ planet ◗ type of planet ◗ distance to sun ◗ diameter ◗ period of rotation ◗ period of orbit ◗ surface gravity ◗ surface temperature ◗ satellites. The database called Microsoft Access is used by many companies and scientists. If it is installed, you will probably find it on your computer s desktop by clicking Start then Programs. The icon for Access is shown below. Ask your teacher if you need help locating the program. Databases are described in detail in chapter 20, pages 535 6.

INvESTIGATE 8 Until 2006, Pluto was considered the ninth planet of the solar system. Find out: (a) when it was discovered and by whom (b) how Pluto differs from the eight planets (c) whether it has any moons and, if so, their names (d) how long Pluto s orbit of the sun takes. 9 The decision by astronomers not to consider Pluto a planet in our solar system was momentous and somewhat controversial. Take the role of a journalist and write a newspaper article announcing the decision to strike Pluto off the list of planets. Include an outline of the conflicting views of scientists on this issue.

◗ Click on the icon and Access will open. If it starts

with a box asking whether you want to Open an existing file, click on Blank Access database, then click OK. You will then see a box that prompts you to give your new database file a name. Call the file Planets. mdb and click Create. Save it somewhere that you ll remember.

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◗ Now another dialogue box will give you several

◗ Click on Datasheet View. You will be asked to save the

alternatives for creating the table that the database will rely on for information. Double click Create table in Design View. ◗ Your screen should look like screen B below. ◗ What you see is called a table. It s time to enter the names of the fields. This is just like writing the headings for the columns in a table in your workbook. For convenience we will let the data type be Text even though most of our information will be numbers. It is a good idea to write a brief description of the field. Enter your field information so that it looks like screen C below. ◗ You are in what Access calls Design View. You now need to be in Datasheet View. Click on the arrow next to the View icon under the File menu. It looks like this:

table. Give it a meaningful name like Planet info . You may be asked to nominate a primary key. At this stage just click No. ◗ You are now ready to enter the relevant information about the planets. The complete row of information is called a record. In Datasheet View just type in the information and press the right arrow to go to the next field and press Enter to go to the next record. When you have finished entering data, your datasheet should look like screen D below. ◗ Congratulations! You have successfully created your first database. It is what we call a flat file database. Don t forget to save it and remember where it is because you can use it and add to it later.

Screen B

Screen C

Screen D

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201

Just as an example of the power of a database and the sort of things you can do with it, let s ask the planets database to sort some information for us.

◗ You should have a query that looks like the screen below.

We ll run a query to find out which planets are terrestrial and their distance from the sun. ◗ With your table of planets on the screen, click on the arrow next to the New object: Autoform icon. It looks like this:

Let s get some answers to the query. Click on the RUN icon in the tool bar. It looks like this: You should see a little table of the terrestrial planets that looks like the screen below.

◗ Now click on Query. Then click on OK to open the query

in Design View, which should look like the screen below. Notice that your planet table fields are visible in a small box.

You can save your query if you wish to.

DISCUSS

◗ Click in the blank box next to Field. Click on the arrow to

select Type of planet from the drop-down list of your field names. ◗ Now go down to the blank box next to Criteria and type in Terrestrial . Don t tick the little box next to Show. ◗ Now go back up to the next Field box and select Planet. Tick the box so that it will Show. ◗ Finally, select Distance to sun (km) in the next Field box and tick the box so that it will Show.

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In making the planets database, you may have seen a few patterns or connections between things. Use your database to help you answer the following questions. 11 How does the temperature of a planet vary with its distance from the sun? 12 How does the time it takes a planet to orbit the sun vary with its distance from the sun? 13 How does the gravity of the terrestrial planets vary with their diameter? 14 Is there any connection between the size of a planet and the number of moons that it has? eBook plus

15 Use the Explore Mars weblink in your eBookPLUS to discover an interactive simulation of life on Mars and learn about plans to land the first man on Mars. 16 Use the Weight converter weblink in your eBookPLUS to calculate your weight on other planets.

8.3

A very important star The sun is the centre of the solar system. It is one of billions of stars in the universe. The planets, asteroids, meteoroids and comets all orbit the sun, trapped by its huge gravitational pull. The sun is vital to life on Earth, providing the planet with heat and light. CAUTION Never look directly at the sun! Serious eye damage can be caused.

Profile of the sun The sun makes up 99.8 per cent of the total mass of the solar system. The diagram below shows how it compares in size with the planets (the sun is the largest circle).

Mercury Venus Earth Mars Jupiter

Saturn Uranus Neptune

The sun is very much larger than the planets.

The diameter of the sun is 1.4 million kilometres, 110 times that of Earth. In fact, it would be possible to fit 1.3 million Earths into the space occupied by the sun. About 75 per cent of the sun is hydrogen. The rest is mainly helium. There are small traces of other materials such as carbon and iron. Like all of the planets, the sun rotates around its own axis.

It therefore has two poles and an equator. Because it is not solid, different parts of the sun rotate at different speeds. At its equator, the sun rotates once every 25 days. At the poles, it takes 34 days for a full rotation. The huge pull of gravity within the sun produces great amounts of heat and pressure. There is enough heat and pressure to allow nuclear reactions to take place in the sun s

InveStIgAtIon 8.2 What keeps the planets in the solar system?

core. Hydrogen in the sun s core is changed to helium in a nuclear reaction that releases huge amounts of energy. It is this nuclear reaction that keeps the sun and all other stars shining, hot and bright. The temperature at the surface of the sun is about 6000 C, whereas the temperature at its centre, where the nuclear reactions take place, is believed to be about 15 000 000 C.

There must be a force to keep the ball moving in a circle. What force keeps the planets in orbit around the sun?

You will need: styrofoam ball one metre of thread sticky tape small metal nut or similar weight hollow plastic tube or empty biro case scissors

Styrofoam ball (Earth)

Hollow plastic tube (sun) Thread

◗ Tape a piece of thread to

a styrofoam ball or table tennis ball and pass it through a hollow plastic tube. Tie the other end to a large metal nut or similar weight. The ball represents a planet and the plastic tube represents the sun.

Metal nut

DISCUSSION 1

What force prevents the ball in this activity from flying off into the distance while it is in orbit?

2

The planets are obviously not tied to the sun with a string. What is the name of the force that keeps the planets from escaping from the sun and the solar system?

3

Describe what happened to the ball when the thread was cut.

4

What would happen to the planets if the sun suddenly disappeared from the solar system?

◗ Move to an area in the

playground where you are several metres away from all other students. Hold the plastic tube in your hand and whirl the ball in a circle as shown in the diagram above. ◗ Cut the thread just below the

plastic tube while the ball is being whirled and observe the motion of the ball.

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The sun provides the planets with heat, light and other forms of energy. The energy released from the sun is called solar energy. Solar energy reaches all of the planets. Life exists on Earth because the atmosphere allows the right amounts of each type of solar energy to reach the surface. Solar energy provides: • the light needed by plants so that they can grow and make their own food. Animals rely on plants as a source of food. Even animals that do not eat plants eat other animals that do eat plants. As well, animals need light to be able to see. • heat, which keeps the atmosphere, the Earth s surface and bodies of water warm enough to support life. The sun controls our climate. Heat is released from the sun in the form of infra-red radiation. Infra-red radiation is not visible to the human eye. Some gases in the Earth s atmosphere trap infra-red radiation from the sun. This makes the atmosphere heat up. This process is called the greenhouse effect. The atmosphere of Venus is mostly carbon dioxide, which absorbs a lot of infrared radiation. The greenhouse effect is responsible for the extremely high temperatures on Venus. • ultraviolet radiation, which is needed by humans to help the body make vitamin D. The amount required can be obtained by being outdoors in the open for just a few minutes. However, the ultraviolet radiation emitted from the sun is also the cause of sunburn and can lead to skin cancer. UV radiation is not related to temperature, so you can still get sunburned on cool, cloudy days. The Bureau of Meteorology provides a daily forecast of the sun s UV radiation intensity. This is called the UV index. It divides UV radiation levels into low (1 2), moderate (3 5), high (6 7), very high (8 10) and extreme (11 and above). In Australia, UV radiation levels are most intense from the beginning of September to the end of April, particularly between 11 am and 3 pm. When UV levels are 3 and above, sun protection is needed because the UV radiation is intense enough to damage the skin. The ozone layer high in the Earth s atmosphere absorbs much of the ultraviolet radiation reaching the Earth from the sun. If humans were living and working in sunlight on the moon or Mars, they would need a lot more protection from ultraviolet radiation than on Earth. Like infra-red radiation, ultraviolet radiation is not visible to the human eye. • other forms of radiation including radio waves, X-rays, microwaves and gamma rays.

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Together, all of the different forms of energy coming from the sun are referred to as the electromagnetic spectrum. 20 UV Alert: 8.20 am to 5.10 pm MA UV Index: 15

15 UV Index

Energy from the sun

Extreme 11 Very high 8

High

6

Mod 3 Low

20

6 am

8 am 10 am 12 pm 2 pm 4 pm 6 pm 8 pm Sydney Fri 5 Dec. 2008

The daily forecast of the sun s UV intensity allows us to predict the time of day when the sun s rays will be most damaging to our skin.

Activities REMEMbER 1 Describe what the sun is. 2 Identify the force that keeps the planets in orbit around the sun. 3 Outline what happens inside the sun to provide the huge amount of energy that it releases.

ThINk 4 Explain why life on Earth would not be possible without the sun. 5 Explain why there is no greenhouse effect on Mars. 6 Explain why you would need protection from the sunlight on Mars, even though it is very cold. 7 All of the Earth s fossil fuels, including coal, petroleum and natural gas could be described as stored solar energy. Explain why. (Hint: Think about how they are formed.)

INvESTIGATE 8 Find out more about one of the following sun topics and present your findings. ◗ Sunspots and how they can affect the Earth ◗ What causes the northern lights (aurora borealis) and southern lights (aurora australis) ◗ How the Earth is protected from the particles and radiation from the sun ◗ Space probes sent to study the sun work sheet

8.2 The sun

8.4

the earth in motion Day and night Have you ever wondered why it gets dark or why the sun rises in Sydney before it does in Perth? Why is Australia in the middle of a hot summer in January while Europe experiences a cold winter? These things can all be explained by the movement of the Earth through space.

The Earth s rotation To us on Earth it seems that the sun rises each day in the east and sets in the west. In fact, the sun doesn t move across the sky at all. It is the Earth that moves and quite fast, too! People living on the equator are moving at close to 1670 kilometres per hour! We don t sense we are moving as everything around us moves at the same speed. Like a spinning top, the Earth rotates spinning from west to east around its axis. The axis of the Earth is an imaginary line drawn from the North Pole to the South Pole, but tilted at an angle of 23.5 . One rotation takes 24 hours. We call the time for a complete rotation one day. As the Earth spins around, first one side and then the other faces the sun and experiences daytime. The side facing away from the sun gets no sunlight, so it experiences night-time.

6 am

The Earth is spherical but it is not a perfect sphere. The diameter of the Earth measured across the equator is 12 760 km. however, if you measure the diameter between the two poles, the diameter is shorter by 40 km because the Earth has a slight bulge at the equator. The Earth rotates from west to east. Continents facing the sun are in daylight.

6.15 am

23.5

North Pole

Sun s rays

Night

Equa tor Sun s rays Day

South Pole Axis

23.5

6.30 am

On the east coast of Australia, the sun rises over the Pacific Ocean.

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The Earth rotates from west to east. Therefore, the sun during the day and the moon, planets and stars during the night seem to move in the other direction, from east to west. Ancient astronomers believed that the Earth was stationary while objects in the sky moved.

Star trails. Stars appear to move in the night sky but it is the Earth that is rotating. ◗ Draw an outline of Australia and Africa on your sphere.

InveStIgAtIon 8.3

Use an atlas to check the positions and approximate shape of each continent. Also note the position of north.

Day and night across the Earth You will need: polystyrene (or similar) sphere (about the size of a small rockmelon) metal or wooden skewer pen spotlight or bright torch ◗ Your sphere represents the Earth. Draw a line around the

centre to represent the equator. Label the Northern and Southern Hemispheres and mark in the North and South Poles.

◗ Mark the four compass directions

and west

north, south, east around the outlines of each continent.

◗ Gently push a skewer through the centre of your sphere

from bottom to top through the polar regions . This skewer represents the Earth s imaginary axis. ◗ Do this experiment in a darkened room. This will help you

see more clearly the contrast between light and dark. ◗ Turn on the spotlight in a dark room. Its light represents

the sun s light. Hold the skewer so it leans a little away from the vertical. This represents the Earth s tilt. ◗ Turn your sphere very slowly in the light, making sure

Skewer

you keep the skewer slightly tilted all the time. Turn it in an anticlockwise direction (as seen from above). Watch what happens from side on.

Darkened room

Sphere

DISCUSSION N

1

In which direction is the Earth rotating from east to west or west to east? Check the compass directions you marked on your sphere.

2

In which direction does the sun s light seem to move around the Earth ? How does this explain the apparent movement of the sun across the sky?

3

Where is Africa when Australia is lit up? Where is Australia when Africa is lit up? Explain why these continents experience daylight at different times.

4

How does this experiment help to explain why night falls in Perth about two hours later than in Sydney?

Equator

W E S

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Spotlight or bright torch

The Earth in orbit As well as rotating on its axis, the Earth is travelling through space in orbit around the sun. A gravitational force keeps the Earth in orbit around the sun. The time it takes to complete one revolution of the sun is called a calendar year. The Earth rotates 365 times in each calendar year and so there are 365 days in a year. To make the calendar simpler, each year is allocated 365 days, and every fourth year is called a leap year, with an extra day added (29 February), giving a leap year 366 days in total.

A day on Jupiter is less than 10 hours. This means it takes under 10 hours to complete one rotation. but this giant planet, made mostly of gas, is about 13 000 times bigger than Earth. So when it rotates, its outermost clouds move at close to 45 000 kilometres every hour!

The seasons As the Earth completes its orbit The sun s rays are spread around the sun, the tilt of its axis over a larger area. does not change. It leans to the (Northern Hemisphere left or to the right, depending on is tilted away from the sun.) the direction you are observing Simulating winter the orbit. This means, during one in the Northern Hemisphere part of the orbit, one hemisphere Position of sun and summer in is tilted towards the sun while the the Southern other hemisphere points away. Hemisphere using The hemisphere that is tilted torches The sun s rays are towards the sun is hit more directly more concentrated. (Southern Hemisphere by the sun s rays, concentrating the is tilted towards the sun.) heat over a smaller area and so heating that part of the Earth more. This hemisphere experiences summer. At Both hemispheres receive equal amounts of sunlight in March. It the same time, the other The Northern Hemisphere is autumn in Australia and spring hemisphere is tilted away tilts towards the sun in in the Northern Hemisphere. from the sun. The sun s rays June. It is winter in Australia and summer striking it are spread out in the Northern over a larger area so this Hemisphere. hemisphere heats up less, so the days are colder. This hemisphere experiences Sun winter. When neither hemisphere tilts towards The Southern the sun, which happens in Hemisphere tilts towards the sun in December. It is summer autumn and spring, each in Australia and winter in the receives the same amount of Northern Hemisphere. the sun s rays. So there is not Both hemispheres receive equal amounts of sunlight in September. It is much difference between, spring in Australia and autumn in the say, a Northern Hemisphere Northern Hemisphere. spring and a Southern Hemisphere autumn. Because of the tilt of the Earth, seasons change as the Earth completes its orbit of the sun.

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InveStIgAtIon 8.4 Pin

Day length in summer and winter

Pin

You will need: the equipment used for Investigation 8.3 2 pins with coloured heads

Pin

◗ Do this experiment in a darkened room; this

will help you see more clearly the contrast between light and dark.

Pin

◗ Hold the skewer vertically. Push two pins

into your sphere one about where Sydney is and the other directly above it at the top of the sphere, near the skewer. ◗ Set the spotlight up in a central place (such as on a table

DISCUSSION 1

Which pin comes into the light first when the southern half of the sphere leans towards the light? Ask your partner which pin moves out of the light first.

2

What does this tell you about the number of daylight hours in each hemisphere when the Southern Hemisphere tilts towards the sun?

3

Which pin comes into the light first when the northern half of the sphere leans towards the light? Ask your partner which pin moves out of the light first.

4

What does this tell you about the number of daylight hours in each hemisphere when the Northern Hemisphere tilts towards the sun?

5

What is the approximate length of day and night at the equator in each season?

6

Suggest why the sun never sets at certain times of year at the North and South Poles. What season is the Southern Hemisphere experiencing when the South Pole has several months of darkness?

you can move around). ◗ Stand to the left of the spotlight. Turn on the spotlight.

Hold the skewer so it leans away to the left from the vertical. The southern half of your sphere should be leaning more towards the light. ◗ Slowly turn your sphere in the light, making sure you

keep the skewer slightly tilted. Turn it in an anticlockwise direction. Watch what happens from side on. Watch the side of the sphere you can see as you turn it. A partner should watch the other side. ◗ Now stand to the right of the spotlight holding your

skewer tilted to the left as before. This time the northern half of your sphere should be leaning more towards the light. Repeat what you did in the previous step. ◗ Repeat the whole procedure above two more times. The

first time, look at what happens at each of the poles. The second time, look at what happens at the equator.

Activities REMEMbER

7 Identify the season in Australia when: (a) it is autumn in England (b) it is summer in Canada (c) the sun does not set at the South Pole.

1 Explain why we have day and night. 2 Explain why the sun rises in the east and sets in the west. 3 During which season in Australia does the Southern Hemisphere tilt towards the sun? 4 Explain why it is warmer on a summer s day than it is on a winter s day. 5 Explain why there are 365 days in each year but 366 days in every fourth year.

ThINk 6 Explain why the climate near the equator does not vary much from season to season.

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CREATE 8 Present a 3 5 minute lesson to the class using models to explain why we have seasons. eBook plus

9 Use the Day, night and time zones interactivity in your eBookPLUS to determine whether it is day or night in any location of the world at a specific time. int-0006 work sheets

8.3 Night and day 8.4 Star trails and seasons

8.5

the moon in motion Studying the moon The moon is, by far, the brightest object in the night sky. Its presence and changing appearance when viewed from Earth have raised many questions, inspired myths and legends, shaped our calendar and even determined the dates of some religious holidays. The moon takes the same time to complete one full turn around its own axis as it takes to orbit the Earth. For this reason only one face of the moon can be seen from the Earth. The face seen from Earth is much less mountainous and rugged than the other side. Unlike the Earth, the moon has no atmosphere. There is no air and there is no water on the surface. There is no wind and no rain. This means that there is no erosion of its cratered surface. Galileo Galilei is thought to be the first person to have used a telescope to study the moon, planets and stars. He made one of the first telescopes himself in 1610 after hearing rumours of the invention of a magnifying tube in Holland. While observing the moon s surface, Galileo observed: • large, dark and flat areas that he called maria (Latin for seas) • dark shadows that appeared to be made by mountains up to 6 kilometres high • numerous craters. Each of these features can be seen in the photograph above right. Until 1959, when the first images were transmitted from space, our knowledge of the moon depended on what could be seen

through telescopes from Earth. The table on the next page lists some of the important events that have occurred in the quest for knowledge about the moon. The most significant event, since Galileo s use of a telescope in 1610 to observe the moon, occurred on 20 July 1969. On that day, astronaut Neil Armstrong stepped down from the lunar landing craft Eagle, and as his foot touched the lunar soil he uttered the memorable words: That s one small step for a man, one giant leap for mankind.

The dark, flat areas in this photograph are called seas , though no water exists on the surface of the moon. Numerous craters are visible, believed to be the result of meteorite impacts.

PROFILE OF ThE MOON • Natural satellite of the Earth • Distance from Earth: 385 000 km (three days by spacecraft) • Diameter at equator: 3475 km (Earth s diameter is 12 750 km) • Period of orbit around Earth: 1 about 29 2 days • Period of rotation around its own 1 axis: about 29 2 days • Surface gravity: about one-sixth that of Earth • Surface temperature: ranges from 175 C in darkness to 125 C in sunlight

The word month comes from the Old English word mona, meaning moon. In early calendars, a month was the length of time between full moons. This period is called a lunar month. The modern calendar was not developed until the sixteenth century by Pope Gregory XIII. The Islamic, hebrew and Chinese calendars are still based on the lunar month.

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Probing the moon: some important events Year

InveStIgAtIon 8.5

Event

1610

Galileo Galilei used a telescope to observe the moon.

Observing the moon s surface

1850s

Astronomers took the first photographs of features of the moon.

1959

Luna 2 (USSR) became the first space probe to reach the moon when it crashed into the surface.

You will need: binoculars or small telescope

1959

Space probe Luna 3 (USSR) provided the first pictures of the previously unseen far side of the moon.

1964

Space probe Ranger 7 (USA) took the first close-up pictures of the moon.

1966

Luna 9 (USSR) became the first space probe to make a soft landing on the moon and take pictures from the surface.

1969

Apollo 11 (USA) carried three astronauts and the lunar lander Eagle to and from the moon. Astronauts Neil Armstrong and Buzz Aldrin became the first humans to walk on the moon. They spent three hours collecting soil and rocks, performing experiments and setting up equipment for further experiments.

1969– 1972

Apollo missions 12 and 14–17 (USA) successfully reached the moon, enabling more experiments to be completed. Apollo 13 failed, stranding the three astronauts in space. The astronauts were able to return safely to Earth by using the fuel and oxygen stored in their lunar lander.

◗ Observe the moon with a pair of

DISCUSSION

As the moon continues its orbit of the Earth, less of the lit face of the moon is visible from the Earth, leading to a quarter moon. Eventually, the near side is completely dark again and there is another new moon, and so the sequence continues. During the period between a new moon and a full moon, the moon is said to be waxing. As the phases move from

Phases of the moon The moon is visible from Earth only because it reflects light from the sun. As the moon orbits the Earth, it turns so that the same side of the moon always faces the Earth. At night, when you are in darkness, this side of the moon is sometimes completely bathed in sunlight; this is called a full moon.

binoculars or a small telescope. The best time to observe the moon is during a quarter moon (when about half of it is visible). Craters and mountains are difficult to see when there is a full moon because they do not cast shadows. ◗ Try to identify the seas (dark, smooth areas), mountainous areas and craters. ◗ Sketch and label what you see.

1

Which features were easiest to locate? How do you think the craters were formed?

2

full moon to new moon, it is said to be waning. The diagram below shows how the phases change during the 2912-day period between one new moon and the next.

Sun s rays

3 4

2

5

1

8

6 7

210

1

2

3

4

5

6

7

8

New moon

Crescent moon

uarter moon

Gibbous moon

Full moon

Gibbous moon

uarter moon

Crescent moon

Core Science | Stage 4 Complete course

InveStIgAtIon 8.6

Activities

Modelling the phases of the moon

REMEMbER 1 Identify the large, dark, flat areas on the moon that are visible from Earth. 2 Identify the phase of the moon that we see when: (a) the Earth is between the sun and the moon (b) the moon is between the sun and the Earth. 3 How many days are there between one new moon and the next?

You will need: projector or bright torch large, light-coloured ball ◗ Select one student

to act as the Earth and another to hold the ball representing the moon. ◗ Darken the room

and aim the projector or torch (the sun) at the ball (the moon). The student holding the moon walks around the Earth slowly in an anticlockwise direction, holding the same side towards the Earth .

DISCUSSION

ThINk

1

Sketch a plan view to show the positions of the sun , Earth and moon that result in: (a) a full moon (b) a gibbous moon (c) a quarter moon (d) a crescent moon (e) a new moon.

2

Describe the positions of the sun, Earth and moon when there is: (a) a full moon (b) a new moon.

4 Explain why there are more craters on the moon than the Earth, even though the Earth is a bigger target. 5 Explain why we never see the far side of the moon. 6 As Neil Armstrong stepped down from the lunar landing craft onto the lunar soil, his now famous words were heard by millions of people watching the event live on television. Propose why this step was such a giant leap for mankind .

◗ Try to identify each of the eight

phases of the moon, as they are seen by the person representing the Earth. Stop rotating briefly when each of the phases is identified so that the positions of the sun , Earth and moon can be recorded in a diagram.

eBook plus

possible so that you know where the sun is.

InveStIgAtIon 8.7 The changing moon

◗ Record the date, the time, and

◗ Copy the start of the table below

into your workbook. ◗ Observe the moon every third or

fourth evening over a period of at least two weeks. Observations over one whole month would be best. Try to make your observations as close to sunset as

the shape of the sunlit part of the moon. ◗ Each time you make an

observation, make a comment about the position of the sun compared with the moon, and why the moon has the shape that you have observed.

Observing the phases of the moon Date

Time

Shape of moon

Comment about position of sun and the shape of the moon

7 Use the Phases of the moon weblink in your eBookPLUS to watch a cartoon animation that will help explain the relationships between the moon, Earth and sun. 8 Use the Man on the moon weblink in your eBookPLUS to learn more about the historic 1969 moon landing. 9 Use the The Dish weblink in your eBookPLUS to view a trailer of the Australian movie The Dish and learn how the town of Parkes in NSW played an integral part in broadcasting the first ever images of a man walking on the moon. work sheet

8.5 The moon

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8.6

ocean tides Day after day, the waters of the Earth s oceans rise and fall against the coastlines of islands and continents. These changes in sea level are called tides. They are caused by the gravitational attraction of the moon and sun on the Earth s oceans. When the Earth rotates around its axis, its waters spin outwards. It is a bit like the way clothes fling out during the spin cycle in a washing machine. This action creates a bulge of water around the Earth. Why, you might ask, does the bulge not fly out into space? It is held back by the Earth s gravity.

Suck in . . . bulge out The size of the bulge is not the same everywhere. The bulge in the oceans gets larger and smaller

ebb and flow High tide As the moon orbits the Earth, its gravity most affects the side of the Earth facing it – the closest side. The ocean bulge on that side is pulled out even further.

Low tide The water that makes up the high tides is sucked from oceans in between.

Moon Earth

High tide The moon’s gravity also attracts the Earth itself. This causes the Earth to pull away from the water surface on this side. As a result, these oceans also bulge out more, though not quite as much as the side facing the moon. Looking down on the Earth from above the North Pole. As the Earth rotates, different places experience high tide.

because of the pull of gravity due to the sun and the moon. It is the change in position of the bulge that we call tides. High tide occurs where there is a bulge. Low tide occurs where there is no bulge. Gravity is a force of attraction between any two bodies in the universe that have mass. How big this force is depends on two things: the mass of the bodies and how close they are. The sun and the moon both pull on the Earth. Even though the mass of the moon is 27 million times less than the sun, its gravitational pull on the Earth is greater than that due to the sun because it is so much closer to Earth. In theory, every place on Earth has two high tides and two low tides on most days. Sometimes, though, other factors cause strange events to happen. For example, the extremes of tides in the Bay of Fundy in Nova Scotia are caused by its geography.

High and low tide in the Bay of Fundy. Its tidal range over 16 m is the biggest in the world. The bay has a very wide mouth that allows a lot of water to rush in as the tide rises. But the bay gets much narrower further inland. The huge volume of water has nowhere to go but up!

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Spring and neap tides Twice each month, the moon, sun and Earth line up. This occurs when there is a full moon and at the time of a new moon. At these times, the pull on the Earth and its waters is much stronger as the gravity of the sun and moon combine. Hence, the ocean bulges contain even more water. This means the tidal range is much greater. These tides are called spring tides.

About seven days after a spring tide, the moon and sun are at right angles to each other with respect to the Earth. In this position, their forces of gravity work against one another, rather than together. So, the tidal range is narrow. These tides are called neap tides.

First quarter Sun’s rays Neap tide New moon

Full moon Spring tide

Spring tide

Neap tide

Third quarter

Each month there are two spring tides and two neap tides.

Activities REMEMbER 1 Define the term gravity . 2 Explain why the moon s gravity has a stronger pull on Earth than the sun s. 3 With the aid of a diagram, distinguish between a spring tide and a neap tide.

7 Imagine a pier in the Bay of Fundy that is two metres above the water level at high tide, and you tie a small fishing boat to the pier using a two-metre rope. Draw a labelled diagram to show the position of the boat at high and low tides.

CREATE 8 Design a role-play involving at least four people to clarify how the movement of the Earth around the sun, and the moon around the Earth, cause tides. A narrator could be used to give a commentary of the role-play.

ThINk 4 What sort of tide occurs when there is a full moon? Explain. 5 If the height of the highest tide on a particular day was 6.5 m and the tidal range was 4.2 m, calculate the height of the lowest tide.

eBook plus

9 Use the Tides interactivity in your eBookPLUS to watch how changing the positions of the sun and the moon affects the tides on Earth. int-0225

6 Deduce why one high tide on any given day is always higher than the other one.

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8.7

Lunar and solar eclipses Lunar eclipses Lunar eclipses occur when the moon moves into the Earth s shadow. In a total lunar eclipse, the moon and Earth are lined up so that the whole of the moon is in shadow for a while. If they are not completely aligned, only a part of the moon will be in shadow; this is called a partial lunar eclipse. During a total lunar eclipse, the moon looks as though it goes through all its different phases in one night. However, this is not the case; in fact, it is a full moon all night long. Lunar eclipses can occur only when the Earth is between the sun and the moon, and that can happen only during a full moon. Why doesn t an eclipse occur every full moon? The sun, Earth and moon line up exactly only a few times a

year. If a straight line was drawn between the sun and the Earth, the moon s orbit is usually offset from it by about 5 . So, at most times when there is a full moon, the moon misses the Earth s shadow it passes above or below it. The moon usually looks white because it reflects white light from the sun; however, during an eclipse, the moon takes on a red tinge. This is because, during a total eclipse, the only light that reaches the moon first passes around the edges of the Earth and so has passed through the Earth s atmosphere. The Earth s atmosphere scatters the blue light from the sun leaving mainly red light to illuminate the dimly lit moon.

Penumbra Sun

Umbra

Moon Penumbra

Earth

Total lunar eclipse

Penumbra Moon Sun

Umbra Earth

Partial lunar eclipse

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Penumbra

The Earth s shadow makes the moon appear to change phases during a total lunar eclipse. Note the red tinge of the moon at the height of the eclipse.

Solar eclipses Solar eclipses occur when the moon lies between the sun and the Earth. This means that the moon s shadow falls on the Earth. People on Earth within the umbra of the moon s shadow see a total eclipse of the sun. Those within the penumbra see a partial solar eclipse. Total solar eclipses are not seen often as the moon casts only a narrow shadow on Earth. The umbra may be only about 100 km wide. It may fall in the middle of an ocean. It may even miss the Earth altogether. During a total eclipse, the area within the umbra on Earth becomes quite dark for a few minutes. You might even see some stars during the day! The sun s corona, or atmosphere, can still be seen. The corona is not normally seen because the sun is so bright. CAUTION You must NEVER look directly at an eclipse of the sun even a partial eclipse. You could permanently damage your eyes. Sunglasses will not protect you.

Penumbra Moon Earth

Sun

Umbra Penumbra

Total and partial solar eclipses

A total solar eclipse the sun s light is blocked as the moon passes in front of it.

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InveStIgAtIon 8.8 The ancient Chinese believed that solar eclipses occurred when a giant dragon ate the sun. They thought that if they made enough noise they could frighten the dragon. The frightened dragon would then spit the sun out, bringing daylight back.

Fuzzy shadows

card or bare wall. Observe the shadow of a coin as you move it between the light source and screen.

◗ Rotate the globe a little (think

carefully about which way to turn it) and note what happens to the shadow.

Modelling solar and lunar eclipses You will need: projector globe tennis ball attached to string

shadows. ◗ Create a shadow that is dark in

the centre and partially dark on the outside. This is the type of shadow cast on the Earth by the moon.

You will need: torch white card or a bare wall to act as a screen coin ◗ Use a torch to cast light on a white

InveStIgAtIon 8.9

◗ Create sharp shadows and fuzzy

◗ To simulate a lunar eclipse, move

the tennis ball to the opposite side of the globe from the projector. Suspend it so that it is partly in the shadow of the globe.

DISCUSSION 1

Where does the coin need to be to create a sharp shadow?

2

Where does the coin need to be to create a fuzzy shadow?

3

Draw a diagram of this fuzzy shadow.

Activities REMEMbER 1 Outline the difference between a solar eclipse and a lunar eclipse. 2 Explain why you must never look directly at a solar eclipse.

◗ Darken the room and aim a beam

of light at the globe. ◗ To simulate a solar eclipse,

suspend the tennis ball (moon) between the projector (sun) and the globe (Earth) as shown below. Ensure that you keep your own shadow off the globe. Light from projector

DISCUSSION

ThINk

1

Draw a diagram to show the initial positions of Earth, moon and sun in your model of a solar eclipse.

3 Explain why total solar eclipses are much less frequent than partial solar eclipses.

2

During which phase of the moon does a solar eclipse occur?

3

When you rotate the globe, does the shadow move from east to west or from west to east?

Tennis ball

Modelling a solar eclipse

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4

Draw a diagram showing the positions of the Earth, moon and sun in your lunar eclipse model.

5

During which phase of the moon does a lunar eclipse occur?

4 Propose why a total lunar eclipse occurs only when there is a full moon, and why a solar eclipse occurs only when there is a new moon. eBook plus

5 Test your knowledge of solar and lunar eclipses by completing the Eclipses interactivity in your eBookPLUS. int-0207 work sheet

8.6 Eclipses

8.8

PRESCRIbED FOCUS AREA history of science

early ideas in astronomy Astronomy is the study of stars, planets and other objects that make up the universe. The history of astronomy goes back several thousand years. Almost all ancient cultures had stories about how the universe was created, what it was like, who created it, and how the Earth and humans got here.

Indigenous Australian astronomy The Yolngu people of Arnhem Land explain the sunrise, sunset and movement of the sun through the sky in terms of Walu, the Sun-woman. Walu lights a fire each morning, which we see as the dawn. Holding her torch, she travels across the sky from east to west. At the end of her journey to the western horizon, she goes underground for her return journey east, back to her starting point at her morning camp. Walu uses red ochre to decorate her face and body; when some of the red dust falls onto the clouds, this creates the red sunrise and red sunset. The Yolngu people explain the phases of the moon through the story of Ngalindi and his wives. At the time of the full moon, Ngalindi is a fat, lazy man. His wives punish him by attacking him with an axe, and he is seen as a waning moon as parts of him are chopped off. Unable to escape his wives, Ngalindi dies of his wounds, and this is the time of the new moon. He rises from the dead after three days and is seen as the waxing moon as he again grows round and fat. Two weeks later, his wives punish him again, and the cycle repeats.

Other dreamtime stories show that the Yolngu people knew about the relationship between tides and the moon s motion. They explain that, at high tide, water fills the moon as it rises. When the water flows back out of the moon, the tides fall. The moon is empty for three days before the tide rises again, when the moon is again filled with water.

Among thousands of beautiful rock engravings in Ku-ring-gai Chase National Park in Sydney s north is this one (above), believed by some scientists to represent two figures below a crescent moon (right).

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Milky Way was mayu, meaning river. This celestial river was said to join up with the Urubamba River in the waters of a great cosmic sea that encircled the Earth. The Incans believed that the celestial river, the Milky Way, was the source of rain on Earth as it passed through the night sky. The Southern Cross constellation contained the most important stars to the Incas since it could be used to show the points of the compass, with the most distant star pointing south when visible in the sky.

Rock engravings at Ngaut Ngaut, South Australia, which are said to represent lunar cycles. There are many examples like this throughout Australia that suggest that astronomy is an important part of many Australian Aboriginal cultures.

A dreamtime story of the Warlpiri people explains solar and lunar eclipses. When the Sun-woman and Moon-man embrace, the Sun-woman is covered over and this is seen as a solar eclipse. At other times they argue and the Moon-man is hidden from view as the Sun-woman chases and threatens him. This is seen as a lunar eclipse. These stories show that the Warlpiri people understood that eclipses relate to the motion of the sun and moon across the sky, they occur when their paths meet.

Incan astronomy For about 300 years, from the 1200s until the Spanish conquistadors invaded in the 1500s, much of South America around Peru was ruled by the Incan empire. The Incas watched celestial events with the naked eye to develop a wide range of astronomical ideas. At Cusco, the astronomical centre of their empire, the Inca constructed a series of stone towers to mark the points of sunrise and sunset on important days. These included the summer solstice (longest day of the year) and the winter solstice (shortest day of the year). The Incas created an accurate annual calendar based on the positions at which the moon rose and set on the horizon, as well as observations of the phases of the moon. The Inca had a deep knowledge of the stars and constellations, which they observed and named. For example, the Incan name for the bright stars of the

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Most historians agree that the Incans had a calendar based on the observation of the sun and the moon and their relationship to the stars. Names of 12 lunar months are recorded.

Ancient Greek astronomy Much of our current scientific knowledge was developed in Europe, so it has a Western influence. The ancient Greeks provided many of the early ideas from which modern astronomy was developed. Actually, the word astronomy comes from Greek terms for law and order. The Greeks were not the first culture to study the night sky but their ideas were widely accepted throughout Europe for hundreds of years. The Greeks discovered that the Earth was spherical; the Greek philosopher Eratosthenes measured the circumference of the Earth to within about 300 kilometres of the true value. In the fourth century BC, Aristotle was one of the most influential philosophers in Greece. He believed that the sun and moon revolved around the Earth, which was the centre of the universe. He used this philosophy to develop what we call a geocentric model. This model was easily accepted at the time

as people who studied the night sky saw celestial bodies passing over the Earth. In the following century, Aristarchus developed his heliocentric model. He stated that the sun was fixed and all the planets, including the Earth, orbited it along circular paths. He noted that, once a day, the moon revolved around the Earth and the Earth rotated on its axis.

Moon Earth

Mars

Venus Jupiter

Sun

Mercury

Claudius Ptolemy (AD 85 165), the last of the great classical astronomers Sphere of stars

Saturn

Jupiter

Aristarchus s heliocentric model

Aristarchus s model did not gain wide acceptance until Copernicus redeveloped it 2000 years later. This sun-centred theory would have defied common sense at the time because we do not feel the Earth spinning or moving through space. Hipparchus (190 120 BC) was the greatest astronomer of his time. He made extensive observations of star positions and is credited by some with the production of the first known catalogue of stars. Like Aristotle, Claudius Ptolemy (AD 85 165) proposed a geocentric model of the universe. He maintained that the five satellites discovered up until then, namely Mercury, Venus, Mars, Jupiter and Saturn, together with the moon and the sun, revolved around the Earth. Ptolemy s model attempted to explain why some of the planets viewed over many nights appeared to travel backwards when compared with other planets or to the background stars. He suggested that the planets travel in small circular orbits (epicycles), while also orbiting around the Earth, and that the stars occupied the outermost circle.

Mars Moon

Venus Sun

Earth Mercury

Saturn

Ptolemy s model of planetary motion

Renaissance astronomy The Renaissance was the period of European history after the Middle Ages from the 1400s to the middle 1600s. It was a period of great scientific advancement in many areas including astronomy. Nicolaus Copernicus (1473 1543) was a Polish astronomer who, like Aristarchus, proposed that the sun is stationary near the centre of the universe.

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In addition, his theory proposed that the Earth rotated on its axis once daily and orbited around the sun once a year. He argued that the planets orbit the sun but rejected Ptolemy s idea of epicycles to explain what appeared to be reverse motion of some Moon of the planets. Instead, he Mercury suggested that the greater the radius of a planet s orbit, the longer it took for the planet to Sun orbit around the sun. However, most sixteenthcentury readers could not accept the concept of a moving Earth, and so the core ideas of his model were Copernicus s heliocentric model Nicolaus Copernicus rejected. Dutch astronomer Johannes Kepler (1571 1630) supported Copernicus s heliocentric model of the solar system and applied mathematics to the observations of astronomers who preceded him. Kepler abandoned the idea that planets travelled in circular orbits at a constant speed. Instead he proposed three theories to explain the motion of planets. The first two were published in 1609 in his work Astronomica nova (New Astronomy). His theories have been tested over centuries and, having stood the test of time, have gained the status of scientific laws. In Kepler s first law he describes the motion of planets as ellipses. (Note: In the diagram below, the flatness of the ellipse has been exaggerated.) Kepler s second law explains how the speed of an orbiting planet depends on its position in the elliptical orbit. Kepler s third law describes how planets more distant from the sun take longer to orbit the sun.

Saturn Stars

Jupiter Mars Earth Venus

Johannes Kepler Elliptical path Planet travels faster when it is closer to the sun.

Sun Planet travels slower when it is further from the sun. Kepler s laws of planetary motion are based on elliptical planetary orbits.

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Galileo Galilei (1564 1642) of Italy was originally a professor of mathematics but, by the time of his death, he had became one of the most influential astronomers of the Renaissance.

planet, thus weakening the hold of Ptolemy s model. The Earth was clearly seen not to be at the centre of all planetary motion.

The moons of Jupiter as drawn by Galileo on successive nights

Galileo s published works contradicted the geocentric view of the universe put forward by Aristotle and Ptolemy and conflicted with powerful authorities in the church. Eventually he was forced to publicly recant his belief in the Copernican system and lived out his life under house arrest working on a better understanding of the physics of moving objects. While Galileo did not propose his own model of the universe, his observational, experimental and theoretical work provided the evidence that eventually led to rejection of the Aristotelian Ptolemaic geocentric model of the universe.

Activities REMEMbER 1 How do the Yolngu people of Arnhem Land explain the existence of sunrise and sunset? Galileo Galilei

2 Besides dreamtime stories that still survive today, what other evidence is there that Aboriginal peoples studied the night sky?

When Galileo heard about a new optical device, the telescope, in 1609 he quickly built his own version. He then used it and, later, more sophisticated telescopes to systematically study the night sky. He observed the moon and described the lunar surface as uneven, with craters and mountains, for the first time ever. Galileo s observations of the planet Jupiter over successive nights revealed four star-like objects in a line with it. The objects moved from night to night, sometimes disappearing behind or in front of the planet. Galileo correctly inferred that these objects were moons of Jupiter and orbited it just as our moon orbits Earth. Today, these four moons are known as the satellites Io, Europa, Ganymede and Callisto. For the first time, objects had been observed orbiting another

3 The Incan calendar, like our own, is based on astronomy. Outline the information used to help create such a calendar. 4 What was at the centre of Ptolemy s model of the universe? 5 Explain why a geocentric model of the solar system would have made much more sense to early astronomers than a heliocentric one.

ThINk 6 Describe the limitations that ancient cultures had on their study of the night sky and outline the conclusions that they drew. 7 What observations suggested to Renaissance astronomers that a heliocentric model of the solar system must be correct? 8 Explain why Galileo s ideas were so controversial at the time. 9 During the Renaissance, new theories about our solar system developed rapidly and previous ones were rejected. In science, why are existing theories replaced by new ones?

CREATE 10 Create your own dreamtime story to explain one of the following phenomena. ◗ Tides ◗ Sunrise and sunset ◗ Eclipses ◗ The movement of stars and planets in the night sky work sheet

8.7 Astronomical history

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8.9

Rocks in space The solar system contains many objects other than the sun and the planets. All of the planets except Mercury and Venus have large bodies called satellites revolving around them. Earth has only one natural satellite. Natural satellites are called moons. Many of these moons have been discovered during the past 25 years by space probes such as Pioneer and Voyager.

Asteroids Thousands of small, irregular objects called asteroids, or minor planets, revolve around the sun just like the major planets. Most of them are between the orbits of Mars and Jupiter a region sometimes called the asteroid belt. The largest asteroid, Ceres, is about 970 kilometres in diameter. The smallest known asteroids are only about one kilometre across. The orbits of asteroids are more elliptical in shape than the orbits of the planets. This brings them quite close to the sun and to the orbit of Earth. In 1991, a small asteroid passed within 170 000 kilometres of Earth. That is less than half the distance from the Earth to the moon and dangerously close. It passed Earth at a speed of about 72 000 kilometres per hour. In 1993, the space probe Galileo, on its way to Jupiter, discovered the first known moon of an asteroid. A body of rock about one kilometre across was photographed orbiting a potato-shaped asteroid called Ida. It is likely that many asteroids have moons. Most asteroids have irregular shapes. Tail

Comets

Jupiter and three of its moons

The moons vary greatly in size. Deimos, the smaller of the two moons of Mars, is only about 10 kilometres in diameter. The largest known moon in the solar system is Ganymede, one of the 16 moons of Jupiter. It is larger than the planet Mercury. Some moons, like the Earth s moon, are cratered while others are quite smooth.

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Coma

Comets are balls of rocky and metallic particles amid ice and frozen gases. Most of the mass of a comet is in nucleus. A bright glowing its nucleus tail of dust and gases becomes larger as the comet moves closer to the sun. Up to millions of kilometres long, the tail is blown away from the sun by the solar wind.

Nucleus

Comet s orbit

Sun

The orbit of a comet is long and narrow. The tail gets longer as the comet approaches the sun.

The orbits of comets are longer and narrower than the orbits of the planets. It is believed that comets are formed from dust and ice in the cold, outer regions of the solar system. The most famous comet is Halley s comet, named after Sir Edmond Halley, who correctly predicted that it would return every 76 years. Its orbit extends beyond the orbit of Neptune. We see it as it passes near Earth on its path to and from the sun. This last happened in 1986.

InveStIgAtIon 8.10 Meteorite impact You will need: ice-cream container or bucket sand water metre ruler compass or pointers from a geometry set large marble or steel ball

Meteoroids

◗ Half-fill the container with sand.

Occasionally people see bright streaks of light called shooting stars in the night sky. The streaks of light are called meteors. They are created when a lump of rock or metal burns up as it passes through the Earth s atmosphere. These lumps of rock or metal that travel around the solar system orbiting the sun are called meteoroids. Most of those that cross the path of the Earth s orbit are so small that they burn up completely before they reach the ground. Those that are large enough to reach the ground are called meteorites. Meteorites hit the ground with speeds of up to 70 kilometres per second, or 252 000 kilometres per hour. They are very hot and explode on impact, leaving craters much bigger than themselves. The Wolf Creek crater in Western Australia, pictured below, has a diameter of about 850 metres. The crater s rim rises about 25 metres above the surrounding plains and its floor is about 50 metres below the rim. Some scientists believe that a meteorite caused the extinction of the dinosaurs about 65 million years ago. They believe that the impact of the meteorite lifted tonnes of dust into the atmosphere, blocking out sunlight from the surface for several months. This would have killed all plants and changed the climate, making it impossible for larger animals like dinosaurs to survive.

◗ Add a little water to the sand and mix it to make it

damp but not too wet. ◗ Design an investigation, using the equipment listed

above, to examine how the speed of impact of a meteorite affects the diameter of the crater that is created. Be sure to collect quantitative data. ◗ Record your data in a suitable table and plot your data

as a line graph.

DISCUSSION 1

Identify the independent and dependent variables in your investigation.

2

Identify two important controlled (constant) variables in your investigation.

3

Write a suitable conclusion to your investigation.

Activities REMEMbER 1 Identify the name given to natural satellites of planets. 2 Describe the asteroid belt. 3 Describe what comets are made of. 4 Define the term meteorite . 5 Explain the difference between a meteor and a meteoroid.

ThINk 6 Explain the difference between a planet and a moon. 7 Explain how asteroids are different from moons. 8 In which year is Halley s comet next likely to be visible from Earth? 9 Explain why the tail of a comet gets larger as it gets closer to the sun. The Wolf Creek meteorite crater in Western Australia

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LooKIng BACK 1 Explain how a day on Jupiter can be about 10 hours long. 2 Identify why our knowledge of the planets has increased so rapidly over the past 30 years. 3 The atmospheres of Mercury and Venus are very thin. Describe the effect this would have on the temperature on those planets.

(d) Which position(s) of the moon would result in a quarter moon? (e) Which position(s) of the moon would result in a full moon? 8 The photograph below shows the Earth as it is seen from the moon.

4 The diagram below shows half of the Earth in sunlight while the other half is in darkness. Which Australian season is represented in the diagram. Explain how you know. 23.5o North Pole Light from the sun

Equa tor

Light from the sun

South Pole Axis

23.5o

Photographs like this one of the Earth were taken from the Apollo 8 spacecraft in 1968 as it orbited the moon.

5 How many times does the moon rotate around its own axis while completing a single orbit of the Earth? 6 Calculate how many rotations the Earth has completed since you were born. 7 The diagram below shows the moon in eight different positions during an orbit around the Earth. (a) Copy the diagram and shade the parts of the Earth and moon that are in darkness. (b) How long does it take the moon to complete a single orbit? (c) Why is it not possible to see a new moon during the day?

(a) Why is the Earth visible even though it does not emit its own light? (b) Would you expect the Earth to always be visible from the part of the moon that faces it? Explain your answer. 9 The stars appear to change their positions during each night and during each year. Explain why the stars appear to move in circular arcs during the night.

Sun s rays

C B

D

A

E

F

H G The moon s orbit around the Earth as seen from above Antarctica

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3 The diagram below shows the Earth orbiting the sun.

10 Distinguish between a neap tide and a spring tide. 11 The table below shows the high and low tide heights at Bondi beach over a 24-hour period of time. Time

D

Height (m)

2.30 am

0.37

9.05 am

2.05

3.52 pm

0.1

9.53 pm

1.37

C

A Sun

(a) Calculate how many hours pass between two consecutive high tides. (b) Calculate how many hours pass between two consecutive low tides. (c) Explain how high tides occur. (d) Deduce why one high tide is lower than the other.

B

12 (a) Identify which of these photographs shows an eclipse of the sun and which shows an eclipse of the moon.

At what positions does Australia experience summer and winter respectively? A A and C B C and A C B and D D D and B (1 mark) 4 Shooting stars are A meteors. B comets. C supernova stars. D stars.

(1 mark)

5 (a) Which astronomer developed the model of the universe shown in the diagram below? (1 mark)

Cel es tia l

(b) Use labelled diagrams to explain how each eclipse occurs. 13 Identify the region of the solar system where you would find the most asteroids.

sp

re he

Jupiter Sun Mercury

Saturn Mars Venus

Earth

TEST YOURSELF

Moon

1 The length of a day on the planet Venus is 243 Earth days. The length of a year on Venus is only 225 Earth days. This means that A it takes 243 days for Venus to orbit the sun. B Venus completes a rotation in 243 Earth days. C Venus completes a rotation in 225 Earth days. D it takes 225 days for the sun to orbit Venus. (1 mark) 2 During a solar eclipse: A the moon is blocked out by the sun. B the sun is blocked out by the Earth. C the moon is blocked out by the Earth. D the sun is blocked out by the moon.

(b) Identify where the stars are in this model. (1 mark) (c) Explain why this model of the universe was so well accepted for almost 1500 years. (4 marks) work sheets

(1 mark)

8.8 Solar system puzzle 8.9 Solar system summary

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225

StUDY CHeCKLISt Components of our solar system ■ identify the planets in the solar system in order 8.1 ■ identify some features of each of the planets 8.2 ■ compare the sizes of the planets in the solar ■ ■ ■ ■ ■ ■

system 8.1 compare the distances between the planets in the solar system 8.1 describe the orbits of the planets 8.1, 8.2 identify the forces keeping the planets in orbit 8.3 explain why Pluto is no longer considered to be a planet 8.1 outline features of the sun 8.3 distinguish between comets, meteors, meteorites and meteoroids 8.9

ICt eBook plus

SUMMARY

Interactivities Day, night and time zones This interactivity enables you to calculate the time of the day or night, anywhere in the world, on any given date and time. A full world map is included with the international dateline, time zones and lines of latitude and longitude clearly marked.

Movements of the planets, moons and sun ■ outline the ways in which the Earth moves 8.4 ■ explain night and day in terms of Earth s rotation 8.4 ■ explain, in terms of the tilt of Earth s axis and ■ ■ ■ ■ ■ ■

its revolution around the sun, what causes the seasons 8.4 describe the surface of the moon 8.5 identify the phases of the moon and explain how they occur 8.5 describe the effects of the sun and the moon on the Earth s oceans 8.6 distinguish between neap and spring tides 8.6 describe the appearance of the sun during a solar eclipse and the moon during a lunar eclipse 8.7 explain how solar and lunar eclipses occur 8.7

Searchlight ID: int-0006 Tides Learn about high and low tides by adjusting the position of the moon in relation to the sun and Earth to see the resulting tidal bulge. A worksheet is attached to further your understanding.

history of science ■ identify some of the ideas about the universe that different cultures have contributed to science throughout history 8.8 ■ describe ideas developed by different cultures (using examples, including those developed by Aboriginal peoples) to explain the world around them 8.8 ■ describe some models and theories that have been considered in science and then modified or rejected as a result of available evidence 8.8

Searchlight ID: int-0225 Eclipses This interactivity challenges you to test your knowledge of eclipses by matching each description to its correct term. Instant feedback is provided. Searchlight ID: int-0207

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9

Energy

Fireworks are noisy, colourful and bright. They contain a fuel that explodes when ignited, creating a loud explosion. Powdered metals are included in the mixture of explosives to produce the brightly coloured sparks we see. Energy transformations take place when fireworks explode, producing sound and light.

In this chapter, students will 9.1 ◗ identify situations or phenomena

that demonstrate different forms of energy ◗ use models to describe different forms of energy ◗ identify objects with energy due to motion (kinetic) or other properties (potential) ◗ apply the Law of Conservation of Energy to account for the total energy involved in energy transfers and transformations 9.2 ◗ describe the processes of

heat transfer by conduction, convection and radiation 9.3 ◗ describe light as a form of energy

not requiring a medium ◗ describe sound as a form of

energy requiring a medium 9.4 ◗ describe technological

developments that use the principles of sound energy.

Fireworks display over Sydney during New Year s Eve celebrations

9 Energy Thinking about energy 1. In groups create a mind map around the central theme of energy. Begin by brainstorming different types of energy. Then continue your mind map outwards to include examples of devices that use or release each type of energy. The mind map has been started for you.

Energy

Light

2. Conduct an audit of your house. Walk around the house and speak to your parents to list features that keep your house: • cool in summer • warm in winter. 3. If you were to renovate your house, how could you improve how well it keeps you cool in summer and warm in winter? 4. The two photos on the right show houses designed for a hot climate and a cold climate. Identify which is suited to which climate. Compare the two houses by listing features of each that make them suited to their respective climates 5. You have 100 mL of water in a beaker at 20 C and a second beaker with 100 mL of water at 80 C. Predict what would happen if you combine the two samples in the same beaker. Test your prediction by carrying out this experiment. 6. Draw up a table with two columns. In the first column, list objects that give out light. In the second column, outline how the light is produced or identify the source of energy. 7. Place your fingers over your Adam s apple at the base of your throat while you make a deep humming sound. What do you feel? Use that observation to try to explain how the humming sound is produced.

Light globe

9.1

Energy transformations What is energy? Have you ever felt like you were full of energy ? If so, you probably felt like moving around or doing something active. Objects can have energy too. We cannot always see the energy that they possess, but we can often observe the effects of objects gaining or losing energy. Winding up a toy or pulling back the string of an archery bow gives these objects lots of energy.

faster an object moves, the more kinetic energy it has. Kinetic energy also depends on the mass of the moving object; a truck travelling 60 kilometres per hour has more kinetic energy than a car travelling at the same speed. Moving objects can do work by travelling distances or by colliding or pushing other objects. Another common type of energy is gravitational energy. Objects above the ground have gravitational energy because the Earth s gravitational force can cause them to fall to Earth. The higher an object, the more gravitational energy it has. Often, objects with gravitational energy do not appear to have any energy at all. However, they still

eBook plus

eLesson

Energy in disguise Did you know that all energy is constantly being transformed and transferred from one object to another? There’s more going on in your world than meets the eye. eles-0063

have the potential to do work and so the energy is stored. Gravitational energy is an example of potential energy. Pole vaulters at the top of their jump have a great deal of gravitational potential energy that is transformed to kinetic energy as the vaulter falls back to the ground. Other examples of potential forms of energy are elastic energy (such as when a rubber band is stretched), nuclear energy (such as that in a nuclear bomb) and chemical energy (evident in chemical reactions).

Objects at a height above the ground have stored energy called gravitational potential energy. The higher an object is, the more gravitational potential energy it has.

Energy is defined as the ability to do work. In some cases, energy may cause an object or other nearby objects to move like a wind-up toy or the arrow fired from a stretched bow. The energy of an object can also give objects the potential to move, or it can create sound, heat or light.

Types of energy There are several types of energy that an object might possess. One common type of energy is kinetic energy. All objects that are moving have kinetic energy. The

All objects that are moving have kinetic energy. The faster an object moves, the more kinetic energy it has. Moving objects can do work by travelling distances or by colliding with other objects.

9 Energy 229

Many other types of energy are important in our daily lives. These include sound energy, heat energy, light energy and electrical energy.

Nuclear Gravitational

T

L I A

P O T E

N

Kinetic

Chemical

Types of energy

Electrical

Elastic

Light

Sound

Heat

The chemical energy in household batteries is an example of potential energy that powers many household devices.

Types of energy changes involved in bouncing on a trampoline 1. At the very top of a jump, the bouncer is momentarily stopped she has no kinetic energy. But she does have gravitational potential energy due to her height above the trampoline. As the force of gravity pulls the bouncer down, some of her potential energy is transformed into kinetic energy.

3. At this point, the bouncer pushes off the trampoline. The elastic potential energy is transformed back into kinetic energy and some gravitational potential energy.

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2. As the bouncer strikes the trampoline, her kinetic and gravitational potential energy are transferred to the trampoline s surface and springs. The energy is momentarily stored in the springs. It is called elastic potential energy.

4. As the bouncer rises again, her kinetic energy is transformed into gravitational potential energy again. At the top of the jump, the bouncer has no kinetic energy, just gravitational potential energy.

How much energy? Energy is measured in a unit called the joule (J), named after the British physicist James Joule (1818 1889). The kinetic and gravitational potential energy of objects can be calculated using a couple of simple formulae.

Calculating gravitational potential energy

Calculating kinetic energy

Gravitational potential energy of an object = mgh where: • m represents the mass of the object (in kg) • g represents the object s acceleration when falling (10 metres/second2 on Earth) • h represents the object s vertical height (in metres). For example, to calculate the potential energy of an 80 kg skier on a chairlift 20 m off the ground: potential energy = 80 kg × 10 m/s2 × 20 m = 16 000 joules or 16 kilojoules

Kinetic energy of a moving object = 12 mv2 where: • m represents the mass of the moving object (in kg) • v represents the object s speed (in metres/second). For example, to calculate the kinetic energy of a cyclist and bicycle with a total mass of 100 kg travelling at 5 metres/second: kinetic energy = 12 × 100 kg × (5 m/s)2 = 1250 joules or 1.25 kilojoules

InvEstIgatIon 9.1 Bosshead

Comparing energy use with a block and tackle A block and tackle is a system of pulleys that allows heavy loads to be lifted with minimal effort. In this experiment you will compare the energy use with and without the use of a block and tackle for lifting heavy loads. You will need: 500 g or 1 kg load 5 N or 10 N spring balance string scissors ruler retort stand, bosshead and clamp 2 double pulleys

Clamp ulley

pring balance

Block and tackle

etort stand

oad

◗ Attach the load to the spring balance with string and

record the force needed to lift the mass by hand. ◗ Calculate the work done (in joules) to lift the mass 0.1 m

(10 cm) by hand using the formula: work = force × distance (in metres)

DisCussion 1

Compare the energy used in lifting the mass using a block and tackle with that used when lifting the mass by hand. If there was a difference suggest why.

2

Compare the force required to lift the mass with the block and tackle with that required when lifting the mass by hand. What advantages does a block and tackle have in lifting loads?

3

If 50 J of work is done to lift a student up by 10 cm, use your results to estimate how much work would be needed using a block and tackle.

◗ Construct a block and tackle as shown at right. ◗ Attach the spring balance to the end of the string and

record the force needed to lift the mass using the block and tackle. ◗ Calculate the work done in joules to lift the mass 0.1 m

(10 cm) with the block and tackle using the formula above. ◗ Draw up a suitable table to record the force, distance

and work done with and without the block and tackle. Be sure to use appropriate units for each measurement.

9 Energy 231

Transferring and transforming energy Energy can be transferred to another object or to the surrounding environment. For example, if you hug a hot-water bottle, the heat is transferred from the bottle to you. The heat has been transferred from one object to another, but has not changed form. Energy can also be transformed into other forms of energy. For example, the electric motor in a hair dryer transforms electrical energy into mechanical energy (the energy that causes the parts to move). Sometimes, during a transformation of energy, not all of the energy is transformed into useful forms. Some of the energy may be transferred to the surrounding environment as unwanted heat, or transformed to

light or sound. For example, not all of the energy you use to ride a bike up a very steep hill goes into making the pedals move. Some of the energy is wasted when your body gives off heat.

The Law of Conservation of Energy When objects stop moving, they no longer have kinetic energy. But the energy is not lost. Instead, it is changed (transformed) into another type of energy or moved (transferred) to another object. The Law of Conservation of Energy tells us that the amount of energy in the universe is always the same. Energy is never lost and energy is never created. Sometimes it is difficult to track where the energy goes. For example, most of the kinetic energy when you clap your hands is transferred to air as sound, but you might also notice that your hands get warm. This demonstrates that some of the original energy is transformed to heat.

In a game of pool, a moving white ball is used to push another ball. The kinetic energy of the white ball is transferred to the coloured ball.

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A clock radio transforms electrical energy into sound energy when the alarm or radio is heard and into light energy in the time display.

Electrical energy (in the form of an electric current) is passed through the wire in the centre of the bulb (the filament), and is then transformed into heat and light energy. The light energy is the desirable energy, but the heat is considered wasted energy because it has no benefit to us in this system.

◗ Heat the corn until the popping stops.

InvEstIgatIon 9.2

◗ Turn off the Bunsen burner, put the saucepan on the

Popping corn You will need: saucepan with lid popping corn matches

heatproof mat to cool and take the lid off the saucepan to observe any changes. ◗ Record your observations.

vegetable oil Bunsen burner heatproof mat

◗ Pour a little cooking oil in the saucepan. ◗ Pour enough popping corn into the saucepan to cover

DiScuSSion 1

What type of energy did the popping corn have before heating? What type did it have during heating?

2

Even though you could not see the corn when the lid was on, how do you know that an energy transformation took place?

the base and place the lid securely on top. ◗ Light the Bunsen burner and heat the saucepan in a blue

flame, making sure the flame is spread evenly over the base of the saucepan.

InvEstIgatIon 9.3 Energy and chemical reactions Chemical reactions often involve energy changes. Chemical reactions that get hot because they generate heat are called exothermic reactions. Chemical reactions that cause the reactants to drop in temperature absorb heat from the environment and are called endothermic reactions.

Temperature probe Test-tube rack

Data logger

You will need: dilute (0.1M) hydrochloric acid solution test tubes test-tube rack data logger and temperature probe (or glass thermometer accurate to 0.2 C) 1 cm long strip of magnesium metal ammonium chloride teaspoon Reaction 1

Dilute hydrochloric acid Magnesium metal ◗ Quickly remove the temperature probe and add half a

teaspoon of ammonium chloride. ◗ Replace the temperature probe in the test tube and

record your observations. Swirl the contents of the test tube and record the minimum temperature reached.

◗ Pour approximately 2 mL of dilute hydrochloric acid

solution into a test tube in a test-tube rack. ◗ Place the temperature probe or thermometer into the

solution and record the initial temperature once it reaches a steady value.

◗ Record all your observations and measurements in a

single suitable table.

◗ Put the strip of magnesium metal into the acid solution

and record your observations. Swirl the contents of the test tube and record the maximum temperature reached. Reaction 2

DiScuSSion 1

Which reaction was exothermic and which was endothermic? How do you know?

2

Identify the energy transformation that took place in the exothermic reaction.

3

Explain why the temperature drops in an endothermic reaction.

◗ Pour 2 mL of tap water into a clean test tube. ◗ Place the temperature probe into the solution and record

the initial temperature once it reaches a steady value.

9 Energy 233

in traditional light globes, electricity passes through a thin filament in the globe, causing it to glow white hot. The light is a useful form of energy but the heat is a wasted form of energy. compact fluorescent lights (cFL) offer a more energy-efficient form of lighting as they generate less wasted heat.

Compact fluorescent lights transform a greater proportion of electrical energy to light and less to wasted heat.

10

light

30

heat

70

light

Electrical energy

REMEMBER 1 Recall four types of energy. 2 identify the type of energy: (a) a person has when running (b) a spring has when it is pulled. 3 Use a suitable example to describe what is meant by an: (a) energy transfer (b) energy transformation. 4 outline the Law of Conservation of Energy. 5 identify the different types of energy involved in a trampoline jump.

THinK 6 Imagine riding your bike along a flat gravel road. If you brake suddenly, the bike eventually stops. It no longer has kinetic energy. However, the energy is not lost. Describe what happens to the kinetic energy. 7 A saucepan of water is heated to boiling on an electric hotplate. List three examples of the ways that energy is transformed or transferred.

cALcuLATE 8 calculate the gravitational potential energy of a 2 kg cat sitting on a tree branch 15 metres from the ground.

Core science | stage 4 Complete course

heat

Electrical energy

activities

234

90

9 calculate the kinetic energy of a 60 kg sprinter running 8 m/s. 10 A child sitting at the top of a playground slide has 2000 joules of gravitational potential energy. She flies off the end of the slide with 1200 joules of kinetic energy. (a) calculate the amount of energy transformed to forms of energy other than kinetic energy. (b) Suggest what these other energy forms might be.

cREATE 11 Construct a poster to outline the different energy forms that are involved in the operation of a hair dryer. Add labels to your poster showing where the different forms of energy are used or produced. eBook plus

12 Use the Coaster interactivity in your eBookPLUS to identify the positions on a roller-coaster ride where the car has more kinetic energy and where it has more gravitational energy. int-0226

work sheets

9.1 Types of energy 9.2 Gravitational potential energy 9.3 Converting gravitational potential energy to kinetic energy 9.4 Endothermic and exothermic reactions

9.2

Heat and temperature Heat is a form of energy and, like other forms of energy, it can be measured in joules (J). Heat and temperature are not quite the same thing. The temperature of a substance is a measure of how hot or cold it is. It is usually measured in degrees Celsius ( C) using a thermometer. In many cases, substances with more heat energy have a higher temperature, but this may not always be the case. For example, on a cold day, a gas heater may provide a bedroom with 1000 J of energy and increase the room s temperature to 26 C. The same gas heater may provide a large living room with 1000 J of energy but increase the room s temperature to only 23 C. Both areas have the same amount of heat energy, but the bedroom has a higher temperature.

During cold weather, snakes lie against rocks that have absorbed some heat from the sun. The fastmoving particles in the rocks transfer some of their energy to the snake, warming it up.

Why temperature changes Heat energy flows from a hotter object to a colder one. When an object receives heat energy, its particles move faster and its temperature rises. When an object gives up heat energy to another object, its particles move more slowly and its temperature drops.

The temperature of an object or substance depends on how fast the particles inside it are moving. The faster the particles move, the higher the temperature.

Heat continues to flow from hotter objects to colder objects until their temperatures are equal. The movement of heat then stops. Heat never flows from colder to hotter objects. For example, if a cup of hot chocolate is left sitting on a bench, it cools down. The fast-moving particles in the hot chocolate give up some of their energy to the air near the cup. The hot chocolate keeps cooling until it reaches room temperature. If chilled juice is left sitting on a bench, it warms up. The particles

in the juice gain some energy from the warmer air near the glass. If left out of the fridge, the juice warms up until it reaches room temperature.

Thermometers When an object absorbs heat, its particles move faster. The faster the particles move, the more space they take up. As the particles take up more and more space, the object expands. A thermometer works because the substance inside it takes up more space when it is heated. The substance used in most modern thermometers is alcohol, dyed red to make it easier to see. Most glass thermometers measure temperatures to ±1 C but digital thermometers are more accurate and can often measure temperatures to ±0.1 C. Digital thermometers are commonly used by doctors to check whether a patient has a high temperature. You might use a digital thermometer in your experiments if you need to measure small temperature changes with great accuracy.

A digital thermometer used by a doctor

9 Energy 235

 é#

Column A very fine column rises from the bulb, up the thermometer. When the bulb is heated, the alcohol inside heats up too. As the alcohol expands, it has only one place to go up the column! The amount that the alcohol expands depends on its temperature. Higher temperatures make the alcohol expand further up the column.

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 é#

 é#

 é#

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Scale The scale is designed so that the height of the alcohol in the column indicates the temperature. This thermometer would be useful for measuring temperatures between 0 and 100 C. It is measuring a temperature of 23 C.

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Bulb The dyed alcohol is stored in the bulb of a thermometer.

Heat transfer by conduction The metals used to make pots and pans are very good conductors of heat. This helps to ensure that the

InvEstIgatIon 9.4 Modelling a thermometer You will need: heatproof mat, Bunsen burner and matches gauze mat and tripod flask stopper with hole in it glass tube retort stand bosshead and clamp food colouring water-based marker ◗ Set up the equipment as shown in the diagram. ◗ Use the retort stand and clamp to keep the flask and

glass tube steady. ◗ Use a water-based marker to mark the level of coloured

water in the glass tube. ◗ Light the Bunsen burner. ◗ Observe what happens to the level of coloured water

heat from the flame or hotplate is spread evenly. To understand how heat is transferred through an object by conduction, you need to look inside the object. The particles in a solid are packed very closely together. They can vibrate on the spot, but they cannot move from one place to another. If some of the particles are heated, they cannot move along the object to transfer heat to the whole object. Heat travels by conduction when fast-moving particles collide with other particles nearby, making them move faster. Heat can travel by conduction through objects, or from one object to another, such as from a cooktop to a saucepan. Heat travels by conduction at different speeds, depending on the type of substance. Heat travels more quickly in solids than in liquids or gases because conduction occurs more quickly when the particles in an object are closer together. Gases are the poorest conductors because the particles in them are far apart. Solids are usually very good conductors of heat because the particles in them are packed closely together, although not all solids conduct heat well. Metals are generally good conductors while non-metals like glass, plastic and wood do not conduct heat as well. Materials that conduct heat poorly are called insulators.

DiScuSSion 1

Explain how the equipment used in this experiment could be used as a thermometer.

2

Use the particle model to explain what happens to the level of water when the flask is heated and cooled.

Glass tube Stopper Clamp Retort stand Water with added food colour

Flask Gauze mat Tripod Bunsen burner

in the glass tube while it is being heated. Record your observations. ◗ Turn the Bunsen burner off before the water boils. ◗ Observe what happens as the water cools. Record your

observations.

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Heatproof mat

When particles are heated (for example, with a flame), they start to move more quickly. When the fastmoving particles collide with other particles, they cause nearby particles to start vibrating more quickly as well. Bunsen burner flame

Conduction in solids, liquids and gases The particles in a solid are packed closely together. If some particles receive heat energy and begin to move faster, they collide easily with other particles nearby and pass the heat energy along.

Direction of heat transfer

High temperature

The particles in liquids are further apart than the particles in solids. When some particles receive heat energy and start to move faster, they collide with other particles. But the distance between the particles means that there are fewer collisions. So, heat is transferred by conduction more slowly in a liquid than in a solid.

Low temperature

Eventually, as particles keep colliding with others, some of their energy is transferred along the object. This process is known as conduction.

The particles in a gas are far apart. Heat does not travel easily by conduction through gases.

◗ Set up the equipment using either

InvEstIgatIon 9.5

the tripod and rods (as shown below left) or the conduction apparatus (as shown below right).

comparing rates of conduction You will need: heatproof mat Bunsen burner matches tripod variety of rods (such as copper, iron, brass, glass) or a conduction apparatus wax candle ruler stopwatch

◗ Light the candle and melt a blob

of wax onto each rod at the same distance from the end of each. ◗ Light the Bunsen burner, turn it

to the blue flame and start the stopwatch as you begin to heat the end of each rod. ◗ Draw up a suitable table to record

Two ways to do this experiment

the time it takes each blob of wax to melt and produce drops of wax. Stop heating after 5 minutes.

◗ Draw an appropriate graph to

present your findings.

DiScuSSion 1

What evidence is there to suggest that heat travelled along the rods?

2

Through which rod did heat travel the fastest?

3

Which rod is the poorest conductor of heat? What evidence do you have for this conclusion?

4

Why was it important to put the blobs of wax the same distance from the Bunsen burner? Blob of wax

Blobs of wax Various rods Bunsen burner

Tripod

Heatproof mat

Bunsen burner

Conduction apparatus

Heatproof mat

9 Energy 237

Heat transfer by convection Have you ever noticed that, in summer, the air in a two-storey house is warmer upstairs than downstairs? You may have heard the saying that hot air rises. On the previous page, you learned that heat travels by conduction fastest in solids because the particles are more closely packed together. Transfer of heat by conduction in liquids and gases is not very efficient; instead, heat travels through liquids and gases by convection. Convection heaters work on this mode of heat transfer. The heater causes the particles of air in front of it to gain energy and spread apart. This warmer air is less dense, so it rises, losing some of the heat energy it gained. This causes the air to cool and become denser as the particles move closer together again. The cooler air then falls. This flow of warm air up and cool air down creates a circular current called a convection current. The same pattern can be seen in liquids.

InvEstIgatIon 9.6 Modelling convection currents You will need: 250 mL beaker heatproof mat, Bunsen burner and matches tripod and gauze mat potassium permanganate crystal drinking straw forceps ◗ Fill the beaker with water. Place it over the Bunsen

burner as shown below. ◗ Carefully drop a crystal of potassium permanganate

down the straw. ◗ Slowly remove the straw, making sure not to disturb

the water. ◗ Light the Bunsen burner and turn it to a blue flame,

being careful not to disturb the beaker. ◗ Draw a diagram to show what happens to the crystal

as the water is heated. Particles lose heat energy.

Forceps

Crystal of potassium permanganate Cold air sinks.

Warm air rises. Particles gain heat energy.

Drinking straw Beaker Water Gauze mat Tripod Heatproof mat

Heat Modelling a convection current

Bunsen burner

DiScuSSion

Gas heater Convection currents consist of warm air rising and cool air falling.

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1

Explain why the particles moved the way they did in this experiment.

2

This investigation modelled heat transfer by convection. Outline the benefits of modelling concepts in science.

3

Are convection currents modelled accurately in this investigation? What limitations are there to modelling concepts in science?

Cold water in Cold water enters the hot-water system through a pipe that takes it to the bottom of the tank.

A hot-water tank has a heating element in the base that creates a convection current. This current causes the warm water to circulate in the water tank ready for delivery to the hot-water tap.

Ready to use A pipe connects the water at the top of the water tank with the shower and every other hot-water tap. If this water is not used, it cools and sinks to the bottom, where it is heated again.

Sinking The particles in the cold water move more slowly than the particles in the warmer water. The cold water sinks because its particles are close together. Cold water is more dense than hot water.

Rising Hot water rises because its particles are further apart than those in cold water; it is less dense than cold water. As the hot water rises, cold water continues to move to the bottom of the water tank.

Gas flame A gas hot-water system has a flame at the bottom of the water tank. The flame heats the water near the bottom of the tank. An electric hot-water system has elements inside the water tank, similar to those in a kettle.

Heating The flame heats the cold water at the bottom of the tank. The particles move more quickly and spread out.

Convection currents within a hot-water tank

coastal sea breezes Sea breezes are often created by convection currents along a coastline. As land along the coast warms up during the day, warm air rises. This warm air cools as it rises above the sea. Cool air then moves in to Day

Cool air sinks. Warm air rises.

Warmer land

Cool air replaces warm air.

Cooler sea

replace the warm air over the land causing a circular convection current. At night, the sea temperature is higher than the temperature on land so convection currents move in the opposite direction. Night

Cool air sinks.

Cool air replaces warm air.

Warm air rises.

Cooler land

Warmer sea

Sea breezes caused by convection currents

9 Energy 239

Heat transfer by radiation The sun provides energy to the Earth. Without heat from the sun, the Earth would be far too cold for humans to live on. Heat from the sun must travel through space to reach the Earth. The heat does not travel by conduction or convection because there are too few particles in space to vibrate or move between the sun and the Earth. Heat from the sun reaches the Earth by radiation. Heat that travels by radiation is called radiant heat. Radiant heat travels very quickly because it does not rely on the movement of particles to move energy from one place to another. The heat from the sun takes about eight minutes to reach the Earth, but would never reach us by conduction or convection.

InvEstIgatIon 9.7 Absorbing radiant heat You will need: heater or microscope lamp 3 identical soft-drink cans black and white paint 3 thermometers (or 3 temperature probes and a data logger). ◗ Paint one can white and one black, and leave the

third with an unpainted, shiny surface. ◗ Pour equal amounts of cold tap water into each can. ◗ Place the thermometers in the cans. ◗ Measure the initial temperature of the water in

each can. Record your results in a suitable table. ◗ Place the three cans at the same distance from

the radiator or lamp. Turn on the power to the heat source. ◗ In a suitable table, record the temperature of the

water in each can every 2 minutes for a total of 14 minutes.

DiScuSSion

Place your hand near the base of the globe of a lamp. Turn on the lamp. You feel the heat from the globe almost instantly. Heat does not travel through air easily by conduction so, the heat does not reach your hand by conduction. Rather, the heat reaches your hand by radiation.

Transmission, absorption and reflection Radiant heat behaves in a similar way to light. When radiant heat strikes a surface, it can be reflected, transmitted or absorbed. Most surfaces do all three; some surfaces are better reflectors, others are better absorbers and some transmit more heat. Transmitted heat

Absorbed heat Radiated heat

Reflected heat

240

1

Why was the temperature of the water measured before starting to heat the water?

2

How did the temperature of the water in each can change during the experiment?

3

Which cans were better absorbers and which were better reflectors of radiant heat? How can you tell?

4

Why was it important to use cans that were the same size? Heater

Transmitted radiant heat Clear objects, like glass, allow light and radiant heat to pass through them. The temperature of these objects does not increase quickly when heat reaches them by radiation. Absorbed radiant heat Dark-coloured objects tend to absorb light and radiant heat. Their temperatures increase quickly when heat reaches them by radiation. Reflected radiant heat Shiny or light-coloured surfaces tend to reflect light and radiant heat away. The temperature of these objects does not change quickly when heat reaches them by radiation.

Core science | stage 4 Complete course

Black

White

Shiny

infra-red scanners

insulation

All objects, including the human body, radiate some heat. The human body usually radiates more heat than the environment around it. Infra-red scanners detect the radiant heat coming from the human body. That s why infra-red scanners are useful for finding people lost at sea, in bushland or even buried under a collapsed building.

Slowing down the flow of heat is the key to keeping drinks cool in the summer and warm in the winter. On a hot day, heat flows from the hot environment to a cold drink, until they are both at the same temperature. On a cold day, heat flows from a warm drink to the cooler environment, until their temperatures are equal. Heat does not travel into or out of a thermos flask very easily. For this reason, a thermos flask can be used to keep cold drinks cold and warm drinks warm. A thermos flask has a number of features that slow heat transfer by conduction, convection and radiation.

Stopper The stopper is made from materials that do not allow much heat to move through them by convection or conduction.

An infra-red image

Silver surface The silver surfaces facing the inside of the container reflect radiant heat back into the container. Silver surfaces facing the outside of the container reflect radiant heat away from the container. Protective case

Air gap Air does not allow much heat to travel through it by conduction.

Vacuum Nearly all particles are taken out from between these two layers making up the wall of the flask. Without particles, heat cannot move through the walls by conduction or convection.

Foam pads keep the glass bottle in place and absorb impacts.

A thermos flask

9 Energy 241

insulating your body The temperature of the human body is about 37 C. When the air temperature is much less than this, heat moves from your body to the environment. In very hot weather, heat moves from the environment to your body. Unless your body is touching a very hot or a very cold object, you won t gain or lose heat by conduction very easily. Most of the movement of heat near your body happens by convection and by radiation. Clothes keep you warm in winter by stopping your body heat from escaping. Fabrics made from natural fibres, like wool, are good insulators of heat. This is because natural fibres contain only very small pockets of air. This prevents convection currents forming and carrying heat away. Air can flow easily through thin material, keeping you cool in summer. Loose fitting clothes allow more convection currents to form. The convection currents help heat to escape from your body.

InvEstIgatIon 9.8 Reducing heat loss You will need: 4 identical soft-drink cans range of insulating materials (such as wool, nylon, cotton, foam and newspaper) plasticine data logger with temperature probes or thermometers ◗ Design an experiment to compare

how well various insulating materials retain the heat in a can filled with hot water. ◗ Outline the procedure used in your

experiment. Include a can filled with water and without insulation as a control in your experiment.

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Losing radiant heat All objects give off some radiant heat. The amount depends on the temperature around the object. On a hot day, an object does not transfer as much radiant heat away as in the cold weather.

Absorbing radiant heat When sunlight strikes any object, including the human body, the object absorbs some radiant heat.

Convection Convection currents form when the heat from your body warms the air next to it. The air rises, taking some of your body heat away with it. Convection currents can form only in air that is free to move.

◗ A thermometer can be held in place

in each can with plasticine.

DiScuSSion 1

Identify the variables that you attempted to control in this experiment.

2

Explain whether it was important for each can of water to start off at the same temperature.

3

Which material was the best insulator? Support your conclusion with your data.

4

The insulating material slowed the transfer of heat by two processes. Name these processes and explain how the insulation prevented them.

5

Why was it important to include a control in this experiment?

◗ Tabulate your results; draw a line

graph for each material on a single set of axes.

Thermometer Soft-drink can

Plasticine holding thermometer in place

Insulating material

We do most of our cooking using energy from electricity and gas or wood fires. However, these are generated from non-renewable resources: that is, resources that we use much faster than we can replace them. Scientists have been working to harness renewable energy, such as solar energy, for everyday tasks. The solar cooker project has been particularly important in developing countries that rely on wood fires for cooking. Solar cookers work by transforming light energy from the sun into heat energy. The inside of the concaveshaped cooker is covered in a shiny metal such as aluminium. Light rays from the sun are reflected off the shiny surface and concentrated into a central area called the focus. Food placed at the focus cooks more quickly because the light (and, hence, heat) is more intense at this point.

activities REMEMBER 1 identify which type of object (solid, liquid or gas) allows heat to travel fastest by conduction. 2 outline the effect of heating an object on the speed of the particles inside it. 3 Explain how a thermometer works. 4 identify which is denser, hot or cold water. 5 Explain why water rises when heated by a flame at the bottom of a container. 6 identify which method of heat transfer does not require a medium containing particles. 7 outline three different things that can happen to radiant heat when it reaches a surface. 8 outline two uses of infra-red scanners.

THinK 9 Draw two labelled diagrams of the particles inside a metal to demonstrate how the particles would move before and during being heated with a Bunsen burner.

10 Explain whether heat can travel by conduction through a vacuum (where there are no particles). 11 identify some of the materials commonly used for saucepan handles. Explain why these materials have been used for this purpose. 12 Explain why the smoke from a factory does not keep rising forever. 13 Explain why it is almost impossible for criminals to hide from infra-red scanners. 14 identify two features of a thermos flask that reduce heat loss by: (a) conduction (b) convection. 15 outline two ways that heat moves between your body and the environment. 16 Explain what is wrong with the following statement. A thick coat keeps the cold out.

inTERPRET 17 The table above shows results collected during an experiment similar to the one on page 237.

Material

Time taken for piece of wax to melt (s)

Rock

8.0

Copper

6.5

Brick

11.0

Silver

5.0

Aluminium

7.7

List the items in the table from the best conductor of heat to the poorest conductor of heat.

inVESTiGATE 18 investigate what a convection oven is and how it works. 19 investigate the contribution of James Joule to science. 20 The change in temperature of water inside shiny, black and white containers was investigated on page 240. Design and perform an experiment to investigate the heat-absorbing properties of different colours. Which colours absorb more heat? How can you tell? work sheet

9.5 Conduction and convection

9 Energy 243

9.3

Light and sound energy Light energy In some energy transformations, light energy is produced along with heat. The light and warmth we receive from the sun each day are the result of a nuclear fusion reaction in the sun as hydrogen atoms are fused into larger helium atoms. Like radiant heat, light produced by the sun takes around 8 minutes to reach us here on Earth. That s not a very long time considering it has to travel 150 million kilometres. Light from any object travels very fast, with a speed of 300 million metres per second. Light does not need a material like air to travel through, which explains why sunlight can travel through space. Closer to home, the incandescent light globe glows white hot, generating light and allowing us to go about our evening activities.

The moon and the statue (below) are not luminous We see non-luminous objects because light from luminous objects bounces from them. The bouncing of light from an object is called reflection. You see the moon because it reflects light from the sun and some of that reflected light enters your eyes. You see the statue because it reflects light from the sun or, if it were indoors, the lights in the room. We are able to see things when light coming from them enters our eyes. The light energy is then transformed into electrical energy by special nerve cells called receptors at the back of each eye. That energy is then sent to the brain, which tells us what we are looking at.

Luminous and non-luminous objects Objects like the sun, that produce their own light by transforming some other form of energy, are said to be luminous. An example of a luminous organism is the firefly. When a male firefly wants to attract a mate, it flashes its light on its abdomen and performs a dance. Females watch from near the ground and respond by flashing their lights. Most of the living things that produce their own light live in the ocean. The angler fish lives in the dark depths of the ocean and produces its own light to attract prey.

Non-luminous objects may appear bright when they reflect light.

The firefly s light comes from a chemical reaction in cells of the abdomen (left). Angler fish have light-emitting bacteria in the tips of their antennae (right).

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◗ Put the radiometer in direct

InvEstIgatIon 9.9

sunlight. Record your observations.

observing a radiometer

◗ Put it in the shade. Record your

observations again.

A radiometer consists of four vanes, each of which is black on one side and silver on the other. The vanes are balanced on a vertical support so that they can turn with very little friction. The mechanism is encased inside a glass bulb from which air has been pumped out, making it almost a vacuum.

1

What effect does sunlight have on a radiometer?

2

How does this experiment demonstrate that sunlight is a form of energy?

You will need: radiometer

3

Research a scientific theory to explain the effect of sunlight on the radiometer.

DiScuSSion

InvEstIgatIon 9.10 Luminous and non-luminous sources of light You will need: light globe and 2 wire leads DC power source light-coloured object (such as a white eraser) long cardboard tube ◗ Connect the light globe to the

power source. ◗ Set the power source to 6 or

8 volts and switch it on. ◗ View the light globe and the light-

coloured object in turn through the cardboard tube from about 1 metre away. Describe your observations. ◗ Now bend the cardboard tube

and repeat the previous step. ◗ Straighten the cardboard tube

DiScuSSion

again and view each object with the room darkened.

1

Could you see either object when the cardboard tube was bent? What does this tell you about how light travels?

2

Which of the objects viewed was luminous? Support your response with evidence from this investigation.

3

Which of the objects viewed was non-luminous? Support your response with evidence from this investigation.

◗ Record each of your observations in a table like the

one below. Observations Object Light globe Light-coloured object

Straight tube in a bright room

Bent tube in a bright room

Straight tube in a dark room

9 Energy 245

CAUTION Never pierce a glow stick. Never let the chemical contents touch the skin or eyes.

InvEstIgatIon 9.11 investigating glow sticks Glow sticks produce light through a process similar to that used by fireflies. When the plastic outer tube of a glow stick is bent, a vial inside the tube is broken causing its contents to combine with another chemical surrounding the vial. A chemical reaction then produces light energy. This process is called chemiluminescence.

◗ Place one glow stick in icy water

and the other in hot water. ◗ Observe the reactions in each glow

stick. Look closely at their contents and note any differences between the reactions in the glow sticks.

DiScuSSion

You will need: ice hot water 2 large beakers 2 glow sticks

1

Outline the energy transformation taking place in each glow stick.

2

Describe any differences between the reactions in the two glow sticks.

◗ Place a mixture of ice and cold

3

Explain any differences in the observations made of the two glow sticks.

water in one beaker and hot water in a second beaker.

◗ Snap two glow sticks and invert

each, allowing the contents to mix.

Sound energy In 1883, the Indonesian island of Krakatoa was blown apart by a volcanic explosion. The sound of the explosion was probably the loudest that human ears have ever detected. It was heard as far away as South Australia. That s over 3000 kilometres away! Sound, along with light and heat, is a form of energy. The explosion at Krakatoa released such a huge amount of sound energy that it could be heard so far away.

The vibrations caused by the volcanic explosion on Krakatoa in 1883 had enough energy to travel through the air for at least 3000 km. This photo shows Krakatoa erupting more recently in 1995.

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Sound waves

Direction of sound wave

The sound wave a moment later

Sound is caused by fast, back-and-forth movements called vibrations. When you strike a drum, the drum skin vibrates. The movements of the drum skin cause air particles around the drum to be pulled back and spread out. A fraction of a second later, the air particles are pushed together. This pulling and pushing of air particles continues until the drum skin stops vibrating. Compression The energy of the vibrating drum skin is transferred to the nearby air particles. The air particles vibrate as Rarefaction quickly as the drum skin vibrates. The vibrating air particles bump into nearby air particles, making them vibrate as well. This creates a series of compressions (layers of air particles that are close together) and Air particles rarefactions (layers of air particles that are spread apart) that we call sound waves. If there is enough energy transferred to the vibrating air, the vibrations are passed on all the way to your Vibrating drum ear. If the vibrations reach your ear, you hear sound. When a mobile phone rings in a bell jar, the sound can be heard clearly. When the air in the bell jar is sucked out by a vacuum pump, the sound fades. If all of the air is removed, no sound can be heard Sound waves consist of a series of compressions and rarefactions. at all. This is because sound cannot travel through empty space. The energy of vibrating objects can travel only by making particles vibrate. In empty space, there are no particles to vibrate. Bell jar Bell jar Light on the other hand does not require a medium to travel through. It can travel through a vacuum. So Mobile phone you can still see the mobile phone, even if you can t hear it. Sponge

Laser pointer

To vacuum pump

Sound waves require a medium to travel through; light does not.

InvEstIgatIon 9.12

To vacuum pump

Modelling sound waves using a slinky spring

Modelling sound waves You will need: slinky spring ◗ Pull the slinky spring from both

ends to stretch it a couple of metres along the floor. ◗ Create vibrations at one end of the

slinky by moving the coils in and out. ◗ Watch the series of compressions and rarefactions

travel to the opposite end and reflect back.

DiScuSSion 1

Describe how your model is similar to real sound waves.

2

Describe how your model is different from real sound waves.

9 Energy 247

How fast does sound travel? You might remember that light travels at 300 million metres per second. Sound does not travel as fast. The speed of sound through air is about 340 m/s. Sound travels faster in denser materials; for example, sound travels through water at 1500 m/s and through rock at about 6000 m/s. When lightning strikes during a thunderstorm, a giant electric spark heats the air around it. The hot air expands quickly, crashing into the cold air around it. The sound of that crash is thunder. So why do you always hear thunder after you see the lightning? The answer lies in one of the differences between sound energy and light energy. Sound travels through air at about 340 m/s. Light travels through air at 300 000 km/s. The delay between when you see lightning and when you hear thunder is about three seconds for each kilometre that you are away from the lightning.

Sounding great Just as light can be transmitted, reflected and absorbed, so can sound. All materials transmit some sound, some better than others. That s why you can sometimes hear conversations from another room through the walls. Sound is reflected by hard surfaces, such as the tiles in bathrooms and showers. Each note that you sing in the shower lasts longer because its sound is reflected. This effect is called reverberation. Soft materials, like curtains and carpet, absorb much more sound than walls covered with tiles or plaster. The concert hall in the Sydney Opera House was designed to control the reflection and absorption of sound and provide good sound quality during musical performances. Timber panelling was incorporated in the ceilings and walls as it was considered to have good acoustic properties, minimising the reflection of sound, called echoes, from the walls and preventing reverberations from repeated echoes during concerts. Concert hall of the Sydney Opera House

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Measuring sound While we can hear sound waves, they are invisible. However, they can be studied by converting the sound energy into electrical energy using a device called a cathode ray oscilloscope (CRO). A microphone connected to the CRO measures the air pressure changes associated with the compressions and rarefactions of a sound wave and produces a graph on the CRO screen called a waveform. This allows us to record how quickly the sound wave makes the air vibrate and compare the energy levels of sound waves. The pitch of a sound depends on how quickly it makes the air vibrate. High-pitched sounds make the air vibrate quickly. As a result, they produce bunched-up waveforms. Low-pitched sounds This peak represents air that has been compressed (squashed up). It is at a higher pressure than normal.

make the air vibrate less quickly, so the waveforms are more spread out. The number of times every second that a sound makes the air vibrate is called its frequency. Frequency is measured in a unit called hertz (Hz). High-frequency sounds are more high pitched than low-frequency sounds. Loud sounds produce a tall waveform on a CRO display. This is because more sound energy produces a larger electrical signal. Soft sounds, on the other hand, produce a shorter waveform. The decibel (dB) scale is commonly used to measure the sound level or loudness of sound. On the decibel scale, the quietest audible sound is 0 dB. Each 10-fold increase in sound level is an extra 10 dB higher. So a sound 1000 times more powerful than This trough represents air that is spread out. It is at a lower pressure than normal.

the quietest audible sound is 30 dB. Some common sounds and their decibel ratings are shown at right. Any sound above 85 dB can cause hearing loss, and the loss is related both to the loudness of the sound as well as the length of exposure. You know that you are listening to an 85 dB sound if you have to raise your voice to be heard by somebody else.

The calls of the blue whale, with sound levels of more than 180 dB, can be even louder than the launch of a space shuttle. Scientists working in the Southern ocean recorded blue whale calls at this sound level and could, therefore, locate blue whales up to 200 km away.

The decibel scale Decibels (dB) 160 150 140 Jumbo jet on take off 130

CRO

120 Threshhold of pain Tuning fork 110 Car horn

Taller waveforms represent louder sounds. That s because louder sounds change the air pressure more than soft sounds do.

100 90

Lawn mower

80 70 60

Normal conversation

50 CRO

40 Tuning fork

This waveform is more bunchedup than the waveform in the top diagram. It represents a sound with a higher frequency.

This tuning fork vibrates faster than the one above. It makes a higher pitched sound.

30 20

Whisper

10 0

Quietest audible sound

9 Energy 249

The ear and hearing The main job of the ear is to detect sound. It collects the energy of vibrating air and changes it into electrical signals, which are sent to the brain. Each ear has three main parts the outer ear, the middle ear and the inner ear.

Middle ear The middle ear contains the three smallest bones in the body. Together, they are known as the ossicles. These tiny bones send vibrations from the eardrum to the inner ear. They also make the vibrations larger. One of the ossicles (the stirrup) presses against a thin layer of skin called the oval window at the entrance to the inner ear.

The aye-aye is a rare animal that ascar. lives on the island of Madagascar. gle it feeds at night and has goggle eyes and huge ears. The aye-aye searches for food by tapping one of its stick-like fingers on tree trunks. it listens to the sound as vibrations go through the wood. The sound tells it where gaps, cracks and hollows are under the bark and where tasty grubs are hiding. Then it chews through the wood and hooks out the grub with its long middle finger.

Semicircular canals These three tubes have nothing to do with hearing. They control your sense of balance. When you move, fluid in the tubes flows past cells that sense the movement. These cells send signals to the brain. The signals tell you when you are moving and whether you are up, down or on your side. When you move around in circles quickly, the fluid moves quickly even for a while after you stop. The messages from the cells in the semicircular canals tell your brain that you are still moving. However, the messages from your eyes tell the brain that you are not moving. These mixed messages to the brain make you feel dizzy.

Auricle The outside part of the ear contains a spongy type of tissue called cartilage.

Outer ear The outer ear collects the energy of the vibrating air and funnels it along the ear canal. The air along the ear canal vibrates. That makes the eardrum vibrate. High-pitched sounds make the eardrum vibrate quickly. Low-pitched sounds make the eardrum vibrate slowly.

Ear canal The ear canal contains wax and tiny hairs to trap dust so that it doesn t get to the eardrum. If the wax builds up enough to block your ear canal, a doctor can remove it.

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Inner ear The inner ear is filled with fluid. The vibrations are passed along the fluid into a snail-shaped tube called the cochlea. The inside of the cochlea is lined with millions of tiny hairs. Each hair is attached to a nerve receptor. When the fluid vibrates, the hairs move. The receptors change the energy of the moving hairs into electrical energy and send signals through the auditory nerve to the brain. You interpret those signals as sound.

PVC/cardboard tube

InvEstIgatIon 9.13

Stretched balloon

Target practice You will need: Candle PVC or cardboard tubes of various lengths and diameters balloon scissors rubber band ruler candle and holder matches ◗ Select a tube. Measure and record

its length and diameter. ◗ Cut the neck from the balloon. Open

the balloon and stretch it over the end of the tube and secure it firmly to the tube using the rubber band. ◗ Light the candle and place it on a

bench. ◗ Starting just in front of the candle,

try to blow out the candle by

Rubber band

pinching and then pulling and releasing the stretched rubber sheet at the end of the balloon. If you were successful move back away from the candle and try again. Record the maximum distance from which you can blow out the candle. ◗ Collate the class s results, including

the lengths and diameters of the tubes.

DiScuSSion 1

Explain why you were able to blow out the candle.

2

Identify an independent variable in this experiment.

3

Identify the dependent variable in this experiment.

4

Analyse the class s results to determine the most effective dimensions for your device.

◗ You could design a separate

experiment to determine the tube diameter and length that are most effective at blowing out the candle.

Auditory nerve Nerves from the receptors in the cochlea merge to form this large nerve that sends signals to the brain.

Eustachian tube This tube joins the middle ear to the nose and throat. It is usually closed. When the air pressure on the eardrum is not the same on both sides, the tube opens. Air then moves either into or out of the middle ear until the pressure is balanced again. When the air pressure on one side of the eardrum changes quickly, you can feel a pop as the Eustachian tube opens and air rushes through it. This happens when you are in a plane that is climbing steeply. The air pressure in the plane becomes less than the air pressure in your middle ear. The Eustachian tube then opens and some air moves from the middle ear to the nose and throat so that the air pressure on your eardrum is balanced.

9 Energy 251

InvEstIgatIon 9.14 Sound proofing You will need: variety of materials to test (such as wood, fabric, glass and cardboard) source of sound (such as an mp3 player) sound level meter or data logger and sound probe ◗ Design an experiment to

investigate the most effective material to insulate against noise. ◗ Record your results in a

suitable table and graph. ◗ Analyse your results to draw an

appropriate conclusion.

activities REMEMBER 1 outline how light energy is produced in the sun. 2 identify the type of energy that a firefly uses to produce light. 3 outline how sound is created. 4 Draw and label a sound wave to demonstrate rarefactions and compressions. 5 Explain why sound cannot travel through empty space. 6 outline the function of the outer ear. 7 Describe how the ear enables us to hear sounds.

108 million km from the sun to Venus. 10 compare the movement of air particles in a compression with those in a rarefaction. 11 identify the three things that can happen to sound energy when it reaches a solid object like a wall. 12 If you see lightning and then hear thunder 9 seconds later, calculate how far you are from the lightning strike. 13 Explain why there are three semicircular canals in the ear rather than just one. 14 The speed of sound through various materials is listed below. Speed of sound (m/s)

THinK

Material

8 identify each of the following objects as luminous or nonluminous. (a) Sun (b) Moon (c) Human eye (d) Venus (e) Burning candle

Brick

3650

Sea water

1531

Iron

5950

9 Light energy travels through empty space and air at a speed of 300 000 km/s. calculate how long light takes to travel the

252

• The African elephant’s ears enable it to hear low-pitched sounds from other elephants over four kilometres away. They also use their giant ears to release heat, sometimes flapping them to cool down more quickly. • Some insects have ears but they are not on their heads. The ears are membranes like eardrums on the surface of their bodies. A cricket has an ear just below the knee of each of its front legs. A grasshopper has an ear on each side of its body just below the wing. Most insects, however, do not have ears but detect vibrations with sensitive hairs on their antennae or other parts of their bodies.

Core science | stage 4 Complete course

Air (at room temperature)

343

Glass

5100

Distilled water

1497

(a) identify the trend in the data. (b) Explain why there is such a trend.

inVESTiGATE 15 investigate how glow sticks produce light energy. 16 You can feel your vocal cords vibrate if you place your hand gently over your throat while you talk. Say a long hummmm in a deep voice and feel the vibrations. Describe how the vibrations change when you say hummmm in: (a) a louder voice (b) a higher voice. 17 Is it true that older people find it more difficult to hear high-pitched sounds? Using secondary sources, investigate the normal frequency range of human hearing and whether that range depends on age. eBook plus

18 Use the Virtual oscilloscope weblink in your eBookPLUS to simulate measuring sound energy. 19 Use the My ear weblink in your eBookPLUS to watch an animation of the effect of sound waves on cochlear structures. work sheets

9.6 Light energy 9.7 Sound energy

9.4

PREScRiBED FocuS AREA Applications and uses of science

sound technology Hearing requires the ear to detect sound energy. Unfortunately, not all of us have perfectly functioning ears. The bionic ear is helping some people with hearing problems, and Australian scientists are at the forefront of its development.

The bionic ear The cochlear implant, also known as the bionic ear, has allowed some people with inner-ear problems to hear sound for the first time. When deafness results from serious inner-ear damage, no sounds are heard at all. Normal hearing aids, which make sound louder, do not help in these cases because the cochlea cannot detect the vibrations. However, the cochlear implant can often help by changing sound energy from outside the ear into electrical signals that can be sent to the brain.

Imaging by Dr Jin Xu

An enlarged x-ray of the cochlea showing the experimental electrode array inside

3. The electrical code is sent through a cable to the transmitting coil. Radio waves are then used to send the code through the skin.

1. A microphone is worn behind the ear. 2. The speech processor changes the sound into an electrical code. It can be worn on a belt, or a smaller version can be built into the microphone and worn behind the ear.

4. The receiver stimulator is implanted in a bone behind the ear. It decodes the signal and sends electric pulses through wires towards the cochlea.

5. Electrodes placed inside the cochlea receive the decoded signals. The 22 electrodes allow a range of different pitches to be detected. The electrodes stimulate the hearing receptors.

6. The hearing receptors send messages through the auditory nerve to the brain. The sound heard by the user is not completely natural because there are only 22 electrodes replacing the tens of thousands of hair cells in the cochlea of a normal ear.

How a cochlear implant works

9 Energy 253

ultrasound While the human ear can detect sound frequencies between 20 and 20 000 Hz, frequencies well beyond the range of human hearing are used in a variety of useful technologies. Sound with frequencies higher than those that humans can hear is called ultrasound. This image of an unborn baby was produced with ultrasound. To produce images like the one above, ultrasound is sent through the mother s body. Some of it is reflected from the baby. A computer is used to change the reflected ultrasound into an image. The images are used to check for problems during pregnancy. Ultrasound is also used to check for cracks in metal, drill holes in glass and steel, and how well metals are joined together.

catching prey in the dark Bats use ultrasound to find their prey in the dark. The ultrasound they emit from their nostrils is reflected from insects. Bats can tell from the reflected ultrasound, or echo, exactly where their prey is. The further away the insects are, the longer it takes the echo to return to the bat. The echo from more distant insects is also fainter. This use of echolocation by bats is called biosonar.

Sonar Ultrasound is used in sonar to produce images of underwater objects or the ocean floor. The use of reflected sound to locate objects is called echolocation. 1 Ultrasound is sent down into the water. 2 Objects under the water (and the ocean floor) reflect some of the ultrasound.

activities REMEMBER

3 A receiver detects the reflected ultrasound.

1 outline the difference between sound that we hear and ultrasound.

