Science Form 3 Text Book Dlp Kssm

THEME

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Maintenance and Continuity of Life

Humans, animals and plants depend on stimuli and responses for survival. Name the organs or parts involved in the stimuli and responses based on the photographs shown.

Why is it healthier for us to exercise during the day than at night?

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Chapter Chapter

111

Stimuli and Responses

What do you know about the human nervous system? How are stimuli related to responses in humans? How are stimuli related to responses in plants? What is the importance of responses to stimuli in animals?

Let’s study Human nervous system Stimuli and responses in humans Stimuli and responses in plants Importance of responses to stimuli in animals 2

Science Gallery

Loudspeaker

Time measuring device The sprint event in international sports competitions such as the Olympics uses loudspeakers and time measuring devices as shown in the above photograph. The time measuring device measures the time interval between the sound from the loudspeaker and the first push exerted by the runner’s foot against the time measuring device. This time interval is known as the reaction time. In the 100 m sprint event at the 2016 Olympics, the reaction time of the gold medal winner, Usain Bolt, was 0.155 s. If the measured reaction time of a runner is less than 0.1 s, the runner will be disqualified from competing. Why?

Keywords Stimulus Response Spinal cord Peripheral nerve Affector Effector

Voluntary action Involuntary action Photoreceptor Taste bud Optical illusion Geotropism

Hydrotropism Thigmotropism Nastic movement Stereoscopic vision Monocular vision Stereophonic hearing 3

1.1

Human Nervous System 2 The brain interprets the impulse, estimates the speed of the shuttlecock and determines the direction and the pattern of body movement.

In a game of badminton… 1 The movement of the shuttlecock serves as a stimulus that is detected by the eye. An impulse is triggered and sent to the brain.

3 The brain then sends impulses to the hand and leg muscles to respond.

The human nervous system is an important control system in body coordination. Other than sight, thinking and body movement, the human nervous system also controls and coordinates organ functions in the body and maintains a balanced internal environment through a process. What is this process?

Structure of the Human Nervous System Look at Figure 1.1. The human nervous system consists of: Brain

Central nervous system

Cranial nerves

Spinal nerves

Peripheral nervous system consists of: • 12 pairs of cranial nerves connecting the brain to the sensory and internal organs • 31 pairs of spinal nerves connecting the spinal cord to the skeletal muscles

N CA P AG

E

S

Spinal cord

   

Peripheral nervous system

  

Figure 1.1  Human nervous system

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1.1.1

Chapter 1: Stimuli and Responses

Functions of the Human Nervous System The human nervous system controls and coordinates organs and parts of the body. The human nervous system: • detects stimuli • sends information in the form of impulses • interprets impulses • produces appropriate responses Photographs 1.1, 1.2 and 1.3 show examples of daily activities that involve detection of stimuli and production of responses to the stimuli detected. State the stimulus and response in each of the daily activities shown.

Photograph 1.1  Collecting garbage

Photograph 1.2  Sneezing 1.1.1

Photograph 1.3  Surfing the Internet

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Voluntary and Involuntary Actions The responses of the human body to stimuli can be divided into voluntary actions and involuntary actions. Observe the examples of responses of the human body in Figure 1.2.

RAFIQ

(a) Reading a book

(b) Withdrawing hand from a hot object

(c) Peristalsis in oesophagus

Figure 1.2  Examples of responses of the human body

Based on Figure 1.2, which response is a voluntary action and which is an involuntary action? Voluntary Actions Voluntary actions are conscious actions and conducted under one’s will. All voluntary actions are controlled by the brain. Examples of voluntary actions include reading, writing, speaking, eating, drinking, walking, running and exercising. Figure 1.3 shows the pathway of impulse in a voluntary action.

Affector (receptor) in human ear

Stimulus

ne r v e im

puls

e

Phone rings

Effector (muscle or gland)

Response

e im ne r v

puls

e

Brain

Touch the screen Direction of the pathway of impulse from the affector (receptor) to the effector

Figure 1.3  Pathway of impulse in a voluntary action

Let us learn more on voluntary actions by carrying out Activity 1.1 on page 7. 6

1.1.2

Chapter 1: Stimuli and Responses

Activity 1.1

Inquiry-based activity

Measuring the reaction time by catching a free-falling ruler (voluntary action) Aim: To measure reaction time Apparatus Half metre rule

Safety Precautions • Make sure that the hand used to catch the ruler remains stationary on the table. • Be careful when releasing or catching the ruler.