A computer uses the time taken for the reflected ultrasound to return to the ship to calculate the depth of objects in the water. It can also map the ocean floor.

2 identify two medical uses of ultrasound. 3 Describe how ultrasound enables bats to locate insects.

Transmitter/receiver

3

4 identify what the electrodes in the cochlear implant replace.

1 Reflected ultrasound (echo)

Transmitted ultrasound

THinK 5 Explain why the use of sound to locate objects is called echolocation. 6 identify which sense the use of biosonar replaces in bats.

2

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7 Explain why hearing aids do not help people with a seriously damaged cochlea.

LooKIng BaCK 1 Identify the type of energy possessed by a: (a) bus on its way to school (b) wind-up toy (c) gas heater.

13 (a) Recall which variable is a measure of the number of times an object vibrates every second. (b) Describe how a sound changes when this variable increases in value.

2 Describe the Law of Conservation of Energy.

14 Give an example of an object that heat (and light) is: (a) reflected from (b) absorbed into (c) transmitted through.

3 Identify the energy transformations that occur as: (a) a skier skis down a slope (b) a firecracker is ignited (c) a bungee jumper reaches the bottom of a jump. 4 Calculate the energy of: (a) a 65 kg bungee jumper about to jump from a height of 60 metres (b) an 800 kg car travelling 15 m/s. 5 In 10 minutes, an incandescent light globe is supplied with 1000 joules of electrical energy. During that time, the globe emits 400 joules of light energy along with 600 joules of heat energy. Calculate the efficiency of the globe in terms of light output. 6 Compare the particles in a beaker containing water at 67 C with particles in another beaker containing water at 11 C. 7 Outline the difference between heat and temperature. 8 Heat can move in three ways: conduction, convection and radiation. Deduce which method is most likely to transfer heat: (a) from the sun to the planets (b) from a person s feet to cold floor tiles (c) through the air (d) through water (e) from an open fire to your body (f) through a solid metal rod. 9 Identify the features of a thermos flask that control the movement of heat by conduction, convection and radiation, and explain how these features limit the transfer of heat by each of these methods. 10 A spatula of ammonium chloride crystals are added to 5 mL of water in a test tube. Explain why the water temperature drops from 22 C to 15 C within 3 minutes. 11 Explain why convection heaters are so effective in heating a room of a house. 12 The waveform below was produced by plucking a string on an electric guitar. Copy the waveform. In another circle of the same size, draw a waveform that: (a) shows a louder sound (b) has a higher pitch.

15 Copy and complete the table below, indicating with a tick which statements refer to light and which refer to sound. Some of the statements apply to both light and sound. Statement

Light

Sound

Travels through empty space at 300 000 km/s Can be reflected Always caused by vibrating objects or substances Can travel through transparent substances Cannot travel through opaque objects Can be measured in decibels Can be produced from another form of energy Is detected by receptors in the human body Travels faster than a speeding bicycle 16 (a) Explain why sound waves cannot travel through empty space. (b) Explain why light waves can travel through empty space. 17 Draw a flow chart to outline the process of hearing by the human ear. 18 Construct a table to indicate whether the following objects are luminous or non-luminous. Some of the objects listed can be either luminous or non-luminous. For example, a torch is luminous if it is switched on and non-luminous if it is not switched on. So, for a torch, a tick would be entered in both the luminous column and the non-luminous column. sun moon Mars light globe candle flame cat s eye diamond TV screen 19 Identify which forms of energy (heat, light or sound) can easily travel through: (a) glass (b) shiny aluminium (c) air (d) empty space.

9 Energy 255

20 The information in the table below indicates how home appliances transform electrical energy into light or sound energy.

Appliance

Transform electrical energy into light energy

Transform electrical energy into sound energy ✔

Hair dryer Television

✔

Desk lamp

✔ ✔

Home computer

✔

Light globe

✔

✔

rm

l energy into lig

ht

sfor Tran

m electric

al e n

erg y o int nd sou

Tra ns fo

The same information can be represented in a Venn diagram as shown below. ca ctri ele

Desk lamp Light globe

Television Home Computer

Hair dryer Vacuum cleaner Airconditioner

4 A conversation is measured by a data logger to have a loudness of 60 dB. An ambulance siren passes by and is recorded at 90 dB. How much louder is the siren than the conversation? A 1000 times B 300 times C 100 times D 30 times (1 mark) 5 Describe some of the technologies involving sound that have been developed by scientists. Explain how these technologies have benefited society. (6 marks) work sheets

The overlapping section of the Venn diagram contains the appliances that transform electrical energy into both light and sound energy.

Convert the information in the table completed in question 15 into a labelled Venn diagram.

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(1 mark)

3 The energy transformations that occur when an electric kettle boils water are A electrical energy to heat energy and kinetic energy. B potential energy to heat energy. C electrical energy to kinetic energy. D potential energy to heat energy and kinetic energy. (1 mark)

✔

Airconditioner

1 Energy is defined as A the ability to do work. B the temperature of an object. C the sum of the kinetic energy and potential energy of an object. D the amount of heat an object possesses. (1 mark) 2 A feature of sound waves is that they A travel at about 340 m/s through air. B do not require a medium to travel through. C consist of troughs and crests. D travel faster through less dense objects like liquids than through solids.

✔

Vacuum cleaner

TEST YouRSELF

9.8 Energy puzzles 9.9 Energy summary

stUDY CHECKLIst Energy transformations

eBook plus

■ define the term energy 9.1 ■ identify different forms of energy and situations or ■ ■ ■ ■

ICt

phenomena in which different forms of energy are evident 9.1 use models to describe different forms of energy 9.1 9.3 identify objects that possess kinetic energy because of their motion and quantify the kinetic energy 9.1 identify objects that possess gravitational potential energy and quantify the gravitational potential energy 9.1 apply the law of conservation of energy to account for the total energy involved in energy transfers and transformations 9.1

sUMMaRY

eLessons Energy in disguise Did you know that all energy is constantly being transformed and transferred from one object to another? This eLesson helps you to discover that there s more going on in your world than meets the eye as you learn about the different types of energy and the laws that govern it. A worksheet is attached to further your understanding.

Heat and temperature ■ compare the terms heat and temperature 9.2 ■ describe the transfer of heat by conduction, convection and radiation

9.2

■ analyse situations in which heat is transferred by one or more of the following: conduction, convection and radiation 9.2 ■ investigate the ability of materials to prevent the transfer of heat 9.2 ■ outline the use of infra-red scanners 9.2

Searchlight ID: eles-0063

interactivities Light and sound energy ■ describe light as a form of energy not requiring a medium for propagation

9.3

■ contrast luminous and non-luminous objects 9.3 ■ describe sound as a form of energy requiring a medium for propagation 9.3 ■ investigate and compare the pitch and frequency of sounds 9.3 ■ describe the function of the human ear in hearing 9.3 ■ identify structures in the human ear involved in hearing and outline the process of hearing 9.3

Coaster This interactivity helps you apply your knowledge of energy to an amusement ride. Identify the positions in a roller-coaster ride where the car would have more kinetic energy and where it would have more gravitational energy. Instant feedback is provided.

Applications and uses of science ■ explain how the bionic ear can assist the hearing impaired

9.4

■ outline some applications of ultrasound technology 9.4

Searchlight ID: int-0226

9 Energy 257

10

Body systems part 1

As you sit reading this book, many complex processes are taking place inside your body. Your cells are burning up glucose to release energy. Oxygen and nutrients are being delivered to every part of your body and waste products are being removed from your cells. Your blood is transporting substances throughout your body and the specialised organs that make up your body systems are working together to keep you alive.

In this chapter, students will: 10.1 ◗ describe respiration and explain how it

keeps organisms alive 10.2 ◗ distinguish between unicellular and

multicellular organisms and explain why multicellular organisms require specialised organs and systems ◗ identify body systems and organs and learn how substances move in and out of cells 10.3 ◗ investigate the structure of the

respiratory system and the function of its organs 10.4 ◗ outline the causes of asthma 10.5 ◗ explore the links between smoking and

cancer 10.6 ◗ describe the role, structure and

function of organs of the circulatory system ◗ describe the components of blood and outline their function 10.7 ◗ learn about the heart and blood

pressure 10.8 ◗ describe some technological advances

in medicine.

Your blood transports oxygen, nutrients and waste products around your body and helps protect it from disease.

Know your type In this chapter you will learn about blood and the important substances it carries around the body. How much do you already know about blood? Do you know your own blood type, for example, and why your blood type is important? The ABO grouping system divides blood into four groups: A, B, AB and O. Also, a person s blood can be either positive (+) or negative ( ) based on whether their blood contains a particular factor, called the Rhesus factor. The following table shows the percentage of the population with each blood type. O+ O– A+ A– B+ B– AB+ AB–

Blood type

Percentage 40 9 31 7 of pop. (%)

8

2

2

1

If you need a blood transfusion, it is very important to know your blood type and that of the donor because some blood types cannot be mixed. If the wrong types are mixed, the blood cells may clump together and cause fatal blockages O

Donor’s blood A B AB

Patient’s blood

O A B AB Blood types are compatible these blood types can be mixed. Blood types are not compatible these blood types clump together if mixed.

in blood vessels. The table below shows which blood types can be mixed and which cannot.

Know your body 1. Identify which blood type is the most common. Which is the least common? 2. Identify which blood group(s), A, B, AB or O, can be accepted by (a) all blood groups, (b) blood group AB and (c) blood group A. 3. Identify which blood group, A, B, AB or O, can receive transfusions from all blood types. 4. Find out what happens if an Rh-negative mother has an Rh-positive child. Does this affect her future children? 5. Find out what happens when people donate their blood at a blood bank. How often can you donate blood, how long does it take and how much blood do they take? Summarise your findings in a brochure, storyboard, PowerPoint presentation or cartoon. 6. (a) Some people have religious grounds for disagreeing with the use of blood transfusions. Imagine a fouryear-old child with a lifethreatening condition. Her parents will not allow her to have the blood transfusion that she needs. What should the doctors do? Discuss this with your team and report your decision to the class. If there are any differences of opinion, organise a class debate on the issue.

(b) Would your response be different if the child was 18 years old and wanted the blood transfusion but her parents would not allow it? 7. A day after donating blood, a person finds that they have an infectious disease that can be transmitted by blood. What should they do? Discuss this with your team, giving reasons for your opinions. 8. Working in small groups, each group lays out a long piece of butcher s paper on the classroom floor. One student lies down on the paper, face up, with their arms slightly away from their body. Another student from the group uses a marker pen or pencil to trace around the outline of the student lying on the paper. (a) Combining your group s knowledge, draw the following organs where you think they belong in the body outline and show what you think is their shape and approximate size: lungs, heart, intestines, kidneys, ovaries, stomach, liver, pancreas, bladder, brain. (b) Use reference books to check how close you were to the actual location and shape of the organs. Did you draw any organs in completely the wrong place? Were you about right in the sizes you estimated for the organs? work sheet

10.1 Blood types

10.1

Energy for living All living things need energy. This energy is generated by a process called respiration. Respiration is a chemical reaction in which glucose reacts with oxygen to form carbon dioxide and water. Energy is also released. This can be written as a word equation: glucose + oxygen carbon dioxide + water + energy or as a symbol or formula equation: C6H12O6 + 6O2

6CO2 + 6H2O + energy

Respiration occurs inside cells in organelles called mitochondria. Mitochondria are found in both plant and animal cells. Cells that have a high energy requirement contain more mitochondria than cells that require less energy. The muscle cells in your legs, for example, have lots of mitochondria. Mitochondrion Cell membrane

Cytoplasm Nucleus Respiration occurs in the mitochondria of cells.

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Where does the glucose come from? • In animals, the glucose comes from the food the animal eats. The digestive system breaks down the food into small molecules including glucose. The glucose travels through the bloodstream to our cells and can pass through the cell membrane into the cytoplasm. • In plants, the glucose is produced by photosynthesis. Photosynthesis is the process where plants use sunlight to change carbon dioxide and water into glucose and oxygen. The glucose is made in the leaves and travels to all parts of plants in special tubes called phloem tubes. Where does the oxygen come from? Oxygen comes from the air for land organisms and from the water for aquatic organisms. In humans, oxygen enters our bodies via our lungs. It then diffuses through the walls of the alveoli in our lungs, into our bloodstream, and it is taken to all the cells of the body. Some aquatic animals take in oxygen through their gills, others through their skin. Plants produce oxygen when they photosynthesise. If they need to take in additional oxygen, it enters the plant through small holes in the leaves and stem. Respiration also produces the waste products carbon dioxide and water. Our lungs excrete (get rid of) the carbon dioxide. We use some of the water produced by respiration for various processes in the body, but some of it may also be excreted via the skin (as sweat) or via the kidneys (as urine).

Diabetes mellitus is a group of diseases that affect the way your body uses blood sugar (glucose). Usually glucose is able to enter your cells because of the action of insulin. Insulin is made in the pancreas. If you have diabetes, glucose cannot get into your cells. It stays in your blood. It then shows up in your urine. This happens either because your body does not make enough insulin, or your cells do not allow glucose to enter. Too much glucose in your blood can damage almost every major organ in your body. This then leads to death. There are different forms of diabetes. Type 1 diabetes usually starts in childhood and type 2 diabetes usually starts later in life. By eating correctly, having a healthy weight and getting lots of exercise, you have less chance of getting adult-onset diabetes. If you have diabetes, diet and exercise are important. Also, watching your glucose level and using medicine to control blood sugar can help you have a healthy life.

A little history How do we know about respiration and the need for oxygen to survive? It s all thanks to the work of some very clever scientists from the past. Some of their work is discussed on this page.

Robert Boyle (1627 91) showed that something in air was needed to keep animals alive as well as to keep a candle burning. He carried out experiments in which he put various items inside jars inverted over water to ensure that no air could enter the jar. When he placed a burning candle inside a sealed jar, the candle went out. When he placed a small animal inside the sealed jar, the animal became unconscious. If he put air back into the jar, the animal sometimes revived.

Lit candle

Candle goes out.

Mouse with green plant survives.

Small animal alive

After some time, small animal becomes unconscious.

Robert Boyle showed that something in air was needed to keep a candle burning and an animal alive.

Priestley s experiment

Burning candle floating on cork

After a short while, candle goes out.

Add green plant.

Later the candle can burn again.

Joseph Priestley (1733 1804) took Boyle s experiment one step further. Like Boyle, he put a candle in a jar inverted over some water and the candle went out. He then introduced a living plant inside the same jar without letting any air in. After a few days, he was able to relight the candle and found it could burn for a short time. This showed that the living plant could produce the substance that was needed for the candle to burn (oxygen). Priestley also set up an experiment with an animal inside a sealed jar with a plant. In another sealed jar he placed the same animal but no plant. Only the animal living in the jar that contained the plant survived. The plant must have produced something that the animal needed to survive (oxygen again!).

Mouse alone dies.

Joseph Priestley showed that plants produce the substance needed to keep a flame burning and an animal alive.

Lid

Hole to allow oxygen in Insulating layer

Antoine Lavoisier (1743 94) also contributed to our understanding of respiration. He showed that respiration was a process that produces heat, just like burning (combustion). He placed a guinea pig in a calorimeter, a device designed to measure the amount of heat released when a substance burns. A picture of the calorimeter used by Lavoisier is shown on the right. Lavoisier measured the amount of ice that melted in order to calculate the amount of heat released by the guinea pig as it respired.

Guinea pig placed here Ice placed here

Water drips out here Lavoisier used this calorimeter (shown here cut away to reveal the inside) to show that respiration releases heat energy. He placed the guinea pig inside the basket and surrounded it with ice, which melted and ran out of the funnel.

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Activities

INVESTIGATION 10.1 Candle in the jar You will need: birthday candle Blu-Tack heatproof mat glass jars or glasses of different sizes (such as jam or instant coffee jars) stopwatch measuring cylinder graph paper ◗ Using the Blu-Tack, attach

the birthday candle to the heatproof mat. ◗ Light the candle. ◗ Invert one of the glass jars over

the candle and time how long it takes for the candle to go out. ◗ Repeat this, using jars of

different sizes. ◗ Measure the volume of each

jar by filling the jar with water and emptying the water into a measuring cylinder.

DISCUSSION 1

Draw up a table like the one below to record your results.

Jar number

262

Time taken for candle(s) to go out

REMEMBER 1 Write down the word equation for photosynthesis. 2 Identify the part of the cell where respiration occurs. 3 (a) Recall the substances needed for respiration. (b) Outline how humans take these in. 4 (a) Recall the waste products formed by respiration. (b) Outline how humans get rid of these substances. 5 Identify which of the following statements are correct. Rewrite any incorrect statements to make them correct. (a) All living things respire. (b) Plants respire at night and photosynthesise during the day. (c) Respiration releases energy. (d) Photosynthesis releases energy. (e) The waste products from respiration are glucose and carbon dioxide. (f) Photosynthesis produces carbon dioxide gas. (g) When a candle burns, it uses up oxygen gas. (h) Animals that live in water do not need oxygen to survive.

THINK Jar volume (mL)

2

Plot a line graph showing jar volume on the horizontal axis and the time taken for the candle to go out on the vertical axis.

3

Is there a relationship between the size of the jar and the time taken for the candle to go out? Explain your answer.

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6 Study the diagram on page 261 showing Priestley s experiment. (a) Explain why there was water at the bottom of the jar and in the container that the jar was sitting in. (b) If Priestley had tried to relight the candle as soon as he had put the plant in the jar, would it have stayed alight? Explain your answer. (c) If the plant was dead, would the experiment have worked? Explain your answer. (d) Would Priestley s experiment have produced the same results if it had been carried out inside a dark room? Explain your answer. (e) In the part of the diagram with the mice, which of the

two jars (left or right) is the control? 7 Study the picture of Antoine Lavoisier s calorimeter on page 261. (a) How did Lavoisier ensure that oxygen could enter the chamber where the guinea pig was placed? (b) Explain why it was necessary to have very good insulation between the layer of ice and the outside of the container. (c) Extension. Ice melts at 0 C. It takes 4.2 joules of energy to heat 1 mL of water by 1 C. The ice started out at a temperature of 4 C. After the guinea pig had been left in the calorimeter for 30 minutes, 50 mL of water was collected. Calculate the amount of heat released by the guinea pig.

INVESTIGATE 8 Lavoisier, Boyle and Priestley used animals in their experiments. What procedure must scientists follow today if they want to use animals in experiments? Justify why such procedures are necessary. 9 The type of respiration described on page 260 is aerobic respiration. Anaerobic respiration is another type of respiration. Use resource materials or the internet to find the answers to the following questions. (a) Outline the difference between aerobic and anaerobic respiration. (b) Write a word equation for: (i) the type of anaerobic respiration that occurs in your muscles when you sprint (ii) fermentation (another type of anaerobic respiration). (c) What is lactic acid? Outline why it is important to athletes. (d) What type of organisms carry out fermentation? Identify some foods and drinks made using fermentation as part of the manufacturing process? work sheet

10.2 Cellular respiration

10.2

All systems go In chapter 5, pages 127 8, you learned that there are unicellular and multicellular organisms. Unicellular organisms are made up of one cell only. That one cell must do all the jobs needed to keep the organism alive. Unicellular organisms are very small so the substances they need, such as oxygen and glucose, can simply diffuse into the cell from its surroundings. Waste products can diffuse out of the cell and into the surroundings. Carbon dioxide out Oxygen in

Other waste products out

Glucose and other useful substances in

Oxygen and other useful substances diffuse into cells and waste products diffuse out of cells.

Multicellular organisms are made up of many cells. Some multicellular organisms, such as flatworms and sea lettuce, are so thin that most of their cells are in direct contact with their surroundings. Oxygen can

diffuse from the water in which they live directly into their cells. Carbon dioxide can diffuse out of their cells into the water. For larger animals with many layers of cells, things are not so simple. Many of their cells are not in direct contact with their surroundings. In humans, for example, most cells are deep underneath our skin. How do oxygen and nutrients reach these cells? How do these cells remove their waste products and where does the waste go? Most multicellular organisms are very complex and contain a number of systems that work together to keep the organism alive. For example: • the respiratory system takes in oxygen and gets rid of carbon dioxide • the digestive system breaks down food into particles that are small enough to pass through the walls of the intestines and into the bloodstream • the circulatory system carries these nutrients, as well as oxygen, to all cells in the body. It also carries waste away from cells and takes it to organs that can excrete (get rid of) this waste. Systems consist of organs. For example, the organs that make up the digestive system include the stomach, oesophagus, pancreas, intestines and liver. Organs are made up, in turn, of different types of tissues. Your heart is an organ and it contains cardiac muscle tissue, blood, connective tissue and adipose tissue (fat). Tissues are made up of cells, and cells, in turn, are made up of molecules, which consist of atoms joined together.

A flatworm (above) and sea lettuce (right) are examples of multicellular organisms that are so thin they do not require complex organs and systems to keep them alive.

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All matter in the universe is made up of atoms.

A group of atoms is called a molecule.

An organelle is made up of thousands of molecules.

Cells are the basic building blocks of all living things. They contain different types of organelles.

The central nervous system consists of the brain and the spinal cord.

Connecting nerves (peripheral nervous system)

Groups of cells that do a specialised job are called tissues. The smooth muscle in your body is a tissue.

Organs like the human brain are made up of different kinds of tissue. The building blocks of life

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Several organs working together make up a system, such as the central nervous system and peripheral nervous system.

Ovaries

Liver Reproductive Excretory

Kidney

Testes Trachea M uscles Muscles System

Musculoskeletal

Lungs

Respiratory

Skeleton System Brain

Blood vessels

Blood

Central nervous

(circulatory)

Spinal cord

Heart Gall bladder

Eyes Ears

Digestive

Sensory

Stomach

Nose Liver Can you suggest examples for the empty boxes in this mind map?

INVESTIGATION 10.2

◗ You might have heard of people

having a burst lung . That seems to suggest that lungs are hollow, like balloons. Slice through one of the lungs to find out if it really is hollow.

Exploring organs You will need: sheep’s pluck (heart and lungs) with part of the liver and trachea attached newspaper and tray to place the pluck on plastic disposable gloves balloon pump on vacuum cleaner ◗ Carefully observe the sheep s heart,

◗ Cut through the heart and liver to

find out if they are hollow.

DISCUSSION 1

Copy and complete the table below in your workbook.

2

Which major blood vessels can be seen?

5

Where does the air go when the lungs blow up?

3

What happens to the lungs when air is blown in?

6

Why does the heart need to be hollow?

4

Explain why there are rings of cartilage around the trachea.

7

Use reference books to find out the function of the liver.

lungs, liver and trachea. ◗ Push a piece of rubber tubing into

the trachea until it reaches one of the lungs. Using a balloon pump or a vacuum cleaner in reverse mode, blow some air into the trachea. CAUTION For hygiene reasons, it is not recommended that you use your mouth to blow air into the tube inserted in the trachea. ◗ Cut off a small piece of lung, liver

and heart. Place each in a beaker full of water. Which one floats? Why?

Phew . . . Garlic breath! Have you ever heard someone say this? Garlic or onion breath comes from further down than your mouth! It has travelled through a number of your body systems. After you have eaten food containing either of these, and it has been digested, it is absorbed through the walls of your intestines and then into your blood. When the smelly onion or garlic blood reaches your lungs through your circulatory system, you breathe out the smelly gas.

Organ

Shape (sketch)

Approx. size

Colour

System to which this organ belongs

Liver Lung Heart Trachea

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Investigate which of these systems are found in: (a) an earthworm

Activities REMEMBER 1 Outline how unicellular organisms take in oxygen and nutrients. 2 Copy and complete the following statements. (a) A molecule is made up of together.

are the small parts inside cells.

(b) (c)

joined

are made up of groups of cells that carry out a specialised job. are made up of different types of

(d) tissues.

(e) Organs work together to make up a (f) The to keep it alive.

.

(b) an ant

in an organism work together

THINK 3 Classify each of the following as a type of cell (C), tissue (T), organ (O) or system (S). Eye Smooth muscle Cardiac muscle Heart White blood cell Liver

Skin Skin cells Brain Neuron (nerve cell) Circulatory system Intestine (c) a jellyfish.

4 Identify which body system has the function of: (a) detecting stimuli (b) supporting and moving the body (c) taking in oxygen and getting rid of carbon dioxide (d) conducting messages from one part of the body to another.

INVESTIGATE 5 The following systems are found in the human body. Digestive Musculoskeletal Endocrine Nervous Circulatory Respiratory Reproductive Immune

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work sheet

10.3 Organ systems

10.3

Breathe in, breathe out Breathe in deeply . . . Now breathe out. You have just introduced some extra oxygen into your body and removed some unwanted carbon dioxide. You do this about 15 20 times per minute without thinking. The muscle movements required for breathing are automatic and controlled by the respiratory centre in the brain. When you breathe in, you take in the mixture of gases called air. Oxygen and carbon dioxide are gases found in the air around you. Oxygen makes up about 21 per cent of the air, while carbon dioxide makes up only about 0.04 per cent. Your body uses some of the oxygen you take in. The table at right shows that the air that you breathe out contains less oxygen and more carbon dioxide

than the air you breathe in. The percentages in the table are approximate and vary a little with weather conditions and height above sea level. The air that you breathe enters your body through your nose and mouth. Unless your nose is clogged up by a cold, it is the most important airway. The hairs and sticky mucus in your nose trap dust and dirt and other harmful material such as diseasecausing bacteria. Breathing in through your mouth gets the air in faster but without being filtered

The water vapour that you breathe out carries heat away from your body and helps you to control your body temperature. You lose about 500 mL of water each day by breathing out water vapour.

by the nose. When you play sport, your body uses oxygen more quickly and it is often necessary to breathe in through your mouth, bypassing the filter system in your nose.

What goes in and what comes out Gas

Oxygen (%)

Carbon dioxide (%)

Air breathed in

21

0.04

Air breathed out

16

4

(a)

Water vapour (%)

Nitrogen (%)

usually <1%

78

2

78

(b)

Epiglottis

Oesophagus (food pipe)

Trachea Capillaries Bronchi

Alveoli

Lungs

Bronchioles

(a) Organs of the respiratory system with (b) a portion of the lung expanded to show details

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Going down?

Direction of blood flow

After entering your body, the air moves into a narrow tube called the trachea, which is more commonly known as the windpipe. At the top of this tube is a flap of tissue called the epiglottis. The job of this tissue is to stop food from going down into your lungs. If food does manage to pass it and go down the wrong way , a cough soon brings it back up again. The trachea divides into two narrower tubes called the bronchi. Each of these tubes leads to a lung. Inside the lung, each tube divides into many smaller tubes called bronchioles. The bronchioles branch out, getting smaller and smaller until they end at thousands of tiny air sacs called alveoli.

Air moves in and out

Oxygen Alveolus (air sac) Carbon dioxide

What happens in an alveolus? An alveolus is full of air. There are many small blood vessels called capillaries that run over the surface of the alveoli. The walls of the alveoli and the walls of the capillaries are very thin. Oxygen passes through these walls from the alveolus into the blood. Carbon dioxide goes in the opposite direction. This is an example of diffusion. When a substance diffuses across a membrane, it moves in the direction that will even out the concentration on both sides of the membrane. In the lungs, the concentration of oxygen is higher inside the alveoli than in the blood so oxygen diffuses out of the alveoli and into the blood inside the capillaries.

(a) Breathing in

Air

Trachea

Direction of blood flow

Capillary

In an alveolus, oxygen diffuses into the blood and carbon dioxide diffuses out of the blood.

The concentration of carbon dioxide is greater in the capillaries than in the alveoli, so carbon dioxide moves out of the bloodstream and into the alveoli so that it can be breathed out. The movement of a muscle called the diaphragm helps the lungs do their job by sucking in and pushing out air. The diagram below shows how this happens.

(b) Breathing out

Air

Trachea

Rib cage

Rib cage

Heart

Heart Lung

Lung

Lung Diaphragm

Diaphragm (a) Breathing in. The diaphragm tightens, allowing the lungs to expand, and the air is sucked in.

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(b) Breathing out. The diaphragm relaxes, making the lungs smaller, and the air is pushed out.

Lung

Air sucked in

Air blown out

Lung capacity

Blu-Tack to ensure good seal

Although adults can breathe out up to 5 litres of air with each breath, they usually breathe out only about half a litre. The largest volume of air that you can breathe in or out at one time is called your vital capacity.

Lid has hole drilled in it. Straw Sticky tape to ensure good seal Balloon inflates (blows up).

Balloon deflates (goes down).

Balloon

Sticky tape or rubber band Cut off top of a balloon to make a rubber sheet .

A model lung. When the rubber sheet at the bottom is pulled down, the pressure inside the jar drops and air is sucked into the balloon. The balloon inflates (blows up).

Balloon allowed to relax

Balloon pulled down

◗ Use the table at the bottom to determine your

INVESTIGATION 10.3

approximate vital capacity in litres.

Measuring your vital capacity

◗ Release the air from the balloon and repeat your

measurement of vital capacity three more times. Average your results to get your best estimate of the maximum blow-out of your lungs.

You will need: balloon ruler ◗ Blow up a balloon to about 20 cm in diameter two or

DISCUSSION

three times to stretch it. Release the air each time. ◗ Take the biggest breath you can, then blow out all the air

1

Why were you asked to stretch the balloon first?

you can into the balloon. Tie up the end of the balloon to hold in your blown out air.

2

Why did you measure your vital capacity four times?

3

(a) Draw up a table with the following headings.

◗ Use a ruler to measure the diameter of the balloon as

shown below. Name

Ruler Approximate diameter measurement Balloon

Male or female?

Does this student play a wind instrument?

Lung capacity (L)

(b) Collect results from all the students in your class and complete the table. (c) Calculate the average lung capacity for all the girls and all the boys. Do girls have a bigger or smaller lung capacity than boys in your class? (d) Calculate the average lung capacity for all the students in your class who play a wind instrument. Compare that with the average value for the other students in the class. Does playing a wind instrument have an effect on lung capacity?

Hold balloon here.

Flat surface (e.g. table)

How to measure the diameter of the balloon 4

Determining vital capacity

Suggest another way of measuring the amount of air exhaled with each breath.

Balloon diameter (cm)

8

9

10

11

12

13

14

15

16

17

18

19

20

21

Approx. vital capacity (litres)

0.3

0.4

0.5

0.7

0.9

1.2

1.4

1.8

2.1

2.6

3.0

3.6

4.2

4.8

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Whales, like all other mammals, have lungs. Unlike fish, they need to swim to the surface every so often to take in a huge breath of air. Large whales blow out then suck in about 2000 litres of air through one or two nostrils on the top of their head. They need only about two seconds at the surface to do this. The air blown out contains a lot of water vapour and forms a cloud or spout that can shoot up to eight metres into the air.

Activities REMEMBER 1 List all of the parts that a molecule of oxygen must go through when travelling from the air into your bloodstream. 2 Describe the job done by each of the following parts of the respiratory system. (a) epiglottis (b) diaphragm (c) alveoli (d) lungs

THINK 3 The terms breathing and respiration are often confused with each other. Differentiate between these two terms. 4 When you breathe out onto a window on a cloudy day it fogs up. (a) Identify the substance that makes the window fog up. (b) Is the same substance breathed out on warm days? If so, why doesn t the window fog up? 5 Some people describe the structure of the lungs as an upside-down, hollowed-out tree. Identify which parts of the lungs the following parts might represent. (a) Trunk (b) Branches

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(c) Twigs (d) Leaves 6 Study the diagram of the model lung on page 269 and answer these questions. (a) Identify the organs or body parts that the following parts of the model represent. (i) Straw (ii) Rubber sheet (iii) Balloon inside bottle (iv) Plastic bottle (b) Copy and complete the following paragraph. When you pull down on the rubber sheet, the space inside the bottle becomes . There is still the same number of air particles in that space so the air particles move . further This makes the air pressure inside the bottle and it causes air to be the straw. When the rubber sheet is let inside go, the the bottle returns to its original size and air is of the straw. (c) Explain why alveoli and capillaries need to have very thin walls.

7 A year 8 student wrote in her exam paper: Humans breathe in oxygen and breathe out carbon dioxide . Her teacher wrote: That s not entirely correct. If that were true, then mouth-to-mouth resuscitation could not keep a person alive . (a) Rewrite the statement made by the year 8 student so that it is correct. (b) Justify the teacher s comment. (c) If you breathed in air that had a lower oxygen concentration than your blood, describe what would happen in your alveoli.

INVESTIGATE 8 Find out what a spirometer is. 9 Research then write half a page to explain how high altitudes affect your breathing.

CREATE 10 Construct a model lung as shown in the diagram on page 269. You can use the following items: ◗ two clear 1-litre plastic bottles with tops ◗ four balloons ◗ two plastic drinking straws ◗ rubber bands or very sticky tape ◗ plasticine or Blu-Tack ◗ scissors. work sheet

10.4 Breathing constructing a report

10.4

Short of breath? If you do not suffer from asthma, it is very likely that you know someone who does. Asthma is a very common condition that affects about one in seven Australian adolescents. About one in ten, or 10 per cent, of adults are affected. Young children are the greatest sufferers of asthma, with one in four affected. One alarming fact about asthma is that the number of people who suffer from it has doubled in the last 30 years. The reasons for this increase are not clear but you might have some ideas of your own after reading this information.

What is asthma? Asthma is a narrowing of the air pipes that join the mouth and nose to the lungs. The pipes most affected are the bronchi. They become narrower as: • the muscle wall of the air pipes contracts • the lining of the air pipes swells • too much mucus is produced.

Normal

Muscles contract

Lining swells

Too much mucus produced

Asthma is a narrowing of the air pipes.

The narrow pipes make breathing difficult and can result in wheezing, coughing and a tight feeling in the chest. The coughing is usually worse at night.

What causes asthma? It is not known why some people get asthma and others do not. It seems that it can be inherited, but many people from families without a history of asthma are affected. Asthma is certainly the result of sensitive airways. An asthma attack occurs when those sensitive airways are triggered. If the sufferer has a cold, the airways are already inflamed and are more likely to be triggered.

Triggers Some of the common triggers of an asthma attack are: • vigorous exercise • cold weather • cigarette smoke • dust and dust mites • moulds • pollen • air pollution • some foods and food additives • some animals. Not all asthma sufferers are affected by the same triggers. Some people suffer attacks only as a result of exercise. Others might be affected by any one or more of the triggers. It is important that those who get asthma try to find out what triggers the attacks. Many of the triggers can be avoided.

Controlling the triggers The best way to control asthma is to avoid the triggers. Of course,

it is not always possible to identify the triggers. People who are affected by cold weather, pollen or air pollution may even move to other places to avoid their triggers. Pollen from some grasses and trees is very light and becomes airborne on even slightly windy days. The inhaling of pollen can be reduced by avoiding outdoor activities and keeping windows and doors closed on breezy spring days. Moulds live in warm, humid conditions and thrive in bathrooms, kitchens and bedrooms. Their spores are easily breathed in, triggering attacks in some asthma sufferers. Moulds can be reduced by airing the house regularly. Pollen and moulds are also the main triggers of hay fever. Hay fever clogs up the nose in much the same way as asthma affects the air pipes. It causes sneezing and a runny nose. Those asthma sufferers whose attacks are triggered by air pollution are warned to remain indoors as much as possible and avoid vigorous activity on smoggy days. If tobacco smoke is a trigger, the cigarette smoke of others needs to be avoided. Dust mites are a common trigger of asthma attacks. Dust mites are microscopic animals that live in their thousands in warm, moist and dark places like doonas, sheets, pillows, carpets and curtains (see photograph on the next page). Dust mite droppings float in the air and are easily inhaled.

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The hygiene theory Dust mites thrive best in bedding and carpets because these contain plenty of dead human skin cells. Humans shed a complete layer of dead skin cells every month. That amounts to about 1 kilogram of skin cells each year. In fact, most of the dust in your house consists of dead skin cells.

A house dust mite

There has been a dramatic increase in the number of children diagnosed with asthma over recent years. One theory that some scientists have proposed to explain this is the ‘hygiene theory’. According to this theory, diseases such as asthma, eczema, hay fever and some other allergies might be increasing because children are being brought up in an environment that is too clean. If children are not exposed to enough germs as children, their immune system (the system that fights off germs that invade the body) does not develop properly. The result is that sometimes the immune system will mistake harmless substances (such as pollen) for nasty germs and go into full attack mode when exposed to these. these The result is an asthma attack or an allergic reaction. The following data have been used to support this theory. • Children who grow up on farms (where there are a lot more germs) are less likely to get asthma than children who grow up in cities. The more children are exposed to the faeces (poo) of animals, the less likely they are to get asthma. children who live in a house where there is a pet (a source of • Young Y germs) are less likely to develop asthma. • Children who go to day care or have older brothers and sisters are less likely to get asthma than children who are not exposed to the germs of other children. At A present, the ‘hygiene theory’ is just that — a theory. That means scientists are not sure whether it is correct or not. Further scientific studies may either support or disagree with this theory. For now, many doctors are advising parents that allowing toddlers to play in the dirt may be doing their health some good.

Activities REMEMBER 1 Describe what happens to the air pipes to the lungs during an asthma attack to make breathing difficult. 2 Explain why an asthma attack is more likely to be triggered in a person with a cold. 3 Define the term ‘asthma trigger’.

(b) Write down two hypotheses suggesting why there has been a sharp increase in the incidence of asthma. (c) Outline how each of your hypotheses could be tested. 6 Explain why it is unlikely that you would ever rid a house completely of dust mites. 7 (a) In a group, brainstorm ideas about the common triggers of asthma and how they can be controlled. (b) Summarise your discussion in a table similar to the one below.

THINK AND DISCUSS 4 If you were part of an audience of 1400 students in a concert hall for a music excursion, calculate how many of them would be likely to be asthma sufferers. (Hint: Use the information on the previous page.) 5 The number of people who suffer from asthma has doubled in the last 30 years. The hygiene theory is just one possible explanation for this. (a) Outline some other possible reasons why the number of people suffering from asthma has increased so dramatically.

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Trigger Moulds

How the trigger can be controlled Air the house regularly.

INVESTIGATE 8 What is the difference between a hypothesis, a theory and a law? Give an example of each. 9 Find out the two major types of asthma medication. Outline how they differ from each other.

10.5

Up in smoke About 18 000 Australians die each year as a result of diseases caused by smoking. In fact, smoking is the largest preventable cause of death and disease in Australia.

Just one cigarette There are clearly many long-term effects of smoking. However, the diagram below shows what happens to you after smoking just one cigarette. There are some more obvious effects such as bad breath, body odour and watery eyes. After several cigarettes, your teeth and fingers become stained. Your sense of taste is reduced. Even your stomach is affected as acid levels increase.

Smoking and your lungs Lung cancer is the most well-known disease caused by smoking. Chemicals that cause cancer are called carcinogens. Cigarette tobacco contains a number of carcinogens. The chemicals in cigarettes also clog up the fine hairs in your air tubes with a mixture of mucus and foreign chemicals. (a)

Coughing is the body s way of trying to clear the air tubes. However, not all of the clogging can be cleared by coughing. The dirty mixture remains in the air tubes, causing swelling, making them sensitive and slowing down the passage of air. Eventually the sticky mixture sinks down into the lungs, where it blocks some of the pathways to the alveoli, where freshly breathed air should deliver oxygen to the blood. The diseases caused by this blocking process are called chronic obstructive pulmonary diseases, or COPD. Emphysema is the worst of these diseases and results in the eventual destruction of the alveoli.

Smoking and lung cancer It seems hard to believe but there was a time when people did not know that smoking causes lung cancer. A number of medical studies now show that there is a clear link between smoking and the likelihood of developing lung cancer. The two graphs on the following page show the results of some of these studies. Can you make sense of these graphs?

(b) Acetone (paint stripper)

Pulse increases beats by 20 heart beats per minute. Blood pressure rises.

Muscles and organs get less oxygen.

Cyanide (used in gas chambers) Tar is the mixture of chemicals that sticks to the walls of the air pipes and alveoli.

Skin temperature drops by up to 5 C. Methanol (rocket fuel)

Carbon monoxide is a poisonous gas that lowers the amount of oxygen carried by the blood. It is one of the gases released in car exhaust. Arsenic (termite poison)

Just one cigarette? Cadmium

Physical endurance is reduced.

Butane

Ammonia (floor cleaner) Phenol

Vital lung capacity decreases.

Vinyl chloride Muscle tension increases.

(a) Some of the health effects of smoking a cigarette, and (b) the substances in a single cigarette

Nicotine is a poisonous chemical that causes addiction to cigarette smoking. It is often used in pesticides.

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Graph 2

Graph 1 Graph 1: The risk of dying from lung cancer increases with the number of cigarettes smoked daily.

80 4000 Cigarettes smoked per person per year

70 60 50 40 30 20 10 0

Activities

Cigarette consumption (men)

3000

150

Cancer deaths (men)

100

2000 50 1000

0

10

20

30

40

1900

Cigarettes smoked per day

1920

1940 Year

1960

1980

ANALYSE AND EVALUATE 1 The table below shows how the popularity of smoking has changed over the past 50 years or so. Percentage of adult Australians who smoke Year

1945

1964

1969

1974

1976

1980

1983

1986

1989

1992

1998

2004

Males (%)

72

58

45

41

40

40

37

33

30

28

29

26

Females (%)

26

28

28

29

31

31

30

28

27

24

24

20

(a) Construct a line graph of the data in the table. Use Year on the x-axis and % of adult Australians who smoke on the y-axis. Draw lines for males and females in different colours. (b) Suggest why the percentage of females who smoke has changed little while the percentage of males who smoke has declined greatly. (c) Use dotted lines to predict the trends up to the year 2020. What percentage of males and females do you predict will be smoking in the year 2020? 2 Study graph 1 above. (a) Copy and complete the following statements: (i) People who smoke 10 cigarettes a day are times more likely to develop lung cancer than non-smokers. (ii) People who smoke 30 cigarettes a day are times more likely to develop lung cancer than people who smoke 10 cigarettes a day. (b) If a packet of cigarettes costs $15 and contains 20 cigarettes, calculate how much a person

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smoking 40 cigarettes a day spends on smoking: (i) each day (ii) each week (iii) each year. 3 Study graph 2 above. (a) Describe how the incidence of lung cancer changed between 1900 and 1980. (b) Identify when the number of male smokers peaked. (c) Identify when the number of deaths from lung cancer peaked. (d) Explain why there is a 20-year gap between the two numbers. (e) The graph shows data for male smokers only. Predict when the number of cases of lung cancer in women peaked (use the graph you drew for question 1 to answer this).

because it was their fault that they got sick. (b) Cigarettes should cost more. The extra money made from them could then be given to hospitals to help pay for treating people with smokingrelated diseases. (c) Cigarette companies who make profits from smoking should be made to pay for hospital treatment of patients with diseases caused by smoking. 5 Although smoking is now banned in many places, including public transport vehicles, workplaces and some restaurants, it is still legal. Propose why smoking has not been made illegal when it causes so much damage? eBook plus

THINK 4 Smoking-related diseases cost taxpayers many millions of dollars because hospitals are mostly paid for by governments. Write down your opinion of each of the proposals below. Justify your opinion. (a) The cost of hospital treatment for diseases caused by smoking should be paid by the patient

6 Use the Quit Now weblink in your eBookPLUS to learn about the national tobacco campaign. Create a poster that sends one single important message about smoking. work sheet

10.5 Smoking and diseases

Lung cancer deaths (per 100 000 people)

Relative risk of lung cancer

90

Graph 2: This graph shows that the number of deaths from lung cancer has risen as cigarette consumption has increased but there is a 20-year lag time because lung cancer takes many years to develop.

20-year lag time between smoking and lung cancer

Smoking increases risk of lung cancer

10.6

Blood highways The respiratory system gets oxygen into our lungs. Once the oxygen is in the lungs, it needs some way of getting to all the cells of the body. That is the job of the circulatory system. The circulatory system consists of the heart, the blood vessels and blood.

Many of the substances carried around in the blood are dissolved in the plasma. Nutrients such as glucose and some waste products, including carbon dioxide, are dissolved in the plasma.

Blood by the bucketful An average-sized human has about five litres of blood; that s about a bucketful. It travels around the body in tubes called blood vessels. If these vessels were laid end to end, they would encircle the Earth two and a half times. These tubes enable materials in your body to be transported from one place to another. Some of these blood vessels are called arteries. They have thick, elastic, muscular walls and carry blood under high pressure away from your heart. Some other vessels are called veins. They have thinner walls, and valves that prevent the blood from flowing backwards. Veins carry blood to the heart. The most numerous and smallest blood vessels are called capillaries. Your body contains about 1 000 000 km of capillaries, which penetrate almost every tissue. No cell is very far away from one. Capillaries are very important blood vessels because they carry materials such as oxygen and nutrients to the cells and remove wastes including carbon dioxide.

What s in blood? The liquid part of blood is called plasma. It is a straw-coloured liquid and consists mostly of water.

The reason that blood looks red is that it contains many red blood cells. In a drop of blood there are about 300 million red blood cells. They are red because they contain a chemical called haemoglobin, which is red in colour.

The job of red blood cells is to carry oxygen around the body. When red blood cells reach the lungs and oxygen diffuses into the blood, the oxygen reacts with the haemoglobin in red blood cells to form a chemical called oxyhaemoglobin, which is an even brighter red. So blood that contains a lot of oxygen is actually brighter red than blood that is low in oxygen. Red blood cells are very small so they can fit inside tiny capillaries. They form from cells in the bone marrow and, when mature, they lack a nucleus. This saves space. They also have a concave shape. This means that, for their size, they have a large surface area that allows them to carry lots of oxygen.

Red blood cells have a biconcave shape

(a) Vein

Artery Capillary

(b)

Valve open Valve closed The valve is open when blood flows in the correct direction. (a) A cross-section of an artery, a vein and a capillary. (b) Veins have valves to ensure that blood flows in only one direction.

The valve ensures that blood cannot flow the wrong way.

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There are a lot fewer white blood cells in blood but they are larger than red blood cells and have a nucleus. White blood cells have an irregular shape and are not rigid so they can squeeze into small blood vessels. They are involved with fighting disease. Some white blood cells engulf (gobble up) germs while others produce chemicals called antibodies that attack germs. When you are sick, the number of white blood cells in your blood increases. Platelets are also found in blood. Platelets help blood to clot if a blood vessel is cut. This seals up the cut so that germs cannot get in.

"LOODæINæMAMMALSæCONSISTSæOF

0LASMA

Cells

Platelets (less than 0.01% of blood)

(about 55% of blood) 3ERUM

sææ ææPERæMM3 sææ FUNCTIONæ æ AIDSæINæCLOTTING of blood

&IBRINOGEN

FUNCTION CONTAINS CLOTTINGæOFæBLOOD sæ WATER sæ PROTEINS sæ GASESæ 2EDæBLOODæCELLS 7HITEæBLOODæCELLS æ EGæCARBONæ (about 45% of blood) (less than 0.1% of blood) æ DIOXIDE sæ NUTRIENTS sæ næMILLIONæPERæMM3 sæ æPERæMM3 sæ WASTEæMINERALS sæ NOæNUCLEUS sæ NUCLEUSæPRESENT æ ANDæOTHERæ sæ CYTOPLASMæWITH sæ COLOURLESSæCYTOPLASM æ SUBSTANCES æ HAEMOGLOBIN sæ FUNCTION sæ FUNCTION DEFENCEæAGAINSTæDISEASE æ CARRIESæOXYGENæAND æ CARBONæDIOXIDE The components of blood

Activities REMEMBER Human blood cells seen through a light microscope. The white blood cells are shown as pink, each with a nucleus.

INVESTIGATION 10.4 Viewing blood cells You will need: prepared slide of blood smear microscope ◗ View the prepared slide under

the microscope on high power. ◗ Find a white blood cell on the

slide.

DISCUSSION 1

Sketch a few red blood cells and one white blood cell.

2

Estimate how many red blood cells would fit inside a white blood cell.

3

276

Estimate the number of red blood cells that can fit across the field of view.

Core Science | Stage 4 Complete course

1 Outline what blood is and what it does. 2 Name and describe the types of blood vessels in which blood travels around your body. 3 Compare red blood cells, white blood cells and blood platelets. 4 Explain the advantage of red blood cells not having a nucleus. 5 Explain why haemoglobin is important. 6 Why isn t blood the same colour in all animals?

THINK AND ANALYSE 7 The higher the altitude, the less oxygen there is in the air. Propose a reason why people living at high altitudes usually have more red blood cells than people living at low altitudes. 8 The branching diagram above shows the composition of blood. Construct a divided bar graph that shows what proportion of blood consists of plasma, red blood cells, white blood cells and platelets.

Insect blood looks a little like raw eggwhite, because it contains no pigment. The blood of crabs and crayfish, however, contains the pigment haemocyanin. This pigment has copper in it and is blue when combined with oxygen. This is different from haemoglobin in humans, which is red when combined with oxygen.

9 Copy and complete the following: There are times more red blood cells than white blood cells in blood.

INVESTIGATE 10 Research one of the following circulation topics and summarise your findings to the class in a poster or PowerPoint presentation: blood transfusions, rhesus babies, varicose veins, leukaemia, haemophilia, thrombosis, embolisms, aneurisms. 11 Find out more about how blood circulates in insects and lobsters.

DISCUSS 12 With a partner, construct a PMI (see page 513) for a law that makes it compulsory for everyone over 16 to donate blood at least once a year.

10.7

Have a heart Often linked with emotions, love and courage, the heart has a special meaning for most of us. In a clinical sense, however, it is merely a pump about the size of your clenched fist.

Two pumps in one To be more precise, the human heart is actually two pumps. Veins bring blood back from all parts of the body to the heart. The veins join up into a large vein called the vena cava. This vein leads into the top right chamber of the heart. The blood is then pushed into the Oxygen in Lung

Carbon dioxide out Trachea Aorta (carries blood to the body)

bottom right chamber. From here it is pumped out to your lungs where it picks up oxygen and becomes more reddish in colour. It also loses some of the carbon dioxide from it. The oxygenated blood then returns to the lefthand side of your heart to be pumped out again to your body tissues, where it delivers oxygen and nutrients. The deoxygenated blood then returns to the righthand side of the heart for the cycle to be repeated.

Four chambers The human heart has four

Pulmonary chambers. The upper two arteries (to chambers are called the left lungs)

atrium and right atrium (plural

Pulmonary = atria), and the lower two veins (from chambers are the left ventricle lungs)

and right ventricle. The two sides of the heart are different. The walls of the left side are thicker and more muscular because they Left side need to have the power to force of heart the blood from the heart to the rest of the body. Flap-like structures attached Left to the heart walls, called valves, ventricle prevent the blood from flowing backwards and keep it going in one direction. If you listen to Artery your heart beating you will hear a lub dub sound. The lub sound Blood is due to the valves between the Capillaries ventricles and atria shutting. The Body tissue cells dub sound is due to the closing of the valves that separate the heart from the big blood vessels that lead to the lungs and the rest of the body. Left atrium

Right atrium Right side of heart

Right ventricle Body tissue cell Vena cava Capillary wall

The movement of blood through the heart

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The pulmonary valve is a semilunar valve. It is between your right ventricle and your pulmonary artery. The aortic valve is a semilunar valve. It is located between your left ventricle and your aorta.

Not all animals have four-chambered hearts; in fact, some don t have hearts at all! A fish heart has two chambers, while amphibians and reptiles have three-chambered hearts. Can you suggest any advantages or disadvantages of these hearts over a four-chambered mammalian heart?

INVESTIGATION 10.5 Dissect a heart You will need sheep’s heart preferably with the blood vessels still attached dissecting instruments dissecting board The left atrioventricular (or mitral) valve is a bicuspid valve; it has two cusps. It is located between your left atrium and your left ventricle.

Blood pressure The heart s pumping action and the narrow size of the blood vessels result in a build-up of considerable pressure in the arteries. The force with which blood flows through the arteries is called blood pressure. It is affected by different activities and moods. It also goes up and down as the heart beats, being highest when the heart contracts (systolic pressure) and lowest when the heart relaxes (diastolic pressure). A person s blood pressure is expressed as a fraction. This fraction is the systolic pressure over the diastolic pressure: for example, 120/70.

Keeping the pace Each minute that you are sitting and reading this, about 5 7 litres of blood completes the entire circuit around your body and lungs. In a single day, your heart may have

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The right atrioventricular valve is a tricuspid valve; it has three cusps. It is situated between your right atrium and your right ventricle.

beaten about 100 000 times and pumped about 7000 litres of blood around your body. A normal human heart beats about 60 100 times a minute, this rate increasing during exercise or stress. With each heartbeat, a wave of pressure travels along the main arteries. If you put your finger on your skin just above the artery in your wrist, you can feel this pulse wave as a slight throb. Your pulse rate immediately after exercise can be used as a guide to your physical fitness. The fitter you are, the less elevated your heart rate will be after vigorous exercise. The regular rhythmic beating of the heart is maintained by electrical impulses from the heart s pacemaker, which is located in the wall of the right atrium. Some people with irregular heartbeats are fitted with artificial electronic pacemakers to regulate the heart s actions and correct abnormal patterns.

◗ Identify the parts of the heart

using the illustration on the previous page. ◗ Try to locate where blood

enters and leaves the heart: (a) to and from the lungs (b) to and from the rest of the body. ◗ Sketch and label the heart

and use arrows to show the direction of blood flow. ◗ Cut the heart in two so that

both halves show the two sides of the heart (similar to the illustration on the previous page). ◗ In a diagram, record your

observations of the thickness of the walls on the left side of the heart compared with the right side. ◗ Suggest reasons for the

differences observed. ◗ Try to locate the valves in the

heart.

DISCUSSION 1 Describe the valves and

suggest their function. 2 Write a summary paragraph

about the structure and function of the heart.

Try clenching your fist every second for five minutes. Getting a little tired? The heart is made up of special muscle called cardiac muscle, which never tires. Imagine having a cramp or stitch in your heart after running to catch the bus! Due to its unique electrical properties, heart muscle will continue to beat even if it has been removed from the body. Scientists have shown that even tiny pieces of this muscle cut from the heart will continue to beat when they are placed in a test tube of warm salty solution.

Artery

Oxygen and nutrients

Blood flow

Connected highways Blood travels to all parts of the body in the capillaries. Oxygen and nutrients move out of the blood and pass through the walls of the capillaries. Waste products, including carbon dioxide, are removed from cells and pass through the walls of the capillaries and into the bloodstream. The carbon dioxide is removed in the lungs. Other waste products are filtered out of the blood as it passes through the kidneys.

Wastes

Body cells Blood flow

Vein

In the capillaries, oxygen diffuses out of the blood and waste produced by cells diffuses into the bloodstream.

◗ Measure your heart rate in beats per minute (bpm)

INVESTIGATION 10.6

by counting the number of times your heart beats in 15 seconds and then multiplying this number by 4.

Check your heart You will need: stopwatch blood pressure monitor

Capillary (containing red blood cells)

◗ Measure your blood pressure using the blood pressure

monitor. (a)

◗ Go for a walk in the playground or around the school

oval. Measure your heart rate and blood pressure again.

◗ Find your pulse, either

on the inside of your wrist or in your neck (see the illustrations). Make sure you use two fingers, not your thumb, to find your pulse.

◗ Run up and down a flight of stairs. Measure your heart

rate and blood pressure again. ◗ Copy the table below in your workbook and enter your

own results.

(b) Test

Heart rate (bpm)

Blood pressure (mmHg)

Before exercise After walking After running up stairs

DISCUSSION

Two places where your pulse should be easy to find: (a) radial location (wrist) and (b) carotid location (neck)

1

What effect does exercise have on heart rate and blood pressure?

2

Design and carry out an experiment to test the following hypothesis: ‘There is a link between a person’s resting heart rate and the number of hours the person spends exercising each week’.

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There are also many capillaries associated with the intestines. The digestive system breaks down food into particles that are small enough to diffuse through the walls of the intestines and into the blood. These nutrients are then delivered to all cells by the bloodstream. Blood also passes through the liver. Your liver is like a chemical factory, with more than 500 different functions. Some of these include sorting, storing and changing digested food. It removes fats and oils from the blood and modifies them before they are sent to the body s fat deposits for storage. It also helps get rid of excess protein, which can form toxic compounds dangerous to the body. The liver converts these protein wastes into urea, which travels in the blood to the kidneys for excretion. It also changes other dangerous or poisonous substances so that they are no longer harmful to the body. Your liver is something you cannot do without. As the diagram illustrates, your blood vessels make up a very busy highway system!

Activities REMEMBER 1 Contrast the following: (a) the blood in the two sides of the heart (b) the structure of the two sides of the heart (c) systolic and diastolic pressure. 2 Explain why there are valves in the heart. 3 Define the terms systolic blood pressure and diastolic blood pressure . 4 (a) Recall how many times a normal human heart beats each minute.

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Head, upper limbs Pulmonary artery Aorta

Lung

Lung

Pulmonary vein Left atrium Right atrium Left ventricle

Right ventricle

Intestines Liver

Vena cava

Kidneys, trunk and lower limbs

Connected highways the routes for blood circulation

(b) Outline what might cause the rate of heartbeats to increase. (c) Outline how the rhythmic beating of the heart is maintained. 5 Describe what is unusual about cardiac muscle. 6 Explain why you can t live without your liver.

THINK AND CREATE 7 (a) Copy the connected highways diagram above into your workbook. (b) Use a coloured pencil to show the path taken for a red blood cell to travel from the pulmonary vein to the

pulmonary artery, if it goes via the intestines. 8 Mark the following sites (a, b, c, d) on your diagram. In which blood vessel(s) would you expect the highest: (a) blood pressure (b) blood glucose levels (c) blood carbon dioxide level (d) oxygen level? 9 List the following in the order that a red blood cell would reach them after leaving the aorta. pulmonary artery, left ventricle, right atrium, intestine, lung, pulmonary vein, left atrium, liver, right ventricle

10 Convert your classroom or sports oval into a circulatory highway system . Pretend to be a red blood cell and travel along the route it would take around the body.

12 Interpret the cardiac cycle below to answer the following questions. (a) In which stage do the atria contract? (b) In which stage do both the atria and ventricles relax?

11 (a) Read through the information on pages 277 8 to refresh your memory on the structure and function of your heart. (b) Construct a flow chart to show the movement of blood through your body using the following labels.

13 Systole is the contraction of your heart muscle and diastole is the relaxation of your heart muscle. Propose what the following might mean. (a) Atrial systole (b) Ventricular systole (c) Atrial diastole (d) Ventricular diastole

left atrium, right atrium, right ventricle, left ventricle, pulmonary artery, pulmonary vein, lungs, aorta, vena cava, from body, to body

INVESTIGATE 14 Hypertension or high blood pressure has been called the silent killer . Find out about high blood

pressure and answer the following questions. (a) What do doctors consider to be high blood pressure? (b) Outline how high blood pressure can lead to death. (c) Outline what people with high blood pressure can do to bring their blood pressure back to normal. eBook plus

15 Test your ability to label the parts of the heart by completing the Beat it! interactivity in your eBookPLUS. int-0210 work sheets

10.6 Blood and blood highways 10.7 Removing waste from the blood

2

Atrial systole, ventricular diastole

3

Ventricular systole, atrial diastole

Semilunar valves closed

Atrioventricular valves open

0.1 s

Semilunar valves open

0.3 s 0.4 s

1

Atrial and ventricular diastole

Atrioventricular valves closed

One complete cardiac cycle can take about 0.8 seconds in an adult human with a pulse of about 75 beats per minute.

Source: Fig. 42.6, p. 876 from BIOLOGY, 6th ed. by Neil A. Campbell and Jane B. Reece. Copyright © 2002 by Pearsons Education, Inc. Reprinted by permission.

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10.8

PRESCRIBED FOCUS AREA Applications and uses of science

Transport technology Heart and blood vessel diseases are the major killers in Australia. They claim twice as many lives as cancer and 20 times more than traffic accidents. Modern medicine and technology have produced techniques and procedures that attempt to minimise the effects of diseases and disorders of the circulatory system.

Healthy valve Diseased valve

Artificial valve insertion

Faulty heart and vein valves As we saw on pages 277 8, the heart, like many other pumps, depends on a series of valves to work properly. These valves open and close to receive and discharge blood to and from the chambers of the heart. They also stop the blood from flowing backwards. If any of the four heart valves becomes faulty, the function of the heart may be impaired. It is now possible to replace faulty heart valves with artificial valves like the one shown above. This requires surgery. The patient may also need to take medicine to prevent their blood from forming clots as it flows through the artificial valve.

About 15 per cent of Australians aged between 20 and 65 have hypertension (high blood pressure). This increases their chances of developing heart disease and strokes. To prevent this, people should maintain a healthy body weight, take regular exercise and eat a diet that is low in fat and salt.

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A faulty heart valve may be replaced by an artificial valve. Why are the heart valves so important to the functioning of the heart?

If I only had a heart . . . The tin man from The Wizard of Oz would have been very happy with the development of an artificial heart. This mechanical device can be made of titanium and plastic. Surgeons also An artificial heart implant a small electronic device in the abdominal wall to monitor and control the pumping speed of the heart. An external battery is strapped around the waist and can supply about 4 5 hours of power. An internal rechargeable battery is also implanted inside the wearer s abdomen. This is so they can be disconnected from the main battery for about 30 40 minutes for activities such as showering.

A heart

but no pulse?

If only the left ventricle is damaged, and the rest of the heart is in good working order, a back-up pump may be implanted alongside the heart. One model of these devices results in its wearers having a gentle whirr rather than a pulse. This is the sound of the propeller spun by a magnetic field to force a continuous stream of blood into the aorta.

Atria Ventricles

Contraction Relaxation

R

R T

P Q S

T

P Q S

(a) Normal electrocardiogram

Getting the beat! An electrocardiogram (ECG) shows the electrical activity of a person s heart. ECG patterns are valuable in diagnosing heart disease or abnormalities. To produce the ECG, electrodes (flat pieces of metal that are connected to the ECG machine by wires) are stuck to the skin. The machine measures the tiny electrical impulses produced by the heart as it beats. It produces a trace similar to the one shown in the diagram above. An abnormal trace could indicate that the patient has arrhythmia. This is a condition where the heart beats irregularly. Another reason for an unusual trace could be a cardiac infarction. In this condition there is dead tissue in the heart. The electrical signal cannot travel through the dead tissue so the ECG looks abnormal. There are many other conditions that can cause an unusual ECG, and doctors will often follow up an abnormal ECG with further tests.

Artificial blood a reason to support scientific research If you lose a lot of blood, you may need a blood transfusion. The blood from another person is injected into your veins to replace the blood you have lost.

(b) Abnormal electrocardiogram Electrocardiograms

However, donated blood is always in short supply and the blood that is transfused must match your own blood type. If the person who donated the blood had an infection, there is also a risk of passing on that infection. What s the solution? Artificial blood. No-one has quite succeeded as yet in making a perfect replacement for blood but a number of teams of scientists around the world are working on it. The ideal blood replacement would be a product that has a long shelf life, does not need to be refrigerated, does not need to match the patient s blood type and is guaranteed to be free of disease-causing germs. A type of artificial blood called Hemopure has been approved to treat some cases of severe anaemia in South African hospitals. It is made from haemoglobin obtained either from blood that has passed its use-by date or from animal blood. The haemoglobin is wrapped in certain chemicals so that it behaves a lot like red blood cells do and can carry oxygen around the body. Hemopure is not an ideal replacement for donated blood,

and it has not been approved for human use in Australia. There are side effects to using this product. In some countries, including South Africa, the number of people infected with HIV (human immunodeficiency virus) is much higher than in Australia and donated blood that is free of the virus is in very short supply. In certain instances the benefits of this blood substitute can thus outweigh the risks from the side effects.

Hemopure is a type of artificial blood that has been approved to treat some cases of severe anaemia in South Africa.

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Transplant pioneer If your heart or lungs were not working properly and you had needed a heart or lung transplant in the 1980s, the doctor to see was Victor Chang. Victor Chang was an Australian doctor who was awarded a Companion of the Order of Australia for his contribution to medicine. Dr Chang played an important role in establishing the heart transplant unit at St Vincent s Hospital in Sydney. He set up a team of 40 health professionals who were the finest in their field and developed new procedures and techniques that led to an improved rate of success. Of his patients,

92 per cent were still alive one year after their heart or lung transplant operation and 85 per cent were still alive five years later. The first heart transplant operation that Victor Chang carried out at St Vincent s Hospital was in 1984 on a young girl called Fiona Coote. Fiona is now an adult and, although she has since needed a second heart transplant, she owes her life to Dr Chang. Dr Victor Chang also developed an artificial heart valve, called the St Vincent heart valve, and was working on developing an artificial heart. Unfortunately his life was tragically cut short in 1991 when he was murdered by gunshot.

Activities REMEMBER 1 Recall which group of diseases is the major killer in Australia. 2 Explain why valves are important to the functioning of the heart. 3 Outline why a patient may have surgery to insert an artificial valve. 4 Explain what an electrocardiogram is and when is it useful. 5 Describe how an ECG is used to detect heart abnormalities. 6 Describe how heart valves are similar to the valves in veins. 7 Outline the features that the ideal artificial blood would need.

THINK 8 Outline some situations where hospitals would go through large amounts of donated blood in a short time. 9 Propose why artificial blood might be particularly useful to army doctors working with soldiers fighting wars. 10 Interpret the electrocardiograms on the previous page to answer the following questions. (a) At P , are the muscle cells of the atria contracted or relaxed? (b) After the QRS wave, is the ventricle relaxed or contracted?

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The late Dr Victor Chang, pioneering heart transplant surgeon

(c) How does the normal electrogram differ from the abnormal electrogram? (d) Suggest what might be wrong with the heart activity shown on the abnormal electrogram.

INVESTIGATE 11 Is there a risk of getting HIV from a blood transfusion in Australia today? Investigate what measures exist to ensure that the blood used for transfusions is free of the HIV virus. 12 Describe what artificial hearts are made of and how they work. 13 Describe how blood loss can cause death. 14 Use the internet to research one of the following: strokes, heart murmurs, hole in the heart , atherosclerosis, angina, heart attack, arrhythmias, pericarditis, hypertension. Summarise your findings in a PowerPoint presentation or as a poster. 15 Find out more about organ transplants. Which organs have successfully been transplanted into humans? What determines whether a donor organ is a match for a particular organ recipient? Why do organ recipients need to take medicine for the rest of their lives after having the transplant? eBook plus

16 Use the Electrocardiogram game weblink in your eBookPLUS to simulate performing ECGs on patients referred to you by medical doctors.

LOOKING BACK 1 Write down a word equation for respiration. 2 In one experiment, Joseph Priestley found that a guinea pig left in a sealed jar will die after a short period of time whereas a guinea pig in a sealed jar containing living plants can survive. Explain Priestley’s observations using your knowledge of respiration and photosynthesis.

5 The following diagram shows an alveolus. Match the letters in the diagram with the correct labels from the following list. Alveolus Bronchiole Air flows into the lungs Deoxygenated blood

3 Copy and complete the following table.

Oxygenated blood Main organ in system

Name of tissue Nerve tissue

(c) (b)

and spinal cord

system

and skeleton

Musculoskeletal system

Muscle tissue and

(a)

Name of system

tissue (d)

4 Make a copy of the diagram below for your workbook. (a) Label the lettered parts (A to N) of the human circulatory system and blood vessels on your diagram. (b) Use a red pencil to colour in the blood vessels with oxygenated blood, and a blue pencil for those with deoxygenated blood. (c) State whether the blood in the following blood vessels is deoxygenated or oxygenated: (i) K (ii) J (iii) N (iv) E (v) L. (d) Draw up a table that shows the differences in structure and function of the arteries, veins and capillaries. Head L

N

F E

J

(e)

6 Identify all the body parts that oxygen would need to travel through to get from the air you inhale through your nose to the cells in your big toe. 7 The ‘hygiene theory’ is a hypothesis that has been proposed to explain an increase in the incidence of asthma. Over time, evidence supporting this hypothesis might accumulate. A scientific theory is based on a hypothesis that is supported by a great deal of scientific evidence. (a) What would cause a theory to gain acceptance among scientists and doctors? (b) Can you think of scientific theories that have gained more acceptance over time? 8 List three examples of recent technological advances in the field of medicine.

C

M

K

A Heart B

D Liver G

I J

Hepatic portal vein Rest of body H Elastic fibres and smooth muscle

Elastic fibres and smooth muscle One cell thick

The human circulatory system

9 In this chapter you have seen the importance of your transport system. (a) In a group, create mind or cluster maps (see pages 514–5) that summarise what you know about the following. Blood Blood vessels Heart Lungs Kidneys Liver (b) For each of the six parts of your body listed above, brainstorm in your group as many questions as you can. Then, select one question for each body part to do your own research. Report your findings back to the group.

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10 Use your six thinking hats (see page 517) for three of the following issues or statements. (a) Drinking of any alcohol in Australia should be illegal. (b) Smoking in public should be punishable by a 10-year prison sentence. (c) Only people under the age of 40 should be allowed to have a heart transplant. (d) Smokers should not be allowed to have surgery. (e) Blood transfusions should be illegal. (f) Everyone should have the right to a blood transfusion. (g) Organ donation should be compulsory. (h) Overweight people should not be allowed to have surgery on their circulatory system.

TEST YOURSELF 1 What are the substances required for respiration? A Carbon dioxide and water B Carbon dioxide and oxygen C Oxygen and glucose D Oxygen and water (1 mark) 2 A diagram of the respiratory system is shown below.

1 2

3 4

The parts labelled 1 to 4 are A trachea, alveolus, lung and diaphragm. B bronchus, trachea, lung and diaphragm. C larynx, lung sacs, diaphragm and rib. D trachea, alveolus, intercostal muscles and pulmonary artery. (1 mark)

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3 What is the main function of the circulatory system? A To carry out respiration B To rid of waste C To transport substances around the body D To break down food into small particles (1 mark) 4 A diagram of the circulatory system is shown on the previous page. Which label is pointing to an artery that contains blood that has a much lower oxygen concentration than most arteries? A E B J C N D K (1 mark) 5 Explain why multicellular organisms such as humans need to have specialised organs such as a heart and lungs. (2 marks) 6 Discuss whether it should be compulsory for all Australian adults to donate blood at least once a year. (4 marks) work sheets

10.8 Body systems 1 puzzle 10.9 Body systems 1 summary

STUDY CHECKLIST Cells

eBook plus

■ identify the substances that move in and out of cells

ICT

10.1

■ distinguish between unicellular and multicellular organisms 10.2 ■ describe some of the experiments that early scientists did to find out about respiration 10.1 ■ outline the process of respiration 10.1

SUMMARY

Interactivities Beat it! The heart is one of the most important organs in the human body. This interactivity tests your ability to label the parts of the heart. Instant feedback is provided.

Multicellular organisms ■ explain why multicellular organisms need specialised organs and systems 10.2 ■ identify the materials required by organisms for the processes of respiration and photosynthesis 10.1

Humans ■ describe the roles of the respiratory system and ■ ■ ■ ■ ■ ■ ■ ■ ■

circulatory system in maintaining humans as functioning organisms 10.3 explain how air goes in and out of the lungs 10.3 describe what happens in an alveolus 10.3 outline the changes that occur in the respiratory system of a person who has an asthma attack 10.4 justify why smoking is damaging to your health 10.5 identify and describe the components of blood 10.6 describe the structure of the heart 10.7 explain how the heart works to circulate blood through the body 10.7 define the terms blood pressure , pulse and heart rate 10.7 outline how blood circulation relates to the removal of waste products from the body. 10.7

Searchlight ID: int-0210

Applications and uses of science ■ outline examples of new technologies in medicine that are the result of scientific research and knowledge of the circulatory system 10.8

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11

Bits of matter

There are millions of different substances in the world. Some, like water, occur naturally. Others, like paper and plastic, are made in factories. Some substances, like sugar and blood, are made by living things. All substances have one important thing in common; they are all made of the tiny building blocks of matter that we call atoms.

In this chapter, students will: 11.1 ◗ describe the structure of the atom 11.2 ◗ explain what an element is and learn

the chemical symbols for common elements 11.3 ◗ distinguish between metals, non-

metals and metalloids 11.4 ◗ explain the differences between

elements, compounds and mixtures 11.5 ◗ learn about metal alloys and describe

their advantages over pure metals 11.6 ◗ understand that molecules are made

from bonded atoms 11.7 ◗ appreciate the vital role that carbon

plays in the biosphere 11.8 ◗ describe how the model of atomic

structure has evolved over time in line with new evidence and discoveries

Model of a large molecule in the human body. Red spheres indicate oxygen atoms, yellow indicate phosphorus, blue indicate nitrogen and grey indicate carbon.

What s inside? When you were little, you probably shook and squeezed your birthday presents while they were still wrapped up to work out what was in them before you opened them. 1. What sort of information can you infer about a wrapped present by shaking it or squeezing it? 2. Imagine that you have a brightly wrapped box with something in it. Describe the different guessing techniques that you would use to work out what is in the box without opening it.

InveStIgatIon 11.1 How small are the bits that matter? You will need: a strip of paper cut from an A4 sheet (about 30 cm long) pair of scissors ruler a lot of patience and care a sense of humour ◗ Construct a table like the one below and record the length of the strip of

paper. ◗ Cut the strip of paper in half across the middle. Put one half aside. Measure

the length of the other half. ◗ Cut the measured half in half again. Again, put one half aside and measure

and record the length of the other half. ◗ Before you go any further, predict how many times you will be able to cut

the strip in half. ◗ Continue this process until you can no longer cut the strip in half.

How small are the bits? Number of cuts

Length of strip (approximate)

0

30 cm

1

15 cm

2

7.5 cm (easy?)

3 4 5 6 7 8

1 mm (you re doing well to get this far!)

9 10 12 14 18

1 micron (1 millionth of a metre, one thousandth of a millimetre)

22 26 31

The size of a single atom

11.1

atoms All matter is made up of tiny particles that are called atoms. In fact, atoms are so tiny that 24 million of the smallest atoms would fit side by side in 1 centimetre, and you could fit 120 000 atoms across the average human hair! They are so small that we have only recently developed the technology that allows us to see them. So, if they re so small, how did anyone even know they were there?

In the beginning The idea of the atom started with a thinking exercise that Democritus, a teacher and philosopher living in Greece about 2500 years ago, gave to his students to discuss. Maybe it went something like the story below.

Imagine a twig that has fallen from a tree. Can we break it in half?

Yes!

Is there any limit to how many times we can split the halves into other halves?

We don’t know.

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Democritus named these tiniest particles of matter atomos, which was the Greek word meaning unable to be divided. Of course, very few of the other philosophers of the time agreed with him, and it took another 2400 years before evidence of these atoms (as we now call them) was gathered.

Inside the atom Not all atoms are created equal! Scientists have identified more than 100 different types of atoms. Not all of these atoms are found easily on Earth. Some of them have been observed only under laboratory conditions and have existed for only fractions of a second before breaking up.

Now if I take one of those halves, could I split that also in half?

We suppose so.

And can we split that half again?

Ummm ... yes?

In the end, I think that you would reach a stage where you had something so tiny that it couldn’t be split any further. What do you think students?

You are so clever, Democritus!

The different types of atoms are made up of different combinations of even smaller particles: protons, neutrons and electrons. Using sophisticated equipment, such as scanning transmission electron microscopes, scientists can produce pictures that show the tiny atoms in a material. They have yet to develop the technology to directly observe the particles that the atoms themselves are made of. Structure of an atom — summary Part of atom

Where found

Relative weight

Charge

Proton

Nucleus

Heavy

Positive

Neutron

Nucleus

Heavy

Neutral (no charge)

Electron

Around nucleus

Light

Negative

In the middle of the atom is the nucleus. The nucleus is made up of protons and neutrons held tightly together. The nucleus has a positive charge because it contains protons.

Protons are found in the nucleus. They have a positive charge and are much heavier than electrons.

Scanning tu tunnelling microscope image of atoms in a crystal of silicon

Neutrons are found in the nucleus and have no charge (neutral). They are much heavier than electrons. Electrons move around the nucleus. They have a negative charge. They are much lighter than protons and neutrons.

An atom usually has equal numbers of positive protons and negative electrons. This makes the atom neutral. This atom has six protons and six electrons. The electrons whiz around the nucleus in different levels. The electrons do not fly off the atom because they are attracted to the protons in the nucleus. This is because opposite charges attract (positive protons attract negative electrons).

Protons and neutrons are made up of different combinations of even smaller particles called quarks. Quarks were first named by the American scientist Murray Gell-Mann in 1964. Gell-Mann named th the first three quarks ‘up’, ‘down’ and ‘strange’, with another three, ‘bottom’, ‘bo ‘top’ and ‘charm’, being ide identified later. A proton is made of two ‘up’ quarks and one ‘down’ quark, while a neutron is made of two ‘down’ quarks and one ‘up’ quark. The word quark can be pronounced to rhyme with either ‘mark’ or ‘cork’.

Atoms also have a lot of empty space.

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InveStIgatIon 11.2 Atomic spaces You will need: 1 hula hoop 1 straw rice grains cotton thread table tennis ball sticky tape broom and dustpan ◗ Set up the equipment as shown in

the diagram below.

◗ From across the room, but within

target distance, use the straw as a peashooter to fire rice grains at the table tennis ball. CAUTION Ensure that the rice grains are not fired towards any person. through and how many hit the table tennis ball. (Note: Hits to the cotton thread do not count!)

Construct a bar graph to display your results.

2

Construct a bar graph to show the class results.

3

Which part of the atom does the table tennis ball represent?

4

What does the hula hoop represent?

◗ Use the broom and dustpan to clean

up the mess you ve left on the floor.

REMEMBER 1 Recall the important idea that Democritus had 2000 years ago about the substances that make up the world. 2 Define the word atomos . 3 Describe an atom. 4 Name the three parts of an atom and explain where they would be found. 5 Explain why electrons do not fly off an atom. 6 Recall what makes up most of an atom.

THInK 7 If a neutral atom has 12 protons, calculate how many electrons it has.

Core Science | Stage 4 Complete course

1

◗ Count how many grains go right

activities

292

DIscussIon

8 In ancient Greece, scientists developed their theories by discussion rather than by doing formal experiments to test their ideas. Assess what problems might arise from using only the ancient Greek approach to science.

cREATE 9 construct a model of an atom. It should have at least six protons, six neutrons and six electrons. Use any materials that you like. Perhaps try using a bowl of jelly with lollies in it to represent the parts of the atom! Your model should have a key.

InVEsTIGATE 10 Investigate what nanotechnology is and what connection it has with atoms.

11.2

It s elementary! The alchemists In the Middle Ages, when kings and queens lived in castles and were defended by knights in shining armour, there lived the alchemists. They chanted secret spells while they mixed magic potions in their flasks and melted metals in their furnaces. They tried to change ordinary metals into gold. They also tried to find a potion that would make humans live for ever. They studied the movements of the stars and claimed to be able to see into the future. The kings and queens took the advice of the alchemists very seriously. The alchemists never found the secrets they were looking for, but they did discover many things about substances around us. There were other people of these ancient times whose work has also helped us to understand the substances around us. Blacksmiths worked with metals to make stronger and lighter swords and armour, fabric dyers learned how to colour cloth, and potters decorated their work with glazes from the Earth. Without the knowledge passed down by these people, the world as we know it would be very different! They discovered twelve important substances: gold, iron, silver, sulfur, carbon, lead, mercury, tin, arsenic, bismuth, antimony and copper. Five of these were discovered by the alchemists.

They discovered that the twelve substances could not be broken down into other substances. Scientists investigated many common everyday substances as well, including salt, air, rocks, water and even urine! They discovered that nearly everything around us could be broken down into other substances. They gave the name element to any substance that could not be broken down into other substances. Between 1557 and 1925, another seventy-six elements were discovered. We now know that ninety-two elements exist naturally. In recent years scientists working in laboratories have been able to make another twentyfive artificial elements. In total there are now 117 known elements.

Element basics An element is a substance that contains only one kind of atom. As there are about 117 elements, this means that there are only 117 types of atom that we know of so far. What makes these atoms different from each other is that they are made up of different combinations of protons, neutrons and electrons. It is the specific combination of these smaller particles in the different atoms that gives each element its particular physical and chemical properties. Just as no two people are the same, neither are any two elements. Elements can be distinguished by looking at such things as their: • colour • hardness and brittleness • melting and boiling points • density • state (whether they are solid, liquid or gas at room temperature) • reaction with acids or other chemicals.

Warning! Danger! Real science In about the seventeenth century, people stopped thinking about magic and instead carried out investigations based on careful observations. These new seekers of knowledge were called scientists.

Many elements are safe to handle. However, there are many that are not. For example, the elements sodium, potassium and mercury need special care and handling. Sodium and potassium are soft metals that can be cut with a knife. They both get very hot if they come into contact with water. They are stored under oil so that water in the atmosphere cannot reach them.

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InveStIgatIon 11.3 checking out appearances You will need: samples of chemical elements (such as carbon, sulfur, copper, iron, aluminium and silicon) ◗ Copy the table below into your

workbook. ◗ Carefully examine each of

the elements in the set; look for colour, appearance and hardness. ◗ Complete the table by filling in

the description. One example is completed for you. Element Hydrogen

State Gas

Description Clear, colourless, explosive

chemical symbols In our everyday lives, we tend to Many of the elements have symbols have a standard set of shorthand based on their Latin or Greek names. ways of writing common words. For For this reason, tin (stannum) is sn, example, we write St for street , gold (aurum) is Au, lead (plumbum) is Mr for mister and e.g. instead Pb and mercury (hydrogyrum) is Hg. of for example. In a similar way, scientists use a standard shorthand way of writing the names of the elements. Each element is represented by either a single capital letter or a capital followed by a lowercase letter these are known as the elements chemical symbols. The chemical symbols of some of the more common elements that you may encounter are shown in the table below. Element name Aluminium Carbon Copper Gold Helium Hydrogen Iron

Element symbol Al C Cu Au He H Fe

activities REMEMBER In days gone by, substances containing mercury were used to make hats. In those days it was not known that mercury is a very poisonous substance. Poisoning by mercury can affect your nervous system and your mind. This sometimes happened to people who made hats and were exposed to mercury for a long time: hence the expression mad as a hatter !

1 Recall why sodium and potassium need to be stored under oil. 2 Describe the element carbon. 3 State one harmful effect of mercury on humans. 4 Recall which problems the alchemists of ancient times tried to solve. 5 Define the term element . 6 Recall which types of substances blacksmiths helped us to understand. 7 Describe how the scientists differed from the alchemists.

THInK 8 Give one reason for displaying chemical safety symbols at the entrances of many buildings. Lewis Carroll s Mad Hatter character in Alice s Adventures in Wonderland was mad because mercury was used in the making of hats.

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9 Hydrogen is an element that is not very dense. How would you describe the density of mercury?

Element name Mercury Nitrogen Oxygen Silicon Silver Sulfur Zinc

Element symbol Hg N O Si Ag S Zn

InVEsTIGATE 10 The element mercury was known to ancient people and was very important to the alchemists. Find out all you can about this liquid metal. What does its name mean? Where is it found? What has it been used for in the past? What is it used for now? What is the safety procedure if mercury is spilt? Why is mercury dangerous? 11 Many years ago, balloons were filled with hydrogen so that they could float high in the sky. However, hydrogen is no longer used in balloons because it explodes too easily. At fairs, carnivals and in florists shops, you can often buy colourful gas-filled balloons that fly high into the sky if you let them go. These balloons are filled with another element called helium. Investigate who discovered the gas helium, where it was discovered and when. eBook plus

12 Play the It s elementary! revelation game in your eBookPLUS and test your ability to identify common elements from their symbols. int-0229

11.3

grouping elements It is often convenient to group objects that have features in common. Shops provide a good example of this. In a department store, the goods are grouped so that you know where to buy them. You go to the clothing section for a new pair of jeans, to the jewellery section for a new watch and to the food section for a packet of potato chips. Scientists also organise objects into groups. Biologists organise living things into groups. Animals with backbones are divided into mammals, birds, reptiles, amphibians and fish. Geologists organise rocks into groups. The elements that make up all substances can also be organised into groups.

Metals and non-metals Scientists have divided the elements into two main groups: the metals and the non-metals.

Metals The metals have several features in common: • They are solid at room temperature, except for mercury, which is a liquid. • They can be polished to produce a high shine or lustre. • They are good conductors of electricity and heat. • They can all be beaten or bent into a variety of shapes. We say they are malleable. • They can be made into a wire. We say they are ductile. • They usually melt at high temperatures. Mercury, which melts at 40 C, is one exception.

non-metals Only twenty-two of the elements are non-metals. At room temperature, eleven of them are gases, ten are solid and one is liquid. The solid non-metals have most of the following features in common: They cannot be polished to give a shine like metals; they are usually dull or glassy. • They are brittle, which means they shatter when they are hit. • They cannot be bent into shape. • They are usually poor conductors of electricity and heat. • They usually melt at low temperatures. • Many of the non-metals are gases at room temperature.

Common examples of non-metals are sulfur, carbon and oxygen.

Metalloids Some of the elements in the non-metal group look like metals. One example is silicon. While it can be polished like a metal, silicon is a poor conductor of heat and electricity and cannot be bent or made into wire. Those elements that have features of both metals and non-metals are called metalloids. There are eight metalloids altogether: boron, silicon, arsenic, germanium, antimony, polonium, astatine and tellurium.

Metalloids are important materials often used in electronic components of computer circuits.

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◗ Connect the circuit shown in the diagram, to determine

InveStIgatIon 11.4

whether electricity passes through each of the elements.

Looking for similarities DIscussIon

You will need: safety glasses samples of sulfur, zinc, tin, carbon, silicon, copper steel wool or very fine sandpaper battery or power pack wires with alligator clips light globe ◗ Make a copy of the table below and use it to record your

observations.

1

Which of the six elements have a shiny surface when polished?

2

Which of the six elements do not have a shiny surface when polished?

3

Which of the six elements can be bent?

4

Which of the six elements cannot be bent?

5

Which of the six elements allow electricity to pass through?

6

Which of the six elements do not conduct electricity?

7

Attempt to divide the elements into two groups on the basis of your observations. Suggest names for these two groups.

8

Which of the six elements tested does not seem to fit into either of these two groups?

◗ Rub each of the elements with the fine sandpaper and

observe whether they are shiny or dull. ◗ Try to bend the metal.

Power supply (transformer)

Lamp

Characteristics of some elements Element

Element to be tested

Shiny or dull?

Does it bend?

Does it conduct electricity?

Sulfur Zinc Tin

Contacts (alligator clips)

Carbon Silicon

Connect your element sample into this circuit.

Copper

activities

IMAGInE

REMEMBER 1 Recall four features that metals have in common. 2 Recall four features that non-metals have in common.

8 Imagine that you are a scientist who has discovered what appears to be a new element. It is golden in colour and very shiny. Propose experiments to test if it is a metal or non-metal. What results would you expect to get if it is a metal?

3 Define the term metalloid . List some examples.

InVEsTIGATE

4 Recall which metal is liquid at room temperature.

9 Polonium is a metal discovered by Marie Curie. She also discovered another metal. Find out its name and the important role it played in medicine.

5 Define the term metallic lustre .

THInK 6 While all metals have similar characteristics, there are also differences between them. List three ways in which metals can differ from each other. 7 Silicon is used in the chips of computer circuits, but it is never used in the connecting wires of electric circuits. Deduce why not.

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work sheets

11.1 The periodic table: atomic structure 11.2 Metals and non-metals

11.4

Compounds There are millions and millions of different substances in the world. They include the paper of this book, the ink in the print, the air in the room, the glass in the windows, the wool of your jumper, the cotton and polyester in your shirt or dress, the wood of your desk, the paint on the walls, the plastic of your pen, the hair on your head, the water in the taps and the metal of the chair legs. The list could go on and on. All substances can be placed into one of three groups: elements, compounds or mixtures. • Elements are substances that contain only one type of atom. Very few substances exist as elements. Most substances around us are either compounds or mixtures. • Compounds are usually very different from the elements that they are made of. In compounds, the atoms of one element are joined very tightly to the atoms of another element or elements. The elements that make up a compound are completely different substances from the compound. For example, common table salt (sodium chloride) is a compound made up of the elements sodium (a silvery metal) and chlorine (a green, poisonous gas). • Mixtures can be made up of two or more elements, two or more compounds or a combination of elements and compounds. The substances that make up mixtures can usually be easily separated from each other. When

the parts of a mixture are separated, no new substances are formed. Fizzy soft drink is a good example of a mixture. It contains water, gas, sugar and flavours. If you shake the soft drink, the gas bubbles separate from the water and go into the air. You still have the water in the bottle and the gas in the air; they are just not mixed together any more. The parts of the mixture can be separated quite easily. The gas escapes when the lid of the container is opened, and the water can be separated by evaporation, leaving behind sugar and some other substances. When the atoms of different elements bond together, a compound is formed. When heated together, the elements iron and sulfur form a new compound called iron sulfide. Iron sulfide has the formula FeS. Every compound has a formula made up of the symbols of the elements that make it up. Unlike mixtures, the elements within a compound cannot be easily separated from each other.

Elements can be separated from the compounds that they make up in a number of ways including: • passing electricity through the compound • burning the compound • mixing the compound with other chemicals such as acids. Each of these methods involves a chemical reaction. Now, let s look at these methods a bit more closely.

A compound is completely different from the elements that it is made of. Table salt consists of the elements sodium and chlorine.

Some common substances Substance

Type

Composed of:

Scientific name

Gold

Element

Gold

Gold

Diamond

Element

Carbon

Carbon

Water

Compound

Hydrogen and oxygen

Dihydrogen oxide

Table salt

Compound

Sodium and chlorine

Sodium chloride

Brass

Mixture

Copper and zinc

Brass

Soft drink

Mixture

Water, sugar, carbon dioxide and other compounds

Sea water

Mixture

Water, sodium chloride and other compounds

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splitting water We are surrounded by water. It is in our taps, in our bodies, in the rivers, in the sea and in the air, and it comes down as rain. We wash in it, cook in it and drink it. We cannot live without water. Water is not an element it can be broken down into simpler substances. The illustration at right shows a piece of apparatus called a Hofmann voltameter. Water is placed in the voltameter, which is connected to a battery. The electricity splits the water into the elements that it is made of: hydrogen and oxygen. Hydrogen and oxygen are both elements. They are both gases, and they look the same; they have no colour and no smell. Hydrogen is a much less dense gas than oxygen. This means that a balloon filled with hydrogen will float up very high, but one filled with oxygen will not.

The element hydrogen is present in all acids. By placing a piece of metal in an acid, the hydrogen is forced out. The hydrogen can be collected and tested with a flame. The element oxygen is present in water, air, rocks and even hair bleach. Oxygen is the gas that all living things need to stay alive. It is also necessary for all substances to burn even hydrogen does not burn in the absence of oxygen. When hydrogen gas is burned, it combines with the oxygen in the air to form water. This releases a lot of energy. If large amounts of hydrogen and oxygen are used, enough energy can be released to lift a space rocket.

Oxygen Hydrogen

Water

6V battery or power supply Water is split in a Hofmann voltameter. The clear gas in the left tube is hydrogen. The gas in the right tube is oxygen. What do you notice about the amounts of hydrogen and oxygen that are produced?

InveStIgatIon 11.5 splitting hydrogen from acid

• carbon dioxide is the gas that is added to soft drinks to give them their fizz. solid carbon dioxide, commonly known as dry ice , is used to keep things cold at outdoor events. • The most abundant compound on planet Earth is water (H2o). Two-thirds of the Earth s surface is covered with water, in which many other compounds (such as salt) are mixed. The compound water is the only substance that is naturally present on Earth in all three states solid (about three-quarters of the Earth s water is frozen near the north and south Poles and in glaciers), liquid and gas (water vapour in the atmosphere). • Your own body contains more water than any other substance about 60 per cent of your body is made up of water. If you think that s a lot, an elephant is 70 per cent water and a tomato is 95 per cent water.

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You will need: safety glasses 2 test tubes and test-tube rack matches dilute hydrochloric acid measuring cylinder magnesium metal

Dilute hydrochloric acid

◗ Measure 10 mL of hydrochloric

acid and pour it into the test tube. ◗ Add a piece of magnesium and

place the second test tube on top of the first, as shown in the diagram. Carefully observe what happens. ◗ After one minute, take the second

test tube off the first. While it is still inverted, immediately light the gas in the second test tube with a match.

DIscussIon 1

Describe what happened in the test tube containing the metal and the acid.

Piece of magnesium metal Collect the hydrogen gas by placing the second test tube over the first.

2

What does hydrogen gas look like?

3

What happened when you lit the gas?

4

Look closely at the second test tube. Describe what you see inside it.

activities

InveStIgatIon 11.6 Making a compound from its elements You will need: 4 5 cm strip of clean, shiny magnesium ribbon. (It can be coiled to fit in the crucible.) crucible with lid pipeclay triangle tongs safety glasses Bunsen burner heatproof mat matches

REMEMBER 1 Describe how compounds differ from elements. Lid Magnesium ribbon inside Crucible

Pipeclay triangle Bunsen burner Tripod

2 Recall the important differences between a mixture and a compound. 3 Recall three ways in which elements can be separated from their compounds. 4 Fizzy soft drink is a mixture of several compounds. List three of the compounds and suggest how each of them could be separated from the mixture. 5 If atoms are bonded together, describe what this means. 6 Recall which elements are present in carbon dioxide.

THInK 7 Describe how you know that water is not simply a mixture of hydrogen and oxygen. ◗ Examine the piece of magnesium and note its appearance before putting it

in the crucible and covering it with the lid. ◗ Put the crucible on the pipeclay triangle as shown in the diagram. ◗ Heat the crucible with a strong blue flame, monitoring the reaction by

occasionally lifting the lid a little with tongs. ◗ When all the magnesium ribbon has been changed, turn off the flame and

leave the crucible on the tripod to cool.

9 How can only 92 different elements make millions of different compounds?

InVEsTIGATE

DIscussIon 1

Describe the substance in the crucible.

2

Is magnesium an element or a compound? Give a reason for your decision.

3

Magnesium is one of the reactants in this experiment. What is the other reactant?

4

Is the substance remaining in the crucible an element or a compound? What is its name?

5

What is the evidence that a new substance has been made?

6

Copy and complete the following word equation to describe the chemical reaction that has taken place.

+ 7

8 Magnesium oxide is a compound of magnesium and oxygen. Describe how you know that it is a completely different substance from each of the two elements it is made up of.

Apart from observing whether the reaction is complete, give another reason for lifting the lid of the crucible a little with tongs during the burning.

10 construct models of some compounds. You may have to work out how many of each type of atom there are in a compound and in what shape they are joined together. 11 Joseph Priestley was one of the first scientists to discover the element oxygen. He also discovered many compounds that are gases. Investigate and report on the life of Joseph Priestley. work sheet

11.3 The periodic table: elements and symbols

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11.5

Mixed up metals Not everyone is good at sport; not everybody can draw; we certainly know that all people are not the same height! Just as people are different, so are the pure metals. And just as you wouldn t pick someone who cannot sing to take the starring role in the school musical, you cannot pick any old metal to do a particular job. For example, iron is very strong so it is great for building bridges, but you wouldn t make a bracelet from it. Gold is good in jewellery because of its lustre and its rarity (which makes it very valuable). However, it is very soft so it cannot be used for jobs that need a strong metal. So, what happens when you need a metal that has a combination of properties that no pure metal has? An alloy is a mixture of pure metals that has properties that the pure metals on their own do not have. They are made by melting the metals that need to be combined and then mixing them together, much as you do with milk and melted butter when you make a cake. Remember, though, that the atoms of the original metals do not combine with each other an alloy is not the same as a compound. Let s look at a few examples of alloys. Bronze is a mixture of copper and tin, and it has been used for over 3000 years to make weapons, statues, coins and bells. It is very strong and durable much stronger than either copper or tin. Many of the large statues that you see in public places, such as the statue of Queen Victoria outside the Queen Victoria Building (QVB) in Sydney, are made of bronze.

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While bronze is deep brown in colour to start with, it can get a whitish green coating, called verdigris, on it when it has been exposed to air and moisture. Brass is commonly used for fittings on boats because it is resistant to the corrosion that other metals suffer when exposed to salt water for a long time. It is a mixture of copper and zinc and has a bright gold appearance. The musical instruments such as tubas, trumpets and trombones that you find in the brass section of the orchestra are made of brass. Bronze statue of Queen Victoria outside the Queen The properties of an alloy can be adjusted by Victoria Building in Sydney using different proportions of the metals that make them. When different proportions of carbon are added to iron, they form different grades of steel. Steel contains between 0.2 and 2 per cent carbon. The more carbon there is in steel, the stronger and harder it is. However, more carbon also makes steel more brittle. Alloy Bronze Brass

Made of Copper, tin Copper, zinc

Steel Stainless steel Rose gold Solder

Iron, carbon Iron, nickel, chromium Gold, copper Lead, tin

activities

Used for making Statues, coins Engine parts, decorative fittings, musical instruments Bridges, buildings, car parts Cutlery, kitchen fittings Jewellery Joins for electrical components

6 Draw a picture of the atoms in a sample of brass. Provide a key that identifies the atoms present.

REMEMBER 1 Define the term alloy . 2 Explain why alloys may be used instead of pure metals for some purposes. 3 Identify the alloy in the table above that contains a non-metal. What is the non-metal?

THInK 4 Lead melts at 327 C and tin melts at 232 C, yet solder s melting point is 183 C. Explain this surprising fact. 5 Describe the properties of alloy wheels that could not be provided by a pure metal.

InVEsTIGATE 7 Although our coinage looks silver and gold, it is actually made of different alloys. Investigate how our coins are made and what metals are used to make them. 8 What was the Bronze Age and when did occur? Research this time period and find out what life was like back then. 9 Is it possible to separate the metals of an alloy once they have been mixed? Investigate this using your library and the internet. work sheet

11.4 Alloys

11.6

Making molecules The naturally occurring elements are the building blocks of everything in our world. The atoms of various elements can be joined in a wide variety of ways to produce many compounds. Elements and compounds can be combined in many ways to make countless mixtures. Atoms can join, or bond, in many different ways. In some substances, atoms are joined in groups called molecules. For example, in oxygen gas, oxygen atoms are joined in groups of two. In the

compound carbon dioxide, there are one carbon and two oxygen atoms joined in every molecule. Atoms can join to form small or large molecules of many different shapes. Some compounds are not made up of molecules. Instead the atoms bond by lining up one after the other. Sodium bonds to chlorine, which bonds to sodium and so on. Common table salt is an example of a substance that is bonded in this way.

◗ Cut out 15 squares, with each

InveStIgatIon 11.7

(a) water, which contains 1 oxygen and 2 hydrogen atoms (b) methane (natural gas), which contains 1 carbon and 4 hydrogen atoms (c) benzene (in petrol), which contains 6 carbon and 6 hydrogen atoms (d) glucose (sugar), which contains 6 carbon, 12 hydrogen and 6 oxygen atoms (e) hydrogen peroxide (found in hair bleach), which contains 2 oxygen atoms and 2 hydrogen atoms.

side 2 cm, from the blue sheet of paper.

Mix n match You will need: green, red and blue sheets of paper scissors, pencil, ruler 1 large sheet of cartridge paper ◗ Cut out 25 diamonds, each 2 cm

long and 1.5 cm wide, from the green sheet of paper. ◗ Cut out 30 equilateral triangles, with

each side 2 cm, from the red sheet of paper. 1.5 cm

◗ Imagine that different types

of atoms are represented by particular shapes: a blue square = carbon a green diamond = oxygen a red triangle = hydrogen and that, by placing them side by side on the sheet of paper, you are joining them. ◗ Place two green diamonds

next to each other on the sheet. This represents the element oxygen, as shown in the diagram below.

DIscussIon 2 cm

2 cm

2 cm

A green diamond represents an atom of oxygen. Together, two diamonds represent a molecule of oxygen.

1

Which of these compounds contain only hydrogen and carbon atoms?

2

In what ways are these two substances different from each other?

3

Which of the compounds contain only oxygen and hydrogen? Do these compounds have the same characteristics?

4

Think about the appearance of the compound sugar. How does it differ in appearance from the elements that it is made of?

2 cm ◗ Place one blue square on the sheet

2 cm 2 cm Cut these shapes from coloured paper.

between two green diamonds. This represents the compound carbon dioxide. Label it with its name and symbol. ◗ Represent and label the following

substances:

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compounds of today and tomorrow Polymer is the name given to a compound made of molecules that are long chains of atoms. Most polymers are made up of chains containing carbon atoms. Plastics are synthetic polymers. Cotton and rubber are examples of natural polymers. Although scientists first developed polymers in laboratories in the 1800s, it was not until after World War II that most of the modern polymers were invented. Modern polymers are used in food wrapping, paint, plastic glass , polystyrene foam for packaging and cups, banknotes, cases for electronic appliances such as computers and televisions, clothing, glues, shopping bags, sports equipment and even tea bags!

(a)

(b)

activities REMEMBER 1 Define the term molecule . Name two compounds that are made up of molecules. 2 Are all compounds made up of molecules? Explain. 3 Name four elements that are made up of molecules.

(c)

4 Define the term polymer .

THInK Models representing the molecules of the compounds (a) carbon dioxide, (b) water and (c) methane. The black balls represent carbon, the red, oxygen, and the white, hydrogen.

5 Recall the difference between an atom and a molecule. 6 Copy and complete the table below. Use the formula of each compound to deduce how many elements are present and which ones they are. (The formula of a compound not only tells you which elements are present, but also indicates the ratio of atoms of the different elements. For example, in the compound NH3 there are three hydrogen atoms for each nitrogen atom.) Compound

• nitrogen is an element. It is a clear, colourless gas made up of molecules. Each molecule is made up of a pair of atoms. nitrogen makes up 80 per cent of the atmosphere. That means that four-fifths of each breath you take in is nitrogen. our bodies cannot use this nitrogen so we breathe it straight out again! The gases oxygen, hydrogen and chlorine also exist as molecules made up of pairs of atoms. • Gold is the only metal element found in large amounts in its pure form, rather than bonded in compounds with other elements. • It has been calculated that nearly half of the weight of the Earth s crust is due to the element oxygen! Most rocks contain compounds that include the element oxygen.

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Copper sulfate

Formula

Number of elements

CuSO4

3

Zinc sulfide

ZnS

Ammonia

NH3

Sulfuric acid

Names of elements Copper, sulfur, oxygen

H2SO4

Hydrochloric acid

HCl

Table salt

NaCl

InVEsTIGATE 7 Australia has led the way in the production of polymer money. Find out all you can about how these banknotes are made. eBook plus

8 Complete the Making molecules interactivity in your eBookPLUS by creating the correct model of the molecule as each chemical formula appears. int-0228 work sheet

11.5 Making compounds

11.7

Carbon

the stuff of life

That s made of carbon?

Finding carbon

Carbon is a most amazing element. It is found in three different forms. One form is diamond, another is graphite (the lead in lead pencils), and the third is called amorphous carbon (coal, charcoal and soot). The three forms are different from each other because the carbon atoms are joined in different ways. Diamond, graphite and amorphous carbon are called carbon allotropes. Allotropes of an element have different appearances and properties due to differences in their molecular structures. It is possible to change one form into another. Amorphous carbon can be changed to graphite by mixing it with sand and heating the mixture to about 2000 C. To change graphite to diamonds, huge pressures and very high temperatures are needed. This occurs deep within the Earth over long periods of time, and can also be done in special factories. Diamonds do not melt! When heated they change straight from solid to gas. This happens at about 3500 C. Diamond is the hardest substance known and is used to make drill tips and cutting tools. Carbon is found combined with other elements in a huge range of compounds. No other element forms as many different compounds as carbon. Carbon is found in everything from the skin of an elephant to paint on the walls!