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Instructions 1. Work with a partner. 2. Ask your partner to hold the end of a half metre rule as shown in Figure 1.4.

Table

Figure 1.4 3. Place your hand at the end of the ruler close to the zero mark without touching it as shown in Figure 1.4. 4. Your partner will release the ruler without warning and you must try to catch the ruler as quickly as possible. 5. Record the distance the ruler fell, x, that is, the scale on the ruler when you catch it. The distance, x, is the measurement of your reaction time. 6. Repeat this activity four times. Then, calculate the average distance, xaverage. Questions 1. In this activity, state the stimulus and its response. Is the response a voluntary action or an involuntary action? Explain. 2. Why is the distance the ruler fell considered as the reaction time? 3. Explain the difference in the reaction time among the students in the class. 4. What is the importance of reaction time in our daily life? Conclusion Make a conclusion on the reaction time of the students in your class. 1.1.2

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Involuntary Actions Involuntary actions are actions that occur immediately without conscious control or prior thoughts. Involuntary actions can be classified into two.

SCIENCE INFO

Involuntary actions Involving medulla oblongata • Heartbeat • Breathing • Peristalsis • Secretion of saliva

Medulla oblongata

Spinal cord Involving spinal cord (reflex actions) • Withdrawing hand when it accidentally touches a hot object • Withdrawing foot when it accidentally steps on a sharp object • Sneezing when dust enters the nose

Affector (receptor)

Spinal cord

Hot object Effector

Direction of impulse

Direction of impulse from the affector (receptor) to the effector

Figure 1.5  Pathway of impulse in an involuntary action (reflex action)

Let us learn more on involuntary actions by carrying out Activity 1.3 on page 9.

Activity 1.2 Create a presentation on: • the parts involved in the transmission of impulse from the affector to the effector • the pathway of impulses in voluntary and involuntary actions

• ICS • Innovationbased activity

Instructions 1. Work in groups. 2. Each group is required to create a presentation to illustrate the following: • The parts involved in the transmission of impulse from the affector to the effector • The pathway of impulses in voluntary and involuntary actions

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1.1.2

Chapter 1: Stimuli and Responses

Activity 1.3

Inquiry-based activity

Detecting changes in the size of the pupil in the eye towards light intensity (involuntary action) Aim: To observe changes in the size of the pupil of the eye towards different light intensities Apparatus Mirror and lamp Instructions 1. Identify the pupil of the eye in Figure 1.6.

Pupils



Figure 1.6

2. Observe the pupil using a mirror in bright light. Sketch the size of the pupil. 3. Observe the pupil in dim light. Sketch the size of the pupil. 4. Compare and contrast the size of the pupils in bright and dim lights. Questions 1. In this activity, state the stimulus and its response. Is the response a voluntary or an involuntary action? Explain. 2. What is the relationship between the size of the pupil and light intensity? 3. What is the importance of this response? Conclusion Make a conclusion about the changes in the size of the pupil towards light intensity.

SCIENCE INFO The pupil in the human eye is circular. Is the pupil in other animals’ eye circular as well?

(a) Goat: Rectangular

1.1.2

(b) Stingray: Crescent

(c) Crocodile: Vertical slit

(d) Squid: W-shaped

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BRAIN TEASER Other than the nervous system, what other body systems help in body and internal organ movements?

- Science, Technology, Engineering, Mathematics N CA

The network of the human nervous system controls and coordinates the organs and parts of the body to carry out processes in the body such as breathing and body movements. A damaged nervous system normally causes a person to become temporarily, partially or completely paralysed. For example, if the nerves in the muscles of a leg or hand are injured, the person will face difficulty in moving his leg or hand. In the case of a more serious problem, he might have to depend on machines to carry out his physiological processes such as breathing or heart beating. Humans are blessed with a nervous system, so they should use and take good care of it.

G

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Humanoid robot

Importance of the Network of Human Nervous System in Daily Life

          PA

Photograph 1.4  Partiallyparalysed individual

Formative Practice

Photograph 1.5  Patient using a breathing machine

1.1

1. State two main parts of the human nervous system. 2. (a) What is voluntary action? Give one example of a voluntary action. (b) What is involuntary action? Give one example of an involuntary action. 3. What happens if a person has brain injury? 4. What is the importance of the network of human nervous system in life? 10

1.1.3

Chapter 1: Stimuli and Responses

1.2

Stimuli and Responses in Humans

Humans face constant changes in surroundings. These changes are called stimuli. Examples of stimuli include light, sound and chemical substances. Humans use their sensory organs to detect stimuli. Humans have five sensory organs: eyes, ears, nose, skin and tongue as shown in Photograph 1.6. Which sensory organ is the largest? Eyes (sense of sight) Ear (sense of hearing) Nose (sense of smell) Tongue (sense of taste) Skin (sense of touch)

Photograph 1.6  Human sensory organs

Eye Study Figure 1.7. Can you identify the parts of the eye? Let us learn more on the parts of the eye by referring to Figure 1.8 on page 12.

Sclera

Iris

Pupil

Figure 1.7  Front view of the eye 1.2.1

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12 Suspensory ligaments

Ciliary muscle

Eye lens

Sclera

Choroid

Muscle that changes the thickness of the eye lens through contractions and relaxations.

Transparent and elastic convex lens which focuses light onto the retina.

Strong layer that maintains the shape of the eye and protects it.

Black layer that prevents reflection of light in the eye and supplies oxygen and nutrients to the eye.

Strong fibres which hold the eye lens in its position.

Retina Layer containing photoreceptors which detects light and produces nerve impulses.

Cornea Transparent layer which refracts and focuses light onto the retina.

Yellow spot Part of the retina which is most sensitive to light as it has many photoreceptors.

Iris The coloured part of the eye which controls the size of the pupil.

Optic nerves Nerve fibres which carry nerve impulses from the retina to the brain to be interpreted.

Pupil Opening in the centre of the iris which controls the quantity of light entering the eye.

Aqueous humour Transparent fluid which maintains the shape of the eyeball and focuses light into the eye.

Conjunctiva Transparent membrane which protects the front part of the sclera.

Vitreous humour

Blind spot

Transparent jelly-like substance which maintains the shape of the eyeball and focuses light onto the retina.

Part of the retina which is not sensitive to light as there are no photoreceptors and an exit point for all optic nerve fibres.

1.2.1

Figure 1.8  Parts of the human eye and their functions

Chapter 1: Stimuli and Responses

What is the Colour of the Object Seen? The retina has two types of photoreceptors: rod cells and cone cells as shown in Figure 1.9. Rod cells are sensitive to different light intensities including faint light but are not sensitive to the colours of light. Cone cells are sensitive to the colours of light under bright conditions. There are three different types of cone cells, with each is sensitive to red light, green light and blue light.

Rod cell

Light

Cone cell

Vitreous humour

Sclera Choroid

Retina

Figure 1.9  Photoreceptors – rod and cone cells

Ear What are the parts of the ear and their functions? Study Figure 1.10 and Table 1.1 on page 14. Outer ear

Middle ear

Ossicles

Inner ear

Semicircular canals

Auditory nerve Cochlea

Earlobe

Ear canal

Eardrum

Oval window

Eustachian tube

Figure 1.10  Parts of the human ear 1.2.1

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Table 1.1  Functions of the parts of the human ear Part of ear Outer ear

Middle ear

Inner ear

Structure of ear

Functions

Earlobe

Collects and directs sound waves into the ear canal

Ear canal

Directs sound waves to the eardrum

Eardrum (thin membrane)

Vibrates according to the frequency of the sound waves received and transfers the vibrations to the ossicles

Ossicles (made up of three small bones)

Amplify sound vibrations and transfer them to the oval window

Oval window

Collects and transfers sound vibrations from the ossicles to the cochlea

Eustachian tube

Balances the air pressure on both sides of the eardrum

Cochlea (contains fluid)

Detects and converts sound vibrations into nerve impulses

Semicircular canals (contain fluid)

Detect the position of the head and help to balance the body

Auditory nerve

Sends nerve impulses from the cochlea to the brain to be interpreted

Nose What are the parts of the nose? Study Figure 1.11. Nerve Nerves to the brain Nasal cavity

rs

nte

e Air

Nose Sensory cells for smell

Mucous

Sensory cells for smell (smell receptors)

Tongue Nostrils

Figure 1.11  Parts of the human nose

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1.2.1

Chapter 1: Stimuli and Responses

Structure of the Nose The nose is the sensory organ of smell. Smells are chemical substances present in the air. About 10 million sensory cells for smell are located at the roof of the nasal cavity as shown in Figure 1.11.