Carbon is one of the five elements that were discovered by the alchemists (see page 293). Concentrated sulfuric acid can be used to detect the presence of carbon in sugar. This acid is too dangerous for you to use in the classroom, but the diagram on the right shows what happens when sulfuric acid is poured over some sugar in a beaker. The sulfuric acid changes the other elements in sugar into different substances, leaving the carbon behind as charcoal.

Sulfuric acid Cone of charcoal

Sugar 250 mL beaker

When sulfuric acid is added to sugar, the beaker gets very hot, steam escapes and the element carbon is left behind.

The three forms of carbon: diamond, graphite and amorphous carbon

A company in switzerland uses the ashes of dead people to make diamonds. Their clients want a permanent memento of their loved ones and are prepared to pay around $10 000 Australian dollars. To create the diamonds, the ashes are prepared and then placed under high temperature and high pressure for weeks. The diamonds can then be cut and polished into the desired shape and even inscribed with a laser.

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InveStIgatIon 11.8 It s elementary, my dear Watson! You will need: safety glasses Bunsen burner, heatproof mat and matches metal tongs small samples of substances to investigate (such as woollen cloth, cotton wool, sugar cube, wood, bread, peanut, steel wool, glass, paper and aluminium foil) ◗ The early scientists were investigators, working methodically to find an

answer to a mystery, a bit like the famous detective Sherlock Holmes. The scientists searched for elements in everyday substances. Your task in this experiment is to find out if the element carbon is present in some common substances. Earlier investigators discovered that carbon can be detected if a substance turns black when it is burnt. ◗ Your teacher may allow you to burn some plastic in the fumehood.

CAUTION Burning plastics produce poisonous fumes. A fume cupboard must be used. ◗ Hold a small piece of the substance you are going to test in the metal tongs. ◗ Put it in the blue flame of the Bunsen burner. ◗ When it catches alight take it out of the flame and, keeping it above the

heatproof mat, allow it to burn slowly. Does it turn black? ◗ Draw up a table like the one below and record your observations.

DIscussIon 1

In which of the substances tested is carbon present?

2

Can you be sure that, if the substance went black, carbon was present? Give a reason for your answer.

3

Can you be sure, if a substance didn t go black, that it didn t contain carbon?

4

Give a reason for your answer.

Substance

Observations

Is carbon present?

Wood Cotton wool

The chemistry of life All living things are made up of compounds including proteins, fats and carbohydrates. The main element in these compounds is carbon. Carbon is not found only in living things. It is also found in the air in carbon dioxide and under the sea in limestone. The carbon atoms in carbon dioxide were once carbon atoms in living things. The carbon atoms in living things will eventually become carbon atoms in the air or carbon atoms in limestone under the sea. The illustration opposite shows how nature constantly recycles carbon atoms.

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Plants take in carbon dioxide through their leaves and, in a process known as photosynthesis, use the carbon dioxide and water to make starch. Starch is a compound made up of carbon, hydrogen and oxygen atoms. Plants use the starch to make other substances and for energy to grow. Animals eat plants or planteating animals. The carbon atoms then become part of the animals bodies. Carbon atoms in the bodies of living things return to the air in several ways. These ways are respiration, decomposition and burning. • Respiration is a process that occurs in the cells of every living thing, from a microscopic water plant to a humpback whale. Respiration releases energy and produces carbon dioxide. The carbon dioxide released by the cells in your body is taken by your blood to your lungs. The carbon dioxide that you breathe out contains carbon atoms that were once part of your body. • Decomposition is what happens when plant or animal material breaks down, such as in a compost heap or after something is buried. Microscopic living creatures called decomposers absorb some of the substances in the dead material and release carbon dioxide to the air by respiration. • When substances containing carbon are burned, carbon dioxide is released. Coal, natural gas and oil are all fuels formed from living things, and contain carbon atoms. When these fuels are burned in homes, cars, factories and power stations, carbon dioxide is released into the air. Bushfires also release carbon dioxide back to the air.

Plants absorb some oxygen.

Animals breathe in oxygen.

Plants absorb CO2 during the day.

Both plants and animals release CO2.

Plants release oxygen during the day.

Fossil fuels release CO2 when burned.

Animals absorb carbon when they eat plants.

Petroleum

Oil

Gas

Coal

The flow of carbon atoms through the environment

activities REMEMBER 1 Recall and describe the three different forms of the element carbon. 2 Recall where plants get the carbon from that they need to make starch. 3 Describe three ways in which carbon can return to the atmosphere. 4 Recall where respiration takes place. 5 Define the term allotrope . 6 Define the term decomposition .

THInK 7 Describe how animals obtain carbon. 8 Where does the carbon come from to form limestone at the bottom of the sea? 9 The amount of carbon dioxide in the Earth s atmosphere is increasing. Deduce why this is happening.

10 When sulfuric acid (chemical formula H2SO4) is added to sugar (chemical formula C12H22O11), it produces steam (H2O) and a large amount of a black, cindery solid. (a) Identify the elements present in (i) sulfuric acid, (ii) sugar and (iii) steam. (b) Given that none of the elements has vanished, deduce which elements are present in the black solid. (c) Sulfur is generally a bright yellow powder. Deduce why it is not readily seen in the black solid. 11 Would it be possible for life to continue on Earth without plant life? Explain your answer.

GRAPH AnD AnALYsE 12 Many different materials are used to provide heating. The table above shows how much carbon there is in each of them. The last column indicates how much heat (in therms) that 50 kg of that material provides.

Material Wood Peat Lignite Black coal Brown coal Natural graphite

Carbon content (%) 11 10 30 80 73 90

Heat production (therms) 8.5 10 12 17 14 18.5

(a) Draw a bar graph showing the percentage carbon content of each material. (b) Deduce which is the best material to use to provide heat. (c) Does the table indicate any relationship between the amount of carbon in a material and the amount of heat that it provides? Explain your answer clearly.

InVEsTIGATE 13 Investigate the greenhouse effect. How is it related to carbon dioxide? work sheet

11.6 Carbon

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11.8

PREscRIBED Focus AREA History of science

Development of the atomic model In science, as in any other field of knowledge, models and theories are put forward to explain observations. When evidence is found that contradicts these models and theories, they are modified to fit the new information or they may even be rejected altogether. In this way, our ideas about what an atom looks like have been developed over thousands of years. In the fifth century BC, Democritus proposed the idea that all matter was made up of small particles that he called atoms. Over the next two thousand or so years, people argued over whether atoms actually existed. Even those who believed in the idea of atoms had no real idea of what the atoms actually looked like, and there was a general tendency to regard these mysterious little things as being very small solid balls of stuff, a bit like very tiny marbles. It wasn t until the eigtheenth century that scientists turned their attention to finding out whether atoms existed and what an atom actually looked like.

John Dalton (1766 1844) John Dalton is considered to be a pioneer of modern atomic theories. In his 20s and 30s, he experimented extensively on gases to learn more about them and the particles they are made of. Based on his observations, he arrived at a number of important conclusions about matter and atoms, which he presented in 1803. Dalton’s atomic theories 1. Matter is made up of atoms that are indivisible and indestructible.

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2. All the atoms of an element are identical. 3. Atoms of different elements have different masses and different chemical properties. 4. Atoms of different elements combine in simple whole numbers to form compounds. 5. Atoms cannot be created or destroyed in a chemical process. When a compound decomposes, the atoms separate but are themselves unchanged.

model in which the atom was a sphere of positive charge that had negative charges (which he called electrons) scattered through it, much like sultanas and plums in a plum pudding. Not surprisingly, this is called the plum pudding model of the atom.

JJ Thomson Positive charge

John Dalton

JJ Thomson (1856 1940) JJ Thomson experimented with electric charges and cathode ray tubes (which were used in the twentieth century to produce pictures in television sets). He suggested that the glow produced in the tube when electricity was passed through it was due to the movement of small corpuscles. He believed these negatively charged particles to be parts of the atom itself. Further experimentation with gases seemed to suggest that there were both negative and positive charges in the atom. In 1904, he proposed an atomic

The plum pudding model

Negative charges (electrons)

Ernest Rutherford (1871 1937) Rutherford s ideas of the atom came as the result of experiments he was doing in which he fired positive charges at gold atoms. He found that some of the positive charges could pass right through the atom and, in some cases, the charges bounced right back.

If Thomson s model was correct, this would not have happened. Rutherford proposed a new model of the atom that explained his observations. In this model, the atom was mostly empty space, with all of its positive charge in a clump in the centre (the nucleus). He thought that the electrons moved around the nucleus in fixed orbits, much as planets do around the sun. For this reason, Rutherford s model is sometimes called the planetary model of the atom.

then, hadn t been able to explain. Bohr agreed with Rutherford that the atom was mostly empty space and that most of the mass was in the nucleus where the positive charges were located. However, he proposed that the electrons changed orbits and so they formed electron clouds around the nucleus. In this model, it was impossible to predict exactly where an electron was at a particular time.

Positive charge

Electron cloud Bohr s model of the atom

And now? At the moment, Bohr s model of the atom is the most consistent with what scientists observe happening in experiments. However, there are still a few things that even this version cannot explain. One day, a new model will be developed to explain what Bohr s model cannot.

Neils Bohr

Ernest Rutherford

activities REMEMBER

Positive nucleus

Electron Rutherford s model of the atom

niels Bohr (1885 1962) Niels Bohr saw that, if Rutherford s model of the atom was correct, atoms would be very unstable and matter would fall apart all the time, and this didn t happen. Bohr s model of the atom was a lot more complicated but seemed to be consistent with what scientists observed, and it explained a lot of strange things that science, up to

Date

Event

Fifth Democritus proposed the century existence of atoms. BC

1 Recall which model of the atom is currently used.

1804

Dalton developed his theory of atoms and matter.

2 Describe how Thomson s model of the atom differed from that of Democritus.

1897

JJ Thomson discovered the electron.

1911

3 Explain why the model of the atom has changed over the centuries.

Rutherford developed the planetary model of the atom.

1913

4 compare and contrast Rutherford s and Bohr s models of the atom.

Bohr developed a model of the atom.

1919

The proton was discovered.

1932

The neutron was discovered.

5 Explain why Rutherford s model is called the planetary model.

InVEsTIGATE cREATE 6 The table below shows when different events in the development of the atomic model occurred. Use these dates to construct a timeline of the events. Remember that you will need to choose an appropriate scale!

7 Bohr s model of the atom is also called the quantum model. Find out what a quantum is. 8 Many of the scientists mentioned on pages 306 7 won Nobel prizes for their work. Use the library and the internet to discover who won a Nobel prize and what for.

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LooKIng BaCK 1 Copy and complete the following table, which describes the structure of atoms. Part of atom

Location

Size and weight (relative)

Electric charge

Large

Positive

6 Describe what diamonds, the lead in pencils and coal have in common. 7 Identify which of the bits of matter is represented by each of the cartoons below.

Neutron Outside the nucleus 2 Complete the following table to summarise what you know about metals and non-metals. Property

Metals

Non-metals

Conduct electricity well Conduct heat well Surface features State at room temperature

8 Each of the diagrams below represents one of the bits of matter that make up substances.

Malleable Ductile Brittle

A

B

C

D

E

F

G

H

I

3 Identify which of the following are (a) metals and (b) nonmetals. chlorine gas, sodium, silver, lead, sulfur, oxygen, silicon 4 Most of the substances around you are compounds and mixtures. (a) Describe the differences between a mixture of hydrogen and oxygen and a compound of hydrogen and oxygen. (b) In your own words, explain the difference between a compound and a mixture. (c) Deduce which elements you would be most likely to find in their pure form around the home.

J

L

5 Complete the table below to identify whether the substances listed are elements, compounds or mixtures. Explain your decisions. Substance

Element, compound or mixture?

Gold Diamond Carbon dioxide Air

Why do you think so?

Identify which of the diagrams represents: (a) an atom of an element (b) a molecule of an element (c) a molecule of a compound. 9 The famous crime writer Agatha Christie mentioned the metalloid arsenic frequently in her novels. Propose why it was important in her stories.

Sea water Pure water Iron Ammonia Table salt (NaCl)

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10 Imagine you are a scientist who is investigating what is produced when various chemicals are mixed together. In one reaction a hard, bright green solid is produced. You do not know what it is. Suggest some tests you could do to help you decide whether it is an element or a compound.

11 Identify which of the following substances are elements, compounds and mixtures: gold, air, carbon dioxide gas, sea water, oxygen gas, sodium chloride, graphite, orange juice, aluminium metal, icecream, pure water. 12 Are all allotropes molecules? Explain. 13 Describe the plum pudding model of the atom. 14 What is an alloy? Identify the metals that make up the following alloys: (a) bronze (b) solder (c) stainless steel (d) brass.

TEsT YouRsELF 1 A compound is a substance that is A made up of one type of atom. B made up of different atoms mixed together. C always a solid. D able to be broken down into the elements it is composed of. (1 mark) 2 The central section of an atom is called the A nucleus. B electron. C middle. D neutron. 3 The chemical symbol for silver is A Si. B S. C Ag. D Sr.

(1 mark)

4 The plum pudding model of the atom was first proposed by A Democritus. B Ernest Rutherford. C Niels Bohr. D JJ Thomson. (1 mark) 5 Imagine you are a scientist in charge of developing new materials. The Australian Space Agency has approached you because they need a new substance to coat the outside of the space shuttles they are designing. The substance must be: • able to withstand the heat of the shuttle re-entering the Earth s atmosphere • flexible enough to bend when the wings of the shuttle bend • strong enough to stand the vibration of take-off, landing and other movement • light enough to be part of a flying spacecraft • resistant to chemical attack • able to reflect the solar radiation in space. Your task is to design the coating for the space shuttle. Include: (a) whether it will be solid, or an innovative liquid or gas coating. It could be a combination of these in layers or as a mixture! (b) what atoms, elements or compounds it will be made of (c) how the coating of substances will work to meet the criteria from the Australian Space Agency. This will include the properties of your substances and how they are put together. (d) a drawing of your coating indicating its special features and how it works. (6 marks) work sheets

11.7 Bits of matter puzzles 11.8 Bits of matter summary

(1 mark)

11 11 BitsBitsthat of matter

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StUDY CHeCKLISt Atoms

ICt eBook plus

■ describe the structure of an atom 11.1 ■ recall the three main particles that make up an atom and where they are found in the atom 11.1 ■ explain what makes atoms different from each other 11.1 ■ recall how an atom differs from a molecule 11.6

SUMMaRY

Interactivities It s elementary! revelation game In this revelation game, you must identify common elements from their symbols to reveal the full periodic table. You must answer quickly to complete the game in time.

Elements ■ contrast the characteristics of metals and non-metals

11.3

■ classify common elements as metals or non-metals

11.3

■ identify the chemical symbols for common elements

11.2

■ distinguish between natural and synthetic elements

11.2

■ define the term allotrope 11.7 ■ describe what is meant by the term alloy 11.5 ■ recall the metals that make up common alloys such as brass, steel and bronze

11.5

■ describe how carbon is recycled in nature 11.7 compounds ■ describe how elements are different from compounds

11.4

■ describe how compounds differ from mixtures 11.4,

Searchlight ID: int-0229 Making molecules In this interactivity, you will use carbon, chlorine, hydrogen, nitrogen and oxygen atoms to create the correct models of a series of chemical formulae. Instant feedback is provided.

11.5

■ recall examples of compounds that are made up of the same elements which differ in their physical properties 11.4 ■ identify common compounds 11.4 ■ explain how compounds may be broken up into their component elements 11.4

History of science ■ compare the models of the atom put forward by Dalton, Thomson, Rutherford and Bohr

11.8

Searchlight ID: int-0228

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12

Chemical reactions

Chemical reactions are happening everywhere. Chemical reactions in your body digest food, decay your teeth and much more. Chemical reactions occur in batteries to provide electricity, in the oven when you bake a cake, in your hair when it is bleached or coloured and in your car when it burns fuel. The list goes on and on and on.

In this chapter, students will: 12.1 ◗ distinguish between physical and

chemical changes and learn the signs that a chemical change has taken place 12.2 ◗ distinguish between reactants and

products and use word equations to describe chemical reactions 12.3 ◗ apply a number of techniques to

change the rate of a chemical reaction 12.4 ◗ investigate the chemical reaction

involved in the corrosion of iron 12.5 ◗ learn about the reactions involved in

combustion and burning 12.6 ◗ learn how pH distinguishes acids from

bases, and how neutralisation of acid with a base can help indigestion 12.7 ◗ learn how the increased use of fossil

fuels has caused the environmental problem of acid rain.

Chemical reactions can be explosive and colourful as during this launch of a scramjet rocket in Woomera, South Australia.

12 Chemical reactions What is a chemical reaction? You ve probably already heard a lot about chemical reactions at school, on television, at the movies or in books. But what is a chemical reaction, and how do you know whether a chemical reaction has taken place?

Check out the images on this page and answer the questions based on what you already know about chemical reactions. 1. The boiling liquid in the pot at left is changing colour. It began as a mixture of reds, greens and blues and, after stirring, is changing into an dangerouslooking, yellow soup. (a) Write down your opinion about whether or not a chemical reaction is taking place. (b) Explain how you know whether a chemical reaction has taken place. (c) Is there a chemical reaction taking place underneath the pot? Explain your answer. (d) Clouds are forming above the pot. Is this evidence of another chemical reaction? Explain your answer. 2. Does a chemical reaction take place when you burn toast? What observations support your answer? 3. Does a chemical reaction take place when you toast bread without burning it? Explain your answer.

4. Is the frozen substance in this man s beard and the inside edge of his hood the result of a chemical reaction? Explain your answer.

5. Runners in long-distance races sweat heavily. The water lost due to sweating evaporates from the skin. Is this evaporation an example of a chemical reaction? Explain your answer.

6. What happens when you use detergents? Are these chemical reactions?

12.1

time for a change? Have you noticed the way that things change? When a tub of ice-cream is left on the table on a warm day, the ice-cream melts. When water is heated, it may turn into a vapour. When an apple is sliced, it turns brown. In chapter 2, we looked at some of these changes when we studied the changes of state that matter may undergo as a result of adding or removing energy. For example: • When energy is added to a solid, it melts to form a liquid. If we keep adding energy to the liquid, it boils or evaporates to form a gas. • When we remove energy from a gas by cooling it, the gas condenses to form a liquid. If we keep cooling it, that liquid freezes to form a solid. All of this may explain the icecream and the water, but does it explain why the sliced apple turned brown?

Physical changes All of the changes of state we ve described are physical changes.

A physical change does not break any bonds between the atoms of a molecule or make different substances with different atoms. When water is in the form of ice, it is made up of water molecules, each of which is made up of one oxygen atom and two hydrogen atoms. When the ice is turned into water or into water vapour, it is still made up of water molecules. Another characteristic of a physical change is that it is usually reversible. Water can be turned into ice and then back into water again very easily.

chemical changes Substances are said to have undergone a chemical change when the particles that make them up undergo change. Usually this occurs when the chemical bonds between particles in molecules are broken or when new chemical bonds are formed. There are a number of different ways that you can tell if a chemical change has occurred: Evaporation

Melting

• A new substance is formed. • A solid appears or disappears. • The temperature of the substances changes spontaneously. • A colour change occurs. • Bubbles appear. • A flame appears or light is produced. When you hard-boil an egg, for example, you can see that a chemical change has taken place because the albumen has changed from a clear liquid to a rubbery white solid, while the yolk has changed from a translucent yellow liquid to a paler yellow, crumbly solid. Most chemical changes are difficult to reverse. Once the egg has been cooked, you cannot turn it back into its raw state. Obviously a little commonsense is needed here though. For example, if you drop a raw egg and the shell breaks, you cannot reverse what has happened, yet this is not considered to be a chemical change. When a sliced apple turns brown, this indicates that a chemical change has occurred to the surface of the apple. This particular change is a form of oxidation, a chemical reaction that we will look at in more detail later.

How does a candle burn? Solid

Liquid

Freezing Changes of state are physical changes.

Gas

Condensation

Sometimes, a process that seems very simple is the combination of both physical and chemical changes. Let s look at the example of a burning candle.

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When you try to light a piece of solid wax it melts, but it does not burn. If solid wax doesn t burn, how does a candle burn? Is it the string wick that is in the middle of the candle that burns? String burns, but it doesn t burn as a candle does. How then does a candle burn?

How does a candle burn?

When you light the wick of a candle, the wax at the top of the candle melts. The molten wax is drawn up the wick, just as water

soaks into a paper towel. As the liquid wax flows up the wick and gets closer to the heat of the flame it evaporates. The wax vapour mixes with oxygen in the air and burns.

How does a cake rise? When an acid is added to bicarbonate of soda, a new substance carbon dioxide gas is produced. This process is a chemical change and is used in cakes to help them rise during the cooking process. Baking powder is a mixture of bicarbonate of soda and cream of tartar. When baking powder is added to cakes, the cream of tartar dissolves in the liquids of the cake mixture and forms tartaric acid. This acid is then available to react with the bicarbonate of soda. Self-raising flour contains baking powder so, when a recipe includes self-raising flour and a liquid, you know that the cooking process will involve a chemical

InveStIgatIon 12.1

Describing change In a burning candle, there are both physical and chemical changes. The melting of solid wax to form liquid wax and the evaporation of liquid wax to form wax vapour are physical changes. The burning of wax vapour is a chemical change. The wax vapour reacts with oxygen in the air to form new substances including carbon dioxide and ash. Physical and chemical changes can be described using word equations. Melting chocolate can be described by the equation: solid chocolate

liquid chocolate

The burning of paper can be described by the equation: paper + oxygen

smoke + ash

◗ To confirm that the white vapour is not smoke, carry out

the following test.

A burning candle

◗ Relight the candle. Once it is burning properly, blow it out.

You will need: safety glasses candle jar lid matches heatproof mat

◗ Quickly light the top of the vapour trail. The flame should

◗ Place a jar lid on a heatproof mat. ◗ Light a candle and allow a drop of wax to drip onto the

jar lid. Place the candle on the drop of wax and fix it to the jar lid. ◗ Observe the candle and write down as many

observations of the burning candle as you can.

run down the vapour to the wick and relight the candle.

Discussion 1

How far is the flame from the solid wax?

2

The solid wax has formed a little pool of liquid wax around the wick. Why has this happened?

3

Describe the odour of the vapour.

CAUTION Do not smell the vapour directly. Fan the odour to your nose with your hand. 4

Draw a diagram of a candle and its flame. Label this diagram to explain how a candle burns.

5

Explain why lighting the wax vapour causes the candle to relight.

◗ Discuss your observations with others in your group. ◗ Blow out your candle and you will see the white vapour

rising from the top of the wick.

314

change. The carbon dioxide gas produced during this chemical change rises through the cake mixture as it cooks and helps to aerate it.

Core Science | Stage 4 Complete course

◗ Stop stirring the mixture when it boils.

InveStIgatIon 12.2 How can you tell a chemical reaction has taken place? You will need: 110 g sugar 150 mL cold water 500 mL beaker hotplate stirring rod 220 C thermometer test tube patty pans heatproof mat electronic balance measuring cylinder 2 teaspoons of golden syrup half a spatula of cream of tartar half a spatula of bicarbonate of soda laboratory coat and safety glasses ◗ Mix the sugar, cold water, golden syrup and cream of

tartar in the beaker. ◗ Gently heat and stir the mixture over the hotplate until the

sugar has completely dissolved.

◗ Allow the mixture to reach 154 C, and then remove it

from the hotplate. CAUTION The beaker and the mixture are very hot. Remove them from the hotplate with care. ◗ Dissolve the bicarbonate of soda in 1 2 mL of

warm tap water in the test tube. Pour the dissolved bicarbonate of soda into the sugar mixture, stirring gently. ◗ Pour the hot mixture into patty pans. ◗ Allow to cool before examining.

Discussion What evidence is there that a chemical reaction has taken place?

THinK

activities

6 Copy and complete the table below. 7 Write two word equations to describe the changes of state that occur when a candle burns.

REMEMBER 1 Describe the difference between a physical and a chemical change. 2 Recall two examples of physical change. 3 Recall two examples of chemical change. 4 identify which term goes with each definition. Definition

Term

Change from solid to liquid

Freezing

Change from gas to liquid

Melting

Change from liquid to solid

Condensation

Change from liquid to gas

Evaporation

8 Write a word equation to describe the chemical change that occurs when a candle burns. 9 When you hard-boil an egg, the inside of the egg gets hard. Explain why this is a chemical change and not a physical change.

cREATE 10 Candles are a good example of both physical change and chemical change. Write a poem about a candle burning. work sheet

12.1 Physical and chemical changes

5 Recall which type of physical change can always be reversed by heating or cooling. Observation

Physical or chemical change

Water freezing to form snow A cake cooking Lighting the gas on the stove Petrol evaporating at the petrol pump Lighting a match Steam condensing on the bathroom mirror Melting gold to cast gold bars Dynamite exploding Bleaching a stain Dissolving eggshell in acetic acid

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12.2

Describing chemical changes When a chemical change occurs, new substances are produced. The process of producing new substances is called a chemical reaction. Almost all the products you use or wear each day are made by chemical reactions: from cosmetics to concrete, plastics to paper, glass to graphite, stainless steel to shampoo, fibres to food additives, margarine to medicines and many, many more. You can usually tell that a chemical reaction has taken place if there is a change in colour, a gas is given off, heat or light is produced or a precipitate (cloudiness) appears.

Reactants and products The substances that you begin with in a chemical reaction are called the reactants; the substances that are produced are called the products. When you wash the dishes, a chemical reaction occurs between the detergent and the mess on the dishes. When you shampoo your hair, some of the chemicals in the shampoo react with the greasy substances on your scalp that contain dust, dirt and tiny organisms like bacteria that can make your hair unhealthy. When you turn on a battery-powered torch, a chemical reaction takes place in the batteries that causes the flow of electrons (electric current) to move through the bulb and the torch lights up.

Chemical reaction experiments Before you start each of the four experiments on these two pages, design a suitable table for recording your observations. As you do the experiments: 1. Make a note of the appearance of the reactants you are starting with. 2. Observe carefully to detect any changes that occur. 3. Describe the products of the reaction.

InveStIgatIon 12.3 Magnesium metal in hydrochloric acid You will need: heatproof mat safety glasses test tube and test-tube rack 1 cm piece of magnesium ribbon dropping bottle of 0.5M hydrochloric acid ◗ Put the magnesium in the test tube. ◗ Add 20 drops of hydrochloric acid to the test tube.

CAUTION The test tube may become quite hot. ◗ Record your observations.

Discussion What observation provides evidence that a chemical reaction has taken place?

InveStIgatIon 12.4 Heating copper carbonate You will need: Bunsen burner, heatproof mat and matches safety glasses test tube and test-tube rack test-tube holder spatula copper carbonate powder ◗ Pour two spatulas of copper carbonate in the test

tube. ◗ Using the test-tube holder, heat the test tube.

Remember to move the test tube in and out of the flame and point the test tube away from people. ◗ Stop heating when the copper carbonate has

changed colour. ◗ Record your observations.

Safety glasses should always be worn during experiments involving chemical reactions.

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Discussion What observation provides evidence that a chemical reaction has taken place?

InveStIgatIon 12.5 sodium sulfate and barium chloride You will need: heatproof mat safety glasses test tube and test-tube rack test-tube holder dropping bottle of 0.1M sodium sulfate solution dropping bottle of 0.1M barium chloride solution ◗ Put 20 drops of sodium sulfate

solution in the test tube. ◗ Add 20 drops of barium chloride

solution to the test tube. ◗ Record your observations.

Discussion What observation provides evidence that a chemical reaction has taken place?

Writing word equations Each of the chemical reactions in the experiments on these two pages can be described by a word equation. In each case, the reactants are on the left side of the equation and the products are on the right side of the equation. 1. When magnesium metal reacts with hydrochloric acid, hydrogen gas and magnesium chloride are formed: magnesium + hydrochloric acid

hydrogen gas + magnesium chloride

2. Heating copper carbonate forms copper oxide and carbon dioxide: heat

copper carbonate

copper oxide + carbon dioxide gas

Although heat is required for this chemical reaction, it is not a substance and therefore is not a reactant. For this reason, heat is written above the arrow. 3. The sodium sulfate and barium chloride in the solution react to form solid barium sulfate and sodium chloride, which remains dissolved in the solution: sodium sulfate + barium chloride

solid barium sulfate + sodium chloride

4. Steel wool (which is made of iron) dissolves in copper sulfate solution to form iron sulfate solution and copper metal: iron + copper sulfate solution

iron sulfate solution + copper

InveStIgatIon 12.6 steel wool in copper sulfate solution You will need: heatproof mat safety glasses test tube and test-tube rack glass stirring rod 1 cm ball of steel wool dropping bottle of 0.5M copper sulfate solution ◗ Put the steel wool in the test

tube, using the glass stirring rod to push it gently to the bottom of the test tube. ◗ Add copper sulfate solution

to the test tube to a depth of 2 cm. ◗ Record your observations.

Discussion What observation provides evidence that a chemical reaction has taken place?

activities REMEMBER 1 Recall four observations that could provide evidence that a chemical reaction has taken place. 2 When magnesium metal reacts with hydrochloric acid, hydrogen gas and magnesium chloride are formed. (a) identify the products. (b) identify the reactants.

produce carbon dioxide and water. (b) Sodium metal reacts with chlorine gas to form sodium chloride. (c) Hydrogen gas and oxygen gas combine to form water. (d) Zinc metal dissolves in hydrochloric acid to form hydrogen gas and zinc chloride. 5 Explain why the reaction that takes place when copper carbonate is heated is called a decomposition reaction.

THinK 3 What is the only real proof that a chemical reaction has taken place? Explain your answer. 4 Write word equations that describe the following chemical reactions. (a) Octane gas is burned with oxygen in a car engine to

cREATE 6 Some experiments with chemical reactions can be dangerous. construct a safety poster for one of the experiments you have done. work sheet

12.2 Describing chemical changes

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12.3

Faster and slower Not all reactions occur at the same rate. The explosive reaction between hydrogen and oxygen to form water is very fast and can release enough energy to propel spacecraft into orbit. Other reactions, such as the rusting of iron, can take weeks, months or even years to be complete.

InveStIgatIon 12.7 The effect of temperature on a reaction You will need: safety glasses heatproof mat Bunsen burner matches marble chips test tube test-tube rack test-tube holder dropping bottle of 1M hydrochloric acid ◗ Carefully slide one or two marble chips to the bottom

of the test tube. ◗ Add the hydrochloric acid to half-fill the test tube. ◗ Observe the reaction. ◗ Now gently heat the test tube and observe the

reaction.

Discussion

Explosions are fast chemical reactions.

Sometimes it is important for the rate of a particular reaction to be either slowed down or made much faster than it would normally occur. There are a number of ways in which we can alter the rate of a chemical reaction.

changing the temperature You ll remember from our studies of the particle model on pages 43 7 that adding energy in the form of heat causes the particles in a substance to move faster and to collide with each other more often. When particles collide, the bonds between atoms may break and new bonds may form. As the added heat increases the number of collisions, the breaking and

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1

Has a chemical change occurred? What evidence have you observed?

2

What effect did heat have on the rate of this reaction?

3

In this reaction, the calcium carbonate, which makes up the marble chip, reacts with the hydrochloric acid to form calcium chloride, water and carbon dioxide gas. Write a word equation for this chemical reaction.

creation of bonds occurs faster. In other words, the chemical reaction between substances occurs much faster if you heat them. Of course, this works the other way as well; cooling the substances involved in a chemical reaction reduces the reaction rate. We make use of this fact when we store food in the refrigerator, rather than leaving it on the kitchen bench. Food goes off when microorganisms produce chemical substances that degrade the food. Food in the fridge is much cooler than on the bench, and this reduces the rate at which the micro-organisms produce degrading substances.

changing the surface area Have you ever had a composite resin filling in your tooth? The dentist uses blue light or ultraviolet (uV) radiation to set this type of filling. The visible or uV light speeds up the reactions that cause the materials in the filling to harden. Without the uV light, you would be waiting for hours for this type of filling to set.

UV light can speed up the setting of a composite resin filling.

Have you ever noticed that sugar in granular form dissolves much faster than a sugar cube when you add it to a cup of tea? When you break up a substance into smaller pieces, you increase the surface area of that substance. This means that more particles can immediately come into contact with the particles of another substance, allowing reactions between them to happen much faster. Bath bombs, for example, are sold as solid balls that are dropped into your bath water to release carbon dioxide gas and scented oil. As the water reacts with the Epsom salts in the bath bomb, it slowly disappears. However, if you crush the bath bomb into a powder and then put it in your bath, it reacts very quickly.

using a catalyst Catalysts are chemicals that speed up chemical reactions. They are not reactants because they are not changed by the reaction. For example, catalytic converters in car exhausts use a precious metal, such as platinum, as a catalyst. This enables nitrogen oxide to react with toxic gases, such as carbon monoxide, to form less the harmful carbon dioxide and nitrogen gases; this reaction would not occur in the absence of platinum. This reaction can be shown as: carbon monoxide + nitrogen oxide

platinum

carbon dioxide + nitrogen

Catalysts produced by living organisms are called enzymes. Many of the chemical reactions taking place inside your body involve enzymes. Enzymes are also responsible for some of the changes we see in our food. If you have ever left a half-eaten apple in your lunch box or locker, you ve seen enzymes at work. Apples and other fruits go brown because chemicals in them, called phenolics, react with oxygen in the air. The brown chemicals produced are called quinones. Enzymes speed up the reaction. The chemical word equation for this reaction is: phenolics + oxygen

Apples go brown when phenolics react with oxygen in the air.

enzymes

quinones

The human body produces many different enzymes to speed up the digestion of our food. Amylase helps us digest starches, protease is needed for protein digestion, and lipase must be present if we are to digest fats and oils.

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changing the concentration The concentration of a solution depends on how much solute is dissolved in a set amount of solvent. The more solute that is dissolved, the greater the concentration of the solution is. The more concentrated that a solution is, the more particles of solute it contains that can react with other substances. If there are more particles available for a chemical reaction, the reaction will occur faster. So, use more concentrated solutions to make a reaction go faster, and use more dilute solutions to make a reaction go more slowly.

activities REMEMBER 1 Define the rate of a chemical reaction . 2 Describe four different methods of changing the rate of a reaction. 3 Explain how heating increases the rate of a reaction. 4 Define the term catalyst . 5 Explain why a catalyst is not considered a reactant. 6 compare enzymes and catalysts.

◗ Discuss with your partner how

InveStIgatIon 12.8 changing the reaction rate You will need: safety glasses heatproof mat test tubes and test-tube rack white chalk mortar and pestle spatula 0.5M hydrochloric acid 1M hydrochloric acid measuring cylinder ◗ Hydrochloric acid reacts with

chalk to produce carbon dioxide gas, water and calcium chloride. ◗ Put a small amount of chalk

in a test tube and add enough hydrochloric acid to cover it. Observe the chemical reaction.

inVEsTiGATE 11 Amylase, pepsin and lipase are all enzymes found in the human digestive system. (a) investigate how they are involved in digestion. (b) Write a chemical word equation for the reactions that they speed up.

usE DATA 12 In an experiment investigating how temperature affects the reaction rate of an unknown metal in acid, students collected the following data.

THinK 7 Does a refrigerator stop food from rotting or does it just slow the rotting? Explain your answer. 8 Food keeps well in a refrigerator. Deduce why it keeps even longer in the freezer. 9 Propose why some washing powders contain enzymes. 10 Deduce why the word enzyme appears over the arrow in the chemical word equation for the browning of fruit.

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Temperature ( C)

Reaction time (seconds)

10

60

20

53

30

48

40

44

50

40

60

35

70

30

80

24

90

18

you could use this reaction to demonstrate one of the following hypotheses. (a) Increasing the concentration or amount of reactants speeds up a chemical reaction. (b) Increasing the surface area of reactants speeds up a chemical reaction. (c) Decreasing the concentration or amount of reactants slows a chemical reaction. ◗ Design your experiment and write

down the method that you have chosen. ◗ Predict the results you would

expect to obtain that would support the hypothesis you have chosen. ◗ Perform the experiment. ◗ Prepare a report of your findings.

(a) construct a line graph that shows how increasing the temperature affected the reaction rate. Put temperature on the horizontal axis and time on the vertical axis. (b) Predict how long the reaction would take if the temperature was: (i) 65 C (ii) 95 C. (c) Describe the shape of the graph. (d) Propose a change to the experiment that would cause the reaction to occur faster. eBook plus

13 Change the temperature, concentration and surface area in the Reaction rates interactivity in your eBookPLUS to see how they affect the rate of a reaction; then decide how the rates of particular reactions could be changed. int-0230 work sheet

12.3 Speeding up reactions

12.4

Rusting is a chemical reaction The Sydney Harbour Bridge is continually painted to protect it from moisture and the air, which would cause its steel girders to rust.

Rusting is an example of corrosion. Corrosion is a chemical reaction between a metal and substances in the air or water around it that eats away the metal and causes it to deteriorate. There are many examples of corrosion: silver tarnish; the green film that forms on copper or brass objects; and, the most common one, the rusting of iron. Corrosion causes enormous damage to buildings, bridges, ships, railway tracks and cars.

Rust Rust is the product of the corrosion of iron. Iron reacts with water and oxygen in the air to form iron oxide and other iron compounds that make up the familiar red-brown substance known as rust. Rusting is a chemical reaction that can be represented by the following word equation: iron + water + oxygen

rust

Even strong buildings and bridges that are made from steel, an alloy of iron, are weakened by rusting. The Sydney Harbour Bridge, for example, is continually painted to protect it from moisture and the air, which would cause its steel girders to rust. Ships and cars are also constructed largely of steel. Despite the strength of the steel, they need to be protected from the corrosive effects of the environment.

InveStIgatIon 12.9 observing rusting Steel wool is made from iron. You can observe rusting of the iron in steel wool by performing the following experiment. You will need: glass Petri dish water steel wool (without any soap) small glass permanent marker ◗ Pour some water into the Petri

dish. ◗ Place the steel wool in the

middle of the Petri dish. ◗ Cover the steel wool by placing

the glass over it upside-down. ◗ Mark the level of the water on

the outside of the glass with a permanent marker. ◗ Leave for several days, adding

water as required to keep the level at the mark on the glass. Steel wool

Glass

Petri dish

Water

speeding up rusting Some substances in the environment make the rusting reaction happen much more quickly. One of the most effective of these is salt. Steel dinghies that are used in the ocean rust much faster than those that are used only in fresh water. This is because the salt in the water allows the reaction between the oxygen in the air and the iron in the steel to occur much faster. Some chemicals released from factories may not be corrosive themselves but may allow the rusting process to occur faster. Even the exhaust from aircraft can speed up rusting. Research by the CSIRO has found that corrosion rates in a large city are highest near airports, industrial plants, sewage treatment works and large bodies of salt water. Rusting is much slower in very dry environments such as deserts. In the Mohave Desert in southern California, hundreds of aircraft that are not in immediate use by airlines are stored in the open air. Due to the extremely low humidity the rainfall is nearly zero rusting occurs extremely slowly. As a result, some of the aircraft are still structurally sound despite being exposed for nearly twenty years!

Observing the rusting of iron ◗ Construct a table in which you

can record your observations over several days.

Discussion 1

What did you observe about the level of water inside the glass? Can you explain why this happened?

2

Write a word equation for the chemical reaction that occurred inside the glass.

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Rust protection The layer of rust that forms on an iron object flakes off the metal, allowing air and moisture to get through to the iron below. This causes more rusting to occur, and eventually the iron becomes a heap of rust. It is important to protect

InveStIgatIon 12.10 Rusting and salt water You will need: test tubes and test-tube rack measuring cylinder iron nails water salt (sodium chloride) ◗ Design an experiment to test

the effect of the saltiness of water on the time taken for an iron nail to rust. ◗ Discuss your design with

a partner. You will need to consider which conditions must be kept the same and which condition will be varied. ◗ You will also need to set up a

control test tube. Find out the purpose of a control. ◗ Write down your method. It

should be clear enough for someone else to follow without any help. ◗ Construct a table in which to

record your observations over the next few days.

iron and steel from corrosion, especially if it is part of a bridge or the hull of a ship. There are several ways to protect iron and steel from rusting. One way is to prevent oxygen or moisture from contacting the metal. This is called surface protection. The metal can be protected by coating it with paint, plastic or oil. If the surface protection becomes scratched or worn off, the metal below can be attacked by moisture and oxygen and rusting will occur. Examine the painted surface of an old car. Wherever the paint has chipped off you will find that corrosion has occurred and the rust can be seen. Another way to protect iron from rusting is to coat it with a layer of zinc. This is called galvanising. Zinc is a more reactive metal than iron, and in the presence of moisture and oxygen the zinc layer corrodes, leaving

activities REMEMBER 1 Define the term corrosion . 2 Define the term rusting . 3 Describe what surface protection is. 4 Explain what galvanised iron is and what advantage it has over iron.

THinK Discussion What effect did salt have on the time taken for the iron nail to rust?

2

How do your results compare with those of others in your class?

6 Discuss how galvanising can protect iron from rusting when the zinc coating corrodes more quickly than the iron.

Write a report on your findings.

inVEsTiGATE

Suggest why people who live in seaside resorts have problems with their cars rusting.

7 Do other metals corrode as iron does? Design an experiment to find the answer to this question using strips of copper, magnesium,

3 4

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5 Explain why rusting occurs faster near Botany Bay than in areas further away from the sea.

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Core Science | Stage 4 Complete course

the iron unaffected. Many roofing materials and garden sheds are made from galvanised iron. You can also buy galvanised nails.

Rusting can be useful Not all rusting is bad. You can buy, from a pharmacy, hand warmers, which are commonly used by skiers and campers. These packages produce heat when you shake them. The contents of the packet include powdered iron, water, salt and sawdust. When the packet is shaken vigorously, the iron undergoes a rusting reaction, which produces heat.

city councils face problems caused by the action of dogs on metal lampposts. The corrosive properties of the dogs urine rusts the steel of the lampposts a few centimetres above the ground.

zinc, lead and aluminium. Use sandpaper to remove any coating caused by corrosion from the metal strips; they should be shiny. 8 Corrosion is found in many places. Survey your school for rust spots. Account for your findings. 9 If you have access to an old car, survey it carefully and record all the rust spots on the car. Explain why some parts of the car are more likely to rust. 10 Aluminium corrodes quite quickly, yet it is used to make soft-drink cans. investigate why aluminium cans are not corroded by the drinks they store. eBook plus

11 Use the How rust works weblink in your eBookPLUS to watch a video about rust and the corrosion of iron. work sheet

12.4 Rusting

12.5

Burning is a chemical reaction Burning is a chemical reaction. It involves the combination of oxygen with a fuel and usually produces heat and gases. Reactions that involve combination with oxygen are called oxidation reactions. There are many other oxidation reactions that can occur. The rusting of iron to form iron oxide is an oxidation reaction. Rusting could correctly be described as a very slow type of burning reaction.

Burning fossil fuels When a fossil fuel reacts with oxygen, heat is produced, along with carbon dioxide and water vapour. Fossil fuels are those fuels that are formed from the remains of living things. Petrol, natural gas and coal are fossil fuels.

the piston, which turns the drive shaft. The products of the reaction, carbon dioxide and water vapour, leave the car engine through the exhaust pipe.

InveStIgatIon 12.11 Burning magnesium You will need: safety glasses Bunsen burner, heatproof mat and matches tongs 2 cm piece of magnesium ribbon sandpaper ◗ If the magnesium ribbon is dull,

use sandpaper to remove the dull layer. ◗ Hold the magnesium ribbon

An oxyacetylene torch is used in construction work.

The oxyacetylene torch

A backdraught occurs when a fire in a closed room dies down because it has been starved of oxygen, but flammable gases continue to stream out of the hot materials in the room. When a door to the room is opened, air is quickly drawn inside, restoring the supply of oxygen and allowing the fire to reignite. The resulting fire consumes all the flammable gases in a few seconds and produces sufficient heat to ignite any remaining materials in the room. This is very dangerous to firefighters.

with tongs in the Bunsen burner flame. CAUTION Do not look directly at the flame eye damage may occur. ◗ After burning the magnesium

metal, observe the product of burning that is left.

To obtain temperatures as high as 3000 C hot enough to melt iron and weld metals acetylene fuel is mixed with pure oxygen in an oxyacetylene torch.

1

acetylene + oxygen carbon dioxide + water

Describe the magnesium metal before burning.

2

During burning, the magnesium reacted with the oxygen in the air by combining with it to form magnesium oxide. Describe the magnesium oxide.

3

How do you know that a chemical reaction has taken place?

4

Write a word equation for the chemical reaction.

Discussion

The car engine Burning is also known as combustion. Car engines work by the combustion of petrol or gas in the cylinders. A mixture of air and fuel is drawn into each cylinder and ignited by a spark from the spark plug. The fuel reacts rapidly with oxygen in the air. The resulting explosion pushes

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InveStIgatIon 12.12 Burning paper You will need: safety glasses Bunsen burner, heatproof mat and matches tongs gas jar limewater paper deflagrating spoon ◗ Pour 10 mL limewater into the gas jar. ◗ Put a ball of scrunched-up paper into the deflagrating spoon. ◗ Light the paper and lower it into the gas jar. ◗ When burning has stopped, remove the deflagrating spoon and cover the jar. ◗ Shake the gas jar and observe the colour of the limewater.

Discussion

Oxidation reactions provide the thrust to launch a space shuttle.

1

What happened to the limewater?

2

What gas was given off by the burning paper?

activities REMEMBER

Rocket fuels

1 Define the term burning .

Liquid and solid fuels are used in the NASA space shuttle program. When these fuels are burned, they provide sufficient thrust to launch a space shuttle into orbit hundreds of kilometres from Earth. Liquid hydrogen and liquid oxygen react to power the shuttle s main engines. hydrogen + oxygen

water

Most of the thrust required to launch the shuttle into orbit comes from chemical reactions in the solid fuel, which is located in the solid rocket boosters. In space, liquid fuel such as hydrazine is oxidised to produce an enormous volume of gas. As the gas is released, the rocket is thrust forwards. By controlling the direction of the thrust, it is possible to steer the rocket.

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2 Explain what evidence there is that burning is a chemical reaction. 3 Define the term fossil fuel . List three examples of fossil fuels. 4 List and describe three examples of useful oxidation reactions. 5 Write a word equation for each of the examples in question 4. 6 Is rusting an example of burning? Explain.

THinK 7 Complete this word equation. fuel + _____________ _____________ + water vapour

8 Name at least one fuel that is not a fossil fuel. 9 Recall the three different oneword names given to the chemical reactions in which fuels react with oxygen.

cREATE 10 Choose one fuel from the list below and construct a poster on the use of this particular fuel. Include in your poster where it comes from, what it is used for and a word equation for its oxidation reaction. methane ethanol butane propane kerosene lignite diesel acetylene 11 Fire extinguishers are used to fight fires. One type of fire extinguisher, the soda acid type, is commonly found in public buildings. When this fire extinguisher is turned upside down, a chemical reaction takes place inside the fire extinguisher to produce the liquid that spurts out of the nozzle. investigate what is inside the soda acid fire extinguisher and explain how it works. construct a poster on how this fire extinguisher works. work sheet

12.5 Combustion

12.6

acids and bases Acids and bases are two groups of chemicals that affect you every day. In your stomach, acids help to digest your food, and, in your mouth, bacteria produce acids that can destroy the enamel of your teeth. Most cleaning agents, including soap, are bases that can dissolve oil and grease from surfaces. In industry, acids are used to produce a wide range of products including drugs, explosives, fertilisers and plastics. The products shown in the photographs below are examples of acids and bases that can be found around the home.

sour and bitter Many of the foods you eat contain acids. Tomatoes, citrus fruits, vinegar and lemonade are all acidic. Acids have a sour taste; in fact, the name acid comes from the Latin word acidus meaning sour. Some acids, like the acid found in car batteries (sulfuric acid), are very corrosive. They react with solid substances, eating them away. Bases have a bitter taste and feel slippery or soapy to touch. Some bases are very corrosive, especially caustic soda (sodium hydroxide). Caustic soda breaks down fat, hair and vegetable matter and is the main ingredient in drain cleaners. Other bases are used in soap, shampoo, toothpaste, dishwashing liquid and cloudy ammonia as cleaning agents. Bases that can be dissolved in water are called alkalis. Some common acids and bases are listed in the tables below. Acid base indicators are substances that can be used to tell whether a substance is an acid or a base. Some common indicators are listed in the table on the next page. Acid base indicators react with acids and bases and produce different colours in each. Some of them are natural dyes, while others are artificially made. Common acids and bases Acid

Uses

Hydrochloric acid

• • • •

To clean the surface of iron during its manufacture Food processing The manufacture of other chemicals Oil recovery

Nitric acid

• The manufacture of fertilisers, dyes, drugs and explosives

Sulfuric acid

• The manufacture of fertilisers, plastics, paints, drugs, detergents and paper • Petroleum refining and metallurgy

Citric acid

• Present in citrus fruits such as oranges and lemons • Used in the food industry and the manufacture of some pharmaceuticals

Carbonic acid

• Formed when carbon dioxide gas dissolves in water • Present in fizzy drinks

Acetic acid

• Found in vinegar • The production of other chemicals, including aspirin

Base

Some common acids and bases are found around the home.

Uses

Sodium hydroxide (caustic soda)

• The manufacture of soap • As a cleaning agent

Ammonia

• The manufacture of fertilisers • As a cleaning agent

Sodium bicarbonate

• To make cakes rise when they cook

12 Chemical reactions

325

Indicators and their colours in acids and bases Indicator

Colour in acid

Colour in base

Methyl orange

Orange

Yellow

Litmus (made from lichens)

Red

Blue

Bromothymol blue

Yellow

Bluish-purple

Phenolphthalein

Colourless

Pink

Red wine

Red

Green

Red cabbage juice

Red

Yellow

indicators and it changes colour as the strength of an acid or base changes. The colour range of universal indicator is shown below.

pH

1 3

12

14

An unusual indicator coccus

The colour range of universal indicator. It is pink in strong acid (pH 1), blue in strong base (pH 14) and green in neutral solutions (pH 7).

6

9

8

Dactylopius

5

pH wheel showing the colour range of the universal indicator

10

Measuring pH You can describe how acidic or basic a substance is by using the numbers on the pH scale. The pH scale ranges from 0 to 14. Low pH numbers (less than pH 7) mean that substances are acidic. High pH numbers (more than pH 7) mean that substances are basic. If a substance has a pH of 7 it is said to be neutral neither acidic nor basic. This is shown on the pH scale below. Acids and bases can be graded from strong to weak. For example, a strong acid has a very low pH (pH 0 or 1) and a strong base has a very high pH (pH 13 or 14). pH can be measured using a pH meter or a special indicator called universal indicator. Universal indicator is a mixture of

cochineal is a red dye made from the dried and ground-up bodies of female scale insects (Dactylopius coccus). These insects live on cactus plants in Mexico. cochineal is used as a food colouring but is also an acid base indicator.

7

bicarbonate of soda

Holbrook's Vinegar

BIG

M

Sea water

Co

lg

MILK

MR

MUSCLE

Jif

at

e

OVEN SPRAY

Black coffee 1M HYDROCHLORIC ACID

0 1 STRONG ACID

Gastric juices

2

3

4

5 WEA ACID

The pH values of some common substances

326

BRASSO

PURE WATER

Core Science | Stage 4 Complete course

6

7 NEUTRAL

pH

8

9 10 WEA BASE

AJAX 11

C LO U DY A M M ON I A

12

CAUSTIC SODA

13 14 STRONG BASE

When your stomach rumbles Have you ever had indigestion? Do you burp? Does your stomach rumble? These things happen as a result of the chemical reactions in your stomach. Your stomach contains hydrochloric acid, which helps food digestion. However, if it becomes too acidic you may experience a burning feeling. This is called indigestion. The treatment for indigestion is to take an antacid powder or tablet. An antacid contains a base, which neutralises the excess acid in the stomach and relieves the pain. As in all neutralisation reactions, a salt and water are produced. One commonly used antacid is milk of magnesia. It consists of a solid base, magnesium oxide suspended in water. The base reacts with the hydrochloric acid in your stomach. The word equation for this chemical reaction is: magnesium hydrochloric oxide + acid base

magnesium chloride + water

acid

salt

The products are the salt, magnesium chloride, and water.

activities REMEMBER 1 Recall at least three uses of acids and three uses of bases. 2 How can acids be distinguished from bases? 3 compare the common properties of some acids and bases. 4 Describe the difference between a base and an alkali. 5 Recall which acid or base is used: (a) to make cakes rise (b) in fizzy drinks (c) in drain cleaners (d) in vinegar (e) in cleaning agents (f) in car batteries. 6 Define the term acid base indicator . 7 Explain how antacids relieve indigestion. 8 Explain what causes the burning sensation in your stomach when you have indigestion.

InveStIgatIon 12.13 Antacids You will need: safety glasses heatproof mat 100 mL conical flask universal indicator 0.05M hydrochloric acid solution spatula antacid powder (e.g. Eno salts or Mylanta) ◗ Pour some hydrochloric acid into the conical flask. ◗ Add 2 or 3 drops of universal indicator. ◗ Note the colour of the solution, and determine its pH. ◗ The acid in the conical flask represents the stomach

fluids. ◗ Add a spatula of antacid powder to the conical flask

and gently swirl the flask. ◗ Observe the reaction and note the colour of the

solution and the pH.

Discussion 1

What happened to the pH of the solution when the antacid was added?

2

Was the level of acidity reduced by the antacid?

9 Recall which type of substance has a pH value: (a) less than 7 (b) more than 7 (c) equal to 7.

(b) vinegar (c) pure water (d) a strong base. Substance

A

B

C

D

E

pH value

6.0 12.0 3.0 7.0 8.0

THinK 10 When you take antacid tablets for an upset stomach, does the pH of your stomach contents increase or decrease? Explain your answer.

cREATE 11 Design and construct a hazard warning label for a: (a) bottle of concentrated hydrochloric acid (b) car battery (c) bottle of drain cleaner that contains mainly caustic soda.

13 Which two of the substances in question 12 would you expect to be the most corrosive? Justify your answer. 14 construct a bar graph to display the pH values of the five substances in question 12.

inVEsTiGATE 15 investigate what a peptic ulcer is, how it is caused and how it can be treated. eBook plus

usE DATA 12 A pH meter was used to measure the pH of five different substances, and the results are shown in the table below. identify which substance could be: (a) a weak base

16 Play the pH rainbow in your eBookPLUS and drop liquids in their correct position on the pH scale. int-0101 work sheet

12.6 Acids and bases

12 Chemical reactions

327

12.7

PREscRiBED Focus AREA current issues, research and development

acid rain Every year, acid rain causes hundreds of millions of dollars worth of damage to buildings and statues. The photographs below show the damage that has been caused to a statue over sixty years. Forests, crops and lakes are also affected by acid rain blown in from industrial areas.

What causes acid rain?

eLesson Rain is normally slightly acidic. The rain is burning! As clouds form and rain falls, the See some of the destruction that acid water reacts with carbon dioxide in rain has caused on Earth. Learn why acid rain is created and how we can the atmosphere to form very weak stop it from occurring. carbonic acid. If concentrations of eles-0065 sulfur dioxide and nitrogen oxide are high, these gases react with the water in the atmosphere to produce sulfuric, nitric and other acids. When rain falls, it is far more acidic than it would normally be and is known as acid rain. If the acid rain falls as snow, acid snow can build up on mountains. When this snow melts, huge amounts of acid are released in a short time. eBook plus

Where do the gases come from? Most of the gases that cause acid rain come from the burning of fossil fuels (natural gas, oil and coal) in industry, power stations, the home and cars. North America and Europe have a greater problem with acid rain because they use coal with a higher sulfur content than Australian coal. The sulfur dioxide released by volcanoes also contributes to acid rain.

react with water in the atmosphere. Acidic gases

Acid rain

kills trees. trees

washes minerals from soil into streams

These photographs were taken in 1908 (top) and in 1969 (bottom). You can see the damaging effects of acid rain on this statue.

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acidifies lakes and streams, and kills fish, plants and other life in water. Acid rain is formed when acidic gases (sulfur dioxide and nitrogen oxides) pollute the air and react with water.

Damage caused by acid rain

solving the problem

Acid rain damages the cells on the surface of leaves and affects the flow of water through plants. It also makes plants more likely to be damaged by frosts, fungi and diseases. Acid rain collects in streams, rivers and lakes, making the waterways more acidic. A healthy lake has a pH of about 6.5 and fish, plants and insects can live in it. Acid rain causes the pH of the lake to fall. Some aquatic plants and animals cannot tolerate these acidic conditions and die. It is not only the acidic water that can kill the aquatic life. Acid rain reacts with soil, releasing minerals, which may contain elements such as aluminium. The aluminium is washed into the streams, rivers and lakes and poisons the aquatic plants and animals. When acid rain eats into buildings and statues, it is reacting with calcium carbonate in the marble or limestone.

The problem of acid rain and all the damage that it causes can be solved only by reducing the release of acidic gases into the air. Some ways of doing this include: • looking for alternative ways of producing electricity • encouraging people to use public transport or to car pool.

calcium carbonate + acid rain gypsum + water + carbon dioxide

The gypsum formed by acid rain on a statue is a powdery dust (calcium sulfate), which is washed away by the rain. As this chemical reaction continues, the statue is slowly eaten away.

InveStIgatIon 12.14 investigating acid rain Design and carry out an experiment to investigate the effect of acid rain on the growth of plants. You will need: empty milk cartons potting soil distilled water vinegar (or 0.1M hydrochloric acid solution) measuring cylinder seeds (such as lucerne, peas, cress, beans) universal indicator ◗ Cut the milk cartons so that they are about 10 cm

high. These will make suitable containers for growing the seeds, five seeds per container.

activities REMEMBER 1 Define the term acid rain , and explain how it is caused. 2 Explain why rain is slightly acidic even without air pollution. 3 Describe two different ways in which acid rain can harm the plants and animals in streams and lakes. 4 Complete this word equation. acid rain + calcium carbonate

___________

THinK 5 Motor vehicles make a large contribution to the acid rain problem. Most of them use fuel that releases acidic nitrogen oxides when it is burned. Write an account that discusses how motor vehicle pollution could be reduced over the next thirty years.

cREATE 6 Write a newspaper article that analyses the devastation caused by acid rain. 7 construct a wall chart that explains how acid rain is formed in our environment and the damage that it can cause.

iMAGinE 8 Imagine that you live near a factory or power station that is producing acidic gases and causing harm to the environment. You wish to be elected to the local government board to stop this problem. Write a speech that you could give at an election meeting that clarifies the issue.

◗ Test the effect of water with different pH values on

the growth of the seeds. To ensure that your tests are fair, you will need to keep everything the same in your experiment, except the one thing that you are varying. In this case you are varying the acidity (pH) of the water that you are putting on the plants. ◗ Prepare a report on your investigation. This could

be a written report, a video, a wall chart or an oral presentation.

inVEsTiGATE 9 Use the library to investigate which countries are most affected by acid rain. 10 investigate how damage caused by acid rain could be stopped or at least reduced. work sheet

12.7 Acid rain

12 Chemical reactions

329

LooKIng BaCK 1 Identify each of the following as either a chemical or a physical change. (a) The wax on a burning candle melts. (b) The wax vapour at the top of the candle wick burns with oxygen to produce carbon dioxide, water vapour and heat. (c) Calcium carbonate is dissolved by hydrochloric acid to form calcium chloride, water and carbon dioxide gas. (d) Hydrogen gas explodes with oxygen gas to form water.

11 Some chemicals react as soon as they come into contact with each other. Others need a trigger to get them started. Identify two things that can trigger a combustion reaction. 12 The setting of concrete is a chemical reaction that takes place between concrete and water. It is a very slow reaction. Give at least two reasons why scientists may be asked to find ways to speed up the reaction.

2 Write word equations for each of the chemical changes in question 1. 3 Explain how you know that: (a) toasting bread is not a physical change (b) rusting of a nail is not a physical change. 4 Some chemical reactions can be useful. Recall three examples of useful chemical reactions. 5 Catalysts are sometimes added to the reactants taking part in a chemical reaction. (a) Define the term catalyst . (b) When a word equation is written to describe a chemical reaction, catalysts are not included as either reactants or products. Explain why. 6 Rusting is an example of a slow chemical reaction. (a) Recall the three reactants of rusting. (b) Identify the product of the rusting reaction.

(a)

(b)

7 For each of the following reactions, propose methods to make the reaction happen more quickly. (a) Burning a pile of dry leaves (b) Cooking potatoes (c) Dissolving marble chips in acid (d) Removing a stain using bleach (e) Making an iron nail go rusty (f) Letting milk go sour 8 Just as chemicals can be grouped or classified, so can chemical reactions. Recall the names given to the following two groups of chemical reactions. (a) Reactions of metals with oxygen (b) Reactions of acids with bases 9 Imagine that you are given a safe, but unknown, liquid and are asked to decide if it is an acid, a base or neutral. You are provided with an acid base indicator that is safe to use, but it does not have a label on it. You don t know what the colour changes to the indicator mean. Outline a step-by-step procedure to describe how you could find out whether the substance is an acid, a base or neutral. You are permitted to use common substances found in just about any kitchen. 10 Each of the four photographs at right (a, b, c, d) shows a chemical reaction taking place. Compare these chemical reactions.

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Core Science | Stage 4 Complete course

(c) (d)

13 The oxyacetylene torch shown here is used to melt metals to allow them to be joined together.

4 Consider this word equation for a chemical reaction: magnesium + hydrochloric acid magnesium chloride + hydrogen gas The reactants in this equation are A magnesium and hydrogen gas. B magnesium chloride and hydrogen gas. C magnesium and hydrochloric acid. D magnesium, hydrochloric acid, magnesium chloride and hydrogen gas.

(a) Identify what type of chemical reaction takes place in the oxyacetylene torch. (b) What evidence is there in the photo that may help you justify your answer to part (a)? 14 Many dentists believe that the increase in cavities in young adults is due to the increased consumption of soft drinks at a younger age. They theorise that a chemical reaction takes place between the tooth enamel and the acid in the soft drink. (a) Recall what acid is found in soft drinks. (b) Design an experiment that will allow you to investigate the effects of the soft-drink acid on teeth. (Hint: Find out what material(s) teeth are made from.) 15 (a) Explain why children s steel swing sets rust much faster in Lennox Heads than those in Dubbo. (b) Suggest two ways in which the rusting of the steel swing sets can be prevented (or at least slowed down).

TEsT YouRsELF 1 Which one of the following would you describe as a chemical change? A Ice-cream melting in the sun B A match burning C Breaking an egg D Boiling water for a cup of tea (1 mark) 2 Which of the following is not a reaction with oxygen as one of the reactants? A Combustion B Oxidation C Rusting D Neutralisation (1 mark) 3 Which substance is used to coat iron in the process of galvanisation? A Gallium B Zinc C Paint D Salt (1 mark)

(1 mark)

5 Have you ever noticed how things made of silver, such as expensive cutlery, old tea services and even jewellery, get a black film over them if they are not used often? That black film, called silver tarnish, is a form of corrosion that occurs when sulfur in the air reacts with the silver metal forming a blackish layer of silver sulfide. You can see the same thing happening much faster if you use a silver teaspoon to eat an egg at breakfast the sulfur from the egg yolk comes into direct contact with the silver and tarnish forms on the teaspoon in a matter of minutes. The good thing is that you can use a bit of knowledge about chemical reactions to remove the tarnish. One of the easier methods of cleaning tarnished silver is to wrap a sheet of aluminium foil loosely around the object and then place it in a tub of warm water that has had bicarbonate of soda (sodium bicarbonate) dissolved in it. It is important that the aluminium foil is completely covered by the warm water and that the warm water can get inside the foil. Over time, aluminium from the foil reacts with the silver sulfide of the tarnish to form aluminium sulfide and silver (which remains on your object). silver sulfide + aluminium

aluminium sulfide + silver

This reaction can take anywhere between a few minutes to a few hours depending on the size of your silver object and how much tarnish there is to remove. When the tarnish has all gone, the silver object is rinsed in clean water to remove any aluminium sulfide. (a) Explain why hot water rather than cold water is used in this method of cleaning silver. Use your knowledge of particle theory to support your answer. (1 mark) (b) Draw a labelled scientific diagram of the set-up for cleaning silver. (1 mark) (c) Does this method work if you use copper foil rather than aluminium foil? Design an experiment that will allow you to find out. (2 marks) (d) This method normally takes a few hours to work. Describe at least two methods you could use to make this process happen faster. Use examples you have encountered in your study so far to justify why you think these methods would work. (2 marks) work sheets

12.8 Chemical reactions puzzles 12.9 Chemical reactions summary

12 Chemical reactions

331

StUDY CHeCKLISt chemical changes

ICt eBook plus

■ recall the physical changes that matter may undergo

12.1

■ compare a chemical change with a physical change 12.1 ■ define the term chemical reaction 12.2 ■ describe how you can tell if a chemical reaction has occurred 12.2 ■ construct word equations to describe chemical reactions 12.2

SUMMaRY

eLessons The rain is burning In this video lesson, you will discover the cause of acid rain and learn about the damage it can do to buildings, plants and waterways. This problem is increasing but there are practical ways to stop it. A worksheet is included to further your understanding.

Describing reactions ■ define the term precipitate 12.2 ■ distinguish between reactants and products 12.2 ■ identify the reactants and products in word equations

12.2

Reaction rates ■ define the term reaction rate 12.3 ■ describe processes that allow the rate of a chemical reaction to be changed 12.3 ■ distinguish between processes that speed up a reaction and those that slow a reaction 12.3 ■ explain why increasing temperature, surface area or concentration makes a reaction occur faster 12.3

common reactions ■ ■ ■ ■

explain the process of rusting 12.4 compare rusting and combustion 12.5 describe how rusting can be prevented or slowed 12.4 construct word equations to describe common oxidation reactions 12.5

Acids and bases ■ distinguish acids from bases 12.6 ■ describe the function of acid base indicators and give examples of these indicators

Searchlight ID: eles-0065

interactivities Reaction rates This interactivity allows you to change the temperature, concentration and surface area of reagents to see how they affect the rate of a reaction, and then decide how the rates of a number of reactions could be changed. Searchlight ID: int-0230 The pH rainbow This interactivity helps you develop your knowledge of pH by challenging you to drop different liquids in their correct position on the pH scale. Instant feedback is provided.

12.6

■ identify acids, neutral substances and bases (alkalis) according to their pH

12.6

■ explain how antacids settle a rumbling stomach 12.6 current issues, research and development ■ discuss the causes of acid rain and its effects on the environment

12.7

Searchlight ID: int-0101

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Core Science | Stage 4 Complete course

13

Plants

Plants are everywhere around us. They grow in parks and gardens, in playgrounds and bushland, and even in the oceans. They are made up of cells and have organs like us. In fact, many of the processes that occur in humans also happen in plants. There are some major differences though. Most significantly, plants do not need to eat food. Instead, they photosynthesise. Most plants are anchored to the ground. Some plants produce flowers that are involved in reproduction. Plants are not just pretty to look at, however. Our survival depends on them. Let s find out more about the world of plants and how they work.

In this chapter, students will: 13.1 ◗ describe the role of the roots and

stems of plants 13.2 ◗ learn about the conducting tissue of

plants 13.3 ◗ describe the process of

photosynthesis 13.4 ◗ investigate experiments done

by scientists to learn about photosynthesis 13.5 ◗ describe the structures and

functions of flower parts 13.6 ◗ learn about the life cycle of

flowering plants 13.7 ◗ design, carry out and report

on experiments involving seed germination or plant growth 13.8 ◗ compare the characteristics of

major groups of plants.

Plants are all around us. Some, like these, are pretty to look at, but air survival depends on the plant kingdom.

13 Plants useful plants Many useful substances are obtained from plants including medicines, ingredients for cosmetics, food and wood for furniture. The diagram at right is the start of a mind map about the use of plants as resources.

Cotton

Plants as resources

Wood

Food

Fabrics

Paper

Used to manufacture products

Complete this mind map by adding at least 10 more branches to it.

InvestIgatIon 13.1 extracting and using a plant dye You will need: calico or white cotton waterproof marker 250 mL beaker brightly coloured plant part (such as red beetroot, spinach leaf, walnut shell, onion skin, brightly coloured berries, tea leaves or coffee beans) scissors, knife or mortar and pestle hotplate or Bunsen burner, tripod and heatproof mat alum mordant strainer or gauze fabric Recipe for alum mordant (can be prepared by the teacher for the whole class): ◗ Weigh out 10 g of alum and 5 g of tartaric acid for every

100 g of fabric. ◗ Dissolve in warm water (use 250 mL water for ten groups).

Lesson 1 ◗ Cut the fabric into five pieces about 10 cm × 10 cm. Label the pieces A to E with a waterproof marker. Leave piece A untreated. Pieces B and C will be treated with alum mordant and then dyed. Pieces D and E will be dyed but not treated with alum mordant. ◗ Put pieces B and C in a 250 mL beaker. Add enough

may choose to chop it into small pieces using scissors or a knife, or you may grind it using a mortar and pestle. ◗ Add the finely divided plant part to a 250 mL beaker and

add 200 mL water. ◗ Heat gently for 30 minutes using a hotplate or Bunsen

burner. This will extract the dye from the plant material. ◗ Allow the dye to cool down until the next lesson.

Cosmetics

Medicines

Lesson 2 ◗ Filter the dye using a strainer or gauze fabric and then boil it. ◗ Remove pieces B and C from the mordant, squeeze them

dry, and then put them in the dye. ◗ Put pieces D and E in the dye as well. ◗ Allow the fabric to soak in the dye for at least 30 minutes

(or until the next lesson). ◗ Remove the pieces of fabric from the dye and allow them

to dry. Lesson 3 ◗ Rinse pieces B and D only in water and allow them to dry.

DiscussiOn 1

Why was one piece of fabric left untreated?

2

Did the plant dye change the colour of the fabric significantly? Which fabric samples do you need to compare to answer this question?

3

Is the vegetable dye colourfast ? Which fabric samples do you need to compare to answer this question?

4

The mordant is supposed to help the dye soak into the fabric and make the dye more colourfast. Was the mordant effective? How can you tell?

5

Compare your results with those of other groups. Which plant part made the most effective plant dye?

6

Which variables were controlled in this experiment?

7

In this experiment the results were qualitative. (a) What is the difference between qualitative and quantitative results? (b) Suggest a way that the results could be made quantitative.

water to just cover the fabric. Add 25 mL of alum mordant. Leave to soak until the next lesson. ◗ Depending on the type of plant part you are using, you

Chemicals extracted from plants and used as ingredients in commercial products

13.1

Plants have organs too! Plants are multicellular organisms; they are made up of more than one cell. Like other multicellular organisms, they contain organs that work together to keep them alive. The main organs of plants are the roots, stem, leaves and flowers.

Photosynthesis occurs in the leaves. Flowers are the reproductive organs of plants. They develop into fruits containing seeds.

Hairy roots and all Roots both anchor the plant and help it to obtain water from the soil. Plants obtain water and mineral salts through their roots. Root hairs found on the outermost layer of the smallest roots can greatly assist this process. These are long cells that act like thousands of tiny fingers reaching into the soil for water and soluble salts. For most plants, it is important for their roots to be in soil that is well drained. Plants need oxygen for respiration, and the uptake of mineral salts is usually reduced if the roots are waterlogged.

The stem holds up the leaves and flowers. It is also involved in transporting water from the roots to the leaves and sugars from the leaves to other parts of the plant.

Fruit

Roots anchor the plant in the ground and absorb water and minerals from the soil.

Xylem

Phloem

Root hairs Root hairs seen with an electron microscope

Main root Root hair absorbs water and minerals (arrows indicate direction of flow).

Lateral root

Root hairs

Water Root tip

Water and solutes to stem

Soil particle Xylem Root vessels cortex

Epidermis (with root hairs)

Soil

Structure of plant roots

13 Plants 335

Which minerals do plants need?

nitrogen: the gas of life

Animals get the minerals they need from the food they eat. Plants do not eat food. They make the sugars they need for energy by photosynthesis, and they absorb minerals from the soil. Some minerals, called trace elements, are needed only in tiny amounts. Others minerals are needed in larger amounts. These are shown below.

Plants need large amounts of nitrogen to produce proteins. There is plenty of nitrogen around. In fact, most of the air is nitrogen gas (78 per cent). However, plants are not able to use nitrogen gas. Nitrogen fixing changes nitrogen in the air into nitrogen compounds in the soil. Plants soak up the nitrogen compounds through their roots.

Nitrogen Nitrogen is an important part of the protein in plant cells. It also makes up part of the chlorophyll in plants. It is important for leaf growth. Plants lacking nitrogen are usually stunted and have pale green or yellow leaves.

Phosphorus Phosphorus is important for plant growth. Plants lacking phosphorus are stunted and have poor root growth. Their fruit is also small.

The main way that nitrogen is fixed is by nitrogen-fixing bacteria. Some of these bacteria live freely in the soil. But they are also found living on the root systems of plants such as clover, peas, she-oaks and wattles. Every few seasons, farmers may alternate their regular crop with a legume crop, such as clover, that has nitrogen-fixing bacteria to help increase the nitrogen content of the soil. If they don t do that, they have to use fertilisers, which can be expensive. Scientists are now trying to produce new plants with nitrogen-fixing properties. There are two other ways in which nitrogen gets into the soil: 1. Lightning causes nitrogen and oxygen to react with each other and puts nitrogen into the soil. 2. The decomposition of dead animals and plants releases nitrogen into the soil.

Calcium Calcium is important for cell growth. Lack of calcium causes poor buds and stunted growth.

Sulfur Sulfur is a part of protein in plant cells. Low sulfur levels can cause leaves to go yellow.

Potassium Potassium is also important in making chlorophyll. It makes plant cells strong and helps with water movement in cells. Lack of potassium causes weak cells. It also causes older leaves to be floppy.

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Core science | stage 4 Complete course

Magnesium Magnesium is needed to make chlorophyll. Not enough magnesium causes the plant s lower leaves to go yellow.

The white root nodules on this plant contain nitrogen-fixing bacteria.

Plants without soil Hydroponics is a way of growing plants without soil. Hydroponic systems use coarse sand, pebbles or rock-wool to support the plant s roots. The nutrients that plants usually get from the soil are supplied in a water solution. The water solution is trickled over

the roots of the plants. This allows the roots to get lots of oxygen and not become waterlogged. Vegetables such as lettuces, tomatoes and beans are sometimes grown hydroponically.

activities 10 explain why it is important to know what plants look like if they lack certain minerals.

ReMeMBeR 1 Copy and complete the table below. Organ

11 Describe what can be done to help plants suffering from a lack of minerals.

Function

Roots

tHinK anD ReasOn

Stem

Use the table below to answer the following.

Leaves Flower 2 Outline why plant roots have small hairs. 3 Recall the minerals that plants need in large amounts. 4 Recall two important chemicals in plants that include the element nitrogen. 5 Define the term nitrogen fixing . 6 Outline three different ways in which nitrogen can enter the soil.

12 (a) Propose how a gardener would use the information in the table. (b) If a plant had a nitrogen deficiency, describe the symptoms that it would show. (c) Sketch and label a plant with a phosphorus deficiency. (d) Sketch and label a plant with a potassium and magnesium deficiency.

investigate 13 Observe a number of different types of roots, using a stereomicroscope, and then record your observations as diagrams.

tHinK 7 classify the following vegetables as leaf, stem, fruit, flower or root. (a) Carrot (b) Celery stick (c) Lettuce (d) Potato (e) Beans (f) Peas (g) Artichoke (h) Capsicum (i) Cauliflower (j) Tomato (k) Broccoli (l) Onion

14 Find out what the main chemicals in fertiliser are. 15 Design an experiment to test each of the following hypotheses. (a) Bean plants that have fertiliser X added to their soil produce larger beans. (b) Rose bushes produce more flowers if fertiliser A is added to the soil they grow in. (c) Pine seedlings grow fastest if you add one capful of fertiliser B to every 500 g of potting mix.

8 At the supermarket, some lettuces are labelled hydroponic lettuce . Define what this means. 9 explain why you can kill pot plants by overwatering them, particularly if the pot does not have drainage holes.

work sheet

13.1 Roots, stems and leaves

Some symptoms of mineral deficiencies in plants Deficient mineral Plant part

Nitrogen

Potassium

Magnesium

Phosphorus

Leaves

Upper leaves pale green, lower leaves yellow

Yellow leaves with dead Upper leaves normal, spots lower leaves pale green or yellow

Small purple leaves

Stem or roots

Weak stem

No observed effect

No observed effect

Poor root growth

Fruit and flowers

No observed effect

Poor flower and fruit growth

No observed effect

No observed effect

13 Plants 337

13.2

Hold and carry Plant stems serve two important functions; they hold up the leaves and flowers, and they transport substances throughout the plant. Water must travel from the soil up to the leaves, and sugars made in the leaves need to be transported to all parts of the plant.

conducting tissue: xylem and phloem The roots, stems and leaves of plants contain conducting tissue to transport substances from one part of the plant to another. There are two types of conducting tissue: xylem and phloem. Xylem tissue carries water and minerals from the roots of plants to all other parts of the plant. It consists of long hollow tubes made up of the remains of dead cells. The cells that xylem tubes are formed from have their cell walls strengthened with a woody substance called lignin. This makes them quite sturdy.

DiscussiOn

InvestIgatIon 13.2 stem transport systems You will need: celery stick (stem and leaves) knife two 250 mL beakers water

blue food colouring red food colouring hand lens

◗ Slice the celery along the middle to about halfway up the

stem. ◗ Fill two beakers with 250 mL of water. Colour one blue

and the other red with the food colouring. ◗ Place the celery so that each side of the celery is in a

separate beaker. ◗ Leave for 24 hours and then observe the celery. ◗ Cut the celery stick across the stem. ◗ Use the hand lens to look at the inside of the stem.

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Water can move in only one direction in xylem tubes: from the roots to the leaves. There are a number of forces that keep water moving upwards. Transpiration plays an important role. Plants lose water from small holes in their leaves called stomata. Water molecules stick together slightly, so, when one water molecule comes out of a stoma, it drags the next molecule up the stem, which in turn drags the next molecule up, and so on. This is called a transpiration stream. Phloem tissue transports sugars made in the leaves to other parts of the plant. Phloem is made up of two types of cells: sieve cells and companion cells. Sieve cells, like xylem cells, arrange themselves end to end to form long tubes, but the cells that make up sieve tubes are still alive. They are called sieve cells because their cell walls have holes in them (like sieves) at each end of the cells to allow substances to move

1

Look at where the water has travelled in the celery. Draw a diagram to show your observations.

2

Draw a diagram to show what you can see when you cut across the stem.

3

Where is the differently coloured water found in the stem?

4

Where are the different colours found in the leaves?

5

Draw a diagram of the whole celery stick and trace the path of the water through each side to the leaves.

6

How could you turn a white carnation blue? Try it.

If we cut through a stem, we can see the conducting tissue of plants. The photo shows a crosssection of a plant stem under the microscope.

Xylem

from one cell to another. Sugars can move both up and down sieve tubes. The movement of sugars throughout the plant is called translocation.

Vascular bundles

Phloem Phloem

Xylem

Vascular bundles

Xylem for support The phloem and the xylem vessels are located together in groups called vascular bundles. The strong, thick walls of the xylem vessels are also important in helping to hold up and support the plant. The trunks of trees are mostly made of xylem. Did you know that the stringiness of celery is due to its xylem tissues?

activities ReMeMBeR 1 Copy and complete the table below.

Tissue

What it carries

Direction of movement

Name of cells that form tubes

Are cells that form tubes living?

Xylem Some water evaporates through the stomata; some water is used for photosynthesis.

Phloem 2 Outline why vascular bundles are important to plants.

investigate 3 Use reference books to define the terms monocotyledon and dicotyledon , and describe some of the features of each of these groups of plants. 4 examine prepared slides showing cross-sections of stems of different plants. (a) Do they all have their vascular bundles organised in a ring? (b) Find out which of the stems you observed came from dicotyledons ( dicots ) and which came from monocotyledons ( monocots ). Describe the difference in the arrangement of vascular bundles between monocot and dicot plants.

Water flows up the stem in xylem tubes.

5 investigate the relationship between wood and xylem tissue. Root hairs take up water in the soil.

6 How long do you think it would take for a plant to take up 50 mL of water? What conditions might speed it up? Propose a hypothesis, and then design an experiment to test your hypothesis. 7 Design an experiment to test the time taken for different volumes of water to be taken up by a plant.

The movement of water from roots to leaves is known as the transpiration stream.

work sheet

13.2 Plant transport highways

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13.3

Leafy exchanges Being green helps plants make their own food.

solar powered Plants are often called producers. This is because they use energy from light to make complex, energy-rich substances for food from simpler substances such as carbon dioxide and water. This process is called photosynthesis. Photosynthesis produces oxygen gas and glucose. There are small holes in the leaves called stomata (singular = stoma). These small holes allow gases such as carbon dioxide, oxygen and water vapour to move in and out of the leaf. They are located mainly on the underside of leaves. The stomata can be seen clearly under the microscope. They are surrounded by two kidney-shaped cells called guard cells. The guard cells can open or close the stomata depending on the plant s need. When the plant has plenty of water, the guard cells fill up with water and stretch lengthways. This opens the pore. If water is in short supply, the guard cells lose water and collapse towards each other to close the pore. This is one way that the plant can control its water loss.

Stomata are surrounded by guard cells on the underside of a leaf. Guard cells

Epidermal cells

Stomatal pore

Nucleus

scientists have used genetic engineering technology to produce plants that glow particular colours when they have mineral deficiencies. this provides farmers with information about which soils need extra minerals added.

Cell wall thickening

Guards cells are filled with water and the stomatal pore opens. Stomata can close to conserve water.

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Guard cells collapse and the stomatal pore closes.

Why plants are green Plants are green because they contain the green pigment chlorophyll. This pigment is found in chloroplasts inside the cells. Chlorophyll traps energy from sunlight so that it can be used in photosynthesis ( light + putting together ). The reaction for photosynthesis is shown below. carbon dioxide + water

sunlight

chlorophyll

glucose + oxygen Light energy from the sun

Plants need light to photosynthesise. In the dark, no photosynthesis occurs. Like other living things, however, plants respire and require oxygen all the time.

Leaf crosssection

Cell membrane

Water from the plant s roots

Cell wall Carbon dioxide

Vacuole Oxygen gas Nucleus Stoma Chloroplast

Single leaf cell

Chloroplasts

Leafy exchanges ◗ Try to find a pair of guard cells and

InvestIgatIon 13.3

one of the stomata.

Observing leaf epidermal cells DiscussiOn

You will need: leaf clear sticky tape microscope slide microscope

1

Is the stoma (the opening) open or closed?

2

Make a drawing of a group of cells, including the guard cells. Include as much detail in your drawing as possible.

3

Label the guard cells and stomata.

4

Title and date your drawing. Write down the magnification used.

You can make a slide of leaf epidermal cells with sticky tape. ◗ Put some sticky tape over a section

of the underside of a leaf. ◗ Press the sticky tape firmly onto the

leaf. ◗ Tear the tape off. Some of the lining

cells should come off with the sticky tape.

◗ Press the tape, sticky side down

onto a microscope slide. ◗ View the sticky tape under the

microscope.

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sugary sweet glucose

the many journeys of

Plants may use the glucose made by photosynthesis in four main ways: 1. used straight away as energy 2. stored changed into starch or oil and stored in the stems, roots, seeds and fruits 3. used to make cellulose for the cell walls

InvestIgatIon 13.4 Looking at chloroplasts under a microscope You will need: tweezers moss, spirogyra or elodea water light microscope, slides, coverslips dilute iodine solution

4. combined with minerals and used to make proteins and other substances for plant growth.

Zooming in to where the action is Using a light microscope, you may be able to see the chloroplasts within cells as small, green, roundish shapes. These are the mini-factories that use the energy from sunlight to make glucose.

◗ Put a drop of dilute iodine solution under the coverslip.

(Iodine stains starch a blue-black colour.) ◗ Using the microscope, examine the leaf again.

DiscussiOn 1

Draw what you see before staining.

2

Label any chloroplasts that are present.

3

Describe the colour of the chloroplasts before staining.

4

What gives chloroplasts their colour?

◗ Place the plant material in a drop of water on a

5

Did the iodine stain any part of the leaf a dark colour?

microscope slide and cover it with a coverslip.

6

If so, what does this suggest?

7

What conclusions can you make about chloroplasts?

◗ Using tweezers, carefully remove a leaf from a moss

or elodea plant or take a small piece of spirogyra.

◗ Use a light microscope to observe the leaf.

activities ReMeMBeR 1 Describe why plants are called producers. 2 Recall the name of the process by which plants make their own food. 3 Recall the word equation for photosynthesis. 4 explain why plants are green. 5 Use a bubble map to summarise four different ways in which plants may use the glucose made by photosynthesis.

tHinK 6 explain each of the following. (a) Leaves have a flat shape. (b) The leaves on many trees are attached to branches in such a way that the leaves do not overlap very much. (c) Rainforest plants tend to have much larger leaves than desert plants.

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7 Suggest how guard cells got their name. 8 explain why guard cells and stomata are usually found only on the lower part of the leaf, away from direct sunlight. 9 Would you expect to find chloroplasts in the cells of plant roots? explain your answer.

investigate 10 View prepared slides of leaf epidermis from different species of plants and find pictures of leaf epidermis from various plants on the internet. Do all epidermal cells have the same shape? 11 Place a plastic bag over the leaves of plants growing in the school grounds. Seal the bag and record the amount of water collected over 24 hours. What conclusions can you draw from your results? work sheets

13.3 Leafy exchanges 13.4 Photosynthesis

13.4

Investigating photosynthesis How do we know that plants need carbon dioxide, water and chlorophyll for photosynthesis? What evidence do we have that photosynthesis produces

InvestIgatIon 13.5 Out of the light You will need: pot plant that has been kept in the dark for a few days several strips of aluminium foil scissors and sticky tape hotplate 500 mL beaker of boiling water test tube of ethanol forceps iodine solution and dropping pipette Petri dish watchglass with a small sample of potato starch

oxygen and glucose? Many scientists have done experiments over many years to gradually reveal all the facts we now have about photosynthesis.

CAUTION Ethanol is flammable. Do not place it near a naked flame. Use a hotplate to heat the water.

◗ Remove the leaf from the ethanol

with the forceps and dip it into the hot water in the beaker again to remove any excess ethanol.

◗ Stand the test tube in the beaker of

hot water and leave for 10 minutes. This treatment will remove the chlorophyll.

◗ Place the leaf into a Petri dish and

cover with iodine solution. Note any colour change and where on the leaf any such change occurred.

◗ While the leaf is in the ethanol,

test a small sample of potato starch on a watchglass with the iodine solution. Note any colour change.

DiscussiOn 1

Glucose is produced during photosynthesis and is then converted to starch and stored. Did your test show any differences in starch production between the sections of leaf exposed to the light and the sections kept in the dark?

2

Which variable was investigated in this experiment?

3

Why was the plant kept in the dark for a few days before the experiment?

4

What inferences (suggested explanations) can you make from your observations?

5

What is the control in this experiment?

◗ Fix aluminium strips to one leaf of

a plant as shown in the figure on the right. Make sure that both sides of the leaf are covered by the strip and that you do not damage the leaf.

Sticky tape

Aluminium foil

◗ Leave the plant in the light for

3 days. ◗ Remove the leaf from the plant and

take off the foil. ◗ Dip the leaf into boiling water for

Make sure that the aluminium strips are secured, and that you do not damage the leaf.

10 seconds, and then place it in a test tube of ethanol.

activities tHinK anD anaLYse Use the Discovery journal of photosynthesis on the next page to answer questions 1 to 8. 1 If you bought a small plant today and watered it regularly, one

year later its mass would have increased. According to Nicholas of Cusa the increase in mass would have come from the water you gave the plant, rather than the soil. (a) Describe how you could prove that the matter in the soil had not turned into plant matter. (b) Was Nicholas of Cusa correct? Propose what actually causes

the increase in the mass of the plant. 2 Stephen Hales suggested that plants get some nourishment from the air. identify what plants actually need from the air to photosynthesise. 3 Study Priestley s experiment. (a) Propose why a candle goes out if it is placed in a sealed jar.

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Discovery journal of photosynthesis Jan Baptista van Helmont Demonstrated that most material Dutch physician in a plant’s body does not come from (1577–1644) soil; he suggested it comes from water

Nicholas of Cusa German cardinal (1401–1464)

Proposed idea that weight gained by plants is from water, not earth

Priestley’s experiment

Suggested plants get some nourishment from air

Stephen Hales British physiologist/clergyman (1677–1761)

Showed that plants could ‘restore’ air injured (by respiration)

Joseph Priestley British chemist/clergyman (1733–1804)

Showed that plants need sunlight to restore ‘injured air’ and that only the green parts do this; all parts of plants ‘injure’ air (i.e. respire)

Various European chemists (late 18th century) Oxygen discovered and identified as ‘restored’ air, carbon dioxide discovered and identified as the ‘injured’ air

Maize seedling held by the cork, with roots in the culture solution

Light

Julius von Sachs German botanist (1832–1897)

Burning candle floating on cork

Candle goes out.

Mouse with green plant survives.

Add green plant.

Later the candle can burn again.

Mouse alone dies.

Jan Ingenhousz Dutch physician (1730–1799)

Jean Senebier Swiss minister (1742–1809) Leaves in water without carbon dioxide give off no oxygen.

Demonstrated that plants use carbon dioxide dissolved in water as food

Leaves in water with carbon dioxide give off oxygen.

Oxygenenriched air

Discovered plant respiration, and that chlorophyll is found in chloroplasts; showed that starch grains form during photosynthesis, and that plants take in and use minerals from the soil; showed that minerals were required for making chlorophyll

Reflected light

Theodor Wilhelm Engelmann German physiologist (1843–1909) Showed that oxygen was produced by chloroplasts; and that red and blue light are the most important wavelengths for photosynthesis Absorbed light Transmitted light

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Chloroplast

(b) Why was Priestley able to relight the candle after the plant had been growing in the jar for some time? (c) Why does a mouse die if left in a sealed jar? (d) Why did the mouse survive if it was placed in a sealed jar containing living plants? (e) Priestley stated that plants could restore injured air . What do you think he actually meant by that? 4 Jan Ingenhousz s statement could be re-written in the following way. Plants need sunlight to produce (a) ________. Only the green parts of plants can produce (b) ________ by (c) p________. All parts of plants (d) r________.

7 Look at the diagram next to the name Julius von Sachs. identify which of the discoveries made by Von Sachs was probably made using this apparatus. 8 identify the colours of light that are absorbed best by chloroplasts. Use the diagram above to answer questions 9 to 11. 9 If you were investigating the effect of carbon dioxide concentration on photosynthesis and enclosed a plant in a plastic bag with soda lime in it, justify why you would put the control plant in a plastic bag without soda lime. 10 Starch found in a leaf is used as evidence of photosynthesis in the leaf. identify where else the starch might have come from.

5 Which gases were identified as restored air and injured air in the late eighteenth century?

11 If you were measuring the effect of light intensity, justify why would you also need a thermometer.

6 Outline what the experiment carried out by Jean Senebier revealed about photosynthesis.

12 Discuss whether photosynthesis is the reverse of aerobic respiration.

13 During a 24-hour period of day and night, identify when a plant respires and when it photosynthesises. 14 Apart from the production of food, how are plants important to life on Earth?

investigate 15 Select one of the questions about photosynthesis experiments in the diagram above. Design (and if possible perform and report on) an experiment to find the answer or more information about it. 16 Your group will be assigned one of the scientists in the Discovery journal of photosynthesis on the previous page. (a) Find out more about the experiments relating to photosynthesis carried out by that particular scientist. (b) Were this scientist s ideas accepted immediately? Which ideas did their new ideas replace?

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13.5

the sex life of plants Flowers are involved in reproduction. They contain the sex organs of plants. Some flowers contain male sex organs, some contain female sex organs and some contain both! Flowers are designed to increase the chance of pollination, the process where pollen produced by the male parts of flowers lands on the stigma of the female part of a flower.

Petals are brightly coloured to attract insects and birds. The nectary produces sweet nectar to attract insects and birds.

Petal

Nectary

Stigma

The stigma is a sticky pad that pollen lands on.

Style Anther

Filament

CARPEL (female)

The ovary protects the ovules.

STAMEN (male) Ovary

Ovule(s) Sepal

Ovules are the female sex cells. Receptacle

Sepals protect the flower bud before it opens.

The stamen is the male part of the flower that produces pollen, which contains the male sex cells.

Pollination Pollination describes the way in which pollen grains reach the stigma. Plants may pollinate themselves (self-pollination). More often, however, they obtain the pollen from the flower of a different plant of the same species (cross-pollination). Cross-pollination increases the variation among the offspring and gives them a better chance of survival. The pollen grains may be transferred to other flowers by wind, insects and other animals. Insect-pollinated flowers usually have attractive, brightly coloured petals and nectaries. The pollen grains themselves may be in a shape that makes them become easily attached to the insect. Wind-pollinated flowers are usually less conspicuous and have no large scented petals or nectar. Their shape

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Self-pollination Cross-pollination

The difference between self-pollination and cross-pollination

enables small, light pollen grains to be shaken from the plant and carried away with even the slightest gust of wind. The anthers hang outside the flower and the feathery stigmas spread out to catch airborne pollen grains.

◗ Identify and label the male and

Investigation 13.6

female parts you can see.

What s in a flower?

◗ Place the flower on the cutting

You will need: flowers sharp knife or razor blade cutting board hand lens tweezers

board and hold it with the tweezers. ◗ Carefully cut the flower in half

Cut down centre

down the middle (a vertical crosssection). ◗ Use the hand lens to look at the

ovary and eggs. ◗ Draw the cross-section and label

the female parts inside the flower. Which do you think is insect pollinated and which is wind pollinated?

Fertilisation After pollination comes fertilisation. Once the pollen lands on the stigma of a flower, pollen tubes grow down the style. The male sex cells travel down the pollen tubes all the way to the ovules inside the ovary where fertilisation occurs. Fertilisation is the fusing of a male sex cell with an ovule.

some plants are shaped in the form of the sexual partner of an insect, and the plants may secrete chemicals that excite or stimulate the insect. this may increase the contact between the insect and the plant pollen. some insects are so fooled by these plants that they attempt to mate with them. On occasions, insects even release their own sperm into the flower.

DiscussiOn ◗ Draw a

1 Which parts of the flower become the seeds?

picture of your flower. Locate, count and label the petals and sepals.

2 Which part of the flower do you think will grow into the fruit?

6 Find pictures of examples of wind-pollinated and insectpollinated flowers.

activities ReMeMBeR 1 Match the words in the left-hand column below with those in the right-hand column. Sepal Sperm Petal Sugar Pollen Leaflet Nectary Colour Ovule Egg cell 2 Propose why plants usually produce so many pollen grains. 3 explain the difference between pollination and fertilisation. 4 Complete the table below for each of the labelled plant parts in the diagram at the top of the previous page. Flower part

Function

Male, female or neither

7 The sunflower, shown above, is actually not a single flower. The heart of the flower consists of hundreds of small flowers close together. The petals are not actually real petals either. They are modified leaves, but they do a great job of attracting insects. This flower organisation enables many flowers to be pollinated at once as insects walk over the heart of the flower to collect nectar. (a) investigate which other plants have their flowers organised like the sunflower. (b) Are there some other ways that small flowers can be organised to look like one large flower from far away? Find examples. eBook plus

investigate

The bee orchid looks and smells like a bee to other bees.

5 Is there a relationship between the colour of a flower and the strength of its scent? Design and carry out an investigation to determine whether the colour of the flower influences how strong the scent is.

8 Complete the Sex life of plants interactivity in your eBookPLUS to answer questions about how plants reproduce. Success rewards you with a video of pollination. int-0211 work sheet

13.5 Plant reproduction

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13.6

Plants and parenthood Are you aware that when you bite into an apple, cherry or orange you are actually eating the enlarged ovary of the plant? Did you know that these swollen ovaries contain the plant s babies in their embryonic form? The plants are using you as a way of distributing their young out into the world.

eggs, embryos, seeds and fruit Once the flower has done its job and the egg cell has been fertilised by the pollen nucleus, another sequence of events takes place. The fertilised egg, in the middle of the ovule, divides into a little ball of cells that becomes an embryo. Special tissue called endosperm surrounds the embryo and supplies it with food.

seeds and germination The embryo, inside the seed, is made up of three different parts: the baby shoot (plumule), the baby root (radicle) and one or two thick, wing-like cotyledons. Plumule

Radicle

Seed coat

Cotyledons

Ovules Ovary

Anther Stigma Ovules are fertilised. Ovules

10 days later Ovary

Ovary or fruit

Ovules or seeds

30 days later 60 days later A pear: from flower to fruit

The ovule becomes the seed and tissue forms around it to provide a protective seed coat. During the formation of the seed, the ovary expands and turns into a fruit.

seed dispersal One of the main jobs of fruits is to help disperse or spread the seeds. There is a variety of ways in which plants disperse their seeds: dispersal may involve animals, including birds (as for tomatoes, grapes and apples); water (as for coconuts); or wind (as for grasses and dandelions). Some plants can disperse their seeds by themselves. For example, the fruits of some plants in the pea family (legumes) split open suddenly when they are ripe and dry, throwing the seeds out for long distances.

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When the conditions are right, the seed bursts open and a new plant grows out. This process is called germination. When germination is complete, the embryo has become a young plant or seedling.

Fruit

Seed Parachute

Legume Fruit

Dandelion

Wind dispersal (left) and self dispersal (above)

There are three environmental conditions that are needed by all seeds before they can germinate: water, oxygen and a certain temperature, usually warm. Water is necessary for the seed to swell and burst open and then to transport food to the growing embryo. Oxygen is required to help provide the energy needed for growth and development. The required temperature depends on the particular type of plant. Some Australian plants, such as Banksia and mountain ash (Eucalyptus regnans), require high

Germination of a broad bean

Leaf Cotyledons Seed coat

Root

temperatures to burst the fruit so that the seeds may be released. This adaptation gives these plants an excellent chance of survival in regions prone to bushfires.

InvestIgatIon 13.7 seeds

Moist sand inside paper towel

You will need: 2 maize seeds, 2 sunflower seeds and 2 beans soaked for at least 24 hours gas jar or tall glass paper towel

Seed (between paper towel and glass so it can be seen from the outside)

◗ Line the inside wall of the

gas jar with a double layer of paper towel. ◗ Pour some sand inside the jar

Glass jar or tall glass

until it is about one-third full. ◗ Place the seeds between the

How to set up this experiment

any observable shoot and root in a table each day. 2

◗ Add more sand to the jar. This

will keep the paper towel pressed against the sides of the jar. ◗ Pour water over the sand until all

3

the sand in the jar is moist. ◗ Observe each seed daily for three

weeks.

4

Record how many days it takes for each seed to germinate. Once the seeds have germinated, record the length of

After three weeks, draw a diagram of one of the plants. Label the shoot, roots and leaves. Draw a graph showing how the length of the shoot of each plant changed over time. Did the two different types of seed grow the same way? Describe the similarities and differences.

ReMeMBeR 1 Recall which part of a flower develops into a fruit after fertilisation. 2 Describe the conditions needed for germination. 3 explain why light is usually necessary only once the plant has germinated. 4 If birds eat the seeds of fruit, explain how the seeds can be dispersed.

tHinK 5 construct a mind map showing some foods that are seeds or that are the products of seeds.

investigate anD Design 6 Design an experiment to investigate whether water affects the germination of a variety of different types of seeds. 7 investigate where the germinating seed gets its food from and report back in a diagram.

5

Did you obtain the results that you expected? Explain.

8 Find seeds or pictures of seeds and classify them according to how they are dispersed. Try a Google image search using the key words seed dispersal .

6

Write a conclusion on the basis of your findings.

work sheet

DiscussiOn 1

Although light is not necessary for the germination of most seeds, it is needed once the young shoot breaks through so that the plant can make its own food.

activities

Paper towel lining jar

watch them grow

paper towel and the glass (so that you can see them from the outside of the jar). Ensure that they are spread around the jar so that each seed will have plenty of room.

Withered cotyledons

13.6 Seeds

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13.7

PRescRiBeD FOcus aRea nature and practice of science

Plant research project It s your turn to be a scientist! In the following investigation, you will design and carry out an experiment involving plants. You will also prepare a scientific report about your experiment.

eBook plus

eLesson

Growing plants in Australia This video lesson is presented by a top Australian horticulturist and will provide you with tips for successfully growing plants. eles-0055

choosing a problem Deciding on a problem to solve is often the hardest part of a research project. The following pointers may help you: • In your experiment, you will need to deliberately change one of the variables. This could be: the amount of water additives to water (such as sugar, salt, caffeine and vitamin C) type of growth medium (such as sand, garden soil and gravel) amount of light (You could use different types of shadecloth.) colour of light. (You could use coloured cellophane over the pots.) The variable you change deliberately is the independent variable. • You will need to decide what to measure. The thing you measure is called the dependent variable. Examples of things you could measure include: time taken for seeds to germinate height of the shoots each day number of leaves on each plant mass of seeds produced by each plant. • You will need to make sure that the experiment is fair. That means that all variables except the independent variable should be kept the same (controlled). • You must also include controls. For example, if you wanted to find out how plants were affected by salty water (independent variable), you might give three plants salty water. You would also need to give a second group of plants normal tap water (the control). The only difference between the two groups of plants should be that one group gets salty water while the other gets normal tap water. If you were testing several groups of plants with different amounts of salt, you would still need to give one group of plants normal tap water. The plants with tap water are the control in the experiment. It shows whether the salt (independent variable) has an effect

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You need at least two groups of plants.

on plant growth (dependent variable). The control is used for comparison to see if the independent variable has an effect. If you were testing different types of soil, you would need to ensure that all other variables (controlled variables) are the same for each group of plants. 1. If you were testing the effect of different types of shadecloth on the growth of plants, describe the conditions under which the control group should be grown. 2. Write a brief plan for your investigation. Read the next section, Conducting the investigation before you start. Include in your plan: (a) what you want to find out (the aim of your investigation) (b) a list of materials that you will use (c) an outline explaining how you will make sure that your tests are fair.

conducting the investigation

them to poke through the soil. If you are short of time, you may want to use seedlings rather than seeds for your experiment. The pictures below show some ways to set up plant experiments. 4. Prepare a table in which you can record the progress of your plants for three to four weeks. Use the sample table below as a guide. It can be used like a diary to keep all your observations and measurements together. 5. Predict what you expect to find out. This is your hypothesis.

1. Make sure you use at least 10 seeds or seedlings for your experiment. 2. If you are using seeds, you will need to soak them in water overnight before starting the experiment. 3. There are a few ways to set up the experiment. To investigate germination, you could use the same apparatus as in Investigation 13.7, or you could put the seeds on moist cotton wool in a dish. To investigate the growth of plants, you could plant the seedlings in soil or potting mix and wait for

Step 1

Step 2

Step 3

Step 4

Press a hole about 2 cm deep into the potting mixture with a pencil.