BRAIN TEASER Why is a person suffering from flu normally unable to detect smells?

Function of Sensory Cells for Smell Sensory cells for smell are tiny and covered with a layer of mucous. Chemical substances in the air will dissolve in this layer of mucous and stimulate the cells to produce nerve impulses. The nerve impulses are then sent to the brain to be interpreted to determine the type of smell.

Tongue What are the parts of the tongue? Study Figure 1.12.

Pore Supporting cell

Taste receptor

Papillae on the tongue

Tongue

Taste bud on the papillae

Nerves to the brain

Figure 1.12  Parts of the human tongue

Structure of the Tongue The tongue is the sensory organ of taste. Observe the surface of your tongue using a mirror. There are tiny nodules known as papillae on the surface of the tongue. The surface of a papillae is covered by hundreds of taste buds. Each taste bud contains 10 to 50 taste receptors. These taste receptors can detect five types of basic tastes which are sweet, salty, sour, bitter and umami.

SCIENCE INFO Umami is classified as a basic taste because there are taste receptors that can only detect umami taste. This is the same as other basic tastes such as sweet, salty, sour and bitter. Umami taste is related to delicious tastes such as the taste of meat in soups or the taste of fermented foods such as cheese and mushrooms or monosodium glutamate (MSG).

Function of Taste Buds When food is chewed, part or all the chemical substances in the food dissolve in the saliva. These dissolved chemical substances will diffuse into the taste buds through their pores and stimulate the taste receptors in them to produce nerve impulses. These nerve impulses are then sent to the brain to be interpreted as sweet, salty, sour, bitter, umami tastes or a combination of the basic tastes. 1.2.1

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Skin What are parts of the skin? There are five types of receptors found in the skin. What are their functions? Study Figure 1.13. Pain receptor

Cold receptor

Detects stimuli that causes pain

Detects cold stimuli Hair

Oil gland

Epidermis

Heat receptor Detects heat stimuli Dermis

Touch receptor Detects touch stimuli Fat layer

Nerve

Pressure receptor Detects pressure exerted

Figure 1.13  Parts of the human skin

The skin is the largest sensory organ in the human BRAIN body. The human skin is made up of a thin outer layer TEASER known as epidermis and an inner layer known as dermis. How does the skin function as a The skin has five types of receptors at different positions sense of ‘sight’ for the blind? to detect different stimuli as shown in Figure 1.13. State the five types of stimuli which can be detected by the receptors in the skin. When the receptor in the skin is stimulated, nerve impulses are produced and sent through the nervous system to the brain to be interpreted and to produce an appropriate response. 16

1.2.1

Chapter 1: Stimuli and Responses

Mechanism of Hearing How do we hear? Study Figure 1.14. Ossicles

Brain Auditory nerve Cochlea

Earlobe

Source of sound

Eardrum

vibrations Eardrum

Ear canal

Auditory nerve

The nerve impulses are then sent through the auditory nerve to the brain to be interpreted.

Ossicle bones

The vibrations are amplified by the ossicles and then sent to the cochlea through the oval window.

nerve impulses

vibrations Cochlea

vibrations

Ear canal channels the sound waves to the eardrum causing it to vibrate.

nerve impulses Brain

Direction of sound

Oval window

sound

sound Earlobe

Earlobe receives and gathers sound waves.

Sound is interpreted

Ear canal

Oval window

Nerve cells in the cochlea convert the sound vibrations to nerve impulses.