If you are planting more than one plant in each container, mark the position of each seed by sticking a toothpick beside it.

Label your container with your name and the date and any other vital information, e.g. salty water , red light .

Water your seeds, but take care not to overwater! Leave your seeds in a warm and sunny position.

Planting your seeds Step 1

Step 2 Moist cotton wool

Seeds

Petri dish or plate

Water the seeds as required to keep the cotton wool moist, but do not overwater as mould will grow on the seeds.

Put some cotton wool in a Petri dish or plate. Add enough water to moisten the cotton wool. Place the pre-soaked seeds on top of the cotton wool. Another way to set up your experiment

Height of seedling (mm) Tap water Date

Day

5/3

10

What I did Watered all plants at 3 pm; gave each plant 50 mL water

Salt water

A

B

C

D

E

7.1

8.0

8.9

7.5

8.2

Ave.

A

B

C

D

E

5.0

4.4

5.8

4.8

5.2

Ave.

Observations and diagrams

Sample table. This table could be used to record the results for an experiment to find out if watering plants with salt water affects their growth.

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Using your data While your plants are growing, you can record the progress of the plants on a line graph like the one below. This graph shows how the height of two groups of six plants changes. You could use graphs in a similar way to show how the number of leaves changes or how many seeds germinate each day. If any of your plants die, your investigation is not a failure. You must, however, make a reasonable attempt to explain why they died. Progress of bean plants

1 In the table on the previous page, five bean plants are watered with each type of water. Explain why this is better than testing just one plant with each type of water.

Tap water Salt water 25

2 Genevieve is investigating the effect of shadecloth on the growth of bean plants at home. She places three plants under the pergola at the back of her house, which is covered with shadecloth. She places the other three against the wall at the front of the house. All plants are in the same size pots and are given the same amount of water. Describe how Genevieve could improve her experimental design.

20 Height (cm)

C B A

10

F D

5

No shoots visible

E Plant died

0

5

10

15

20

25

Time (days) Use a graph to record the progress of your plants. The independent variable is on the x-axis; the dependent variable is on the y-axis.

Writing your report In reporting your investigation to others, you should use the headings listed below. You will find a description of what should be included under each heading on pages 538–39 of this book. • Aim (purpose) • Procedure (materials and method) • Results (your observations and measurements, including tables, graphs or photos, if appropriate) • Discussion (including evaluation of method and results) • Conclusion (a statement about the key findings in your experiment, which must be related to the aim)

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Activities THINK

30

15

Also, make sure that you give your report an appropriate title. A good title for this investigation would be: • ‘The effect of ______________________ on the growth of bean plants’ • ‘The effect of ____________________ on seed germination’.

3 Cameron is trying to find out whether sand or garden soil is better for growing radishes. He also wants to find out if sugar added to the water that is given to plants makes a difference. Cameron plants three seeds in sand and three seeds in garden soil. The plants growing in sand are watered with tap water. The plants growing in garden soil are given the same amount of a mixture of sugar and water. (a) What two questions is Cameron trying to answer with his experiment? (b) Identify the major problem with Cameron’s experimental design. (c) Is it possible for Cameron to design a better experiment to answer both of his questions with only six seeds? Explain how. 4 Summarise what you know about scientific method and reports into a mind map or another visual map.

INVESTIGATE 5 Propose how a plant would grow in a container that is upside down. Design and perform an experiment to find out. 6 Propose how a plant would grow in a fully enclosed container with a hole in one side. Design and perform an experiment to find out. 7 Can a plant grow without soil? Design and perform an experiment to find out.

13.8

Which plant? In this chapter, we have focused on the group of plants we are most familiar with: the flowering plants. Most of the plants that grow in gardens and most of the plants used as food are flowering plants, so it is easy to forget that there are other groups of plants. Many plants do not produce flowers, some do not produce seeds and others do not even have roots or conducting tissue.

classifying plants One of the main ways plants can be grouped is according to whether they have transport tissue. Known as vascular tissue, this transport tissue consists of two sets of tubes. One set, made of phloem cells, transports sugars throughout the plant. The other set, made of xylem cells, transports water and minerals from roots in the soil to other parts of the plant. Plants with vascular tissue are called tracheophytes. They have roots, stems and leaves. They include flowering plants, conifers and ferns. The other two major plant groups do not have vascular tissue. They include bryophytes (mosses and liverworts) and algae. There is some debate among biologists about the classification of algae. Some biologists consider that most algae are plants. Others argue that only multicellular algae (such as the large seaweed that you sometimes see at the beach) belong in the plant kingdom; they assign unicellular algae with a true nucleus to the kingdom Protista. Another approach is to place all algae in the kingdom Protista. The blue-green algae, however, are

not classified by most scientists as plants or protists as they lack a true nucleus; instead they are assigned to the kingdom Monera.

the language of plants Plants can be described using different words, depending on a person s purpose. For example, in describing a bottlebrush tree: • a scientist would use its correct botanical name, Callistemon citrinus, and say it belonged to the angiosperm or flowering plant group • a gardener might say I planted a new tree called a bottlebrush • a horticulturist would tend to use both scientific and common names.

carnivorous plants some plants trap animals to get the nutrients they need. these plants live in soils that are poor in some nutrients. they still make their own food by photosynthesis and absorb available soil nutrients. However, they get their nitrogen and some minerals from digesting animals such as insects and spiders. the venus flytrap is a well-known example of a carnivorous plant. the venus flytrap s leaves are shaped like two wings, with long spines along the edge. On the surface of the wings are trigger hairs. When the insect walks on the hairs, it causes the two halves to close quickly. the spines interlock to form a cage and trap the insect. the plant makes a sweet liquid to attract the insects. Once an insect is trapped, the plant makes a digestive juice to break it down.

A bottlebrush flower (Callistemon citrinus)

Words used to describe groups of plants Scientific term

Common name

Bryophytes

Mosses and liverwort

Pteridophytes

Ferns

Angiosperms

Flowering plants

Gymnosperms

Conifers

Tracheophytes

Plants with stems

Gardeners use words like tree , shrub , herb and grass to describe groups of plants. To a scientist, a tree could belong to the angiosperm or gymnosperm group.

A scientist would carefully examine the characteristics of the plant to find out if it had flowers, seeds and fruit, or cones containing seeds. The scientific names for individual plants and groups of plants are more specific than the common names.

13 Plants 353

Plant group

Location

Stem and roots

Leaves

Flowers

Seeds

Flowering plants (e.g. roses, fruit trees, grasses, eucalyptus trees)

Mostly on land

Yes

Yes

Yes

Yes — reproduce from seeds. Seeds form inside flower, which develops into a fruit.

Conifers (e.g. firs, pines, spruces)

On land

Yes

Yes — mostly fine and needle-shaped

No

Yes — form on scales of cones

Ferns (e.g. maidenhair fern, fishtail fern)

Damp, shady, cool regions

Yes

Leaves are fronds that uncurl as they get bigger.

No

No — reproduce from spores on leaves. These are released from brown spore cases that form on the underside of leaves.

Mosses (e.g. sphagnum moss)

Damp, shady, cool regions

No stems. ‘Roots’ are more like fine hairs.

Yes, but simple structure — tiny and dainty

No

No — reproduce from spores

Algae

Water (oceans, lakes, rivers)

No

No

No

No — reproduce from spores

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activities ReMeMBeR 1 Recall the main difference between bryophytes and tracheophytes. 2 Which groups of plants are called tracheophytes? 3 Decribe two differences between conifers and flowering plants.

tHinK 4 explain why plants with vascular tissue can grow larger than ones without it. 5 A description of three plant specimens follows. identify the plant group that each may belong to. (a) A plant with needle-like leaves and seeds that form inside cones (b) A plant with an obvious root system, a stem, leaves and with fruit containing seeds (c) A plant found in a cool, shady rainforest, with a horizontal stem and curled up new leaves with rows of brown spots underneath them

Grevillea treueriana

6 identify which plant group the plant below belongs to.

Callistemon pachyphyllus

(b) compare and contrast each of the following pairs of plants. (i) Callistemon pachyphyllus and Callistemon citrinus (ii) Grevillea treueriana and Callistemon citrinus (c) explain why the name Callistemon citrinus is written in italics but not the name bottlebrush.

investigate

7 Use the information on page 354 to construct a key that shows one way to classify plants. Start by deciding which feature best divides plants into two groups. For each group, decide what features they have in common, and how they differ. This will help you decide how to break them down further into sub-groups. If you need some help with drawing keys, check some shown on pages 89 90 in chapter 4. 8 (a) Which of the two plants above right is more closely related to Callistemon citrinus (shown on page 353)? explain how you can tell from the names of the plants. (Hint: See page 93.)

9 Many flowering plants are useful to humans as food and to manufacture products such as paper and furniture. Many of the chemicals used to make medicines, dyes and cosmetics are extracted from flowering plants. Find pictures of plants that are useful to humans and create a collage entitled Flowering plants an important resource . eBook plus

10 Use the Corpse flower weblink in your eBookPLUS to learn why this flower smells so dreadful. work sheet

13.7 Classifying plants

13 Plants 355

LooKIng BaCK 1 Identify the minerals needed in large amounts by plants. 2 Recall two examples of trace elements.

8 Write down in your workbook which letter in the following diagram corresponds to each of these terms. ovules, sepals, filament, style, stigma, ovary, anther, petals, stamen, carpel

3 Compare and contrast xylem and phloem. 4 Write a word equation for photosynthesis.

F

A

5 Recall what happens to the sugars made in photosynthesis. 6 Explain how stomata open and close and why this is important to the plant s survival.

G

7 Study the following graph showing changes in size of stomatal openings. (a) Describe any pattern in the size of the stomata throughout the day. (b) How might the plants decrease the amount of water lost from them each day? (c) Describe what happens to a plant when it wilts. Explain your answer with diagrams. (d) Under what conditions would a plant be turgid? Explain your answer with diagrams.

Stomatal opening (per cent)

Changes in size of stomatal openings over 24 hours 100 Sunrise Sunset

80 60 40 20 0 Midnight

6 am

12 noon

6 pm

Midnight

H I J E B D C

9 Charlotte wanted to find out if temperature affects the growth of plants. She bought four seedlings. She put one seedling in the fridge and one in her garage (which has no windows so is dark and cooler than her house). She put the third seedling on the windowsill (in full sun) and the fourth seedling on her desk (out of the sun but in daylight). Charlotte measured the height of each seedling every day for 10 days. Her results are shown in the table below. (a) Write an aim for Charlotte s experiment. (b) Suggest three improvements to Charlotte s experiment. (c) Graph Charlotte s results. (d) Write a conclusion for this experiment. 10 Construct a concept map to summarise what you know about plant classification.

Heights (cm) of seedlings Position

356

Day 1

Day 2

Day 4

Day 5

Day 6

Day 7

Day 8

Day 9

Day 10

6.0

6.2

6.6

7.0

7.3

7.5

7.7

8.0

Fridge

5.0

Garage

5.0

5.6

6.2

6.6

7.0

7.3

7.6

7.9

8.4

8.8

Windowsill

5.0

6.0

6.7

7.5

8.0

8.5

9.0

9.6

10.2

10.6

Desk

5.0

5.8

6.3

7.0

7.5

8.0

8.5

9.1

9.6

10.0

Core science | stage 4 Complete course

5.5

Day 3

11 Suggest which two of the following organisms are most closely related. (Hint: see page 93.)

3 What is the name of the part labelled A in the diagram below?

A

Mentha spicata

Tussilago farfara

Borago officinalis A B C D

Stamen Style Stigma Ovule

(1 mark)

4 Which of the following flow charts shows the stages of the life cycle of a flowering plant in the correct order?

Foeniculum officinale

A

B

C

D

Flower formation

Flower formation

Growth

Germination

Pollination

Fertilisation

Flower formation

Growth

Fertilisation

Pollination

Fertilisation

Flower formation

Fruit formation

Fruit formation

Pollination

Seed dispersal

Seed dispersal

Germination

Fruit formation

Fruit formation

Germination

Seed dispersal

Germination

Pollination

Growth

Growth

Seed dispersal

Fertilisation

Primula officinalis

Mentha piperita

Scabiosa columbaria

(1 mark)

test YOuRseLF 1 Which of the following statements is correct? A Water moves up and down the stem of a plant in the xylem tubes. B Phloem tissue takes sugars from the roots to the leaves of plants. C Phloem tissue takes water from the leaves to other parts of the plant. D The movement of water from the roots to the leaves occurs in xylem tubes. (1 mark) 2 When does respiration occur in plants? A Never. Plants photosynthesise rather than respire. B At night only C During both night and day D During the day only (1 mark)

5 Use your knowledge of plants to explain the following. (a) It is possible to grow plants without soil (hydroponically) as long as certain nutrients are added to the water. (1 mark) (b) Seedlings that are grown in the dark do not become green. They may initially grow faster than plants left in sunlight, and then eventually die. (1 mark) (c) Some farmers find that their orchards produce more fruit if there are beehives near the orchard. (1 mark) 6 Variegated leaves are green in some parts and yellow in other parts. The yellow parts of the leaves do not contain chlorophyll. Predict whether photosynthesis would occur in the yellow parts of the leaves. (3 marks) work sheets

13.8 Plants puzzles 13.9 Plants summary

13 Plants 357

stUDY CHeCKLIst

ICt

Plant structure and function

eBook plus

■ describe the structure and function of plant roots 13.1 ■ explain why plants need to take in certain nutrients ■ ■ ■ ■ ■

through their roots 13.1 assess the importance of the nitrogen-fixing bacteria found in root nodules 13.1 describe the structure and function of plant stems 13.2 distinguish between xylem and phloem tissue 13.2 describe the structure and function of leaves 13.3 outline the role of stomata in plant leaves 13.3

sUMMaRY

eLessons Growing plants in Australia This video lesson is presented by a top Australian horticulturalist and provides you with tips for successfully growing plants in Australia. Watch this video as an introduction to your experiments with plants.

Photosynthesis ■ recall the word equation for photosynthesis 13.3 ■ explain why plants need to photosynthesise 13.3 ■ identify chloroplasts in plant cells viewed under a microscope

13.3

■ interpret the results of experiments relating to photosynthesis

13.4

■ extract information from a timeline outlining some of research carried out to investigate photosynthesis

13.4

Life cycle of flowering plants ■ recall the names and functions of the parts of flowering plants

13.5

■ distinguish between pollination and fertilisation in flowering plants

13.5

■ describe how fruit and seeds are formed from flowers

13.6

■ outline some ways in which seeds can be dispersed

13.6

Searchlight ID: eles-0055

interactivities Sex life of plants This interactivity delves into the seedy world of the sex life of plants. Play the revelation game and answer questions about how plants reproduce. Success rewards you with an animation of the sex life of plants.

■ investigate factors that affect seed germination by designing and carrying a scientific experiment

13.6, 13.7

Plant classification ■ distinguish between algae, mosses and liverworts, ferns, conifers and flowering plants 13.8 ■ account for the fact that scientists and gardeners might use different names to refer to the same plant 13.8 ■ construct a dichotomous key to classify plants into the five main plant groups 13.8

nature and practice of science ■ design, carry out and write a report about a scientific investigation involving seed germination or plant growth 13.7 ■ distinguish between independent, dependent and controlled variables 13.7

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Searchlight ID: int-0211

14

Body systems part 2

To stay healthy, it is important to have a balanced diet. Food is a fuel that provides us with the energy we need to live. It also contains important nutrients that our bodies need to function properly. Our muscles use the energy from the food we eat to allow us to move. This and other processes that occur inside the body generate waste products that must be removed; this is the job of the excretory system.

In this chapter, students will: 14.1 ◗ learn about and measure the energy

content of food 14.2 ◗ distinguish between the main

nutrients found in food 14.3 ◗ discuss the importance of a balanced

diet 14.4 ◗ learn about the work of dietitians 14.5 ◗ describe the structure and function of

the digestive system 14.6 ◗ distinguish between mechanical and

chemical digestion and describe the structure and role of teeth in digestion 14.7 ◗ explain the role of enzymes in

chemical digestion 14.8 ◗ describe the function of the skeletal

system and explain how muscles and bones work together to allow movement 14.9 ◗ explain the role of the excretory

system and describe the functions of the main organs involved in excretion.

You should eat a wide variety of food to get the nutrients and energy that your body needs to function properly.

14Body systems

part 2

Bush tucker When Europeans first came to Australia, they thought that it was a dry, empty land with no water or food. The Australian Aboriginals, however, lived and survived in this harsh land. They followed a simple hunter gatherer lifestyle. For tens of thousands of years, Aboriginal people used a range of native plants and animals for food, medicine, tools, clothing and shelter. They ate seasonal fruit, nuts, roots, vegetables, meat and fish. Although this was all available in the bush, many European settlers nearly starved. Others got very sick or died from eating native food incorrectly. Many of the fruits and nuts need to be treated to make them safe to eat. Nowadays, native food is widely eaten and is called bush tucker. The knowledge about native plants and animals that has been passed on by traditional Australian Aboriginals over thousands of years is also important in making new products.

1. Which food group is missing from the traditional Aboriginal diet? 2. Why is it important to know what is in the food we eat? 3. Why do we need to eat different types of food?

nutrition in the media Hardly a week goes by without current affairs programs and newspapers running a story about childhood obesity, the latest weight loss diet, food allergies or the effect of particular nutrients on health. 1. Use a database such as EBSCO to search for an article about an issue that relates to nutrition. Make sure you choose an article you can understand. 2. Briefly outline what the article is about. 3. Is the article based on scientific evidence or personal opinion? How can you tell? 4. Can the information in the article be trusted? Explain how you might check the reliability of the information in the article.

14.1

Food as a fuel Are you feeling full of energy today? The human body, just like a car, needs to be provided with fuel to keep working. That fuel is the food we eat. Our bodies break down the food and release the energy that is locked up inside it. This energy can then be used by our bodies to move, grow and carry out important processes that are vital to our health.

The amount of energy needed each day depends on how much physical activity a person does, as well as other factors including their size, age and gender. The table below shows the amount of energy used by a range of activities. For example, a person who sits at a desk for most of the day needs to eat less food than a person who spends a large part of the day walking. If we take in more energy than we need, our bodies store the excess energy as fat. If we take in less energy than we need, some of this fat can be broken down and used for energy. Activity

Approximate energy use (kJ) per hour

Sleeping

250

Food as a fuel

Very light

sitting, reading, watching television, driving

450

To keep a car running, you need to provide it with petrol. Inside the engine, the petrol reacts with oxygen; it undergoes combustion or burns. This releases energy that is used to run the motor. Something very similar happens inside our bodies. The food we eat is broken down into a number of chemicals including glucose. Just like petrol, glucose can react with oxygen to release energy. This process is called respiration. Food contains stored energy. The amount of energy stored in the food is measured in kilojoules (kJ) or Calories (with a capital C). • One calorie (with a lowercase c) is the amount of energy needed to heat 1 g of water by 1 C. • One calorie is equivalent to 4.2 joules (J). • One kilojoule (kJ) is equal to 1000 joules. • One Calorie (with a captial C) is equivalent to 1000 calories (with a lowercase c). So, if a breath mint contains 2 Calories, that means that it contains enough energy to heat 200 g water (about a cup) by 10 C.

Light walking leisurely, washing, shopping, light sport such as golf

950

Moderate fast walking, heavy gardening, moderate sport such as bicycling, tennis, dancing

1800

Heavy vigorous work, sport such as swimming, running, basketball and football

3500

Maintain weight

Gain weight

Energy intake

Lose weight

Energy used

To maintain a healthy weight, it is important to balance your energy intake with the energy you use.

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part 2

361

InveStIgatIon 14.1 It seems so simple doesn t it? Take in more energy than your body uses up and you will put on weight. Take in less energy than your body uses up and you will lose weight. Yet some people seem to be able to eat a high-energy diet with little effect on their weight. one scientist set out to determine whether eating too much food has the same effect on all people. Fredrick nystr m of Link ping university in sweden recruited 18 lean and healthy volunteers and asked them to double their energy intake and avoid exercising for one month. For health reasons, the volunteers were asked to stop the experiment if their weight increased by more than 15 per cent of their original weight. one volunteer reached this after just two weeks. Another volunteer found that his weight had increased by only 4.6 kg by the end of the experiment. nystr m has suggested that perhaps some people release more of the extra energy they take in as heat rather than store it as fat. so, after overeating, these people may feel warmer or more fidgety as their bodies use up some of the extra energy.

Measuring the energy in food You will need: small metal basket (used to fry food) samples of small biscuits, potato chips, uncooked pasta, crouton or small piece of toast thermometer retort stand, bosshead and clamp large test tube Bunsen burner measuring cylinder The apparatus used in this experiment Test tube Burning food

Wire basket

Before starting this experiment, read all the steps below and make a list of the risks (dangers) associated with this activity and how you plan to minimise these risks. ◗ Use the clamp to attach the test tube to the retort stand. ◗ Measure 30 mL of water and pour it into the test tube. ◗ Measure the temperature of the water. ◗ Weigh the biscuit. ◗ Place the small biscuit in the wire basket and set fire to it using the Bunsen

burner. When the biscuit is alight, put the basket containing the biscuit underneath the test tube. The heat released from the burning biscuit will heat the water. Hold the basket under the test tube until the biscuit is completely burned. You can tell that the biscuit is completely burned if it is all black and will not re-ignite in the Bunsen burner flame. ◗ Measure the temperature of the water again. ◗ Calculate the amount of energy that was stored in the biscuit, using the

following equation. Eating energy-dense food caused all of the volunteers to gain weight, but some gained weight a lot faster than others.

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Energy (in joules) = 4.2 × volume of water (in mL) × increase in temperature (in C) ◗ Calculate the amount of energy per gram of food by dividing the amount of energy by the mass of the food. ◗ Repeat the steps above using the other food samples.

◗ Copy and complete the table below.

Food

DIscussIon Biscuit

Chip

Pasta

Crouton/ toast

1

Copy and complete the aim of this experiment: To compare the amount of ___________ contained in a range of foods .

2

Copy and complete the conclusion: The food that contained the most energy per gram was __________________ .

3

Why was it necessary to calculate the amount of energy per gram of food?

4

Did all the heat from the burning food go into heating the water? Explain how this might have affected the validity of this experiment.

a. Mass of food (g) b. Volume of water (mL) c. Initial temperature of water ( C) d. Final temperature of water ( C) e. Increase in temperature (= d

c)

f. Energy in food (J) (= 4.2 × 30 × e) g. Energy in food (kJ) (= f ÷ 1000) h. Energy per gram of food (kJ/g) (= g ÷ a)

activities REMEMBER 1 Recall the name of the process where glucose reacts with oxygen to release energy. 2 Recall which unit energy is usually measured in. 3 Copy and complete the following statements: (a) 1 kilojoule = _____________ joules (b) 1 Calorie = ______________ calories (c) 1 calorie = ______________ joules (d) 1 Calorie = ______________ kilojoules 4 If you take in more energy than your body needs, explain what happens to the extra energy.

usE DATA 5 Use the table on page 361 to answer the following questions. (a) How much energy is used up in 1 hour of fast walking? (b) calculate the amount of energy used in 30 minutes of running. (c) Explain why two people might both dance for 20 minutes but burn very different amounts of energy.

6 The tables below show the recommended daily energy intake for 12 15 year olds and the amount of energy contained in a range of foods sold at a snack bar. (a) What is the recommended daily energy intake for someone of your age and gender? (b) For lunch, Fred ate one hamburger and an apple pie with ice-cream. He also drank one medium orange juice. (i) calculate Fred s energy intake. (ii) Fred is 13. calculate the percentage of his recommended daily energy intake that his lunch contains. (c) Identify the combination of main course and dessert that supplies the least energy. Recommended daily energy intake, in kilojoules, for 12 15 year olds Recommended daily intake (kJ)

(d) calculate how many minutes of walking would be needed to use up the energy contained in two slices of pizza. (Hint: See the table on page 361.) eBook plus

7 Use the Kilojoule Burn calculator weblink in your eBookPLUS to learn how many calories you will burn from performing a number of common exercises. work sheet

14.1 Food facts

Nutritional information for a snack bar menu Food

Energy (kJ)

Pizza (2 slices)

2060

Hamburger

1900

Salad sandwich

940

Chocolate eclair

1320

Fresh fruit salad

290 2310

Age (years)

Male

Female

12

9 800

8600

Apple pie with ice-cream

13

10 400

9000

Medium cola

14

11 200

9200

Strawberry thick shake

15

11 800

9300

Medium orange juice

384 1230 530

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14.2

essential intake Why are some foods better for you than others? It is almost always because of the nutrients they contain. Nutrients are substances that give us the energy and the raw materials to grow, move, repair and build tissue, reproduce, and to stay alive. Nutrients can be divided into five main groups.

carbohydrates Carbohydrates provide a source of energy. There are two types of carbohydrates: simple carbohydrates and complex carbohydrates. Simple carbohydrates are also called sugars. They include glucose, sucrose (the type of sugar used for cooking), fructose (a type of sugar found in fruit) and lactose (found in milk). Complex carbohydrates are made up of simple sugars joined together. Starch is an example of complex carbohydrate. It is found in bread, cereal, pasta, rice, potatoes and many other foods. Starch needs to be broken down into glucose before it can be used by the body for energy. Fibre or cellulose is another type of complex carbohydrate. Cellulose is also made up of glucose, but the glucose units are joined up in a different way from starch. Humans lack the necessary enzymes to break cellulose into glucose, but bacteria that live in the gut can break it down to some extent. A lot of the fibre you eat is excreted from your digestive system without having been broken down into glucose. However, it still plays an important role in keeping us healthy (see page 368). All carbohydrates are made up of the chemical elements

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Core Science | Stage 4 Complete course

These foods contain a large amount of carbohydrate.

carbon, hydrogen and oxygen. Carbohydrates are organic compounds. That means that they contain the element carbon. On average, 1 g of carbohydrate provides 16 kJ, although the exact amount of energy depends on the type of carbohydrate.

Proteins Good sources of protein include meat, fish, dairy products, eggs, nuts and legumes. Proteins are a source of energy like carbohydrates, but they have another important role. Proteins are broken down by the body into amino acids. The amino acids are then used to make important chemicals such as enzymes. They are also used to make muscle, hair, nails and other vital tissues. Proteins are organic compounds and they are made up of the elements carbon, hydrogen, oxygen and nitrogen, with 1 g of protein providing 17 kJ of energy.

In your great-grandparents days, many children were given a daily dose of cod liver oil to maintain good health. It turns out that your greatgrandparents may have been right about the benefits of fish oil. Fish oil is rich in omega-3 fatty acids. These fatty acids are being investigated as a possible treatment for conditions including rheumatoid arthritis, depression, attention deficit disorder and heart disease. A number of scientific studies have shown that omega-3 fatty acids affect behaviour and mood. For example, Bernard Gesch did an experiment involving British prison inmates. He gave half the people who had volunteered for his study a daily supplement that contained omega-3 fatty acids and other vitamins and minerals. The other prisoners were given a placebo (a tablet that looked just like the supplement but did not contain fatty acids, vitamins or minerals). over time, he found that the prisoners taking the supplement were involved in a lot fewer violent incidents. The prisoners taking the placebo showed no significant change in their behaviour.

These foods are a good source of omega-3 fatty acids.

InveStIgatIon 14.2 Testing food for nutrients You will need: test-tube rack 4 test tubes safety glasses glucose solution starch solution gelatine solution

distilled water iodine solution test-tube holder Benedict s solution tongs candle or Bunsen burner

matches heatproof mat 0.01 M copper sulfate solution

1.00 M sodium hydroxide solution food samples (if solid, crush a small amount into a mash with water)

Do each of the three tests described below on a sample of each of the four liquids shown on the right. Make sure to use a fresh sample of each liquid for each test. Glucose solution

◗ Copy and complete this table for recording the

test results. Test results

Water

Starch solution

Glucose solution

Gelatine solution

Starch solution

Water

Gelatine solution

Starch test Glucose test Protein test

Starch test ◗ Add two drops of iodine solution to each of the

Glucose solution

four test tubes. Observe any colour change and record the results.

Starch solution

Gelatine solution

Water

Iodine

Glucose test ◗ Add four drops of Benedict s solution

to each of the four test tubes. Gently heat each test tube over the candle or Bunsen burner flame. Observe any colour change and record the results.

Glucose solution

Starch solution

Gelatine solution

Water

Benedicts solution

CuSO4

NaOH

Protein test ◗ Add ten drops of copper sulfate solution to each of

the four test tubes. Then add five drops of sodium hydroxide solution to each test tube. Observe any colour change and record the results.

10 Glucose solution

◗ Using the three tests above, investigate the food

Starch solution

Gelatine solution

Water

5 Copper sulfate solution

Sodium hydroxide solution

samples for the presence of starch, glucose and protein.

DIscussIon 1

Construct a table to record your observations.

2

Which foods contain two or more of the nutrients tested for?

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Lipids Lipids include fats and oils. Foods that are high in fat include nuts, butter, cooking oil, fried food, pastry and many snack foods such as biscuits and chips. Fats are a source of energy. They are also needed to provide cushioning for organs, to maintain a stable body temperature and to keep your skin and hair healthy. Lipids are broken down by the body into fatty acids, which are used in many chemical processes in the body. Fats and oils are organic compounds that contain the elements carbon, hydrogen and oxygen. On average, 1 g of fat releases 37 kJ of energy.

Vitamins Vitamins are organic nutrients that are required in very small amounts. We need 13 vitamins. Vitamins A, D, E and K are fat soluble and are found in foods containing fats and oils. Vitamins B and C are water soluble and are found in cereals, fruit, vegetables, meat and nuts. Lack of a particular vitamin leads to a vitamin deficiency disease; for example, lack of vitamin D can lead to tooth decay and bone deformities.

Minerals Minerals are nutrients that do not contain the elements carbon, oxygen and hydrogen. For this reason they are called inorganic nutrients. There are more than 20 minerals that are required in our diet, including calcium, phosphorus, magnesium, sodium, iron, potassium and zinc. Minerals are found in all types of food and in drinking water. Each mineral has a particular job to do to keep the body healthy. A lack of a mineral can also cause a deficiency disease.

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activities REMEMBER 1 Copy and complete the table at right. 2 Identify what the items in the following pairs have in common. (a) Carbohydrates and lipids (b) Cellulose and starch (c) Fats and oils (d) Iron and potassium (e) Hormones and enzymes

Feature

Carbohydrates

What the body uses this nutrient for

Energy source

Proteins

Lipids

Example of food containing this nutrient What this nutrient is broken into by the body

Amino acids

Chemical elements that make up this nutrient

Carbon, hydrogen, oxygen

Energy per gram (kJ/g)

3 compare organic nutrients and inorganic nutrients. 4 Which vitamins are fat soluble and which are water soluble? 5 Define the term mineral in relation to the food we eat. 6 Explain why it is important to use a placebo when testing the effect of a dietary supplement or medicine. 7 In his experiment (see page 364), Bernard Gesch used a supplement that contained both fatty acids and other minerals and vitamins. outline how he could test whether it was the fatty acids or the vitamins and minerals that caused the improvement in the behaviour of the prisoners.

usE DATA 8 Use the nutritional panel above right to answer these questions. (a) The recommended daily intake of protein for a 13 year old is 40 g. calculate the percentage of the recommended daily intake of protein supplied by one serving of this food. (b) If one serving of this food provides 6 per cent of the recommended daily intake of fat, calculate the daily recommended intake of fat.

(c) Which food could this label belong to? NUTRITIONAL INFORMATION Servings per package: 8 Serving size: 30 g Average Average quantity quantity per per serving 100 g Energy 470 kJ 1570 kJ Protein 1.4 g 4.6 g Fat total 2.8 g 9.3 g saturated 2.0 g 6.7 g Carbohydrate 21.0 g 70.0 g sugars 8.7 g 28.9 g Dietary fibre 1.7 g 5.5 g Sodium 50 mg 180 mg

InVEsTIGATE 9 Collect 10 nutrition panels from food packages. Use the information on the nutrition panels to rank the foods from highest to lowest for: (a) energy (b) fat (c) carbohydrate (d) protein. 10 Some foods are labelled with the Heart Foundation Tick. Find out what requirements the food must meet to be allowed to display the tick. work sheet

14.2 Nutrients

14.3

Healthy eating Hamburger, pizza, jelly and ice-cream; apples, oranges, carrots and peas there is such a variety of food to choose from. How do you choose? Which foods should you eat more of and which should you eat less of? The bottom (larger) section of the pyramid below shows the types of food that you should eat most of. The foods that you should eat least of are in the top (smaller) section. Health professionals usually classify food into the following wing five groups: Eat least 1. breads and cereals Foods that are high in fats and sugars should be 2. vegetables egetables eaten in small amounts only. Fat is part of many 3. fruits foods that we eat, so there is no need to add extra. Sugars are simple carbohydrates and 4. milk and milk products are often found in processed food. 5. meats, nuts, beans and eggs. Different types of food contain different Eat moderately nutrients, which are required for growth and Meats, nuts, beans and eggs are good activity.. The amount of each nutrient you sources of protein. Aim for two need depends on your age and activity servings of these daily. Selecting level. lean cuts of red meat and skinless A balanced diet contains all the chicken adds little to your fat intake. food groups in the correct amounts Milk and milk products are to keep you healthy. You need to important for their calcium eat more of foods that contain and energy content. Three complex carbohydrates, vitamins servings a day are required, or 600 mL of and minerals and less of milk. foods high in salt, sugar Low-fat milk has and fat. less energy in it, but still contains vitamins and minerals.

Eat most Fruits and vegetables are rich in complex carbohydrates, vitamins and minerals. Try to eat five servings of vegetables and two servings of fruit a day. Breads and cereals are good sources of complex carbohydrates. Wholemeal bread and wholegrain cereals contain more fibre and vitamins than white bread and flours. At least four servings of bread and cereals should be eaten daily.

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In one end and out the other Fibre is found in the walls of plant cells. It is only partially broken down by your digestive system. Although it really does go in one end and out the other , it serves a very useful purpose and is an essential part of your diet. It provides bulk to your food, allowing it to move properly through your intestines. Without fibre, undigested food travels too slowly through the large intestine, losing too much water. The result is that the solid waste (faeces or poo) is hard and difficult to release. This is known as constipation. Bowel cancer and other medical conditions have been linked to a diet low in fibre. Fibre can be found only in foods that come from plants foods such as fruits and vegetables, wholegrain breads and cereals, nuts and seeds. A grain of wheat Wholegrain products are higher in dietary fibre because they contain Endosperm the outer covering, or bran, of the grain. When grains are highly Bran processed, as they are in the production of white bread, white flour and Embryo many breakfast cereals, the bran is removed.

activities REMEMBER 1 Define the term balanced diet . 2 List the five food groups under the headings: Eat most , Eat moderately and Eat least . 3 Recall how many servings of fruit and vegetables you should eat every day. (A serving is a typical amount of a food that you would eat in a single meal.) 4 Recall how many litres of water a day we lose through breathing out, sweating and urinating.

I ll have water with that! Water is an important part of your diet. The human body is about 60 per cent water. If you lose 10 per cent of your body water, then you become ill. If you lose 20 per cent, you can die. Loss of water is called dehydration. We lose water every day through breathing out (0.5 L per day), sweating (0.5 1 L per You need to replace the water you lose. day) and urinating (1.5 2 L per day). We get about 1.0 1.5 L of water per day from the food we eat and about 0.25 L of water per day from chemical processes in the body. We also get water by drinking it, and we should drink 1 2 L per day to keep our bodies healthy. Water makes up most of the fluid part of blood, called plasma. It allows food and waste to be moved about the body. saliva is a watery fluid in your mouth that makes your food slippery so that it is easy to swallow. Water also helps to keep your body cool, through sweating. sweating causes water to evaporate from your skin, using body heat to do so. We cannot live more than three days Sweating: 0.5 1 litre/day without drinking water, Breathing out: 0.5 litres/day but can go forty days Urinating: 1.5 2 litres/day without food.

fruit for morning tea; and a meat pie for lunch, what would be a good dinner to help balance your diet to fit the healthy-eating pyramid? 6 (a) Make a list of all the food you ate over the last 24 hours. (b) classify the food you ate into the groups that make up the healthy food pyramid. (c) How many serves of fruit and vegetables did you eat? (d) Identify which food groups you need to eat more of to make your eating habits fit the healthy-eating pyramid.

DEsIGn AnD cREATE THInK 5 If you had cereal and orange juice for breakfast; yoghurt and

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7 Design and make a poster to promote the healthy-eating pyramid for your school canteen. Use the

types of food your canteen sells to decorate your poster.

InVEsTIGATE 8 The law requires certain nutritional information to be written on food packages. Do some research and find out what nutritional information companies need to include on their packaging. eBook plus

9 Test your ability to identify common foods that are high in certain nutrients by completing the A healthy diet interactivity in your eBookPLUS. int-0214 work sheet

14.3 Food pyramid

14.4

PREscRIBED Focus AREA current issues, research and development

Science careers: dietitian through a drip or nasogastric tube (a tube that goes into the nose and down to the stomach). If a patient cannot eat due to a medical condition (such as tongue cancer), a dietitian will calculate how much and what type of food solution the patient needs.

Joanne

Dietitian,

giving dietary advice to a patient

Joanne (not her real name) is a dietitian in a large city hospital. She is an expert on the science of food and its effect on the body. She works closely with doctors and other health practitioners and provides expert nutrition and dietary advice to patients. She has also been involved with a number of research projects. A large part of the work of dietitians is to educate people about the type of diet they should be eating by explaining complex scientific information about nutrition in a way that patients can understand. Patients who have recently been diagnosed with dietrelated diseases, such as diabetes, coeliac disease, heart disease and certain types of cancers, are referred to a dietitian to advise them on the types of foods they should eat. Certain medical conditions require that the patient follows a very strict and very specific diet. For example, patients with kidney problems may need to dramatically cut down the amount of salt they take in. This means that ordinary foods such as cheese and rice bubbles can create health problems for them. Dietitians are also called upon when patients need to be fed

and some dietitians work for the government or large companies that manufacture food. The skills needed to be a dietitian vary with the type of work that they do, but all dietitians need a very good knowledge of food and its effect on the body. Good communication skills are also important as well as strong interpersonal skills (being able to work with people). All dietitians have university qualifications. Some universities require students to complete a science degree before specialising in nutrition.

activities THInK A doctor inserting a nasogastric tube into a patient

A number of dietitians also do research. For example, Joanne has been involved in a study to assess the effect of patients nutritional status on the time it takes for them to recover from an injury or illness. She worked out whether the patients were well nourished or malnourished and recorded the length of time the patients stayed in hospital. She showed that malnourished patients needed more time in hospital to recover from their injury or illness. Not all dietitians work in hospitals. Some dietitians have their own practice (an office where patients come to see them), and other dietitians work with particular communities. Sport dietitians work with athletes

1 Justify why dietitians need good communication and interpersonal skills. 2 Identify other skills that might be important for dietitians. 3 Explain why athletes may need to see a dietitian.

InVEsTIGATE 4 Osteoporosis, scurvy, atherosclerosis and rickets are all diseases with a dietary link. For each disease, find out what the symptoms are and how the disease is linked to the type of food eaten. eBook plus

5 Use the Dietitians Association weblink in your eBookPLUS to find the name of the university closest to where you live that offers a course that can qualify you to work as a dietitian.

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14.5

the digestive system The role of the digestive system is to break down the food that we eat into particles that are small enough to pass through the walls of the intestines and into our blood. A number of organs make up the digestive system. Some organs break up the food mechanically by cutting, grinding or churning it. Other organs secrete chemicals that can break the chemicals in the food into smaller molecules. Teeth Used to bite and chew food into small pieces. Tongue Works the food into a little round ball, called a bolus. It then pushes the ball to the back of the mouth, where it is swallowed. Epiglottis A flap of tissue that closes off the entry to your lungs so that food does not go down and cause you to choke Oesophagus Directs the food to the stomach. It is a long muscular tube that moves the food by the process of peristalsis. Peristalsis squeezes food down the oesophagus by repeated waves of muscle contractions. Liver Controls the number of glucose molecules in the blood. When there is too much, the liver stores it as glycogen and releases it when needed. It also makes bile, which breaks down fat into small droplets in the small intestine. The bile is stored by the gall bladder until it is needed in the small intestine. The liver also breaks down toxins in the blood. Stomach A large muscular organ that churns and mixes the food. The stomach lining releases chemicals that start to break down protein. It also releases hydrochloric acid, which kills unwanted bacteria. The stomach can hold between two and four litres of food and can store it for about four hours. Appendix A small projection at the beginning of the large intestine. In humans, it does not help with digestion.

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eBook plus

eLesson

From dinner plate to sewerage system Watch the amazing journey of food through the human body. eles-0056

Salivary glands Make about 1.5 L of saliva a day. Saliva moistens the food, making it easier to chew and swallow. Saliva also contains chemicals that break down the starch in food.

A gory tale from the past

Partly digested food is forced along the oesophagus by peristalsis a wave of involuntary muscular contractions.

Gall bladder Stores bile made in the liver until needed in the small intestine Pancreas Makes chemicals that are used in the small intestine. It also reduces the effect of the acid from the stomach on the walls of the small intestine. Small intestine A long, hollow, coiled tube about six metres long. It is the main organ of digestion. Food, which is now like a creamy soup, passes slowly into it. Liquid from the pancreas and bile from the gall bladder enter the small intestine to help with digestion. The small intestine is where the breakdown of starch and proteins is finished and fat breakdown occurs. The food particles are then tiny and can pass through the wall of the small intestine into the bloodstream. Large intestine Undigested food and water pass into the large intestine from the small intestine. Bacteria in the large intestine help in making some vitamins and are the main source of gas. Water, vitamins and minerals pass into the bloodstream. Rectum Faeces is stored in this last part of the large intestine. Faeces contains the waste products of digestion. It consists of about 75 per cent water and 25 per cent solid matter mainly dead bacteria and fibre. Anus Releases the faeces as waste

When Alexis St Martin was accidentally shot in the stomach at close range, he was not expected to recover from his injuries. He had a hole the size of a fist in his stomach. An army surgeon named Beaumont treated him. Alexis did recover but, as the wound healed itself, the edge of the hole in his stomach attached itself to the edge of the hole in his skin, so there was a small passage between the inside of his stomach and the outside of his body. The passage had to be sealed with bandages so the food and stomach juices could not leak out of his stomach. Beaumont used this opportunity to study the process of digestion. Alexis became Beaumont s servant. As well as doing all the tasks normally expected of a servant, Alexis was also involved in a number of experiments on digestion. Beaumont collected some of the fluid that emerged from the hole in Alexis stomach and did tests on it. He could also dangle various foods by a string into Alexis s stomach and pull them out after a period of time to find out what had happened to the food in the stomach.

Zooming in on the small intestine Nutrients must pass through the walls of the small intestine and into the bloodstream. The walls of the small intestine are not smooth; they are lined with small finger-like projections called villi. This increases the surface area through which nutrients can diffuse across the walls of the small intestine. There are also many small blood vessels called capillaries associated with the villi. These transport the nutrients away from the intestines.

Small finger-like projections called villi line the walls of the small intestine.

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Coeliac disease is a condition where the villi of the small intestine are damaged. People with coeliac disease are intolerant to gluten, a substance found in wheat, oats, barley and rye and the numerous food additives made from these. If they eat foods containing gluten, the villi in their small intestines become damaged over time. This means that they can no longer absorb certain nutrients properly. An early symptom of coeliac disease is anaemia (low blood iron levels) as iron absorption is reduced by the damaged villi. Some coeliac sufferers may also experience stomach pains and bloating after eating foods containing gluten. It is possible for coeliac disease to develop in childhood, but many people do not develop it until their thirties or later. Scientists are not sure why. Perhaps certain triggers are needed for the disease to develop. If coeliac disease is diagnosed in its early stages, it is reversible provided that the person completely avoids gluten for the rest of their life. This is challenging as gluten is found in so many foods including most types of bread, pasta, cakes and biscuits. Failure to avoid gluten can have dire consequences for people with coeliac disease. Apart from feeling unwell and being deficient in certain nutrients, coeliac sufferers who do not follow a gluten-free diet also have an increased risk of developing bowel cancer.

Activities

3 Complete the following sentences.

REMEMBER 1 Match the following words with their definitions: oesophagus, gall bladder, liver, digestion, stomach, small intestine, epiglottis, rectum, peristalsis. (a) The process of breaking food down into particles that are small enough to pass through the walls of the intestines (b) The tube that joins the mouth to the stomach (c) Muscular contractions that move food along the digestive tract (d) A flap of tissue that blocks the entry to the lungs when you swallow (e) The organ that produces bile (f) Where the digestion of protein begins (g) Where bile is stored (h) Where fat is broken down (i) Where faeces is stored until it can be released 2 Copy and complete the table below for each of the organs labelled in the diagram below.

Organ Function

Involved in physical or chemical digestion or both

When food is digested, some of the substances in the food end up in the _________ __________. Other substances, such as fibre, cannot be broken down completely and are ___________ out of the body in the form of ___________. 4 Describe coeliac disease.

THINK 5 Explain why the food you eat needs to be digested. 6 If you stand on your head and take a bite of a chocolate bar, can you still swallow it? Explain why. 7 Beaumont’s experiments on Alexis St Martin raise some ethical issues. (a) Define the word ‘ethical’. (b) Justify why Beaumont’s experiments would be seen as unethical by some people. (c) Do you think Beaumont could do such experiments today? Explain your answer.

IMAGINE 8 Imagine that you are a cheese and salad sandwich. You have just been eaten. Write a story to describe your passage through the digestive system from the mouth to the anus. 9 Imagine that one of your friends has coeliac disease. Design a dinner and breakfast menu that you could serve to your friend if she was coming over for your slumber party.

DESIGN AND CREATE

A

B

10 Design a poster of the digestive system to explain to year 3 students how food is digested. eBook plus

G H

C D E F

Damaged intestinal villi, leaving holes on a flattened wall

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11 Test your knowledge of the digestive system by completing the Digestive jigsaw interactivity in your eBookPLUS. int-0216 work sheet

14.4 The digestive system

14.6

Mechanical digestion Mechanical digestion involves physically breaking food down by cutting, grinding or churning it. The teeth do most of the mechanical digestion. In humans, the front teeth cut the food and the back

teeth grind it. When food is chopped up into small pieces, there is a larger area of the food exposed. This allows the chemicals produced by the digestive system to work on the food more effectively.

Teeth Humans have four different types of teeth. Each type has a different shape, position in the mouth and job in breaking down food. Molar You have between eight and twelve molars, depending on your age. The last four molars are known as your wisdom teeth; they usually appear at the age of 17 or older. Molars grind food. They have between three and five cusps. The rough cusps help to break down the food.

Incisor Incisors are spade shaped. They have a straight, sharp edge for cutting and biting food. You have eight incisors in total four on both the upper and lower jaw at the front of the mouth.

Canine There are four pointed canines one on each side of the incisors. They are used for shearing and tearing through tough food.

Premolar Premolars roll and crush food. There are eight premolars two next to each canine. They have two pointed cusps to help break down food.

structure of a tooth Although different in size and shape, all teeth are made up of the same material.

Gum Gum surrounds the tooth, stopping food particles getting into the root.

Enamel Enamel is the hardest substance in the body. It forms a coating over the exposed surface of the tooth.

Pulp The pulp contains the nerves and blood vessels.

Dentine Dentine (sometimes spelled dentin) makes up most of the tooth. It is a bone-like material that gives the tooth its shape. Dentine is not strong and wears away if exposed.

Root canal The root canal is the channel where the nerves and blood vessels go down into the jawbone.

Bone Teeth are locked into the bone of the jaw.

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What do they eat?

InveStIgatIon 14.3

Herbivore (wombat)

How well do you brush your teeth?

Herbivores eat plants. They have large incisors for biting and cutting. Herbivores do not have canines. They have large premolars and molars because the fibrous plant material needs a lot of grinding.

You will need: 3 nutrient agar plates 3 small labels 3 cotton buds sticky tape

toothbrush toothpaste incubator set at 35 C dissection microscope

Note: This is best done after lunch, prior to cleaning teeth. ◗ Label the three agar plates as Dirty , Toothpaste and

Brush only .

carnivore (Tasmanian devil) Carnivores eat other animals. Because their prey is alive and moving, they have large canines for stabbing and holding on to it. Their incisors are used for tearing m eat. The molars and premolars in carnivores have cutting edges.

omnivore (human) Omnivores eat both plants and animals. They have all of the different types of teeth needed to break down both meat and plants.

◗ Wipe a cotton bud

carefully over your uncleaned teeth and gums. ◗ Gently wipe in a

zigzag pattern over agar plate labelled Dirty . ◗ Replace the lid

and seal around the edges with sticky tape. ◗ Repeat the steps above after brushing with no

toothpaste and then with toothpaste. ◗ Incubate agar plates for 24 48 hours. ◗ Observe the agar plates using the dissection

microscope. Do not open agar plates. Observe through the plastic dish.

Insectivore (numbat) Insectivores are carnivores that eat only insects. Their teeth are small and pointed so that they can crush the exoskeleton of the insect. Insects are then swallowed whole.

activities REMEMBER 1 Define the term mechanical digestion . 2 Identify the four types of teeth and their function. 3 Define the terms carnivore , omnivore and herbivore . 4 Explain why it is important to break food down into small pieces.

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DIscussIon 1

Sketch the three agar plates, showing any growth.

2

Which agar plate had the most growth? Why?

3

Why should we brush our teeth with toothpaste?

THInK 5 Justify why herbivores do not have canines. 6 Describe what would happen to your teeth if they did not have enamel covering them. 7 How do we know what dinosaurs ate when all we have is their fossilised bones? 8 Modify Investigation 14.3 to test the following hypothesis: Mouthwash prevents the growth of bacteria that cause tooth decay.

14.7

Chemical digestion Once the food has been broken down into small pieces, chemicals called enzymes can get to work on the food particles. There are many types of enzymes in the body. Those involved in digestion break down the complex chemicals found in food into small molecules that can pass through the walls of the small intestine and into the bloodstream.

Enzymes Enzymes are special chemicals that speed up the chemical reactions in your body. The enzymes themselves do not change and can be reused over and over. So, only a very small amount of an enzyme is needed. Each enzyme has its own special shape, just as a key has a special shape. Enzyme ‘keys’ can fit into food particles just as a key fits

into a lock. And, like a key fitting a lock, each enzyme can ‘fit’ into only one type of substance. If an enzyme matches a food particle, the food particle breaks apart. There are hundreds of enzymes working in your body. The digestive enzymes are only one group. Enzyme locks onto food particle.

Food particle (top) and free enzyme

Enzyme is unchanged and can repeat the process on another food particle.

Enzyme breaks the food particle into smaller pieces.

Some enzymes of the human digestive system Amylase Amylase Amylase Amylase Starch molecule (chain of glucose molecules)

Amylase enzymes cut starch into glucose molecules. Glucose molecules

Wall of small intestine

Amylase is made in the salivary glands, pancreas and small intestine. It works in the mouth and small intestine to break down starch into simple sugars such as glucose.

Protease Protease is made in the stomach, pancreas and small intestine. It breaks down protein into amino acids. It works in both the stomach and the small intestine.

Lipase Glucose in bloodstream Amylase enzymes break down starch into glucose molecules, which can diffuse across the wall of the small intestine.

Lipase breaks down fats and oils into fatty acids and glycerol. It is made in the pancreas, and lipids are digested in the small intestine.

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Fat stuff Breaking down lipids, such as fats and oils, is hard work! Because lipids are insoluble in water, they tend to clump together into large blobs. A substance called bile helps solve this problem. Bile is produced by your liver and stored in your gall bladder. As half of the bile molecule is attracted to water and the other half is attracted to lipids, it helps to emulsify or separate the lipids so the lipase enzymes can gain access to them and do their job. This is an example of mechanical digestion (bile) and chemical digestion (lipase) working together to get the job done!

376

Bile emulsifies fat so that lipases can break it down.

High or low GI?

Glycaemic index

Extremely high

You might have noticed that some foods are labelled as low GI. The GI or glycaemic index of a food is a measure of the time it takes for your blood sugar level to rise after you eat that food. Foods that are high in sugar, and starchy foods that are low in fibre, can be digested quickly by amylase. These foods have a high GI and they provide only a short burst of glucose. As your blood glucose level drops, you may start to feel hungry again. Foods with a low GI are digested more slowly. Blood glucose levels rise more slowly and over a longer period of time, so you feel full for longer. Choosing low GI foods might help maintain a healthy weight and perhaps also prevent certain diseases such as type II diabetes. The table above indicates the glycaemic index of a range of foods. The graph at right shows the blood glucose spike and drop that occur after eating high GI foods, and the more moderate, longer lasting rise in blood glucose level after eating low GI foods.

Grains

Puffed rice Wholemeal Cornflakes bread White bread Muesli Brown rice Porridge oats

Bran Rye bread White pasta Brown pasta

Tomato soup Barley Lima beans

Fruit and vegetables

Parsnip Baked potato Carrot

Sweet corn Mashed potato Boiled potato Apricots Bananas

Sweet potato Peas Baked beans Grapes Orange juice

Pears Apples Oranges Apple juice

Red lentils Soybeans Peaches Plums

Sugar

Glucose Honey

Sucrose Potato chips Sponge cake

Yoghurt High-fat ice-cream

Peanuts

Core Science | Stage 4 Complete course

Snacks

Corn chips Chocolate Crackers Biscuits Low-fat ice-cream

8 Blood glucose (mmol/L)

Moderately high

High

Moderately low

Low

High GI (e.g. chocolate)

7

Low GI (e.g. peanuts)

6

5 0

50 100 Minutes after intake

150

Foods with a high GI, such as chocolate, cause a sharp rise in blood sugar. Foods with a low GI, such as nuts, result in a more moderate but longer lasting rise in blood sugar.

taken to set. If the milk has not set after 15 minutes, record the time as 15+.

beaker 3 and boiling water (from a kettle) for beaker 4. These are the water baths .

InveStIgatIon 14.4 Does temperature affect enzymes?

◗ Half-fill four test tubes with milk and

You will need: 4 beakers 8 test tubes milk 4 thermometers fresh pineapple puree (Fresh pineapple can be pureed using a food processor. If fresh pineapple is not available, use junket powder or a junket tablet dissolved in 10 mL water.) ◗ Add water to the beakers so that

they are two-thirds full. Use cold tap water and ice for beaker 1, cold tap water for beaker 2, hot tap water for

◗ Copy and complete the table of

results below.

put one test tube in each water bath. ◗ Place one teaspoon of fresh

Temperature of milk and pineapple mixture ( C)

pineapple puree (or 1 mL junket solution) in the other four test tubes. Put one of these test tubes in each water bath. ◗ Allow the test tubes to stand in the

water baths for at least 5 minutes.

DIscussIon 1

Pineapple juice and junket contain an enzyme that causes a protein in milk (casein) to undergo a chemical reaction and change texture; that is why the milk sets. At what temperature did the enzyme work best? Explain your answer.

2

Did the enzyme work well at very high temperatures? Explain your answer.

3

Which variables were controlled in this experiment?

4

Do you think that the same results would be obtained if tinned pineapple puree was used instead of fresh pineapple? Explain your answer.

◗ For each water bath, pour the

fresh pineapple puree into the milk and stir briefly. Quickly record the temperature of the milk and pineapple mixture and then allow it to stand undisturbed. The mixture will eventually set. Record the time

Pineapple puree Pineapple puree Milk

Milk

Iced water

Room temperature water

Warm water

activities REMEMBER 1 Define the term chemical digestion . 2 Describe the function of enzymes. 3 Identify the three main digestive enzymes, where they are made and the type of substance they break down. 4 Describe what happens to enzymes when they get very hot. 5 Describe how bile helps lipase enzymes get their work done.

THInK 6 Explain why the food you eat needs to be chemically digested. 7 When you eat a piece of bread, nothing much can be tasted at first. As you continue to chew,

Boiled water

After 5 minutes, combine milk and pineapple puree and return to water bath.

a sweet taste can be detected. Explain why. 8 It is sometimes necessary, for medical reasons, to remove the gall bladder. The gall bladder stores bile. Justify why a person who has had their gall bladder removed might need to follow a low-fat diet. 9 Study the table on page 376. (a) Identify the types of foods that have an extremely high GI. Are there any general trends? (b) Deduce how the fat content of a food affects its GI. (Hint: Look at where the high-fat foods are in the table.) (c) High-fat ice-cream has a lower GI than low-fat ice-cream. Discuss whether it is healthier. 10 Amylase breaks starch down into glucose. Iodine solution turns

Time taken to set (min)

blue-black when it is added to starch, but it is a light brown colour when starch is not present. (a) Jossie combined 10 mL of starch solution with 1 mL of amylase solution. She removed a small amount of the mixture and added iodine solution. The iodine solution turned blueblack. Half an hour later, Jossie removed another small amount of the mixture and tested it with iodine solution. This time the iodine remained light brown. Explain Jossie s observation. (b) Design an experiment to test the hypothesis that amylase is more active (converts starch to glucose faster) at 50 C than at 20 C. work sheet

14.5 Mechanical and chemical digestion

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14.8

Bodies on the move Muscles use the energy from food to enable us to move. They move the bones they are attached to, allowing us to walk, run, lift objects and perform fine movements such as those involved in writing. Together, muscles and bones form the musculoskeletal system, the system responsible for body movements.

Muscles Muscles are tough and elastic fibres. You have muscles to make your heart pump, muscles to help you digest food and muscles to help you breathe. Many muscles, however, are joined to bones. Muscles pull on bones by contracting, or shortening. Muscles never push. The movement of muscles is controlled by the brain, which sends signals through your nerves. Muscles such as those that make your heart pump and those that control your breathing are called involuntary muscles. They work without you having to think. The muscles that are connected to bones are called voluntary muscles because you have to choose to use them. In animals without bones, such as worms and slugs, the muscles bring about movement by stretching and shortening certain parts of the body. It can be quite an effective way to move in water. Squid and jellyfish, for example, can propel themselves reasonably quickly in water even though their muscles are not attached to hard parts. They achieve this by pumping water

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into body cavities and releasing it suddenly to provide thrust. On land, this option is not available. To achieve high speeds on land, it is necessary for muscles to be anchored to something rigid. Insect muscles are attached to a layer of tough material on the outside of their bodies. This layer is called the exoskeleton. It is made of a substance called chitin. The diagram below shows how insects can move by contracting and relaxing their muscles.

Shoulder joint

Scapula Humerus

Biceps Ulna Triceps

Radius

Elbow joint Triceps contract Biceps relax

Biceps contract Triceps relax

When your biceps contract, your arm bends upwards. When your triceps contract, your arm straightens.

Exoskeleton (cuticle) Joint Extensor muscle

Flexor muscle

The muscles in insects are attached to the exoskeleton, the outer covering of the body. This grasshopper can extend its leg by contracting the extensor muscle and relaxing the flexor muscle.

There are more than 200 bones in the skeleton of an adult human. Apart from providing a rigid structure for muscles to attach to, thus allowing you to move, the skeleton also has two other important functions. The skeleton provides support and forms a frame that gives your body its basic shape. Without a skeleton, you would be a jelly-like blob.

Bones In humans and other vertebrates (animals with a backbone), the muscles are attached to bones inside the body by bundles of tough fibres called tendons. The muscles move the bones by contracting and relaxing.

Certain bones of the skeleton also protect vital organs. For example, the brain is protected by the bones of the skull, and the heart is protected by the rib cage.

Skull (cranium)

InveStIgatIon 14.5 Rubbery bones

Lower jaw (mandible)

Collarbone (clavicle)

Breastbone (sternum)

Ribs

Spine (vertebrae)

Pelvic girdle

You will need: 2 chicken or turkey bones 2 jars vinegar ◗ Clean the two chicken or turkey bones and leave

them to dry overnight. Place one bone in a jar of vinegar and the other in a jar of water. ◗ Allow the bones to soak for at least three days. Then

remove the bones and observe any changes. Thighbone (femur)

Kneecap (patella)

Vinegar is an acid and dissolves minerals such as calcium and phosphorus compounds, removing them from the bone. ◗ Return the bone to the jar of vinegar for another

week, then remove and observe any further changes in the bone. Try to tie the bone in a knot.

Shinbone (tibia)

DIscussIon

What s in a bone? Long bones, such as the shaft of the femur (in your thigh), have an outer layer of hard, strong compact bone that covers an interior of spongy tissue containing the bone marrow. Some of the most important parts of your blood are made in the bone marrow. Some other bones in your body, such as the head of the femur, are made up of lighter spongy bone, which is more open in structure than compact bone. Bones are alive. They contain living cells and need a blood supply to provide oxygen and other nutrients. If bones were not alive, how would you grow taller? How would a broken arm or leg mend? Hard covering of compact bone: includes calcium and phosphorus

Bone marrow

Spongy tissue

The structure of a bone

Your bones cannot remain hard without an adequate supply of two important minerals: calcium and phosphorus. In fact, until you reach the age of about 20, the soft cartilage that made up your skeleton when you were born is being gradually

1

What changes occurred in each of the two bones?

2

How did the bone change after more than a week in vinegar?

3

Why was the jar of water used in the first part of this experiment?

replaced. Cartilage is very soft and rubbery, not as hard and solid as bone. The hardening of your bones as you get older is called ossification. After ossification, the bone is made up of about 70 per cent non-living matter and 30 per cent living matter. As you get old, your bones may get dry and brittle. That is why older people break their bones more easily. Not all cartilage changes into bone. The ends of your bones remain covered in cartilage. Your trachea (windpipe), nose and ears are made mostly of cartilage. Investigation 14.5 above shows what could happen to your bones without a supply of important minerals.

Joints A joint is where two bones meet. The elbow and knee are examples of joints. At a joint the bones are held together by bundles of strong fibres called ligaments. The ends of each bone are covered with cartilage. The cartilage is covered with a liquid called synovial fluid. Together, the cartilage and synovial fluid stop the bones from scraping against each other.

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Slippery cartilage where bones rub together

Synovial fluid

Bone Bone marrow

Ligament

The region where bones meet is called a joint.

Most joints allow your bones to move. The amount and direction of movement allowed depends on the type of joint. (a)

(b)

Humerus

Pelvis (c)

(d)

Broken bones

Radius

Hinge joint

When a bone breaks, the ends of the bone need to be put back into place (set), so that they can grow together. If a bone is shattered into several pieces, it is sometimes possible to use pins or wire to hold the pieces in place while the bone heals. A greenstick fracture occurs when the bone cracks but does not break. Greenstick fractures are common in children because the bones are more flexible.

Ulna Head of femur

Socket

Ball

Pivot

Hinge

Socket

Different types of joints: (a) pivot joint, (b) hinge joint, (c) ball and socket joint, (d) immovable joint

osteoporosis

The knee and elbow are hinge joints, like those in a door. They allow movement in only one direction. The hip and shoulder joints are ball and socket joints. They allow movement in many directions.

Osteoporosis is a loss of bone mass that causes bones to become lighter, more fragile and easily broken. It occurs in middle-aged

joint from one end of the muscle to the other. Try pulling on the muscle. Can you get the bones to move by pulling on the muscle?

InveStIgatIon 14.6 chicken wing dissection You will need: chicken wing scalpel scissors dissection tray or board newspaper disposable gloves

◗ Use scissors to cut through the joint. As you do so, look

for tendons and shiny white cartilage.

DIscussIon 1

Sketch one of the joints in the chicken wing. Label the bones, the tendons and the muscles. Show clearly where the muscle inserts (attaches to the bones). Use arrows to show how the bones move when the muscle is shortened.

2

Feel the cartilage with a gloved hand. Does the cartilege feel rough or slippery? Why does it need to be slippery?

3

Is cartilage harder or softer than bone?

◗ Using the scissors and scalpel, gently pull away the skin

from the chicken wing. Put the tip of the scalpel blade between the skin and the muscle to separate the skin from the muscle. ◗ When you have completely removed the skin from one

joint, inspect it carefully. Follow each muscle near this

380

The joint between your skull and spine is a pivot joint. It allows a twisting type of movement. Some joints, such as those that join the plates of your skull, do not move. Such joints are called immovable joints. While not allowing movement, these joints provide a thin layer of soft tissue between bones. Their job is to absorb enough energy from a severe knock to prevent the bone from breaking.

Core Science | Stage 4 Complete course

or elderly men and women. In Australia, about 60 per cent of women and about 30 per cent of men are affected in some way by osteoporosis. It is believed to be caused by a lack of calcium in the diet. Insufficient exercise is also an important factor in the development of osteoporosis.

In your teen years, you can help protect yourself from getting osteoporosis later by having a healthy diet. It should include dairy products such as milk, cheese and yoghurt and other foods high in calcium. Such a diet will help ensure that your bone mass is adequate as an adult. 9 Describe why our skeleton isn t made of just one bone.

activities

10 Explain why it is that, in a similar accident, an adult gets a broken bone while a child may suffer only a greenstick fracture.

REMEMBER 1 Cover up the diagram of the human skeleton on page 379 and test your memory of the names of some of your important bones by completing the table below. Scientific name

11 Find out where in the human skeleton the following bones are. (a) Humerus (b) Fibula (c) Coccyx (d) Scapula

Common name

Vertebrae Skull

12 The muscles in your food pipe contract and relax to push food down into your stomach. Are these muscles voluntary or involuntary muscles? Explain your answer.

Clavicle Breastbone Mandible Thighbone

13 Describe what would happen if the cartilage in your knee joint wore out.

Patella Shinbone

cREATE

2 Describe the job done by each of the following parts of a joint. (a) Ligament (b) Cartilage (c) Synovial fluid

14 construct a skeleton mobile to hang from the ceiling. (a) Trace the skeleton diagram on page 379 (or a larger one from another book), colour it and cut it into a number of sections. (b) Paste each section onto cardboard and thread the sections together to make a skeletal mobile.

3 Some joints are referred to as immovable joints. What is the use of having joints that don t move? 4 Identify an example of each of the following types of joint. (a) Hinge (b) Ball and socket (c) Pivot (d) Immovable

work sheet

14.6 Bones, joints and muscles

5 Ligaments and tendons are bundles of tough fibres. Identify the major difference between a ligament and a tendon. 6 Describe the action of the biceps and triceps muscles as you bend your elbow to raise your forearm. 7 Recall which organs the skull and rib cage protect.

THInK AnD InVEsTIGATE 8 Look carefully at each of the skeletons at right. Three of them are incomplete. Identify which skeletons are incomplete and name the missing parts.

A

B

C

D

E

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14.9

getting rid of waste The human body takes in substances including food, water and oxygen. It also needs to get rid of unwanted substances that are produced by the body. A number of organs are involved in getting rid of waste, including the lungs, the liver, the skin and the organs that make up the excretory system. Many of the chemical reactions that occur inside cells produce toxic waste products. If our bodies could not get rid of these we would die. Excretion involves the removal of these harmful substances from the body. Carbon dioxide, produced in respiration, is excreted via the lungs; we breathe

Vena cava

it out. Our skin excretes some salts and water in the form of sweat. Another harmful substance we need to excrete is urea. It is produced from the breakdown of proteins. The kidneys remove urea from the blood. If you put your hands on your hips, your kidneys are close to where your thumbs are. You have two of these reddish-brown, beanshaped organs. Without them you would survive only a few days. Kidneys play an important role in filtering your blood. About a quarter of the blood that your heart pumps is sent to your kidneys. These small organs filter about 50 litres of blood each hour. As blood passes through the

kidneys, the urea and some other harmful substances are removed. Other substances, like salts and water, which may be in excess, can also be removed. This keeps their concentration in the blood constant. If this did not occur, your cells would not work properly. Urine is produced by your kidneys. This watery fluid contains unwanted substances. Tubes called ureters transport urine from your kidneys to your bladder to be stored temporarily. As it fills, your bladder expands like a balloon. It can hold about 400 mL of urine. Urination occurs when urine moves from your bladder through a tube called the urethra and out of your body.

Aorta Renal artery

Kidney: filters the blood and produces urine.

Renal vein

Ureter: transports urine from kidney to bladder.

Bladder: stores urine.

Urethra: transports urine from bladder to outside body. The excretory system

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Blood, water and urine Both blood and urine are mostly made up of water. Water is very important because it assists in the transport of nutrients within and between the cells of the body. It also helps the kidneys do their job because it dilutes toxic substances and absorbs waste products so that they may be transported out of the body. A comparison of what is found in the blood and the urine. How are they different? Quantity (%) Substance

In blood

Water

In urine

92

95

Proteins

7

0

Glucose

0.1

0

Chloride (salt)

0.37

0.6

Urea

0.03

2

Too much or too little The concentration of substances in the blood is influenced by the amount of water in it. If you drink a lot of water, more will be absorbed from your large intestine and the kidneys will produce a greater volume of dilute urine. If you do not consume enough liquid, you will urinate less and produce more concentrated urine. Freshwater fish: rarely drinks. Fluid

Water in through gills

Lots of dilute urine Saltwater fish: drinks sea water. Fluid H2O

Which type of fish rarely drinks?

Water leaves via gills.

Little urine

Fish maintain their salt and water balance in different ways, depending on whether they are freshwater or saltwater fish. Have you ever noticed that putting salt on vegetables such as eggplants draws the water out of the vegetables? Something similar happens to fish living in sea water, such as snapper. Because the salt concentration is higher outside their bodies than inside their bodies, they tend to lose water through their skin. They need to drink sea water constantly to ensure they do not dehydrate and they only produce small amounts of very concentrated urine. The situation is reversed for freshwater fish, such as Murray cod. The salt concentration is higher inside than outside their bodies, so water tends to diffuse into their bodies. They need to get rid of this water so they produce large amounts of very dilute urine, and they rarely drink.

The human kidneys remove excess salt from the blood to help keep levels constant. Different types of animals have other ways of removing excess salt from their bodies. Turtles, for example, have salt-secreting glands behind their eyes. Hence you may see a turtle shedding tears . Penguins, on the other hand, may appear to have runny noses because that is where their salt-secreting glands are located.

Getting rid of alcohol Drinking excessive amounts of alcohol is linked to many health risks. The part of the digestive system that is most affected by alcohol is the liver. When alcohol enters the liver, it breaks down the alcohol into energy and the waste products carbon dioxide and water. The carbon dioxide is released through the lungs, and water leaves the body as urine, sweat and breath vapour (this is why people who drink too much can smell of alcohol ). If you drink alcohol faster than the liver can break it down, the alcohol that is not eliminated is absorbed in the body and you become intoxicated. The liver works at a fixed rate and can detoxify about one standard drink each hour. So coffee, cold showers, fresh air and vomiting do not speed up the process of getting rid of alcohol from your body. Alcohol also affects the amount of urine produced by the kidneys. It reduces the body s production of a hormone that keeps urine concentrated. The kidneys produce more urine than usual, instead of reabsorbing water into the body. As a result, you urinate more and can become dehydrated. In extreme cases, a heavy drinker can lose so much water that the body cannot function properly.

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People with kidney disease may not be able to remove the waste materials from their blood effectively. They may be linked up to a machine that does this job for them. Their blood is passed along a tube that lets wastes, such as urea, pass out of it. However, useful substances, such as glucose, proteins and red blood cells, stay in the tube and are kept in the blood. This process is called haemodialysis.

Dialysate Blood cell

Waste products Dialysis tubing Vein Blood pump

Radial artery

Dialysis tubing

Compressed CO2 and air Bubble trap

Fresh dialysing solution

Constant temperature bath

Dialysing solution

Used dialysing solution

Haemodialysis

activities REMEMBER 1 Define the term excretion . 2 Draw and label a diagram of the excretory system showing the following: renal arteries, renal veins, ureters, bladder, urethra. 3 What do blood and urine have in common? 4 outline what happens when you drink a lot of water. 5 Describe one way in which excess salt is removed from your body. 6 Explain how haemodialysis can assist people with kidney disease.

THInK 7 Look carefully at the diagram of haemodialysis and suggest reasons why the following are included in the process: (a) blood pump (b) bubble trap (c) constant temperature bath. 8 Identify what you would expect to find in the used dialysing solution. 9 Explain why red blood cells don t pass through the dialysis tubing. 10 compare dialysis with the way a real kidney works.

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AnALYsE AnD EVALuATE 11 Use the table on the previous page and the other information on pages 382 3 to answer the following questions. (a) construct two divided bar graphs to show the quantity of water, proteins, glucose, salt and urea in blood and in urine. (b) Identify which substance is in the greatest quantity. Suggest a reason for this. (c) Identify the substances found only in blood. (d) Identify the substances found in urine in a greater quantity than in blood. Suggest a reason for this. (e) Explain why the concentration of urea in the urine may vary throughout the day.

InVEsTIGATE 12 Research and report on one of these conditions: urinary incontinence, kidney stones, dialysis, kidney transplants, cystitis. 13 Find out: (a) the differences between the urethra in human males and females (b) why pregnant women often need to urinate more frequently (c) how the prostate gland in males may affect urination in later life (d) which foods can change the colour or volume of urine (e) which tests use urine in the medical diagnosis of diseases.

LooKIng BaCK 1 Complete the table below to summarise what you know about some of the substances in food. Nutrient Carbohydrates Fats and oils Proteins Vitamins Minerals Fibre

Why is it needed?

In which foods is it found?

5 What useful purpose do the bacteria in your large intestine serve? 6 List three digestive enzymes and outline the substances that each enzyme breaks down. 7 Describe the features of the small intestine that make it suitable for absorbing food particles. 8 Explain why we would die if our kidneys stopped working. 9 Describe what happens to a piece of meat after it is eaten. Include information about what happens after the amino acids have entered the bloodstream and how the waste ammonia produced is removed from the body.

2 (a) What is the purpose of digestion? (b) Explain the difference between mechanical and chemical digestion. 3 Identify the name and role of the organs marked in the following diagram of the human digestive system.

(a)

TEsT YouRsELF 1 What is the main role of proteins in the diet? A Proteins are a source of essential fatty acids. B Proteins are a source of important vitamins and minerals. C Proteins are broken down to produce glucose, which is needed for respiration. D Proteins are broken down into amino acids, which are needed for growth and repair and to make important molecules including enzymes. (1 mark) 2 In which part(s) of the digestive system does mechanical digestion occur? A Mouth only B Mouth and stomach C Mouth and small intestine D Small intestine and large intestine (1 mark)

(b)

(d)

(e) (f)

(c)

3 Which of the following is not a unit used to express the amount of energy in food? A Kilowatt B Kilojoule C Calorie D Joule (1 mark) 4 Which organ removes urea from the bloodstream? A Bladder B Liver C Kidney D Urethra (1 mark) 5 Explain why you need to include fibre and water in your diet. (2 marks) 6 (a) Describe the role of teeth in the process of digestion. (b) Justify why humans have different types of teeth. (c) What are enzymes? Describe their role in digestion.

(1 mark) (1 mark) (1 mark)

7 Use your knowledge of bones and their function to explain why all large land animals have a skeleton. (1 mark) 4 Investigate what passes into the bloodstream from: (a) the small intestine (b) the large intestine.

work sheets

14.7 Body systems 2 puzzles 14.8 Body systems 2 summary

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StUDY CHeCKLISt

ICt

nutrition

eBook plus

■ explain why animals need to eat food 14.1 ■ describe how the energy content of food can be

SUMMaRY

eLessons

measured experimentally 14.1 ■ describe the roles of carbohydrate, protein, lipid, vitamins, minerals, fibre and water in the diet 14.2, 14.3 ■ describe some chemical tests for starch, glucose and protein 14.2 ■ outline some healthy eating guidelines 14.3

From dinner plate to sewerage system This video lesson explains the amazing journey of food through the human body, from dinner plate to sewerage system. Learn how our bodies release chemicals to break down food and absorb energy-giving nutrients, all without us even being aware of the process. A worksheet is attached to further your understanding.

Digestive system ■ label a diagram of the digestive system 14.5 ■ describe the function of the main organs of the digestive system

14.5

■ distinguish between mechanical and chemical digestion

14.6, 14.7

■ describe the role of teeth in digestion 14.6 ■ compare the teeth of herbivores, carnivores and omnivores

14.6

■ describe the role of enzymes in digestion 14.7 ■ investigate the effect of temperature on the activity of an enzyme

14.7

Searchlight ID: eles-0056

skeletal system

Interactivities

■ label the major bones of the human skeletal ■ ■ ■ ■

system 14.8 outline the role of the skeletal system 14.8 explain how muscles and bones work together to allow movement 14.8 describe the structure of bones 14.8 identify examples of hinge, pivot and immovable joints in the body 14.8

A healthy diet This interactivity looks at the nutrient contents of different foods and challenges you to test your ability to identify common foods that are high in certain nutrients. Instant feedback is provided. Searchlight ID: int-0214 The digestive jigsaw This interactivity looks at the jigsaw puzzle that is the digestive system. Test your knowledge by re-creating the human digestive system. Instant feedback is provided.

Excretory system ■ explain why excretion of waste is essential 14.9 ■ label a diagram of the excretory system 14.9 ■ describe the roles of the main organs of the excretory system

14.9

■ account for the different ways in which freshwater and saltwater fish solve the problem of water balance 14.9

14.9

■ define the term haemodialysis

current issues, research and development ■ summarise information about the work of dietitians

14.4 Searchlight ID: int-0216

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15

Ecology

Rock pools, like the one in this photo, can be seen at low tide on rock platforms. They are like underwater gardens, teeming with different types of seaweed and all sorts of small animals. The organisms that live in rock pools are ideally suited to their environment and interact with both their environment and each other. Ecology is the study of these interactions.

In this chapter, students will: 15.1 ◗ learn about the biotic and abiotic

features of ecosystems 15.2 ◗ measure abiotic factors of

ecosystems and estimate the abundance of organisms 15.3 ◗ learn about the types of relationships

that exist between different species 15.4 ◗ learn about food chains and food

webs 15.5 ◗ learn about the role of decomposers

in ecosystems 15.6 ◗ learn about the carbon cycle and

global warming 15.7 ◗ learn about the effect of bushfire on

Australian ecosystems and some adaptations of Australian animals and plants to their environments 15.8 ◗ learn about the effect of drought and

flood on Australian ecosystems 15.9 ◗ learn about the work of Australian

environmental scientists.

The organisms that live in habitats, such as this rock pool, interact with the environment and each other.

15 Ecology a personal environmental-impact assessment 1. Everything we do affects the environment in some way. Complete the following survey to see how your impact on the environment compares with that of other people in your class. Circle the response that most closely represents your lifestyle. R = rarely S = sometimes U = usually Food consumption and packaging

Water I limit my showers to five minutes or less.

USR

I have a water-saving shower head.

USR

I have the tap turned off when brushing my teeth.

USR

I water the garden after dark or not at all.

USR

My house has access to a rainwater tank.

USR

I use scented, coloured or pictured toilet paper.

RSU

The environment I treat living things with respect.

USR

I discuss environmental issues with my friends.

USR

When shopping, I take my own bags.

USR

I plant some trees every year.

USR

My family grows some of its own food.

USR

I make an effort to improve my environmental habits.

USR

I compost food waste.

USR

My family buys organic foods.

USR

I avoid snacks that have a lot of packaging.

USR

I eat at fast-food restaurants that use a lot of packaging.

RSU

Personal environmental-impact score: ____________

Household energy and supplies I turn off electric lights and appliances when no-one is in the room.

USR

I decide what I want from the refrigerator before opening it.

USR

I keep windows and doors closed while heating or cooling my house.

USR

I avoid using a clothes dryer.

USR

In my home we have energy-saving light bulbs.

USR

I use airconditioning in summer.

RSU

I use facial tissues.

RSU

Transport I regularly walk or ride a bicycle to school.

Scoring Add up the number of points for each section. If the first letter is circled, it is worth 0; the middle letter is worth 2; the last letter is worth 5.

USR

Recycling and reusing I recycle aluminium, paper, glass, plastic bottles and steel cans.

USR

I use both sides of a sheet of paper.

USR

If I am out somewhere and buy a drink, I carry the container home to recycle it if there is no recycling bin available.

USR

I have a reusable lunch box.

USR

I use plastic shopping bags.

RSU

A high score means you use more resources, produce more waste and have a greater impact on the Earth. Your eco-footprint would be large. Compare your score with other class members and attempt to work out why your score is higher or lower than other people s scores. 2. Write the following words in your workbook. As you come across each word in this chapter, write down a definition of that term in your own words. ecosystem habitat distribution abundance collaboration symbiosis mutualism parasitism commensalism epiphyte saprophyte extinct endangered consumer producer decomposer adaptation respiration photosynthesis eBook plus

3. Use the Ecological footprint weblink in your eBookPLUS to calculate how many Earths it would take to support your current lifestyle.

15.1

a place to call home Next time you go for a bushwalk or walk along a rock platform, take a good look around. Try to count the different types of living things that surround you. Some organisms such as trees and large animals are very obvious, but there are many smaller creatures and plants that are easier to miss. There are even The sun is the source of all life on Earth. It supplies the energy that plants use to make their food. All animals depend on the food that plants make for their energy.

thousands of microscopic animals living in the soil. The living things in natural environments, regardless of their size, depend on each other and on their surroundings for survival. Ecology is the study of the way in which organisms interact with other organisms and with their environment.

Animals depend on trees and plants. Trees and plants provide food (fruit, flowers and seeds) and a home for many insects and animals. Plants also make some of the oxygen that we need to breathe.

Many plants and animals have relationships that help each other. In this example, a bee is pollinating a flower so that the flower can make seeds. The seeds will grow into new plants.

Animals depend on rocks for shelter and a safe home away from those who may want to eat them. Lizards also sit on rocks in the sun to get warm.

Animals depend on other animals for food. This is just another part of the web.

Water is essential to all life. Animals and plants are mostly made up of water. Amazingly, your own body is made up of about 70 per cent water! Some animals and plants also live in water.

Many animals, like ants and worms, live in the soil. Worms also use the soil as their food. Plants can get nutrients from the soil through their roots. They also use the soil to support themselves.

Humans are animals too. Often we think we are not, but we depend on the web of nature just like all other animals.

15 Ecology 389

it s all about relationships An ecosystem is made up of living and non-living things that interact with each other. A pond, a rock platform and a rainforest are all examples of ecosystems. The living things in an ecosystem (the organisms) are the biotic factors. The non-living features are the abiotic factors. Abiotic factors include temperature, soil pH and amount of available light. The abiotic factors determine the types of organisms that can survive in an area and, in turn, the living things affect the abiotic features of an ecosystem. The living things also interact with each other. A habitat is the place where a particular organism lives. For example, the habitat of the platypus is freshwater creeks, rivers and lakes of eastern Australia. The rock pool shown below is a habitat for many species. A habitat must provide the things that animals and plants need to stay alive. For example, organisms living in this rock pool, and other habitats, need: • food • clean water • shelter • space • a mate for reproduction • gases, like oxygen and carbon dioxide.

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The distribution of a species tells us where it is found, whereas the abundance or density of a species tells us how many of these organisms live in a particular area. For example, the Sydney funnel-web spider (Atrax robustus) is found in New South Wales, from Newcastle to Nowra and west to Lithgow. That is its distribution. There are more funnel-web spiders in the Hornsby area than in the Parramatta area, so we can say that the abundance or density of funnel-web spiders is higher in the Hornsby area than in the Parramatta area.

Sydney funnelweb spider

gaia A biologist named Professor James Lovelock developed the scientific theory of Gaia (pronounced guyah). This theory states that the Earth s physical environment and living creatures have developed together over a very long time. Trees, clouds, rivers, rocks, air, animals and plants are all separate. But together they are also a super-organism. Gaia is named after the mythical Greek goddess of Mother Earth. We are all part of this giant organism. Each environment makes up an important part of it. The forests are like skin. They sweat to keep us cool. The rivers and oceans are like blood. They carry supplies such as nutrients and dissolved oxygen, and wash away wastes. The air is like lungs. The rocks, strong and solid, are like bones. What hurts one part of the Earth, hurts it all. What helps one part of the Earth, helps it all.

The earth is alive! australian aboriginals have traditionally believed that the whole earth is living. They believe that animals and plants are not any different from the rocks, mountains, sun, fire, water or air. after all, animals and plants cannot survive without these things. The Rainbow serpent (carpet snake) is said to be the creator of life. she is responsible for the colours and shape of earth. she called spirits to make the mountains, light, water and colour that brought mother earth to life. do you think a mountain or river can be alive?

InvEstIgatIon 15.1 Lid

a mini ecosystem You will need: 1 L clear plastic bottle scissors or knife masking tape soil or potting mix small plants or seedlings grass clippings or ground mulch (including small organisms). If there are few organisms in the grass clippings or mulch, you may want to add ants or slaters.

Tape sealing the bottle

Plants ◗ Cut the top off the bottle. ◗ Pour the soil or potting mix into the

Mulch or grass clippings containing small organisms

bottom of the bottle. ◗ Plant the seedlings into the potting

mix.

Moist soil

◗ Place the ground mulch or grass

clippings over the potting mix and around the seedlings. ◗ Add sufficient water to moisten the

discUssion 1

Explain why it is not necessary to regularly water the plants in this ecosystem.

2

The living things in the ecosystem use up oxygen. (a) Recall what the living things need oxygen for. (b) Why doesn t the oxygen run out?

3

Where do the living things get their energy from? Why is there no need to feed them?

soil. ◗ Put the top back on the bottle and

seal it with masking tape. The bottle should be completely sealed so that no air, nutrients, animals or plants can be added or removed from the mini ecosystem for the duration of the experiment. ◗ Observe your mini ecosystem

each lesson for the duration of this topic.

activities RemembeR 1 define the terms ecosystem , organism , biotic , abiotic , habitat , distribution and abundance . 2 Recall two examples each of biotic and abiotic factors in an ecosystem. 3 explain why the sun is said to be the source of all life on Earth. 4 identify what a habitat needs for organisms to be able to live there.

4

If the ecosystem is balanced, the organisms inside the bottle continue to live for a very long time without needing extra water or food. (a) Explain what a balanced ecosystem is. (b) What could cause this mini ecosystem to become unbalanced?

Think 5 explain how the Earth can be likened to one giant organism. 6 Humans have a habitat too. describe your habitat.

cReaTe 7 Create a colourful poster to demonstrate how your favourite animal or plant lives in its habitat. Include information about how it gets food, water, oxygen or carbon dioxide, and the other plants or animals it needs for survival. work sheets

15.1 Ecosystems and habitats 15.2 Biotic and abiotic factors

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15.2

Investigating the environment The first step in protecting our environment is to find out as much as we can about it. That involves taking measurements. We can measure abiotic factors, such as temperature and soil pH, as well as the abundance of particular animals or plants in an ecosystem.

Why are abiotic factors important? The abiotic factors of an ecosystem affect which species can survive there. For example, most species can survive only within a certain temperature range. Emperor penguins can tolerate temperatures well below 0 C but would die if the temperature reached 40 C. Humans would not survive well below 0 C without the help of many layers of clothing. Each species has a tolerance range for each abiotic factor. The optimum range is the range within the tolerance range in which it functions best. Measuring the abiotic factors in a habitat can provide information on the abiotic requirements for a particular organism in that habitat. Can you think of features that organisms possess to increase their chances of survival in some habitats more than in others?

distribution The distribution of a species tells us where it is found. To work out the distribution of a species, scientists sometimes use a transect. This involves recording all the organisms found in a narrow strip of an ecosystem. For example, if you wanted to draw a transect of a rock platform, you could lay two parallel string lines a short distance apart from the edge of the water up to the beach. You could then walk along the string lines from the water to the beach and record all the living things you see in the narrow strip between the string lines. That would show you how the types of living things found on the rock platform change as you move away from the edge of the water.

Marker

Marker Continuous sampling

Zone of intolerance

Zone of intolerance

Number of organisms

Optimum range

Too cold! Organism cannot survive in this environment.

Too hot! Abiotic factor e.g. temperature Tolerance range This is the range in which it can survive.

Organism cannot survive in this environment.

Each species tolerates a certain range of temperatures.

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Line transects provide information on the distribution of a species in a community.

abundance The abundance of a species tells us how many of these organisms are in a particular area. Measuring the abundance of elephants in NSW would be easy. There are only a few elephants in NSW (at Taronga Zoo and Western Plains Zoo), and elephants are easy to see. If we had to measure the abundance of limpets on a rock platform, however, we would have a much harder time. Two techniques that are sometimes used to estimate abundance are the quadrat method and the capture recapture method. The quadrat method works best for species that do not move around much, such as trees and limpets. The capture recapture method is more suited to species that move, such as rabbits and fish.

Life in a square A quadrat is just a sampling area (often 1 square metre) in which the number of organisms in that area is counted and recorded. When organisms are counted in a number of quadrats, this is usually considered to be representative of the total area under investigation. The abundance of the organism in the total area can be estimated using the equation: estimated average number per quadrat × total area abundance = area of quadrat For example, some students counted the number of oysters in quadrats with an area of 0.25 m2 and found that the average number of oysters was 15. They then estimated the total number of oysters on the rock platform as follows: average of oysters per quadrat = 15 total area of rock platform = 300 m2 area of quadrat = 0.25 m2 15 × 300 estimated abundance = = 18 000 0.25

Students using quadrats to estimate the abundance of oysters

InvEstIgatIon 15.2 Using quadrats to estimate the abundance of eucalyptus trees

discUssion 1

Quadrat number

You will need: maps of environments A and B (provided by your teacher) overhead transparency sheet

Environment B

3 4

◗ Measure the length and width of each map and calculate

5

the area of each using the following equation.

Average

area = length × width 2

Estimate the abundance of eucalypts in each environment using the equation shown above.

3

Ask your teacher for the actual abundance of eucalypts in each environment. Compare your estimate with the actual abundance.

4

What could you have done to make your estimate more reliable?

◗ Close your eyes and drop the quadrat anywhere on

the map. Count how many eucalypts (crosses) are inside the quadrat. Repeat four more times. Do this for both maps.

Environment A

2

eucalyptus tree as a cross.

overhead transparency film. Calculate the area of the quadrat.

Number of eucalypts

1

◗ The maps of environments A and B show each

◗ Make a quadrat by cutting a 3 cm × 3 cm square out of

Copy and complete the table below.

15 Ecology 393

becomes slightly cloudy or turns completely white/grey. Work out the salinity of the water sample using the table below. Repeat using water sample B.

InvEstIgatIon 15.3 measuring abiotic factors You will need: water samples A and B and soil samples A and B (provided by your teacher) thermometer dropper bottle of universal indicator solution universal indicator colour chart dropper bottle of silver nitrate solution (0.1 mol/L) calcium sulfate powder

Description

discUssion 1

Copy and complete the result table below.

2

A pH less than 7 is considered acidic. The lower the pH the more acidic the sample is. (a) Which water sample was more acidic? (b) Which soil sample was more acidic?

3

One of the environments is near the ocean and so some sea water mixes with the water in the river. Was this environment A or B? Explain your answer.

4

Which of the tests in this investigation were qualitative and which were quantitative?

5

Which variables were controlled in the salinity test?

Salinity

Clear

Nil

Slightly cloudy

Low

Completely white/grey

High

◗ Put a small amount of soil

sample A on a watchglass. The soil should be slightly moist. If the soil is very dry, add a few drops of distilled water. Sprinkle some calcium sulfate over the soil. Add some drops of universal indicator over the calcium sulfate powder. Compare the colour of the powder with the colour chart and record the pH of the soil. Repeat using soil sample B.

In this investigation you will measure some abiotic factors for environments A and B. The soil samples were collected from these environments. The water samples were collected from rivers that run through each environment. ◗ Use the thermometer to measure

the temperature of each water sample and each soil sample. ◗ Pour 5 mL of water sample A

into a test tube. Add 3 drops of universal indicator. Compare the colour of the water with the colour chart and record the pH of the water sample. Repeat using water sample B. ◗ Pour 5 mL of water sample A into

another test tube. Add 3 drops of silver nitrate solution. Note whether the sample remains clear,

Abiotic factor

Soil temperature ( C) Water pH Water salinity Soil pH

RemembeR 1 Recall what sort of information line transects provide. 2 define the term quadrat . 3 Recall what sort of information quadrat sampling provides. 4 Write the equation used to determine the estimated abundance of a population in a particular area.

Core science | stage 4 Complete course

Environment B

Water temperature ( C)

activities

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Environment A

Think 5 Study the diagram below and then answer the questions on the following page.

(a) identify five abiotic factors that may affect the fishes health and chance of survival. (b) Apart from the fish, identify other biotic factors in the fish tank. (c) explain how the plants and the bacteria in the gravel might play a part in keeping the fish alive.

N

Use daTa 6 The location of five different types of trees in the two quadrats at right is indicated by the five different symbols. (a) Count and record the number of trees in each quadrat. (b) Count and record the number of the different species in each quadrat. (c) identify which quadrat provides a greater variety of habitat types for wildlife. explain your answer. (d) Propose why the rainforest species in both quadrats are located most densely near the creek.

Location A S: 41 g/L T: 26 C O: 19%

Location B S: 38 g/L T: 26 C O: 28%

Location C S: 37.5 g/L T: 24 C O: 41%

ey Blackwattle tree Messmate, rough-barked eucalypt Creek

Myrtlebeech, a rainforest tree Sassafras, a rainforest tree Mountain ash, smooth -barked eucalypt

7 The graph below shows the physical conditions at low tide along a rock platform from a cliff to the sea. Use this graph to answer the following questions. (a) describe the patterns along the rock platform for each of the abiotic factors measured. (b) identify the features that organisms living at the following locations would need. (i) Location A (ii) Location D (iii) Location F Location D S: 36 g/L T: 20 C O: 56%

Location E S: 35 g/L T: 17 C O: 72%

Location F S: 34 g/L T: 15 C O: 99%

Elevation above the low water mark (m)

Cliff

3.0 2.0 1.0

HWM

0.0

LWM: low water mark HWM: high water mark S: salinity T: temperature O: oxygen concentration 16

Abiotic factors

15

14

Pool

13

12

Sea LWM

11

10 9 8 7 6 5 Distance from low water mark (m)

4

3

2

1

0

salinity, temperature and dissolved oxygen at low tide on a rock platform

Source: Biozone International (Year 11 Biology 1996 Student Resource and Activity Manual)

work sheets

15.3 Distribution and abundance 15.4 Measuring abiotic factors

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15.3

You scratch my back The world is composed of many ecosystems and each contains thousands and sometimes millions of organisms. These organisms interact with each other in many different ways. Some organisms depend on other organisms for food, shelter or protection.

collaboration Collaboration involves individuals working together for shared benefit. Members of the same species may work together to achieve a common goal. Dolphins herding schools of fish together is one such example.

symbiosis Symbiosis describes an interaction between two different organisms

Tapeworms are parasites that live in the intestines of several animals, including humans. They vary in length from 1 cm to 10 metres. Their heads are equipped with suckers and sometimes hooks. because they live on the digested food in the intestine, they do not need a digestive system of their own. each tapeworm has both male and female sex organs so it does not need a mate to reproduce.

where at least one of them benefits. The other organism may also benefit, be unaffected or be harmed or even killed. There are three main types of symbiosis: mutualism, parasitism and commensalism.

mutualism An interaction between two different organisms that benefits both is called mutualism. In many cases, neither species can survive under natural conditions without the other. The tiny protozoans found in the intestines of termites help digest wood fibres. The protozoan does not live anywhere else and the termite would die without the protozoan they both benefit. Lichen, which is often found growing on rocks, is made up of a fungus and an alga living together. Both the fungus and the alga benefit from the interaction. The alga uses light from the sun to make food in the form of glucose (a carbohydrate). The fungus uses the carbohydrates made by the alga, but also shelters the alga so that it does not get too hot or dry out.

Parasitism Parasitism is an interaction where one species (the parasite) lives in or on another species (the host) from which it obtains food, shelter and other requirements. Some parasites harm their hosts but do not usually kill them. Tinea fungus causes a skin irritation called athlete s foot, and gets nutrients from its host, but does not kill the host. Rafflesia, a giant flower without leaves, lives on the roots of trees in the Malaysian jungle. The mistletoe plant lives on other plants and draws water and nutrients from their stems, but still makes its own food through photosynthesis, so it is only a partial parasite.

Mistletoe obtains water and nutrients from its host, but also makes food through photosynthesis. It is a partial parasite.

commensalism M Mutualism: lichen is made up of a fungus and an alga living together.

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Commensalism is an interaction between populations of two species in which one species (the commensal) benefits from another

(sometimes called the host) without damaging the host. For example, the remora fish, often found swimming under sharks, feed on scraps of food left by the shark, without interfering with the shark s lifestyle. The interaction between the clownfish and the sea anemone is another example of commensalism.

. . . and others Some symbiotic interactions do not fall into the three major categories: • Epiphytes are plants that simply grow on the outside of other plants without taking nourishment from them. Staghorn ferns, orchids and many other plants, found mainly in tropical rainforests, are epiphytes. Epiphytes are not parasites because they make their own food like other green plants.

• Saprophytes are organisms that live on dead and decaying plants. Most fungi belong to this group.

Most fungi are saprophytes.

Commensalism: the clownfish depends on the sea anemone for food, shelter and protection.

Elkhorn ferns and orchids are epiphytes.

activities RemembeR 1 define the term symbiosis . 2 (a) identify an example of a parasite and host. (b) How does the parasite affect the host? (c) How is the parasite affected in this relationship? 3 define the term mutualism . Give an example.

Think 4 compare commensalism and mutualism. 5 explain the type of relationship that humans have with the bacteria living on their skin. 6 describe some ways that humans try to control parasites. 7 Justify why the organism that a parasite lives on or in is called a host. 8 explain why it is harmful to a parasite s survival to kill its host. 9 classify the following as examples of parasitism, mutualism or commensalism. Give reasons for your answers. (a) Cleaner fish eat parasites off a larger fish to keep it clean.

• A leech feeds on the blood of animals, when it can attach itself to one, but can survive without drinking blood. Some leeches feed on dead and decaying animals and plants. • An insect larva bores into a tree for food and shelter, sometimes harming the tree, but sometimes having no effect.

(b) Cattle ticks suck the blood from cows. (c) Ants take food from our kitchen. (d) Termites consume wood, but cannot digest it. Protozoans in the termite s gut break down the wood, releasing sugar for the termites. The protozoans cannot live anywhere else. (e) Aphids suck the sap from rose plants. (f) A dog has a tapeworm in its intestine, absorbing the digested food. (g) Egrets feed on the insects that cows stir up. (h) Many harmless bacteria live in human intestines. (i) Root nodules of clover contain bacteria the clover benefits, but can survive without the bacteria; the bacteria don t live anywhere else. (j) Ringworm is a fungal disease on human skin.

invesTigaTe 10 The koala and the bacteria that live in its gut have a symbiotic relationship. investigate how each of the organisms benefits from this relationship. 11 Choose one of the following parasites. explain how it infests its host and how it affects its host. malaria parasites, tapeworms, ticks, insects that make galls in trees, blight-causing bacteria

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15.4

Food chains and webs All of the animals in a rock pool need to eat. Food is where animals get the energy they need to grow, move and reproduce. Some animals eat plants, but many eat

other animals. What do you think the animals in this rock pool are having for dinner tonight?

Other larger fish, such as the zebra fish, may be found in rock pools. This fish feeds only on seaweed.

The octopus is an expert hunter. Octopuses eat fish, crabs and shrimp.

Birds visit a rock pool to feed on fish, crabs, shrimp, sea urchins or shellfish. Algae and sea plants use the sun s energy to make food. Algae and seaweed are producers. Sea stars eat anything they can find. This includes crabs, shellfish and algae. They push their stomach out through their mouth and digest food outside their body. The elephant snail has a shell that does not completely cover its body. It hides under ledges in rock pools and comes out at night to feed on algae. Many animals, such as this sponge, filter the water for plankton. Rock pool shrimp are scavengers. The blenny fish is a common rock pool fish that eats other small animals, recently dead meat or algae.

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Producers

Many snails, such as the conniwink, chiton and limpet, eat algae. They use their rough tongues to scrape algae off rocks.

Sea urchins hide during the day and move about at night feeding on algae. They have spikes to stop other animals eating them.

Producers are organisms that can make their own food. All plants make their own food using the energy of the sun in a process called photosynthesis. In photosynthesis, plants use water, and carbon dioxide from the air, to make glucose (a type of sugar) and oxygen. To do this, the plant also needs a green pigment called chlorophyll. This is usually found in the leaves. The chemical word equation for photosynthesis is: carbon dioxide + water

sunlight

glucose + oxygen

chlorophyll

consumers

Sea anemones have sticky tentacles that catch anything that floats by in the water. This includes fish, algae, microscopic animals, and plants called plankton.

The dog whelk is a snail that eats other snails. It drills a hole through the snail s shell with its rough tongue and sucks out the insides. The green turban is a snail that feeds on larger seaweeds. Crabs feed on dead or decaying material in rock pools. Animals that feed on dead and decaying material are called scavengers. They eat anything they can find. The decorator crab covers itself in seaweed for camouflage.

Consumers are organisms that rely on other organisms for their food. Consumers feed on plants or other animals. The food is used as the material for growth and to release energy for living. The energy in foods is released in a process called respiration. Respiration takes place in every living cell. Plants also use respiration to release energy from the food they have made. Respiration is a chemical reaction in which organisms use oxygen and glucose to produce carbon dioxide and water. Energy is released during the reaction. The chemical word equation for respiration is: oxygen + glucose

energy released

carbon dioxide + water

meat or vegetables? Carnivores are animals that eat only the meat of other animals. In a rock pool, these include the dog whelk and the octopus. Animals that eat only plants are called herbivores. The elephant snail and the green turban snail are examples of herbivores. Some animals have a more balanced diet and eat both animals and plants. These organisms are called omnivores. The sea star is an omnivore in the rock pool.

hunting or hunted? An animal that hunts another animal is called a predator. The animal it hunts is called its prey. An example of predator prey relationship in the picture on these two pages is the relationship between the seagull and the urchin. The seagull is the predator and the urchin is the prey.

15 Ecology 399

food chains

food webs

A food chain shows how the energy stored in one organism is passed to another. Each organism depends on the one before. All food chains start with a producer, such as algae. The producer obtains its energy from the sun and provides the nutrients and energy that other animals need. Herbivores that eat the plants, such as the green turban snail, are called first-order consumers. Carnivores that eat first-order consumers, such as the dog whelk, are known as secondorder consumers. The seagull is a third-order consumer because it eats the second-order consumer. A food chain can be represented by a simple diagram.

Many animals eat more than one type of food. This means that they are in more than one food chain. Joining a number of food chains together produces a food web. Note that some animals, such as the seagull, may actually be in more than one level, depending on which chain you follow to the top. A food web also has decomposers. Decomposers are organisms, such as bacteria, worms and fungi, that break down dead animals and plants. The nutrients in the dead animals and plants are recycled back into the food web.

Octopus

Energy

Second-order consumer: dog whelk

Animal waste and dead organisms

Third-order consumer: seagull

Zebra fish Green turban snail

Crab

Shrimp

Energy Blenny First-order consumer: green turban snail

Energy

Producer: seaweed

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Dead and decaying material

Seaweed and algae Decomposers

Seagull

activities

an energy pyramid Producers absorb the sun s energy during photosynthesis to make sugar. some of the sun s energy is stored in the sugar. When consumers eat producers, the energy is passed up the food chain. however, some of this energy appears to be lost at each link in the chain. but the energy cannot just disappear. instead, it is transferred to the surrounding environment as heat, wastes, and even sound. This means that only a small amount of the sun s energy makes it to the top consumer. for energy to reach the animals at the top of the food chain, there must be many plants at the bottom of the chain. This means that a food web rarely has more than six trophic levels. at each level there are fewer animals of each type because there is less energy available. This is shown in the energy pyramid.

Dog whelk

Limpets

RemembeR 1 define the terms producer , consumer and decomposer . 2 Recall where producers get their energy from. 3 outline how consumers release energy from the food they eat. 4 Write an equation for respiration. 5 describe what happens to the amount of energy available to organisms as it moves through an energy pyramid.

Think 6 compare the types of information that can be represented in a food chain and a food web. 7 Give examples, from the rock pool on pages 398 9, of herbivores, carnivores, omnivores, predators and prey. 8 Predict what would happen to the animals in a rock pool if the seaweed and algae died. 9 explain the advantage of animals having more than one food source.

Energy Energy 1 octopus

Energy 2 larger fish

6 small fish 500 plants

This food chain has four trophic levels.

10 Julie and James were studying animals in their local park. They made the following observations: ◗ Grasshoppers eat grass. ◗ Mice eat grass seeds and grasshoppers. ◗ Small birds eat grasshoppers. ◗ Snakes eat mice and small birds. ◗ Kookaburras eat snakes. (a) construct a food web using this information. The producers should be at the bottom. (b) identify which organisms: (i) are producers (ii) are first-order consumers (iii) are second-order consumers only (iv) are second- and third-order consumers (v) are herbivores (vi) are omnivores (vii) compete for food (viii) have more than one food source. (c) Predict what would happen if the snakes died out. work sheet

15.5 Food chains and food webs

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15.5

natural recyclers Tyrannosaurus rex stalked the Earth over 65 million years ago. We have found the bones, but what happened to the atoms that made up its flesh? Saint Joan of Arc, a great military leader and religious visionary, was burned at the stake in 1431. What became of the atoms in her body? What will happen to the atoms in your body when you die? The answer to each of these questions is the same they are recycled.

flies and maggots Flies lay their eggs on dead and decaying animals. The eggs hatch into larvae that are called maggots. The maggots can quickly eat away large parts of a dead animal. The maggots grow up to become flies, which lay eggs somewhere else, or become food for other animals. This recycles the nutrients from the dead animal back into the ecosystem.

Worms Worms are very effective recyclers. Worms eat just about anything and can do so quickly. They are especially good at recycling our food waste. Worms are found underneath dead organisms in the soil. They feed on animal and plant remains, recycling them into nutrients for plants.

bacteria Bacteria can grow on anything dead or alive. They grow and reproduce very quickly. Bacteria reproduce by simply dividing in half. Bacteria feed on decaying material to help break it down and recycle nutrients for other animals. This photograph of bacteria was taken using an elecron microscope.

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fungi Mushrooms and toadstools are fungi that feed on dead material. Another variety of fungi is called mould and looks fuzzy. Fungi grow microscopic threads into the food they are feeding on. These threads help to break down the dead organism. Fungi may become food for other animals, or they may decay. This allows the nutrients to be recycled back into the ecosystem.

call in the decomposers cycles in nature After organisms die, the decomposers are responsible for breaking down their bodies and recycling the atoms that make them up. Decomposers include worms, some insects, bacteria and fungi. They feed on the chemicals that make up the dead organism and convert them into other chemicals. By doing this, they return the nutrients that make up the dead organisms to the soil and the atmosphere, where they can be taken up by plants and other living things. Decomposers can also break down some of the rubbish humans produce. Things that can be broken down by decomposers, such as paper and food scraps, are said to be biodegradable, whereas substances like plastic or foam that cannot be broken down by microbes are said to be nonbiodegradable.

The amazing worm farm about 60 per cent of our household rubbish can be used as worm food. Worms eat just about anything that was once living, including kitchen scraps, garden waste and manure. They love pizza and will even eat the box it comes in! Worms can eat about half their body weight in food each day. We can use a worm farm to feed our once-living rubbish to worms. This is how a worm farm works. The lid has ventilation holes to let air in. The holes are small so that flies and insects cannot get in. A bedding of shredded paper, manure, leaf compost, or a mixture of these, is added first. The bedding must always be kept damp. Worms are placed in the bedding.

Decomposers play an important role in cycling nutrients. They are involved in the carbon cycle (see page 406) as well as in the nitrogen cycle. In chapter 13, you learned that plants need nitrogen to build proteins, and that, even though the atmosphere contains over 80 per cent nitrogen, plants cannot absorb the nitrogen they need directly from the air. They can absorb it only in the form of nitrate compounds through their roots. Certain bacteria, called nitrogenfixing bacteria, are the only organisms on Earth that can absorb nitrogen and turn it into nitrate compounds. Plants use the nitrate compounds they absorb from the soil to build proteins. When an animal consumes a plant, it uses the plant proteins to make new animal proteins. Other bacteria, called nitrifying bacteria, are also involved in the nitrogen cycle. When an organism dies, its proteins break down and the nitrogencontaining molecule ammonia (NH3) is formed. This also happens when an animal s wastes decompose. Nitrifying bacteria turn the ammonia firstly into nitrite compounds and then into nitrate compounds. A third group of bacteria, the denitrifying bacteria, Food scraps are added on top of the bedding for the worms to eat. A sheet of newspaper or hessian is put over the top of the food to keep it dark.

an entomologist is a scientist who studies insects. sometimes entomologists are asked to provide information to help solve crimes. after a person or animal dies, insects are attracted to the corpse and feed on it. They lay their eggs in the corpse, and larvae eventually emerge from the eggs and develop into adult insects. over time, different types of insects colonise the body. by looking at the types of insects and what stage of their life cycle they are at, it is often possible to work out the time of death. it is sometimes also possible to find out other information about the crime from the types of insects that have colonised the body. if a body spent some time in a dry cool area before being buried in dry sandy soil, the insects living on it would be different from those if it had been buried in dry sandy soil straight after death.

Professor Jerry Butler is a real-life entomologist. He is shown here examining hairy maggot blowfly larvae retrieved from a murder victim.

The top level is still empty. There are holes between levels to allow the worms to move up when the level below is full. The worms turn the bedding and food scraps into compost. This is the nutrientrich worm poo .

Liquid runs into the tray on the bottom and is known as worm wee . It makes an excellent liquid fertiliser for plants.

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can turn nitrates back into nitrites and ammonia, and even into nitrogen gas. This is not good for plant growth as it is the nitrates that a plant needs to make protein, not the nitrites. Nitrites are poisonous to plant growth. Nitrates can also be formed by lightning during storms, causing nitrogen and oxygen to react together. Nitrogen in the air

Lightning

Nitrogen-fixing bacteria

Plant proteins

engine such as Picsearch or AltaVista Image Search. ◗ In the search box, type

science cartoons or science environment cartoons or science sustainability cartoons or recycle cartoons . ◗ Choose a cartoon that you

think makes an important point. Eaten by

Nitrites in the soil

The nitrogen cycle

◗ Write a paragraph explaining

Animal proteins Decomposition Ammonia in the soil

activities RemembeR 1 define the term biodegradable . 2 identify two types of biodegradable waste. 3 identify two types of nonbiodegradable waste. 4 Recall the main groups of decomposers. 5 Propose why decomposers are also called natural recyclers. 6 explain why worms are such good recyclers.

8 outline why animals and plants need nitrogen. 9 Both bacteria and maggots are decomposers that feed on dead material. But they are also different types of organisms. compare the size and reproduction of bacteria and maggots. 10 explain why a worm farm is a useful way of disposing of some household rubbish. 11 outline why paper bags are better for the environment than plastic bags. 12 explain the difference between nitrogen-fixing bacteria, denitrifying bacteria and nitrifying bacteria.

Think 7 identify the organisms that are responsible for absorbing nitrogen from the air.

Core science | stage 4 Complete course

what message the selected cartoon gets across and why it is funny.

Dead animals and plants

Nitrifying bacteria

404

One of the simplest and best definitions of sustainability is to meet our needs in the present without compromising the ability of future generations to meet their needs .

Absorbed by plants

Denitrifying bacteria

Nitrifying bacteria

sustainable cyberhunt

◗ Choose an image search

Denitrifying bacteria

Nitrates in the soil

InvEstIgatIon 15.4

invesTigaTe 13 Do some research to find out more about worms. This could include

information about their body structure, how they reproduce, what they do or do not like to eat, and their behaviour. 14 Some types of worm are good recyclers and others are not. Design an experiment to test how good different worms are at recycling food scraps. You could compare garden worms with some worms bought at a garden centre.

design and cReaTe 15 construct a worm farm for your class. This could be used to recycle your class s lunch waste. Using an appropriate search engine, you should be able to find a simple design on the internet. work sheet

15.6 Cycles in nature

15.6

It s getting hot in here How many days did the temperature rise above 40 C last summer? Unfortunately, very hot days are something we may need to get used to. Australia and the rest of the world are getting warmer, and climate patterns are changing. Some parts of Australia are set to become even drier than they are now. Scientists believe that the cause of climate change is human activity upsetting the composition of our atmosphere.

The greenhouse effect The Earth is surrounded by a layer of gases. This natural layer of gases (which includes carbon dioxide and water vapour) traps the sun s warmth and keeps the Earth at the correct temperature for maintaining life. This

greenhouse effect has kept the Earth s temperature fairly constant for a very long time.

The enhanced greenhouse effect Human activity has increased the amount of gases that trap heat in the atmosphere. These gases are called greenhouse gases. They include carbon dioxide, methane, water vapour, nitrous oxide and ozone. With more greenhouse gases in the air that trap heat, the Earth s temperature is rising. This is called the enhanced greenhouse effect. The rising temperature of the Earth (which the enhanced greenhouse effect contributes to) is commonly called global warming.

The Earth is covered by a blanket of gases that trap enough heat to keep the temperature stable. Most heat escapes back into space.

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Global warming in Australia Learn why many scientists believe the Earth is getting hotter and how Australia is addressing this global problem. eles-0057

What causes the increase in greenhouse gases? carbon dioxide

To understand why carbon dioxide levels are rising, we need to understand the carbon cycle. Many processes release carbon dioxide into the air. When living things respire, and when dead organisms decompose, carbon dioxide is released. Burning fossil fuels such as coal, petrol and gas also More carbon dioxide and other releases carbon greenhouse gases in the air trap more dioxide. On the heat from the sun. The Earth s other hand, plants temperature will rise. absorb carbon dioxide when they photosynthesise. Humans are burning large amounts of fossil fuels to make electricity and run cars. We have also cut down many trees and replaced them with buildings or crops that do not take up as much carbon dioxide as growing trees. This has caused carbon dioxide levels to rise.

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Recycling carbon Carbon atoms are found in the air, soil, rocks, in oil and gas below the Earth s surface, and in all living things. The number of carbon atoms on Earth always remains the same. When living things use carbon atoms, the atoms don t just disappear. They are recycled. The diagram below shows the recycling of carbon. It also shows how humans have added to the amount of carbon dioxide in the air. We must take care not to interfere with the natural recycling process. Humans burn fossil fuels to make energy. Burning fossil fuels releases carbon back into the air as Deforestation leads to an carbon dioxide gas. increase in the amount of carbon dioxide in the air. Dead trees can t absorb carbon dioxide from the air. The organisms that decompose trees also release carbon dioxide.

Dead material can form oil and gas within the Earth s crust. Oil and gas are known as fossil fuels.

other greenhouse gases Carbon dioxide is not the only gas that is causing the Earth to get hotter. Methane and nitrous oxide are also increasing as a result of human activity. Methane is produced by grazing animals such as sheep and cattle. Some other important sources of methane are landfills (where garbage is dumped after it is collected from your house) and agriculture. Bacteria that live in the soil where crops grow produce methane. Rice paddies, in particular, are a significant source of methane. The main source of nitrous oxide is farming; it is produced when bacteria break down urine produced by livestock and fertilisers added to the soil.

Carbon is found in the air as the gas carbon dioxide. Plants take carbon dioxide from the air. They use it to make food in the form of sugars.

Living things release carbon dioxide back into the air through respiration.

Animals get carbon atoms by eating plants or other animals that eat plants.

Dead matter and waste contain carbon. Decomposers release carbon dioxide back into the air through respiration.

Scientists have used ice cores to track the amount of carbon dioxide in the air and the Earth s temperature. The graphs on the next page show how these have changed over the past 420 000 years.

Where s the evidence? For thousands of years, snow has fallen in Antarctica. The snow turns to ice, which builds up over time. Dust, gases and other substances from the air become trapped in the ice. The trapped substances provide information about what was in the air at the time the snow fell.

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This ice core was drilled from more than 3.7 km down. Parts of it are more than 150 000 years old.

Temperature difference over 420 000 years

350

4

300

2

Temperature difference

CO2 (ppm)

CO2 in the air over 420 000 years

250 200 150

0 2 4

100 400 000

300 000 200 000 100 000 Number of years ago

0

The line on the graph for carbon dioxide resembles the temperature line. When the temperature was higher, there was more carbon dioxide in the air. When the temperature dropped, so did the amount of carbon dioxide. (The abbreviation ppm means parts per million.)

400 000

300 000 200 000 100 000 Number of years ago

0

Zero on the temperature scale represents the Earth s average temperature now. Greater than zero is warmer than now, and below zero is cooler. On the temperature line, the peaks represent warmer periods of time. In between the peaks, the average air temperature was up to 6 C lower than now. These colder times are called the ice ages.

how much hotter?

is there a solution?

No-one really knows how much hotter the Earth s temperature may get. It is thought that it may increase between 1.4 C and 5.8 C over the next century. This does not sound like much, but it could cause many changes in the climate. The changes could include: • more heatwaves, droughts and bushfires • more wild storms, such as tropical cyclones • less rain and less snow in the mountains • rising sea levels as the polar icecaps melt. This could cause some islands and coastal cities to flood. The changes in climate may have a follow-on effect on plants and animals. These may include: • plants growing faster in some areas because of higher temperatures and more carbon dioxide becoming available for photosynthesis • plants growing slower, or dying in other areas, due to the lack of rainfall • plants or animals becoming extinct as their habitat changes. For example, animals in the high country that are adapted to cold weather may find it becomes too warm. • bacteria and fungi growing faster in the warmer climate. This would increase the risk of disease. • humans suffering from heat stress and increased pollution in cities.

Many scientists and most world leaders are becoming increasingly aware of the need to address global warming. In 1997, at a meeting in Kyoto, most world leaders signed a document (the Kyoto Protocol), agreeing to reduce the amount of greenhouse gases they produce. Australia did not sign the Kyoto Protocol until 2007. At the Climate Change conference in Bali in December 2007, nations agreed to work on a new document to replace the Kyoto Protocol and sign it at a UN climate change conference in Copenhagen in 2009. Reducing greenhouse emissions will not be easy. It is likely to involve cutting down on our use of fossil fuels. That might mean cutting down on our use of cars or finding a different source of energy for cars. We will need to reduce our use of electricity or generate our electricity without burning fossil fuels. Our farming methods may also need to be modified, and we may need to change our diet so that we eat less meat and favour locally grown fruit and vegetables. Making all devices as efficient as possible, so that less energy is wasted, and recycling or re-using as many products as possible will also help us reduce greenhouse emissions and help keep the planet cool.

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activities RemembeR 1 describe the greenhouse effect.

Argument

2 Does the greenhouse effect occur naturally? explain your answer.

If all countries agree to Against drastic cuts, no-one will buy Australia s coal, and jobs will be lost in the coalmining industry.

3 describe the enhanced greenhouse effect. 4 identify human activities that add more greenhouse gases to the air. 5 describe two possible effects of global warming on animals. 6 Predict the effect of global warming on bacteria and fungi. 7 What is the Kyoto Protocol? 8 What is the purpose of the UN climate change conference that will be held in Copenhagen in 2009?

Think 9 explain how cutting down trees increases the amount of carbon dioxide in the air. 10 If more carbon dioxide is added to the air, predict what will happen to the temperature of the Earth. 11 outline some ways that humans could reduce the amount of carbon dioxide added to the air. 12 If the sea levels rise when the Earth s temperature increases, predict what would happen to the sea levels if it got colder. Why? 13 explain how each of the following actions could reduce greenhouse emissions. (a) Walk or use public transport rather than getting a lift in the car to school each day (b) Have shorter showers (c) Eat less meat and rice and more vegetables (d) Buy fruit that is in season and grown locally rather than imported fruit (e) Avoid wasting things like paper and recycle as much as possible (f) Avoid using heaters, airconditioners, clothes dryers and other electrical appliances 14 At the UN climate change conference in Copenhagen in 2009, world leaders will probably have to agree on the amount by which their countries will cut greenhouse emissions. For example, they might agree that by 2020 they will release 20 per cent less carbon dioxide than in 2007. The table on the right lists reasons for and against making drastic cuts in greenhouse emissions. classify each argument as either in favour of or against making large cuts, and then classify each argument as scientific, economic or legal. The first example has been done for you.

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Type of argument (scientific, economic or legal) Economic

Global warming has already begun. If we do not cut our greenhouse gas emissions now, it may be too late to reverse the damage. If really tough targets are set, it will be difficult for many nations to reach the targets. It will be necessary to decide how to penalise these nations. If global warming continues, scientists predict that some areas of Australia may experience permanent drought conditions. Climate change will affect farming and could cause some farmers to become bankrupt. The changes to business practices needed to reduce greenhouse emissions will cost businesses lots of money and may lead to job losses.

imagine 15 You are a newspaper reporter. Write a story to explain the enhanced greenhouse effect to people. Include a description of the causes of global warming and some of the effects it may have. eBook plus

16 Use the Global warming weblink in your eBookPLUS to find out more about what you can do in your home to reduce the amount of carbon dioxide released. Produce a brochure to teach people how they can help slow global warming. work sheet

15.7 Global warming

15.7

Fired up for change Aboriginals have traditionally used fire to hunt animals and clear undergrowth. This caused grasses to grow. The extra growth attracted new animals. Fire has always been present in Australia and is a major cause of change in the environment. When fire has not occurred for a period of time, undergrowth builds up, and more sticks and leaves fall to the ground. The longer the time between fires, the more plants and leaf litter there is. This means more fuel for a fire. People, camp fires, barbecues, cigarette butts, power lines, burning off and lightning can all start fires.

fire! fire! Some fires are lit on purpose, like those used by Aboriginals and park rangers to regenerate the land. These small controlled fires also help to reduce the risk of a big fire because they use up some of the fuel. Large out-of-control fires in bushland are called bushfires. Bushfires do more damage to animals and plants because they are hotter and burn nearly everything. They often destroy homes and property. It is believed that the regular controlled fires that were lit by Aborigines as part of their hunting practices have contributed to the type of vegetation now growing in Australia. The regular fires probably changed rainforest areas into the open eucalypt forests that cover much of Australia today. Australian native grasses get their tops burned off every few years. But they still manage to survive.

Within days you can see new sprouts growing out of the burnt grass. Australian plants have had to get used to fire. They must live with it, or not live at all. Animals manage to survive a fire in many ways: • Insects hide under the bark of trees or in the soil. • Flying insects flee and return after the fire. Small controlled fire Some leaf litter destroyed; many insects and decomposers survive on the ground.

• Birds and bats fly away. • Large animals, such as kangaroos and wallabies, run away. • Wombats and snakes hide in their underground burrows. • Koalas run away or stay in the tops of trees where the fire is not too hot. • Animals find shelter in the parts of the ecosystem that have not been burned. Large bushfire All leaf litter destroyed; no insects and decomposers survive on the ground.

Soil releases stored nutrients. Ash provides many minerals and fine texture. This helps seeds to germinate and new plants to grow. Heat and smoke cause some plants to release seed and some seeds to germinate.

Heat and smoke cause most plants to release seed and many seeds to germinate.

Many unburnt patches where grasses and shrubs survive; animals can find food and shelter here.

Few unburnt patches; no food or shelter is left for animals.

Many animals survive and can stay in the area. Food is still available.

Many animals are killed, or must move to another habitat. No food is available.

Fallen branches and logs survive to provide shelter for animals.

No fallen branches or logs survive so there is less shelter.

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Why the australian bush needs fire

after a fire is very rich in nutrients and fertilises the soil. After a fire, plants rapidly grow new shoots and leaves. Both plants and animals recover very quickly from a fire. A fire can have both good and bad effects on an ecosystem. The effect of a fire depends on the fire intensity that is, how hot it is.

In the Australian bush, fire is a natural part of the life cycle of many plants. Many Australian plants cannot germinate without fire. Their seeds are encased in hard husks that can be opened only by the high temperatures produced in fires. The ash left behind Eucalypts have buds underneath the bark. After a fire these epicormic buds sprout new green shoots.

Eucalypts store some seeds on the plant. Eucalypts have woody gumnuts that protect the seed from the heat. After a fire, the seed pods dry out and open. The seeds fall into the ash and germinate. The bark of trees helps to protect the trunk and buds underneath from damage in a fire.

Fire causes many grasses to flower. This grasstree will produce a flower spike 7 10 months after a fire. Insects pollinate the flowers, the seed is released, and new plants grow. The trunk of the grasstree is protected by a thick layer of old leaf bases. The leaves on the top may be burned; but the plant is not killed. Banksias live for only 8 15 years. They store their seed on the plant. A fire causes the seed pods to open, releasing the seed.

Many plants flower as a result of fire. The redbeak orchid flowers only in the first season after a fire.

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Grasses have their growth tissue at the base of the plant. When the top burns off, the heat rises and the growth area is protected from damage. Grasses can then regrow quickly after a fire.

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Some plants, such as lilies, have tubers under the ground. If the top is burned off, they use the energy stored in the tubers to start growing again.

Many plants drop seed that is stored in the soil. The heat of a fire may crack the hard coating of wattle (acacia) seeds and allow them to germinate. The chemicals in the ash or the smoke may also cause germination. In Tasmania, wattle seeds that are 300 400 years old have been found in soil, just waiting for a fire.

Many plants, such as eucalypts and banksias, have swollen parts on their roots called lignotubers. These are protected from the fire by the soil. Lignotubers contain many buds. After a fire they send up new shoots.

InvEstIgatIon 15.5

◗ Collect the seeds and plant them

in the seedling trays. Care for them until they are large enough to plant in the garden.

germinating seeds with fire Many seeds need fire to germinate. It could be the smoke, heat or the chemicals in ash that cause the seeds to germinate. You will need: hakea or banksia seed pods unopened newspaper matches bucket of water seedling trays seedling mix acacia seeds (silver or black wattle work well) oven Part A ◗ Collect unopened banksia or hakea

seed pods from trees in your local area. ◗ Wrap the seed pods in newspaper

and burn them in a safe area. (Alternatively, heat the pods in an oven.) ◗ Observe the seed pods after burning.

activities RemembeR 1 outline why Aboriginals traditionally used fire. 2 describe what happens in the bush in the periods between fires.

CAUTION • Make sure you are supervised by an adult. • Burn seed pods only in a safe area. • Do not do this activity on a hot windy day or a day of total fire ban. • Have a bucket of water or a fire extinguisher ready. • Pods stay hot for some time after burning. Give them time to cool before touching them.

1

What effect did heat or fire have on the pods?

2

How does the opening of seed pods in response to heat help plants to grow at the right time?

Part B equal piles. Record the number of seeds in each pile.

◗ Plant these seeds in a separate

seedling tray. Sprinkle some ash over the seedling tray. ◗ Keep the trays moist. Wait for the

seeds to germinate. This could take many days. ◗ Count the number of seedlings

that have germinated in each tray. Compare class results. ◗ Look after your seedlings and,

when large enough, plant them in a garden.

discUssion 3

How did heat change the look of the seeds?

4

Which group of seeds germinated better?

5

What caused one group to germinate more?

6

How is this similar to what a fire would do?

8 explain whether a controlled fire or a bushfire is more damaging to the environment. 9 If a fire occurred in the same place two or three years in a row, describe what may happen to some of the animals and plants in the area.

4 define the terms lignotuber and epicormic bud .

11 explain why park rangers burn areas of the bush today.

5 describe how a grasstree responds to and survives fire.

12 describe what would happen to the red-beak orchid if there were no fires for 50 years.

7 explain the difference between a controlled fire and a bushfire.

◗ Heat the second pile in the oven.

◗ Divide the acacia seeds into two

10 explain how bushfires can start: (a) without any human activity (b) as a result of human activity.

Think

tray.

discUssion

3 Recall three positive effects of a fire on the environment.

6 explain how eucalypt seeds are protected from fire.

◗ Plant one pile of seeds in a seedling

13 compare a eucalypt and a banksia in the way they cope with fire. 14 Look at the photograph above and describe what has happened and what the area may look like in the near future.

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15 Use the Bushfire weblink in your eBookPLUS to find out what to do if you are caught in a bushfire. Write an emergency survival information card that people could use if they were caught in a bushfire.

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15.8

Floods and droughts The Australian continent is a land of extremes; years of drought can be broken by torrential rain that results in flooding. Both drought and flooding can affect the environment. But a question on the minds of many scientists is whether global warming will make the Australian climate even more extreme.

drought Australia is the driest continent on Earth. Even in periods without drought, areas away from the coast of Australia generally receive very little rainfall, and much of central Australia is so dry that the land is not suitable for farming. Even near the coast it is often necessary to irrigate (water) crops.

Droughts also affect the environment. During periods of drought there is more soil erosion and bushfires are more frequent. Species of plants that are not drought tolerant may be replaced by more drought-tolerant species. This, in turn, affects the types of animals that live in a particular area. Until about 50 000 years ago, much of Australia was covered with lush rainforests full of plants with large soft leaves. The Australian climate became drier over time. The rainforest plants were not suited to the dry conditions and were replaced by plants with smaller, harder leaves that are better suited to the dry conditions. The plants covering much of Australia today are ideally suited to dry conditions.

adaptations for dry conditions Adaptations are features that help an organism survive in its environment. The pictures below and on the next page show some adaptations of the eucalyptus tree and the eastern grey kangaroo that enable them to survive in the dry Australian environment. Light-coloured fur reflects heat and allows the kangaroo to blend in with its surroundings.

Large ears dissipate heat.

The kangaroo produces concentrated urine to conserve water.

Little grass grows in times of drought, and grazing animals run out of food.

Australia regularly experiences periods of drought. The drought in the early part of the twenty-first century was the worst on record. Many farmers were forced to sell their farms as their crops failed and their livestock starved. In towns and cities, dams dried up and measures were taken to conserve the water that was left.

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Bouncing allows kangaroos to travel quite fast without using much energy, so they need less food. This helps them survive in times of drought.

The forelimbs have many blood vessels close to the skin. The kangaroo licks its forelimbs; as the saliva evaporates, it draws heat away.

Adaptations that help a kangaroo survive in a dry environment

Woody fruits (gumnuts) protect seeds from drying out.

Leaves have a thick waxy cuticle to reduce water loss.

Blue-grey leaves reflect heat.

global warming, while others argue that Australia s climate has cycled through periods of drought and flood for many years before the world started to warm up. Most agree, though, that further global warming is likely to permanently change rainfall patterns. Southern Australia, where most of the population lives, is set to become drier. Creative solutions to the water supply crisis are urgently needed.

activities RemembeR 1 describe the effect of drought on people and the environment in Australia. 2 define the term adaptation . 3 describe three adaptations of the eucalyptus tree and the grey kangaroo for dry conditions.

Leaves hang vertically so that a smaller area of the leaf is exposed to the sun in the middle of the day.

4 describe the effect of flooding on people and the environment.

Think 5 Make a list of ways you can conserve water at home.

Bark has a light colour to reflect heat.

6 outline the likely effect of global warming on rainfall patterns in Australia.

invesTigaTe 7 Find out what a water desalination plant is and discuss whether it was a good idea to build one in Sydney. Adaptations that help eucalypt trees survive in a dry environment

floods When rain does fall in Australia, it often results in flooding. Floods affect agriculture; livestock may drown and crops can be destroyed. When a town or city is flooded, the damage to property can be very costly to repair. In some cases, lives may be lost and diseases may spread as sewerage systems overflow and mix with the floodwaters. Floods also affect the natural environment. Vegetation may die if it remains under water for a long time, and topsoil is washed from one area to another by the floodwater.

The effect of global warming on rainfall patterns The recent drought was the worst in Australia s recorded history. Some climate experts are blaming

8 Use a research database such as EBSCO and search for an article about a flood that occurred in Australia recently. For this flood, find out: (a) where it occurred (b) the impact it had on people and property. eBook plus

9 Use the Sydney Catchment Authority weblink in your eBookPLUS to find out how full the dams supplying Sydney s water are. 10 Use the Water investigator game weblink in your eBookPLUS weblink to build your own virtual home and calculate your family s water usage. 11 Use the New Inventors weblink in your eBookPLUS, browse the inventions by category and select the category environment . List at least five Australian inventions that are aimed at conserving water, recycling water or obtaining fresh water from sea water.

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15.9

PRescRibed focUs aRea current issues, research and development

Being part of the solution The Australian environment is under threat from human activity. However, the situation is not hopeless; if we all do our bit to look after our environment, we can continue to enjoy this great land of ours, now and in the future.

Renewable or not? Resources are things we use to make things, as a food source or to generate energy. Some resources are renewable. That means that they can be regenerated over time. Wood, leather, meat, wheat, fish, cotton and wool are all renewable resources. Non-renewable resources cannot be regenerated; once they are used up they cannot grow back or re-form. Gemstones such as diamond and rubies are non-renewable. Marble and granite are also non-renewable. Metals are extracted from non-renewable metal ores, and most plastics are made from non-renewable petroleum. Choosing to use resources that are renewable is one way that you do your part to look after the planet and ensure that Earth s resources are not depleted for future generations .

that, unlike fossil fuels, they will not run out. It must be remembered that even renewable energy sources can harm the environment though. Wood, vegetable oil and ethanol all produce carbon dioxide when burned to release energy, thus contributing to global warming, and building dams to harness energy from water can destroy ecosystems.

Reduce, re-use and recycle Growing crops, processing the crops to make food, making goods such as clothes, electronic goods and books, as well as transporting goods and food around the country all produce pollution and greenhouse gases. When you throw out these goods and they are left to decay in landfill, more pollution results. In most cases, making electricity also causes pollution and releases greenhouse gases. The best thing you can do to look after the environment is to buy fewer things and continue to use the things you already have. You can also avoid wasting electricity and food, choose goods with little packaging that are made locally, and re-use, compost or recycle as much of your rubbish as possible.

choosing your energy source Toasting bread, boiling water for tea and lighting a dark room all require energy. The impact of generating this energy on the environment can vary greatly according to the source of energy used. Electricity can be produced in many ways. Currently most of the electricity used throughout the world is produced by burning fossil fuels such as coal or gas. Fossil fuels are not renewable. Nuclear power plants use uranium, another nonrenewable resource. It is also possible to produce electricity by burning wood or using energy from tides, the wind, water flowing downhill and the sun. These sources of energy are renewable. Similarly, cars can run on non-renewable petroleum, or with modifications to the engine they can run on renewable vegetable oil or ethanol made from plants. The advantage of using renewable sources of energy is

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Australia s landfills are costing $740 million each year in environmental damage. This could be reduced by re-using, recycling, composting and buying goods with less packaging.

◗ Use bathroom scales or an

InvEstIgatIon 15.6

electronic balance to estimate the mass, in kilograms, of the contents of each garbage bag. Think carefully about the best way to do this for each bag. Don t forget to divide by 1000 to convert to kilograms, if you measure the mass in grams.

investigating rubbish You will need: rubber gloves several garbage bags marking pen bathroom scales electronic balance calculator

Which type of rubbish is the most common (by mass)?

2

Why is the total mass per year only an estimate?

3

Which types of rubbish collected could be recycled?

4

Discuss this question with the rest of your group: How could the amount of wasted recyclable rubbish be reduced? Following the discussion, write down your own answers to the question.

below to record your results in. The example shown in the table records part of the rubbish taken on a single day from a single bin outside a school canteen. The total mass collected from the bin that day was 8 kilograms.

around the school by collecting litter left on the ground over a period of several days or by sorting out the rubbish left in a bin near the school canteen. CAUTION Do not handle any sharp objects or put them in garbage bags. Inform your teacher if sharp objects are found. Do not empty a bin while bees or wasps are nearby. ◗ Collect litter in a large garbage bag

Per cent (by mass)

◗ Calculate the percentage of the

total mass for each type of rubbish, using the following formula. (See the example in the table.)

Food 36%

◗ For each type of rubbish, estimate

the mass that would be disposed of over a period of a year. Think carefully about how this should be done. The food scraps referred to in the table were found in a rubbish bin outside a school canteen. They represented one full day s rubbish in that bin. The mass was multiplied by 200 because there are about 200 days in a school year.

or spread the contents of a rubbish bin over the ground. ◗ Wearing rubber gloves, sort the

rubbish into seven different rubbish bags: food scraps paper and cardboard plastic glass aluminium cans other metal other rubbish.

Food scraps

1

◗ Construct a table like the one

◗ This experiment can be done

Type of rubbish

discUssion

percentage mass of type of total = × 100% total mass mass

Mass collected (kilograms) 2.5

Paper 21%

Glass 16% Plastic 10% Garden 7% Steel 5% Aluminium 1% Other 4% A survey of household rubbish shows that a lot of materials that could be recycled are being wasted and unnecessarily damaging the environment.

Percentage of total mass

Estimated mass per year (kg)

2.5 × 100% = 31% 8

2.5 × 200 = 500

15 Ecology 415

scientists making a difference If you have an interest in ecology, you may want to make a career out of conserving the environment. The scientists described on this page are all contributing to finding solutions to environmental problems.

helene marsh Professor Helene Marsh studies dugongs. A dugong is a type of mammal that lives in the ocean and feeds on seagrass. Her research initially involved studying the carcasses of dugongs that had died in shark nets. She worked out a way of estimating the age of dugongs by studying their tusks. Later, she focused on the reproductive cycle of dugongs. Helene has also been involved with estimating the abundance of dugongs in various areas using aerial photographs. By measuring the abundance of dugongs regularly, it has been possible to identify areas where dugong numbers are falling and suggest strategies to maintain dugong numbers.

of sea birds that die as a result of long-line fishing. Long-line fishing uses a very long line with many baited hooks sunk into the ocean. Graham has found that, if the line sinks too slowly, sea birds including albatrosses, petrels and shearwaters are lured by the line, get caught on the hooks and die as the line sinks further into the ocean. By weighing down the lines so that they sink faster, a lot fewer birds are lost. He has worked with long-line manufacturers to design lines that have weight built into the fabric of the line. Graham has also been involved with important research on the ecology of the emperor penguin.

Graham Robertson

One of the steps involved in photosynthesis actually converts light into electricity. Plants can do this step with 30 40 per cent efficiency. Deanna has been able to make molecules called porphyrin dendrimers, which, like chlorophyll, can convert light into electrical energy. These molecules can be used to make solar panels. It is hoped that this will lead to the production of solar panels that can produce more electricity per square metre.

Tim flannery Professor Tim Flannery was named Australian of the Year in 2007, largely for helping make Australians more aware of environmental issues. He started his scientific career studying the evolution of Australasian mammals. This involved looking at living examples of mammals as well as fossils. In 1994, Tim Flannery published a book called The Future Eaters that described the damage humans have caused to the Australian environment. He has argued that the Australian environment can cope with only about 6 million people and that we should be trying to cut down rather than increase Australia s population. In his book The Weather Makers, he focused on global warming and suggested controversial ways of addressing this issue.

Long-line fishing can kill sea birds.

deanna d alessandro

Helene Marsh bottle feeding a dugong

graham Robertson Dr Graham Robertson is trying to find ways to reduce the number

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One way to make electricity without burning fossil fuels is by using solar cells. Solar cells convert the sun s light into electricity. Traditional solar cells are only about 12 per cent efficient, so very large panels are needed to produce small amounts of electricity.

Tim Flannery

RemembeR 1 define the terms renewable and non-renewable. 2 Recall four examples of renewable resources. 3 contrast renewable and nonrenewable energy sources and provide two examples of each.

Think 4 The words listed below are used on pages 415 417. Match each word with its meaning. Words Landfill

Meaning Process waste in such a way that a new product can be made from it

Compost

Teeth that stick out of the mouths of elephants and dugongs

Recycle

Dead body

Dugong

A method of waste disposal where rubbish is dumped into holes in the ground and covered with dirt

Tusks

Something used to attract an animal

Carcass

The number of organisms living in a country or area

Abundance A way of disposing of plant matter, paper and food scraps where bacteria and worms break it down until it can be spread over the garden Bait

How many organisms live in a particular area

Population

A marine mammal

Year Blue whales killed Fin whales killed Sei whales killed Sperm whales killed Totals

invesTigaTe

5 contrast re-using and recycling.

activities

1930 25 000 14 000 1000 1000

6 Soft-drink bottles are recyclable. Toilet paper can be made from recycled paper. explain the difference between the terms recyclable and recycled . 7 Most councils now issue recycling bins. Recall some items that can go in your recycling bin. 8 What are some advantages and disadvantages of using solar panels to produce electricity?

Use daTa The data in the table below has been adapted from PR & AH Ehrlich, Population, Resources, Environment (WH Freeman, San Francisco, 1972).

13 Use the library or internet to find out more about one of Australia s most threatened vertebrate species. Write a short report, or design a poster, and include the following information: (a) a description of the animal and its habitat (b) a list of the animal s requirements (including food and shelter) (c) reasons why the animal is threatened with extinction (d) what, if anything, is being done to save the species. Choose your vertebrate from the species listed below. mountain pygmy possum, Leadbeater s possum, spotted-tailed quoll, dugong, southern right whale, humpback whale, western blackstriped snake, western swamp turtle, platypus frog, trout cod, bar bar frog, mallee fowl, helmeted honeyeater, golden-shouldered parrot, yellow-bellied parrot

◗ Calculate the total for each

column and construct a column graph showing the data for all four whales, and the totals, on a graph, using the same set of axes for all of them. Put the years on the horizontal axis (scale of 1 cm = 5 years, starting at 1930) and the numbers of whales killed on the vertical axis (scale of 1 cm = 5000). Use different colours for the different whales and the total numbers, and include a legend to show which colour represents which whale.

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14 The solar cube is another type of solar panel that Australians are working on. Use the Solar cube weblink in your eBookPLUS to find out why it is more efficient than traditional solar panels.

9 Which whale was killed less and less over the whole period?

15 Play the Survival game in your eBookPLUS and test your knowledge on how you can help to save the environment. int-0217

10 When was the total number of whales killed the greatest? 11 (a) What can you say about the rate of killing whales after 1965? (b) Why do you think this happened? 12 Why do you think there were fewer whales killed in total in 1940 than in 1930? 1940 15 000 14 000 1000 5000

1950 7000 23 000 3000 12 000

16 Complete the Threats to Earth interactivity in your eBookPLUS and spot the differences in an environment before and after human contact. int-0218

1960 3000 32 000 8000 20 000

1965 2000 20 000 25 000 30 000

1970 0 5000 15 000 23 000

15 Ecology 417

LooKIng BaCK 1 Read the following statements. Decide if they are true or false. Correct any statements that are false by rewriting them. (a) A habitat is the place where an organism lives. (b) An ecosystem is the conditions within a place that affect the animals and plants. (c) The idea that the whole Earth functions as one complete organism is called the theory of Gaia. 2 Identify what a habitat needs to supply for animals to survive. 3 Identify what a habitat needs to supply for plants to survive. 4 Redraw the table below to correctly match the heads and tails. Heads

Tails

(a) Herbivores are . . .

A organisms that produce their own food.

(b) Producers are . . .

B animals that eat plants.

(c) Consumers are . . .

C organisms that live in or on other organisms and obtain their food from them.

(d) Parasites are . . .

D organisms that break down dead plants and animals.

7 Describe the difference between a food chain and a food web. 8 Answer these questions about the food web shown below. (a) Identify the producer and describe how it gets its food. (b) Draw a food chain involving a producer, a first-order consumer and a second-order consumer. (c) Identify a third-order consumer. (d) How do the consumers get their food? (e) How many trophic levels are shown? (f) A magpie dies, but does not get eaten. Explain what would happen to its body. (g) Identify a herbivore and carnivore in the food web. (h) Identify an omnivore.

Kookaburra

Blue heron

(e) Decomposers are . . . E animals that eat other organisms. 5 Unjumble the words below to reveal some of the important terms in this chapter. Write down what each term means and give an example. (a) lotiolpun (b) phetypie (c) cudperro (d) ovinorme (e) dofo incah (f) asitreap 6 Copy the puzzle below into your workbook, then use the clues to complete it. (a) __ __ __ __ __ E __ __ __ __ __ __ (b) __ __ __ __ __ N __ __ __ __ __ (c) __ __ __ __ __ V __ __ __ __ (d) __ __ __ __ __ I __ __ __ (e) __ __ __ __ __ R __ __ __ __ __ __ (f) __ __ __ __ __ O __ __ __ __ __ __ (g) __ __ __ __ __ N __ __ (h) __ __ __ __ __ M __ __ __ __ __ __ (i) __ __ __ __ __ E __ (j) __ __ __ __ __ N __ __ __ __ __ (k) __ __ __ __ __ T __ __ __ __ __ __

418

Core science | stage 4 Complete course

Carpet snake

Mouse

Grasshopper Rabbit

Grass

Clues (a) Animals that eat the same sort of food, and live in the same area (b) Animals that are close to extinction (c) Meat-eating animals (d) A place where an organism lives (e) Plant-eating animal (f) A stable system made up of living and non-living things (g) Describes plants or animals that no longer exist (h) Organisms such as bacteria and fungi that break down plant and animal remains (i) A diagram that shows the feeding relationships of organisms in an ecosystem (j) Information about the number of organisms determined by sampling (k) The interaction between members of two species that benefits both species

9 Explain why so many plants are required to support just one octopus in the ecosystem represented by the biomass pyramid shown below.

6 larger fish

3 In an ecosystem A matter and energy are recycled. B only matter is recycled. C only energy is recycled. D neither matter nor energy is recycled.

6 small fish 500 plants

(1 mark)

4 The main role of bacteria and fungi in an ecosystem is to A recycle energy. B carry out photosynthesis inside plant cells. C prevent overpopulation by causing disease. D recycle minerals in dead organisms so that they are available to plants. (1 mark)

10 The powerful owl is an endangered species in Victoria. Logging has destroyed a lot of its habitat. Explain what would happen to the food web that the powerful owl is part of if it became extinct.

5 Classify the following as biotic or abiotic factors. Water Food Plants Sunlight Soil Climate Gases in the air Parasites Predators Shelter (2 marks)

The powerful owl is an endangered species.

11 Redraw the table below to match each type of relationship with an example. Example

(a) Competition

A Snakes hunt and eat mice.

(b) Predator prey

B Lampreys are fish that attach themselves to sharks. They feed on scraps of the shark s food and the shark is unaffected.

(c) Mutualism

C An aphid sucks the sap from a rose bush.

(d) Parasite host

D Male kangaroos fight each other for the attention of females.

(e) Commensalism

1 The abundance of a species refers to the A change in the number of individuals of that species over time. B area over which the species is found. C biotic factors that affect where an organism is found. D number of organisms in a particular area. (1 mark) 2 Sharks and other large fish often have smaller fish called remoras attached to their bodies. As the shark eats, small morsels of food escape from its mouth and the remora fish feed on these. The shark is not harmed by this. This relationship is an example of A parasitism. B predation. C competition. D commensalism. (1 mark)

1 octopus

Type of relationship

TesT YoURseLf

E Termites contain a fungus in their stomach that digests the wood they eat. The fungus cannot live anywhere else. Without the fungus, the termites would starve.

6 Construct a food web using the following information about a river ecosystem: • Snails eat water weed. • Mayfly larvae and tadpoles eat algae. • Water beetles eat mayfly larvae. • Tortoises eat tadpoles and snails. • Small fish eat tadpoles and snails. • Large fish eat water beetles and small fish. • Water snakes eat large fish. (4 marks) work sheets

15.8 Ecology puzzles 15.9 Ecology summary

15 Ecology 419

stUDY CHECKLIst

ICt

measuring ecosystems

eBook plus

■ define the following terms: ecosystem 15.1 habitat 15.1 distribution 15.1 abundance 15.1 collaboration 15.3 symbiosis 15.3 mutualism 15.3 parasitism 15.3 commensalism 15.3 epiphyte 15.3 saprophyte 15.3 extinct 15.9 endangered 15.9 consumer 15.4 producer 15.4 decomposer 15.4 adaptation 15.8 ■ identify examples of biotic and abiotic factors in ecosystems 15.1 ■ calculate an estimate of the abundance of a species using the quadrat method 15.2 ■ investigate some abiotic features in an environment 15.2

sUMMaRY

eLessons Global warming in Australia This video lesson looks at the phenomenon of global warming. Learn about greenhouse gases and why many scientists believe the Earth is getting hotter. Discover some of the potentially catastrophic effects this could have on the Earth, and learn how governments and individuals can address this global problem. A worksheet is attached to further your understanding.

Relationships in ecosystems ■ describe examples of the following interactions between species: parasitism, mutualism and commensalism

15.3

■ construct food chains and food webs 15.4 ■ describe the role of decomposers in ecosystems 15.4, 15.5 Searchlight ID: eles-0057

Photosynthesis and respiration ■ describe the role of photosynthesis and respiration in ecosystems

15.4

global warming ■ define the terms greenhouse effect and enhanced

interactivities The survival game This interactivity looks at the survival of the environment through a fun snakes and ladders style game. Play the game and test your knowledge on how you can help save the environment.

greenhouse effect 15.6 ■ outline strategies for addressing the issue of global warming 15.6

natural events ■ describe the effects of bushfires, floods and droughts on the environment

15.7, 15.8

■ describe examples of adaptations of animals and plants to Australian ecosystems

15.7, 15.8

solutions to environmental problems ■ outline some actions that high school students can take to protect the environment

15.9

current issues, research and development ■ investigate the work of some Australian environmental scientists

420

15.9

Core science | stage 4 Complete course

Searchlight ID: int-0217 Threats to Earth This interactivity looks at what is threatening life on Earth. See if you can spot the 10 differences in an environment before and after human contact. Instant feedback is provided. Searchlight ID: int-0218

16

Electricity

What does a battery have in common with a bolt of lightning? It turns out to be quite a lot. They both store electrical energy and transfer energy to allow electric charges to move. In this chapter you will investigate the nature of electricity and examine how electricity is used in our daily lives.

In this chapter, students will: 16.1 ◗ describe how an object gains an

electrostatic charge ◗ identify examples where the effects of

electrostatic forces can be observed ◗ describe the behaviour of electrostatic

charges when brought close together ◗ describe the electric field around

charged objects 16.2 ◗ describe the elements of an electric

circuit 16.3 ◗ describe how electric circuits transfer

energy ◗ construct circuits and draw circuit

diagrams to show the transfer of energy 16.4 ◗ outline how electricity can provide a

solution to our dwindling oil reserves.

Sparks caused by electricity discharging between two iron nails

16 Electricity Inside the atom An atom of boron contains five protons, six neutrons and five electrons. Draw and label a diagram to represent a boron atom. (Hint: see page 291 in chapter 11.)

Electricity around you 1. List as many examples as you can of when you have experienced static electricity. You might like to discuss these in pairs. 2. (a) What is lightning? (b) What do you think causes lightning? (c) Can you suggest the link between lightning and thunder? 3. (a) List all of the devices in your home that use: (i) electricity by connecting to a power point (ii) batteries only (iii) batteries and electricity from a power point. (b) Identify whether most of the electrical devices in your home use power points, batteries or both. (c) Construct a table like the one below and place each device you listed in part (a) in the appropriate column. (d) For which of the purposes listed in the table are the

most electrical devices used? 4. If you were restricted by law to only five individual electrical devices in your home, which five would you choose? Give a reason for each of your choices. 5. List any actions that you can take each day to minimise your use of electricity in your home. 6. Design a questionnaire that you can use to survey people over 30 years of age, to find out how electrical devices have changed during their lifetime. Use your questionnaire to survey: • at least one person between 30 and 40 years old • at least one person over 40 years old. (a) Summarise what you found out about how electrical devices have changed during the past 40 years. (b) What does your questionnaire tell you about how much people depend on electricity? 7. Draw a timeline to show how electrical devices have developed since the invention of the incandescent light globe by Thomas Edison in 1879. Some devices and their years of invention are listed below to

help you get started. Conduct some research to add at least three more devices to your timeline. • Electric elevator 1889 • Electric toaster 1908 • Electric kettle 1923 • Electric shaver 1928 • Electric photocopier 1938 • Microwave oven 1953 • Cassette tape recorder 1963 • Videotape recorder 1975 • CD player 1983 • DVD player 1995

Try this In which of the following electric circuits are the components correctly arranged so that the light globe will work? A

B

C

D

Purpose of electrical devices used in the home Heating and cooling

Lighting

Food storage and preparation

Cleaning

Personal grooming

Entertainment

Other

16.1

Static electricity You may have experienced static electricity when you removed a jumper or blouse. It sometimes causes your hair to stand up on end or creates little sparks that tingle. To explain the nature of static electricity, it is important to have a good understanding of the atom and the subatomic particles that make them up.

eBook plus

eles-0067

Electrons

Positive or negative? At the centre of each atom is a heavy nucleus. Surrounding the nucleus is a lot of empty space and tiny particles called electrons. Electrons are constantly moving around the nucleus. Each electron carries a negative electric charge. Inside the nucleus are two different types of particles. The protons inside the nucleus are much heavier than electrons. Each

-

Protons

Inside atoms The idea that all matter is made up of atoms originated in ancient Greek times around 2500 years ago. Experiments done in the 1800s and 1900s provided evidence for the existence of subatomic particles that today we call electrons, protons and neutrons. Scientists’ understanding of the structure of atoms has helped them to explain how objects can acquire an electric charge. Benjamin Franklin, an American scientist in the 1700s, was the first person to use the term ‘charge’. He also named the two charges positive and negative. Like the poles of a magnet, they are opposite to one another.

eLesson

Producing static electricity Learn about static electricity and watch it being produced by charging perspex and ebonite rods.

+ + ++ -

Nucleus

Neutrons

-

Benjamin Franklin discovered the electrical nature of lightning. There is some contention though whether he actually carried out this dangerous experiment.

proton carries a positive electric charge. The neutrons inside the nucleus are similar to protons but carry no electric charge. The positive electric charge of a proton exactly balances the negative charge of an electron. Atoms usually contain an equal number of electrons and protons. Any material that has more protons than electrons is said to be positively charged. Any material that has more electrons than protons is said to be negatively charged. Any material that has equal numbers of electrons and protons is said to be neutral. The term ‘uncharged’ is also used to describe neutral materials.

A neutral atom contains an equal number of protons and electrons. (Some of the protons are hidden in this diagram.) This diagram represents a carbon atom. The number of neutrons is not always the same as the number of protons.

The central part of the atom is called the nucleus. The nucleus is very small compared with the overall size of the atom. To give you an idea of the size of the nucleus compared with the whole atom, imagine this: If an atom was as big as the Sydney Cricket Ground, the nucleus would be the size of a marble placed at its centre.

16 Electricity 423

Getting charged

Standing still

Objects usually become charged by the addition or removal of electrons. This charge is called an electrostatic charge because, once an object gains an electric charge, it remains ‘static’ or stationary on that object, unless the charge is transferred to another object. Only in conductors (mainly metals) do charges move through the object, creating a ‘current’ of charge rather than a static charge. This will be discussed further. There are two ways that an object can gain an electrostatic charge: by friction or by contact with another object that is already charged.

The electricity that builds up on plastic rulers and balloons when charged and on the Van de Graaff generator is called static electricity. Static charge can leak slowly through substances such as rubber and air. When electric charge moves quickly, as it does through metals, it is no longer called static. Hence, the electricity that flows along wires in appliances is not static.

+

+ + +

+

+ +

+

– – – –

Rubbing a neutral material against another adds or removes electrons. When you rub a plastic ruler with wool, for example, electrons from atoms near the surface of the neutral wool are forced onto the neutral plastic ruler. The wool, having lost electrons, becomes positively charged. The plastic ruler, having gained electrons, becomes negatively charged.

–

If a neutral material is touched by a charged object, electrons can be transferred from atoms near the surfaces of the two objects. When the charged object is removed, the previously neutral material has gained or lost electrons. The student touching the dome in the photograph on the right becomes charged by contact and loses electrons to the dome. The student’s hair stands on end, as the positively charged strands repel one another. Electrons are the easiest particles to add to or remove from atoms, because they are not held tightly in the nucleus as protons are.

Core Science | Stage 4 Complete course

Dome

+

–

– – – –

– – – –

+

+

+

Rollers

+ +

By friction

By contact

424

+

+ Belt

–

–

–

–

–

Metal object

–

–

– – –

– –

A Van de Graaff generator has a large rubber belt held tightly between two rollers. When the motor is turned on, the belt rotates. As it moves, the belt rubs against the rollers. Electrons are transferred from the top dome, which is in contact with the rubber belt, to the top roller. This leaves the dome with a build-up of a large positive charge. Bringing a metal object near the dome allows electrons to flow to neutralise the charge on the dome, and this produces a spark. The spark you see is the dome discharging. The Van de Graaff generator was first built in 1929. Its purpose was to smash atoms to find out more about them. A static charge builds up on the dome. A student’s hair can stand on end in an experiment with the Van de Graaff generator.

INVESTIGATION 16.1 The attraction of electricity You will need: 2 balloons woollen cloth

light thread metre ruler

◗ Suspend one balloon from the metre

◗ Remove the cloth and position

the balloons so that they are as close together as possible without touching each other. Observe any movement of the balloons.

1

Describe the movement of the single balloon.

2

Does the balloon have the same charge as the woollen cloth after it is rubbed? Explain.

3

Describe the movement of the two balloons.

4

After being rubbed with the woollen cloth, do the balloons have like or unlike electric charges? Explain.

5

Copy and complete the following sentences by choosing the correct word from the pair of underlined words.

Metre ruler 1m

ruler with light thread, as shown in the diagram. ◗ Rub the balloon with a woollen

DISCUSSION

Light thread

cloth. ◗ Remove the woollen cloth and then

place it close to, but not touching, the part of the balloon that was rubbed. Observe any movement of the balloon.

Balloon

Objects with like charges attract/repel each other.

◗ Suspend a second balloon from the

metre ruler so that it is close to, but not touching, the first balloon.

Objects with unlike charges attract/repel each other.

◗ Rub each of the balloons with

a woollen cloth — rub on the surfaces that are facing each other.

Suspend a balloon from a metre ruler.

INVESTIGATION 16.2 The Van de Graaff generator CAUTION Your teacher will carry out this activity. Do not touch the charged dome of a Van de Graaff generator unless instructed to by your teacher. Always use an earthed rod to discharge. Carry out the demonstration while standing on a plastic tray. You will need: Van de Graaff generator several strands of wool

Part B ◗ Tape several

strands of wool onto the dome. Make sure they are spread out over the surface of the dome. Turn the generator on and let it charge up once more.

Part A ◗ Turn the Van de Graaff generator on and let it charge up.

Bring the earthed metal rod near it. ◗ Turn the generator off and discharge it using the earthed

metal rod.

DISCUSSION DISCUSSION

1

What happens to the wool?

1

What do you observe occurring between the rod and the dome when it is turned on?

2

Explain why this happens in terms of the charges on the dome and on the wool.

2

Explain your observation. Use words like charging and discharging in your explanation.

3

The wool forms a pattern around the dome. Explain why this pattern forms.

16 Electricity 425

All charged up Objects with the same charge repel each other while those with opposite charges attract each other. If sufficient charge builds up in oppositely charged objects, the attraction between the electric charges is so great that they can jump across small air gaps. Lightning is caused by the movement of electric charge between a cloud and the ground. However, the clouds and ground are both neutral! Lightning seems to show that electric charge can move between neutral objects as well as between oppositely charged objects. The explanation for this can be found on the next page.

But it wasn’t charged! Charged objects and neutral objects can be attracted to each other. A charged plastic pen attracts a neutral stream of water. A charged balloon sticks to a neutral wall. A charged comb will make dry hair stand up. The illustration below shows how a negatively charged plastic pen is able to pick up a small, neutral piece of paper. Only a few charges have been labelled in the illustration. In reality there would be millions and millions of them. The labelled charges are there to show whether an object is neutral or charged, and how the charge is arranged in the object.

When the negatively charged pen is close to the paper, electrons are repelled from the top surface of the paper, leaving the surface with a positive charge. Note that the whole piece of paper is still neutral. If there is enough charge and the pen is close enough to the paper, the force of attraction is great enough to pull the paper up. Once the paper is touching the pen, the charge moves across and arranges itself so that it is evenly spread out.

Mapping electric force Any charged object either pushes or pulls on other charged objects around it. A positively charged object exerts an attractive force on a negatively charged object

and exerts a repelling force on a positively charged object. A diagram can be drawn to represent the electric force around a charged object. The area around the charged object is called the electric field. The electric field lines are closest together near the charged object. This is where the force is strongest.

INVESTIGATION 16.3 Defying gravity You will need: plastic ballpoint or felt-tip pen woollen, cotton or nylon cloth balloon ◗ Rub a plastic pen with a piece

of cloth, then hold it near a thin stream of water from a tap. ◗ Describe what happens to the

+

water. ◗ Rub an inflated balloon with

the woollen cloth and place it against a wall. ◗ Does the balloon stick to the

wall? ◗ If the balloon does not stick to

– This diagram illustrates electric fields around a positive and a negative charge. The field lines always show the direction of the force that would be applied to a small positive charge placed in the area.

the wall, try rubbing it with a different type of cloth.

DISCUSSION 1

Explain the behaviour of the water and balloon in your own words.

2

Explain the effect of the cloth on the balloon.

Negatively charged pen

Neutral paper Electrons are repelled from the top surface of the paper. Charged and neutral objects can be attracted to each other.

426

Core Science | Stage 4 Complete course

Positively charged surface is attracted to the pen.

When lightning strikes The particles of water and ice inside clouds are constantly moving against each other. Their movement causes charge to build up in the cloud. Some parts of the cloud become more negative, while other parts become more positive. The charges keep building up. Eventually, there is so much charge built up in part of the cloud that it quickly discharges to another cloud or to the ground below. The result is the spectacular spark we call lightning. If a bolt of lightning strikes a building, it can cause a huge amount of damage. It is known that lightning takes the easiest path to the ground, so lightning rods are attached to the top of tall buildings.

It is more likely that lightning will strike the rod, keeping the rest of the building safe. Although lightning is spectacular to watch, it can also be very dangerous. Make sure you do not talk on the telephone during an electrical storm. Lightning can strike the phone line and travel to every phone on the line. Mobile or cordless phones are much safer. It is also unsafe to be outside during an electrical storm. Take shelter inside a building or in a car. Never take shelter under trees, as they are often struck by lightning.

When getting out of a car is a hazard A moving car is a great charge builder. As a car moves, its body

Some parts of the cloud become negatively charged, other parts become more positively charged.

rubs against the air and its tyres rub against the road. The rubbing can cause charge to build up on the car and its passengers. As you get out of the car and go to touch the metal body, a spark crosses the small gap between your hand and the metal just before you touch it.

Static electricity is a hazard in an operating theatre. Charge can build up on blankets and discharge quickly, causing a spark. Many of the instruments used in an operating theatre can also create sparks. This is very dangerous because operating theatres use gases that could easily explode. Doctors and nurses wear gowns made from natural fibres that do not build up electric charge easily. The patient and all of the equipment are earthed. An object is earthed when it makes contact with the ground. By earthing the patient and any equipment, charge flows to the ground before it can build up and cause a spark.

Built-up charge discharges to the ground during a lightning flash.

The heat created during a lightning strike heats the nearby air to a very high temperature. The air suddenly expands and produces the crashing sound we know as thunder.

16 Electricity 427

When cleaning makes things dusty When you use a cloth to wipe over furniture it can sometimes make matters worse. Rubbing leaves the surface with an electric charge that can attract small dust particles in the air. The dust particles are neutral and will be attracted to either a positive or negative charge left on the furniture. Using a furniture polish reduces the attraction between the furniture and dust particles by helping built-up charge to leak into the air. Have you ever noticed that your computer screen is dustier than thee nt rest of the computer? Television and computer screens are excellent dust collectors. Charges build up on the screen, attracting dust particles.

Activities REMEMBER 1 (a) Identify which two particles of an atom carry electric charge. (b) Identify which type of electric charge each of these particles carries. 2 When you rub a plastic ruler with a woollen cloth, the plastic ruler becomes negatively charged. (a) Describe what happens to the atoms in the cloth and ruler to cause this change. (b) Complete the following sentence. As the ruler becomes negatively charged, the cloth becomes _____________ charged because it has more _____________ than electrons. 3 Complete each of the following sentences by using the words ‘attract’ and ‘repel’. (a) Two positively charged objects would be expected to _________ each other. (b) Two negatively charged objects would be expected to __________ each other. (c) A positively charged object would be expected to __________ a negatively charged object. 4 Explain, with the aid of a diagram, how it is possible for a neutral object to be attracted to a charged object. 5 What is the release of built-up charge called?

THINK 6 In the diagram of the carbon atom on page 423, some of the protons are not visible. How many are hidden by other protons? 7 Two balloons are hanging on threads next to each other, but not touching. They begin to move away from each other. If one of the balloons is positively charged, identify the charge of the other balloon. 8 Explain why the student touching the dome of a Van de Graaff generator on page 424 would be wearing rubber-soled shoes and standing on a plastic mat.

428

Core Science | Stage 4 Complete course

9 Work out from the following list of observations whether balloons A, B, C, D and E are positively or negatively charged. ◗ Balloon A is attracted to balloon B. ◗ Balloon C repels balloon A. ◗ Balloon D is attracted to balloon E. ◗ Balloon B repels balloon D. ◗ Balloon E is positively charged. 10 If a pen is rubbed with a woollen cloth, it can attract a piece of paper. (a) Is the pen neutral or charged? (b) Is the paper neutral or charged? 11 Draw a labelled diagram to show how a neutral stream of water from a tap is attracted to a charged plastic pen. Use the symbols + and – to represent positive and negative charge.

INVESTIGATE 12 Have you ever heard a crackling sound when you remove your clothes at night? What causes it? Design and carry out an investigation to test which types of clothes are most likely to cause the crackling. 13 Search the internet to find out how many people are struck by lightning each year in Australia.

CREATE 14 Devise a model, using people to represent positive and negative charges, to show how objects become positively and negatively charged. Use your model to demonstrate: (a) whether a neutral object contains any electric charges (b) what must happen to make an object (i) negatively charged (ii) positively charged. work sheets

16.1 Positive and negative 16.2 Charging up! 16.3 Attraction and repulsion

16.2

Electric circuits At the flick of a switch, you can turn on a light, play a song on your mp3 player or use a computer. Electrical energy makes these appliances work by changing into light, sound or other useful form of energy.

Moving electricity Static electricity results when positive or negative charge builds up in a non-conductor because there is no easy path for electrons to move. The electricity that flows out of a power point or battery is not static but can travel through a path called an electric circuit. Just as electrons are transferred in static electricity, electrons are the charges that travel through electric circuits. Interestingly, electrons weren’t discovered until the 1900s, well after electricity had been described and so, originally, it was thought that positive charges travelled through electric circuits. A battery or other power supply gives the electrons energy to move around a circuit. This energy is called electrical energy. Electrons keep moving until the power supply is removed or the path is broken.

Completing a circuit When you switch on a light or torch, turn on a computer or press ‘play’ on an mp3 or a DVD player, you are closing an electric circuit. This allows electric charges (electrons) to travel around the circuit. These charges carry electrical energy, which is transformed to useful forms of energy by electrical components in the circuit.

circuit. The connecting leads provide this path.

The essentials of electrical circuits For an electric circuit to do its job of converting electrical energy to another useful form of energy, three things are necessary: • a power supply, such as a battery, to provide the electrical energy. In most household appliances the power supply is connected by plugging into a power point. • a load, such as a light globe, in which electrical energy is changed into other forms of energy. • a conducting path so that electric charge can flow around the

INVESTIGATION 16.4 Making the right connections Try this investigation at the start of this unit. You will need: two 1.5 V batteries two 3 V globes 3 wire leads Blu-tak Activity 1 ◗ Using the equipment provided, how would you connect a battery to a single light globe so that it glows? Try it out until you’ve got it working. ◗ Record your successful set-up as

a labelled diagram.

DISCUSSION 1

What did you try that didn’t work?

2

Where does the electrical energy come from?

3

In which direction do you think the electric charges flow? Label it on your diagram.

An mp3 player changes electrical energy into sound energy.

Activity 2 ◗ How would you connect two batteries to a single light globe? Try it out until you’ve got it working. ◗ Record your successful set-up as

a labelled diagram.

DISCUSSION 4

What effect does providing a second battery have on the light? Explain why.

Activity 3 ◗ How would you connect two light globes to a single battery so that you get a: (a) bright glow (b) dim glow? ◗ Record your successful set-up as

a labelled diagram.

DISCUSSION 5

Explain your results.

16 Electricity 429

Current and voltage — what’s the difference?

INVESTIGATION 16.5 Switched on circuits You will need: 3-volt globe and holder 1.5-volt battery and holder 5 connecting leads with alligator clips or banana plugs 2 tapping switches Part A ◗ Connect circuit 1 as shown.

DISCUSSION 1

How can you stop the globe in circuit 1 from glowing?

Part B ◗ Connect circuit 2 as shown.

Circuit 1

◗ Close the switch. ◗ If nothing happens, open the

switch, check that your circuit is connected properly and try again. If nothing happens this time, replace the globe.

Conductors and insulators

◗ Open the switch and

remove the globe from its holder. Close the switch.

Circuit 2

DISCUSSION 2

Describe what happens to the globe in circuit 2 when the switch is closed.

3

Does the globe light up when it is removed? Why not?

DISCUSSION

430

Explain what happens to the light globe in circuit 3 when: (a) neither of the switches is closed (b) either one of the switches is closed (c) both of the switches are closed.

Core Science | Stage 4 Complete course

The cords that plug into power points from electrical appliances are coated in plastic. Electricity can pass through the metal wires inside the cord because metal is an electrical conductor. It cannot pass through the plastic because plastic is an electrical insulator. Without the plastic, electricity could pass through to any person touching the cord.

Transporting electricity

Part C ◗ Put the globe back in its holder and add a second switch as shown in circuit 3.

4

As we now know, electrons are the carriers of electric charge around a circuit. The rate of flow of electric charge through an electric circuit is called the electric current. An electric current is a measure of how much electric charge passes a given point in the circuit per second. The unit of electric current is the ampere, which is commonly abbreviated to amps (A). The voltage of the battery or other power supply is a measure of how much energy is available to push the charges through the circuit. If the circuit is not closed, current cannot flow and the electrical energy cannot be used to move the charges around. The unit of voltage is the volt (V).

Circuit 3

To get to our homes, electricity travels through metal cables. The cables are usually high above the ground out of reach. It is important for the electricity to travel along the cables, but not through the poles that support the cables. For this reason, power poles are often made of wood or concrete. Both of these substances are insulators.

Metals and non-metals Conductors allow electrons to flow through them. Most metal objects are conductors of electricity because some electrons in the atoms of metals are free to move. When wires of metal are connected to a power supply, free electrons in the wires move through the wires to create an electric current. Insulators do not allow electrons to flow through them. Many objects made from non-metals are insulators. The electrons inside insulators are strongly bound to the nucleus of the atoms and cannot move easily. Free electrons

Positively charged nuclei of atoms Electrons in conductors are free to move.

The volt and the ampere, the unit of electric current, were named after two men who made important discoveries about electricity more than 50 years before Thomas Edison invented the electric light globe. Alessandro Volta (1745–1827), an Italian physicist, invented the first electric battery in 1800. His full name was Count Alessandro Giuseppe Antonio Anastasio Volta. Count Volta discovered that a moist cloth placed between two different metals could produce a small electric current. The first electric battery is known as the voltaic pile and consists of alternating disks of copper and zinc. Each pair of copper and zinc discs was separated by a piece of cloth soaked in salty water. Volta’s ‘electric organ’, as he called it, was about 30 cm high. André Ampére (1775–1836) was a French mathematician with an interest in physics and chemistry. According to some historians, he had mastered all known mathematics by the age of 12. He is best known for his discovery that two nearby parallel wires carrying electric current could attract or repel each other.

–

Count Volta’s pile

◗ Place each item in turn between

INVESTIGATION 16.6 Conductors and insulators

+

the alligator clips. Light globe

You will need: light globe and light-globe holder battery or other power supply (no more than 6 V) 3 connecting wires (at least 2 with alligator clips) objects to test (for example, copper sheet, paper, plastic, coin, fabric, iron nail, glass, ice-cream stick, paperclip and aluminium foil).

◗ Complete the table for each item as

you test it. Alligator clips Material to be tested

Battery

DISCUSSION 1

List the items that conducted electricity.

2

What is the purpose of the light globe?

3

Look at the items that are conductors of electricity. What do they have in common?

◗ Set up the equipment as shown. ◗ Draw up a table like the one below.

Object

Light globe on or off?

Conductor or insulator?

4 (a) Is air a conductor of electricity? (b) How can you test to see if it is? 5

Are the alligator clips conductors or insulators? Explain your answer.

16 Electricity 431

A light in the dark Many battery-operated devices use more than one battery. In torches, portable radios, and mp3 and CD players, two or more batteries are connected in series. The batteries are connected end-to-end as shown in the diagram on the right. It is important to ensure that the positive end of one battery is connected to the negative end of the other.

Circuit diagrams: a common language Diagrams of electric circuits need to be drawn so that people all over the world can read them. Circuit diagrams use straight lines for connecting leads and symbols for other components of circuits. Connecting wire

Two wires crossing over one another

Resistor

Cell

Battery (two cells in series) Light globe

A

Ammeter

V

Voltmeter

Filament This small coil of wire in a globe is called a filament. When a current passes through a globe, the filament gets hot and produces light. The electrical energy from the batteries is changed into light and heat energy in the filament.

Globe base The globe base is connected to the metal strip and the batteries.

Switch When the switch is open, the metal strip does not make contact with the base of the globe. A current cannot flow. When the switch is closed, the metal strip is forced against the base of the globe to complete the circuit. The electric current then flows.

Metal strip The metal strip completes the circuit between the batteries and the globe. A torch is a simple electric circuit.

Two wires joined

Switch closed

Switch open Some circuit symbols

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Circuit diagram for a torch

Plastic covering The plastic cover is an insulator and so doesn’t allow a current to flow through it.

Batteries Batteries provide electrical energy for the torch to work. The energy stored in each battery forces electrons to move from the negative terminal through the circuit and towards its positive terminal at the other end. This can happen only if the battery is part of a closed circuit. Voltage These batteries are 1.5 volts (V ) each. Together, the two batteries provide 3 V to the torch. The voltage is a measure of how much energy the battery gives the electrons to move them around the circuit. Notice how they are connected end to end, with the positive terminal of one battery against the negative terminal of the next.

Spring The spring keeps the batteries in contact with the base of the globe.

The torch circuit The power supply of a torch usually consists of two or more 1.5-volt batteries connected in series. When two 1.5-volt batteries are connected in series, the total voltage supplied to the circuit is 3.0 volts. This means that twice as much electrical energy is available to move the electric charge around the circuit. The load in a torch circuit is the globe. When the switch is closed, electric current flows around the

circuit. As electric charge passes through the globe, its electrical energy is transformed to heat in the filament. The filament inside the globe is made of the metal tungsten and glows brightly when it gets hot. The conducting path in a torch consists of the spring that pushes the battery against the base of the globe (or a metal globe holder) and the metal strip that includes the switch. When the switch is open, the metal strip does not make contact with the globe and the circuit is not complete.

APPLY

Activities

13 Draw a circuit diagram containing a battery, two globes in series and an open switch.

REMEMBER

14 Use symbols to draw a circuit diagram of the circuit used in activity 2 of Investigation 16.4 on page 429.

1 Define the term ‘closed circuit’. 2 Identify the part of an electric circuit in which electrical energy is changed into other useful forms of energy. 3 Identify which terminal of a battery electrons move from. 4 Define the term ‘voltage’. 5 State the name given to materials that allow electrons to flow through them. 6 Explain the purpose of the plastic coating around electrical cords.

CREATE 15 Construct a steady-hand tester. You will need a wire coathanger, a loop of thin wire, wire cutters, battery, electric bell or light globe, connecting wires, and a shirt box, shoe box or cereal packet for the base. Bent coathanger

7 Explain why metals are better conductors of electricity than non-metals.

Base

THINK 8 Explain how electricity transmission towers can be made from metal but not conduct electricity from the cables to the ground. Light globe or electric bell

9 If three 1.5-volt batteries were used to power a torch, calculate the voltage they would provide to the torch. 10 Explain why it is important to have circuit symbols that are recognised by scientists and electricians around the world. 11 Identify which of the following arrangements will cause the globe to light up.

Battery A steady-hand tester. The ‘alarm’ can be a bell hidden in the base or a globe attached to the base. Hide as much of the connecting wires as you can. eBook plus

12 Describe how a torch works. Use the words ‘current’, ‘energy’ and ‘circuit’ in your description. A

B

C

D

16 Use the Electric circuits weblink in your eBookPLUS to play a series of games that test your knowledge of simple circuits.

work sheets

16.4 Simple circuits 16.5 Series and parallel circuits 16.6 Conductors and insulators

16 Electricity 433

16.3

Electricity at work Series circuits Do you remember how the parts of the torch on page 432 were connected together? The circuit contained several components, connected one after the other. Conductors, like the metal strip and the light globe case, linked the components. The circuit was a single, complete loop. This type of circuit is called a series circuit. The good thing about series circuits is that they are simple to put together. But if any part of a series circuit doesn’t work, such as one of the globes in the first circuit below, none of the circuit will work. A series circuit will not work if even one part of it breaks down.

When batteries are connected in series, electrons flowing through the circuit must flow through each battery. The electrons are given electrical energy from each battery. Note that the positive terminal of one battery is joined to the negative terminal of the other.

The ammeter

An ammeter is always connected in series. This way, the electrons that flow through the circuit will also flow through the ammeter. The circuit symbol for an ammeter is shown below.

An ammeter is a device that measures electric current, which is the rate of charge flowing through a circuit per second. The more electrons that flow through the circuit per second, the higher the current and the higher the ammeter reading.

A

This ammeter measures milliamperes. 200

100

0

30

0

50

20 DC 30 mA

0

10

40

0

0

40

The negative (black) terminal of the ammeter is connected so that it is closer to the negative terminal of the battery than to the positive terminal.

50

— 500

mA

50

mA The positive (red) terminal of the ammeter is connected closer to the positive terminal of the battery. Select the positive terminal with the highest value first. If the current is too small to register on this scale, switch to the more sensitive terminal.

Both of these circuits are series circuits. The componens in these circuits are connected in series.

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There are usually two or more scales on an ammeter. Your selection of positive terminals tells you which scale to read.

CAUTION An ammeter is easily damaged. If the current reading goes off the scale, open the circuit immediately.

The voltmeter The energy that electrons have as they move around a circuit comes from a battery or other power supply. As the electrons move around the circuit, some of their energy is transformed into other forms of energy by the appliances in the circuit. The energy that is transformed by components along the circuit is measured in volts using a voltmeter. Like an ammeter, a voltmeter is placed in a circuit with its positive terminal closer to the positive terminal of the power supply than the negative terminal. But, unlike an ammeter, a voltmeter is connected parallel to a component in a circuit. The symbol for a voltmeter is shown below.

Parallel circuits Imagine what would happen if the electrical appliances in your home were all connected in series? Every time a light blows out, no other electrical appliance would work. To avoid this problem, most circuits contain components connected in parallel. This means that each component is connected in a separate path. A parallel circuit works even when one part of it breaks down.

At point A, the electrons can move along either the first path or the second path. If the paths are identical, half of the electrons will take the first path and the other half will take the second path. Although the electric current is divided between the two paths, electrons in each path will carry the voltage (energy) provided by the battery (power source). Second path

V

Christmas lights — if these lights are connected in parallel, when one light blows out, the others still work.

First path

The voltmeter in this circuit tells us how much of the electron’s energy is turned into light energy. This light globe uses almost all of the energy given to the electrons.

A

Electrons Electrons

This battery gives 1.5 V of energy to the electrons as they leave the battery.

1.5 V +

–

5

0

10 0

1 Volt

s

2

15

A parallel circuit has more than one path for the electricity to follow. If one of the paths has a break in it, the other paths will still work. Only components in the broken part of the circuit will stop working.

3

— 15

V

3V

A parallel circuit drawn as a circuit diagram.

Voltmeters can measure how much energy electrons lose as they pass through a component.

16 Electricity 435

INVESTIGATION 16.7

7

Series and parallel You will need: two 3-volt globes and holders 1.5-volt battery and holder 6 wire leads Part A: Series circuits ◗ Connect one globe and the battery together with wire leads so that the globe lights up. ◗ Add a second globe in series with

What would be the effect on the other globes if a third globe were added in series? If a third globe is available, test your prediction.

Part B: Parallel circuits ◗ Connect the two globes, battery and wire leads as shown in the diagram below. ◗ Remove one globe from its holder. ◗ Replace the globe that was

removed, then remove the other one.

the first globe as shown in the diagram below. ◗ Remove one globe from its holder. ◗ Replace the globe that was

removed, then remove the other one.

What affects brightness? The brightness of each globe depends on both the voltage and the electric current. In series circuits, the electrons share their energy (voltage) among all of the globes in the circuit. The more globes there are, the more the energy needs to be shared and the less brightly they glow. The branches of a parallel circuit do not share the energy carried by electrons. So, identical globes placed in parallel glow with equal brightness. No matter how many branches are added to a parallel circuit, the brightness of each identical globe is the same.

Globes connected in parallel

DISCUSSION Globes connected in series

8

Draw a circuit diagram to represent the circuit that you have connected.

How does the brightness of the two globes compare with the brightness of a single globe connected to the same battery?

9

How does the brightness of the two globes compare with the brightness of a single globe connected to the same battery?

What effect does the removal of one globe have on the other globe?

10 Does it matter which globe is removed?

DISCUSSION 1

2

436

3

What effect does the removal of one globe have on the other globe when the battery is connected?

4

Does it matter which globe is removed?

5

Can electric current flow in this series circuit when either globe is removed?

6

Would it be sensible to have all of the ceiling lights in your home connected in series? Give a reason for your answer.

Core Science | Stage 4 Complete course

11 Can electric current flow in this parallel circuit when either globe is removed? 12 Outline whether the removal of one globe has any effect on the other globe. 13 What would be the effect on the other globes if a third globe were added in parallel? If a third globe and enough connecting leads are available, design a circuit to test your prediction.

These lights are connected in parallel. Why?

What about in your home? All globes are connected in parallel but, because they are not all identical, some may glow more brightly than others. This is because the electrons flowing through each globe receive the same voltage, but the electric current flowing through the globes in each parallel branch differs. The numbers printed on light globes tell us how quickly the globes use energy. A 23-watt light globe uses energy more quickly than an 11-watt light globe and so it shines more brightly. The electrons that pass through these globes carry

the same amount of energy (240 V in Australia). But a greater current passes through the 23-watt globe than the 11-watt globe in any given time. So, current, as well as voltage, affects brightness.

Electricity in a packet The electrical energy needed to operate most electrical devices in the home and at school is obtained by plugging into a power point. Much of the electrical energy used in NSW is provided by power stations in the Hunter Valley. Batteries are portable. They are mostly used to provide electrical energy in devices that need to be moved about. They can also be used in devices such as smoke detectors as a backup in case of a power failure. A car battery

Alkaline zinc/manganese dioxide batteries

A button battery

flow. A chemical reaction takes place inside the cell, creating an electric current.

Dry cells The general-purpose cells used in torches, clocks, smoke detectors and toys are filled with a paste of chemicals. The two electrodes are: • a central rod of carbon, which is attached to the positive terminal of the cell • a zinc case, which is in contact with the negative terminal of the cell. When a conducting path is provided between the two terminals of the cell, a chemical reaction takes place between the paste and the zinc case. This releases electric charge, allowing an electric current to flow around the circuit. A separating layer stops the chemicals from reacting while the cell is not in use. These general-purpose cells are called dry cells because the electrolyte (the substance inside the cell through which electric charge moves) is not a liquid. Positive terminal Asphalt seal Air

Paste of chemicals Carbon rod

A rechargeable battery Separating layer Types of batteries

Zinc case

A battery is made up of two or more cells connected in series. However, in everyday language the word battery is used for a single cell. Each battery used in a torch is actually a single cell. An electric cell consists of a positive and a negative electrode and a substance through which electric charge can

Negative terminal A general-purpose dry cell

Other types of dry cells work in the same way but use different electrodes or electrolytes. Alkaline cells contain an electrolyte that allows a greater

The very first electric cell was created by accident over 200 years ago. Luigi Galvani, an Italian physician, was dissecting the leg of a recently killed frog. The leg was held by a copper hook. When he cut through the leg with an iron knife, the leg twitched. Galvani thought that he had discovered a new, special type of animal electricity. Several years later, it was realised that Galvani had produced the world’s first electric cell. Electric current had flowed from one electrode to the other through the tissue of the frog’s leg.

electric current to flow. They are ideal for heavy-duty torches, battery-operated shavers, mp3 players and digital cameras. Mercury cells produce a voltage that is much steadier than other dry cells. Their steady output makes them ideal for pagers, hearing aids, watches, calculators and measuring instruments.

9 and 12 V batteries Many of the cells you use provide 1.5 V of energy to the electrons in a circuit. When you purchase a 9 V battery, it is actually six 1.5 V cells joined together in series and placed in a single container. Cars are powered by 12 V batteries. Like other batteries, the chemical reaction in these batteries create free electrons, and other new products. One difference between car batteries and other batteries is that a car battery recharges when the car engine is running. The running engine reverses the chemical reaction in a battery. After a few years, the battery needs to be replaced because some of the products of the chemical reactions inside the battery build up, stopping it from recharging properly.

16 Electricity 437

Alligator clips

INVESTIGATION 16.8 Modelling an electric kettle You will need: 250 mL beaker 100 mL measuring cylinder 50 cm length of fine nichrome wire pen or pencil power pack 2 wire leads and alligator clips thermometer (preferably digital) or a data logger and temperature sensor stopwatch

+

Beaker +

AC

POWER SUPP LY VOLTS

–

DC

–

2

4

6 8

10 12

Water

Power pack

◗ Measure 100 mL of water into the

250 mL beaker. Nichrome wire coil

◗ Wind the middle of the nichrome

wire around a pen or pencil to make a coil from the wire. ◗ Connect the apparatus as illustrated

at right. ◗ Record the initial temperature of the

water before the power is switched on.

◗ Measure the temperature of the

DISCUSSION

water every minute for 15 minutes.

1

Describe the temperature change that you have observed.

2

Describe the energy transfer that is taking place.

3

Extrapolate your graph to predict the temperature after 20 minutes.

4

Predict the temperature change you would observe if 4 V was supplied to the coil.

◗ Record your data in a table like the

one below. ◗ Draw a line graph to illustrate the

temperature change.

◗ Set the power pack to 2 V, turn it on

and start the stopwatch. Time (min)

0

1

2

3

4

5

6

7

8

9

10

Temperature (°C)

INVESTIGATION 16.9

◗ Trial different arrangements of the

Microammeter

A lemon battery

0

100 10 0

00

lemons can be used to make an electric cell. A chemical reaction occurs between the different metals and the acid in the fruit so that electrons are forced to move around a circuit.

Core Science | Stage 4 Complete course

produced the maximum current, and record the current.

Galvanised nail

DISCUSSION

500

0 µA 500

µA 50 µ A

◗ Citrus fruits like

438

◗ Draw the arrangement that

5000

Wire lead

500 400 50 40

200 30 20 30 0 roa mp ere s

Mic

4000

You will need: 3 lemons range of nails (galvanised, iron, steel) 6 wire leads with alligator clips microammeter

30

0

lemons and metals to create the maximum possible current.

2000

1000

Lemon

◗ Squeeze each of the whole lemons

to break up some of the pulp inside.

1

What variables did you test to see if you could increase the electric current produced?

2

Which variables increased the electric current produced?

3

Outline the energy conversion that is taking place in this experiment.

12 What would be the readings on ammeters B and C in the circuit below?

Activities REMEMBER

C

1 Copy and complete the following sentences by choosing the correct word from the pair of underlined words. (a) When light globes are connected in series/parallel, the same electric current always flows through each globe. The globes share the voltage of the power supply. (b) When light globes are connected in series/parallel, the electric current splits and is shared by the globes. Each globe uses the same voltage. 2 Identify the instrument used to measure the size of an electric current.

A

A

A

A 50 mA

B

13 Look at the two circuit diagrams below. When the switches are closed in each circuit, the globes will glow.

3 Identify the terminal of an ammeter that should be connected to the positive terminal of a battery. 4 When a voltmeter is used to measure the transformation of energy by an electrical load, identify whether it is placed in series or parallel with the load.

Circuit 1

5 Explain why a 50-watt globe glows more brightly than a 25-watt globe. 6 Outline what takes place inside a cell to cause an electric current to flow. 7 Outline how alkaline cells differ from general-purpose dry cells.

Circuit 2

8 If a car battery can be recharged, explain why it can’t last for ever.

THINK 9 A circuit is set up as illustrated below.

A

B

(a) In which circuit will the globes glow more brightly? (b) Explain your answer to part (a) in terms of the voltage available for each globe.

CREATE

C

(a) If the filament of globe A breaks, do globes B and C remain lit or do they stop working also? (b) If the filament of globe B breaks, which globe or globes (if any) remain lit? (c) If the filament of globe C breaks, which globe or globes (if any) remain lit? 10 In a house, four light globes are connected in parallel. However, the lights are in separate rooms. This means that a separate switch is needed for each globe. Draw a circuit diagram of this circuit. 11 The filament in an electric light globe is a poor conductor of electricity. Would a filament made of a very good conductor of electricity light up? Explain your answer.

14 Design and create a circuit with two switches and an electric bell so that the bell rings when either one (or both) of the two switches is closed. Draw a picture and circuit diagram of your circuit. Invent your own symbol for the bell. If a bell is not available, use a light globe instead.

INVESTIGATE 15 Many battery manufacturers claim that their batteries are the best. Design an experiment to find out which brand of dry cell gives best value for money. Make sure your experiment is a fair one. work sheet

16.7 Testing batteries

16 Electricity 439

16.4

PRESCRIBED FOCUS AREA Applications and uses of science

The next generation of motor cars What sort of car do you expect to be driving thirty years from now? Will it be just a newer, sleeker, lighter version of the cars you see on the road today? How much will petrol cost: $2 per litre or $20 per litre? Most medium-sized cars have petrol tanks that hold between 50 and 80 litres. How much will it cost to fill the tank? Will you have trouble breathing the polluted air in traffic-clogged cities? It is unlikely that you will be driving a car with an engine powered by petrol. There are several reasons for this: • Petrol is made from oil and the world’s oil supply is rapidly decreasing. At the same time, the amount of oil being used is increasing. It has been predicted that the world’s oil reserves will run out in less than fifty years. • Petrol is becoming more expensive. As the cost of petrol increases, alternative fuels become more attractive. LPG (liquefied petroleum gas) is already increasing in popularity as a fuel for cars. • Petrol-driven car engines cause air pollution. Gases released from car exhausts include carbon monoxide (a poisonous gas), carbon dioxide (a major cause of global warming and a probable cause of climate change) and nitrogen oxides (which lead to smog and acid rain).

batteries is used to power the car’s motor, which turns the wheels. The batteries can be recharged while the driver is at home or at work. Electric cars have three main benefits: • Their use will reduce the demand for oil. The world’s oil reserves will last longer. • They do not release exhaust gases. This would reduce air pollution in large cities. • They are very quiet. There are also some drawbacks to electric cars: • Electric cars can travel only about 160 kilometres before the batteries need recharging whereas a tank of petrol allows most cars to travel between 400 and 800 kilometres before refuelling. • The batteries, which are very expensive, need replacing after a few years.

eBook plus

eLesson

The Australian International Model Solar Challenge Learn about the exciting annual event where Australian high school students compete by building and racing model cars and boats that are powered by solar energy. eles-0068

• Electric cars do not accelerate quickly and can usually reach speeds of only 100 km per hour. • Electric cars are more expensive to buy than petrol-driven cars. • If everyone owned electric cars, power stations would need to supply more energy for recharging their batteries. Although air pollution in cities would be reduced, the air pollution around the power stations would be increased.

Electric cars One of the most attractive alternatives to the petrol-driven car is a car powered by rechargeable batteries. Electrical energy from the

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The Tesla Roadster is a high performance electric car available in the USA from 2007. It can accelerate from 0 to 100 km/h in 4 seconds, has a top speed of 200 km/h and can travel 350 km before the batteries need recharging.

Solving the problems

capacitors) so that vehicle batteries require less frequent recharging.

Some of the disadvantages of electric cars will be overcome as the need to replace petrol-driven cars becomes more urgent. Engine Automotive engineers are using scientific principles, together with computer technology and modelling, to design lighter cars. They are also developing car bodies to reduce air drag. These changes will reduce the amount of energy needed to keep cars running. Batteries store energy. Electric cars that have been converted from petrol-driven cars need at least 12 standard Fuel tank Radiator lead–acid car batteries (connected in series) Electric motor to run at normal speeds. These batteries are very heavy. Research is continuing to develop lighter A hybrid car combines rechargeable batteries with a petrol batteries that will last longer. engine. As more electric cars are made, the cost of each car will decrease. Also, as petrol becomes more expensive, the higher cost of electric cars will seem to be less of a problem. New car designs, better batteries and decreasing costs make electric cars a very likely alternative to petrol-driven cars in the future. REMEMBER

Activities

The hybrid car The hybrid car combines a bank of rechargeable batteries with a petrol engine. It provides many of the benefits of an electric car but with better acceleration, and it can be self-recharging. They typically consume half the amount of petrol per kilometre that a conventional petrol-driven car uses. The exhaust fumes of hybrid cars still contribute to air pollution but to a much lesser extent than petrol-driven cars. While few models of electric cars are commercially available, there are many hybrid vehicles already on the market. Hybrid vehicles are particularly effective in stop–start city traffic. In some models, the energy normally lost as heat and friction when braking is transformed to electrical energy and used to recharge the hybrid vehicle’s battery. This system can save the energy equivalent of 1 litre of petrol over 100 km. Science is at the forefront of efforts to improve the technology in hybrid cars. For example, the CSIRO is working in partnership with car makers to develop more efficient lead–acid batteries for use in hybrid vehicles so they can be more compact and lightweight. Their research is also focused on developing electrical energy storage devices (called

1 List three benefits of electric cars. 2 State five disadvantages of electric cars at the current time. 3 Outline the features of a hybrid car.

THINK 4 Explain why electric cars are likely to become popular after being ignored for over 60 years. 5 Outline the disadvantages of electric cars that hybrid cars partially or entirely overcome. 6 State whether you think the government should force car manufacturers to stop making petrol-driven cars and replace them with electric or hybrid cars. Give reasons for your opinion. 7 Discuss whether society should support scientific research into new vehicle technologies.

CREATE 8 Create a poster or brochure advertising a model of hybrid vehicle to describe: ◗ the technology used in the vehicle (use clear language that is easy for your classmates to understand) ◗ its features (include labelled diagrams) and its performance ◗ the benefits of the vehicle over conventional petrol-driven cars.

16 Electricity 441

LOOKING BACK 1 Identify which of the following atoms is positively charged, which is negatively charged and which is neutral. (a) (b) (c)

10 Match each term in the following table with its correct description. Word

Description

Static electricity A material that allows current to flow through it

2 This Van de Graaff generator has an overall positive charge.

Electron

Positively charged particle in the nucleus of an atom

Proton

The build-up of charge on an object

Current

A material that does not allow current to flow through it easily

Voltage

Particle in an atom with a negative charge

Conductor

A path that has no breaks in it

Closed circuit

The energy supplied to move charges around a closed circuit

Insulator

The flow of charges around a closed circuit

11 Use symbols to draw circuit diagrams containing a light globe in series with an ammeter, a battery and a switch.

(a) Draw electric-field lines around the Van de Graaff generator. (b) Outline how the positive charge on the Van de Graaff generator could be discharged. 3 Explain why you should avoid standing under trees in a thunderstorm.

12 Use symbols to draw a circuit containing two globes in parallel with each other and with a battery. Place a switch in the circuit to operate both lights at the same time. 13 There is a mistake in each of the circuit diagrams below. Find the mistakes and then redraw the circuits correctly. (a)

(b)

4 When a plastic rod is rubbed with a certain cloth, the rod becomes positively charged. Predict the charge on the cloth. 5 State whether the following are true or false. (a) Objects with like charges attract. (b) Two neutral objects repel each other. (c) Neutral objects contain both negative and positive charges. (d) Objects with an overall negative charge still contain some positive charges. (e) If two objects repel, they must be positively charged.

–

A + +

V

(c)

6 A plastic spoon that has just been dried with a tea towel is placed near some pepper spilled on a kitchen bench. Some of the pepper is attracted to the spoon and sticks to it. Explain why this happens. 7 (a) As planes move through the air, they build up large amounts of static electricity. Suggest how this happens. (b) Before refuelling, a wire is used to connect the plane to the ground. Explain why this is important. 8 Explain how you can tell where an electric field is strongest. 9 Imagine you are a tiny particle carrying a small positive charge. Outline what will happen to you near a large: (a) positive charge (b) negative charge (c) neutral object.

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+

A

–

14 If a 9 V battery is used to power a circuit with four globes in parallel to each other, how many volts of electrical energy will each globe receive? 15 Why does a 12 W globe glow more brightly than a 24 W globe when connected in parallel, even though the electrons passing through each of them receive the same amount of energy?

–

16 Using the correct symbols, draw this circuit as a circuit diagram.

5

0

3 Identify which of the rows in the table below lists the series and parallel circuits among those shown here. Circuit 1

Circuit 2

Circuit 3

Circuit 4

Volts 10

0

1

2

15 3

— 15

v

3v

17 Catherine and Lauren used the circuit shown in the diagram on page 431 to test five materials labelled A–E. Their observations are shown in the table below. Catherine and Lauren’s data Material

Light globe (on or off)

Electric current (mA)

A

On

130

B

Off

0

C

Off

0

D

On

100

E

On

50

Series circuit(s)

(a) Identify which of materials A, B, C, D and E are conductors. Explain how you know. (b) Identify which of materials A, B, C, D and E are insulators. Explain how you know. (c) Identify which of the materials is the best conductor. Explain how you know.

Parallel circuit(s)

A

Circuit 3

Circuits 1, 2, and 4

B

Circuits 2, 3 and 4

Circuit 1

C

Circuits 2, and 3

Circuits 1 and 4

D

Circuits 3, and 4

Circuits 1 and 2 (1 mark)

4 If switches X and Z in the circuit diagram below are closed, identify the light globes that will be lit.

X

A

TEST YOURSELF B

1 When a plastic rod is rubbed with a nylon cloth the rod becomes positively charged. This is because the A plastic rod has gained protons. B nylon cloth has lost electrons. C plastic rod has lost electrons. D nylon cloth has gained neutrons. (1 mark) 2 A battery is connected to two identical globes that are connected in parallel. The current flowing through one globe is 400 mA. Identify which of the rows in the table below shows the current through the battery and the current through the other globe. Current through the battery (mA)

Current through the other globe (mA)

A

400 mA

800 mA

B

400 mA

400 mA

C

800 mA

800 mA

D

800 mA

400 mA

Y F C D

A B C D

None A, B and F C, D and E A, B, C, D and E

(1 mark)

5 Sam’s family is thinking of replacing their family car with a hybrid vehicle. However, it is probably 30 per cent more expensive than a comparable petrol-driven car. Outline the advantages and disadvantages of purchasing a hybrid vehicle. Make a judgement about whether Sam’s family should buy the hybrid vehicle and support your opinion. (6 marks) work sheets

(1 mark)

E Z

16.8 Electricity puzzle 16.9 Electricity summary

16 Electricity 443

STUDY CHECKLIST

ICT

Electrostatic forces

eBook plus

■ outline the components of an atom 16.1 ■ describe ways in which objects acquire an electrostatic charge 16.1 ■ describe the behaviour of charges when they are brought close to each other 16.1 ■ identify examples where the effects of electrostatic forces can be observed 16.1 ■ illustrate the electric field around a charged object 16.1

SUMMARY

eLessons Producing static electricity Learn about static electricity, how it is created and the effect that charged and uncharged objects have on each other when they are put together. Watch static electricity produced by charging perspex and ebonite rods. A worksheet is attached to further your understanding.

Electrical energy ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■

outline the essential parts of an electric circuit 16.2 compare conductors and insulators 16.2 define the current and voltage in an electric circuit 16.2 compare series and parallel electric circuits 16.3 identify symbols used in circuit diagrams 16.2, 16.3 define the terms ‘series circuit’ and ‘parallel circuit’ 16.3 use circuit diagrams to represent simple series and parallel circuits 16.3 identify the energy transfer taking place in an electric circuit 16.2, 16.3 outline how an ammeter is used to measure current in an electric circuit 16.3 outline how a voltmeter is used to measure voltage in an electric circuit 16.3 outline how batteries provide circuits with electric energy 16.3

Searchlight ID: eles-0067 The Australian International Model Solar Challenge Learn about the exciting annual event where Australian high school students compete by building and racing model cars and boats that are powered by solar energy.

Applications and uses of science ■ describe the principles that have been used in the development of electric and hybrid vehicles

16.4

■ discuss the positive and negative effects of petrol-driven vehicles and the new generation of electric and hybrid vehicles 16.4 ■ justify why society should support scientific research on alternatives to petrol-driven vehicles 16.4

Searchlight ID: eles-0068

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17

Staying healthy

The bacteria in this photo might be small but they can certainly make you very sick. Bacteria, viruses and fungi are examples of micro-organisms that can cause disease. Fortunately, medical science has provided us with weapons against some of these microbes in the form of powerful medicines. Our body also has its own defence mechanisms including the skin. It s important to remember that only a very small proportion of all microbes are bad news. Some microbes are used to make food products such as yoghurt and cheese. Other microbes live on and in our bodies and play an important role in keeping us healthy.

In this chapter, students will: 17.1 ◗ distinguish between infectious and

non-infectious diseases 17.2 ◗ learn about bacteria and how to grow

them in the lab 17.3 ◗ describe examples of harmful and

beneficial microbes 17.4 ◗ learn about viruses 17.5 ◗ appreciate the importance of the

discovery of antibiotics as well as some of their advantages and disadvantages 17.6 ◗ describe the structure of the skin and

the important role it plays in keeping us healthy 17.7 ◗ understand how skin cancer forms

and outline some discoveries by Australian scientists to fight skin cancer 17.8 ◗ learn about some careers in the field

of medical science.

Coloured electron micrograph of bacteria that cause gas gangrene

17 Staying healthy thinking about diseases 1. Copy the table below into your workbook. Work with two or three other students to fill in the table for 10 diseases.

2. Study the graph below. It shows the main causes of death worldwide in 2002. Maternal conditions (5 )

Other (5 )

Cardiovascular disease (29 )

Injuries (9 )

Is this an infectious disease?(a)

Name of disease

(a)

Which part of the body does this disease affect?

Infectious diseases are those you can catch from other people. They are caused by microbes or other disease-causing organisms.

2. Some diseases are hereditary; they tend to run in families. List as many examples of hereditary diseases you can think of.

analysing disease data 1. Study the graph below. It shows the main causes of death in Australia in 2005. Disease Coronary heart disease Stroke Chronic obstructive pulmonary disease Depression Lung cancer Dementia Diabetes Colorectal cancer Asthma Osteoarthritis 0

2

4

6

8

10

12

14

Main causes of death in Australia in 2005 Source: Australian Institute of Health & Welfare

(a) What were the three main causes of death in Australia in 2005? (b) Which of the diseases shown in the graph are examples of lifestyle diseases (diseases caused by lifestyle factors such as smoking, lack of exercise and unhealthy eating habits)? (c) Are there any infectious diseases shown in the graph?

Cancer (13 )

Infectious diseases (19 : 45 in low-income African and Asian countries; 63 among children under 5 globally)

Respiratory and digestive conditions (20 )

Main causes of death worldwide in 2002

(a) What percentage of people died from infectious diseases: (i) worldwide (ii) in low-income African and Asian countries? (b) Why do you think there is such a large difference in the percentage of people who died from infectious disease between wealthier countries and poor countries? (c) What percentage of children who died before the age of 5 died of infectious diseases? Why is this figure so high? (Hint: Think about the other main causes of death and who they are likely to affect.) (d) Draw a column graph to represent the data shown in the pie chart above. (e) If the same data was collected for 2012 and a similar graph drawn, how do think the two graphs would differ? Give a reason for your answer.

17.1

Catch us if you can Diseases can be divided according to whether they are infectious or non-infectious, as shown in the cluster map below.

eBook plus

eLesson

Killing Australians Learn about the leading causes of death in Australia. eles-0069

Cystic fibrosis Bovine spongiform encephalopathy (mad cow disease)

Colour blindness Osteoporosis Haemophilia Anaemia

Influenza

Obesity

Measles

Goitre Inherited

AIDS Nutritional Chickenpox

Depression Schizophrenia

Viruses

Mental

Prions

Botulism Tetanus Tuberculosis

Lactose intolerance

Chemical (metabolic)

Non-infectious

Disease

Infectious

Cholera

Bacteria

Diabetes Protozoa

Giardiasis

Drug related Accident related

Malaria

Animals

Environmental

Cancer

Ageing Louse Fungi

Asbestos related

Ringworm

Tapeworm Heart disease

Arthritis Tinea

Liver fluke Thrush Stomach

Breast

Colon

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Infectious diseases are those that can be spread or transferred from one organism to another. The common cold, influenza and chickenpox are examples of infectious diseases. Non-infectious diseases cannot be spread from one person to another. Arthritis and diabetes are examples of non-infectious diseases. You cannot ‘catch’ them from someone else.

Can’t catch us! The seven main types of non-infectious diseases are related to: • nutrition, including overeating, undereating and eating an unbalanced diet • ageing, the gradual breakdown of body tissues • cancer, the multiplication of body cells at an abnormal rate • inherited disorders, which are passed on from your parents’ genes • mental disorders, with a variety of causes including chemical deficiencies, stress and trauma • chemical deficiencies that result in metabolic disorders • environmental diseases resulting from exposure to poisons, asbestos, fire, accidents and drugs.

Activities REMEMBER 1 Distinguish between the causes of infectious and noninfectious diseases. 2 Recall seven types of non-infectious diseases. 3 Classify the following diseases as infectious or noninfectious. ringworm, colon cancer, thrush, arthritis, cholera, diabetes, osteoporosis, malaria, measles, depression, anaemia, AIDS 4 Use the mind map on the previous page to distinguish between the causes of: (a) goitre and arthritis (b) haemophilia and anaemia (c) AIDS and malaria (d) tinea and chickenpox.

THINK AND INVESTIGATE 5 Explain why nutritional diseases are not classified as infectious diseases. 6 Until the middle of the twentieth century, infectious diseases killed many more people than non-infectious

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Catchy diseases Infectious diseases are caused by pathogens (diseasecausing organisms). Some pathogens are large enough to be seen without a microscope. Tapeworms, head lice and liver flukes are examples of pathogens you can see without a microscope. Most pathogens are tiny and cannot be seen without a microscope. Many diseases are caused by single-celled bacteria, protozoa or fungi. Viruses and prions are not big enough to be seen with a light microscope but they can cause serious illness. AIDS is caused by a virus whereas mad cow disease is caused by prions. When you ‘catch’ a disease from another person, the pathogen they are carrying invades your body.