Figure 1.14  Mechanism of hearing in humans

Activity 1.4 To study the mechanism of hearing using a model

• CPS, ICS

Instructions • Innovationbased activity 1. Work in groups. 2. Each group is required to present the mechanism of hearing using a model prepared by the teacher. 3. Construct a flow chart that shows the direction of sound in the mechanism of hearing. 1.2.2

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Mechanism of Sight How do we see? Study Figure 1.15. Ciliary muscle Light rays from an object

Vitreous humour Retina

Cornea

Brain

Aqueous humour

Eye lens Optic nerves Light rays from an object enter the eye through the cornea, aqueous humour, eye lens and vitreous humour before reaching the retina. These parts of the eye focus the light rays from the object onto the retina. The object appears smaller and inverted.

The light rays stimulate photoreceptors to produce nerve impulses that are sent to the brain.

The brain interprets the nerve impulses. The smaller inverted image on the retina will then appear upright.

Figure 1.15  Mechanism of sight in humans

Activity 1.5 To study the mechanism of sight using a model

• CPS, ICS

Instructions • Innovationbased activity 1. Work in groups. 2. Each group is required to present the mechanism of sight using a model prepared by the teacher. 3. Construct a flow chart that shows the direction of light in the mechanism of sight.

Photograph 1.7  A human eye model

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1.2.2

Chapter 1: Stimuli and Responses

Sensitivity of the Skin on Different Parts of the Body towards Stimuli Photograph 1.8 shows a few examples of daily activities of humans which make use of the sensitivity of skin on different parts of the body towards different stimuli.

Photograph 1.8  Sensitivity of the skin on different parts of the body

Why are the daily activities shown in Photograph 1.8 carried out on different parts of the body? Let us investigate this in Activity 1.6.

Activity 1.6

Inquiry-based activity

To investigate the sensitivity of the skin on different parts of the body towards the touch stimulus Material Cellophane tape Apparatus Ruler (30 cm), toothpick and handkerchief (or blindfold) Instructions 1. Work in pairs. 2. Set up the apparatus as shown in Figure 1.16. Toothpick 2

Cellophane tape



1.2.3

Toothpick 1

Ruler 0

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Toothpick 3

Figure 1.16 Using the cellophane tape, attach: • Toothpick 1 on the 0 mark of the ruler. • Toothpick 2 opposite the first toothpick on the ruler. • Toothpick 3 on the 0.5 cm mark of the ruler.

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3. Cover your partner’s eyes with a handkerchief. 4. Prick the back of your partner’s hand with one or two toothpicks as shown in Figure 1.17.

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• Hold the sharp end of the toothpick with care. • Do not press the sharp end of the toothpick too hard onto the skin. • Throw away all used toothpicks into the rubbish bin.

Figure 1.17 5. 6. 7.

Ask your partner if he or she feels it as one or two toothpicks. Mark ‘•’ if the answer is correct and ‘×’ if the answer is wrong in the table below. Repeat steps 4 and 5 three times. Repeat steps 4 to 6 on different parts of the body such as the tip of the index finger, elbow and arm. Touch stimulus by using Part of Body

one toothpick 1st attempt

2nd attempt

two toothpicks 3rd attempt

1st attempt

2nd attempt

3rd attempt

Back of the hand Tip of the index finger Elbow Arm Questions 1. At which part or parts of the body is the skin most sensitive to touch stimulus? Explain your observation. 2. At which part or parts of the body is the skin least sensitive to touch stimulus? Explain your observation. 3. Which type of receptor is stimulated in this activity? 4. State two factors that affect the sensitivity of skin on different parts of the body towards touch stimulus.

The sensitivity of skin towards stimuli depends on the number of receptors and the thickness of the skin epidermis. For example, the tip of the finger is very sensitive towards touch because at the tip of the finger, there is a large number of touch receptors and the epidermis is thin. The tongue, nose and lips are also very sensitive to touch. The elbow, the sole of the foot and the back of the body are less sensitive to touch. Why? 20

1.2.3

Chapter 1: Stimuli and Responses

Sensitivity of the Tongue towards Different Taste Stimuli The tongue can detect five types of tastes which are sweet, salty, sour, bitter and umami. Each type of taste is detected by a different receptor. Let us investigate the areas of the tongue that detect different tastes in Activity 1.7.