Head lice are pathogens that can be seen without a microscope.

diseases. However, since about 1930, in the developed countries of Australia, North America and Europe, more people have died from non-infectious diseases. Account for this change. 7 The biggest killer of Australians in 2006 was heart disease. Explain how diseases of this kind, such as heart attacks, might be related to nutrition.

INVESTIGATION 8 (a) Investigate the cause, symptoms and methods of prevention for one of the following diseases: osteoporosis, schizophrenia, haemophilia, anaemia, arthritis, heart disease, lung cancer, skin cancer. (b) Report your findings back to your team or class in a PowerPoint presentation, visual thinking tool or poster. (c) In your team, discuss with others any ways in which the community or government may be involved in reducing the impact or frequency of these diseases. 9 Fatal familial insomnia is a disease caused by prions. (a) Investigate the symptoms of this disease. (b) Even though fatal familial insomnia is caused by prions, it is also considered to be a hereditary disease. Find out why.

17.2

Germs everywhere They make you sick, they can cripple you and even kill you. They are more dangerous to human life than sharks, crocodiles, snakes and even other humans. On the other hand, you couldn t live without them. Some of them even live inside your body. They are among the smallest living things on the planet. You know them as bacteria. All organisms that are too small to be seen without a microscope are called microbes. Bacteria are microbes made up of only one cell. There are many different types of bacteria. Some are helpful and some relatively harmless, but some can be fatal to humans. Bacteria live in a variety of places, such as in dirt, in water, inside your large intestines and even underground. Bacteria are among the earliest life forms that appeared on Earth billions of years ago. A typical bacterium is about 1 micron in size (a thousandth of a millimetre). They can be rod-shaped, spherical or spiral-shaped. Bacteria reproduce by binary fission; a single cell divides into two cells. These two cells then grow until they reach a certain size. Each of them then divides into two to produce four cells. These four cells in turn divide to produce eight cells. If the bacteria are in ideal conditions, this process can occur quite rapidly. In fact, if a single bacterium is kept in a moist environment, provided with a supply of nutrients and kept at the right temperature, it can give rise to a colony of bacteria that is so large it can be seen without a microscope in just 24 hours.

Colonies of bacteria can be seen on the agar. Colonies contain thousands of bacteria. Each colony is formed from one bacterium by binary fission.

Bacteria reproduce by binary fission.

Microbiologists are scientists who study microbes. They can find out a lot about bacteria by growing them on agar, which is a jelly-like substance. (Some people eat agar as a dessert.) The agar is poured into a shallow dish called a Petri dish and allowed to set. Substances such as vegemite can be added to the agar to help bacteria grow. When microbiologists grow bacteria that live in blood, they use blood agar, which is a mixture of blood and agar that sets like jelly. To grow colonies of bacteria, a very small amount is wiped onto the surface of the agar; at this stage, they cannot be seen. The agar plate is then incubated; that is, it is left in a cabinet that maintains the optimum temperature for bacterial growth. The bacteria divide over and over by binary fission. After one or two days, the agar plates are removed from the incubator.

Colonies of bacteria on an agar plate

it is possible to grow bacteria on gelatine (the substance that makes jelly set). gelatine is not as suitable as agar though because it melts in hot weather and some bacteria can digest gelatine and turn it into liquid. these are the problems that the microbiologist Walther Hesse faced until he asked his wife how she managed to make jellies that did not melt in hot weather. Lina Hesse s secret recipe was agar. She had got the idea of using agar in her jellies from a neighbour who had emigrated from Java. Walther Hesse switched from using gelatine to agar with great success. this technique was then adopted by robert Koch, a famous microbiologist Hesse was working with, and today agar is one of the most common substances used to grow bacteria.

17 Staying healthy

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◗ Pour the sample of water over the surface of the

INVESTIGATION 17.1

agar and swish it around. Seal and label the agar as before.

Where are those germs? You will need: sterile cotton buds nutrient agar plates in Petri dishes (3 per group) sticky tape marker pen sterile Pasteur pipette CAUTION Agar plates should not be opened after incubation. ◗ Swipe a sterile cotton bud across a surface of your

choice (such as canteen counter, computer keyboard, phone mouthpiece or bin lid).

◗ Incubate the three plates upside down at 30 C for

48 hours. Remove the plates from the incubator and observe the colonies of bacteria through the lid of the Petri dishes (do not open the Petri dishes).

diScuSSioN 1

Draw a diagram of each Petri dish showing the location and size of the colonies.

2

Colonies of bacteria tend to be smooth whereas colonies of fungus appear furry and are often larger. Do you have colonies of bacteria or fungi or both on your plates?

3

Look at the other groups plates. (a) Which of the surfaces tested by your class had the most microbes? How can you tell? (b) Which body part tested had the most microbes? (c) Which of the water samples tested contained the most microbes?

4

Explain why it would be dangerous to unseal the agar plates and lift the lid to look at the colonies of microbes.

5

Find out from your teacher how the plates are disposed of safely at your school.

6

Design an experiment to test whether antibacterial surface spray really does kill bacteria.

◗ Swipe the cotton bud across the surface of the agar. Be

careful not to push down too hard. The cotton bud should not leave a mark on the agar. ◗ Use sticky tape to seal the plate around the edge. ◗ Use a marker pen to write your group s name and where

you collected the sample from. ◗ Use a different cotton bud to swipe a part of your body

(such as the inside of your nose, your teeth, inside your ear or your scalp). ◗ Swipe the cotton bud on the surface of the second agar

plate, then seal and label it as before. ◗ Use the sterile Pasteur pipette to collect about 1 mL water

from a location of your choice (such as a fish tank, puddle, local creek, school swimming pool or drain pipe).

Activities reMeMber 1 define the term microbe .

Generation

Time (min)

Number of cells

1

0

1

2 List the three shapes that bacteria can have.

2

40

2

3 outline how bacteria reproduce.

3

80

4

4 recall what bacteria need to grow and reproduce.

4

120

8

5

160

6

200

5 What is agar? explain why it is an ideal substance to grow bacteria on.

tHiNK aNd aNaLYSe 6 Escherichia coli is a species of bacteria. Under ideal conditions, the generation time for E. coli is 40 minutes. That means that every 40 minutes the E. coli cells divide to produce two cells.

450

(a) Copy and complete the table below.

Core Science | Stage 4 Complete course

7 8 9 10 (b) construct a graph showing how the number of cells changes over time. Time should be on the

horizontal axis and the number of cells on the vertical axis. (c) describe the shape of the graph. (d) deduce how long it would take for a colony of E. coli to reach over 2000 cells. 7 When microbiologists prepare agar to grow bacteria, they boil the agar mixture for a few minutes to ensure that the agar is sterile (free of microbes). explain why it is important for the agar to be sterile.

iNveStigate 8 Robert Koch made some important contributions to microbiology. Research and summarise some of Koch s discoveries in an information report. work sheet

17.1 Classifying bacteria

17.3

The good, the bad and the ugly Single-celled organisms such as bacteria and some fungi can make you seriously ill, make your teeth rot and cause food to decay. Not all micro-organisms are bad news though. Some microbes are used to make food, and others play an important role in keeping us healthy. Microbes are also involved in the recycling of nutrients in ecosystems.

the bad guys Bacteria and other micro-organisms are responsible for many diseases. Some diseases caused by bacteria include tetanus, pneumonia, meningococcal meningitis, tooth decay and some cases of sore throat and ear infections. Bacteria in food and water can cause food poisoning and gastroenteritis. Even pimples are caused by bacteria.

they feed on the nutrients in the food. Storing food in the fridge slows down its decay as the low temperature slows down the growth of bacteria. Another way to keep food from rotting is to dry or freeze it. If there is little water available, or the water is frozen, bacteria cannot reproduce and the food will not decay. Microbes in food can also be killed by high temperatures or radiation. Canned food and long-life milk have a long shelf life because the microbes in these foods have been killed by heat.

Bacteria and fungi are responsible for the decay of food.

the good guys The rash on this patient s legs is caused by the bacteria responsible for meningococcal meningitis.

Bacteria can also cause disease in other animals and in plants. Anthrax and mastitis are bacterial diseases of cattle. Leaf blight and spot, found in plants, are bacterial diseases. Micro-organisms are responsible for the decay of food. The microbes break down the food as

Microbes are involved in the preparation of a range of foods. Yeast (a fungus) is used to make bread and most alcoholic drinks including wine and beer. Yeast converts glucose (a type of sugar) into alcohol and carbon dioxide gas. This is known as fermentation. Without yeast, wine and beer would not contain alcohol. In bread, the alcohol formed by the yeast evaporates as the bread is cooked. The carbon

dioxide bubbles that form in the fermentation process are important though. They are the reason that bread dough rises, and they make bread light and fluffy. Many dairy products including yoghurt, cheese, butter and sour cream are made using bacteria. To produce yoghurt, the bacterial species Streptococcus salivarius and Lactobacillus delbbrueckii are added to milk. The bacteria multiply and produce lactic acid as a waste product. The lactic acid causes a protein in the milk to clump, so the milk solidifies. Sometimes, other species of bacteria, including Lactobacillus acidophilus, Lactobacillus casei and Bifidobacterium are added to the yoghurt to increase its health benefits and improve the taste. Even coffee and chocolate could not be made without bacteria. The tough outer coat of coffee and cocoa beans is broken down by bacteria and fungi as part of the process of making coffee and chocolate. Also, without the action of bacteria, olives would be inedible, pickles would be plain cucumbers and sauerkraut would simply be cabbage.

in the future, the dentist s drill might be replaced by a spray of bacteria or a vaccine. tooth decay is caused by a bacterium called Streptococcus mutans. a vaccine against this bacterium would greatly reduce the incidence of tooth decay. certain bacteria can prevent the growth of S. mutans. Mouthwashes or sprays that contain good bacteria may one day be used to control tooth decay.

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Many of the microbes that live on or in our bodies help to keep us healthy. The bacteria that grow on our skin produce acid and make our skin slightly acidic. This prevents the growth of diseasecausing bacteria. Bacteria in our intestine help to break down some of the complex carbohydrates in the food we eat and produce important vitamins. Exposure to certain bacteria may also help strengthen the immune system that fights disease. For this reason, some people regularly eat food that contains the right type of bacteria, such as yoghurt with a live bacterial culture.

INVESTIGATION 17.2 preserving apples You will need: small apple cubes (peeled) test tubes range of substances to test (such as water, ethanol, sugar solutions of different concentrations, vinegar, salt solutions of different concentrations) ◗ Pour a sample of each of

the solutions you are testing into a separate test tube. For example, you could put water in test tube 1, ethanol in test tube 2 etc. ◗ Place one apple cube in each

test tube. ◗ Set up one additional test

tube containing only an apple cube.

Bacteria and fungi in soil break down dead animal and plant material to provide the nutrients that plants need to grow.

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Activities reMeMber 1 identify some diseases caused by bacteria. 2 identify the bacteria that cause tooth decay. 3 Name five foods that are produced using bacteria.

diScuSSioN

tHiNK

1

Write an aim for this experiment.

2

Design a table to record your observations for each apple cube in each lesson for the next two weeks.

4 explain why plants and animals would eventually die if all bacteria were suddenly killed.

Some yoghurts contain live bacteria.

Bacteria and fungi are also important in the cycling of nutrients in ecosystems. They decompose (break down) dead animals and plants as well as the urine and faeces produced by animals, and return the chemicals to the soil and air. Without microbes, the soil would be depleted of nutrients, and plants would soon cease growing.

people who are obese have a different mix of bacteria in their gut from thin people. it is not known whether the type of diet that leads to obesity also promotes the growth of one type of bacteria in the gut over another or whether the bacteria affect the amount of energy a person can absorb from the food they eat. bacteria make up about 30 per cent of the weight of faeces.

3

Each lesson, record any changes to the pieces of apple. Take note of the colour, the presence of mould and any other signs of decay.

4

Which substance best preserved the apple pieces (stopped them from decaying)?

5

Why do you think certain substances can preserve food?

6

Which test tube was the control?

7

List some examples of foods that are preserved using: (a) salt (b) sugar (c) alcohol (d) vinegar.

5 explain why it is important to wash your hands after using the toilet and before eating. 6 Design an experiment to investigate which conditions cause bread to go mouldy fastest.

iNveStigate 7 Long-life milk lasts for months at room temperature until it is opened. Find out the process involved in making milk long life . Does the process affect the nutritional value of the milk? 8 Research a bacterial disease. Summarise your findings in a report with the headings Cause , Symptoms and Treatment . 9 Find out what probiotics are and why some people add probiotics to their diet. work sheet

17.2 The good and the bad

17.4

Viruses

living or not?

Viruses are able to infect us and take over our cell machinery to make more of themselves. Except by their effects on our bodies, we cannot detect their presence without advanced technology.

using others for their needs

cell-less Viruses do not have cells like animals, plants, fungi and bacteria. They do not have a nucleus, membrane or cytoplasm. They do, however, contain substances found only in living cells. Viruses consist of a protein box, containing a tiny strand of a substance found in the cell nucleus of living cells. This substance is called nucleic acid. The nucleic acid holds the instructions for making new viruses. Some of the shapes of viruses are shown below. Tobacco mosaic virus

Influenza virus

When they are inside living cells, viruses act as if they are alive. When they are outside living cells, they do not display the characteristics of living things. They can be isolated and crystallised in a similar way to chemical compounds. Some scientists classify viruses as nonliving because they cannot function independently. A virus may lie dormant for many years. Then, when it comes in contact with a suitable living cell, it invades the cell and forces it to make hundreds of new virus particles. When the cell dies, it bursts open and releases the new particles, which may then infect other cells. Bacteriophage

Cold sore virus

The viruses that cause influenza (the flu) and the common cold leave the bodies of infected people in droplets of mucus. The shiny spray that flies out with a sneeze is packed with virus particles that you may inhale. These droplets may be transferred to a tissue or the hands of the person with the virus, or to a door handle or a lift button. If you touch your eyes, nose or mouth before washing your hands, you can transfer the virus to a mucous membrane where it can invade your cells and multiply. Some types of virus can live outside the body for a surprisingly long time, which explains how people can catch a virus without a face-to-face meeting with a sick person.

curing a viral illness

350 nm

100 nm

aaaachoooooo!

100 nm

150 nm

Polio virus

Adenovirus

12 nm

25 nm

Foot-and-mouth virus

10 nm

Shapes of some common viruses. Did you know that a nanometre (nm) is equal to a millionth of a millimetre?

These viruses destroy the leaves of tobacco plants.

The red objects are the viruses that cause AIDS.

Antibiotics kill bacteria, but they do not kill viruses. Many antibiotics work by disrupting the cell walls of the bacteria. Viruses don t even have a cell wall. So, antibiotics will not cure the common cold or the flu because they are caused by viruses. The job of ridding your body of the cold and flu viruses is left to your body s own immune system. The best defences against viruses are to keep your hands clean, avoid touching your eyes or picking your nose, and maintain a healthy immune system by eating healthily, keeping a positive frame of mind and getting enough sleep.

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the SarS virus The SARS virus is a very nasty flu-like virus, that hit the headlines in 2003. It causes fever, headache and difficulty in breathing. SARS stands for severe acute respiratory syndrome. The first victim of the virus was a 48-year-old businessman who had travelled from the Guangdong Province in China, through Hong Kong, to Vietnam. The businessman died of the disease and so did the doctor, Dr Carlo Urbani, who diagnosed the virus as a new one. The virus spread rapidly and, within weeks, had infected thousands of people around the world. To try to reduce the spread of the virus, schools were closed throughout Hong Kong and Singapore.

people. Fortunately, people with SARS showed flu-like symptoms very early on, which made it easy to spot victims, treat them and isolate them. If a virus takes a long time to produce symptoms, it is more difficult to prevent the virus from spreading.

Activities reMeMber 1 define the term nucleic acid . Where is nucleic acid found? 2 outline how viruses are similar to non-living chemical compounds. 3 outline how viruses are similar to living cells. 4 describe how the flu virus is passed from one person to another. 5 recall whether antibiotics are effective against viruses. 6 What does SARS stand for?

tHiNK aNd reaSoN 7 explain the statement Viruses cannot function independently . 8 (a) Use the information on the previous page to construct a column graph that shows the names of the different types of virus on the vertical axis and their size on the horizontal axis. (b) identify the virus that is: (i) the biggest (ii) the smallest. (c) classify the viruses into groups on the basis of: (i) their size (ii) their shape. (d) construct a classification key (see pages 89 91) for the viruses shown on the previous page. Artist s impression of the SARS virus (with the red spikes) invading a host cell, so that it can replicate itself

At the same time, scientists around the world worked frantically to find out how the virus was spreading. Chinese scientists did experiments that showed the virus could live for five days outside the body in a drop of saliva. Another study showed the virus survived a stint of more than 24 hours on a plastic surface. German scientists found that household cleaners did not kill the virus, which meant that disinfecting hospitals with everyday cleaning fluids would not stop the virus spreading. In the end, the spread of the virus was stopped by isolating the people who had caught it and preventing them from having contact with other

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9 explain why washing your hands frequently can reduce the risk of catching diseases such as the flu. 10 explain why it is more difficult to control the spread of viruses that take a long time to produce symptoms.

iNveStigate 11 Find out more about some of the diseases that viruses cause. Summarise your information in a poster. 12 Find out about the special measures that were taken at airports to control the spread of SARS at the height of the epidemic. 13 What is bird flu? Can it be transmitted to humans? work sheet

17.3 Viruses

17.5

preScribed focuS area applications and uses of science

A weapon against germs One hundred years ago, many children died both from infectious diseases and bacterial infections. A small scratch was sometimes enough to allow deadly bacteria to enter the body and cause swelling, the formation of pus and severe pain. Children born today can avoid the harsh consequences of many bacterial infections.

Today, we take antibiotics to avoid the harsh consequences of bacterial infections. These photographs of a young patient in 1942 show how serious an infection can be. After being treated with penicillin, the patient s condition improved and she recovered fully.

an accidental discovery The first antibiotic to be used successfully to treat a patient was penicillin. Alexander Fleming discovered the antibacterial

properties of penicillin by accident. He had been growing bacteria on agar plates, and when he went on holidays he forgot that he had left some open agar plates on a bench near a window sill. When Fleming came back from his holiday, he noticed that mould was growing on some of the plates. No bacteria had grown around the mould but the rest of the plates were covered with bacteria. He concluded that the mould must be producing a substance that prevents the growth of bacteria. He called the substance penicillin, but he was not able to extract it, so it could not yet be used to treat bacterial infections.

he was knighted in 1944. His likeness appeared on an Australian $50 banknote and a suburb of Canberra was named after him.

Howard Florey

the australian connection

Scientists working in teams

It was a team of scientists, led by an Australian named Howard Florey, that discovered how to extract penicillin. Howard Florey was born in Adelaide in South Australia in 1898. He was a keen student who loved sport and chemistry. He studied medicine at the University of Adelaide where he won a Rhodes scholarship to Oxford University, England. While in England he led the team that finally extracted penicillin in 1940. In 1945 he shared his Nobel Prize with Alexander Fleming and Ernst Chain. In speaking of his discovery, he modestly stated, All we did was to do some experiments and have the luck to hit on a substance with astonishing properties. Penicillin was so successful in saving lives that population control became an issue for medical researchers. Florey later worked on contraception research. In honour of his contribution to medicine,

In the 1940s, it was unusual for scientists to work in teams. Yet Howard Florey gathered together a group of experts and divided the problem up so each one worked in an area that best suited their talents. The researchers and their responsibilities were as follows: • Ernst Chain shared the Nobel prize for the discovery of penicillin. Chain found Fleming s notes and brought them to the attention of the team. He worked with Edward Abrahams looking for ways to purify penicillin. • Norman Heatley used ether and bedpans to develop ways to extract penicillin. • AD Gardner and Jena Orr-Ewing worked together to see how organisms reacted to penicillin. • Margaret Jennings worked with Florey to conduct animal trials of the substance. Their most important test was conducted

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on Saturday 24 May 1940. They gave eight mice a lethal dose of streptococcus bacteria. They then gave four mice penicillin. Within 24 hours these four had recovered while the four control mice were dead. They knew they had something worth telling the world about. • Ethel Florey worked with her husband on the clinical trials of penicillin. Albert Alexander was the first human to be treated with penicillin. He had been scratched by a rose thorn, and his face was so terribly swollen with a bacterial infection that his only remaining eye had to be lanced. He was given penicillin and started to recover, but unfortunately not enough penicillin was available to control his horrendous infection and he died. Florey s team then worked hard to make large quantities of penicillin. The war in Europe meant there was little financial support for their work. However, Fleming went to America and got assistance to begin mass production of the drug, and it was used to treat wounded soldiers in the last months of World War II.

456

There are some problems with penicillin: a small percentage of the population is allergic to penicillin; and an increasing number of bacteria have developed resistance to penicillin. When penicillin was first discovered, it was effective against many bacterial species. It is now common for a patient to show no improvement after taking penicillin to treat a bacterial infection. New antibiotics such as streptomycin and sulfur drugs have been developed, but bacteria are rapidly developing resistance to these too. The antibiotic vancomycin is currently the last resort. It is used to treat only bacterial infections that have shown no improvement with all other antibiotics. Unfortunately, some bacteria are developing resistance to vancomycin so it is important for scientists to continue the search for new antibiotics. Antibiotics kill or prevent the growth of disease-causing bacteria. However, they also affect friendly

Activities reMeMber

Miracle cure-all?

1 define the term antibiotics .

Initially penicillin had to be injected in the bloodstream, as natural penicillin is destroyed by stomach acid. Today, it is possible to treat many infections by taking syrup or tablets containing chemicals derived from penicillin. These chemicals are not broken down by stomach acid. Once the penicillin reaches the bloodstream, it works by stopping bacteria from forming cell walls as they try to divide. This is why penicillin is useful for treating bacterial infections only; it is powerless against viruses. A case of the flu or chickenpox, both viral infections, cannot be cured with antibiotics.

2 recall what produces penicillin.

Core Science | Stage 4 Complete course

3 recall who discovered penicillin. 4 outline the role that Howard Florey played in the development of penicillin as a drug. 5 explain how penicillin works.

tHiNK 6 describe what would have happened if you had an ear infection before antibiotics were invented. 7 Why are antibiotics prescriptiononly medicines? (Prescription medicines can be purchased only from a chemist if you have a written prescription for that particular medicine from a doctor.) discuss

a

b

c

d

In these photographs, bacteria were grown in penicillin for 30 minutes. The bacteria grow longer as shown at (b), but eventually rupture (d), unable to divide due to the influence of the penicillin.

bacteria, such as the bacteria found in your intestines. That is why taking antibiotics sometimes causes problems including diarrhoea and stomach aches. Eating yogurt or other food containing friendly bacteria can help reduce the side effects of antibiotics.

whether antibiotics should be available without a prescription. 8 What precautions must we all take to ensure that antibiotics remain useful to us? 9 assess whether Florey would have been successful in extracting penicillin if he had been working on his own rather than as part of a team. What are the advantages and disadvantages of working in a team?

iNveStigate 10 Meningococcal meningitis is a bacterial infection. investigate why people can die from this disease despite antibiotics being readily available in hospitals. 11 Use the internet to find out more about Nobel prize winners. work sheet

17.4 Penicillin

17.6

Skin deep Your skin plays an important role in keeping you healthy. As well as holding the insides of your body in, it also: • protects your body from microbes that could cause disease • is almost completely waterproof • protects the inside of your body from chemicals and harmful radiation from the sun • detects heat, cold, pain, pressure and movement • helps control your body temperature • forms vitamin D in sunlight • releases water and other waste products. Your skin varies in thickness between about 0.5 millimetres and 5 millimetres. The thickest part is on the soles of your feet. Skin consists of three layers.

Layer of dead skin

Sebaceous gland

Hair Pore Epidermis

Pain receptor Light-contact receptor Heat receptor

Dermis

Sweat gland

Cold receptor Pressure receptor

Fatty layer

Movement receptor

Nerve

When you get hot, it is important that your body cools itself down so the blood remains at its constant temperature of about 37 C. Your sweat glands produce a liquid that is released through the pores at the surface of your skin. When the water in your sweat evaporates, it takes some of the heat out of your body.

are you ticklish? Are you more ticklish on some parts of your skin than others? Below the surface of your skin there are many receptors, which are attached to nerves. The nerves send messages to the brain. There are different receptors for heat, cold, light contact, pain, pressure and movement. They are all receptors to the sense of touch. The light-contact receptors are nearer to the surface and closer together in some parts of your skin than others. It is those parts that are most sensitive to tickling. Some parts of the skin are also more sensitive to pain, heat, cold, pressure and movement than others. Your sensitivity depends a lot on how close together the receptors are to each other and how deep they are.

Blood vessels

The skin is divided into three layers.

The epidermis is the top layer. It contains several layers of cells. At the very top is a layer of dead skin cells, which flake off continually. At the bottom of the epidermis, new cells are always being produced. They push upwards on the older cells, moving them towards the surface. Below the epidermis is the dermis, which contains receptors for the sense of touch. It also contains sweat glands and many small blood vessels. Beneath the dermis is a thicker layer of fatty tissue, which acts as an insulator to help keep the body temperature constant. This fat has been stored by the body and can be used when needed to provide extra energy.

Sweat doesn t actually smell until it is consumed by the bacteria that live on the surface of your skin. the regions around your armpits and external sex organs are warm and moist, providing ideal conditions for bacteria to grow and feed on the sweat. this is why these areas can get smelly.

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Activities

INVESTIGATION 17.3 Where is the skin most sensitive to light contact?

reMeMber

You will need: 2 toothpicks ruler 2 rubber bands blindfold

1 recall the six different types of touch receptors. 2 The skin is an important organ because it contains the receptors for the sense of touch. outline other reasons why your skin is important to you. 3 distinguish between the epidermis and the dermis.

Can you feel one point or two?

◗ Draw a table like the one below in your workbook. ◗ Use rubber bands to attach two toothpicks to a ruler so that they are 2 cm

apart. ◗ Blindfold your partner. Gently touch your partner s inside forearm with the

points of the two toothpicks. ◗ Ask your partner whether two points were felt. Move one toothpick towards

the other in small steps until your partner is unable to feel both points. To make sure that there is no guesswork, use just one point from time to time. ◗ Record the distance between the toothpicks when your partner can feel

only one point when there are really two points in contact. ◗ Repeat this procedure on the palm of one hand, a calf (back of lower leg),

a finger and the back of the neck. ◗ Swap roles with your partner and repeat the experiment.

Where is your skin most sensitive? Distance (cm) between two points when only one point is felt Part of the skin

Your partner

You

4 explain how sweat cools you down when your body gets hot. 5 Summarise your answers to questions 1 4 in a concept map.

tHiNK 6 deduce why the thickest part of your skin is on the soles of your feet. 7 explain why some parts of your skin, such as the back of your hand, are more sensitive to heat than others. 8 How do the movement receptors receive a sensation of movement when they are well below the surface of the skin?

Inside forearm Palm of hand

iNveStigate

Calf

9 With a partner, play a guessing game to see how well you can use your sense of touch alone to identify 10 unknown objects. You will need a blindfold and 10 objects of about the same size. Sandpaper, plastic, coins and pieces of carpet, polystyrene, nylon and wool would be ideal. See who can identify the most objects correctly.

Finger Back of neck

diScuSSioN

458

1

Which touch receptors were being used in this experiment?

2

Which area of the skin was most sensitive?

3

Which area of the skin was least sensitive?

4

Suggest why the skin is not equally sensitive all over the body.

5

Which parts of the skin are likely to have the most light-contact receptors?

6

Suggest further experiments to investigate light-contact receptors more closely.

Core Science | Stage 4 Complete course

17.7

Skin cancer Skin cancer is the most common form of cancer in Australia. In fact, two out of three Australians are likely to get skin cancer at some time during their lives. The most serious forms of skin cancer are responsible for about 1000 deaths each year in Australia.

What causes skin cancer? The main cause of skin cancer is exposure to the sun. The ultraviolet radiation reaching Earth from the sun is not visible. Ultraviolet radiation, which is also the cause of sunburn, is at its peak in the middle of the day when the sun is directly overhead. Ultraviolet radiation causes cancer in the cells of the epidermis, the top layer of the skin, because it damages the cells genetic material, called DNA.

prevention is better than cure To avoid getting skin cancer, follow the following simple steps: 1. Avoid going out in the sun in the middle of the day (11 am 3 pm), particularly in summer. 2. Wear a shirt with sleeves and a hat when outside. 3. Wear a broad spectrum sunscreen labelled 30+ or higher.

The three main types of skin cancer Squamous cell carcinoma

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• less common and more dangerous than basal cell carcinoma

• appears as a red, scaly sore • usually found on the hands,

forearms, face and neck, but can spread to other parts of the body • mostly affects people over 40 who have been exposed to the sun for many years • kills about 200 Australians each year Basal cell carcinoma

• most common form of skin cancer and also the least dangerous

• appears as a red, flaky lump on the skin

• rarely spreads to other parts of the

body but needs to be treated before it grows large or forms a deep sore

Melanoma

• As the body’s cells die, new cells are made to replace them. in a healthy person, just the right number of new cells are formed using a process called cell division. if cells become damaged, they can multiply out of control. cells keep dividing over and over until a mass of cells called a tumour is formed. the cells in a tumour are not specialised. they cannot do the job of the cells they are replacing. for example, brain cancer cells cannot work like normal brain cells. Some tumours are malignant. that means they can spread to other parts of the body. • An Australian drug company called peplin has developed a gel made from a common weed called Euphorbia peplus, which has been used successfully to treat some skin cancers. the plant contains a cancer-fighting chemical. peplin has found a way of extracting this chemical from the plant and making it into a gel that can be applied to skin cancers. When the gel was tested, it cleared most skin lesions after just two days.

early detection The key to curing skin cancer is early detection. Even melanomas can be cured in more than 95 per cent of patients if they are detected quickly. If you see a new lump or spot, or a changing freckle or mole, see a doctor promptly.

• least common but most dangerous form of skin cancer • first sign is a change in size, shape or colour of a freckle or mole, or the appearance of a new spot on normal skin

• can spread quickly to other parts of the body • most common in adults aged between 30 and 50 years, usually caused by long

periods of exposure to the sun during childhood and adolescence about 800 each year in Australia

• cause of the most deaths from skin cancer

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Some questions about fun in the sun Q: Is a suntan healthy? A: No. A suntan is evidence that you have been exposed to the sun for too long. A suntan will not protect you from skin cancer. Fake suntan lotions do not offer protection from skin cancer either.

Q: Do I need to worry about sunburn or skin cancer when it s cloudy? A: Yes. Although clouds block out a lot of the sun s visible light, they do not block out enough ultraviolet radiation to protect your skin completely, especially during summer. The graphs below show that light cloud cover has little effect on the harmful ultraviolet radiation reaching the ground on a summer s day in Sydney. Heavy cloud, however, decreases the amount of ultraviolet radiation reaching the ground by over 90 per cent.

Q: Do I need to use sunscreen when I wear a hat? A: Yes. The sun s radiation is reflected from the ground and from water. Snow and sand reflect a lot of radiation, even on cloudy days. In addition, many hats, including baseball hats, do not protect you from direct radiation. Widebrimmed hats or legionnaire hats provide the best protection because they shade the neck and ears.

Q: What does SPF 30+ mean? A: SPF stands for sun protection factor. It allows you to estimate how long you can stay in the sun before your skin starts to go red. This period can be estimated by multiplying the amount of time that it takes your skin to redden by the SPF factor. For example, if your unprotected skin starts to burn after 10 minutes in

the hot sun, proper use of SPF 4 sunscreen would allow you to remain in the sun for 10 × 4 = 40 minutes before burning starts. After that 40 minutes, you would burn, even with more sunscreen applied. An SPF water-resistant 30+ sunscreen reapplied every 2 hours would allow you to remain in the sun for at least 10 × 30 = 300 minutes before burning starts. SPF 30+ sunscreen blocks out about 97 per cent of the sun s radiation.

Q: What does broad spectrum mean? A: The Cancer Council NSW recommends a broad spectrum SPF 30+ sunscreen. Broad spectrum sunscreens offer protection from the three different types of ultraviolet radiation: UVA, UVB and UVC.

ltraviolet radiation throughout the day

Extreme

Very high

Heavy cloud

High

Light cloud

Moderate 9.00 am

11.00 am

1.00 pm

Cloud-free day

3.00 pm

5.00 pm

9.00 am

11.00 am

1.00 pm

3.00 pm

Cloudy day

These graphs show how the ultraviolet radiation reaching the ground changes on a typical summer day in Sydney.

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5.00 pm

Activities reMeMber 1 identify the most serious form of skin cancer and outline how it is caused. 2 distinguish between a benign tumour and a malignant tumour. 3 recall which part of the sun s radiation is the major cause of skin cancer and sunburn. 4 identify the most dangerous time of day to be out in the sun. 5 outline what you should look for on the skin when checking for signs of skin cancer. 6 outline five ways that you can help protect yourself from skin cancer.

iNveStigate aNd deSigN

(b) Which age groups of females are mostly affected by melanoma? (c) Does melanoma appear to be more common in males or in females over the age of 50? Why do you think this is the case?

13 Design and carry out a survey (consisting of a series of questions) to investigate whether people of different age groups protect themselves from the danger of skin cancer by wearing hats, shirts and sunscreens. By sharing your data with other members of your class, you may be able to form a sound conclusion.

create aNd deSigN 11 Design a colourful poster that would encourage people to protect themselves from the sun s harmful radiation.

work sheet

17.5 Skin

12 Design and construct a multipurpose hat that shades the head and has at least one other purpose. Give your multipurpose hat a name. Prepare an advertising brochure and instruction manual for your hat.

tHiNK 7 Melanomas occur mostly in adults over the age of 30. explain why it is so important that young children and adolescents are aware of the dangers of the sun s radiation.

Age ) y ( ears

Age distribution of melanoma in New South Wales 2003 to 2005

85 + 80 84

8 Daniel has very pale, sensitive skin that begins to burn after only eight minutes in the summer sun. He goes to the beach and takes a tube of SPF 6 sunscreen with him. (a) If he doesn t go swimming, calculate how long he would be able to sit in the sun before getting burned, assuming that he applies his sunscreen correctly. (b) If he used SPF 15+ sunscreen instead, would he be safe sitting in the sun all day? Justify your answer.

75 79 70 74 65 69 60 64 55 59 50 54 45 49 40 44 35 39 30 34 25 29 20 24

9 Kimberley is planning to play a game of tennis with a friend on a warm summer s day. What should she take with her to protect her skin from the sun?

15 19 10 14

tHiNK aNd reaSoN

5 9 0 4

10 extract the answers to the following questions from the graphs at right. (a) Which age groups of males are most affected by melanoma?

15

0 0

10 5 ales e of m g a t n e Perc

5 10

15

es emal e of f g a t n e Perc

Source: NSW Central Cancer Registry

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17.8

preScribed focuS area current issues, research and development

Healthy careers Most of us are familiar with a small number of careers in health and medicine, including nursing, pharmacy, dentistry and general medicine. However, a staff list for a hospital or medical research centre would show you that there are many more careers dedicated to getting people back to health. Numerous scientists work in the field of medicine and play an important role in identifying the causes of diseases and developing and testing treatments.

Scientists playing detective Medical pathologists are scientists who study disease. They do tests to determine the cause of a disease. If you go to a doctor s surgery or hospital and have a sample of blood taken, a pathologist will organise technicians to run tests on the blood sample and prepare a report on the results of the tests. Pathologists also test tissue samples. If you had a mole removed, a pathologist would determine if the mole was harmless or a type of skin cancer likely to spread to other parts of your body. During surgery, a surgeon often sends body tissue to pathology. The results of pathology tests help the surgeon decide whether to finish the operation or keep looking for other things that might be wrong with the patient. Some pathologists do post-mortem examinations ( postmortem means after death ). A post-mortem examination is done if the cause of a person s death is unclear. The pathologist examines and tests the organs to determine the cause of death. Forensic pathologists are called in when foul play is suspected. They collect evidence that may lead to the conviction of criminals. In reality, only a small proportion of post-mortem examinations are concerned with solving crimes.

Medical scientists Many scientists carry out research in the field of medicine. Some are employed by drug companies to develop and test new drugs to treat diseases. Others work for government agencies and universities on particular diseases. Teams of Australian scientists are currently trying to find cures for certain types of cancers and developing new vaccines.

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Australian contributions to medical science A team of scientists led by Howard Florey discovered how penicillin could be extracted, purified and produced (see pages 455 6) and, recently, and an Australian company has developed a treatment for some skin cancers (see page 459). Some other contributions to medical science by Australian scientists are summarised below. • Aspro, the fizzy headache tablets, were invented by the Australian Chemist George Nicholas. Aspirin itself had been developed earlier by the German company Bayer, but it was Nicholas who first produced the convenient Aspro tablets in Melbourne between 1915 and 1917. By the 1940s, it had become the world s leading headache treatment. An Australian scientist developed Aspro tablets.

• Dr Fiona Wood pioneered the development of spray-on skin to treat burns patients, including victims of the Bali bombing in 2002. She started a company that makes the spray-on skin using the patient s own skin cells. It can be applied to burnt areas of the body or to scars. It is also used in cosmetic surgery. The main advantage of spray-on skin is that it reduces scarring. She was named Australian of the Year in 2005. • Before the 1990s, it was widely believed that painful stomach ulcers were caused by stress. In 1982, Barry Marshall and Robin Warren showed that bacteria called Helicobacter pylori cause stomach ulcers and that it was possible to treat ulcers successfully with antibiotics. To prove that these bacteria cause ulcers, Barry Marshall swallowed the bacteria and soon developed symptoms associated with the formation of a stomach ulcer. Both scientists were awarded a Nobel prize in 2005 for their discovery. Robin Warren and Barry Marshall were awarded a Nobel prize for their work on the cause and treatment of stomach ulcers.

• The world s first vaccine against cervical cancer is also an Australian invention. It was developed by Professor Ian Frazer in the 1990s and was first approved for use in countries including the USA and Australia in 2006. The vaccine protects against a virus that is the cause of many cases of cervical cancers.

Activities

CAREER PROFILES

REMEMbER 1 Describe the work of a medical pathologist. 2 Explain why post-mortem examinations are sometimes done by pathologists. Name: Arianne Lee Job title: Clinical trials assistant Field of science: Medical clinical research

First interest in science Arianne s interest in science was first sparked in grade four, after learning about famous scientists from the past. She has always been fascinated by how relevant science is to everyday life. Some time ago, Arianne was a patient in clinical trials for asthma medication and has since taken an interest in the health sciences. Her father s work in the pharmaceutical industry has also given her an interest in this field of science.

The job Arianne is a link between a research company that tests pacemakers and the hospitals that run the tests. She decides who will test the pacemakers and in which hospitals. Arianne seeks permission from ethics committees before any tests are conducted. These committees decide whether the tests are appropriate and also make sure that proper procedures will be followed. After collecting data from the clinical tests, she reports on the results.

Study Arianne has a Bachelor of Science. Her major areas are physiology and pharmacology. These areas are related to human biology and chemistry.

Name: Paula Fisher Job title: Laboratory scientist Field of science: Histology

Paula Fisher is a histologist. Histology is the study of the cells and tissues that make up animals, including humans. Histologists look at small samples of cells and tissues under microscopes.

The job Cancer is a condition where cells grow abnormally. Each year, many people are diagnosed with cancer. Experts agree that the earlier treatment starts, the better the chances of survival. Paula and her team help engineers to design machines. Their machines make diagnosing cancer a much faster process. Paula s job requires her to run the machines and make sure that the cells are clear and easy to see. This makes diagnosing cancer more accurate as well as faster.

Study Paula enjoyed biology and chemistry at high school. She studied Applied Science at university and followed this up with a Graduate Diploma in Medical Laboratory Science. Many universities require students wanting to get into this field to have studied chemistry and one other science, usually physics or biology.

3 What medical trials did Arianne participate in herself?

THINK 4 Which sciences would you need to study in senior school to become a histologist? 5 Identify what the two professions described on this page have in common. 6 In groups of two or three, make a list of the skills and other qualities people in the health sciences need. 7 Working with two or three other students, make a list of at least 20 careers that relate to health. For each career, explain in one sentence what that particular occupation involves. 8 Would doctors have prescribed antibiotics to treat a stomach ulcer before it was discovered that stomach ulcers were caused by a bacterial infection? Justify your answer.

INvESTIgATE 9 Interview a person who works in a health-related profession. Summarise the interview in a report with the following headings. (a) Name (b) Occupation (c) Place of work (d) A typical day at work (e) Personal attributes required for this occupation (f) Study required for this profession 10 Find out what ingredients make Aspro tablets fizz in water.

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LOOKING BACK 1 Use the table below to answer the following questions. Major causes of death in Australia Year: 1919 20% pneumonia 10% heart disease 8% tuberculosis 7% accidents 5% cancer 4% stroke

Year: 2001 29% cancer 21% heart disease 9% stroke 5% asthma, emphysema, bronchitis 4% accidents 2% diabetes 2% pneumonia and influenza

(a) Account for the fact that the percentage of people dying from diseases such as pneumonia has decreased greatly since 1919. (b) Explain why the percentage of people dying from heart disease has increased so much. (c) What new additions to major causes of death are listed in 2001? (d) Explain why you think each of the diseases in part (c) has emerged as a major killer. (e) Account for the fact that accidental deaths have decreased so much. 2 Charlotte wanted to find out if antibacterial soap really works. She prepared two agar plates. She swiped her fingers over the surface of plate A. She then washed her hands with antiseptic soap and wiped her fingers over the surface of plate B. She incubated both plates. Her results are shown below. A

B

(a) Write a conclusion for Charlotte s experiment. (b) Which plate was the control? (c) What were the independent and dependent variables in this experiment? (d) Which variables need to be controlled in this experiment so that it is a fair test? 3 Jossie wanted to find out the best conditions for growing bread mould. She put a slice of bread on each of five plates and left the plates in various locations around her house. Her results are shown below. Observations after Location 3 days Fridge No mould Freezer No mould Kitchen bench Small amount of mould (a) 25% of bread covered Top of fridge with mould 50% of bread covered Bathroom with mould cupboard(b)

Observations after 6 days Small amount of mould No mould 50% of bread covered with mould 75% of bread covered with mould 100% of bread covered with mould

(a) The top of the fridge is warmer than room temperature. (b) The bathroom is humid for most of the day.

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(a) What conditions promoted the growth of mould? (b) Why did the bread go mouldy a lot more slowly inside than on top of the fridge? Why did the bread not go mouldy in the freezer? (c) Suggest some improvements to Jossie s experiment. 4 Equipment used in a doctor s surgery must be sterilised before use. Suggest why. 5 When antibiotics first became widely available, doctors prescribed them to treat even minor coughs and colds. Today, doctors usually prescribe antibiotics only if the patient does not improve after a few days and the disease is highly likely to be caused by a bacterial infection. Explain why doctors have become more cautious. 6 The skin is described as the first line of defence against disease. Explain why.

teSt YourSeLf 1 Which of the following lists contains only non-infectious diseases? A Down syndrome, lead poisoning, lung cancer B Down syndrome, polio, diphtheria C Smallpox, polio, diphtheria D Smallpox, lung cancer, polio (1 mark) 2 A particular type of bacteria divides every 20 minutes. If you started with one bacterium, after 20 minutes, there would be two bacteria; after another 20 minutes, there would be four bacteria. How many bacteria would there be after 80 minutes? A 6 B 6 C 16 D 32 (1 mark) 3 Which of the following foods use microbes as part of its manufacturing process? A Chocolate B Bread C Ham D Cheese (1 mark) 4 Which of the following groups of organisms contains the smallest organisms? A Bacteria B Insects C Protozoa D Fungi (1 mark) 5 Choose an infectious disease that you have studied in this chapter. (a) Outline the cause of the disease. (b) Describe some of the symptoms of the disease. (3 marks) 6 Describe an experiment you could do to test the following hypothesis: There are more bacteria on a kitchen chopping board than on a toilet seat. (3 marks) work sheets

17.6 Staying healthy puzzles 17.7 Staying healthy summary

STUDY CHECKLIST types of diseases

ICT eBook plus

■ distinguish between infectious and non-infectious diseases

17.1

■ recall examples of diseases caused by each of the following types of pathogens: bacteria, fungi, viruses and prions 17.1

bacteria ■ describe how bacteria reproduce 17.2 ■ outline how bacteria can be grown in the laboratory

SUMMARY

eLessons Killing Australians You may think that venomous snakes or spiders are the leading cause of death in Australia, but you d be wrong. Learn about the different types of diseases which are proving to be Australia s biggest problem and the factors which come into play when helping to minimise the chance of contracting these killers. A worksheet is included to further your understanding.

17.2

■ describe harmful and beneficial effects of bacteria 17.3 ■ explain why bacteria are a vital component of all ecosystems

17.3

viruses ■ discuss whether viruses should be classified as living or non-living

17.4

Skin ■ describe the structure of the skin 17.6 ■ outline the role of the skin 17.6 ■ explain what happens when the process of cell division gets out of control in the body 17.7 ■ outline how you can minimise the risk of skin cancer 17.7

applications and uses of science ■ outline the role of Alexander Fleming and Howard Florey in the development of antibiotics

Searchlight ID: eles-0069 A cure? Skin cancer is the most common form of cancer in Australia with around 400 000 people diagnosed each year. Learn about the revolutionary new trials led by Australian scientists to find a vaccine for skin cancer. A worksheet is included to further your understanding.

17.5

■ assess the advantages and disadvantages of using antibiotics to treat diseases

17.5

current issues, research and development ■ list some careers in the field of medical science and outline what each career involves

17.8

Searchlight ID: eles-0070

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18

The night sky

On a clear night, thousands of stars are visible to the naked eye, although some of the fainter stars might only be seen away from the light pollution created by street and city lighting. It is difficult to comprehend the scale of the universe. The sun, our closest star, is crucial to our own existence as it provides the heat and light that all life depends on. However, it is rather average for a star, with a diameter of 1.4 million km and a temperature of 6000 C at its surface. The sun is just one of billions of stars that make up the Milky Way Galaxy, and there are thought to be billions of galaxies in the universe.

In this chapter, students will: 18.1 ◗ describe some major features of the

universe, including galaxies, stars and nebulae ◗ relate the solar system to the Milky Way Galaxy and to the universe at large ◗ describe differences in sizes of, and distances between, structures making up the universe 18.2 ◗ relate the model of the solar system to

the observed sky ◗ interpret and compare celestial

objects visible in the night sky 18.3 ◗ describe developments in technology

that have transformed the study of astronomy and our understanding of the universe.

Infra-red image from NASAs Spitzer Space Telescope of the core of the spiral Milky Way Galaxy. Dust lying between Earth and the galactic centre would block a picture taken using visible light.

Thinking about the night sky 1. What are stars and what are they made of? 2. Each of the following objects might be visible in the night sky: • galaxies • planets • stars • moons • constellations. Arrange these objects in a table from largest to smallest. Work in pairs and use your current knowledge to suggest a definition for each term. 3. Observe the stars on a dark night, preferably around the time of a new moon. Draw the positions of the ten brightest stars and label your diagram to indicate the colour of each. 4. While observing the night sky, you might notice stars of different brightness and slightly different colours. Can you explain why? 5. Explain why the positions of stars change over the weeks and months. 6. What is a light-year? Why is it a useful concept in astronomy? 7. Outline the purpose of a telescope. If you have seen a telescope up close, describe how it works. 8. Form a group with two or three other students that have a different star sign from your own. Ask each group member to collect their horoscope from a magazine or newspaper each week for two to three weeks. Paste yours into your workbook and record whether any of the predictions seem to match incidents in your week. 9. Humans have sent numerous space probes into space. Conduct some research to outline where they have gone and what they have studied.

INVESTIGATION 18.1 Light pollution You will need: 2 sheets of A4 paper pen sticky tape torch ◗ Prick holes in a sheet of A4

paper using the tip of a pen to model the five stars of the Southern Cross (see page 476). ◗ Stick this sheet of paper over

another sheet and tape them both to a window so that daylight shines through them. ◗ Record your observations. ◗ Now shine a torch over

the stars and record your observations again.

DISCUSSION 1

What effect did shining the torch have on the visibility of the stars?

2

Explain what this investigation demonstrates about when and where astronomers can observe celestial objects.

18.1

A sense of perspective Light-years away The universe is so big it is difficult to comprehend its size. It would take light 12 15 billion years to reach the most distant objects in the universe. The closest star to our solar system that is visible to the naked eye, Alpha Centauri, is about 41 000 billion kilometres away. The distances between objects in the universe are so vast that expressing them in kilometres

would involve immense numbers. Instead, astronomers use a much larger unit of distance, the lightyear. A light-year is the distance that light travels in one year. If light travels 300 000 km per second, then in one year it travels 300 000 × 60 s/min × 60 min/h × 24 h/day × 365.25 day/yr = about 9500 billion kilometres. This means that Alpha Centauri is 4.3 light-years away. When we look at the stars, we see the light produced by them.

However, because of the vastness of space, that light takes a long time to reach us here on Earth. In fact, viewing stars is like looking back in history; the light we see today from Alpha Centauri was emitted 4.3 years ago. The galaxy nearest to our own, the Andromeda Galaxy, is the most distant object visible to the human eye; at 2.2 million light-years away we are looking at the light it released 2.2 million years ago, before the appearance of modern humans, Homo sapiens.

Possible black hole in centre Approximate location of our solar system on the Orion arm of the Milky Way Areas of glowing pink, blue and green gas are nebulae where new stars form.

50 0 00 l ight -ye ars Spiral arms

Direction of rotation

An artist s impression of the Milky Way. The Milky Way, along with our neighbouring galaxy, the Large Magellanic Cloud, forms part of the Local Group of galaxies.

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Galaxies On a dark night, a hazy white band can be seen across the sky. Greek legend explains that the hazy band of light was formed from milk spilled by the baby Hercules. The hazy band is actually part of the Milky Way Galaxy that we live in. The word galaxy comes from the Greek word gala, meaning milk. A galaxy is made up of a huge number of stars and dust, held together by gravity. A hundred years ago, astronomers believed that the Milky Way Galaxy was the only galaxy in the universe. Thanks to developments in optical telescopes and radio telescopes, astonomers have now detected about 100 billion other galaxies. With the help of the Hubble Space Telescope in orbit around the Earth, astronomers have been able to locate galaxies that are more than one billion lightyears away!

Galactic shapes How can we see the Milky Way Galaxy if we are in the Milky Way Galaxy? The answer lies in its shape. The Milky Way is shaped like a spiral, with arms coming from its centre. Our solar system is located on one side of the galaxy, on a spiral arm called the Orion arm. When looking at the Milky Way in the night sky, you are actually seeing the stars in the central part of the spiral. American astronomer Edwin Hubble recognised that galaxies could be grouped according to their shapes. Galaxies like ours are called spiral galaxies. Elliptical and irregular galaxies are two other types.

also a spiral galaxy. At 2.2 million light-years away, it is the most distant object visible from Earth with the naked eye.

Irregular galaxies These have no definite shape. Irregular galaxies tend to have very hot, new stars mixed in with lots of dust and gas. The Magellanic Clouds are two small, irregular galaxies that look like two fuzzy clouds near the constellation called the Southern Cross. They are the closest galaxies to our own Milky Way Galaxy. The gravitational pull between all three galaxies is so strong that eventually they will all become part of the Milky Way Galaxy.

Elliptical galaxies Elliptical galaxies are oval or egg-shaped galaxies. They contain masses of old red stars with little gas or dust. Unlike spiral galaxies, the stars in elliptical galaxies move around in every direction. Elliptical galaxies, such as M87, have grown to an enormous size by pulling in other galaxies.

Spiral galaxies Spiral galaxies rotate. They have a bright bulging middle with two or more curved arms of stars spiralling out from the centre. The middle parts of spiral galaxies spin faster than the edges. The older red stars are found closer to the centre and the younger blue stars are located on the outer arms of the spiral. The Andromeda Galaxy is

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Barred spiral galaxies

Nebulae

These are a type of spiral galaxy. However, the central disk is replaced by a bar-shaped middle. In barred spiral galaxies, arms spiral out from either end of the bar.

In the photograph of the constellation Orion below, there is a cloudy-looking, pink region. This is the Orion Nebula, known as M42. It looks small, but it is about 30 light-years across. A nebula is a cloud of gas and dust. In some nebulae, such as the Orion Nebula, stars begin to form as the gas and dust come together due to the force of gravity. The centre of the nebula heats up, causing it to glow.

The constellation Orion. Part of this constellation is also commonly known as the Saucepan.

A computer-simulated view of a cluster of galaxies far from our own Milky Way Galaxy

The two Antennae galaxies colliding. During this collision, billions of stars will be formed. They give us a preview of what may happen when our Milky Way Galaxy collides with the neighbouring Andromeda Galaxy in several billion years.

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Not all nebulae glow. Some of them absorb light from nearby stars and appear as dark spots in the sky. One of these dark nebulae can be seen in the Southern Cross constellation as a dark patch to its lower left. It is known as the Coal Sack.

The Southern Cross and the Pointers. The Coal Sack Nebula is the dark patch to the lower left of the Southern Cross.

The Carina Nebula in the Milky Way Galaxy. New-born stars are visible within the pillars of dust and gas. The colours in this image are not actually visible but have been computer generated based on the different elements present in the nebula; for example, red indicates sulfur emissions, green indicates hydrogen, and blue indicates oxygen.

Activities REMEMBER 1 Explain why so many more stars are visible in the night sky in rural areas than in the city. 2 Define the term light-year and identify the number of kilometres in a light-year. 3 Identify how big the universe is thought to be. 4 (a) Identify four types of galaxies. (b) Name an example of each type of galaxy. 5 Identify the diameter of the Milky Way Galaxy. 6 Outline where we are located within the Milky Way Galaxy. 7 Identify the force that holds the stars together within a galaxy or nebula. 8 Name the galaxy closest to our own. 9 Define the term nebula . Why are they such important objects?

THINK 10 Explain why stars (apart from the sun) are not visible during the day.

11 Explain why looking at stars is like looking back in time. 12 Arrange these astronomical objects from largest to smallest: galaxy, moon, universe, planet, star, nebula. 13 Explain why we can see the Milky Way in the night sky even though we are within this galaxy.

CALCULATE 14 It takes 8 minutes for light from the sun to reach the Earth. If light travels at 300 000 km/s, calculate the distance of the sun to the Earth in kilometres. 15 The distances to some prominent celestial objects are listed below. Copy the table and calculate the time it would take a space probe to travel from Earth to each

destination if travelling at a speed of 6 km/s (using current technology) as follows: time taken by space probe = 300 000 km/s time taken by light × 6 km/s eBook plus

16 Create a poster or PowerPoint presentation of some fascinating images of stars, nebulae or galaxies taken using telescopes. Use captions to convey the information that these images reveal. As a starting point, use the Galaxies weblink in your eBookPLUS to find images of different galaxies. work sheet

Destination Moon Mars (at its closest point in orbit) Sun Alpha Centauri (the closest star visible in the night sky) Sirius (the brightest star in the night sky) Large Magellanic Cloud (a galaxy close to the Milky Way)

18.1 A long way from here

Time taken Time taken by by light a space probe seconds 1.3 seconds minutes 3.1 minutes minutes 8.3 minutes years 4.3 years years 8.7 years years 179 000 years

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18.2

Stars and constellations The brightness of stars Many stars in the night sky are visible to the naked eye. One of the brightest celestial (sky) objects is, in fact, not a star but the planet Venus. Unlike stars, planets do not produce their own light but reflect the sun s light. Stars are immense spherical masses of hydrogen gas undergoing a fusion reaction, producing helium and enormous amounts of light and heat energy. The brightness of a star does not necessarily tell us how far away a star is. The closest star to our solar system, Proxima Centauri, was not discovered until modern telescopes were invented. It is so dim that it cannot be viewed with the naked eye or even a basic telescope. The brightest star in the sky is Sirius. It is almost twice the distance of Proxima Centauri, at 8.6 light-years from Earth, but Sirius is much larger.

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eLesson

Twinkle, twinkle Have you every wondered why stars twinkle? Find out in this video lesson. eles-0071

INVESTIGATION 18.2 The brightness of stars You will need: graph paper with millimetre squares ruler small torch ◗ Colour in a small

circle with a diameter of about 1 cm to represent the Earth on a sheet of graph paper. ◗ Hold a torch, representing a star, 2 cm from the graph

paper and record the diameter of the circle of light created. ◗ Move the torch back a further 2 cm at a time and

repeat the process until the diameter of the light circle exceeds the size of the graph paper. ◗ Record the proportion of total light output of the star

received by the Earth (as a percentage) at each distance as follows: proportion of light received =

diameter of Earth × 100 diameter of light circle

◗ Record all your data in a suitable table. ◗ Plot a line graph to demonstrate the relationship

between the distance from a star (x-axis) versus the proportion of light received on Earth (y-axis). Draw a line of best fit.

DISCUSSION 1

This investigation models the effect of distance on the brightness of stars viewed from Earth. Write a suitable conclusion for this investigation.

2 What benefits does modelling have in science? Sirius, the brightest star in the night sky

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Twinkling stars

Giant stars and dwarves

Stars appear to twinkle in the night sky. This is because the light travelling from a star is distorted by the Earth s atmosphere. The light is bent in all directions as it passes through the moving air of the atmosphere, which causes the image to change slightly in brightness and position and hence twinkle. This is one of the reasons the Hubble telescope in orbit high above the Earth is so successful at capturing clear images of celestial objects. In space, there is no atmosphere to make the stars twinkle, allowing a much better image to be obtained.

Rigel and Betelgeuse in the constellation Orion are both examples of stars known as supergiants. Both of these stars are much larger than the sun and both are in the process of dying. Their hydrogen fuel is running out, causing them to swell up. They appear as different colours because they have different temperatures. Rigel is much hotter than Betelgeuse and is a blue supergiant, while Betelgeuse is a red supergiant. Eventually, both of these stars will explode. Stars similar in size to our own sun also swell up as their fuel supply gets low. They turn red and are known as red giants. The outer layers are eventually blown off leaving behind a small, but very hot core called a white dwarf.

Light from a star

Earth Layers of the atmosphere

Pockets of warm and cold air in the Earth s atmosphere bend light from a star, making the star appear to twinkle. When stars similar in size to our own sun get low on fuel, they swell up to become red giants and then explode, leaving behind a solid, heavy core called a white dwarf.

INVESTIGATION 18.3 Twinkling stars You will need: aluminium foil glass dish torch ◗ Fill a glass dish with water. ◗ Take a sheet of aluminium foil large enough to cover the

◗ Put the crinkled foil under the glass dish. ◗ Darken the room and then shine a light down at an

angle into the dish while the water is still. Observe the reflected image. ◗ Stir the water and, while it is still moving, shine the torch

into the dish and once again observe the reflected image.

DISCUSSION 1

What effect did the turbulence of the water have on the image of reflected light?

2

How do these results help explain why stars twinkle?

base of your dish. ◗ Crinkle the foil into a loose ball then open it out again.

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Constellations Astronomers of ancient civilisations grouped stars according to the patterns or shapes they seemed to form. These shapes were usually of gods, animals or familiar objects. Today, astronomers divide the sky into 88 regions of stars. The group of stars within each region is called a constellation. When viewed from Earth, the individual stars in a constellation may appear to be very close to each other. However, they can be separated by huge distances in space and in fact have no real connection to each other at all. The stars that make up the constellation Orion, for example, are at very different distances from Earth.

In ancient times, it was thought the stars wandered through the night sky; today we explain the stars’ apparent movement in terms of the motion of the Earth through space as it orbits the sun. Over the course of an evening, the positions of constellations appear to move from east to west. This is due to the Earth’s spin. Just like the sun and the moon, stars rise in the east and set in the west. A time-lapse photograph of the stars taken over several hours shows the changing positions of the stars due to the Earth’s spin. The central point around which the star trails appear to rotate is called the South Celestial Pole and it indicates the Earth’s axis of rotation. Perpendicular to orbit

Axis tilt

North Celestial Pole

Direction of orbit around the sun

225 200 175 150 125 100 75 50

ars ye htLig

Ecliptic

South Celestial Pole

25

Rotational axis Graph showing the distances that stars in the constellation Orion are away from Earth

Stars appear to move around the celestial poles due to the spin of the Earth.

The constellations visible on any given night depend on the time of year. For example, Gemini and Leo are clearly visible in March but not in October. Virgo, Leo Autumn Libra, Scorpio, Sagittarius

Taurus, Gemini Winter

The constellations that are visible depend on the position of the Earth in space.

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Sun

Summer

Spring Aquarius, Capricorn

Star trails produced by time-lapse photography

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The zodiac Twelve constellations pass through what is known as the ecliptic, the path that the sun traces in the sky during the year. Ancient Greek astronomers believed that these twelve constellations had a special significance and are known today as the constellations of the zodiac.

Comparing astronomy and astrology Some people today confuse the terms astronomy and astrology. Until a few hundred years ago, there was hardly any difference between them, but today, with our systematic study of the night sky, they are seen to be quite different. Astronomy is the scientific study of our solar system and its place in the Aries

Taurus

March 21 April 20

April 21 May 21

Cancer

Leo

June 22 July 23

July 24 August 23

Libra

Scorpio

September 24 October 23

October 24 November 22

Capricorn

Aquaruis

December 22 January 20

January 21 February 19

The signs of the zodiac

(22 May – 21 June) Take your time this week and don t make any hasty decisions. It is important that you make time to relax or your health will suffer. ou are spending too much effort trying to please others. eep an open mind when it comes to friends, and don t be too quick to judge. Think carefully about your finances this week if you want to improve your long-term prospects.

A horoscope prediction for a Gemini someone born between 22 May and 21 June

universe. Astrology is a study of how the positions of the sun, moon and planets are said to affect our lives. Before people began to understand the science of space, many cultures thought events in the skies were the work of gods. Eclipses, comets, a full moon or the return of the sun Gemini after a long winter were signs from the gods for people to take action or to make decisions. May 22 The ancient Greeks June 21 believed that events on Earth (such as a Virgo person s birth) were influenced by whatever constellation was passed by the sun at August 24 that time. These beliefs September 23 gave rise to what we call horoscopes. Sagittarius In a horoscope, each of the zodiac s 12 constellations becomes a star sign. Each has its own November 23 symbol and special December 21 features. Astronomers are Pisces scientists. They make and use observations to learn more about the universe, Febuary 20 including our solar March 20 system. Astrologers are not scientists.

However, they make predictions about people s lives based on star signs and observations of the sun, moon and planets. The dates listed in horoscopes are based on when the sun passed in front of each constellation over 2000 years ago. Today, those dates are different, but the dates for each horoscope remain the same.

Navigation by the stars For thousands of years, sailors used the positions of the stars to guide them on long sea journeys. The invention of the sextant in 1731 made it much easier to do this. It enabled sailors to work out their latitude, position from the equator, by measuring the angle of a particular star above the horizon. In the Southern Hemisphere, the stars used for navigation form the Southern Cross. This group of stars is used because the angle between the horizon and the Southern Cross is always equal to the latitude of your position. Sailors used clocks to calculate the longitude of their position. Longitude measures your position around the globe from Greenwich near London, which acts as a reference point. Today, sailors use the global positioning system (GPS) to find their way across the oceans. Special GPS receivers that look a bit like mobile phones are used to process data from 24 satellites. The GPS gives a position accurate to within 15 metres.

A sextant used by early sailors

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DISCUSSION

INVESTIGATION 18.4 Star charts

1

The stars you drew should be in about the same position a few nights later, but the moon will have moved. Explain why, in terms of the motion of the moon.

2

When viewed a few weeks later, the stars are in a slightly different part of the sky. Explain why, in terms of the motion of the Earth.

◗ Go out one night when the moon is visible and try to find

some stars that appear close to the moon. ◗ Sketch the positions of the moon and nearby stars. ◗ Go out one or two nights later at the same time and

compare your drawing with what you see. ◗ Go out a few weeks later at the same time and compare your drawing again with what you see.

INVESTIGATION 18.5 Using a sky map A sky map, sometimes called a star chart or star map, shows the positions of planets, stars and constellations visible in the night sky from a given location at a certain time of the year. Use the Star maps weblink in your eBookPLUS to find and print a map of the stars for the current month of the year. A key is provided with most star maps to indicate whether the celestial object viewed is a planet, star or other object. The brightness of stars is indicated by the diameter of the circle depicting them. A magnitude scale is used to compare the brightness of stars; brighter stars such as the Southern Pointers have a low magnitude value while fainter stars have a larger magnitude value. You will need: star map for the Southern Hemisphere for the current month small torch (preferably with red cellophane taped over the end) pair of large binoculars or a telescope (optional) highlighter pen

the outer circular edge represents the horizon. ◗ Use the small torch to view your star

map at night. ◗ Find the Southern Cross constellation

and the two nearby Pointers, Alpha and Beta Centauri. There are many crosses in the night sky; the key to finding the Southern Cross is locating the pointers alongside. ◗ If you have a pair of large binoculars

or a telescope, locate and view some prominent celestial objects near the Southern Cross. Southern Cross Jewel Box Beta Centauri Coal Sack

• The Coal Sack is a dark patch in the Milky Way between the two brightest stars of the Southern Cross (Alpha and Beta Crucis). This is a dark cloud of gas about 60 lightyears across and 500 light-years away that blocks our view of the stars in the Milky Way behind it. • The Jewel Box is a bright cluster of stars on the edge of the Coal Sack and near Beta Crucis. It gets its name from the various colours visible when the stars are viewed through a telescope. The Jewel Box contains about 50 bright stars, all of which are only a few million years old. It is about 25 light-years across and about 7700 light-years away. ◗ Locate the approximate position of the South Celestial Pole by following the line of the long arm of the Southern Cross and finding where it intersects with a line perpendicular to the line joining the two Pointers.

Alpha Centauri Canopus Southern Cross

Gamma Crucis

Beta Crucis

Delta Crucis

Pointers

South Celestial Pole

◗ Select a clear night, preferably with

little moonlight available.

Achemar

Epsilom Crucis

◗ Once you have selected a viewing

position, you might like to lie down and turn the chart so that the direction you are facing (north, south, east or west use a compass if you are unsure) is shown at the bottom of the map. The centre of the chart represents the point directly above your head, called the zenith point, and

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Alpha Crucis

South ◗ Locate as many constellations and

• Alpha Centauri, at 4.3 light-years away, is the closest star visible to the naked eye in the night sky.

other prominent celestial objects as possible. ◗ Highlight each of the constellations on your sky map once you have viewed them.

Activities REMEMBER 1 Identify the: (a) closest star to Earth apart from the sun (b) brightest star in the night sky.

we see the constellation Leo. The ancient Greeks that created the star signs lived in the Northern Hemisphere.) 15 The five main stars of the Southern Cross constellation are shown on page 476. All five stars appear to be the same distance from the Earth but they are not. The brightness of each star and its actual distance from Earth are listed in the table below.

2 Explain why stars appear to twinkle. 3 Define the term constellation .

Distance from Earth (light-years)

Brightness (magnitude value)

4 Name the 12 constellations of the zodiac.

Star

5 There are 88 named constellations. What is special about the 12 constellations of the zodiac?

Alpha Crucis

321

0.8

Beta Crucis

353

1.3

6 Explain why different constellations are visible in different months of the year.

Gamma Crucis

88

1.6

Delta Crucis

364

2.8

Epsilon Crucis

228

3.6

7 Explain why the positions of stars appear to change over the course of an evening. 8 Define the term South Celestial Pole and describe how it can be found. 9 Outline the difference between astronomy and astrology. 10 Outline what a horoscope is.

THINK 11 The Hubble Space Telescope was put into orbit around the Earth in 1990. Explain why this telescope was responsible for the discovery of many new galaxies and other celestial objects. 12 In Investigation 18.5 on page 476 it was suggested that the torch should be covered in red cellophane. Explain why. 13 Refer to a star map to identify a: (a) star of magnitude 0 (b) constellation along the ecliptic (c) planet that should be visible. 14 The diagram below shows how the stars in the Leo constellation appear above Australia. Trace the positions of the stars into your workbook. Check the horoscope on page 475 to find the symbol for Leo and attempt to join the stars with straight lines to form a shape that looks like the Leo symbol.

(a) Identify the star closest to the Earth. (b) Identify the brightest star. (c) Beta Crucis and Gamma Crucis have a similar brightness when viewed from Earth. Identify which star produces more light and justify your response.

CREATE 16 Use the internet to research the arrangement of stars in the constellation of your zodiac sign. Copy the arrangement onto A4 paper so that the stars cover most of the paper. Poke holes through the stars, making larger holes for brighter stars. Use one of the following two methods to display your constellation: ◗ Join the stars with straight lines to display the object that the constellation is based on. Attach the paper to a window to allow light to illuminate the stars. ◗ Put the paper onto an overhead projector and project the stars onto a whiteboard. Use a whiteboard marker to draw straight lines between the stars. eBook plus

17 Match each constellation to the correct representation on the sky map by completing the Star matching interactivity in your eBookPLUS. int-0232 18 Use the Star maps weblink in your eBookPLUS to print a map of the stars for any month of the year. 19 Use the NASA weblink in your eBookPLUS to learn more about the United States space program in the past, today and into the future. 20 Use the Hubble weblink in your eBookPLUS to see images taken by the Hubble Space Telescope. work sheets

(Note: The diagram that you draw should be upside down. Because we live in the Southern Hemisphere, this is how

18.2 18.3 18.4 18.5

Constellations Star brightness Star maps Semicircular sky map

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18.3

PRESCRIBED FOCUS AREA Applications and uses of science

Probing the universe Our understanding of the universe has increased phenomenally over the past century as a result of remarkable technological advances in the field of astronomy. From the use of the first telescopes in the 1600s to the development of radio telescopes in the 1940s, astronomers have sought to collect and analyse information from distant stars and galaxies. More recently, space missions have deployed satellites in orbit around the Earth beyond the obscuring atmosphere to peer into the more distant reaches of the universe. Scientists now have the ability to send space probes to visit distant planets in our solar system to collect data, enabling a better understanding of our planetary neighbours.

The optical telescope In 1609, Galileo Galilei became the first person to use a simple optical telescope to view the night sky. Among other things, he was the first person to see the craters on the moon. He also discovered the four largest moons around Jupiter and that the Milky Way was actually made up of millions of stars. The invention of the optical telescope allowed us to start uncovering some of the secrets of the universe.

Optical telescopes collect light and make distant objects appear much closer. Observatories have huge telescopes that are able to view more distant objects because their large diameter collects more of the dim light. They are usually built far from the lights of cities and high on mountains to minimise distortion by the atmosphere. These types of optical telescopes can also split the light being collected from a star and give information about the object s temperature, movement and even the chemicals it is made of.

Radio telescopes As well as light, stars give off other types of radiation such as ultraviolet rays and radio waves. Radio waves, for example, are used on Earth by televisions, mobile phones and radios. The finder scope is used to find objects in the sky. It helps you line up the main telescope.

Light from distant stars enters here.

The eyepiece for the main telescope

Flat mirror

A closer look with a telescope When Galileo pointed a telescope at the planet Saturn, he said it had ears . What he was really looking at was Saturn s rings. If you pointed an optical telescope at Venus you would see that it has phases just like our moon. You would also be able to see the famous Great Red Spot on Jupiter.

Concave mirror

The tripod supports the heavy telescope and helps keep the telescope steady. Optical telescope

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Radio telescopes collect radio waves that are emitted by distant objects. These telescopes are shaped like huge dishes, with a central antenna. The dish focuses the collected radio waves onto the antenna. The antenna then sends the signals to a computer, which creates an image of the object. Radio telescopes are able to see through dust in space. For this reason, they were the first telescopes to detect planets outside our solar system. Radio telescopes can take images through the centre of galaxies where stars are forming. Radio waves

Receiving antenna

Radio waves

people on missions to these far away places, not to mention the danger involved! So, scientists use technology to gather information out in space and transmit it back to Earth. The former Soviet Union sent up the first spacecraft in 1957. Since then, scientists have sent satellites, space probes, space stations and space shuttles out of the Earth s atmosphere. Each type of spacecraft is sent to carry out a different mission.

Putting people into space The first living things in space were two Russian dogs. They orbited the Earth in 1960. Eight months later, a Russian cosmonaut became the first human in space. The Soviet Union and the United States raced to put the first man on the moon. In 1969, America won the race when Neil Armstrong became the first human to walk on the moon. In more recent times, space shuttles have taken their crews to fix satellites and work on space stations.

Parabolic reflector

A radio telescope detects radio waves using a parabolic reflector and receiving antenna.

Using technology to explore space Scientists are constantly learning more about the universe. As new technology is developed, new discoveries are made and new theories developed. Most of the objects in the universe that scientists study are a long way from Earth. It would take too long to send

Satellites A satellite is any object that orbits another object. The moon is a satellite of Earth because it orbits the Earth. It is a natural satellite whereas artificial satellites are those that scientists have built and sent into space. Some artificial satellites gather information about space. Others are involved with GPS technology or monitoring of climate, vegetation or land surfaces. The Hubble Space Telescope is a satellite that gathers information about stars and galaxies. It sends computer images back to Earth for scientists to analyse. Other artificial satellites are used with communication technologies, such as mobile phones. They receive radio and other signals from one place on Earth and beam them back to other locations on Earth.

The Solar and Heliospheric Observatory (SOHO) is the only artificial satellite to orbit the sun. The SOHO studies the sun and its atmosphere. SOHO was launched in 1995 to study the sun s interior and its atmosphere. Its results have been so valuable that its two-year mission has been extended to the current day. As well as providing new data about the sun, SOHO has discovered 1500 comets, making it the most successful discoverer of comets in the history of astronomy.

The Apollo 11 mission sent Neil Armstrong and his crew to the moon.

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Some significant developments in astronomy 3000 BC Egyptians developed calendars using the positions of the stars. They drew the oldest known constellation shapes. 2446 BC Chinese astronomers discovered that planets move in space. 370 BC Aristotle was a Greek philosopher and scientist. He believed that the Earth was not flat, even though most people in his time believed it was. He thought the Earth was the centre of the universe with the sun, moon and stars orbiting the Earth instead of the sun. AD 150 Greek astronomer Claudius Ptolemy studied the movement of the moon and the planets. He believed that the Earth was at the centre of the universe. His ideas and theories lasted more than 1400 years.

AD 1796 Pierre Simon Laplace of France suggested that the sun and the rest of the solar system formed from a cloud of gas called a nebula. AD 1687 Isaac Newton was able to explain why the planets orbited the sun. His Universal Law of Gravitation showed that all objects in the universe attract each other. AD 1609 Italian physicist and astronomer Galileo Galilei was the first to turn the optical telescope to the skies. His observations supported Copernicus theory over Ptolemy s. Galileo s ideas about astronomy conflicted with the ideas held by the Catholic Church at that time. So, at 74 years of age, he was placed under house arrest for the remainder of his life.

AD 1006 Chinese astronomers observed the brightest supernova ever recorded. A supernova is the explosion of a massive star at the end of its life. It shone for two months and was so bright that it could be seen even during the day.

Probes Space probes have been sent to other planets in the solar system. These probes can orbit a planet, fly past it or land on it. So far, no probe has returned to Earth. Special cameras on board the probes send images of the planets back to Earth. Other instruments may take readings to find out what substances are present in a planet s atmosphere.

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AD 1927 George Lemaitre of Belgium put forward the Big Bang theory that suggested that the universe formed in a huge explosion 13 15 billion years ago.

AD 1945 An amateur radio operator built the first radio telescope in America.

AD 1946 Edwin Hubble, an American astronomer, helped build the biggest reflecting telescope ever made. He observed that distant galaxies in every direction are moving away from the Earth.

AD 1974 Stephen Hawking, a physicist from England, developed ideas that improved our understanding of black holes. He believes the universe has no edge or boundary. AD 1543 Nicolaus Copernicus was a Polish mathematician and scientist. He suggested that the sun, not the Earth, was at the centre of the universe. He also explained the movement of the stars by the rotation of the Earth on its axis. It was a long time before anyone else believed his idea.

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AD 1905–1916 Albert Einstein developed his theories of relativity. Einstein greatly added to our understanding of the universe through his description of gravity and new ways of thinking about space and time.

AD 1977 The twin American space probes Voyager 1 and Voyager 2 were sent separately to the two largest planets in the solar system, Jupiter and Saturn. It took the Voyager craft two years to travel to Jupiter and a further two years to reach Saturn.

Once a probe has been launched, scientists guide it by remote control. Astronauts cannot visit a probe to make repairs. So, it is important for a probe to be built to last for many years. Voyager 1 and Voyager 2 are probes that were sent out in 1977. Their missions were to investigate Jupiter, Saturn, Uranus and Neptune. Both Voyager probes have continued to relay messages back to Earth well after their original missions have been completed.

AD 2008 NASAs Phoenix spacecraft landed on the surface of Mars and confirmed the presence of water ice in soil samples.

In 1989, NASA launched the Galileo space probe. It reached Jupiter in December 1995. Galileo was made of two parts. One part orbited Jupiter and a smaller probe entered the planet s atmosphere. After nearly an hour of collecting data, the smaller probe was vaporised by the heat of Jupiter s atmosphere, as scientists had predicted. The data collected by the probe has been valuable to scientists.

AD 1990 The Hubble Space Telescope became the first optical telescope to orbit the Earth. It is as big as a truck and orbits above the Earths atmosphere, where it can take crystal-clear images deep into outer space.

AD 1989 The Cosmic Background Explorer, or COBE, satellite was launched in 1989. COBE helped scientists understand how the universe expanded, cooled and then formed clumps of matter. These clumps eventually formed all the stars and galaxies. One of the Voyager spacecraft

Both of these probes now have new missions to travel to the outer reaches of our solar system. Both of the Voyagers have power and fuel to last them until about the year 2020.

Space stations Space stations are homes away from home! They are manned spacecraft, in which astronauts can live for months at a time. Space stations are

satellites; they orbit the Earth at an altitude of about 400 kilometres. Astronauts can conduct special experiments on space stations because they are not affected by gravity as they are on Earth. Living on space stations also helps scientists understand how the body reacts to living without the effects of Earth s gravity. This information could be valuable if we should ever live on the moon or another planet in the future.

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The first module of the International Space Station (ISS) was put into orbit around the Earth in 1998. By 2008, it was 85 per cent complete and will eventually consist of 14 pressurised modules including laboratories, docking compartments, airlocks and living quarters. Astronauts will be able to live on the ISS for three to six months at a time and conduct experiments under the unusual conditions present in orbit.

The International Space Station in 2008

Activities REMEMBER 1 Name two telescopes that detect types of radiation other than light. 2 Explain why observatories are usually built on hilltops or mountains. 3 Outline the universe proposed by Copernicus. 4 Explain why Galileo was placed under house arrest. 5 Many man-made objects have been launched into space. When was the first spacecraft launched? By which country? 6 The United States put the first man on the moon. (a) Name the first man to land on the moon. (b) In what year did he land on the moon? 7 Define the term satellite .

THINK 8 Sketch a diagram of what the universe looked like according to Aristotle.

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9 The images on the right show a portion of the night sky seen with the naked eye (top), binoculars (middle) and an optical telescope (bottom). Use these images to explain why telescopes are important pieces of technology. 10 Explain why radio telescopes are curved like a dish. 11 Explain why the Hubble Space Telescope can see further into space than telescopes on the ground. 12 Outline some reasons to support funding of the International Space Station.

INVESTIGATE 13 There is a type of optical telescope called a refracting telescope. Find out how it works and how it is different from a reflecting telescope. 14 Choose an astronomer from this chapter and write a short biography of the person. Include some personal information about the astronomer that is interesting for others to read.

15 Describe the history of the Hubble Space Telescope and some of the information it has revealed about the universe. work sheet

18.6 Space probes and satellites

LOOKING BACK 1 Define the term light-year .

16 Outline how the Southern Cross and Southern Pointers can be used to locate the South Celestial Pole.

2 How large is the: (a) universe (b) Milky Way Galaxy? 3 How old do scientists believe the universe is?

17 Outline how a star map indicates: (a) a galaxy (b) a planet (c) the brightness of a star.

4 Identify the type of galaxy in each of the following photos. A

B

TEST YOURSELF 1 Which of the following shows celestial objects arranged from smallest to largest? A Universe, galaxy, nebula, constellation, planet B Planet, constellation, nebula, galaxy, universe C Planet, star, nebula, constellation, galaxy, universe D Planet, nebula, star, constellation, galaxy, universe (1 mark)

C

D

2 The positions of stars change slowly over the course of the night because A the Earth rotates from east to west. B the Earth orbits the sun. C the stars orbit the sun. D the Earth rotates from west to east. (1 mark) 3 The brightness of the main stars in the constellation Orion is listed below.

5 If galaxies are so common, explain why only three can be seen with the naked eye. 6 Explain why looking at the night sky is said to be like looking back in time. 7 Outline how constellations and galaxies differ. 8 Identify where the solar system is located in the Milky Way Galaxy. 9 Define the term nebula and explain how it relates to stars. 10 Identify the constellation used by sailors in the Southern Hemisphere for navigation. 11 Explain whether the stars in a constellation are close together. 12 Identify the galaxy closest to our own and how far away it is. How long would it take a space probe to reach this galaxy if it could travel at half the speed of light?

Star

Betelgeuse Mintaka

Rigel

Bellatrix

Magnitude

0.45

0.18

1.64

2.25

The brightest star is A Rigel. B Mintaka. C Betelgeuse. D Bellatrix.

(1 mark)

4 The closest star to our solar system (apart from the sun) that is visible to the naked eye is A Proxima Centauri. B Alpha Centauri. C Rigel. D Betelgeuse. (1 mark) 5 Explain how any three developments in technology have increased our understanding of the universe. (6 marks) work sheets

18.7 The night sky puzzle 18.8 The night sky summary

13 The planet Venus and the star Sirius are clearly visible to the naked eye at night. Contrast these two celestial objects. 14 Outline the factors that affect the brightness of a star. 15 Explain why most of the constellations visible in summer are different from those visible in winter.

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STUDY CHECKLIST Galaxies and nebulae ■ define the term galaxy 18.1 ■ relate the solar system to the Milky Way Galaxy 18.1 ■ identify three different types of galaxies and give an example of each type of galaxy 18.1 ■ define the term nebula and relate it to the formation of stars 18.1 ■ define the term light-year and explain the need to use this large distance unit 18.1

ICT eBook plus

SUMMARY

eLessons Twinkle, twinkle Have you ever looked up at the stars on clear night and wondered why stars twinkle? Why do stars twinkle but not the moon? This video lesson helps to answer these questions and more. A worksheet is attached to further your understanding.

Stars and constellations ■ use the sizes of stars and their distances away to ■ ■ ■ ■ ■ ■

account for the brightness of different stars visible in the night sky 18.2 define the term constellation 18.2 use a sky map to locate and identify constellations, stars and other prominent celestial objects 18.2 explain why stars twinkle 18.2 account for the movement of stars and the difference in constellations visible at different times of the year 18.2 contrast astrology and astronomy 18.2 relate a zodiac symbol to the layout of a constellation s stars 18.2

Applications and uses of science ■ outline key developments in technology, including the use of optical and radio telescopes that have contributed to our understanding of the universe 18.3

Searchlight ID: eles-0071

Interactivities Star matching Constellations are names for groups of stars that appear in the sky. Test your knowledge of different constellations by matching them with the correct representation on the sky map. Instant feedback is provided.

Searchlight ID: int-0232

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19

The changing Earth

The Earth’s surface is constantly changing. Volcanoes and earthquakes can cause quick changes, but most of the changes to the Earth’s surface happen slowly. Rocks on and below the surface of the Earth are slowly and constantly being changed by natural events. Rocks also provide a valuable record of past events.

In this chapter, students will: 19.1 ◗ learn about the mineral composition

of rocks and how to distinguish between minerals 19.2 ◗ describe how igneous rocks are

formed and distinguish between different types of igneous rock 19.3 ◗ explain how rock weathers and how

the process of erosion redistributes sediment 19.4 ◗ understand how sediment is

deposited to form sedimentary rocks and distinguish between different types of sedimentary rock 19.5 ◗ learn how metamorphic rock is

formed from other rock types. They appreciate that the rock cycle describes the constant formation and reformation of rocks from one type into another in the lithosphere 19.6 ◗ appreciate how examination

of sedimentary layers reveals information about Earth’s history 19.7 ◗ understand that human activity

also causes changes to the Earth’s surface.

This aquatic reptile died over 300 million years ago. Fossils and the rocks in which they are found provide a valuable record of the past.

19 The changing Earth Thinking about the changing Earth The Earth is constantly changing. Some of the changes take millions of years — others take place within seconds. 1. Take a look at each of these images and write down what each tells you about the Earth and the way that the Earth is changing. (a)

(b)

(c)

(e)

(d)

2. Which one or more of the changes depicted in the photos above are caused or made worse by human activities? 3. How are rocks formed? 4. The terms ‘igneous’, ‘sedimentary’ and ‘metamorphic’ describe different types of rocks. Just from looking at the words, suggest how each type of rock is formed. 5. How many names of rocks do you know? List them and then, if you can, classify them as igneous, sedimentary or metamorphic.

19.1

Solid rock The Earth’s crust and the upper sections of the mantle form the Earth’s lithosphere (from the Greek words lithos meaning stone and sphaira meaning globe. It is in the lithosphere that rocks are formed by a variety of different processes such as melting, erosion, weathering, crystallisation and deposition. All rocks can be divided into three main groups: igneous, sedimentary and metamorphic. We will look in more detail at how each of these rock groups is formed.

What are rocks made of? Rocks are made up of substances that are called minerals. The term ‘mineral’ describes any solid material made up of a consistent combination of chemical substances that occur naturally. These chemical substances can take the form of chemical compounds (which are made up of combined elements) or elements found in

Many minerals leave a streak when rubbed against the rough surface of an unglazed white tile. Hematite has a red-brown streak. The streak left by a mineral and the actual colour of a mineral are not always the same. Not all minerals leave a streak.

their pure form. It is very unusual to find pure elements in nature but gold and diamond (which is made up of carbon that has been subjected to high pressure and heat) are two examples. These types of minerals are referred to as native elements. Most of the minerals that make up the Earth’s crust are compounds of oxygen and silicon; these are called silicates. They differ in appearance and in their chemical and physical properties due to variations in what metals they are combined with and the proportion of each element present in the mineral molecule. Two minerals may be made up of the same elements but differ in the proportions. For example, iron oxide (Fe2O3) is a reddish brown substance that gives rust its colour, whereas Fe3O4 forms magnetite, a dull grey stone. It can also happen that one mineral can come in a number of different colours. Quartz is made of silicon dioxide (SiO2) and, in its purest form, is a clear white stone. However, small impurities in the compound can cause quartz of every colour of the rainbow to exist. Generally, colour alone is not a good indicator of what mineral is present in a sample of rock. After all, a citrine, a topaz and a champagne diamond are all clear yellow stones but differ completely in chemical composition. Geologists consider a number of different properties in order to identify a specific mineral in a rock sample: • A mineral’s lustre describes how it reflects light from its cut

surface. The lustre of a mineral may be described as dull, metallic, pearlescent, glassy, brilliant, waxy or silky. • The transparency of the mineral describes how well light travels through it. Opaque minerals (such as iron oxide) do not let light through at all; transparent minerals (such as diamond and pure quartz) allow light to pass easily through them; while other minerals (such as calcite) are translucent, allowing only some light through a sample. • A mineral’s streak is the colour and texture of the mark that the mineral leaves behind when it is scratched across a hard white surface. Not all minerals leave a streak. • The fracture of a mineral describes the appearance of the break when a sample of the mineral is snapped. These properties are considered along with the mineral’s hardness. Geologists use a system called the Mohs’ hardness scale to determine this property. This scale was developed by the geologist Friedrich Mohs; it consists of a comparative list of ten minerals arranged in order from softest (hardness value of 1) up to the hardest (10). A harder mineral scratches a softer mineral. Typical minerals for each of the ten hardness values are shown on the next page. The hardness of a particular mineral can be found by comparing it with minerals on the Mohs’ scale. For example, if the mineral sample can be scratched by a piece of quartz but not by orthoclase, its hardness lies between 6 and 7.

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Ideally, you would keep a sample of each of the ten reference minerals handy, but it is possible to use common materials to find a mineral’s hardness. Some of these items and their typical hardness values are also shown in the diagram below. Softest

Mohs’ scale of hardness Talc

1

Gypsum

2

Calcite

3

Fluorite

4

Apatite

5

Orthoclase

6

Quartz

7

Topaz

8

Corundum

9

Diamond

10

1 Describe what the lithosphere is and where it can be found.

Soft grey lead pencil point

2 Define the term ‘mineral’. Recall at least two examples of minerals.

Fingernail Copper coin

3 Recall two examples of native elements. Iron nail

4 Identify which minerals are present in granite.

Sandpaper

5 Recall at least three properties that you could observe to help you identify an unknown mineral.

A scale for testing the hardness of minerals

◗ Scrape the mineral across the

unglazed side of a white ceramic tile. Record the colour of the streak.

Which mineral is it? You will need: mineral kit common materials to substitute for unavailable Mohs’ scale minerals magnifying glass white ceramic tile

◗ Use the Mohs’ scale minerals

or the common materials to estimate the hardness of the mineral by trying to scratch it. An approximate range, such as 5–6, is sufficiently accurate.

◗ Construct a table like the one

shown below and use it to record your observations as you work through the following steps for each mineral.

DISCUSSION 1

Other than those already described, what additional properties of minerals could be used to identify them?

2

If two unlabelled mineral samples have the same colour and lustre, can you be sure that they are the same mineral? Explain how you would find out.

◗ Describe the colour and lustre of

the mineral. ◗ Use the magnifying glass to look

closely at the mineral and describe the shape and size of its crystals. Properties of some minerals Mineral

Colour

Lustre

REMEMBER

Common materials

Hardest

INVESTIGATION 19.1

Activities

Crystal shape and size

Streak

Hardness

6 Identify the approximate hardness on Mohs’ scale (to the nearest whole number) of a mineral that can be scratched by sandpaper but not by an iron nail.

THINK 7 Distinguish between a rock and a mineral. 8 Explain what the size of the crystals in a rock tells you about the way the rock was formed. 9 You have a sample of each of two minerals but no other equipment to test them for hardness. How could you tell which mineral was harder? Explain your answer. 10 A mineral can be scratched by a copper coin but not by a fingernail. You know that the mineral is quartz, fluorite or calcite. Which mineral is it? Justify your answer. 11 Is table salt a mineral? Think carefully about your answer and suggest reasons for and against classifying it as a mineral. work sheet

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19.1 Identifying and classifying minerals

19.2

Fiery rocks Think about the word ‘igneous’ for a moment. Does this word remind you of any other words? How about ‘ignite’ or ‘ignition’? In fact, all of these words have a common origin and they come from the Latin word ignis meaning fire. So, we can think of igneous rocks as coming from a hot, fiery place. Igneous rocks are formed from molten rock from the upper sections of the mantle. The temperature in this part of the mantle can reach as high as 1400 °C. The molten rock from the mantle is called magma. The magma is pushed upwards into the crust by pressure in the mantle. In some places, the crust is very weak or has been ruptured so the magma can break through and flow onto the Earth’s surface. Magma that flows onto the Earth’s surface is called lava. Volcanoes are formed where the crust is weak, allowing magma to break through. Igneous rocks can be formed from either magma or lava. Those that have formed from magma that cooled below the surface are called intrusive rocks or plutonic

The batholith forms under the Earth’s surface when magma cools. 1.

rocks. They cool slowly and become visible only when the rocks and soil above them wear away. Large bodies of intrusive rock are called batholiths. These can stretch over distances of up to 1000 kilometres.

Extrusive rock forms from lava that cooled quickly above the surface.

Earth’s surface

Intrusive rock forms from magma that cooled slowly below the surface.

Igneous rocks can form below or above the Earth’s surface.

Cracks form in the batholith while it cools. 2.

Igneous rocks that are formed from lava cooling above the surface are called extrusive rocks. They generally cool very quickly. Igneous rocks that form from lava spilling from underwater volcanoes are also classified as extrusive rocks.

The softer rocks and soil around the batholith may wear away. 3.

4.

If a batholith is exposed to the environment, it will start to wear away along the cracks. Over time, the batholith may break down completely. The breakdown of rocks is called weathering.

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The appearance of an igneous rock depends on what substances were in the molten rock that it was made from and how quickly the molten rock cooled. The substances in an igneous rock determine its colour and hardness. Crystals are formed when lava or magma cools. The size of the crystals in an igneous rock depends on how quickly it cooled. Intrusive rocks have larger crystals than extrusive rocks because the crystals have had more time to grow. When lava emerges from a volcano, contact with the cool air or cold water makes it cool very quickly, not giving large crystals time to grow.

Common igneous rocks Frothy rocks Some violent volcanic eruptions shoot out lava filled with gases. The lava cools quickly, while it is still in the air, and traps the gases inside. Rocks that form this way are full of holes. Two examples of these rocks are pumice and scoria.

Pumice Pumice is a pale-coloured rock. It is very light because it is full of holes. It floats on water and sometimes washes up on beaches. Powdered pumice is used in some abrasive cleaning products.

Scoria Scoria is heavier than pumice and has more iron so it is darker than pumice. It is usually found closer to the volcano’s crater than pumice. Scoria is a red-brown

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or grey rock that can be used in garden paths or around drainage pipes.

Obsidian Obsidian is a smooth, black rock that looks like glass. It is formed when lava cools almost instantly. This rock is different from basalt because it cooled so quickly that no crystals formed. Sometimes very fine air bubbles are trapped in the rock, which give it a coloured sheen.

Basalt Basalt is an extrusive rock that can take on many appearances. One big difference between samples of basalt is the size of the crystals that make up the rock.

Basalt with bubbles When viewed under a microscope, it is apparent that the crystals in this basalt are large. This is because they formed from lava on the ground. The crystals had time to grow before the rock became solid. Notice the holes. The lava was filled with gases when it began to cool. The gases have since escaped.

Pillow basalt This rock formation came from a volcano that was once under water. The rocks formed from underwater volcanoes are smooth and round. The crystals in this basalt are so small that they are difficult to see.

Granite Granite is a common intrusive rock. The crystals in granite form over long periods of time and grow large enough to make them easy to see with the naked eye. Granite is very hard and can be used for building. Headstones and other monuments can be made from granite that has been polished to give it a glossy finish. The crystals found in granite are a mixture of white, pink, grey, black and clear minerals. These are quartz (clear to grey), feldspar (white and pink) and mica (black). Feldspar is made of aluminium silicate, and black mica is aluminium silicate combined with potassium, magnesium and iron.

INVESTIGATION 19.2 Does fast cooling make a difference? You will need: freshly made saturated solution of potassium nitrate potassium nitrate spatula 250 mL beaker 3 test tubes and test-tube rack test-tube holder Bunsen burner, heatproof mat and matches crushed ice safety glasses hand lens CAUTION Safety glasses must be worn during this experiment. ◗ Half-fill a beaker with crushed ice. ◗ Quarter-fill a clean test tube with saturated potassium

nitrate solution. Add a spatula of potassium nitrate to the solution. ◗ Gently heat the solution over a Bunsen burner flame until

the added potassium nitrate has dissolved or until the solution starts to boil. ◗ Pour half the warm solution into each of two clean test

tubes. ◗ Place one test tube in the beaker of crushed ice and the

other test tube in the rack to cool.

Activities REMEMBER 1 Describe two ways in which you can distinguish between intrusive and extrusive rocks. 2 Recall how a batholith is formed. 3 Summarise the differences between granite and basalt.

Crushed ice

Potassium nitrate solution Cool one solution quickly and the other one slowly. ◗ When crystals have formed in each test tube, examine

them with a hand lens.

DISCUSSION 1

Draw a labelled diagram of some crystals in each test tube, concentrating on their shape and size.

2

Which test tube contained the largest crystals — the one that cooled quickly or the one that cooled slowly?

3 Which type of igneous rock would you expect to have larger crystals, those that cool slowly beneath the surface or those that cool quickly above the surface or underwater? 4 Why do safety glasses need to be worn in this experiment?

THINK 9 Explain how you would decide whether an igneous rock came from a volcano. 10 Rhyolite is an extrusive rock that contains the same minerals as granite. In what way would you expect it to be different from granite? 11 In which of these two rocks did the lava cool faster? Explain your answer.

4 Recall why the crystals in pillow basalt are smaller than the crystals in basalt that formed on the ground. 5 Scoria and pumice are formed in a similar way. Explain why their colours are different.

8 Explain why pumice is so light.

INVESTIGATE 14 Locate a building, statue or memorial in your area made from granite. Describe the granite in the building or structure and explain why granite’s features make it so useful. eBook plus

6 Recall what type of extrusive rock could easily be mistaken for glass. 7 Describe one way in which intrusive rocks can become visible on the Earth’s surface.

(a) All intrusive rocks form batholiths. (b) Rocks are made up of substances called minerals. (c) All igneous rocks are extrusive rocks. (d) Intrusive rocks are more likely to have larger crystals than extrusive rocks. (e) Batholiths come from volcanoes.

12 Describe what the presence of ‘bubbles’ in rocks tells us about lava. 13 Identify which of the following are true.

15 Use the Who am I? weblink in your eBookPLUS to play the Rock Game and identify rocks from a series of clues. work sheet

19.2 Igneous rocks

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19.3

Wearing away Volcanoes continue to erupt, leaving igneous rocks on and under the Earth’s surface, yet the surface of the Earth’s crust isn’t a huge mass of solid rock. The actions of wind, water and ice constantly break down rocks on the Earth’s surface. The process of breaking down rocks is called weathering. Weathering is a slow process, but the rate at which it happens depends on the type of rock and the natural action involved. In a climate as severe as Australia’s, we can see many different examples of weathering. The action of the sea breaks off pieces of coastal rock, often leaving spectacular features such as the Twelve Apostles at Port Campbell National Park, Victoria. The wind wears rock away, especially in dry conditions when it blasts the rock with sand and soil it has picked up. Acid rain can form if there is a lot of pollution in the air. It can react with chemicals in rocks, making them crack and crumble more easily. Water on the ground can react with certain chemicals in rocks, soil and decaying plants, producing acids and bases that speed up the weathering of rocks. Weathering doesn’t change only rocks. It changes buildings, roads and cars — even your own skin weathers as you get older!

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The Twelve Apostles, on the coast of southern Victoria

Wave Rock, Western Australia, a spectacular example of weathering by the wind and chemicals

Tree roots widen the cracks in rocks.

1

INVESTIGATION 19.3 Chemical weathering You will need: piece of limestone distilled water dilute hydrochloric acid 2 dropping pipettes ◗ Put a drop of distilled water on

the piece of limestone. ◗ Put a drop of dilute

hydrochloric acid on a different part of the piece of limestone.

DISCUSSION 1

Does the distilled water have any observable effect on the limestone?

2

What is the effect of the dilute acid on the limestone?

Fast-flowing water can move sand, soil and even big rocks over long distances. All creeks and rivers flow to the sea or to inland lakes, but, by the time they reach the seas or lakes, the water flows much more slowly.

6 Sand is picked up by currents in the waves along one beach and deposited on other beaches. Strong winds have enough energy to pick up sand and carry it inland.

2 As the water slows down, the bigger rocks are deposited. 3 By the end of the river’s journey, all but very fine sediments have been deposited. 4 Coastlines can change quite quickly as a result of weathering, erosion and the deposition of sediments. 5 Ocean waves wear away the rocks that make up cliff faces. The waves pound rocks, smashing them into smaller and smaller pieces.

1

2

Carried away Weathered rock is usually moved from one place to another by the wind, running water, the sea or glaciers. This process is called erosion. The weathered rock moved by erosion is deposited and settles on the land, riverbeds and floors of lakes, seas and oceans to form sediments. Deposits of dead plants and animal remains are also called sediments. Soil is formed by weathering, erosion and deposition of rock. Soil also contains humus — decaying plant and animal material that plants can grow in. A fast-moving river is likely to carry sand, gravel and smaller particles with it. As it slows down on its path to the sea, it loses energy, and particles are deposited, forming sediments. The larger particles, such as gravel and sand, settle first. By the time the river reaches the sea, it is usually travelling so slowly that the very fine mud particles begin to settle.

3 5 4 6

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INVESTIGATION 19.4 Cracking up Some objects, like glass, crack if their temperature changes quickly. Rocks can do the same. The cracking occurs because the outer part of the rock cools more quickly than the inside of the rock after a hot day. Cracking can also occur when it rains on a hot day. The cracks gradually get larger, until large flakes begin to fall off. Granite often weathers this way.

You will need: mixture of garden soil, gravel, sand and clay large jar with lid watch or clock ◗ Before commencing this

experiment, form your own hypothesis about the order in which the different types of particles in the mixture will settle. Give reasons for your hypothesis. garden soil, gravel, sand and clay in a large jar to quarter-fill it. ◗ Add enough water to three-

quarters fill the jar and place the lid on firmly. Shake the jar vigorously.

Activities REMEMBER 1 Define the term ‘weathering’. 2 Recall five causes of weathering. 3 Define erosion, and describe how it differs from weathering. 4 Distinguish between a soil and a sediment. 5 As a flooded river slows down, identify which particles are likely to settle first: gravel, sand or fine clay.

THINK 6 The Sphinx and the Great Pyramids of Egypt have stood for thousands of years, yet weathering has affected them more during the past 50 years than in the previous years since they were built. Describe the most likely cause of increased weathering. 7 Acid rain is a serious problem in industrial areas where there is a

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Then compare your observations of the jar with your diagram.

Sediments and water

◗ Place enough of a mixture of

Trees can begin to grow within cracks in rocks. As the trees grow, the cracks are forced apart, eventually splitting the rocks. This speeds up weathering.

◗ Leave the jar for a day or two.

DISCUSSION 1

Which type of sediment settled after you first shook the jar?

2

Where are the other particles of sediment while the first layers are settling?

3

Draw a labelled diagram showing clearly any layers that form. Identify the layers if you can.

4

Which sediments settled after a day or two?

5

Why did the last sediments take so long to settle?

6

Was your hypothesis supported by your observations?

7

What is the relationship between the size of sediment particles and the time taken to settle?

◗ Put the jar down and watch

carefully as particles begin to settle. ◗ Note the time taken for each layer

of sediment to settle completely.

lot of air pollution. However, rain reaching the ground after falling through clean air is also slightly acidic. Explain how this could be. 8 Identify which feature of Wave Rock on page 492 is the result of: (a) weathering by wind (b) weathering by chemicals. 9 Describe some evidence of the weathering of: (a) buildings (b) cars (c) roads. 10 Compare the sediment found at the bottom of a still lake with the sediment on the banks of a mountain stream. 11 In alpine regions, rocks can be shattered by frozen water. Explain how this can happen. 12 What type of sediment would you expect to find on the bed of the Yarra River in Melbourne, the Derwent River in Hobart or the Swan River in Perth?

13 The Twelve Apostles on page 492 were originally named because 12 ‘stacks’ were close together along the western Victorian coast. Some of the stacks have since collapsed into the sea. (a) What is probably the main cause of the weathering of these stacks? Explain. (b) Which part of each stack is likely to weather most quickly? Justify your answer. (c) Has this coastal feature been caused by weathering, erosion or both? Explain your answer. 14 Why are larger sediments deposited before finer ones in river systems? 15 How much weathering and erosion would take place on the moon? How long would you expect a footprint to remain on its surface? Justify your answers. work sheet

19.3 Weathering and erosion

19.4

It’s sedimentary, Watson! Rocks that are formed from the particles of sediments are called sedimentary rocks. Most sedimentary rocks are formed from weathered rock that has been deposited due to erosion. Grains of sediment are cemented together to form a solid rock. The process is shown in the diagrams below. Sediments are laid down by ice, wind or water, in horizontal layers called beds.

Rocks from living things Limestone is a sedimentary rock that is formed from deposits of the remains of marine organisms such as shellfish and corals. The hard parts of these dead animals contain calcium carbonate. These deposits are cemented together over a period of time in very much the same way as sedimentary rocks form from weathered rock.

Within each bed, the sediment grains are squashed together so that they are in close contact.

Water seeps in between the grains, bringing with it many dissolved chemicals.

When the water evaporates, these chemicals are left behind as crystals around the edges of the grains. These crystals cement the grains of sediment together to form rock. Many sedimentary rocks form in this way.

Sandstone is formed from grains of sand that have been cemented together over a period of time. Mudstone and shale are formed from finer grains of sediment deposited by calm water in the form of mud. Siltstone has grains slightly larger than those of mudstone. Conglomerate contains grains of different sizes that have been cemented together.

This limestone, rich in corals and shells, is many metres above sea level. How did it get there?

Coal is formed from the remains of dead plants that are buried by other sediments. In dense forests, layers of dead trees and other plants build up on the forest floor. If these layers are covered with water before rotting is completed, they can become covered with other sediments. The weight of the sediments above compacts the partially decayed plant material. Over millions of years the compacting increases the temperature of the sediment and squeezes out the water, forming coal.

Rocks from chemicals

Conglomerate is formed from sediments that might be deposited by a fast-flowing or flooded river.

Some sedimentary rocks form when water evaporates from a substance, leaving a layer that is compressed after being buried by other sediments. Rock salt is an example of a rock formed in this way. It forms from residues of salt that remain after the evaporation of water from salt lakes or dried-up seabeds.

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Rocks in layers Layers of sedimentary rock are often clearly visible in road cuttings and the faces of cliffs. The limestone in the photograph opposite was formed on the ocean floor. Layers of sediments and sedimentary rocks can be pushed upwards by the same forces below the Earth’s surface that cause mountains to be formed. Those forces can also bend and tilt the layers.

Coal is used as a fuel. It is burned in electric power stations to boil water. The steam is then used to drive the turbines that produce electricity. In some countries, coal is burned in home heaters.

Using sedimentary rocks Sandstone and limestone are often used as external walls of buildings. These sedimentary rocks are well suited to carving into bricks of any shape. Shale can be broken up and crushed to make bricks. Limestone is broken up to produce a chemical called lime. Lime is used to make mortar, cement and plaster, in the treatment of sewage and on gardens to neutralise acid in the soil.

The chalk used to write on blackboards is like limestone, but it is not as hard as most limestone. Chalk is formed from very fine grains of calcium carbonate that have separated from sea water and settled to become a white, muddy sediment on the sea floor. The sediment hardens over time to form chalk. This process takes millions of years. The remains of shellfish and other sea animals are also found in the sediment that forms chalk, but most of these remains are microscopic. The white cliffs of Dover that overlook the English Channel are composed of chalk.

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Activities REMEMBER 1 Recall what all sedimentary rocks are formed from. 2 Explain, with the aid of a diagram, how grains of sand can become part of a sedimentary rock. 3 Sedimentary rocks that have formed from the erosion of weathered rock cannot be identified by their colour. Recall the feature that allows you to identify them. 4 Explain how a rock can be formed from the remains of animals. 5 Recall how coal is formed.

THINK

Layers of sedimentary rock can be pushed upwards, bent and tilted by forces beneath the Earth’s surface.

6 Explain why sedimentary rocks are found in layers. 7 A road cutting reveals a layer of sandstone beneath a layer of mudstone. Between them is a much thinner layer of conglomerate. Identify which layer would have formed: (a) from sediments beneath the sea (b) while the area was flooded by a swollen, fast-flowing river (c) while the land was the floor of a still lake (d) most recently. 8 Explain why limestone and coal are sometimes referred to as ‘biological rocks’. 9 Limestone is mostly formed on the ocean floor. Account for the fact that the Nullarbor Plain is riddled with limestone caves. 10 In which type of sedimentary rock would you be most likely to find embedded seashells? Explain.

INVESTIGATE 11 What do peat, brown coal and black coal have in common? Investigate what makes them different from each other. work sheet

19.4 Sedimentary rocks

19.5

Rocky changes Sedimentary rocks are those that have formed from deposits of weathered rock or the remains of living things. Igneous and sedimentary rocks deep below the Earth’s surface are buried under the huge weight of the rocks, sediments and soil above them. They are also subjected to high temperatures. The temperature increases by about 25 °C for every kilometre below the surface. This heat and pressure can change the composition and appearance of the minerals in rocks. The process of change in the rocks is called metamorphism and the rocks that are formed by these changes are called metamorphic rocks. The name for these changed rocks comes from the Greek words meta, meaning after or changed and morphe, meaning form.

• the amount of pressure caused by the weight of the rocks above • how quickly the changes take place. Metamorphic rocks that are mainly the result of great pressure can often be identified by bands or flat, leaf-like layers. These bands are evident in the sample of gneiss (pronounced ’nice’) pictured below left. The diagram below shows how rocks can be changed by the high temperatures that result from contact with hot magma. Layers of sedimentary rock

Other common examples of the formation of metamorphic rocks are: Shale (sedimentary)

Sandstone (sedimentary)

Limestone (sedimentary)

mainly pressure

⇒

mainly heat

⇒

mainly heat

⇒

Slate Quartzite Marble

Metamorphic rock

Hot magma

The formation of metamorphic rock by contact with hot magma

Shale is a common type of sedimentary rock. It has fine grains and crumbles easily along its layers. When shale is exposed to moderate heat and pressure, it forms slate.

Have you ever tried to lift one end of a pool table and noticed how incredibly heavy it is? It’s really heavy because the flat surface under the felt is not wood as you may have thought — it’s actually made of slate. Because of its natural hardness and its flat face, it makes an ideal even surface! Gneiss is formed mainly as a result of great pressure on granite.

The changes that take place during the formation of metamorphic rocks depend on: • the type of original rock • the amount of heat that the original rock is exposed to

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INVESTIGATION 19.5 Rocks — the new generation You will need: labelled rock samples including: granite gneiss limestone marble sandstone quartzite shale slate hand lens Marble forms from limestone under heat and pressure. It contains the same minerals as limestone.

◗ Try to sort the rocks into pairs of ’parent’ rock and corresponding

metamorphic rock. Use the examples on this page and the previous page if you have trouble pairing the rocks. ◗ Examine each pair of rocks with a hand lens.

Clues from metamorphic rocks The nature of metamorphic rocks above and below the ground can provide clues about the history of an area. Think about why the presence of quartzite or marble high in a mountain range would suggest that the area was once below the sea. The presence of slate might suggest that the area was once the floor of a still lake or river mouth. The sediments were probably buried under many other sediments and cemented together to form shale. The shale was transformed, or metamorphosed, into slate as a result of new rock formed above it.

Uses of metamorphic rock The strength, resistance to weathering and appearance of marble make it suitable for use in statues and the walls and floors of buildings (inside and outside). It is usually highly polished. The hardness, flat structure and strength of slate make it ideal for use in buildings, especially in roofing and floor tiles. The sedimentary rocks from which marble and slate are formed could not be used for these purposes.

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◗ Copy and complete the table below by noting the similarities and

differences between the ’parent’ and metamorphic rock of each pair. Comparing ‘parent’ and metamorphic rocks ‘Parent’ rock

Metamorphic rock

Similarities

Differences

Main cause of metamorphism

Shale Gneiss Sandstone Marble

DISCUSSION 1

Why is the term ’parent’ rock used?

2

Use the last column of your table to suggest whether the main cause of metamorphism was heat or pressure.

A tadpole grows into a frog, female frogs lay eggs, and eventually more tadpoles emerge from the eggs. That’s a life cycle. Some of the changes in rocks can be described as cycles too. Weathered rock is moved by erosion and the particles form sediments, which can be cemented together to form sedimentary rocks, which in turn may eventually change into metamorphic rocks. Once those rocks are exposed at the surface, the weathering starts all over again. A complete cycle normally takes millions of years, but sometimes never takes place at all. Why?

There are many cycles in nature. Some happen faster than others.

The rock cycle The rock cycle describes how rocks can change from one type to another. Weathering, erosion, heat, pressure and remelting

an at He

are processes that help change rocks. The rock cycle is different from other cycles because there is no particular order in which the changes happen. Some rocks have been unchanged on Earth

Hea t an dp

e sur res dp me Re

for millions of years and may not change for millions more. Some rocks change very quickly, especially near the edges of the plates that make up the Earth’s crust.

Wea the ring a

g ltin

er o

sio

Metamorphic rock

nd

res su re

n

Igneous rock Sedimentary rock

Weathering and erosion Remelting

Activities REMEMBER 1 Rocks are classified into three groups. Metamorphic rocks make up one of these. Identify the two groups of rock that metamorphic rocks are formed from. 2 Recall the processes that can cause rocks to change form and become metamorphic rocks. 3 Describe how the appearance of gneiss differs from granite. 4 Recall how granite can be transformed into gneiss. 5 Explain why slate is commonly used in floor tiles. 6 When sandstone is under heat and pressure, identify which metamorphic rock it might form. 7 Identify the rock type that slate is formed from.

8 Classify the following rocks as sedimentary, igneous or metamorphic. (a) Sandstone (b) Marble (c) Basalt (d) Gneiss (e) Granite

THINK 9 Explain what the bands in metamorphic rocks tell us about how the rocks were formed. 10 If an igneous or a sedimentary rock gets so hot that it melts completely, it does not become a metamorphic rock. Explain why. 11 Deduce why geologists describe limestone as the ‘parent’ rock of marble. 12 Metamorphic rocks are generally formed deep below the surface of the Earth. However, they are often found above the ground — even

high in mountain ranges. Explain how this can be so. 13 Limestone is a sedimentary rock. Describe the events that could occur to change limestone into another rock.

INVESTIGATE 14 Investigate the uses of marble and slate. Where are they obtained? What are they used for? Why are they expensive? eBook plus

15 Apply mainly heat or pressure to a series of rocks and watch them change with the Metamorphic rocks interactivity in your eBookPLUS. int-0234 16 Use the Rock cycle weblink in your eBookPLUS to watch an animation of how rocks undergo change. work sheet

19.5 The rock cycle

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19.6

Tracking changes in rock Layers of clues Sedimentary rocks form in layers. Each new layer forms on top of the older layers below. Sedimentary rocks are therefore useful for giving scientists clues about the order in which events have happened. Sudden events, like exploding volcanoes, are recorded in the layers. Slow movements beneath the surface can also be seen in the layers.

compare the ages of rocks all around the world. Sedimentary rocks that contain the same fossils have usually formed at about the same time.

knowing their age in years is called relative dating. Palaeontologists study fossils. A fossil is evidence of life in the past. Fossils can be used to

Living in the past The layers in rocks are useful for finding out about the order of events in a particular area. Finding out about the order of events, or comparing the ages of rocks without actually

Fossil of a reptile

7 These layers were deposited last. They have started to weather and erode. 6 A long period of weathering and erosion left the layer of limestone with a flat surface. When a volcano then erupted nearby, lava from the volcano cooled to form basalt on the flat surface. 5 A sudden event, like an earthquake, has occurred to break the layers of rocks like this. This event took place after the lower layers were folded. A break like this is called a fault. 4 A slow event has caused the lower levels to buckle. This is called folding. Folding can occur when rock layers are under pressure from both sides. 3 The third event to occur was the deposition of limestone. It tells us that there were probably marine organisms present in the area during this time. 2 This is the second layer deposited. Shale is a finegrained rock that is deposited in a quiet environment such as a swamp, lake or the slow-flowing part of a river.

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Mudstone

7

Conglomerate

Basalt

6

Limestone

5

3

Shale 2

4

Conglomerate 1

1 Conglomerate was deposited first in this rock sample. This layer was deposited by a glacier or an active environment — like a very fast flowing river.

How fossils form The remains of most animals and plants decay or are eaten by other organisms, leaving no trace behind. However, if the remains are buried in sediments before they disappear, they can be preserved, or fossilised. Fossils can take several forms. • The hard parts of plants and animals are more likely to be preserved than the softer parts. Wood, shells, bones and teeth can be replaced or chemically

A fatal fall . . . or was it murder? In 1991, some German hikers found a body preserved in ice near the Italy–Austria border. Scientists used radiometric dating and found that the body was about 5300 years old! They thought that the person, known now as the Iceman, had died of hypothermia (extreme cold). Ten years later, another group of scientists using hightech X-rays found the remains of an arrowhead lodged near his left lung. Specialists have not yet confirmed whether the Iceman fell back onto his arrow or if he was murdered. And without any witnesses to question, the truth may never be known!

changed by minerals dissolved in the water that seeps into them. Fossils formed in this way are the same shape as the original remains but are made of different chemicals; petrified wood is an example. Animal bones and shells can be preserved in sediments or rock for many years without changing. The types of bones, shells and other remains found in the layers of sedimentary rock provide clues about the environment, behaviour and diets of ancient animals. • Sometimes, fossils of whole organisms, including the soft parts, are preserved. Such fossils are rare and valuable. Insects that became trapped in the sap (called amber) of ancient trees have sometimes been wholly preserved. Similarly, if the remains of animals or plants are frozen and buried in ice, they can be fully preserved. Whole bodies of ancient woolly mammoths (including skin, hair and internal organs) have been found trapped in the ice of Siberia and Alaska. These

This insect was trapped in the sap of a tree millions of years ago.

remains provide clues to the way that living things have changed since ancient times. Whole bodies and preserved skulls of animals can even reveal evidence of their last meal before death. • The remains of animals or plants sometimes leave an impression, or imprint, in hardened sediments or newly formed rock. It is also possible for remains trapped in rock to be broken down by minerals in water, leaving a mould in the shape of the organism. • Some fossils, called trace fossils, provide only signs of the presence of animals or plants. For example, footprints preserved in rock can provide clues about ancient animals, including dinosaurs, and how they lived. By studying the shape, size and depth of footprints, hypotheses can be made about the size and weight of extinct animals as well as how they walked or ran. Plant, leaf and root imprints and feather impressions are other examples of trace fossils.

An ancient woolly mammoth. Whole bodies of these ancient animals have been discovered in the ice of Siberia and Alaska.

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◗ You have two records of the seashell — the mould or

INVESTIGATION 19.6 .

imprint in the sand and the plaster cast.

Making a fossil DISCUSSION

You will need: small seashell small box (shoebox or milk carton) fine sand plaster of Paris ◗ Half-fill the box with fine, damp sand. ◗ Make a clear imprint of a small seashell in the sand. ◗ Mix some plaster of Paris and pour it carefully into the

imprint. ◗ Once the plaster has set, remove the plaster cast carefully from the sand.

1

Which parts of animals are most likely to be preserved as casts?

2

Is the fossil of a fern leaf more likely to be found as a cast or a mould? Why?

3

Dinosaur fossils are found in casts and moulds. What evidence of dinosaurs is likely to be found as a mould?

CAUTION Do not put plaster of Paris down the sink.

5 Describe the clues that fossils provide about life in the past.

Activities REMEMBER 1 A road cutting reveals the layers of rock shown below. Identify which of the rocks in the cutting is: (a) the oldest rock (b) the youngest rock (c) evidence of volcanic activity (d) not a sedimentary rock.

6 Describe how whole ancient living things can be preserved as fossils. 7 Define the term ‘trace fossils’, and explain how they are useful. 8 Distinguish between a cast and a mould.

THINK Shale Sandstone Basalt Limestone

Mudstone Layers of rock exposed by a road cutting

2 Recall why some layers of sedimentary rock are tilted, even though the sediments that formed them were laid in horizontal beds. 3 Distinguish between the relative age of a rock and its actual age in years. 4 Recall what a palaeontologist studies.

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9 Identify which of the rocks shown at left would be most likely to contain the fossil of: (a) a seashell (b) the leaf of a fern usually found in swamps. 10 Explain why some layers shown at left are thicker than others. 11 Explain why the hard parts of plants and animals are more likely to be preserved than the softer parts. 12 Is an ancient Egyptian mummy found in a newly discovered tomb a fossil? Explain your answer. 13 Normally, older layers of rock are found below younger layers. Sometimes, however, younger layers are found beneath older layers. Deduce how this could happen.

14 Describe how fossil records can help us to link rocks from different parts of the world.

CREATE 15 Use plasticine to construct a sample of sedimentary rocks. Apply a gentle force to the sides of the layers. Describe how the layers fold under gentle pressure.

INVESTIGATE 16 Even an animal’s droppings can become fossilised. Use the internet or your library to investigate the following. (a) Which animal was responsible for a huge fossilised dropping found in Canada in 1998? (b) How long was the dropping? (c) What can palaeontologists find out from it? (d) Scientists give fossilised droppings a special name. What is it? eBook plus

17 Rate the rock formations in order from the oldest to the most recent with the Relative age of rocks interactivity in your eBookPLUS. int-0233 work sheet

19.6 Tracking changes in rock

19.7

PRESCRIBED FOCUS AREA Current issues, research and development

Human-made erosion Without weathering and erosion, the rocks that rise to the Earth’s surface would keep building up. Both weathering and erosion are natural processes. But what happens when humans disturb the natural process? Imagine a world where acid falls from the sky, a place where deserts replace fertile land and where the beaches are vanishing. These are some of the effects that humans have already had on the Earth.

Why save the trees? The roots of trees help to hold the soil together. Removing trees exposes good, fertile soil to wind and water. The soil is blown or washed away, leaving the land

Acid rain Every day many harmful chemicals are pumped into the air. Some are naturally formed chemicals, but many are from cars, factories or from other human activity. The chemicals in the air can dissolve in water, much like salt in hot water. The dissolved chemicals return to the ground in rainwater, snow or fog, and the combination is called acid rain. Acid rain can poison trees, soil and water supplies. It even eats away at rocks, including those used in buildings and statues.

destroyed. Early Australian settlers originally cut down trees to create farmland. As the population grew, more trees were cleared to provide space for industrial areas and housing. Since then, industrial areas have grown larger and the forests smaller. Trees are still being cleared for wood and wood products like paper (see photo above). Over the past 200 years, over two-thirds of Australian forests have been cleared.

Coasts under threat Coastal areas can be badly affected by erosion. Bare sand is easily washed away by water and blown inland by the wind. Vegetation egetation that binds the sand together has been torn up by recreational vehicles. Vegetation near beaches in tourist areas such as the Gold Coast has been removed and replaced with huge buildings. Barriers such as sea walls, mesh fences and groynes are built to hold sand on the beaches.

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INVESTIGATION 19.7

Rubber tubing

Tap

Why plant trees? Plastic lid

You will need: stream tray or box damp sand wooden block rubber tubing plastic lid from a soft-drink bottle several small twigs

Twigs

Moist sand

◗ Pack the sand into the tray. ◗ Make a groove in the sand to represent a

Wooden block

creek or river.

Creek

◗ Set up the equipment as shown in the

diagram at right.

Drain hole

Sink

◗ Make sure to ‘plant trees’ on one side

of the ‘creek’ only. ◗ Use the rubber tubing to aim water into

DISCUSSION

the lid.

1

Where does most of the erosion occur along the ‘creek’?

2

What effect do the ‘trees’ have on erosion?

◗ Allow water to flow slowly but steadily into the lid

and then overflow into the ‘creek’.

On the mend Scientists, conservation groups and government bodies play an important part in improving the environment. The aim is to reduce the impact of human activity and repair past damage. Some methods for reducing erosion and repairing the damage already caused by erosion include: • farmers ploughing their fields around hills rather than up and down the slope. This reduces the amount of soil washed down hills by rain. • sealing roads and gutters to direct water into proper drains • controlling numbers of livestock • replacing trees that have been removed • fencing off large sections of beaches and banning recreational vehicles in many coastal areas • reducing the impact of introduced animals, such as rabbits, on native vegetation.

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Activities REMEMBER 1 Define the term ‘acid rain’. 2 Give two reasons why forests have been cut down. 3 Explain how cutting down trees speeds up erosion. 4 Describe two ways that farmers can reduce erosion.

THINK 5 Explain why a barrier has been placed at the back of the beach in the photo on page 503. 6 The photograph at right shows an example of tunnel erosion. Suggest what has caused the erosion and how it may be stopped.

CREATE 7 Construct a flow chart to show how deforestation can occur. 8 Imagine you work for a local council in an area that has both national parks and coastlines. Your job is to educate people in the area about erosion and land care. Design and construct a leaflet that gives reasons for not using recreational vehicles in the area.

LOOKING BACK

4 Draw diagrams to explain the difference between weathering and erosion. 5 There is a lot of evidence that the Earth is changing. Volcanoes erupt, coastlines disappear, cracks appear in the ground, and fossils of seashells can be found on the top of some high mountains. In some cases, ancient cities have been found beneath the sea. Some of these changes are caused by natural events that change the Earth over millions of years; other natural events happen very quickly, in days, hours, minutes or even seconds. Unfortunately, not all of the events that change the surface of the Earth are natural. Some of them are caused by human interference with the environment. (a) Copy and complete the table below that lists some of the natural events that change the Earth. Work in a small group to add as many natural events to the table as you can. (b) Work in a group to construct a table like the one below that lists non-natural events that shape the Earth or might shape the Earth in the future. (c) For each of the events that you have included in your table for part (b), describe: (i) whether the changes made to the Earth’s surface would continue to have effects if humans were to suddenly be removed from the planet (ii) ways in which these events could be stopped.

Natural event

Conditions that cause the event

osion and er ring the

3 Often, when lava cools, the rocks formed near the edge of the lava flow have different-sized crystals from the rocks formed in the middle of the flow. (a) Describe where in the flow the rocks with the smallest crystals would form. (b) Propose a reason for this.

? re su es

ea W

2 Evaluate if the word in italics makes the statement true or false. If the statement is false, replace the word in italics to make it true. (a) Extrusive rocks form above the Earth’s surface. (b) The faster the cooling time, the larger the crystal size in igneous rocks. (c) Weathering is the process of moving broken down rock or soil from one place to another.

6 Fill in the blanks in the diagram below.

Hea t an dp r

1 Identify which of the following are extrusive igneous rocks and which are intrusive igneous rocks: scoria, basalt, granite, obsidian, pumice.

?

?

Igneous rock W ea

the

ring and erosion

?

?

7 Explain why acid rain eats away some types of stone used in buildings, but not others. 8 Deforestation is a worldwide problem. (a) Describe how deforestation speeds up the process of weathering and erosion. (b) Recall some measures that are being taken to reduce erosion and improve the environment. 9 The Grand Canyon in Arizona, shown below, has been forming over millions of years. It once formed the lower slopes of a mountain range that was twice as high as Mount Everest. Today, it is the largest gorge on Earth. The Colorado River flows in the bottom of the gorge.

(a) Describe how the gorge was probably formed. (b) State what types of rock would be found here and explain your answers. Likely effects on the Earth’s surface or crust

Likely effects on humans

Cyclone Earthquake Volcanic erruption Drought Tsunami Erosion

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10 Identify the following rocks based on their descriptions: (a) This rock is deposited in layers that are squashed together over long periods of time. It is most easily seen in road cuttings or cliff faces. (b) This rock is formed from limestone that has been heated and placed under great pressure. It is very hard but is able to be formed into sculptures. (c) This igneous rock is speckled in appearance due to its large crystals of feldspar, mica and quartz. (d) This dark, glassy rock is formed from the same material as basalt but has no crystals. (e) This is a pale rock that has a lot of holes in it. It can float on water and is used as an abrasive.

5 Describe the order of events that occurred to form these rock samples. (a)

Mudstone

Limestone

Sandstone

TEST YOURSELF

Mudstone

1 Rocks that have formed from cooled lava are described as A plutonic. B igneous. C metamorphic. D sedimentary. (1 mark)

(1 mark)

3 The lithosphere includes the A crust and the upper sections of the mantle. B crust only. C mantle only. D top layer of the crust only.

(1 mark)

Core Science | Stage 4 Complete course

(b) Mudstone Basalt

2 Fossils are most likely found in A granite. B basalt. C obsidian. D shale.

Conglomerate

4 The hardest mineral on Mohs’ scale of hardness is A talc. B quartz. C corundum. D diamond. (1 mark)

506

(3 marks)

Sandstone

Limestone

(3 marks) work sheets

19.7 The changing Earth puzzles 19.8 The changing Earth summary

STUDY CHECKLIST Rock composition

eBook plus

■ describe the lithosphere 19.1 ■ recall that all rocks are made up of minerals 19.1 ■ identify minerals based upon their hardness, lustre, colour and streak 19.1 ■ define the Mohs’ hardness scale

19.1

Types of rock ■ distinguish between extrusive and intrusive igneous rocks

ICT SUMMARY

Interactivities Metamorphic rocks Metamorphic rocks form when other rocks are placed under heat, pressure or both. The original rock that changes into metamorphic rock is called a parent rock. This interactivity enables you to apply heat or pressure to a series of rocks and watch them change.

19.2

■ explain the differences between igneous, sedimentary and metamorphic rocks

19.2, 19.4, 19.5

■ describe how metamorphic rocks are formed from sedimentary and igneous rocks

19.5

■ identify a variety of igneous, sedimentary and metamorphic rocks

19.2, 19.4, 19.5

■ recall how crystal size depends on cooling rate 19.2 ■ describe the rock cycle 19.5 ■ explain how rock layers reveal information about changes to the Earth

19.6

Weathering ■ define the terms ‘weathering’, ‘erosion’ and ‘sediment’

19.3

■ recall different ways that sediment may be deposited 19.3 ■ explain how acid rain affects rocks and human-made structures 19.7 ■ identify Australian examples of rock formations that have been created by erosion and weathering 19.3

Searchlight ID: int-0234 Relative age of rocks This interactivity tests your knowledge of how rocks are formed. Arrange a series of rock formations in order from the oldest to the most recent. Instant feedback is provided.

Current issues, research and development ■ describe the effect of deforestation on soil erosion 19.7 ■ describe methods that can be used to reduce soil erosion

19.7

Searchlight ID: int-0233

19 The changing Earth

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20

Student research project and skills

Scientists use investigations to solve problems; they design and carry out experiments. They keep records of the procedures used and the results obtained, and they draw conclusions from their findings. Very few scientists work in isolation. To make good progress in any field of science, scientists need to share reports on their work. In this chapter, you will learn about the work of scientists and the skills needed to design, carry out and report on a scientific investigation.

In this chapter, students will: 20.1 ◗ describe a problem and develop a

hypothesis to test 20.2 ◗ use a range of thinking tools to plan a

student research project 20.3 ◗ use a range of visual tools to develop

a timeline for a project 20.4 ◗ use a range of sources to gather

information and assess the reliability of this information 20.5 ◗ identify different types of variables,

describe a procedure for a simple controlled experiment, select appropriate equipment and evaluate data for reliability and validity 20.6 ◗ organise data and display it using the

appropriate graph 20.7 ◗ organise data using spreadsheets 20.8 ◗ organise data using databases 20.9 ◗ draw conclusions from experimental

results, write a project report and acknowledge sources of information appropriately.

Scientists use a wide variety of equipment to make accurate measurements.

Researching the CsIRO Use the CSIRO weblink eBook plus in your eBookPLUS to answer the following questions. 1. What is the CSIRO? 2. The CSIRO s website describes some of the research done

INVESTIGATION 20.1

◗ If you are using thermometers,

record the temperature of the coffee in both cups every 30 seconds.

milk now or later? You have just finished making yourself a cup of coffee when the phone rings. So that your coffee is as warm as possible, should you add the milk to your coffee now or after you have finished talking on the phone? Does your answer depend on the length of the phone call? You will need: kettle 2 identical cups instant coffee milk 2 thermometers or a data logger with 2 temperature probes 2 measuring cylinders ◗ Your teacher will assign a particular

phone call time to each group of students. ◗ Heat some water in a kettle and

use it to make two cups of instant coffee. Make sure you use the same type of cup, the same amount of hot water and the same amount of coffee powder. ◗ Put a thermometer or temperature

probe in each cup of coffee. If you are using a data logger, set it to collect results for at least 10 minutes. ◗ Measure 40 mL of milk in each of

two measuring cylinders. ◗ Add 40 mL of milk to one of the

cups.

other two students the area of research they have just read about. Try doing this without referring to your notes.

by CSIRO scientists. Read the information provided for one area of research that the CSIRO is involved with and summarise this research in point form. 3. Form groups of three. Each student should explain to the

◗ After your phone call time has

passed, add the milk to the second cup. ◗ Continue measuring the

temperature in both cups every 30 seconds until 10 minutes has passed since you added the milk to the first cup. ◗ If you used thermometers, record

your results in a table like the one below. Temperature ( C) Time (minutes)

Milk added at time 0

Milk added after phone call

A data logger can be used for this experiment.

DIsCUssIOn 1

Does hot coffee cool faster than warm coffee? How can you tell from your graph?

2

Did the two lines on the graph cross at any stage? What does this indicate?

3

Write a conclusion based on your results.

4

Does the length of the phone call affect the results? Compare your graph with those of other groups.

5

Why was it important to put exactly the same amount of water in both cups and to use the same type of cup?

6

What are the advantages and disadvantages of using a data logger for this experiment?

7

How could this experiment be improved? Explain your answer.

0 0.5 1 1.5 ◗ Plot line graphs of your results on

the same set of axes. Put time on the horizontal axis and temperature on the vertical axis. ◗ If you used a data logger, a graph is

plotted automatically. If necessary, adjust the settings so that the graph shows the temperatures measured by both probes on the same set of axes. Put the graph into the results section of your experiment report or into your workbook.

20.1

Choosing a problem Choosing a problem to investigate can be the hardest part of a student research project (SRP). Ideally, the problem should relate to something you are interested in. You need to make sure that you can write a hypothesis for the problem you choose and that it can be tested by carrying out a scientific experiment.

What s the problem? The problem you choose to investigate should relate to science. It should be written as a question, and it should be something you do not already know the answer to; the problem should challenge you. On the other hand, you also need to make sure your challenge is achievable with the resources available at school. Some examples of problems suitable for a Year 8 student to investigate are shown at right. Some problems can be answered by doing just one experiment. Other problems are more complex and have many parts. To solve such problems, you may need to design and carry out a number of experiments. For example, if you are trying to find out what type of parachute will slow down a toy s fall most effectively, you may do an experiment to investigate the ideal material to use for the parachute, a second experiment to test the design of the parachute and a third to test the ideal size of the parachute.

The aim of the game Each of the experiments you do to solve your problem should have an aim. The aim of the experiment is the reason for doing the experiment. It is often more specific than the problem you are investigating and it should start with the word to. Below are some examples of aims for experiments. • To find out which flower colour makes the best acid base indicator • To find out if the size of the sheet of paper used to make a paper aeroplane affects how far the plane will fly • To compare the speed of balloon rockets gliding along fishing line with that of balloon rockets gliding along string • To compare the cooling rate of test tubes wrapped in different types of fabric

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Possible student research project topics • Does the thickness of a rubber band affect how far it

• • • • • • • • • • • • • • • • • • • • •

•

stretches? Do other features of rubber bands affect how far they stretch? What type of paper aeroplane flies furthest? What type of parachute slows a toy s fall best? Which plants make good acid base indicators? What type of balloon rocket travels fastest? What is the best recipe for soap bubble mixture? Do tall people jump higher and further than short people? Does the amount of exercise you do affect your heart rate? In what way? What type of fabric keeps you warmest in winter? How do fertilisers affect the growth of plants? Does talking to plants improve their growth? Can plants grow without soil? What makes algae grow in an aquarium? What is the best shape for a boomerang? What type of wood gives off the most heat while burning? What makes iron rust? Which paint weathers best? Which battery lasts longest? Which type of glue is best? Which food wrap keeps food fresher? Which fabrics burn faster? How can the growth of mould on fruit be slowed down? Which concrete mixture is strongest?

Which parachute will slow the toy s fall more? Is the test fair?

What is your hypothesis? A hypothesis is a sensible guess about the outcome of an experiment. It should relate to the aim and should be able to be tested with an experiment. The results of the experiment will either support (agree with) the hypothesis or not support (disagree with) the hypothesis. It is not possible to conclusively prove that a hypothesis is correct. When scientists make a hypothesis, they usually do a number of experiments to test that hypothesis. Sometimes, a number of teams of scientists test the same hypothesis with slightly different experiments. Even if the results of each experiment agree with the hypothesis, the scientists could never say that the hypothesis is proven to be correct. They would say that each experiment has provided further evidence to support the hypothesis.

Use your own observations Your hypothesis should be based on observations you have made. It might also be based on your own reading. For example, if you are trying to design the best parachute for a toy, you should read about

Stool Sticky tape

Drinking straw

parachutes before writing your hypothesis. You might find out that light, closely woven fabric that does not increase in weight too much when wet makes better parachutes than heavy fabric that soaks up a lot of water. When walking home in the rain, you might observe that your cotton T-shirt soaks up a lot of water and becomes heavy, whereas your nylon jacket does not soak up water. As a result, your hypothesis might be: Closely woven nylon is a better fabric to use for a parachute than loosely woven cotton.

Fine-tuning your hypothesis A statement that cannot be tested with a scientific experiment is not a suitable hypothesis. The statement People born in January are more conscientious than others is not a good hypothesis unless you can find a reliable way to measure conscientiousness. The statement People born in January work more hours than others is a better hypothesis because the number of hours worked is something that can be measured. Similarly, the statement Watching television makes you fat would be difficult to test scientifically; however, the statement Children who watch more than two hours of television

each day are more likely to be overweight than children who watch less than two hours could be tested scientifically. Aeroplanes made from cardboard fly better than those made from paper is not a suitable hypothesis because fly better has not been defined so cannot be tested scientifically. Fly better could mean fly further, fly in a straighter line or stay in the air longer. A better hypothesis would be Aeroplanes made from cardboard fly further than those made from paper.

hypotheses and predictions Hypotheses and predictions are not the same thing. A hypothesis is a more general statement. Purple flowers make good acid base indicators is a hypothesis; it is a general statement about all purple flowers. However, a hypothesis can be used to make a prediction. Purple impatiens will make a good acid base indicator is a prediction. It is a specific statement about one particular type of flower. The table on the next page shows how problems and observations can lead to hypotheses and predictions, with possible results from testing these.

Stool Fishing line

Air Balloon Does a balloon rocket glide faster along a fishing line or a string? Which plane will fly further?

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Problem

Observation

Hypothesis

The television remote doesn t work.

If I press the on button The batteries in the on the remote, the remote control are flat. television won t come on.

My hair is sometimes dry and frizzy. No parrots come to our bird feeder.

Test results The remote still doesn t work.

My hair is driest soon after washing it with Mum s shampoo.

Mum s shampoo dries out If I use a different my hair. shampoo, my hair won t dry out.

My new shampoo does not dry out my hair. Problem solved!

There is bread in the bird feeder, and magpies and miners feed there.

Parrots prefer seeds. I ll try wheat seeds.

Parrots were not attracted to the feeder.

Activities REmEmBER 1 Copy and complete the following statements using these words: aim, to, hypothesis, problem, predictions, support, observations, prove, tested. (a) An aim always starts with the word _____________. (b) A ________________ is usually worded as a question to answer. (c) The results of an experiment can ___________ a hypothesis but they never ____________ that the hypothesis is correct. (d) A __________________ is an educated guess about the outcome of an experiment. (e) The ______________ of an experiment is the purpose of the experiment. (f) A hypothesis can be ____________ by carrying out a scientific experiment. (g) We can use a hypothesis to make _________________. (h) A good hypothesis is based on _______________ and often also on research. 2 Distinguish between the terms hypothesis and prediction .

ThInk 3 Classify each of the statements below as an aim, a hypothesis, an observation or a prediction: (a) Substances dissolve faster in hot water than in cold water. (b) At 80 C, it will take 30 seconds for one teaspoon of sugar to dissolve in a cup of water. (c) At 70 C, it took 40 seconds for one teaspoon of sugar to dissolve in one cup of water. Problem The dog won t eat its dinner.

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Prediction If I change the batteries, the remote will work.

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Parrots will come if I fill the feeder with wheat seeds.

(d) To find out if sugar dissolves faster in hot or cold water. (e) It will be windy tomorrow. (f) A red sunset is always followed by a windy day. (g) The wind speed is 5 km/h. (h) To find out if there is a relationship between the colour of the sky at sunset and the top wind speed on the following day 4 Is each of the following statements a suitable hypothesis? If not, justify your answer. (a) White chocolate tastes better than dark chocolate. (b) Washing powder X removes tomato sauce stains faster than washing powder Y. (c) Plants grow faster under red light than under green light. (d) Sagittarians are nicer people than Leos. (e) Playing video games increases the muscle strength in your thumbs. (f) Playing video games affects the development of social skills. (g) Science teachers are more interesting people than English teachers. (h) Science teachers perform better in IQ tests than English teachers. 5 Consider the table above. Construct alternative hypotheses for the problems where the test results did not support the original hypothesis. 6 Consider the information given in the table below. In groups of three, discuss the information and create two possible hypotheses that explain the observations listed. Make predictions about the possible outcomes of testing based on each of your hypotheses. work sheet

20.1 Starting an investigation

Observations • The dog has not eaten dinner for three days in a row. • The side fence has a hole in it. • There has been a recent change to the brand of dog food served. • The neighbours have a new puppy.

Hypotheses

Predictions

20.2

Thinking about your problem Much of a scientist s work involves thinking about problems and trying to come up with solutions. Sometimes ideas seem to pop into your head when you least expect it, such as when you are out walking the dog. In some instances though, thinking needs to be an organised process. The thinking tools described on the next few pages will help you make a start on your student research project.

Looking from all sides: PmI PMI stands for plus, minus, interesting. A PMI is a thinking tool that encourages you to look at an idea from a number of perspectives before making a decision. Use the following steps to construct a PMI on a particular topic. 1. Write your topic or problem at the top of the page. 2. Draw three columns underneath the topic. 3. Fill in the three columns with good things and bad things about the topic or problem and things you find interesting but are neither good nor bad. Imagine that a student was thinking of choosing the following problem for their student research project Do guinea pigs eat more food when the weather is cold? The example below shows a PMI that the student used to decide whether to choose that particular problem for her project.

how ideas overlap: venn diagrams Venn diagrams are often used in mathematics, but they can be useful to scientists as well to show the common points between different ideas or concepts. Use the following steps to draw a Venn diagram for two topics. 1. Draw two overlapping circles with the topic written above each circle. 2. In each circle, write down ideas that relate to each topic. 3. Write ideas that relate to both topics in the overlapping section. Below is a Venn diagram that shows some of the similarities and differences between respiration and photosynthesis. Photosythesis

sæ/CCURSæONLYæIN æ PLANTS sæ2ELEASESæOXYGEN sæ0RODUCESæSUGARS sæ2EQUIRESæLIGHT sæ4AKESæINæENERGY

Choosing the following problem for my SRP: Do guinea pigs eat more food when the weather is cold? Plus • I have four guinea pigs at home so I don t need to buy guinea pigs. • I know a lot about guinea pigs and I enjoy looking after them.

Minus • I don’t want to make my guinea pigs uncomfortable or sick by exposing them to extreme temperatures. • Four guinea pigs may not be enough to provide reliable data, and my mum will not let me buy more guinea pigs. • My Science teacher may not approve an SRP that involves animals.

Respiration

sæ#HEMICALæREACTION æ THATæOCCURSæINæLIVING æ THINGS sæ&ASTERæATæHIGHER æ TEMPERATURES sæ2ELEASESæGAS

sæ/CCURSæINæALL æ LIVINGæTHINGS sæ2ELEASESæENERGY sæ0RODUCESæCARBON æ DIOXIDEæANDæWATER

A Venn diagram

Interesting • How will I measure how much food the guinea pigs have eaten? • I may need a food dish that the guinea pigs cannot tip over.

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mapping your thinking

Identifying similarities: double bubble maps

Once you have selected a problem, a bubble map, cluster map or mind map can help you organise your thoughts. These three thinking tools have many similarities and some key differences.

Like Venn diagrams, double bubble maps can be used to show things that are common to two different topics. Use the following steps to construct a double bubble map. 1. Create separate single bubble maps for the two topics that you are comparing. 2. Identify the characteristics that are the same or similar. 3. Redraw to create a double bubble map by placing the similar bubbles in the middle. The example at the bottom of the page shows a double bubble map for two important environmental issues: thinning of the ozone layer and global warming.

Identifying key ideas: single bubble maps A single bubble map is the simplest way to map your thinking. Use the following steps to construct a bubble map on a particular topic. 1. Write your topic in the middle of the page. 2. Around the topic, write down any ideas that relate to your topic and join these ideas to your topic using lines. In the example below, a student created a single bubble map to organise her thinking about the problem she chose for her SRP Which features of rubber bands affect how far they stretch?

Thickness Exposure to UV light

Type CTyof rubber Features of rubber bands that may affect how far they stretch

Age of or Covered rubber band uncovered

Covered or uncovered Length of rubber band

stimulating ideas: cluster maps A cluster map starts in the same way as a bubble map, but each of the bubbles around the central topic can itself have other ideas linked to it. Use the following steps to construct a cluster map. 1. Think of a topic and write it in the middle of a sheet of paper. 2. Around your topic, write down any ideas that link with it. Draw lines from the ideas to your topic. 3. Write down new ideas that are related to your first ideas, and link them with lines. The cluster map on the opposite page was created by a student who chose the following problem for her SRP Which parachute design will slow down a toy s fall most effectively?

Single bubble map

Pollution of the atmosphere

Will lead to rising ocean levels

Main gases responsible are carbon dioxide and methane

Global warming

Linked to burning of fossil fuels

Double bubble map

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Environmental problem

Caused by gases

Main gases responsible are CFCs

Thinning of the ozone layer

Will lead to more cases of skin cancer

Size

Cotton

Shape

Nylon Canopy

Type of thread

Closeness of weave

Number of strings

Fabric

Parachute design

Strings

Length of strings

Material used for strings

Thickness A cluster map

Exploring and summarising ideas: mind maps

re he W

W ea th er

Garden

A mind map is similar to a cluster map but it also has the relationship between the ideas written on the lines An example of a mind map is shown below. It was that join them. Creating a mind map for a particular used by a student to revise the plant growth topic. A topic is a great way of revising that topic to prepare mind map could also help you plan your SRP. for an examination. Use the following steps to construct a Water Fertiliser Shade mind map. 1. Write your topic in the Humidity Rain middle of a sheet of paper and draw a number of lines Type of potting mix branching out from it. Temperature Hail 2. Think of some main ideas related to the topic and Insects Pot Water write one on each branch. 3. Draw a number of lines Rats branching from each of your main ideas. Fertiliser Vertebrate Pests Plant 4. Think of words or terms Size of the pot growth related to one of your main ideas and write one on Possums each branch. 5. Continue adding branches Slow growing until you run out of ideas. Snails 6. You can decorate your map with colour, clip art, Fast growing drawings, photos, etc. to Bacteria Viruses Fungi make the ideas and links clearer. A mind map it s

Diseases

g tin lan tp ea Ag

Ty pe of pla nt

ed nt pla

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Linking ideas: concept maps A concept map is similar to a mind map in that they both show the relationship between ideas in a topic. However, a concept map also explains the relationship between elements, with statements written on the links. Use the following steps to draw concept map. 1. Write down all the ideas you can think of about a particular topic. 2. Select the most important ideas and arrange them under your topic heading. Link these main ideas to your topic and write the relationship along the link. 3. Choose ideas related to your main ideas and arrange them in order of importance under your main ideas, adding links and relationships. 4. When you have placed all of your ideas, try to find links between the branches and write in the relationships. An example of a concept map is shown above right. It illustrates some of the important ideas and links associated with electric circuits.

Electric circuits

has a

voltage

need a

can be

power supply

closed circuits

to allow

used to

provided by

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open circuits

switch electric current battery

can break

follows flows through

provides

load

energy

conducting path like a

filament in a

is converted in a

torch

A concept map

Scientific investigation Hypothesis

Observation

Educated guess

Not certain

Prediction

Sensible

sorting ideas into groups: affinity diagrams An affinity diagram helps you to group common ideas or viewpoints. Use the following steps to construct an affinity diagram on a particular topic. 1. Think about a topic and write any ideas you have onto small pieces of paper. 2. Examine your pieces of paper and put similar ideas into groups. Feel free to rearrange your groups until you are happy with them. 3. Think of names for your groups. An example of an affinity diagram is shown at right. Each category name represents an important part of scientific investigations.

or

Seeing

Tasting

Hearing

Feeling

Smelling

Noticing

Measurement

Conclusion

Balance

Ruler

Outcome

Findings

Thermometer

Stopwatch

Final

Fairly certain

An affinity diagram

The cause of it all: fishbone diagrams A fishbone diagram is particularly useful if you are trying to establish the cause of an event. Use the following steps to construct a fishbone diagram on a particular event. 1. Think of an event that you do not know the causes of.

2. In pairs or a team of four, organise your list of causes into groups. 3. Write the event that you are analysing as the fish s head of a fishbone diagram. Your groups of causes then become the main bones of the diagram, one bone for each group.

4. Write the title of each of your groups of causes on its relevant fishbone. 5. Write the causes on the smaller fishbones that are joined to the sides of the main bones.

(You can attach causes to more than one bone or group of causes.) Charlotte constructed the fishbone diagram below for her SRP problem How can I keep

The water in the vase is missing something the plant needs to survive.

Cutting the plant damages the stem.

Activities REmEmBER

The salt concentration is too low. The conducting tissue of the plant is damaged when the stem is cut.

cut flowers looking fresh for the longest possible time? In her fishbone diagram, she has considered the reasons why flowers die rapidly after they have been cut from a plant.

The plant loses sap where the stem is cut (just as humans lose blood) so it dies.

Flowers die rapidly after being cut from a plant.

Plants need roots to survive.

A fishbone diagram

Thinking with different hats There are a number of very useful tools that can help develop your thinking. One of these was created by a great thinker by the name of Edward de Bono. He developed the idea of using different coloured thinking hats for different types of thinking. These hats don t even have to be on your head. The idea behind each hat just needs to be in your head.

The following example shows how your thinking hats can be used to discuss whether expensive space exploration should continue.

Problem: Spending billions of dollars on space exploration Red hat: How do you feel about all the money spent on exploring space? Yellow hat: How do we benefit from space exploration? Black hat: What s wrong with spending billions on space exploration? White hat: What information do we need? Green hat: What other things could we spend the money on? Blue hat: What can be gained from space exploration in the future?

1 What does PMI stand for? 2 Identify a type of diagram that consists of two overlapping circles. 3 Distinguish between bubble maps, cluster maps and mind maps. 4 Compare Venn diagrams with double bubble maps.

ThInk 5 Construct a PMI for each of the following ideas. (a) School students should not wear a uniform. (b) School canteens should sell only healthy food. (c) Parents should be fined if their children are sunburned. (d) The legal driving age should be changed to 21. (e) All high-school students should be given a free computer paid for by the government. 6 Construct a Venn diagram with one circle labelled Plants and the other Animals and complete using features of plants and animals. (Hint: See chapters 4 and 5.) 7 (a) Construct a bubble map for the topic The solar system . (Hint: See chapter 8.) (b) Add additional bubbles to change your bubble map into a cluster map. 8 Choose one of the topics you studied in science this year and, working in groups of three to four students, construct a mind map for that topic.

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20.3

Organising your thinking Timelines and gantt charts

think about all the tasks required and construct a timeline or Gant chart that shows when you need to have completed each task. This will help you complete your project on time without having to rush any part of the project.

Constructing a timeline 1. Draw a line to represent the total amount of time available; for example, if you have 6 weeks to work on your project, you might draw a 12 cm line. 2. Divide the line evenly to represent blocks of time; for example, 2 cm might represent 1 week. 3. Indicate on the timeline when you plan to have completed particular tasks.

When you are set a large complex task such as your SRP, it is important to plan how you will use the time you have available. Leaving all the work until the last few days before the due date is unlikely to result in a high-quality project report. Depending on the problem you have chosen to investigate, you might need to allow time for plants to grow or for results to be collected over a period of time. Writing the final report, taking photographs and constructing tables and graphs of your results also take time. Before you start on your Spreadsheet software can be used to draw Gantt charts. project, you should

1 Mar.

8 Mar.

A student s SRP timeline

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15 Mar.

22 Mar.

A Gantt chart is another way of planning your time. It can show more clearly that some tasks will be done over an extended period of time. If you have access to a computer, a Gantt chart can be drawn easily using Microsoft Excel or another spreadsheet program. 1. Draw a table with each column representing a particular block of time, such as a week. 2. List the tasks to be completed in the first column of the table. Each task should take up one row of the table. 3. Shade the cells of the table that represent the time when you plan to work on that particular task. An example of a Gantt chart for a student SRP is shown below.

Experiments completed 29 Mar.

}

Project handed out

}

Decide on problem.

Library research

Constructing a gantt chart

Plan due

Do experiment.

Work on report.

}

Diagrams can help us to organise our thinking and also to organise our time when planning a complex project. Storyboards, timelines, Gantt charts, cycle maps and flow charts are tools used to represent complex scientific processes, plan presentations and help you manage your time as you work on your SRP.

5 Apr.

Results entered in spreadsheet

12 Apr.

Due date

Using storyboards to plan your work A storyboard is similar to a comic strip. It is a series of diagrams that might be used to plan a PowerPoint presentation, movie or project. If you are planning a movie, each diagram might represent an outline of a scene in the movie. For a PowerPoint presentation, each diagram could represent one slide of the presentation. Your teacher might give you the option of presenting your SRP to your class using a short movie or PowerPoint presentation. A storyboard would be an excellent tool to plan such a presentation.

going with the flow: flow charts and cycle maps Flow charts and cycle maps are representations of particular processes. The method for an experiment can usually be represented by a flow chart. A cycle map is similar to a flow chart, but it forms a closed cycle so it is useful to represent processes that repeat themselves, such as the water cycle or the life cycle of an organism. To draw a flow chart or cycle map, write each step or event and link them with arrows. Collect

A

B Assess Outline of scene 1

Examine

Outline of scene 2

Perform

Agree

D

C

A cycle map for a team meeting Outline of scene 3

Flower formation

Outline of scene 4 Growth

Pollination

E

Outline of scene 5

Outline of scene 6

Fruit and seed formation

Germination Seed dispersal

General plan for a storyboard

A cycle map showing the life cycle of a flowering plant

Storyboard for a movie presentation of a student SRP

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The problem Our new puppy keeps barking and whining each night when we put him outside.

Test I ll place a ticking clock under the puppys bedding. I will try this method for three nights.

Hypothesis The puppy is scared of the dark.

Results The puppy barked and whined for the first hour each night.

Test I ll place a small lamp near the puppys bed. I will try this method for three nights.

Think again The results don t agree with my hypothesis. I need a new hypothesis.

Check hypothesis My hypothesis has been generally supported, but not fully supported.

Think again Modify my hypothesis and test again.

Results The puppy keeps barking and whining most of the night.

Check hypothesis My hypothesis has not been supported. Providing light for the puppy has had no effect at all.

Test I ll place a ticking clock and hot-water bottle under the puppys bedding. I will try this method for three nights.

Hypothesis The puppy misses the noise of its mother and brothers and sisters.

Results The puppy barked and whined for 15 minutes on the first night, 5 minutes on the second night and not at all on the third night.

Check hypothesis My results agree with my hypothesis. Peace at last

Hypothesis The puppy misses the noise and warmth of its mother and brothers and sisters.

A flow chart of the process used to stop a puppy barking at night

Activities REmEmBER 1 Recall two similarities and two differences between a timeline and a Gantt chart. 2 Identify a visual tool that looks like a cartoon strip. 3 Compare cycle maps with flow charts.

ThInk 4 Interpret the flow chart above to answer the following questions. (a) What was the problem to be solved? (b) What action was taken when the first and second hypotheses were not supported? (c) What variable was used in each of the three experiments? (d) Do you think each experiment was a fair test? Explain.

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(e) What other explanations could there be for the change in the behaviour of the puppy in the final experiment? 5 Identify the visual tool that you would use to show each of the following. (a) When various groups of animals first appeared on Earth (b) The procedure used to extract DNA from cells (c) The life cycle of a butterfly (d) The date on which each of your assignments is due this term (e) An outline of the video you would like to make for your cousin s sixteenth birthday 6 Construct a timeline that shows some of the key events that have occurred in your life so far. 7 Construct a Gantt chart that shows which subject you plan to work on each night of this week. 8 Construct a flow chart that shows how to make slime using the following recipe.

Combine 20 mL PVA glue, 20 mL water and 3 drops of food colouring and stir. Prepare a saturated solution of borax. Use a syringe to measure 20 mL borax solution and add it to the glue mixture. Stir vigorously until the slime forms. Rinse the slime with water before playing with it. 9 Construct a cycle map for the water cycle (Hint: See page 177 in chapter 7.)

20.4

Research and record keeping Scientists do experiments to test hypotheses, which are based on observations as well as knowledge previously discovered by other scientists. An important part of the job of scientists is to read reports written by other scientists and to do background research before designing their experiments. Scientists also need to keep records of all their observations and any changes they make to the design of their experiments. When you do a student research project, you will probably be asked to do this by keeping a logbook.

What is a logbook? A logbook is a document where you keep a record of all the work you do towards a project. Each entry should be dated like a diary. In your logbook, you might include the following items. • A timeline or other evidence of planning your use of

Part of a blog site used by a researcher to share the results of her investigations into acid base indicators

time • Notes about conversations you have had with

•

• • • • •

teachers, friends, parents or experts on your project and how these conversations affected your project. Make sure you record each person s details so you can acknowledge their contribution in your report. Notes from library research you have done for your project. Include all the details you will need for your bibliography. A plan or rough outline of the method you will use for your experiment(s) Notes about any problems you encountered during your project and how you dealt with these Information on any changes you made to your original plan Results of all your experiments (these may be presented roughly at this stage) A plan or storyboard for your presentation if you are required to present your research to your class.

A logbook can be written by hand on paper, it can be done with a wordprocessing program on a computer or even be in the form of a website. A blog is a website that has dated entries so it can be used as a logbook. It has the added advantage that you can invite other people, such as your friends, parents and teachers, to look at your work and post comments. You should check with your teacher on the format required for your logbook.

Researching your topic Before you start your own experiments, you should find out more about your topic. As well as increasing your general knowledge of the topic, you need to find out whether your problem has been investigated by others. Information already available about your topic might help you to design your experiments. It might also help you in explaining your results. Make notes on your topic as you find information. You may be able to include some relevant background information in your report.

Using the library The best place to start is the school library. There are several different types of information sources in the library. They usually include the following.

Nonfiction books Use the subject index catalogue to find out where to find books with information about your topic. Your library catalogue is most likely to be stored in a computer database. You might need to ask the librarian to help you use the catalogue at first. It is also a good idea to browse through the contents list of science textbooks. Your topic may appear.

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Reference books

Industry

These include encyclopedias, atlases and yearbooks. The index of a good encyclopedia is a great place to start looking for information.

Information on some topics can be obtained from certain industries. For example, if you were testing glues for strength, or batteries to find which ones last longest, the manufacturers might have useful information. Use the yellow or white pages of the phone book to find addresses and send a polite letter or email.

Journals and magazines There are quite a few scientific journals that are suitable for use by school students. New Scientist, Ecos, Australasian Science, Popular Science, Choice, Helix and Scientriffic are available in many school libraries. They provide up-to-date information, but flicking through journals is a very slow way to find a relevant article. Instead, you might try using a journal index, such as EBSCO. Ask your school librarian which journal is available at your school.

Information files Many school libraries keep information files (also called vertical files) of newspaper articles on topics of interest or even collections of articles on CD-ROM. Ask your school librarian if you don t know how to use these resources.

Audiovisual resources When you use the library catalogue to look for resources, you may discover that your school has a relevant DVD you can borrow or a digital video you can watch. If your school subscribes to digital video library software, you may be able to search for relevant video resources at your school.

Relatives or friends Perhaps you or a relative know somebody who works in your area of interest. Let your friends and relatives know about your intended research. They might be able to put you in contact with people who are experts in the area you are researching. Perhaps they can obtain information that is relevant to your project from their workplace. For example, if your project involves plants and a family member or friend works in a plant nursery, they might be able to give you expert information on the best ways to grow your plants. This could help avoid some preliminary experiments that you would otherwise need to perfect your techniques. In some instances, it may be possible for you to obtain some of the resources you need for your experiment from friends and relatives as well. For example, if your project involved comparing the effectiveness of different types of ear muffs, these might be able to be borrowed over the weekend from a friend s workplace.

Beyond the library Information on your topic may be available from the following sources.

Your science teacher This may seem obvious, but many people don t even think to ask. Your science teacher may also be able to direct you to other sources of information.

Government departments and agencies Federal, state and local government departments and agencies may be able to provide you with information or advice on your topic. Try searching through the government listing at the front of the white pages of the phone book. Addresses to write to are usually listed. A polite letter or email to the appropriate department or agency is the best way to ask for help.

The internet The internet provides a wealth of information on almost any topic imaginable. The trick is to use the right search words. Search engines such as Google, Yahoo!, AltaVista and Ask.com will help you find the information you need.

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Use a variety of information sources when looking for background information for your project.

In your logbook complete a checklist like the one on the next page to see if you have thoroughly searched sources of information.

how to use information

Checklist of information sources School library:

• nonfiction books • reference books • journals and magazines • information file • audiovisual resources

Beyond the library:

• your science teacher • government departments and agencies • the internet • industry • relatives or friends • other sources

Activities REmEmBER 1 Outline why a logbook is a bit like a diary.

■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■

Make notes on information that is relevant to your research topic. Think about what you really need to know. You need information that will help you to: • plan your experiments • understand your results later on • show in your report how your research relates to everyday life or why your research is important. You will need to keep an accurate list in your logbook of the steps you have taken and the resources that you have used.

(a) Explain what an online catalogue is. (b) Distinguish between online catalogues and search engines such as Google. (c) It is usually better to start a search using the library online catalogue rather than an internet search engine. Explain why.

2 Define the term blog . 3 An easy way to find information about a topic is to use a search engine. Outline how you might find information about your topic in your school library without using a computer.

eBook plus

6 You can find information about science topics in science textbooks and on the internet. (a) Explain why you would not find the results of scientific research that was done last month in a science textbook. (b) assess the advantages of using science textbooks as a source of information. (c) assess the advantages of using the internet as a source of information.

8 Use the Wikipedia weblink in your eBookPLUS to answer the following questions about Wikipedia, an online encyclopedia. (a) When did Wikipedia start? (b) Who founded Wikipedia? (c) How is Wikipedia different from other online encyclopedias such as World Book Online and Encarta Online? (d) Some of the information in Wikipedia is not reliable. Explain what reliable means and why that might be the case for Wikipedia. (e) How could you assess whether a particular piece of information you found on Wikipedia was reliable? (f) Outline some reasons why people may wish to put inaccurate information on Wikipedia. (g) Discuss whether certain people should be banned from contributing to Wikipedia. Give reasons for your answer. (h) Which Wikipedia entries are most likely to be highly reliable, those that have been edited many times by a large number of people or those that have been written by only one person and never edited. Explain your answer.

7 Your school and local library probably have an online catalogue.

9 Use the Wiki weblink in your eBookPLUS to have a go at writing a class wiki on a topic of your choice.

4 Define the following terms. (a) Vertical file (b) Journal (c) Search engine (d) Encyclopedia (e) Nonfiction

ThInk 5 Imagine you are scientist. assess the advantages and disadvantages of maintaining a blog rather than keeping a logbook in your office.

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20.5

Designing your method Your student research project will include one or more experiments. Each experiment must be carefully planned to ensure that the results are valid, reliable and accurate. Designing a scientific investigation usually begins by considering the variables involved in the experiment. You should also think about the observations and measurements that you will need to make. Most importantly, your experiment must be safe and minimise risk to yourself and others.

variables Variables are the conditions that can be changed in an experiment. In chapter 1 (see pages 25 6), you learned that there are different types of variables in experiments. The example below will help you revise this. Problem: Do black cars heat up in the sun faster than white cars? Type of variable

Definition

Independent

The variable that is deliberately changed in the experiment

Dependent

The variable that is Temperature measured in the experiment

Controlled

Variable that must be kept constant to ensure that the experiment is fair

Which car will heat up faster on a hot day?

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Colour of car

• • • • •

Location of car (both cars in full sun) Outside temperature Type of car Window tinting Location of thermometer in car

valid experiments A valid experiment tests what it is designed to test. For example, if you want to measure a student s intelligence, getting the student to complete an IQ test would be a more valid test of her intelligence than measuring how high she can jump. Imagine that a student wants to find out if washing powder X cleans better than washing powder Y. A valid test might involve staining two pieces of the same type of fabric with the same amount of engine oil and washing these in the same way. After washing, the amount of grease left on each piece of fabric could be compared. On the other hand, asking people to compare the smell of the two washing powders would not be a valid way of testing which powder washes clothes better. Using washing powder X to wash cotton stained with tomato sauce and using washing powder Y to wash wool stained with engine grease would not be a valid test either. In a valid experiment, only one variable (the independent variable) is changed. The other variables are controlled (kept the same) as far as possible. A control is usually needed in experiments that test whether a particular variable has an effect. A control allows the scientists to compare the results with and without changing the variable. For example, if you want to test whether a fertiliser makes a plant grow faster, you would need to grow two plants under identical conditions and apply the fertiliser

to only one of the plants. By comparing how quickly both plants grew, you could decide whether the fertiliser has an effect.

The placebo effect When scientists test the effectiveness of medicines and other medical treatments, they need to take into account the placebo effect. A placebo looks and tastes identical to the real medicine but does not contain any of the active ingredients found in the medicine, so it should not have an effect on patients. Many studies have shown that patients given a placebo report improvements in their condition. To allow for the placebo effect, scientists usually test new drugs by giving half the patients the real medicine and the other half (the control group) a placebo. The patients are usually not told whether they are taking the placebo or the real medicine. This is called a blind study. In addition, in a double-blind study, the nurses and doctors who deal with the patients and collect the results do not know which patients are receiving the placebo. This ensures that they do not treat the patients receiving the placebo differently or prompt them when asking about their symptoms.

accurate experiments

Reliable experiments

The degree of accuracy of the results of an experiment depends on the instruments that have been used to measure the results. If you want to measure the length of your classroom, you could pace along the length of the room and count the number of steps from one end of the room to the other. You could also use a trundle wheel with marks every 10 cm, or you could use a tape measure marked in millimetres. The tape measure would provide the most accurate measurement. Similarly, to measure 100 mL water, you could use a measuring cylinder that is graduated in millilitres or you could use a measuring cup that is marked every 100 millilitres. The measuring cylinder would provide a more accurate measurement than the cup.

An experiment is reliable if it consistently produces the same results when it is repeated. Imagine that you want to compare the strength of plastic bags by filling the bags with weights until the bag breaks. If the experiment is reliable, you will find that the mass needed to break a particular type of bag would always be about the same each time the experiment was repeated. If the results vary greatly between trials, the experiment is not reliable. You can improve the reliability of an experiment by repeating it a number of times and calculating the average of the results.

80 mL

70 mL 50 mL

60 mL

40 mL

50 mL

40 mL 30 mL

30 mL

20 mL

10 mL 10 mL

0 mL

0 mL

80 mL

Measuring cylinder: Each fine graduation 1 mL

60 mL 40 mL 20 mL

Do the tablets really work or is it a placebo effect?

Beaker Each graduation 20 mL

Burette Each fine graduation 0.1 mL

Each fine graduation 1 m

Each of these contains 40 mL of water. Which measurement is most accurate?

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Experiments can be repeated in different ways. In some instances, it is just a matter of doing the same experiment again. For example, if you want to compare the speed of a balloon rocket gliding along string with one gliding along nylon fishing line, you would do the experiment a few times and then calculate and compare the average speeds (see the figure at the bottom left of page 511). Each repetition of an experiment is called a trial. Increasing the number of trials increases the reliability of the experiment. For experiments involving plants, animals and people, it is usually easier to do the experiment once but use a large number of plants, animals or people. The number of organisms used in the experiment is called the sample size. Reliable experiments have a large sample size.

INVESTIGATION 20.2 The flying straw You will need: paper scissors straws sticky tape metre ruler or tape measure stopwatch ◗ Cut out two strips of paper. One strip should be 10 cm by 2 cm and the other

should be 20 cm by 2 cm. ◗ Attach the strips of paper to a straw as shown in the photo below.

A flying straw ◗ Throw the straw forwards and observe how far it flies. This is the basic

flying straw.

keep it safe The most important thing to consider when planning an investigation is safety. Your teacher may ask you to write a risk assessment before you start your research project. A risk assessment involves listing any potential hazards relating to your investigation and explaining how you will minimise these risks. For example, if you were doing an experiment to test whether the temperature of an acid affects how quickly it reacts with magnesium, your risk assessment might look like this. Risk

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DIsCUssIOn 1

The length of the straw is one variable that may affect how far the flying straw can fly. List at least five other variables that may affect the distance flown.

2

Choose one of the variables from question 1 and design an experiment to test the effect of this variable. Decide what you will measure first. It could be the distance flown, the amount of time the straw stays in the air or whether the straw flies in a straight line. Your experiment should include: (a) the aim (b) a hypothesis (c) the method, including a diagram (d) a table to enter your results.

3

Carry out the experiment and enter the results in the table you designed.

4

Write a conclusion based on your results.

How the risk will be minimised

Acid splashing into face and eyes

• Wear safety goggles. • Heat acid using a water bath rather than directly over a Bunsen burner flame. • Use dilute acid rather than concentrated acid.

Cutting fingers when tearing small pieces of magnesium

• Use scissors to cut magnesium.

Core Science | Stage 4 Complete course

ThInk

Activities

2 Copy and complete the table at the bottom of the page.

REmEmBER 1 Match each of the following words with its meaning: variable, dependent variable, independent variable, controlled variables, sample size, reliability, accuracy, validity, trial, risk assessment. (a) How exact the measurements are in an experiment (b) The number of plants, animals or other items used in an experiment (c) The variables that must be kept constant in an experiment (d) Whether the experiment actually tests what it is supposed to test (e) The variable that is deliberately changed in an experiment (f) Name given to each repetition of an experiment (g) Whether the experiment produces similar results when it is repeated (h) A list of the hazards in an experiment and how these will be minimised (i) Something that can be changed in an experiment (j) The variable that is measured in an experiment

Hypothesis Plants grow faster when it is hot.

3 Charlotte wanted to compare the amount of air in two brands of icecream. She placed a large spoon of each ice-cream in two different cups and let the ice-cream melt. She then measured how much liquid was in each cup. There was less liquid in cup B so she concluded that ice-cream B must contain more air. (a) Describe one way that Charlotte could improve the validity of her experiment. (b) Outline how the accuracy of Charlotte s experiment could be increased. (c) Outline how the experiment could be made more reliable.

(b) Describe how the experiment could be made more: (i) accurate (ii) reliable (iii) valid.

DEsIgn 5 Design experiments to test the following hypotheses. (a) Eggs become less dense as they age. (b) Detergent A produces more foam than detergent B. (c) Cola drink P contains more sugar than cola drink C. (d) Talking to plants makes them grow faster. (e) Chocolate S melts at a higher temperature than chocolate Q. work sheet

20.2 Accuracy and reliability

4 Jossie wanted to find out if the mass of a rock affects how far the rock can be thrown. She weighed some rocks, threw each rock as far as possible and measured the distance by pacing between the point where she threw the rock and the point where it landed. (a) Construct a table listing at least two risks associated with this experiment and how each risk could be minimised.

Independent variable Temperature

Dependent variable Height of plant

Controlled variable Plant species, amount of water, soil type

Exercise increases breathing rate. Guinea pigs eat more when it is cold. Sugar dissolves faster in hot water than in cold water. The more you water plants, the faster they grow.

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20.6

Presenting your results Values or measurements obtained from an investigation are called data. Having collected the data, it is important to present it clearly so that another person reading or studying it can understand it. Tables and graphs are a great way to organise data.

Using tables A table organises data so that trends are more easily identified. An example of a simple table is shown below; it includes all the features you need to remember when constructing a table.

Always include a title for your table.

Depth (km)

Temperature ( C)

0

15

1

44

2

73

3

102

4

130

5

158

6

187

7

215

8

242

Nutrients in 100 g of -plus cereal

Enter the data in the body of the table. Do not include units in this part of the table.

Do large paper aeroplanes fly further than small paper aeroplanes? 21

15

9

Length of paper (cm)

14

10

6

Distance flown (m)

Other B vitamins (0.02 g) Fat (0.5 g)

Niacin (0.02 g) Iron (0.01 g)

Calcium (0.5 g) Fibre (5 g) Sugars (18 g)

Labels

Width of paper (cm)

Trial 1

4.5

6.2

3.2

Trial 2

4.9

5.9

3.6

Trial 3

4.6

5.8

3.5

Core Science | Stage 4 Complete course

There are five different types of graphs: pie charts, column graphs and bar graphs, divided bar graphs, histograms and line graphs. A pie chart (also known as a sector graph) is a circle divided into sections that represent parts of the whole. This type of graph can be used when the data can be added as parts of a whole. The example below shows the food types, vitamins and minerals that make up the nutrients in a breakfast cereal.

You may need to construct more complex tables, like the one below, to present your student research project results.

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Organising data as a graph is a widely recognised way of making a clear presentation. It makes the information easier to read, interpret, show trends and make conclusions. A graph, especially a line graph, can also be used to find values other than those used in the investigation. This can be done by interpolation or extrapolation (see pages 530 1).

Pie charts (or sector graphs)

The column headings show clearly what has been measured.

Use a ruler to draw lines for rows, columns and borders.

Average

Why use graphs?

Types of graphs

Include the measurement units in the headings. Temperature of the Earth at different depths

Using graphs

Units Protein (20.5 g) Complex carbohydrates (55.45 g) A pie chart

Divided bar graphs Divided bar graphs are also used to represent to represent parts of a whole. However, the data is represented as a long rectangle, rather than a circle, divided into sections. The example below shows the type of footwear worn to school today by male and female students.

The example below shows the lengths of different metal bars when heated. Each bar represents a different metal bar. Lengths of different metal bars when heated in the same way

Note: The metal bars were of identical lengths before heating.

Metal A

Types of footwear worn to school today

Metal B

Metal bar

Female

Metal C Male

Metal D 0

10

20

30

40

50

Number of students wearing footwear School shoes

Thongs

Running shoes

0

Boots

Column graphs and bar graphs A column graph (sometimes called a bar graph) has two axes and uses rectangles (columns or bars) to represent each piece of data. The height or length of the rectangles represents the values in the data. The width of the rectangles is kept constant. This type of graph can be used when the data cannot be connected and is therefore not continuous. The example below shows data on the average height to which different balls bounced during an experiment. Each column represents a different type of ball.

Histograms are similar to column graphs except that the columns touch each other because the data is continuous. They are often used to present the results of surveys. In the histogram below, each column represents the number of students that reached a particular height. Heights of a group of students in a class 20

15

Height of bounce (m)

1.2 1.0 0.8

Number of students

All balls were bounced by the same person, from the same height and onto the same surface.

30

Histograms

Heights to which different types of balls bounced

1.4

20 Length (cm)

A bar graph

A divided bar graph

1.6

10

10

5

0.6 0.4 0.2 0.0

0 Golf ball

Tennis ball

Basketball

140

Type of ball A column graph

145

150

155

160

165

170

Height (cm) A histogram

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Line graphs A line graph has two axes a horizontal axis and a vertical axis. The horizontal axis is known as the x-axis, and the vertical axis is known as the y-axis. The line graph is formed by joining a series of points or drawing a line of best fit through the points. Each

4. Setting up the scales Each axis should be marked into units that cover the entire range of the measurement. For example, if the distance ranges from 0 m to 96 m, then 0 m and 100 m could be the lowest and highest values on the vertical scale. The distance between the top and bottom values is then broken up into equal divisions and marked. The horizontal axis must also have its own range of values and uniform scale (which does not have to be the same scale as the vertical axis). The most important points about the scales are: sæ THEYæMUSTæSHOWæTHEæENTIREæRANGEæOFææ measurements sæ THEYæMUSTæBEæUNIFORMæTHATæIS æSHOWææ equal divisions for equal increases in value.

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2. Title Tell the reader what the graph is about The title should describe the results of the investigation or the relationship between variables.

1. rid Graphs should always be drawn on grid paper to ensure that the values are accurately placed. Drawing freehand on lined or plain paper is not accurate enough for most graphs.

Distance covered by a runner in 15 seconds

Data table

100

80

Distance (m)

3. Setting up and labelling the axes Graphs represent a relationship between two variables. When choosing which variable to put on each axis, remember that there is usually an independent variable (which the investigator chooses) and a dependent variable. For example, if students wish to find out how far a runner could run in 15 seconds, they may choose to measure the distance covered every five seconds. The time of each measurement has been chosen by the students and is the independent variable. The distance that is measured is therefore the dependent variable. Usually the independent variable is plotted on the horizontal x-axis and the dependent variable on the vertical y-axis. After deciding on the variable for each axis, you must clearly label the axes with the variable and the units in which the variables are measured. The unit is written in brackets after the name of the variable.

point represents a set of data for two variables, such as height and time. Two or more lines may be drawn on the same graph. Line graphs are used to show continuous data that is, data in which the values follow on from each other. The features of line graphs are shown below.

Distance (m)

Time (s)

0

4

8

5

37

10

96

15

60

5. Putting in the values A point is made for each pair of values (the meeting point of two imaginary lines from each axis). The points should be clearly visible. Include a point for (0, 0) only if you have the data for this point.

40

20

5

10

15

Time (s) 6. Drawing the line A line is then drawn through the points. A line that follows the general direction of the points is called a line of best fit because it best fits the data. It should be on or as close to as many points as possible. Some points follow the shape of a curve, rather than a straight line. A curved line that touches all the points can then be used. The type of data you are graphing may lead you to expect either a straight line or a curve. For example, you might expect the increase in temperature of water being boiled to be presented as a straight line because the temperature increases at a steady rate. The growth rate of a red panda (see page 540) would be curved because the panda will have growth spurts. Inspection of the data will help you to decide whether your line should be a straight line or a smooth, curved line.

Interpolation

Extrapolation

Line graphs can be used to estimate measurements that were not actually in an experiment. The table below shows the results of an experiment where a student measured how many spoons of sugar dissolved in a cup of tea at various temperatures.

In many cases it is also possible to assume that the two variables will hold the same relationship beyond the values that have been plotted. This is called extrapolation. Consider the table below, which shows the results obtained when different masses were attached to a spring and the increase in length of the spring was measured.

Amount of sugar that dissolves in one cup of tea at different temperatures Temperature ( C)

Mass of sugar dissolved (g)

0

4

20

30

40

60

60

98

80

120

100

160

The student did not measure how much sugar dissolved at 50 C, but we can work this out by interpolation. First we need to plot the data collected in the experiment. Then we read off the graph the amount of sugar that would dissolve at 50 C. The same procedure can be used to work out the water temperature that would be needed to dissolve 130 g sugar in one cup of tea. This is shown in the graph below. Effect of temperature on the amount of sugar dissolved in tea

Amount that a spring stretched when various masses were attached to it Mass attached to the spring (kg)

Length by which spring stretched (cm)

0

0

0.5

8

1.0

16

1.6

26

?

32

If you want to predict the mass needed to stretch the spring by 32 centimetres, you need to plot the data on a graph and extrapolate the value. The data in the table above have been plotted on the graph below. Values have been plotted up to a mass of 1.6 kg and an increase in length of of 26 centimetres. The line on the graph has been projected onwards (as the dotted lines show). This extrapolation shows that a mass of 2 kg will stretch the spring 32 centimetres. Effect of mass on spring stretch

180

140

Length by which spring stretched (cm)

160 Dotted line 2

Mass (g)

120 100 Dotted line 1 80 60 40 20 0

20

40

60 Temperature ( C)

Using a line graph for interpolation

80

100

30

20

10

0 0

0.5

1.0

1.5

2.0

Mass attached to spring (kg) Using a line graph for extrapolation

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(i) Can you suggest any uses of plastics that would contribute to waste products? List them and explain your choices. (ii) Can you suggest alternatives to reduce the amount of plastic waste products?

Activities anaLYsE anD EvaLUaTE 1 (a) Construct a line graph of the data shown in the table at the top left of the previous page. (b) Use your graph to interpolate the mass of sugar that would dissolve in one cup of tea if the temperature of the tea was (i) 70 C and (ii) 90 C. 2 (a) Complete the bottom row of the table on page 528. (b) Construct a column graph showing the length of the paper used to make the plane on the horizontal axis and the average distance flown on the vertical axis.

5 The data in the following table relates the speed of a car to its stopping distance (the distance the car travels after the brakes are applied). Relationship between the speed of a car and its stopping distance Speed of car (m/s)

3 Construct a column graph using the information below. Nutrients in 30 g serving of ice-cream Amount (g)

Protein

2.00

Fat

6.00

Carbohydrate

polysaccharide

11.00

Carbohydrate

sugars

10.00

Cholesterol

0.02

Calcium

0.10

Potassium

0.80

Sodium

0.05

Building

4.0

Furniture and bedding

8.0

Housewares

4.0

Marine, toys and leisure

2.0

Packaging and materials handling

31.0

Transport Others

5.0 14.0

(b) Choose two uses of plastic from your graph. For each use, state a particular item that is made of plastic. (c) There has been recent controversy about the waste products that humans create.

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20

36

30

72

40

120

400

200

0 0

24.0 8.0

12

Increase in mass of pondweed with time

Percentage (%)

Electrical/electronic

10

600

Uses of plastics in Australia

Agriculture

0

6 The following graph shows the increase in mass of pondweed (a type of plant that grows in ponds).

4 The following table shows the uses of plastics in Australia. (a) Select a suitable graph type and prepare a graph from this table.

Use

0

(a) Construct a graph of the data. (b) Make a conclusion about the information in the graph. (c) How could this information be applied to your everyday life?

Dry weight of pondweed (mg)

Nutrient

Stopping distance (m)

2 4 Time (weeks)

6 1

(a) What was the mass of the pondweed after 3 2 weeks of growth? (b) How long did it take for the pondweed to reach a mass of 250 grams? (c) Predict the mass of pondweed after 6 weeks of growth. (d) Can you be sure that your extrapolation in part (c) is valid? Justify your answer. (e) Would the interpolations in parts (a) and (b) be more valid than your extrapolation? Discuss your ideas in class. work sheet

20.3 Presenting results

20.7

Using technology: spreadsheets A spreadsheet is a document that stores data in columns and rows. Spreadsheets used to be written on paper by hand. Shopkeepers and bank tellers needed to keep neat handwritten ledgers to record all transactions. Today, computers and software such as Microsoft Excel are used to create and edit spreadsheets. Spreadsheets can also be used to create graphs and charts at the click of a button.

some spreadsheet terminology In a spreadsheet, the data is organised in rows and columns. The columns are named using letters (such as column A) and the rows are named using numbers (such as row 3). Cells are the boxes in the spreadsheet. The cell reference tells us which column and row the cell is in. For example, cell B3 is in column B and row 3. The active cell is the cell you will type the data in. In Excel, it has a dark border around it. This is shown in the diagram below.

Working with Excel spreadsheets When you create a spreadsheet, you need to decide how many columns and rows you will need and enter a suitable heading for each column. This is similar to designing a table. Make sure that you include units where relevant. When using Excel, you can format cells in a variety of ways by clicking on Format and then Cells.

Entering formulae in Excel If you want to do calculations on the data in a spreadsheet, you need to enter a formula. In Excel, a formula always starts with an equals sign (=). If you want the total of cell A2 and cell B2 to appear in cell C2, you would type the formula =A2+B2 in cell C2, and then press the [Enter] key. You can also use one of the many functions available in Excel. For example, it is much quicker to use the Average function to calculate the average of 50 numbers than to type in a formula to add the 50 cells and divide the total by 50. The Insert function button, fx, can be used to view the format required for particular functions.

Drawing graphs and charts

Cell B3 is the active cell.

INVESTIGATION 20.3 Dissolving aspirin You will need: beaker thermometer ice Bunsen burner, tripod, heatproof mat 2 tablets of soluble aspirin, such as Aspro stopwatch ◗ Your teacher will assign each group two temperatures to

test. For example, your teacher might ask you to test 20 C and 50 C.

Drawing a graph using Excel is easy. Just highlight the data you want to graph, click on the Chart wizard button and follow the prompts. However, remember that a line graph is called an XY scatter graph in Excel. ◗ Pour 200 mL water into a beaker. Adjust the temperature

of the water by adding ice or by heating the water over a Bunsen burner until the water temperature matches one of the temperatures you are to test. ◗ Add one of the tablets to the water. Use the stopwatch to record the time taken for the tablet to dissolve completely. ◗ Repeat these two steps for the second temperature.

DIsCUssIOn 1 Create a spreadsheet with the column headings Water temperature ( C) and Time taken to dissolve (s) .

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2

Enter all the groups results in your spreadsheet.

3

If necessary put the results in order from the lowest to the highest temperature by selecting (highlighting) all the data and clicking on the Sort ascending . You should end up with a table similar button to the one below.

4

rather than keeping handwritten records in a book.

Activities REmEmBER

CREaTE

1 In the screenshot below, identify the letter pointing to: (a) cell C2 (b) cell E5 (c) the active cell (d) a formula (e) the Chart wizard button (f) the Insert function button (g) a column (h) a row.

3 (a) Collect the following data for each student in your class, (i) First name (ii) Gender (iii) Foot length (cm) (iv) Height (cm) (v) Favourite subject (vi) Country where mother was born (b) Enter the data you collected into a spreadsheet. (c) Use the Chart wizard to construct an XY scatter graph (without joining points) showing foot G length on the x-axis and height on the y-axis. (d) Use your graph to decide if there is a relationship between foot length and height. F

2 List two advantages and two disadvantages of using a computer spreadsheet program to store data B

A

D

E C

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With the data still selected, click on the Chart wizard button. When prompted, choose an XY scatter graph with the points joined by a straight line. When prompted, enter Does the water temperature affect how long it takes for a tablet to dissolve? as the chart title, Temperature ( C) as the x-axis title and Time taken to dissolve (s) as the y-axis title. You should obtain a graph similar to the one below.

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(e) Apply a filter to the Gender column. To do this, click on one of the data entries in the column. Then click on Data, then Filter and then AutoFilter. Click on the arrow next to the column heading to select data for just the girls, just the boys or both boys and girls. (f) Construct an XY scatter graph of height versus foot length for the girls in the class only. How is the graph different from the graph showing the data for the whole class? (g) Look at the Favourite subject column and count how many students liked each subject most. Create a new spreadsheet with the column headings Subject and Number of students . (h) Use the Chart wizard to construct a column graph and a pie chart that show the data in the spreadsheet you just created. (i) Repeat parts (g) and (h) for the data in the Country column.

20.8

Using technology: databases Spreadsheets are useful for organising and presenting data. However, for very large amounts of information, a database can make it easier to keep the data organised and to search quickly for data that matches particular criteria.

What is a database? You use databases all the time without even thinking about them. When you look up a phone number in the white pages, you are using a database of people in your city or town who have telephones. When you look up a book s table of contents, you are looking at a database of the chapter names and the page numbers where you can find them. The index at the back of books and your train or bus timetables are also databases.

The phone book is a huge database of people with telephones in your city or town.

Another way of thinking of a database is to describe it as a table of data. Of course, you have been making tables of data yourself all year. A telephone book is a huge table with three columns of data names, addresses and telephone numbers. The contents of a book is a table with just two columns chapter titles and page numbers.

Shop catalogues and library catalogues are also examples of databases. A shop catalogue contains a list of items sold by the shop as well as a description of each item and its cost. It is a database with three columns. A library catalogue stores data about all the resources held in the library. In this case, the columns in the database include authors, title, subject and type of resources (such as book or video).

Electronic databases A database on paper has limitations. You can crossreference only two things and then usually only in a specific order. For example, you can look up a person s telephone number easily only if you first look up their name and address. You can t do the reverse; that is, you can t look up a phone number and find out the name of the person who has that number (unless, of course, you have a lot of time and patience). For this reason, most databases are now stored electronically. To find a library book you can use a computer to access the library s catalogue. You can perform a search for topics, authors, date of publication and more. You can refine your search and perhaps look for just magazine articles or videos. You can even read a short summary (synopsis) of each article. This is all possible because computers are very good at storing lots and lots of data and retrieving it very quickly. Unlike a database on paper, a computer can store data (such as

the topic and author of a book) in a table with as many columns as you like and it can search any of the columns rather than just the first one. And it does all this very quickly. The only problem is that a computer can t actually think, so it is up to the person who designs the database to do so very thoughtfully so that it will be easy to search.

Why use an electronic database in science? Scientists often have huge amounts of data that they need to organise and search (or allow others to search). For example, the scientists who help the police to solve crimes are called forensic scientists. They know that a substance called DNA, which is found in every one of our cells, is unique to each human being; that is, no two people on the planet have the same DNA unless they are identical twins.

As each person on the planet has a unique set of DNA, police can solve crimes by matching DNA samples from crime scenes to DNA information stored on a database.

Forensic scientists are setting up a database of DNA from convicted

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criminals that helps police to crack unsolved crimes. Police can compare any DNA in tissue found at crime scenes with the DNA database. Astronomers gather huge amounts of data about the solar system using optical telescopes, radio telescopes and information sent back by space probes. The large amount of information they gather is organised in computer databases so that they, or other astronomers around the world, can search the data to use in their research projects.

directory into a computer database, it would have three fields: name, address and telephone number. Each person s details would then be a record. It would look something like the screenshot below.

Designing databases Just as a table is made up of columns and rows, so too is a database except that the columns are called fields and the rows records. If you made the telephone

Activities

Access icon shown below.

anaLYsE anD EvaLUaTE Creating a database of Nobel prize winners Before creating your database, you will need to find some information to put in it. This is best done as a class activity with each student in the class researching one or two Nobel prize winners. ◗ Use the Nobel prize weblink in your eBook plus eBookPLUS to find a list of Nobel prize winners. ◗ Each student in the class should research one or two different Nobel prize winners. Choose people who have won a Nobel prize for work in the categories of Chemistry, Physics or Medicine. ◗ For each prize winner, collect the data listed below. Ideally the data should be written on cards that can be passed around the class, or it could be displayed in large writing on butcher s paper around the room. • First name • Last name • Country of birth • Year of birth • Category of award (such as Chemistry, Physics and Medicine) • Organisation (where the person worked) • Nobel prize awarded for (one sentence or phrase that outlines the work for which the scientist received the award) • Share received (if the award was shared by a group of people) ◗ Microsoft Access software is commonly used to create databases. The following instructions are for the 2003 edition of this software. Other editions are similar to use but the screens are not exactly the same. You can start Access by clicking on Start, then Programs and then the

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◗ When you open the software, click on File and then

New. A list of options will appear in the task pane on the right-hand side of the screen. Choose the option Blank database. A dialog box will appear for you to enter a name for your database and navigate to the folder where you want to save the database. Choose a sensible name (such as Nobel prize winners ) and save it where you normally save your science work. This is shown in the screenshot below.

◗ A new dialog box will be displayed. Choose the option

Create table in Design view and press [Enter]. A new screen will appear where you can enter field names, which are the column headings for the database. Enter the field names as shown below. You will note that, by default, the data type is Text even though some of the fields are numbers. This is not important for this database.

done this, click Next. In the next dialog box, enter a name for your query, select Modify the query design and click on Finish.

Click on a field to select it.

Click on the single arrow to move the field into the Selected Fields box.

◗ The screen below will appear. Now enter the ◗ Now that you have designed the database, it is time to

change to datasheet view. Click on the Datasheet view button in the top left-hand corner of the screen. You will be prompted to save the table. Give the table a suitable name (such as Table 1 ) and click Save. When you are asked if you want to create a primary key, click No. The table shown below should appear. You are now in datasheet view. Note that the Design view button now appears in the left-hand corner of the screen.

criteria you want the query to look for in the appropriate boxes. In the Category column, type Chemistry (without the quotation marks) in the Criteria row. In the Country of birth column, type United States in the Criteria row. Quotation marks will automatically appear when you press [Enter]. This is shown below.

◗ Enter the data that you and your classmates found

into the table. When you have done this, save your database. The great thing about databases is that they allow you to search for data that matches particular criteria. This is called running a query. We are going to create a query to find all the Nobel prize winners in our database who were awarded a prize for Medicine and were born in the United States. ◗ Make sure you are in datasheet view. Click on the arrow next to the New object button. Select Query and then Simple query wizard and click OK. The fields in your table will be displayed; click on the ones you want to appear in the query then click on the single arrow to move them into the Selected Fields box. Select the following fields: first name, last name, country of birth and category. When you have

◗ Now click on the Run button in the toolbar

near the top of the screen. The query will run and a table displaying the Nobel prize winners that match your criteria will appear. ◗ Create a new query to display the Nobel prize winners who won the Nobel prize for Physics and were born in England.

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20.9

Writing your report A variety of formats can be used to present a student research project. Your teacher might expect you to give an oral presentation to your class or to prepare a poster or PowerPoint presentation about your project. In most instances, though, your written report should use some of the headings used by scientists when they publish their investigations in scientific journals. You should check with your Science teacher which of the following sections to include in your report.

Abstract Briefly describe your experiments and your main conclusions. Even though this appears at the beginning of your report, it is best not to write it until after you have completed the rest of your report.

Introduction Present all relevant background information. Include a statement of the problem that you are investigating, saying why it is relevant or important. You could also explain why you became interested in the topic.

Aim or problem State the purpose of your investigation: that is, what you are trying to find out.

Results Observations and measurements (data) are presented in this section. Wherever possible, present data as a table so that they are easy to read. Graphs can be used to help you and the reader interpret data. Each table and graph should have a title. Ensure that you use the most appropriate type of graph for your data (see pages 21 and 528 30).

Discussion Discuss your results here. Begin with a statement of what your results indicate about the answer to your question. Explain how your results might be useful. Any weaknesses in your design or difficulties in measuring could be outlined here. Explain how you could have improved your experiments. What further experiments are suggested by your results?

Conclusion

Hypothesis Using the knowledge you already have about your topic, make a guess about what you will find out by doing your investigation.

Materials and method Describe in detail how you did your experiments. Begin with a list of the equipment used and include

This is a brief statement of what you found out and may link with the final paragraph of your Discussion. It is a good idea to read your Aim again before you write your conclusion. Your conclusion should also state whether your hypothesis was supported. Don t be disappointed if it is not supported. Some scientists deliberately set out to reject hypotheses! Rubbish found in the schoolyard (percentage by weight)

30 25

Number of people

Height of plant (cm)

photographs of your equipment if appropriate. The description of the method must be detailed enough to allow somebody else to repeat your experiments. It should also convince the reader that your investigation is well controlled. Labelled diagrams can be used to make your description clear. Using a stepby-step outline makes your method easier to follow.

20 15 10 5 0

5

10 15 Number of days

20

25

Food 40

20 15 10 5 0 Black

Brown Red Colour of hair

Blond

Aluminium 10 Plastic 20

(Left to right ) A line graph, a bar graph and a pie chart. Choose the type of graph that is appropriate to your data.

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Paper 30

Bibliography Make a list of books and other printed or audiovisual material that you have referred to. The list should include enough information to allow the source of information to be easily found by the reader. Arrange the sources in alphabetical order. For each resource, list the following information in the order shown. • Author(s) (if known) • Title of book or article • Publisher or name of journal/magazine (if not in title) Acknowledge the • Place of publication (if given) help you received. • Date of publication • Chapter or pages used Some examples are listed below. Breidahl, H. Australia s Southern Shores, Lothian, Melbourne, 1997, Chapter 2. World Book Encyclopedia, Volume 4, 1991, pp. 234 236. The Battle of the Bathroom , Choice, Sydney, November 1990, pp. 34 37. You may be required to present your research project to your classmates.

Acknowledgements List the people and organisations who gave you help or advice. You should state how each person or organisation assisted you.

Activities REmEmBER 1 Identify which section of your investigation report you should write each of the following in. (a) A list of the books and other resources you used to find information for your project (b) A table showing all the measurements you recorded (c) A diagram of the equipment you used (d) The purpose of the experiment (e) A brief summary of your investigation and findings (f) A statement that relates the results back to the aim and outlines what your results show

ThInk 2 When scientists write up their investigations for publication in a scientific journal, the abstract is one of the most important parts of the report. Explain why the abstract is usually read by many more people than the full report.

4 Explain why it is important for scientists to publish their investigations in scientific journals and to read the reports written by other scientists. 5 Many scientists choose to have their reports published in journals written in English, even if English is not their first language. Suggest why.

InvEsTIgaTE 6 Find out what a patent is and why scientists sometimes patent their ideas. 7 There have been instances where scientists have faked their results or committed other types of scientific misconduct. (a) Use the words scientific misconduct in a search engine to find examples of such instances. (b) Outline why you think that some scientists might be tempted to fake or fabricate their results. (c) Explain why cases of scientific misconduct are damaging to all scientists. (d) What do you think might happen to scientists who are found to have faked their results?

3 Justify why it is important for scientists to clearly describe the method they used when they write a report of their investigation.

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LOOKING BACK 1 The boiling point of water changes with air pressure. For example, water may not boil at 100 C at the top of Mount Everest, where the air pressure is less than the pressure at sea level. The following data shows the boiling point of water at various air pressures. Boiling point of water at different air pressures Air pressure in kilopascals (kPa)

Boiling point of water ( C)

Red panda cubs masses 1996 97 (grams) Week

Singalia

Sallyana

1

213

219

2

285

290

3

330

349

4

365

377

5

403

408

0

0

6

465

452

1

20

7

536

514

7

40

8

564

576

21

60

9

594

610

45

80

10

650

637

101

100

11

703

680

200

120

12

714

740

13

814

796

14

872

812

15

956

806

16

1111

786

17

1043

890

2 Draw a cluster map that summarises the key ideas on pages 524 6.

18

1130

1000

19

1163

1083

3 Singalia and Sallyana are two red panda cubs born at Sydney s Taronga Zoo. The table at right shows their masses during their first 22 weeks. The photograph below shows one of the cubs being weighed.

20

1182

1162

21

1225

1218

22

1335

1270

(a) (b) (c) (d)

Graph the data. Describe the shape of your graph. What is the pressure of the atmosphere at sea level? Would it take a longer or shorter time to boil water at the top of Mount Everest, compared with the time it would take at sea level? Explain your answer.

(e) Which were the fastest and slowest growth periods for each panda? (f) What age was each of the cubs when they reached 1 kg? (g) Predict the age at which each cub will reach 1.5 kg. Explain how you made your prediction. What assumption did you make to answer the question?

TEsT YOURsELF Use the following scenario to answer questions 1 and 2. (a) Construct a line graph showing both sets of data on the same set of axes. Use different symbols for the points for each panda and label each line with the panda s name. You may have to extend the vertical axis to fit in the scale for the pandas masses (or else convert the masses to kilograms and plot in kilograms). Interpret the graph from part (a) to answer the following questions. (b) Describe the growth of each of the panda cubs. How do they compare with each other? (c) How long did it take the cubs to double their mass measured in week 1? (d) Did the pandas grow at the same rate during the 22 weeks?

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Kimberley and Glenn were walking past their neighbour s house when they noticed that a front window was broken. Glenn told Kimberley that somebody had probably thrown a ball through the window. They had a closer look and noticed clothes scattered all over the floor and drawers open. Kimberley noticed some blood on the broken glass. She told Glenn that the house had been burgled. Glenn agreed and they called the police. 1 The statement Kimberley noticed some blood on the broken glass is A an observation. B a hypothesis. C a conclusion. D an inference. (1 mark)

foam than other washing powders. Emily did the following experiment to compare how much foam was produced by three brands of washing powder.

2 Who suggested a hypothesis? A No-one B Glenn only C Kimberley only D Both Glenn and Kimberley

(1 mark)

Use the following scenario and graph to answer questions 3 and 4. Jane and Greg decided to test how quickly water would boil when using either the yellow flame or blue flame of the Bunsen burner. They set up identical experiments, except that Jane used a blue flame and Greg used a yellow flame. Their results are graphed below. 100 Jane s result

Temperature ( C)

80

This is when Greg changed Bunsen burners.

60 Greg s result

40

• • •

20

0

•

5

10 15 Time (min)

She put one teaspoon of each washing powder in separate 100 mL measuring cylinders. She added 60 mL warm water to each measuring cylinder. She shook each measuring cylinder vigorously. She measured the height of the foam produced in each measuring cylinder.

20

3 What was the temperature of Greg s water when Jane s water reached 100 C? A 100 C B 60 C C 62 C D 70 C (1 mark) 4 Jane removed her beaker and Greg quickly placed his beaker over Jane s Bunsen burner. Assuming that the temperature of Greg s beaker did not drop while swapping Bunsen burners, at what time will his water boil? A 17 minutes B 22 minutes C 15 minutes D 18 minutes (1 mark) 5 Huang and Tina conducted an experiment to find out if radish plants grow better in the shade. They placed three plants under a veranda at the back of the house and another three in a sunny place in the front yard. All plants were planted in the same soil. Huang and Tina watered each of the plants equally each day. (a) Did they conduct a fair test? (b) How could Huang and Tina improve the design of their experiment? List as many improvements as possible. (2 marks) 6 If you have a front-loading washing machine, you should use low-sudsing washing powder, which produces less

100 mL

80 mL

Foam 60 mL

Use a ruler to measure the height of the foam.

40 mL

20 mL

One teaspoon washing powder 60 mL water The amount of foam produced can be measured with a ruler.

(a) Identify the independent and dependent variables in Emily s experiment. (b) Identify the variables that Emily controlled? (c) Which variables could have been controlled better? (d) Suggest how Emily s experiment could be made more reliable. (4 marks)

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Text types When completing assessment tasks or answering examination questions it is important to use the correct text type. The table below describes some text types commonly used in Science.

Text type

542

Examples of questions that would require the use of this text type

Features of text type

Discussion

Discuss whether research involving the use of embryonic stem cells should be legal in Australia.

In a discussion the writer presents both sides of an issue. The first paragraph is used to introduce and describe the problem or question. A number of paragraphs are then used to introduce lines of argument both in favour of and against the issue. This is followed by a concluding paragraph where the writer may express a particular viewpoint after having considered all the arguments or conclude that they remain undecided based on all the arguments they have outlined.

Explanation

Explain why average daily temperatures are higher in summer than in winter.

An explanation explains why or how something happens. It starts with a description of the object or phenomena. This is followed by a step-by-step explanation. This text type contains linking words such as because, as a result and consequently, which describe cause and effect.

Procedure

Write a procedure for the separation of sand from copper sulfate.

A procedure is a list of steps. Each step starts with a verb. Most recipes are procedures.

Exposition

Should mining of uranium in Kakadu National Park be allowed? Write a letter to the editor of the The Sydney Morning Herald outlining your views on the issue.

An exposition has a similar structure to a discussion, but it favours one side of the argument instead of giving similar weight to both sides of the issue.

Recount

Recount how you prepared a sample of onion epidermis for viewing under a microscope.

A recount is written in the past tense. It is a sequenced description of what happened or what you did. In includes linking words such as then, after, next and finally.

Report

Write a report about an endangered species.

A report provides information about something. It is written in the present tense and includes facts and technical terms. The first paragraph is a general description. Each of the paragraphs in the body of the report describes a different aspect of the item. Note: An experiment or scientific report is not the same as a report. The features of a scientific report are described on p. 538.

Response

Write a review of the game Body invaders.

In a response the writer describes their personal reactions to something, such as how it made them feel or what they learned from it.

Core Science | Stage 4 Complete course

Glossary abdomen: the end part of an insect’s body, behind the thorax abiotic factors: the non-living features in an ecosystem abrasive: a property of a material or substance that easily scratches another absorb: take in something. Absorbed energy, such as light, sound or heat, can be stored or released as a different form of energy. abundance: the number of a species living within an area acid: a chemical that reacts with a base to produce a salt and water. Edible acids taste sour. acid rain: rainwater, snow or fog that contains dissolved chemicals, such as carbon dioxide, that make it acidic. Acid rain can cause rock to weather faster than pure rain can. acidity: describes the amount of acid in a mixture. Acids have a sour taste and neutralise bases. Too much acid in water would make it harmful to drink. air: the mixture of gases in the atmosphere air pressure: the amount of force pushing on the air air resistance: the force of air pushing on an object as the object moves through the air alchemist: olden-day ‘chemist’ who mixed chemicals and tried to change ordinary metals into gold. Alchemists also tried to tell the future. algae: commonly known as seaweed; an organism belonging to Kingdom Protista that lives in water. It contains chlorophyll and may range from a single-celled organism to a multi-celled long structure. alkali: a base that dissolves in water allotropes: forms of an element that have different appearances and properties due to differences in their molecular structure. Diamond, graphite and amorphous carbon are allotropes of carbon. alloy: a mixture of a metal with a non-metal or another metal alum: the common name for the chemical potassium aluminium sulphate alveoli: tiny air sacs in the lungs at the ends of the narrowest tubes. Oxygen moves from alveoli into the surrounding blood vessels, in exchange for carbon dioxide. ammeter: a device used to measure the amount of current in a circuit. Ammeters are placed in series with other components in a circuit. amoeba: microscopic organism consisting of one cell that has a thin membrane. It belongs to Kingdom Protista but has animal-like features. ampere: the unit for measuring electric current, usually abbreviated to amps (A) amylase: an enzyme in saliva that breaks starch down into sugar antacid: a substance containing a base used to treat indigestion. It neutralises excess acid in the stomach.

antennae: the pair of fine probing feelers on the head of many invertebrates (e.g. flies, crabs) antibiotics: chemicals that kill bacteria or other microorganisms antibodies: chemicals produced by animals to fight some pathogens aqueous solution: a solution in which water is the solvent arteries: hollow tubes (vessels) with thick walls carrying blood pumped from the heart to other body parts arthropod: animal that has an exoskeleton, a segmented body and jointed legs (e.g. insects, crabs) assimilate: take in and process something. Living things assimilate substances. asthma: narrowing of the air pipes that join the mouth and nose to the lungs asteroid: one of the millions of rocky bodies that orbit the sun. Some asteroids are like tiny pebbles; others may be hundreds of kilometres in diameter. asteroid belt: the collection of asteroids that orbit the sun between Mars and Jupiter astronomy: the study of space, including stars, planets, comets and galaxies atmosphere: the layer of gases around the Earth atom: a very small particle that makes up all things. Atoms have the same properties as the objects they make up. attract: a pull towards another object auditory nerve: a large nerve that sends signals to the brain from the hearing receptors in the cochlea axis: an imaginary line running through the centre of the object, about which it rotates axle: the central part around which a wheel turns backdraught: explosive burning of hot gases that occurs after air enters a room that is poorly ventilated because of a fire bacteria: the smallest life form found on Earth. Some types of bacteria are responsible for decay and disease. balanced: describes forces that are equal but act in opposite directions. Balanced forces cancel each other out. ball and socket joints: joints where the rounded end of one bone fits into the hollow end of another ball bearings: steel balls inserted into the hub of a wheel that help the wheel roll around the axle, rather than slide over it. The rolling motion of the ball bearings helps to reduce friction. bar graph: a diagram using the lengths of rectangles (bars) to show the size of the same property for different objects or at different times. The bars may be horizontal or vertical; also called a column graph. barred spiral galaxy: a type of spiral galaxy in which the central disk is replaced by a bar-shaped middle, with arms spiralling out from either end of the bar

Glossary 543

basalt: a dark, igneous rock with small crystals formed by fast cooling of hot lava. It sometimes has holes that once contained volcanic gases. base: a chemical that reacts with an acid to produce a salt and water. Edible bases taste bitter. batholith: intrusive rock mass that measures more than 100 kilometres across batteries: two or more electric cells connected in series beaker: container for mixing or heating substances beam balance: an accurate measuring scale used in the science laboratory bicuspid: a type of valve with two cusps (points). The valve between the heart’s left atrium and left ventricle is a bicuspid valve. Big Bang: the theory that describes how the universe formed. The theory says that the universe formed when a small space exploded about 13 billion years ago. bile: a substance produced by the liver that helps digest fats and oils binary fission: reproduction by the division of an organism (usually a single cell) into two new organisms binocular microscope: a microscope with two eyepieces, so you use both eyes to look at the object biologist: a scientist who studies living things biomechanics: the study of how animals, including humans, move biomechanist: a scientist who studies how people move biotic factors: the living things (organisms) in an ecosystem black hole: a very dense star that has a very strong gravitational pull bladder: sac that stores urine blood pressure: measures how strongly the blood is pumped through the body’s main arteries blood vessels: the veins, arteries and capillaries through which the blood flows around the body boiling: the change of state from a liquid to a gas. Boiling occurs when the entire liquid is heated and continues until the liquid turns completely into a gas. boiling point: the temperature at which a liquid changes to a gas bolus: round, chewed-up ball of food made in the mouth that makes swallowing easier bonds: forces that hold particles of matter, such as atoms, together bone marrow: a substance inside bones in which blood cells are made brass: an alloy made from a mixture of copper and zinc breathing: movement of muscles in the chest causing air to enter the lungs and the altered air in the lungs to leave. The air entering the lungs contains more oxygen and less carbon dioxide than the air leaving the lungs.

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Glossary

brittle: describes a material that shatters when it is hit bronchioles: small branching tubes in the lungs leading from the two larger bronchioles to the alveoli bronze: an alloy that is a mixture of copper and tin bryophytes: plants that do not contain vascular tissue Bunsen burner: a device that burns gas, producing a hot flame; used to heat or burn objects in the laboratory buoyancy: the upward push of water or any other fluid on a submerged or partly submerged object burning: combining a substance with oxygen in a flame bushfire: a large, uncontrolled fire in bushland calcium: a fairly reactive metal that is not found by itself in the body, but as part of many important substances, such as cartilage and bones calculus: the branch of mathematics concerned with the measurement of quantities that are continually changing calorimeter: a device designed to measure the amount of heat released when a substance burns cancer: a disease resulting in the uncontrolled growth of body cells, forming tumours canines: sharp, pointed teeth used for tearing and ripping food capillaries: minute tubes carrying blood to body cells. Every cell of the body is supplied with blood through capillaries. capture–recapture: a method used to estimate the number of organisms in an area. Individuals are captured and marked on a first visit, and this is compared with the number recaptured on a second visit. carbohydrates: organic substances, such as sugars and starch, that are made up of carbon, hydrogen and oxygen and contain useful chemical energy carbon dioxide: a gas in the air produced by respiration and used by plants as part of photosynthesis. The burning of fossil fuels releases carbon dioxide. carcinogens: chemicals that tend to produce cancer in the body cardiac muscle: special kind of muscle in the heart that never tires. It is involved in pumping blood through the heart. carnivore: animal that eats other animals cartilage: a waxy, whitish, flexible substance that lines or connects bone joints or, in some animals such as sharks, replaces bone as the supporting skeletal tissue. The ears and tips of noses of people are shaped by cartilage. cell: the smallest unit of life. Cells are the building blocks of living things. There are many different sized and shaped cells in animals and plants, as well as single-celled organisms. cell membrane: a structure that encloses the contents of a cell and allows the movement of some materials in and out cell sap: the mixture of water, dissolved substances, food and waste material found in the vacuoles of plant cells

cell wall: a wall around the cell membrane in plant cells providing a tough extra covering that gives strength and support to the plant cell cellulose: the cell walls of plants are made of this centre of gravity: the point of a body where the weight would be concentrated if the body were a single point centrifuging: separating a mixture by rotating the container quickly. The heavier parts of the mixture move to the outside of the spinning container. Cream is removed from milk by centrifuging. cerci: a pair of movement detectors at the rear of many insects. They may look like antennae. charge: (noun) a property of all objects. Charge can be positive or negative. There are some particles inside an atom that have no charge; (verb) to give an object an overall electric charge by adding or removing negative charges. Objects can be charged by rubbing. charged: describes an object that has more of one type of charge than the other chemical engineer: a scientist who combines chemistry and engineering to select materials to develop new products chemical reaction: a chemical change in which one or more new chemical substances is produced chemical symbol: the standard way that scientists write the names of the elements, using either a capital letter or a capital followed by a lowercase letter, for example, carbon is C and copper is Cu chemist: a scientist who studies how substances react with other substances chlorine: element added to a water supply to kill harmful micro-organisms chlorophyll: the green-coloured chemical in plants that absorbs the light energy used in photosynthesis, which makes food from carbon dioxide and water chloroplast: oval-shaped organelle found only in plant cells. Chloroplasts contain the pigment chlorophyll. They are the ‘factories’ in which carbon dioxide and water are changed by sunlight and water into food by the process of photosynthesis. cilia: hair-like tips on cells. The cilia that line your windpipe and lungs help stop germs, dust and fluid getting to your lungs. circulatory system: the body system that circulates oxygen in blood to all the cells of the body. The circulatory system consists of the heart, the blood vessels and blood. classifying: placing organisms or objects into groups based on common characteristics clouds: visible collections of small water droplets in the air high above the ground coal: a sedimentary rock formed from dead plants and animals that were buried before rotting completely

cochlea: the snail-shaped part of the inner ear. It is lined with tiny hairs that are vibrated by sound and stimulate the hearing receptors. collaboration: working together for shared benefit colloid: a mixture in which extremely small particles of one substance are spread evenly throughout another substance colourfast: of fixed or lasting colour column graph: a diagram using the lengths of rectangles (bars) to show the size of the same property for different objects or at different times. The bars may be horizontal or vertical; also called a bar graph. combustion: the process of combining with oxygen, most commonly burning with a flame comet: a body composed of rock, dust and ice. When close to the sun, it has a tail that points away from the sun. commensal: describes a species that benefits from its relationship with another species without harming the other species commensalism: relationship between organisms where one benefits and the other is unaffected compact bone: the hard shell of a bone. The minerals it contains give it strength. complex carbohydrates: organic substances such as cellulose and starch. These are made up of long chains of carbon, hydrogen and oxygen and are very strong. component: an object placed in a circuit, for example, a globe or switch compound: two or more different types of atoms that have been joined (bonded) together compressed: squeezed into a small space. Gases can be compressed, but liquids and most solids cannot be compressed. compressions: the processes of pushing a material into itself conclusion: what was found out in an investigation. It is a general statement that sums up a number of observations or the results of an experiment. The conclusion of an experiment relates to the stated aim. condensation: a change in state from a gas to a liquid; can occur when gas comes into contact with a cold surface condense: change state from gas to liquid conducting path: connected series of materials along which an electric current can flow conducting tissue: a type of tissue in the roots, stems and leaves of plants that transports substances from one part of the plant to another. The two types of conducting tissue are xylem and phloem. conduction: transfer of heat through collisions between particles conductor: material that allows electric charge to flow through it

Glossary 545

conglomerate: sedimentary rock containing large particles of various sizes cemented together constellation: group of stars that has been given a particular name because of the shape the stars seem to form in the sky when viewed from the Earth constipation: a condition of the bowels, caused by lack of dietary fibre, in which solid wastes cannot easily leave consumer: organism that relies on other organisms for its food contact force: a force that acts only between objects that are touching contaminated: describes a useful substance that contains one or more other substances that affect its use contract: become smaller in size control: a parallel experiment where everything is the same as the test set-up except the variable. It is used to ensure that the result is due to the variable and nothing else. controlled variables: the conditions that must be kept the same throughout the experiment controlling variables: the process of ensuring that all conditions, except one (the experimental variable), that could affect the results of an experiment are kept the same convection: transfer of heat through the flow of particles corona: the sun’s bright, hazy atmosphere. It is only obvious when there is a total eclipse. You must never look at the sun even for a brief moment. You could permanently damage your eyes. corrosion: a chemical reaction that wears away a metal. Air, water or chemicals in air and water, as well as many household substances, can be corrosive. Many acids and other corrosive substances are dangerous. corrosive: describes a chemical that wears away the surface of substances, especially metals cosmonaut: the Russian term for astronaut cotyledons: special leaves of the embryo plant inside a seed that provide food for the developing seedling criteria: properties of a field cross-pollination: transfer of pollen from stamens of one flower to the stigma of a flower of another plant of the same type crust: the outer layer of the Earth, made mostly of solid rock cusp: ridge or point on the surface of molars and premolars cyanobacteria: single-celled organisms known as blue–green algae. They are related to bacteria rather than algae and belong to the Kingdom Prokaryotae Monera. cyclone: a weather formation that starts over water and intensifies as a result of very low pressure, air temperature greater than about 27 °C and average wind speed higher than 60 km/h cytoplasm: the jelly-like material inside a cell. It contains many organelles such as the nucleus and vacuoles.

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Glossary

data: observations or measurements made and recorded during an investigation data sensor: device that measures and sends information to the data logger to which it is connected data type: the type of information to be recorded, such as numbers database: an organised collection of information decanting: pouring liquid off the top when sediment has settled to the bottom of the container decibel (dB) scale: a scale used to measure the sound level or loudness of sound, in decibels (dB) decomposers: small organisms that break down dead and decaying matter decomposition: breaking up of a substance into smaller parts deep water currents: complex currents that move in the depths of the oceans below about 400 metres, which is about 90% of the ocean’s water. The other 10% experiences surface currents. deficiency disease: disease caused by the lack of a vitamin or mineral deforestation: the removal of trees from the land dehydration: loss of water from the body denitrifying bacteria: bacteria in the soil that chemically change useful nitrate compounds into poisonous nitrites and ammonia gas density: the number of a species living within an area dentine (or dentin): bone-like material that gives the tooth its shape deoxygenated: describes blood from which some oxygen has been removed dependent variable: a variable that is expected to change when the independent variable is changed. The dependent variable is observed or measured during the experiment. deposition: the laying down of weathered rock particles and soil by rivers, wind, oceans and glaciers depression: area of low air pressure that develops where warmer air is rising from the Earth’s surface. As this warmer air cools, it allows cloud to form; so, a depression or low pressure system usually brings rain and strong winds. dermis: the medical name for the deeper part of the skin description: information about a field in a database diagnose: to identify a disease or condition diamond: colourless, sparkling crystal valued in jewellery for its beauty. It is a three-dimensional arrangement of carbon atoms that differs from the layers in graphite. diaphragm: flexible, dome-shaped, muscular layer separating the chest and the abdomen. It is involved in breathing. diastolic pressure: the lower blood pressure reading during relaxation of the heart muscles

diatom: microscopic organism, consisting of one cell, that lives in water. It belongs to Kingdom Protista, but has plant-like features (e.g. it contains chlorophyll). dichotomous key: a diagram used to classify things, by grouping them into smaller and smaller groups that are more and more alike, based on choosing one of two features diffuse: spread throughout another substance diffusion: the spreading of one substance through another due to the movement of their particles disperse: scatter dissolved: describes a substance that has mixed completely with a liquid so that it is no longer visible. Dissolving requires the substance to separate into very small particles. distillate: the liquid collected during distillation when the evaporated substance condenses distillation: a separation technique that uses evaporation to separate substances. The mixture is heated so that one substance evaporates. The vapour is collected and condenses into a liquid. distilled water: pure water collected by condensing steam distribution: the area inhabited by a plant or animal species divided bar graph: a type of bar graph in which the bars are divided into sections to represent parts of a whole domain: a ‘mini-magnet’ found in magnetic materials drag: the force that acts on an object moving against air or water dry cells: devices containing chemicals as solids and pastes that react to supply an electric charge ear canal: the tube that leads from the outside of the ear to the eardrum eardrum: a thin piece of stretched skin inside the ear that vibrates when sound waves reach it echolocation: the use of sound to locate objects by detecting echoes ecliptic: the path that the sun moves along each year ecology: the study of the way in which organisms interact with other organisms and with their environment ecosystem: community of living things that interact with each other and with the environment in which they live electric circuit: the path that electrons flow along. Electrons require a closed path of conductors for electricity to flow. electric current: a measure of the number of electrons flowing through a circuit every second. An increase in current means an increase in the rate of flow of electrons in the circuit. electrocardiogram (ECG): graph made using the tiny electrical impulses generated in the heart muscle, giving information about the health of the heart electrodes: conductors through which an electric current enters or leaves an electric cell

electrolyte: acid, base or salt that conducts electricity when dissolved in water or melted electromagnet: a magnet formed by wrapping a coil of wire around an iron core. When electricity passes through the coil, the iron core becomes magnetic. electromagnetic spectrum: energy radiated as electric and magnetic fields that can travel through space from the sun. There are many different types of electromagnetic energy, such as light, microwaves and radio waves. electron: negatively charged, very light particle of an atom. Electrons move around the central nucleus of the atom. electron microscope: instrument for viewing very small objects. An electron microscope is much more powerful than a light microscope and can magnify things up to a million times. electronic scales: device for measuring mass, in grams (g) and kilograms (kg) electrons: negatively charged, very light particles of an atom. Electrons move around the central nucleus of the atom. electrostatic force: a non-contact force of electric charges at rest. We experience electrostatic forces when we pull off a jumper and our hair stands on end. element: pure substance made up of only one type of atom elliptical galaxy: an oval or egg-shaped galaxy embryo: group of cells formed from the zygote and developing into different body organs emphysema: condition in which the air sacs in the lungs break open and join together, reducing the amount of oxygen taken in and carbon dioxide removed emulsify: combine two liquids that don’t normally mix easily emulsion: a colloid with droplets of one liquid spread evenly through another enamel: hard substance that covers the outside of the tooth and protects the dentine endoskeleton: skeleton or shell inside the body endosperm: food supply for the embryo plant in a seed endothermic: chemical reactions that absorb heat energy from the surroundings, causing the reactants to drop in temperature energy: the ability to make something happen, such as moving something, making a light glow or making a noise engineer: a person who uses designs or scientific ideas to design and build devices or structures or new technology for a useful purpose and make it work enhanced greenhouse effect: the increase in the Earth’s temperature caused by humans adding more carbon dioxide and other heat-trapping gases to the air environment: the living and non-living things that affect organisms in a particular place: that is, the surroundings of a living thing enzymes: special chemicals that speed up reactions but are themselves not used up in the reaction

Glossary 547

epicormic bud: a bud under the bark of a tree that sprouts after a fire epidermal cells: flattened type of cells that protect the top and bottom surface of leaves. Stems and roots also have an outer ring of these cells for protection. epidermis: outermost layer of the skin epiglottis: leaf-like flap of cartilage behind the tongue that closes the air passage during swallowing epiphytes: plants that use other plants for support but not for food epithelial tissue: the lining cells that form the outside or inside surfaces of a plant or animal erosion: the process of moving weathered rock or soil from one place to another evaporate: change state from liquid to gas evaporation: a change in state from liquid to gas. Evaporation occurs only from the surface of the liquid. excrete: remove wastes from the body exoskeleton: skeleton or shell that lies outside the body exosphere: the outer region of the Earth’s atmosphere where it meets space exothermic: describes chemical reactions that get hot because they generate heat expand: increase in size due to the movement of particles in a substance extinct: describes volcanoes that are no longer active. Extinct volcanoes have not erupted for thousands of years and show no sign of future eruption. extrapolation: use of a graph to determine unmeasured data values beyond the range of measured data values extrusive rock: igneous rock that forms when lava cools above the Earth’s surface eye: the central low-pressure region of a cyclone. There is very little wind in the eye of a cyclone. faeces: waste products released by animals in solid form fair test: a method for determining an answer to a problem without favouring any particular outcome: another name for a controlled experiment fat: an organic substance that is solid at room temperature and is made up of carbon, hydrogen and oxygen fat soluble: describes a substance able to dissolve in fat fault: a break in a rock structure. The rock on either side of the break can move. fertilisation: penetration of the ovum by a sperm fertilised: an egg cell is fertilised when a male sex halfcell enters it. In animals, the male sex cell is the sperm; in plants, it is contained in the pollen. A fertilised egg eventually grows into a new organism. fever: a symptom of illness in which the body experiences very high temperatures

548

Glossary

fibre: a chemical substance produced by plants. It is made up of very large molecules. field: in a database, type of information recorded in a column for each record filament: the male part of a flower that holds up the anther; also the coil of wire made from a metal that glows brightly when it gets hot. The filaments in light globes heat up when electricity flows through them. filter: a device that allows some materials to pass through. It blocks particles too large to fit through the holes or pores. filter funnel: used with filter paper to separate solids from liquids filtrate: the liquid or particles that pass through a filter filtration: a separation technique that separates objects of different sizes flammable: describes substances such as methylated spirits that burn easily fire intensity: a measure of how quickly heat is released from a fire flat file database: a simple database with a single table floatables: substances that are less dense than water so can float on water floc: a clump of particles heavy enough to sink to the bottom rather than remain floating in a liquid flocculation: the process of adding a chemical to a suspension to create flocs, which settle to the bottom fluid: a substance that flows and has no fixed shape. Gases and liquids are fluids. fluoride: substance added to a water supply to help prevent tooth decay fog: a visible collection of small water droplets in the air at ground level folding: the buckling of rocks. It is caused when rocks are under pressure from both sides. food chain: diagram that shows how the energy stored in one organism is passed to another. food web: diagram showing several food chains joined together to demonstrate that animals eat more than one type of food force: (noun) a push, pull or twist. Forces are measured in newtons (N). (verb) to push, pull or twist fossil fuel: substance, such as coal, oil and natural gas, that has formed from the remains of ancient organisms. Coal, oil and natural gas are often used as fuels; that is, they are burnt in order to produce heat. fracture: in relation to identifying minerals from their properties, a mineral’s fracture describes the appearance of the break when a sample of the mineral is snapped freezing: change of state from liquid to solid frequency: the number of vibrations each second

friction: a force that acts against the movement of an object. It occurs between any surfaces that are touching and trying to move past each other. fruit: ripened ovary of a flower, enclosing seeds fuel: a substance that is burnt in order to release energy, usually in the form of heat fungi: organisms, such as mushrooms and moulds, that help to decompose dead or decaying matter Gaia: a theory that the Earth’s physical environment and living creatures have developed together over a very long time; named after the Greek goddess of Mother Earth galaxy: a very large group of stars held together as a system by gravity galvanising: protecting a metal by covering it with a more reactive metal that will corrode first gas: state of matter with no fixed shape or volume gas giant: a large planet mostly made up of gas. Jupiter is a gas giant. geologist: a scientist who studies the structure of the Earth, especially its rocks germinate: grow a plant from a seed germination: first sign of growth from the seed of a plant global positioning system (GPS): a system that gives your location in longitude and latitude at the touch of a button global warming: an increase in the Earth’s temperature over a period of many years glucose: a simple carbohydrate and the simplest form of sugar granite: a hard, igneous rock with different coloured crystals large enough to see. It forms slowly below the Earth’s surface. graphite: a black form of carbon easily rubbed onto other substances gravitational attraction: an attraction that exists between any two bodies in the universe that have mass gravitational energy: type of energy from the Earth’s gravitational force that causes objects above the ground to fall to Earth. The higher an object, the more gravitational energy it has. gravity: the force of attraction that exists between any two bodies in the universe that have mass. The gravity at the Earth’s surface is the pull on objects near its surface towards the centre of the Earth. greenhouse effect: a natural effect of the Earth’s atmosphere trapping heat, which keeps the Earth’s temperature stable. The sun’s energy passes through the atmosphere and warms the Earth. Heat energy radiated from the Earth cannot pass through the atmosphere and is trapped. greenstick fracture: a break that is not completely through the bone, often seen in children ground water: rainwater that has soaked into the lower levels of the soil and has saturated the soil

groyne: a jetty built into the sea to prevent the erosion of the beach guard cells: cells on either side of a stoma that work together to control the opening and closing of the stoma gum: the firm flesh in which the teeth are set gyres: ocean currents that have formed circular patterns over large areas of water between continents. Gyres move anticlockwise in the Southern Hemisphere and clockwise in the Northern Hemisphere. habitat: the place where an organism lives haemoglobin: the red pigment in red blood cells that carries oxygen hardness: a property of a mineral that can be found using Mohs’ hardness scale. For example, if a mineral sample can be scratched by a piece of quartz but not by orthoclase, its hardness lies between 6 and 7. hearing loss: permanent damage to the ear affecting a person’s ability to hear sounds heartbeat: contraction of the heart muscle occurring about 60–100 times per minute heat: energy that moves from one place to another place that is at a lower temperature heatproof mat: surface that protects benches from damage by heat and chemicals herbivores: animals that eat only plants heresy: stating an opinion that goes against the orthodox teachings of a religion hertz: the unit of frequency. Abbreviation is Hz. One hertz is equal to one vibration each second. high pressure system (or high): an area of high air pressure that moves across the land, tending to bring fine weather, dry with very few clouds. Highs tend to move fairly slowly and cover a large area. hinge joints: joints in which two bones are connected so that movement occurs in one plane only histogram: a graph with equal intervals marked on the x-axis for the values of a quantity, and frequency of occurrence of each value shown by the height of adjoining columns histologist: a scientist who studies the cells and tissues that make up animals, including humans. Histologists look at small samples of cells and tissues under microscopes. homogenised milk: processed milk. The butterfat (oil) is broken up into droplets and spreads evenly through the rest of the milk. This milk is an emulsion, so the butterfat does not settle out. host: organism living in a relationship with another organism. The host supplies something needed by the other organism (called the parasite).

Glossary 549

humus: organic matter resulting from the decomposition of plant and animal tissue in the soil. Humus helps the soil hold water and mineral nutrients needed by plants. hydrogen: the element with the smallest atom. By itself, it is a colourless gas and combines with other elements to form a large number of substances, including water. It is the most common element in living things. hydrosphere: the water on the Earth’s surface hypothesis: a suggested explanation for past observations that is tested in an experiment immovable joints: joints that allow no movement except when absorbing a hard blow immune system: parts of the body involved in defending it against disease in series: connected one after the other so that the same current passes through each load. The positive end of one cell must be joined to the negative end of the next cell. incisors: teeth with straight, sharp edges that are used for biting and cutting food incubated: placed in a cabinet that maintains an optimum temperature for bacterial growth independent variable: the variable that the scientist changes to observe its effect on another variable indicator: a substance that changes colour when it reacts with acids or bases. The colour shows how acidic or basic a substance is. indigestion: a chemical reaction in the stomach related to difficulties in digesting food. Indigestion can cause discomfort, burping and stomach rumbling. industrial chemist: scientist who uses chemistry to create new materials, such as synthetic fibres infectious diseases: diseases that can be transferred from one organism to another inference: a logical explanation about what happened and why it happened influenza: a virus, also known as the ‘flu’, that can spread in droplets of mucus infra-red radiation: invisible radiation emitted by all objects. You feel infra-red radiation as heat. inner core: the solid centre of the Earth inorganic nutrients: chemical substances other than organic nutrients that are needed by living things insect-pollinated flowers: flowers that receive pollen carried on the body parts of insects from other flowers insoluble: unable to be dissolved insulator: material that does not allow heat to move through it intensification: a weather process that begins when moist, warm rising air meets colder air and the water vapour condenses into rain, making this upper air even colder. The warm air then rises faster and the winds spiralling into the low pressure system speed up.

550

Glossary

interpolation: use of a graph to determine unmeasured data values within the range of measured data values interstellar space: the space in between the stars outside our solar system intrusive rock: igneous rock that forms when magma cools below the Earth’s surface invertebrate: an animal without a backbone investigation: activity aimed at finding information involuntary muscles: muscles not under the control of the will; they contract slowly and rhythmically. These muscles are at work in the heart, intestines and lungs. ionosphere: the highest layer of the atmosphere where the air is spread extremely thin. This layer reflects radio waves, enabling communication between many parts of the Earth. irregular galaxy: a galaxy that has no particular shape irrigate: to water crops, especially when there is insufficient rainfall Jupiter: the largest of the planets, with 17 satellites kilogram: the unit in which mass is measured kinetic energy: energy due to the motion of an object laboratory: a room fitted with apparatus for scientific research land breeze: the breeze that occurs when differences in air pressure cause air particles to flow from the land towards the ocean landfill: an area set aside for the dumping of rubbish larvae: a stage in the life cycle of egg-laying animals. It is the stage after the egg hatches. latitude: a distance measured in degrees, north or south of the equator lava: a mixture of molten rock and gases that has reached the Earth’s surface from a volcano Law of Conservation of Energy: a law that states that energy cannot be made or lost. However, energy can be transformed from one type to another or transferred from one object to another. leaf litter: layer of dead leaves on the ground in a forest left atrium: upper left section of the heart where oxygenated blood from the lungs enters the heart left ventricle: lower left section of the heart, which pumps oxygenated blood to all parts of the body ligament: band of tough tissue that connects the ends of bones or keeps an organ in place light: radiation to which our eyes are sensitive, making it possible to see objects that emit or reflect it light microscope: instrument for viewing very small objects. A light microscope can magnify things up to 1500 times. lightning: the spark caused when built-up charges in a cloud discharge quickly to other clouds or the ground

lightning rod: conductive metal rod, often attached to the top of tall buildings. Lightning rods help to keep buildings safe from lightning strikes. lignin: a hard substance in the walls of dead xylem cells that make up the tubes carrying water up plant stems. Lignin forms up to 30% of the wood of trees. lignotuber: a lump on the roots of a tree that sprouts after a fire lime: compound (calcium hydroxide) added to a water supply to reduce acidity limestone: a sedimentary rock formed from the remains of sea organisms. It consists mainly of calcium carbonate. line graph: a graph made by plotting pairs of data as points and joining the points together, or drawing a line through the middle of the points, called the ‘line of best fit’ line transect: line placed across a community of organisms, which is used to measure their distribution and density lipases: enzymes that break fats and oils down into fatty acids and glycerol lipids: type of nutrient that includes fats and oils liquid: state of matter that has a fixed volume, but no fixed shape lithosphere: the outermost layer of the Earth; includes the crust and uppermost part of the mantle living: being alive or once alive. Living things have a number of features in common; for example, they reproduce, and require food and oxygen. load: device that uses electrical energy and converts it into other forms of energy; force, such as the weight of an object, resisting motion against which a lever works longitude: a distance measured in degrees, east or west from a defined place called the Prime Meridian. The Prime Meridian passes through a town called Greenwich (near London). low pressure system (or low): area of low air pressure that develops where warmer air is rising from the Earth’s surface. As this warmer air cools, it allows cloud to form; so, a low pressure system usually brings rain and strong winds. lub dub: the sound made by the heart valves as they close lubricant: substance with large particles that can slide easily over each other. Lubricants are used between surfaces that rub against each other to reduce wear and increase motion between the surfaces. luminous: releasing its own light lustre: describes how a mineral reflects light from its cut surface. Lustre may be described as dull, metallic, pearlescent, glassy, brilliant, waxy or silky. magma: a very hot mixture of molten rock and gases, just below the Earth’s surface, that has come from the mantle layer below the Earth’s outer crust

magnetic field: a map of lines showing the size and direction of a magnetic force. The size of the force is shown by how close together the lines are. The direction at any point is given by the direction in which the north pole of a magnet would face. magnetic force: the force (a push or pull) that acts between magnets (including the Earth) and magnetic objects magnetic North Pole: the place on Earth to which the north pole of a magnet is attracted magnetic South Pole: the place on Earth to which the south pole of a magnet is attracted magnification: the number of times the image of an object has been enlarged using a lens or lens system. For example, a magnification of two means the object has been enlarged to twice its actual size. magnify: to enlarge an object using a lens or lens system mantle: the thick layer inside the Earth, below the crust. Most of the mantle is solid rock, but the upper part is molten rock called magma. manufacturing processes: processes used to make products Mars: a small planet near Earth. Space probes have brought back samples from Mars. mass: the quantity of matter in an object (usually measured in grams or kilograms) massive: describes an object with a very large mass matter: anything that has mass and takes up space. The three main states of matter are solid, liquid and gas. measuring cylinder: used to measure volumes of liquids accurately melting: the change of state from solid to liquid melting point: the temperature at which a solid substance turns into a liquid (melts) or a liquid turns into a solid (freezes) meniscus: the curved upper surface of a column of liquid Mercury: the small planet nearest the sun mesosphere: the middle layer of the atmosphere, between the stratosphere and the thermosphere metal: element that conducts heat and electricity; shiny solid that can be made into thin wires and sheets that bend easily. Mercury is the only liquid metal. metalloids: elements that have the appearance of metals but not all the other properties of metals metamorphic rock: rock formed from another rock that has been under great heat or pressure (or both) metamorphism: the process that changes rocks by extreme pressure or heat (or both) meteor: the fiery streak of light from a meteoroid that has entered the Earth’s atmosphere from space and has become so hot that it burns meteorite: a fallen meteoroid that has reached the Earth’s surface

Glossary 551

meteoroid: small bodies of rock and/or metal travelling through space microbe: very small organism that can be seen only through a microscope micrographs: images produced by an electron microscope micron: unit of length, a thousandth of a millimetre microscope: an instrument for viewing small objects Milky Way Galaxy: the galaxy of which our solar system is a very small part millimetre: unit of length, a thousandth of a metre minerals: substances that make up rocks. Each mineral has its own chemical make-up. mineral salts: chemical compounds that occur naturally and belong to the group called salts. Many dissolve in water and contain elements that are essential for healthy plant or animal growth. mitochondria: small rod-shaped organelles that supply energy to other parts of the cell. They are usually too small to be seen with light microscopes. Singular: mitochondrion. mixture: a combination of substances in which each keeps its own properties Mohs’ hardness scale: scale developed by the geologist Friedrich Mohs; it consists of a comparative list of ten minerals arranged in order from softest (hardness value of 1) up to the hardest (10). A harder mineral scratches a softer mineral. molars: teeth with a large rough surface used for grinding food molecule: two or more atoms joined (bonded) together, forming a small particle monochloramine: a type of disinfectant added to the water supply to kill any dangerous bacteria or micro-organisms monocular microscope: a microscope in which the specimen is seen using one eye only moon: a body that naturally orbits a planet moulds: cavity in a rock that shows the shape of the hard parts of an organism; types of fungi found growing on the surface of foods mudstone: a fine-grained, sedimentary rock without layering multicellular: having many cells. Most plants and animals are multicellular. mutualism: relationship between two different organisms in which both benefit native elements: minerals in their pure form, for example, gold and diamonds natural fibres: fibre that forms naturally; that is, it has not been made by humans neap tide: a weaker high and low tide that occurs when the sun and moon are not in the same line as the Earth. At such times, the gravitational pull of the sun and the moon work against each other.

552

Glossary

nebula: a cloud of gas and dust particles that may come together and heat up to form a star nectary: gland secreting a sugary fluid negative electric charge: the charge on an atom or object with more electrons than protons negatively charged: having more electrons than protons (more negative charges than positive charges) Neptune: a small planet near the edge of the solar system, with an atmosphere of methane gas nerve cells: type of cell in the body designed to carry electrical impulses by which the nervous system functions neuropsychologist: a scientist who studies different areas of the brain to better understand brain functions such as memory and learning neutral: having the same number of protons and electrons neutron: tiny, but heavy, particle found in the nucleus of an atom. Neutrons have no electrical charge. newton (N): the unit for measuring forces nitrates: types of compounds called salts that contain the NO3 group, made up of three oxygen atoms bonded to one nitrogen atom nitrifying bacteria: bacteria that change dissolved ammonia into nitrite compounds, or nitrites into nitrate compounds nitrites: types of compounds called salts that contain the NO2 group, made up of two oxygen atoms bonded to one nitrogen atom nitrogen-fixing: changing nitrogen in the air into nitrogen compounds in the soil. Plants can’t use nitrogen gas from the air. They obtain nitrogen through their roots from nitrogen compounds in the soil. Nobel Prize: one of six international prizes awarded annually for outstanding achievement in physics, chemistry, medicine, literature, economics and the promotion of peace non-contact force: a force that acts between objects even though the objects are not touching non-infectious diseases: diseases that cannot be transferred from one organism to another non-living: not alive and never having been alive non-luminous: describes objects that do not emit their own light, but can be seen by reflected light non-metal: element that does not conduct electricity or heat. Non-metals melt and turn into gases easily and are brittle and often coloured. nucleus: the roundish structure inside cells that acts as the control centre for the cell. Plural: nuclei. nutrients: substances that provide energy and chemicals that living things need to stay alive, grow and reproduce observation: information obtained by the use of our senses or measuring instruments obsidian: a black, glassy rock that breaks into pieces with smooth shell-like surfaces

oil: an organic substance that is liquid at room temperature and is made up of carbon, hydrogen and oxygen omnivores: animals that eat plants and other animals optical telescope: a telescope that uses light to produce images of distant objects optimum range: the range, within a tolerance range for a particular abiotic factor, in which an organism functions best orbit: the path that an object follows when it moves all the way around another object, such as the path of the Earth around the sun organ: group of tissues working together to carry out a particular job organelle: small structure in a cell with a special function organism: living thing osmosis: the diffusion of water in or out of a cell ossicles: a set of three tiny bones that send vibrations from the eardrum to the inner ear. They also make the vibrations larger. ossification: hardening of bones osteoporosis: loss of bone mass that causes them to become lighter, more fragile and easily broken outer core: the liquid layer surrounding the solid inner core of the Earth oval window: an egg-shaped hole covered with a thin tissue. It is the entrance from the middle ear to the outer ear. ovary: the hollow, lower end of the carpel containing the ovules (the female egg cells) ovule: receptacle within an ovary that contains egg cells oxidation: chemical reaction involving the loss of electrons by a substance oxygen: a gas in the air (and water) that animals need to breathe in; made up of particles with two oxygen atoms. Plants produce oxygen as part of photosynthesis. oxygenated: describes the bright red blood that has been supplied with oxygen in the lungs oxyhaemoglobin: haemoglobin with oxygen molecules attached ozone layer: a layer in the stratosphere, about 25 km above Earth, that has high concentrations of ozone gas. The ozone layer absorbs over 90% of the sun’s ultraviolet light. pacemaker: electronic device inserted in the chest to keep the heart beating regularly at the correct rate. It works by stimulating the heart with tiny electrical impulses. palaeontologist: a scientist who studies fossils paper chromatography: method of separating a mixture of different colours. The liquid soaks through the paper and carries the mixture with it. Some substances in the mixture are carried through the paper faster than others so the substances are separated along the paper. paper mill: place where paper products are manufactured

parallax error: the error that occurs when scales are read inaccurately from an angle parallel circuit: circuit that has more than one path for electricity to flow through. If one of the paths has a break in it, the others will still work. paralysis: loss of the ability to move parasite: organism that lives in or on another organism. The parasite benefits while usually harming the host organism. parasitism: an interaction where one species (the parasite) lives in or on another species (the host) from which it obtains food, shelter and other requirements particle model: a description of the moving particles that make up all matter and how they behave. The model explains the properties of solids, liquids and gases. pathogen: disease-causing organism penicillin: substance, first extracted from moulds, that kills many types of bacteria. It was the first antibiotic drug. penumbra: the lighter, outer part of a shadow peristalsis: the process of pushing food along the oesophagus or small intestine by the action of muscles permanent magnet: a magnet that retains its magnetic effect for many years petals: the coloured parts of a flower that attract insects Petri dish: a shallow, circular glass dish, often used in the laboratory for growing bacteria pH scale: scale from 1 (acidic) to 14 (basic) that measures how acidic or basic a substance is pharmaceutical industry: an industry that manufactures medicines and other medical treatments pharmacology: the study of the effect of drugs on living things phloem: type of tissue that transports sugars made in the leaves to other parts of a plant phloem cells: long, narrow, living cells that are joined together to form long tubes in a plant. The tubes move the food made in the leaves to other parts of the plant, such as the roots and storage areas. phosphorus: a substance that plays an important role in almost every chemical reaction in the body. Together with calcium, it is required by the body to maintain healthy bones and teeth. photosynthesis: the food-making process in plants that takes place in chloroplasts within cells. The process uses carbon dioxide, water and energy from the sun. photosynthesise: describes a plant’s ability to use carbon dioxide, water and the sun’s energy to make food physicist: a scientist who studies the laws of nature physiologist: a scientist who studies how the parts of living things work together physiology: a study of how the parts of living things work together

Glossary 553

physiotherapist: a person who treats body weaknesses through massage and exercise pie chart: a diagram using sectors of a circle to compare the size of parts making up the whole pitch: the highness or lowness of a sound. The pitch that you hear depends on the frequency of the vibrating air. pivot joint: joint that allows a twisting movement planet: a large object that orbits a star. Planets do not produce their own light. plankton: microscopic animals and plants that float in sea water plasma: the yellowish, liquid part of blood that contains water, minerals, food and wastes from cells plastic: synthetic substance capable of being moulded platelets: small bodies involved in blood clotting. They are responsible for healing by clumping together around a wound. plumule: small bud at the tip of the embryo plant in a seed plutonic rocks: igneous rocks that form when magma cools below the Earth’s surface; also called intrusive rocks poles: two areas of a magnet (the north and south poles) where the magnetic force is the strongest pollinate: transfer pollen from the stamen (the male part) of a flower to the stigma (the female part) of a flower pollination: transfer of pollen from the stamen (the male part) of a flower to the stigma (the female part) of a flower polymer: substance made by joining smaller identical units. All plastics are polymers. pore: small opening in the skin. Perspiration reaches the surface of the skin through pores. positive electric charge: the charge on an atom or object with fewer electrons than protons positively charged: having more protons than electrons (more positive charges than negative charges) post-mortem: examination carried out on a body by a pathologist if the cause of a person’s death is unclear potential energy: energy that has the potential to do work and so the energy is ‘stored’, such as gravitational energy, elastic energy and chemical energy power supply: a device that can provide an electric current precipitate: solid product of a chemical reaction that does not dissolve in water predators: animals that hunt other animals for food premolars: teeth with two points that roll and crush the food pressure: a push or squeeze on an object prey: animal hunted by other animals for food primary key: a field which links two or more tables in a database proboscis: a long feeding tube attached to the head of some insects. It sometimes rolls up when not in use.

554

Glossary

processed food: packaged food that has been altered by cooking and adding chemicals to it producers: organisms, such as plants, that use photosynthesis to make their own food from the sun’s energy product: new chemical substance that results from a chemical reaction properties: characteristics or features of an object or substance proteases: enzymes that break proteins down into amino acids protein: chemical made up of amino acids needed for the growth and repair of the cells in living things proton: tiny, but heavy, particle found in the nucleus of an atom. Protons have a positive electrical charge. pulp: the part of the tooth that contains the nerves and blood vessels pulse: alternating contraction and expansion of arteries due to the pumping of blood by the heart pumice: a pale rock that forms when frothy lava cools in the air. Pumice often floats on water as it is very light and full of holes that once contained gas. quadrat: a sampling area, often one square metre, in which the number of organisms in that area is counted and recorded qualitative: type of observation that describes what is seen quantitative: type of observation where a measurement with a specific value is used quarks: small particles that combine in different ways to make up protons and neutrons query: a request for information from a database radiant heat: heat that is transferred from one place to another by radiation radiation: a method of heat transfer that does not require particles to transfer heat from one place to another radicle: root of the embryo plant in a seed radio telescope: a telescope that uses a huge dish, or a collection of smaller dishes, to pick up radio waves (not light waves) from distant stars and galaxies radio waves: a type of energy that is created when electric and magnetic fields move together rarefactions: in sound waves, the layers of air particles that are spread apart (between compressions) reactant: chemical substance used up in a chemical reaction. Some chemical bonds in a reactant are broken during the reaction. receptors: special cells that detect energy and convert it to electrical energy that is sent to the brain record: a collection of information about one object in a row of a database recycling program: a program often run by local councils to collect recyclable materials from people’s homes

red blood cells: living cells in the blood that transport oxygen to all other living cells in the body. Oxygen is carried by the red pigment, haemoglobin. red giant: a star in a late stage of its life. Helium atoms in the core fuse to form carbon and other heavier elements. It retains its ‘burning’ hydrogen shell. The star’s size increases because the outward push of the nuclear reactions inside it is greater than the inward pull of gravity. This expansion allows the star to radiate more energy so its surface cools to a red colour. refine: restrict a search reflected: bounced off relative dating: comparing the ages of rocks without actually knowing their ages in years reliable: describes consistent results obtained from repeated experiments repel: push away repulsion: a push away from another object residue: the material left behind when a mixture is filtered respiration: the chemical process that takes place in every cell to release energy. Glucose reacts with oxygen to produce carbon dioxide and water. reverberation: the longer lasting sound caused by repeated reflection from hard surfaces right atrium: upper right section of the heart where deoxygenated blood from the body enters right ventricle: lower right section of the heart, which pumps deoxygenated blood to the lungs rigid: stiff, not flexible rock salt: a sedimentary deposit formed when a salt lake or seabed dries up. Its main chemical is sodium chloride. root canal: the channel through which the nerves and blood vessels of the teeth go into the jawbone root hairs: tube-like outgrowths of cells on the surface of roots. They have thin walls, which allow water and dissolved substances to move into the root. rotate: turn around on an axis rust: a brown substance formed when iron reacts with oxygen and water rusting: the corrosion of iron safety glasses: plastic glasses used to protect the eyes during experiments saliva: watery substance in the mouth that moistens food before swallowing saltfall: a process in which salt water from the ocean evaporates into the atmosphere and returns to the land’s interior as rain sample size: the number of organisms used in an experiment. Reliable experiments have a large sample size.

sandstone: a sedimentary rock with medium-sized grains. The sand grains are cemented together by silica, lime or other salts. saprophytes: organisms that eat dead and decaying plant and animal material satellite: an object that orbits another object. The moon is the Earth’s satellite. Scientists have made and launched many artificial satellites. Saturn: a large planet famous for the rings of material around its equator scavengers: animals that eat dead plant and animal material scientists: people skilled in or working in the fields of science; scientists use experiments to find out about the material world around them scoria: a dark, igneous rock formed from gassy lava that cools quickly sea breeze: the breeze that occurs when differences in air pressure cause air particles to flow from the ocean towards the land search: the use of a computer to find information in a database sector graph: a diagram using sectors of a circle to compare the size of parts making up the whole sediment: the material that collects when suspensions are left to stand. Insoluble substances that collect at the bottom of a container are sediments. sedimentary rocks: rocks formed from sediments deposited by water, wind or ice. The sediments are cemented together in layers, under pressure. seed: product of a fertilised ovule seed coat: the protective layer around a seed seedling: young plant produced from the embryo in a seed after germination self-pollination: transfer of pollen from the flower’s own stamen to its stigma semilunar: a type of valve which is half-moon shaped. The aortic valve is semilunar and is located between the heart’s left ventricle and aorta. sensor: device connected to an instrument such as a data logger that measures and sends information separate: to divide into parts separating funnel: a pear-shaped glass container, with a tap at its base, used to separate two liquids that do not mix. Opening the tap removes the bottom liquid and the liquid floating on top is left in the funnel. separation: the process of dividing a mixture into its parts septic tank: a sewage treatment system placed underground in backyards of houses not connected to town sewage treatment plants series circuit: a circuit with the components joined one after the other in a single continuous loop

Glossary 555

sewage: a mixture of water and substances that flow from laundries, bathrooms, kitchens and toilets sewerage: the system of drains and pipes that takes sewage away from a property sextant: an instrument used to measure the height of an object above the horizon in order to calculate its latitude shale: a fine-grained rock formed in layers by the consolidation of clay show: display sieving: separating particles of different sizes by allowing the smaller particles to fall through holes in a container siltstone: a sedimentary rock with a particle size between that of sandstone and mudstone simple carbohydrates: organic substances such as glucose and sucrose. These are made up of short chains of carbon, hydrogen and oxygen. solar energy: energy sent out into space from the sun solar system: our Sun and everything that orbits it, including the eight planets (including Earth), the planets’ moons, asteroids and comets solid: state of matter that has a fixed shape and volume solubility: a property of a substance that describes how quickly it dissolves. Substances with different solubilities dissolve at different rates. soluble: able to be dissolved solute: a substance that is dissolved in a solvent to form a solution solution: a mixture of a solute dissolved in a solvent. Solutions are transparent (clear) but may be coloured. solvent: a substance in which a solute dissolves to form a solution sonar: the use of reflected sound waves to locate objects under water sound waves: vibrations of particles in the air space probe: an unmanned spacecraft that sends information back to Earth space shuttle: a spacecraft with a plane-like orbiter that can be reused. It is made up of the orbiter (the part which returns to Earth), liquid fuel tank and solid rocket booster. space station: a large manned base in space where astronauts can live for some months. Many experiments are performed there because gravity has no effect inside an orbiting spacecraft. species: a group of living organisms capable of interbreeding with each other but not with members of other species spiracles: small openings in the body through which some animals breathe. All insects have spiracles. spiral galaxy: a galaxy that has a dense centre of old stars, and arms that contain stars, dust, planets and gases that curve around the centre in a spiral shape

556

Glossary

spongy bone: bone tissue with a lattice-like structure that is less dense than compact bone spore: a reproductive cell of some organisms (e.g. ferns and fungi) that is protected within the organism until the time is ready for it to be released sports psychologist: someone who studies how athletes train their minds to help produce greater success in the sports arena sports psychology: the study of how athletes train their minds to help produce greater success in the sports arena spring tide: very high tide that occurs when there is a new or full moon. At such times, the Earth experiences the combined gravitational attraction of the sun and the moon because all three bodies are in a straight line. stamen: male part of the flower; includes the anther (containing the pollen) and the stalk to which it is attached (the filament) star: a ball of gas that gives off heat and light. The heat and light result from nuclear reactions that happen inside the atoms of the gases. starch: a complex carbohydrate that stores energy in plants static electricity: a build-up of charge in one place steel: an alloy made from combining carbon and iron stereo microscope: a microscope in which the specimen is seen using both eyes stigma: the female part of a flower, at the top of the carpel, that catches the pollen during pollination stomata: small openings located mainly on the lower surface of leaves. These pores are opened and closed by guard cells. Singular: stoma. stratosphere: the second layer of the atmosphere up to about 55 km above the Earth’s surface, between the troposphere and the mesosphere streak: the colour and texture of the mark that a mineral leaves behind when it is scratched across a hard white surface streamlined: shaped so that drag through a fluid is minimised sublimation: the change in state from a solid into a gas without first becoming a liquid (or from a gas into a solid without first becoming a liquid) substance: something made of matter sugars: simple carbohydrates that contain carbon, hydrogen and oxygen. Glucose and sucrose are sugars. supergiants: a very large type of star that is expanding while running out of fuel, and will eventually explode supernova: a huge explosion that happens in the life cycle of super-giant stars surface currents: ocean currents that affect the surface above about 400 metres, which is about 10% of the ocean’s water. The other 90% experiences deep water currents. surface protection: coating over a metal surface to prevent corrosion

surface tension: the ‘firmness’ of the surface of a liquid created by the attraction between particles at the surface. The surface acts like an elastic skin. suspended: hanging, not falling or sinking suspension: a mixture of a gas or liquid and an insoluble substance. The insoluble substance settles to the bottom when the mixture is left to stand. sweat gland: tiny, coiled tube in the skin through which water and salt are removed from the body, helping to control body temperature symbiosis: very close relationship between two organisms of different species. It may benefit or harm one of the partners. synovial fluid: the liquid inside the cavity surrounding a joint. It helps bones to slide freely over each other. system: several organs working together to make up a system. For example, the brain and spinal chord make up the central nervous system. systolic pressure: the higher blood pressure reading during contraction of the heart muscles table: the basis of a database, consisting of information in fields and records telescope: an instrument used for looking at and detecting far away objects temperature: a measure of how hot or cold a substance is. It is measured in degrees Celsius. temporary magnet: a magnet that stays magnetic only while it touches a permanent magnet, or one that is magnetic for a very short time terminal: the points where electrons enter and leave a battery or other electrical device. Electrons leave from the negative terminal and return to the positive terminal. terrestrial planet: Earth-like planet that is small and solid test tube: thin glass container for holding, heating or mixing small amounts of substances test-tube baby: baby resulting from fertilisation of an egg by sperm in the laboratory thermometer: instrument used to measure temperature. Most school thermometers contain alcohol that is dyed red. As the temperature rises, the alcohol expands up a thin column in the thermometer. The length of the alcohol column indicates the temperature. Extra care must be taken with thermometers containing mercury as it is poisonous. thermosphere: a layer of the atmosphere that extends to about 400 km above the Earth, between the mesosphere and exosphere thorax: the section of an insect’s body between its head and its abdomen tidal month: the time it takes from one full moon to the next. A tidal month is not the same as a calendar month (e.g. August).

tidal range: the difference between the higher of the high tides in a given day and the lower of the low tides tinea: a painful skin disease, caused by a fungus, that often occurs between the toes tissue: a group of cells that come together to perform a specific function. For example, muscle tissue is formed by muscle cells, and nerve tissue is formed by nerve cells. tolerance range: range of an abiotic factor in the environment in which an organism can survive tooth decay: the formation of holes in the surface of teeth toxic: describes chemicals that are dangerous to touch, inhale or swallow trace elements: elements needed in minute amounts in compounds in the soil for healthy plant growth trace fossils: fossils that provide evidence, such as footprints, that an organism was present when the rock was formed trachea: narrow tube from the mouth to the lungs through which air moves tracheophytes: plants that contain vascular tissue traction: a force that keeps objects from slipping or losing contact with a surface. Traction is similar to friction. transferred: moved from one place to another transformed: energy changed from one form to another transfusion: injection of blood from another person into your veins to replace the blood you have lost translocation: transport of materials, such as water and glucose, in plants transmit: pass through something, such as light or sound passing through air transmitted: passed through something, such as light or sound passing through air transparency: allowing most of the light to pass through a substance transpiration: loss of water from plant leaves through their stomata transpiration stream: movement of water through a plant as a result of loss of water from the leaves trial: repetition of an experiment. Increasing the number of trials increases the reliability of the experiment. tricuspid: a type of valve with three cusps (points). The valve between the heart’s right atrium and right ventricle is a tricuspid valve. trophic: describes the different levels in a food chain, food web or food pyramid troposphere: the layer of the atmosphere closest to the Earth’s surface. The particles of the air are packed most closely in this layer and they spread out further away from the surface. ultraviolet (UV) rays (radiation): invisible radiation very similar to violet light, but not visible, more energetic and able to damage skin cells

Glossary 557

umbilical cord: a cord that connects a developing embryo/ foetus to the mother’s placenta umbra: the darker, central part of a shadow unbalanced: describes two or more forces that do not cancel each other out. Unbalanced forces can start an object moving, speed it up, slow it down, change its direction or change its shape. unicellular: describes an organism having only one cell universe: all of space and the matter and energy contained in it Uranus: a small planet with an unusual rotation. It spins rapidly with its axis of rotation pointed towards the sun. ureter: tube from each kidney that carries urine to the bladder urethra: tube through which urine is emptied from the bladder to the outside of the body urination: passing of urine from the bladder to the outside of the body urine: yellowish liquid, produced in the kidneys. It is mostly water and contains waste products from the blood such as urea, ammonia and uric acid. vacuole: a sac within a cell used to store food and wastes. Plant cells usually have one large vacuole. Animal cells may have several small vacuoles or none at all. valves: flap-like folds in the lining of a blood vessel or other hollow organ that allow a liquid, such as blood, to flow in one direction only variable: quantity or condition in an experiment that can change varicose veins: expanded or knotted blood vessels close to the skin, usually in the legs. They are caused by weak valves that do not prevent blood from flowing backwards. vascular bundles: groups of xylem and phloem vessels within plant stems veins: blood vessels that carry blood back to the heart. They have valves and thinner walls than arteries. vena cava: large vein leading into the top right chamber of the heart Venus: the planet closest to Earth. Venus is very hot due to an atmosphere of mainly carbon dioxide. verdigris: the whitish green coating that develops on bronze when it has been exposed to air and moisture vertebrate: an animal with a backbone vibrations: repeated fast, back-and-forth movements vital capacity: the largest volume of air that can be breathed in or out at one time vitamins: organic nutrients required in small amounts. They include vitamins A, B, C, D and K. voltage: the amount of energy contained in electrons flowing in an electric circuit voltmeter: a device used to measure the amount of energy used by a component in a circuit. Voltmeters are placed in parallel with the components that they are measuring.

558

Glossary

volume: the amount of space taken up by an object or substance voluntary muscle: muscle attached to bones; it moves the bones by contracting and is controlled by an animal’s thoughts water: a colourless liquid made up of particles containing two hydrogen atoms bonded to one oxygen atom, and written as H2O water condenser: a glass device for cooling a gas to form a liquid. It is a tube within a tube. The gas flows through the inner tube while water moves through the surrounding outer tube to cool the gas. water soluble: describes substances that dissolve in water water still: a device used to distil water watertable: the top portion of the ground saturated by water water vapour: water in the state of a gas when the temperature is less than 100 °C. Water vapour remains in the air as a result of the evaporation of water from the Earth’s surface. waveform: a graph that shows the energy of sound versus time weathering: the process of breaking down rocks by conditions in the atmosphere weight: a measure of the size of the gravity force pulling an object towards the centre of a massive body, such as the Earth. The weight of an object depends on the object’s mass. white blood cells: living cells that fight bacteria and viruses. They are part of the human body’s immune system. white dwarf: the core remaining after a red giant has shed layers of gases. A white dwarf has no nuclear reactions and its only energy source is gravity that pulls it into a core of very dense matter, a jumble of tightly packed electrons, protons and neutrons. wind: the flow of air particles as they move from an area of higher air pressure to an area of lower air pressure wind-pollinated flower: flower that receives pollen carried by the wind from another flower x-axis: the horizontal axis on a graph xylem: tissue that carries water and minerals from the roots of plants to all other parts of the plant xylem cells: long narrow cells that are joined together to form long tubes in a plant. The tubes, made from xylem cells, move water and dissolved minerals up from the roots to the stem and leaves. The wood in a tree trunk consists mostly of dead xylem cells. y-axis: the vertical axis on a graph yeast: a fungus that causes certain foods (e.g. dough) to rise zodiac: the region that the sun, moon and planets seem, from Earth, to occupy as they pass in front of 12 constellations that make up what we call ‘star signs’

Index A abdomen 106 abiotic factors 390, 392, 394 abrasive cleaning products 490 Aboriginal culture astronomy 217–18 bush tucker 360 classification of living things 110 fire 409 living Earth 390 Rainbow Serpent 390 Abrahams, Edward 455 abundance of species 390, 392 acetic acid 325 acid–base indicators 325, 326 acid rain 328–9, 503 acids 325–9 adaptations for dry conditions 412 adipose tissue cells 131 adult stem cells 137 affinity diagrams 516 agar 449 ageing-related diseases 447, 448 AIDS 447, 453 air 180, 183, 267 air classifier 62 air pressure 183–5, 249 air resistance 150, 151, 152 alchemists 293 alcohol 51, 235, 236, 383, 451 Aldrin, Buzz 210 Alexander, Albert 456 algae 109, 128, 180, 353, 354 alkaline batteries 437 alkaline water 78 alkalis 325 allotropes 303 alloys 157, 300 Alpha Centauri 468, 476 altitude and air pressure 183 altocumulus 178 alum 78 aluminium 41, 62, 294, 490 alveoli 267, 268 amber, fossils in 501 amino acids 364, 375 ammeter 432, 434 ammonia 325, 403, 404 Amoeba 93, 109, 127 ampere 430 Ampère, André 431 amphibians 96, 97, 98, 278 amylase 375, 376 anaemia 372 ancient Greek astronomy 218 Andromeda Galaxy 468, 469, 470 angiosperms 353 Animalia 92, 93, 127, 128, 129 animals cells 122

classification 95–107 extinct 501 annelids 105 antacid 327 antennae 104, 106 anther 346 antibiotics 29, 453, 455–6 antibodies 276 antimony 293, 295 anus 371 aorta 280, 382 aortic valve 278 appendix 370 aqueous solutions 64 arachnids 107 Architeuthis dux 105 Aristarchus 219 Aristotle 174, 218, 219, 221, 480 Armstrong, Neil 209, 210, 479 arsenic 273, 293, 295 arteries 275 arthropods 96, 104, 106, 107 Aspro 462 assimilation 86 astatine 295 asteroid belt 222 asteroids 222 asthma 271–2 astrology 475 astronomy 4, 217–21, 475 ancient Greek 218 astrology compared 475 geocentric model 218, 219, 221 heliocentric model 219, 220 history of 217–21, 480 Incan 218 indigenous Australian 217–18 Renaissance 219–20 atmosphere 175, 180 atoms 54, 120, 263, 264, 290–1, 306–7, 423 bonding 297, 301 development of atomic model 306–7 electrical charge 423 neutral 291 ‘plum pudding model’ 306 structure 291 atrioventricular valve 278 auditory nerve 250, 251 aurora australis 181 aurorae 181 Australian bush 409, 410 Australian mammals 100–1 axis Earth rotating on 205 line graphs 530 sun rotating on 203 axle 151 aye-aye 250

B backdraught 323 bacteria 29, 30, 76, 85, 86, 93, 108–9, 120, 128, 406, 449–52 agar, growing in 449 antibiotics killing 29, 453 bad 449 binary fission 449 body odour, causing 457 colonies 449 cycling of nutrients 403, 452 decomposer 400, 402, 403, 452 diseases caused by 445, 447, 448, 449 good 449 nitrifying 403, 404 nitrogen-fixing 403 penicillin used against 108, 455–6 reproduction 449 single-celled organism 93, 108, 449 size 120, 449 baking powder 314 balanced forces 147, 148 ball and socket joints 380 ball bearings 151 bar graphs 21, 529 barometer 184 barred spiral galaxies 470 basal cell carcinoma 459 basalt 490, 500 bases 325–6 batholiths 489 bathroom science 37, 47 bats 254 batteries 431, 432, 434, 437 car batteries 325, 437 dry cells 437 9 V and 12 V 437 types 437 Bay of Fundy 212 beaker 3, 7, 8, 9, 10, 20, 67, 525 beam balance 17 Behrendt, Dr Ralph 189 Betelgeuse 473 bicarbonate of soda 314, 325 biceps 378 bicuspid valve 278 bicycle helmet 167 Big Bang theory 480 bile 370, 376 billy tea 69 binary fission 127, 449 binocular microscope 116 biodegradable substances 403 biologists 4, 5 biomechanics 6, 14 bionic ear 253 biosonar 254 biotic factors 390 birds 96, 97, 98, 110

Index 559

black hole 468, 480 bladder 382 blood 70, 275–6, 382 artificial 283 capillaries, moving through 275, 279 circulatory system 263, 265, 275–81 concentration of substances in 383 deoxygenated 277 donations 70 mixture 70, 275 oxygenated 277 plasma 70, 71, 275, 368 platelets 70, 71, 137, 276 red blood cells 70, 130, 131, 137, 275, 276 separating 70, 71 serum 276 transfusion 283 type 259 water in 368, 382 white blood cells 70, 130, 137, 276 blood pressure 278, 282 blood type 259 blood vessels 274, 371 blue-green algae 109, 128, 353 blue whale 95, 249 Bohr, Neils 307 boiling 40, 46 boiling flask 72 boiling point 40, 41, 42 bolus 370 bone cells 130, 379 bone marrow 130, 137, 379, 380 bones 378–81 boron 295, 422 bosshead 7, 8 botanists 4 Boyle, Robert 261 bran 368 brass 297, 300 breathing 267–70 broken bones 380 bromothymol blue 326 bronchi 267 bronchioles 267, 268 Brown, Robert 120 bryophytes 353 bubble maps 514 bungee forces 162 Bunsen burner 7, 8, 10, 20 buoyancy 27, 146, 165 burette 525 burning 304, 323–4 backdraught 323 candles 313–14 fossil fuels 323, 405 oxidation 323, 324 rocket fuels 324 bush tucker 360 bushfires 409–11 Butler, Jerry 403

560

Index

C cakes rising 314 calcium 78, 336, 366, 379 calcium carbonate 495 calculus 31 Calories 361 calorimeter 261 cancer 447, 448, 459 brain 459 cervical 462 skin 414, 459–62 candles burning 313–14 canines 373 capillaries 267, 268, 275, 279, 280, 371 capture–recapture method 392 car(s) 440–1 batteries 325, 437 electric 440 engine 323 hybrid 441 safety 168 carbohydrates 364, 367, 396 carbon 293, 303–5, 405 amorphous 303 chemical symbol 294 diamond 297, 303, 487 finding 303 flow of 305 fuels 304 graphite 303 non-metal 295 recycling 405 steel made from 300 carbon dioxide 301 acid rain 328 air containing 180, 267 diffusing out of cells 125, 263 dry ice 298 excreting 86, 260 fermentation 451 fire hydrants 52 fizzy drinks 53, 64, 298 greenhouse effect 405 Mars 198 molecules 301, 302 photosynthesis 85, 86, 335, 340, 341, 343–5, 399, 405 respiration 85, 86, 260, 267, 304, 382, 399 traps 182 Venus 197, 204 carbon monoxide 273, 319 carbonated drinks 53, 64, 298 carbonic acid 325, 328 carcinogens 273 cardiac muscle 279 Carina Nebula 471 carnivores 374, 399, 400 carnivorous plants 353

carpel 346 Cartesian diver 166 cartilage 97, 379, 380 catalyst 319 cathode ray oscilloscope (CRO) 249 caustic soda 325 cell (electrical) 432, 437 cell membrane 122, 128, 260 cell sap 122 cell walls 122, 128, 129, 340 cells 114, 119–42, 264 adipose tissue cells 131 animal cells 122 blood cells 70, 130, 131, 275, 276 bone cells 130, 379 classification according to 92 death of 123 diffusion into/out of 125, 263 discovery of 119 egg cells 131 epidermal cells 133, 136, 340 guard cells 133, 340 histologists studying 463 leaf cells 133 lung epithelial cells 131 multicellular organisms 128, 129, 263, 335 muscle cells 130 nerve cells 131 organelles 122, 123, 124 phloem cells 133, 136, 260, 338, 353 plant cells 122, 128, 133, 335 root hair cells 133 size 120, 123 skin cells 123, 131 sperm cells 131 stem cells 137–9 unicellular organisms 127, 129, 263 xylem cells 133, 136, 338, 353 cellulose 122, 364 central nervous system 264, 265 centre of gravity 147 centrifuging 68 blood 70, 71 cerci 106 Ceres 222 cervical cancer vaccine 462 Chain, Ernst 455 chalk 496 Chang, Victor 284 changing state of matter 40, 46, 313–16 chemical changes 313, 316 chemical energy 230 chemical engineers 6 chemical reactions 233, 311–30, 399 batteries 437 burning 323–4 catalyst 319 changing rate of 320

chemical reactions (continued) concentration of solution 319 describing 316 energy from 233 products 316 rate of 318–20 reactants 316 rusting 321–2 surface area, changing 319 temperature, effect of 318 word equations 316 chemical symbols 294 chemicals in cigarettes 273 chemicals in water 78 chemists 5 chilopods 107 chlorine 78 chlorofluorocarbons 182 chlorophyll 93, 122, 336, 341, 399, 416 chloroplasts 122, 123, 129, 133, 341, 344 chromatography 73, 74 cigarette smoking 273 cilia 131 circuit diagrams 432, 435 circulatory system 136, 263, 265, 275–81 cirrocumulus 178 cirrus 178 citric acid 325 clamp 7, 8 classes 93 classification 83–113 Aboriginal names 110 animals 95–107 circular keys 91 classes 93 dichotomous keys 89–90 families 93 genera 93 groups 92 hierarchy 93 invertebrates 95, 96, 104–7 kingdoms 92, 93, 108, 127 living/non-living 85–8 orders 93 phyla 93 plants 353–5 species 93, 104 vertebrates 95, 96, 97–9, 110 clouds 177–8 cluster maps 514 cnidarians 96, 104 coal 495, 496 Coal Sack 470, 476 coastal erosion 503 cobalt 156, 157 cochlear implant 253 cockroach 105 coeliac disease 372 cohesion 166 collaboration 396

colloid 66, 78 colourfast 334 Columbia space shuttle 152 column graphs 21, 529 combustion 323 comets 222–3 commensalism 396–7 common cold 453 compact bone 379 compass 156, 157 complex carbohydrates 367 compounds 298, 301, 302 compression 43, 52, 247 concentration of solution 319 concept maps 516 condensation 40, 313 conducting path 429 conducting tissue 338 conduction 236–7, 241, 242 conductors 430, 431 conglomerate 495, 500 conical flask 7, 8, 20, 67, 72 connecting wire 432 connective tissue 135 constellations 469, 470, 474–5 constipation 368 consumers 399 contact forces 145, 146 contraction 50–1 controlled tests 25, 350, 524 controlling variables 164 convection 238–9, 241, 242 convention currents 238, 239 Copernicus, Nicolaus 30, 175, 219–20, 480 copper 293, 294, 300, 431 copper carbonate 316, 317 copper sulfate and iron 317 cord blood stem cells 137 corrosion 321 corrosive substances 9, 321, 325 Cosmic Background Explorer (COBE) 481 cotyledons 348, 349 cross-pollination 346 crustaceans 107 crystallisation 73 cumulonimbus 178 cumulus 178 Curie, Marie 31 current convection 238, 239 deep water 178 electric 430 ocean 178 cusps 373 cyanobacteria 93, 109, 128 cycle maps 519 cycling nutrients 403 cycling safety 167 cyclones 185–7 cytoplasm 122, 127, 260

D D’Alessandro, Deanna 416 Dalton, John 306, 307 dangerous chemicals 9 cigarettes 273 contaminated water 78 data loggers 15 databases 535–6 designing 536 electronic 535 fields 536 searches 535 decanting 67 decibel scale 249 decomposers 304, 400, 402, 403, 452 decomposition 304, 336 deep water currents 178 deforestation 405, 503 dehydration 368, 383 Democritus 290, 306, 307 denitrifying bacteria 403 density 48–9 density of species 390 dentine 373 deoxygenated blood 277 dependent variable 25, 350 deposition 493 dermis 457 designing experiments 25–8, 524–7 diabetes mellitus 260 diagnosis 463 diamond 297, 303, 487 diaphragm 135, 268 diastolic pressure 278 diatomaceous earth 108 diatoms 108, 109 dichotomous keys 89 dietitians 369 diffusion 38, 44, 125, 263 digestion 370–6 chemical 375 mechanical 373 digestive system 130, 135, 136, 260, 263, 265, 280, 368, 370–2 Dimetrodon 97 diplopods 107 Diprotodon 101 diseases 445–65 infectious 447, 448 microbes causing 449–52 non-infectious 447, 448 pathogens 447 viruses causing 453–4 dispersal of seeds 348 dissolving 64 distillate 72 distillation 72 distilled water 72 distribution of species 390, 392

Index 561

divided bar graphs 529 DNA 122, 128, 459 domains 156 double bubble maps 514 drag (friction) 147, 151 drought 412 dry cell batteries 437 dryland salinity 188–9 dugong 416 dust mites 271, 272 dusting 428 Dutrochet, René 120 dwarf planets 193, 195 E ear 250–1 bionic 253 ear canal 250 eardrum 250 Earth 172–90, 195–8, 205–8 age 172 atmosphere 180, 204 crust 175 diameter 172, 174, 205 inner core 175 magnetic field 156 mantle 175 mass 172 orbit around sun 207 outer core 175 rotation 205–6 shape 174–5, 205 stars viewed from 474 structure 175 surface 175 surface area 174 temperature 176, 407 water 177–9 earth scientists 4 earthworms 95, 105 echinoderms 96, 104 echoes 248 echolocation 254 ecology 387–420 ecosystem 390, 391 ectotherms 97, 98 eddy current 62 Edison, Thomas 431 egg cells 131 Einstein, Albert 4, 30, 480 elastic potential energy 229 electric cars 440 electric cells 432, 437 electric circuits 429–39 brightness 436 circuit diagrams 432, 435 completing 429 conducting path 429

562

Index

essential features 429 load 429 parallel circuits 435, 436 power supply 429 series circuits 434 torch 432, 433 electric current 430 electric field 426 electric force, mapping 426 electrical charge 423, 426 attraction/repulsion of charged objects 426, 428 electrical energy 232, 429 electricity 421–44 batteries 431, 432, 434, 437 circuits 429–39 coal used to produce 496 conductors 430, 431 insulators 430, 431 static 423–8 transporting 430 electrocardiogram (ECG) 283 electrolyte 437 electromagnetic spectrum 204 electromagnets 157, 158, 159 electron microscope 108, 114, 115, 116, 121 electronic databases 535 electronic scales 17 electrons 54, 291, 306, 307, 423, 424, 426, 429, 431 electrostatic charge 424 electrostatic forces 146 elements 293, 487 compounds made from 298 dangerous 293 distinguishing 293 grouping 295–6 metalloids 295 metals 295 mixtures of 298 native elements 487 non-metals 295 symbols 294 elephant 252 elliptical galaxies 469 embryonic stem cells 137, 138 embryos 97 plants 348, 368 emphysema 273 emulsify 376 emulsion 66 enamel (teeth) 373 endangered species 414 endoskeletons 95 endosperm 348, 368 endothermic reactions 233 endotherms 97, 98 energy 30, 229–57 calculating 231

chemical reactions and 233 elastic potential 229 electrical 232, 429 food and 361–3 gravitational 229, 231 heat 232, 234, 235–43 joule as unit of 231 kinetic 229, 231, 232 Law of Conservation of Energy 232 light 232, 234, 244–6 measuring 231 potential 229, 231 pyramid 401 saving 231 solar 204, 240, 243 sound 246–52, 429 transferring 232 transforming 232 types 229–30 Engelmann, Theodor Wilhelm 344 enhanced greenhouse effect 405 entomologists 403 environment 390 acid rain 328–9, 503 dryland salinity 188–9 ecology 387–420 erosion 493, 503–4 global warming 405–7, 413, 414 greenhouse effect 181–2, 204, 405–7 measuring 392–4 waste water 76 environmental diseases 447, 448 environmental-impact assessment 388 enzymes 319, 364, 375, 377 Eocene epoch 102 eosin 125 epicormic buds 410 epidermal cells 133, 136, 340 epidermis 335, 457 epiglottis 267, 268, 370 epiphytes 397 epithelial cells 131, 135 equations for chemical reactions 316 Eratosthenes 175, 218 erosion 493, 503–4 eucalypts 410, 413 Euglena 93, 109, 127 Eustachian tube 251 evaporating dish 7, 8, 10 evaporation 40, 72, 73, 313, 314, 457 Evergraze 189 Excel spreadsheets 533 excretion 86, 260, 263, 280, 382 excretory system 265, 382–4 exoskeletons 95, 104, 378 exosphere 180, 181, 183 exothermic reactions 233 expansion and contraction 50–1

experiments accuracy 525 aim 350, 510 control 26, 350, 524 designing 25–8, 350, 524–7 fair tests 25 hypothesis 19, 25, 351, 510–12 reliability 26, 525 report 20–4, 352, 538–9 results 528–32 safety 526 sample size 526 student research project (SRP) 508–41 trials 526 valid 524 extinct animals 501 extinction 414 extrapolation 161, 531 extrusive rocks 489 eye (of cyclone) 185 F faeces 368, 452 fair tests 25 famous scientists 29–31 fat-soluble vitamins 366 fats 366, 367, 375, 376 fatty tissue 457 fault (in rock) 500 feldspar 490 fermentation 451 fertilisation 131, 347 fever 454 fibre 364, 367, 368 fibrinogen 276 filament (plant) 346 filament (torch) 432, 433 filter 76 filter funnel 7, 8, 9, 20, 67 filter paper 67, 68 filtrate 67, 68 filtration 67 blood 70 fingernails 131 fire 409–11 fire intensity 410 fireworks 227 fish 96, 97, 98, 278, 383, 398 fish oil 364 fishbone diagrams 516 Fisher, Paula 463 five kingdoms 92, 93, 108, 127 flammable substances 9 Flannery, Tim 416 flatworms 105 Fleming, Alexander 5, 18, 29, 455 flies 402 floatables 76 floating 48

floc 78 flocculation 78 floods 413 Florey, Ethel 456 Florey, Howard 455, 462 flow charts 519, 520 flowers 335, 346, 347, 348 fluids 151 friction in 151 fluoride 78 fog 177 foggy mirror in bathroom 37, 47 folding 500 food bacteria in 445, 451 bush tucker 360 energy and 361–3 essential intake 364 fuel, as 361–3 healthy eating 367–8 low/high GI 376 microbes in 445, 451 food chains 398–400 food pyramid 367 food webs 398–400 forces 6, 143–70 balanced/unbalanced 147, 148 contact/non-contact 145, 146 electrostatic 146 friction 6, 146, 149–53 gravitational 146, 158–64 magnetic 146, 154–9 measuring 146 newton as unit of 31, 146, 160 representing 147 types 145 what are 145 fossil fuels 304, 323, 405 fossils 500–2 fracture greenstick 380 mineral 487 Franklin, Benjamin 29, 423 freezing 40, 313 frequency 249 friction 6, 146, 149–53 electrostatic charge 424 fluids 151 measuring 150 reducing 151 space shuttle 152 traction and 150 using 149 what affects 149 what is 149 frothy rocks 490 fruit 348 fuel 304 burning fossil fuels 323, 405 burning rocket fuels 324

coal 496 food as 361 fungi 93, 108, 128–9, 397, 400, 402, 448–52 cell design 129 cycling of nutrients 452 decay of food 451 disease caused by 445, 448 Fungi kingdom 92, 93, 108, 128 G Gagan, Michael 102, 103 Gaia 390 galaxies 469–70 Galilei, Galileo 30, 209, 210, 221, 478, 480 Galileo space probe 481 gall bladder 370, 371, 376 Galvani, Luigi 427 galvanising 322 Gantt charts 518 Gardner, AD 455 garlic breath 265 gas giants 195, 198–9 gases 38, 53 carbonated drinks 53 changing state 40, 46 compression 43, 52 conduction in 236, 237 expansion 50 particles in 43, 44, 46 well-known gases 53 gauze mat 7, 8, 10 gelatine 449 Gell-Mann, Murray 291 genera/genus 93 Genyornis 101, 103 geologists 4, 5, 487 germanium 295 germination 348, 349, 351, 409, 411 germs 449 Gesch, Bernard 364 giant kangaroo 101 giant mammals 101 giant squid 105 glass sorting facility 62 global positioning system (GPS) 475 global warming 405–7, 413, 414 globe 432, 433 brightness 436 glow sticks 246 glucose 85, 260, 342, 364, 365, 375, 396 blood glucose level 376 diabetes mellitus 260 fermentation 451 photosynthesis 340, 341, 342, 343, 399 respiration 85, 260, 399 gluten 372 glycaemic index (GI) 376 glycogen 370

Index 563

gneiss 497 gold 293, 294, 295, 300, 302, 487 granite 490 graphite 303 graphs 21, 528–33 gravitational attraction 212 gravitational energy 229, 231 gravity 31, 146, 158–64, 180, 183, 203, 212 bungee jumping 162 centre of 147 galaxies held together by 469 Newton’s law of 31, 162, 480 skydiving 163 tides and 212 greenhouse effect 181–2, 204, 405–7 greenhouse gases 406 greenstick fracture 380 ground water 188 growing (living things) 86 groynes 503 guard cells 133, 340 gum 373 gymnosperms 353 gypsum 329 gyres 179 H habitat 390 haemodialysis 383 haemoglobin 275, 283 hair 131 Hales, Stephen 344 Halley’s comet 223 hardness (minerals) 487–8 Hawking, Stephen 480 head lice 447, 448 health sciences 462–3 healthy eating 367–8 hearing 250 hearing loss 249 heart 277–84 artificial 282 chambers 277 disease 282, 283 faulty valves 282 functions 277 left/right atrium 277, 280 left/right ventricle 277, 280 rate 279 transplant 284 valves 277 heartbeat 278 heat 235 conduction, transfer by 236–7, 241, 242 convection, transfer by 238–9, 241, 242 energy 232, 234, 235–43 insulation 241–2 radiant 240 radiation, transfer by 241–2 temperature distinguished 235

564

Index

heating containers 10 heating substances 10 Heatley, Norman 455 heatproof mat 7, 8, 10 helium 53, 165, 203, 294 Helmont, Jan Baptista van 344 Hemopure 283 herbivores 374, 399, 400 heresy 30 hertz 249 Hesse, Walther 449 high GI foods 376 high pressure system 185 hinge joints 380 Hipparchus 219 histograms 529 histologists 463 Hofmann voltameter 298 Holocene epoch 102 Hooke, Robert 119, 120 Hopper, KE 102 horticulturalists 4 host 396 hot-water tank 239 Hubble Space Telescope 469, 473, 479, 481 human body temperature 51, 97 humerus 380 humus 493 hybrid cars 441 hydrochloric acid 316, 317, 325, 327, 370 hydrogen 203, 294, 297, 298 hydroponics 336 hydrosphere 175 hygiene theory of asthma 272 hypertension 282 hypothesis 19, 25, 351, 510–12 choosing 510–12 fine-tuning 511 prediction distinguished 511

influenza virus 453, 456 infra-red radiation 204 infra-red scanners 241 Ingenhousz, Jan 344 inherited disorders 447, 448 inner ear 250 inorganic nutrients 366 insectivores 374 insect-pollinated flowers 346 insects 106, 107, 252, 378, 346, 347, 403, 403 insoluble substances 64, 65 insulating your body 242 insulation 241–2 insulators 236, 430, 431 insulin 260 intensification 185 International Space Station (ISS) 482 interpolation 531 intestine 370 intrusive rocks 489 invertebrates 95, 96, 104–7 investigations 3, 293, 350–2 student research project (SRP) 508–41 in-vitro fertilisation (IVF) 137–8 involuntary muscles 378 iodine 125 ionosphere 180, 181 iron 293, 300, 366, 490 anaemia 372 boiling point 41 copper sulfate and 317 magnets affecting 155, 156, 157 melting point 41 rusting 321–2 steel made from 300 iron oxide 487 irregular galaxies 469 irrigation 412 J

I ice ages 407 ice core 406 Iceman 501 identification keys 89 circular 91 dichotomous 89–90 igneous rock 489–91, 497 image 253 immovable joints 380 immune system 453 Incan astronomy 218 incisors 373 incubation 449 independent variable 25, 350 indigestion 327 industrial chemists 6 infectious diseases 447, 448 inference 18

Jennings, Margaret 455 joints 151, 379–80 joule 231 Jupiter 195, 196, 198, 207, 219, 478, 480 moons of 221, 222, 478 K kangaroo 412 Kepler, Johannes 220 Kepler’s laws of planetary motion kidney disease 384 kidneys 280, 382, 383 kilojoules 361 kilopascals 183 kinetic energy 229, 231, 232 kingdoms 92, 93, 108, 127 Koch, Robert 449 Krakatoa 246 Kyoto Protocol 407

220

L laboratory equipment 7, 8 drawing 20 safety 9–12 land breeze 184 landfill 62, 406, 414 Laplace, Pierre Simon 480 large intestine 371, 383 larvae 402, 403 latitude 475 lava 489, 490 Lavoisier, Antoine 261 Law of Conservation of Energy 232 leaf cells 133 leaf litter 409 Lee, Arianne 463 Leeuwenhoek, Antonie van 119, 120 Lefevre, Christophe 102 Lemaitre, George 480 length 14–15 library, using 521–2 lichen 85, 109, 326 ligaments 379, 380 liger 93 light energy 232, 234, 244–6 luminous/non-luminous objects 244, 245 speed of 244, 248 vacuum, travelling through 247 light globes 234 light microscope 116, 122, 342 lightning 29, 54, 248, 336, 404, 423, 426, 427 lightning rod 29, 427 light-year 468 lignin 338 lignotubers 410 lime 78, 496 limestone 495, 496, 497, 500 line graphs 21, 530 line transects 392 Linnaeus, Carl 92 lipase 375, 376 lipids 366, 375, 376 liquids 38 changing state 40, 46 conduction in 236, 237 expansion and contraction 50 particles in 43, 44, 46 lithosphere 175 litmus 326 liver 280, 370, 382, 383 living things 85–8 load 429 logbook 521 longitude 475 Lovelock, James 390 low GI foods 376

low pressure system 185 lubricants 151 luminous objects 244, 245 lunar eclipses 214 lung cancer 273, 274 lung capacity 269 lung epithelial cells 131, 135 lungs 267, 269, 280, 382 smoking and 273–4 lustre 487 M mad cow disease 447, 448 Magee, John 102, 103 Magellanic Cloud 468, 469 maggots 402 maglev train 159 magma 489 magnesium 366, 490 burning 323 hydrochloric acid and 316, 317, 327 plants needing 336 tap water 78 magnetic field 155 Earth 156 mapping 155 magnetic forces 146, 154–9 magnetic North Pole 156 magnetic South Pole 156 magnets 60, 62, 146, 154–9 attracting 146, 154, 155 electromagnets 157, 158, 159 permanent 154, 157, 158 poles 146, 154, 155, 156 repelling 146, 155 temporary 154, 157 using 158 magnification 119 mammals 96, 97, 98, 100 Australian 100–1 giant 101 mantle (of Earth) 175 manufacturing processes 62 mapping electric force 426 magnetic field 155 thoughts 514–17 marble 497, 498 Mars 195, 196, 197, 198, 219 moons 222 Marsh, Helene 416 Marshall, Barry 462 marsupials 100 mass 160, 212 estimating 17 gravity and 160, 212 measuring 17 units of measurement 17, 160 weight distinguished 160

matter 36, 288 bonds 46 changing states 40, 46, 313 density 48–9 expansion and contraction 50–1 plasma 54–5 ranking substances 37 solids, liquids and gases 37–53 volume 39 McKenzie, HA 102 measuring 13–18 data loggers 15 energy 231 environment 392 forces 146 friction 150 length 14–15 mass 17 parallax error 15 reading scales 16 sensor 15 sound 249 temperature 15–16, 51 time 18 volume 15, 39 measuring cylinder 3, 7, 8, 9, 525 medical scientists 462, 463 megafauna 101, 103 Megalania 101 melanoma 459 melting 40, 46, 313 melting point 40, 41 meniscus 15, 39 mental disorders 447, 448 mercury 51, 293, 294, 295 Mercury 195, 196, 197, 198, 219 mercury poisoning 294 mesosphere 180 metabolic disorders 447, 448 metalloids 295 metamorphic rocks 497–9 metals 295, 300, 430, 431 metamorphism 497 meteorites 223 meteoroids 223 meteors 223 methane 53, 180, 199, 302, 405, 406 methyl orange 325 methylene blue 125 mica 490 microbes 445, 449–52 microbiologists 4, 119 micrographs 118 micrometres/microns 120, 449 micro-organisms 445, 449–52 microscopes 105, 114–19 binocular 116 electron 108, 114, 115, 116, 121 invention 119

Index 565

microscopes (continued) light 116, 122, 342 monocular 116, 117 rules for handling 116 sketching specimen under 125 staining specimen 125 types 116 using 116 middle ear 250 Milky Way Galaxy 466, 469, 470, 478 mind maps 514, 515 mineral salts 335 minerals 336, 366, 487–8 hardness 487–8 lustre 487 plants needing 336 rocks made of 487 streak 487 transparency 487 Miocene epoch 102 mistletoe 396 mitochondria 85, 122, 123, 128, 260 mixtures chemical 297 colloid 66 emulsion 66 metals 300 separating 59–63, 67–75 solution 64–5 Mohs’ hardness scale 487, 488 molars 373 molecules 263, 264, 301 molluscs 96, 104 Monera 92, 93, 108–9, 127, 128, 129, 353 monochloramine 78 monocular microscope 116, 117 monotremes 100 moon 209–11 landings 209, 210 lunar eclipses 214 phases 210 tides affected by 212 moons 222 mould 402 movement (living things) 85 mudstone 495, 500 multicellular organisms 128, 129, 263, 335 muscle cells 130 muscle tissue 135, 263 muscles 378 mutualism 396 N native elements 487 natural fibres 241 navigation by the stars neap tides 213 nebulae 468, 470 nectary 346

566

Index

475

negative electric charge 423 negatively charged material 423, 426 nematodes 105 neon 53 Neptune 195, 196, 198, 199, 480 nerve cells 131, 244 nerve tissue 135 nervous system 136 neuropsychologists 5 neutral atom 423 neutral material 423, 424, 426 neutrons 291, 307, 423 newton 31, 146, 160 Newton, Isaac 31, 146, 162, 480 Nicholas, George 462 Nicholas, Kevin 102 Nicholas of Cusa 344 nickel 156, 157 nicotine 273 nimbostratus 178 nitrates 403, 404 nitric acid 325, 328 nitrifying bacteria 403, 404 nitrites 403, 404 nitrogen 180, 302, 336, 403, 404 air containing 180, 302 boiling point 41 chemical symbol 294 compounds 336 cycle 404 fixing 336, 403 melting point 41 plants needing 336 nitrogen fixing 336 nitrogen-fixing bacteria 403, 404 nitrous oxide 53, 405, 406 Nobel prize 30, 455, 462 non-biodegradable substances 403 non-contact forces 145, 146 non-infectious diseases 447, 448 non-living things 85, 87 dead things distinguished 87 living things distinguished 85–8 non-luminous objects 244, 245 non-metals 295 Norman, Dr Hayley 189 North Celestial Pole 474 North Pole 156, 175, 205 Northern Hemisphere 175, 207 notochord 97 nucleic acid 453 nucleus atom, of 291, 423 cell, of 108, 109, 122, 123, 125, 127, 128, 129, 260 nutrients 336, 364, 365, 389 nutrition-related diseases 447, 448 Nyström, Fredrick 362

O observations 14, 18, 293, 511 measuring 13–18 qualitative 14 quantitative 14 observatories 478 obsidian 490 ocean currents 178, 179 gravitational attraction of moon and sun 212 gyres 179 tides 212–13 oesophagus 267, 370, 371 oils 366, 375, 376 Oligocene epoch 102 omega-3 fatty acids 364 omnivores 374, 399 onion cells 124 optical telescopes 469, 478 optimum range 392 orbit 195, 469 organelles 122, 123, 124, 264 organisms 92, 390, 500 organs 135, 136, 263, 264, 265 Orion 470, 473, 474 Orr-Ewing, Jena 455 osmosis 125 ossicles 250 ossification 379 osteoporosis 380–1 outer ear 250 oval window 250 ovary (plant) 346, 348 ovules (plant) 346, 348 oxidation 323, 324 oxyacetylene torch 323 oxygen 180, 261, 267, 298, 302 air containing 180, 267 boiling point 41 breathing 267 chemical reactions involving 323 chemical symbol 294 diffusing into cells 125, 263 Earth’s crust 487 gas 301 germination, required for 349 living things needing 261 melting point 41 non-metal 295 phenolics reacting with 319 photosynthesis 85, 86, 93, 127, 335, 340, 341, 343–5, 399 red blood cells carrying 130 respiration 85, 86, 260, 261, 267, 335, 399 splitting from water 298 water composed of hydrogen and 297, 298

oxygenated blood 277 oxyhaemoglobin 275 ozone 53, 180 ozone layer 180, 182 P pacemaker 278, 463 palaeontologists 4, 500 Palaeocene epoch 102 palisade cells 133 pancreas 371, 375 paper chromatography 73, 74 paper mills 62 parallax error 15 parallel circuits 435, 436 paralysis 138 Paramecium 127 parasites 108, 396 parasitism 396 partial lunar eclipse 214 partial solar eclipse 215 particle model 43, 44, 50 Pasteur, Louis 30 pathogens 448 pathologists 462 pelycosaurs 97 penicillin 108, 455–6 penumbra 214, 215 Peplin 459 peristalsis 370, 371 petals 346 Petri dish 449 petrol 440 pH scale 326, 329 pharmacists 5 pharmacology 463 phenolics 319 phenolphthalein 326 phloem 335, 338, 339 cells 133, 136, 260, 338, 353 Phoenix spacecraft 481 phosphorus 335, 366, 379 photosynthesis 85, 86, 93, 127, 128, 133, 180, 260, 304, 335, 340, 341, 343–5, 399, 401, 405, 416 phyla/phylum 93 physical changes 313 physicists 5, 6 physiologists 5, 6, 463 physiotherapists 6 pie charts 21, 528 pillow basalt 490 Pilobolus 108 pitch 249 pivot joint 380 placebo effect 525 placenta 100 placentals 100 planets 193–202

astronomy, history of 217–20 dwarf 193, 195 gas giants 195, 198–9 Kepler’s laws of planetary motion 220 terrestrial 195, 197–8 plankton 399 plant cells 122, 128, 133, 335 plant dye 334 Plantae 92, 93, 127, 128, 129 plants 333–58 botanical names 353 carnivorous 353 cells 122, 128, 133, 335 classification 353–5 common names 353 conducting tissue 338 germination 348, 349, 351, 409, 411 hydroponic 336 minerals needed by 336 nutrients 336 organs 335 photosynthesis 85, 86, 93, 127, 128, 133, 180, 260, 304, 335, 340, 341, 343–5, 399 producers 340, 399 reproduction 346–9 research 350–2 roots 335 sex organs 346 stem 338 transpiration 338 useful 334 plasma 54–5 plasma (in blood) 70, 71, 275, 368 Plasmodium 109 plastics 302 plastics optical sorting facility 62 platelets 70, 71, 137, 276 platinum 319 platyhelminthes 105 platypus 100, 101 Pleistocene epoch 102 Pliocene epoch 102 plumule 348 Pluto 193, 195, 196 plutonic rocks 489 PMI (plus, minus, interesting) 513 poles (magnetic) 146, 154, 155, 156 pollination 206, 346 pollution 414 polonium 295 polymers 302 pores 457 porifera 96, 104 porphyrin dendrimers 416 positive electric charge 423 positively charged material 423, 426 post-mortem examinations 462 potassium 293, 336, 366, 490

potential energy 229, 231 power supply 429 precipitate 316 predator 399 predictions 511 premolars 373 pressure 500 prey 399 Priestley, Joseph 261, 344 prions 92, 447, 448 proboscis 106 Procoptodon 101 producers 340, 399 products 316 properties 60 protease 375 protein 335, 364, 365, 367, 375 Protista 92, 93, 108, 109, 127, 129, 353 protons 54, 291, 307, 423 protozoa 447, 448 Proxima Centauri 472 psychologists 5, 6 pteridophytes 353 Ptolemy, Claudius 219, 220, 221, 480 pulmonary arteries 277, 280 pulmonary valve 278 pulmonary veins 277, 280 pulp (teeth) 373 pulse 278 pumice 490 Pythagoras 174, 175 Q quadrat method 392, 393 qualitative observations 14 quantitative observations 14 quarks 291 quartz 490 quartzite 490, 498 quinones 319 R radiant heat 240, 242 absorption 240, 242 infra-red scanners 241 reflection 240 transmission 240 radiation 31, 204, 241–2, 478 radicle 348 radio telescopes 469, 478–9 radio waves 478, 479 radiometer 245 radius 378, 380 rain 185, 413 rainfall patterns 413 rarefaction 247 reactants 316 receptors 244, 457

Index 567

record keeping 20, 521 rectum 371 recycling 62, 63 red blood cells 70, 130, 131, 137, 275, 276 red cabbage juice 326 red wine 326 Reeve, Christopher 139 relative dating 500 reliability (of experiments) 26, 525 renal artery 382 renal vein 382 reporting on investigations 20–4, 352, 538–9 reproduction 86, 346–9 reproductive system 265 reptiles 96, 97, 98, 278 researching SRP topic 521–3 residue 68 resistor 432 respiration 85, 86, 122, 260, 261, 267, 335, 341, 361, 382, 399 respiratory system 136, 263, 265, 267–74 responding (living things) 85 retort stand 7, 8, 20, 68 reverberation 248 Rigel 473 ringworm 108 Robertson, David 189 Robertson, Graham 416 robots 87 rock 487–502 cycle 498, 499 erosion 493, 503–4 extrusive 489 fossils in 500–2 igneous 489–91, 497 intrusive 489 layers 496 metamorphic 497–9 minerals, made of 487–8 molten 489 sedimentary 495–6, 497, 500 tracking changes in 500–1 weathering 492–3 rock pools 387, 398 rock salt 495 rocket fuels 324 root canal 373 root cortex 335 root hair cells 133 root hairs 335 roots 335 rose gold 300 roundworms 105 Ruska, Ernst 121 rust 321 rusting 321–2 Rutherford, Ernest 306–7

568

Index

S Sachs, Julius von 344 safety glasses 7, 8, 9 salinity 188–9 saliva 368, 370 salivary glands 370, 375 salt boiling point 41 contaminated water 78 melting point 41 removing from body 383 salinity of water 188–9 separating from water 72, 73 sodium chloride 297, 301 saltbush 189 saltfall 188 sample size 526 sandstone 495, 496, 497 saprophytes 397 SARS virus 454 satellites 222, 479, 481 Saturn 193, 195, 196, 198, 199, 219, 478, 480 S-bend trap 76 scavengers 398 scales, reading 16 scanning electron microscope 121 Schwann, Theodor 120 science branches of 4–6 meaning of word 2 mixing of branches 5 technology and 5 science laboratory 7–13 dangerous chemicals 9 equipment 7, 8 safety 9–12 scientists 4–6, 293 Australian 102–3 environmental 416 famous 29–31 medical science 462–3 scoria 490 sea breezes 183, 239 sea water 297 seasons 207 seatbelts 168 sector graphs 528 sediment 65, 493 sedimentary rock 495–7, 500 seed 348 seed coat 348, 349 seed dispersal 348 seedling 348 segmented worms 105 seismic waves 175 seismograms 175 seismologists 4 self-pollination 346

semicircular canals 240 semilunar valve 278 Senebier, Jean 344 sensor 15 sensory system 265 sepals 346 separating funnel 68 separating mixtures 59–63, 67–75 blood 70–1 household rubbish 63 liquid and sediment 67 recycling 62, 63 solutions 72–5 septic tank 76 series circuits 434 serum 276 sewage 76–7 sewage treatment plants 76–7 sewerage 76–7 sex cells 86 sextant 475 shale 495, 497, 500 Sharp, Julie 102 Shaw, Dr George 101 sieving 67 silicon 294, 295, 487 siltstone 495 silver 293, 294, 321 simple carbohydrates 367 single bubble maps 514 single-celled organisms 93, 108, 127, 449 sinking 48 Sirius 475 skeletal muscles 130 skeleton 95, 104, 378, 379 skin 136, 382, 457–8 cancer 414, 459–62 cells 123, 131 spray-on 462 skull 378, 379 sky maps 476 skydiving 143, 163, 164 slate 497, 498 small intestine 370, 371, 375 smoking 273–4 smooth muscle cells 130, 264 sodium 78, 293, 366 sodium bicarbonate 314, 325 sodium chloride 297, 301 sodium hydroxide 325 sodium sulfate and barium chloride 317 soil salinity 188–9 Solar and Heliospheric Observatory (SOHO) 479 solar cooker 243 solar distillation 72 solar eclipses 215 solar energy 204, 240, 243 solar radiation 182, 204

solar system 193–226, 468 Earth 205–8 historical theories 217–21 moon 209–11 planets 193–202 sun 203–4 solder 300 solids 38 changing state 40, 46 conduction in 236, 237 expansion and contraction 46, 50 melting 40, 46 particles in 43, 44, 46 rigid 43 solubility 73 soluble substances 64, 65 solute 64 solutions 64–5 separating 72–5 solvent 64, 74 sonar 254 sound 247–54 energy 246–52, 429 hearing 250–1 measuring 249 medium to travel through 247 reverberation 248 speed of 248 technology 253–4 vibrations 247 waves 247 South Celestial Pole 474, 476 South Pole 156, 175, 205 Southern Cross 469, 475, 476 Southern Hemisphere 175, 207, 475 space exploration 479–82 space probes 479, 480–1 space shuttles 152, 479 space stations 479, 481 spatula 7, 8 species 93, 104 abundance 390, 392 distribution 390, 392 extinction 414 speed of light 244, 248 speed of sound 248 sperm cells 131 spinal cord 97, 264 injury 138, 139 spiracles 106 spiral galaxies 469 spongy bone 379 spores 108, 354 sports psychologists 5, 6 sports safety 168 sports shoes 167 spreadsheets 533–4 spring balance 146, 147, 160, 161 spring tides 213

squamous cell carcinoma 459 St Martin, Alexis 371 staining specimen 125 stainless steel 300 stamen 346 starch 364, 365, 370 stars 466, 468, 469 brightness 472 constellations 469, 470, 474–5 navigation by 475 red giants 473 sky maps 476 supergiants 473 twinkling 473 white dwarves 473 static electricity 423–8 steel 62, 157, 300 stem cells 137–9 adult 137 cord blood 137 embryonic 137, 138 research 137, 138 stereomicroscope 116 stigma 346, 347 stirring rod 7, 8, 67 stomach 370, 375 stomach ulcers 462 stomata 133, 338, 340 storyboards 519 stratocumulus 178 stratosphere 180, 182 stratus 178 streak 487 streamlining 150, 151 student research project (SRP) 508–41 choosing problem 510–12 designing experiment 25–8, 524–7 mapping thoughts 514–17 organising thoughts 518–20 PMI (plus, minus, interesting) 513 possible topics 510 presenting results 528–32 record keeping 521 report 20–4, 538–9 researching topic 521–3 technology, using 533–7 thinking with different hats 517 style (plant) 346, 347 sublimation 40 sugar 364, 367, 375 sulfur 293, 294, 295, 336 sulfur dioxide 328 sulfuric acid 303, 325, 328 sun 203–4, 389, 466 air pressure affected by heat from 183 corona 215 diameter 203, 466 energy from 204, 240, 243 planets orbiting 195 radiation 182, 204, 240

rotating on axis 203 solar eclipses 215 temperature 203, 466 UV radiation 204, 319, 459, 460 sun safety 459 sunscreen 459 superfast electron microscope 121 supernova 480 super-organism 390 surface currents 178 surface protection 322 surface tension 166 suspension 65 sweat 368, 382, 457 sweat glands 457 switch 432 Sydney funnel-web spider 390 Sydney Opera House 248 symbiosis 396 synovial fluid 151, 379, 380 systolic pressure 278 T Tank Stream 76 tapeworms 396, 447, 448 technology science and 5 space and 479 using 533–7 teeth 370, 373 decay 451 fillings in 319 structure 373 telescopes 478 optical 469, 478 radio 469, 478–9 tellurium 295 temperature 15, 235 changes in 235 chemical reactions, effect on 318 Earth 176, 407 heat distinguished 235 human body 51, 97 measuring 15–16, 51, 235 sun 203, 466 tendons 378 terminal velocity 163 terrestrial planets 195, 197–8 test tube 7, 8, 9, 20 test-tube baby 138 test-tube holder 7, 8 test-tube rack 7, 8 Thales of Miletus 174 thermometer 7, 8, 15, 16, 51, 72, 235–6 bulb 236 column 236 digital 235 glass 235, 236 scale 236

Index 569

thermos flask 241 thermosphere 180, 181 Thomson, JJ 306, 307 thorax 106 Thylacoleo 101 ticklishness 457 tides 212–13 time, measuring 18 timelines 518 tin 293, 300 tinea 108, 398, 447 tissues 135, 263 tolerance range 392 tongs 7, 8 tongue 370 tooth decay 451 tooth structure 373 toothpaste 108 torch 432, 433 total lunar eclipse 214 total solar eclipse 215 toxic substances 9 trace elements 336 trace fossils 501 trachea 267, 268, 379 tracheophytes 353 traction 150 transfer of heat 40 translocation 339 transparency 487 transpiration 338 transpiration stream 338 trials 526 triceps 378 tricuspid valve 278 tripod 7, 8, 10, 20 trommel 62 trophic levels 401 troposphere 180 Trounson, Alan 138 tubers 410 tumour 459 tuning fork 249 U ulna 378, 380 ultrasound 254 ultraviolet radiation 204, 319, 459, 460 ultraviolet (UV) rays 182 umbra 215 unbalanced forces 147, 148 unicellular organisms 127, 129, 263 universal indicator 326 universe 203, 468, 469 Uranus 195, 196, 198, 199, 480 Urbani, Dr Carlo 454 urea 382

570

Index

ureters 382 urethra 382 urination 382 urine 382, 383, 452 V vacuoles 122, 123, 127, 129, 341 vacuum heat not travelling 241 light travelling 247 sound not travelling 247 Van de Graaff generator 424, 425 van Leeuwenhoek, Antonie 119, 120 variables 25, 350, 524 vascular bundles 339 vascular tissue 353 veins 275, 277 vena cava 277, 280, 382 Venn diagrams 513 Venus 195, 196, 197, 198, 204, 219, 472, 478 Venus flytrap 353 verdigris 300 vertebrae 97 vertebral column 97 vertebrates 95, 96, 97–9, 110 veterinarians 4 vibrations 247 villi 371, 372 Virchow, Rudolf 120 viroids 92 viruses 92, 120, 445, 447, 448, 453–4 vital capacity 269 vital organs 378 vitamin D 204, 366 vitamin deficiency disease 366 vitamins 366 volcanoes 4, 489, 492 volt 430, 431 Volta, Alessandro 431 voltage 430, 432, 435, 436 voltmeter 432, 435 volume 15, 39 voluntary muscles 378 Voyager space probes 480, 481 vulcanologists 4 W Warren, Robin 462 waste water treatment 76–7 watchglass 7, 8 water 36, 78, 177, 297–8, 389 boiling point 40, 41, 42 compound of oxygen and hydrogen 298 contaminated 78 country water supplies 78

dehydration 368, 383 diffusion into/out of cells 125, 263 Earth’s surface 177 evaporation 40, 72, 73 fluoride 78 freezing 40 germination, required for 349 human body, in 368, 383 melting point 40, 41 molecules 302 muddy 78, 79 osmosis 125 salinity 188–9 separating oil from 68 separating salt from 72, 73 splitting 298 Sydney tap water 78 waste water treatment 76–7 water condenser 72 water cycle 178 water-soluble vitamins 366 water stills 73 water vapour 72, 267, 405 watertable 188 waveform 249 weather 183–7 weathering 492–3 weight 160, 161 whales 95, 249, 270 white blood cells 70, 130, 137, 276 wholegrain foods 368 wind 183 wind-pollinated flowers 346 Wood, Dr Fiona 462 woolly mammoth 501 worm farms 403 worms 95, 96, 400, 402, 403 X x-axis 530 X-rays 31, 204 Xena 195 xylem 335, 338, 339 cells 133, 136, 338, 353 vessels 335, 339 Y y-axis 530 yakt 110 yeast 93, 108, 451 yoghurt 445, 451, 452 Yolngu people 217

297,

Z zinc 294, 322, 300, 366, 431 zodiac 475 zoologists 4