Activity 1.7

Inquiry-based activity

To show that the sensitivity of the tongue towards taste stimuli is related to the number of receptors Materials Sugar solution (sweet), salt solution (salty), lime juice (sour), strong coffee without sugar (bitter), mushroom soup (umami) and distilled water

Do not taste any chemical substance in the laboratory without your teacher’s permission.

Apparatus Drinking straw, handkerchief (or blindfold) and six cups Instructions 1. Work in pairs. Your teacher will provide each pair of students with five solutions of different tastes which are sweet, salty, sour, bitter and umami, in different cups. 2. Cover your partner’s eyes with a handkerchief. 3. Ask your partner to gargle with distilled water. 4. Using a drinking straw, place a drop of sugar solution on part A of his tongue as shown in Figure 1.18. 5. Ask your partner to identify the taste of the solution without pulling the tongue back into the mouth. 6. Mark ‘•’ if your partner correctly identifies the taste of the solution and ‘×’ if your partner incorrectly or fails to identify the taste of the solution in a table as shown below. 7. Repeat steps 3 to 6 on parts B, C, D and E. 8. Repeat steps 3 to 7 using the four other solutions provided. Part of the tongue A

Sweet

Salty

Type of taste Sour

Photograph 1.9

E

C B

D

C B

A

Figure 1.18 Bitter

Umami

B Questions 1. Why does your partner have to gargle each time before tasting the solutions? 2. Which part of the tongue is able to identify all the tastes of the solutions? 3. Which part of the tongue is most sensitive to taste? Explain your observation. 4. Which part of the tongue is least sensitive to taste? Explain your observation. 5. What conclusion can you make from this activity? 1.2.3

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Different Areas of the Tongue are More Sensitive to Specific Taste

KEY:

Areas of the tongue are sensitive to all five tastes. However, different areas of the tongue have different sensitivities towards specific taste. For example, the area in front of the tongue is more sensitive to sweet taste whereas the sides are more sensitive to sour and salty tastes. The area at the back of the tongue is more sensitive to bitter taste. The area at the centre of the tongue, however is more sensitive to umami taste. Study Figure 1.19.

BRAIN TEASER

Bitter Sour Sweet Salty Umami

Figure 1.19  Different areas of the tongue are more sensitive to specific taste

Nowadays, there is a toothbrush equipped with a tongue cleaner. Does the use of the tongue cleaner reduce the sensitivity of the tongue?

Combination of the Sense of Taste and the Sense of Smell Look at Photograph 1.10. Can the child enjoy the fried chicken? Does the sense of smell play a role when a person tastes food? Let us investigate this matter in Activity 1.8.

Activity 1.8

Photograph 1.10  Food eaten without smelling

Inquiry-based activity

To investigate the relationship between sense of taste and sense of smell Materials Cordial drinks of different flavours (grape, orange, mango, strawberry) and distilled water Apparatus Handkerchief (or blindfold) and cups Instructions 1. Work in pairs. Your teacher will provide each pair of students with cordial drinks of different flavours such as grape, orange, mango and strawberry in different cups. 2. Cover the eyes of your partner with a handkerchief and ask him to pinch the nose as shown in Photograph 1.11. 3. Give your partner a cup of distilled water and ask him to gargle.

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1.2.3

Chapter 1: Stimuli and Responses

4. Give your partner a cup of grape-flavoured cordial drink and ask him to identify and state the flavour of the cordial in the given cup. 5. Mark ‘•’ if your partner answers correctly and ‘×’ if your partner is unable or fails to answer correctly in a table as shown below. 6. Repeat steps 3 to 5 using cordial drink of other flavours. 7. Repeat steps 2 to 6 without pinching the nose. Condition Flavour of cordial drink of the Grape Orange Mango Strawberry nose

Photograph 1.11

Pinched Without being pinched

Make sure your partner is not allergic to all the flavours of the cordial drinks investigated.

Questions 1. Under what condition is your partner able to identify the flavours of the cordial drinks more easily, with his nose pinched or not being pinched? 2. State one inference based on your answer. 3. Why should your partner’s eyes be covered in this activity? 4. Why does hot food taste better?

Case Study 1. The judges in a cooking competition as shown in Photograph 1.12 use several types of senses. (a) State the types of senses used by the judges to carry out their evaluation. (b) What sensory organs are related to the sense of taste? 2. Have you ever carried out the daily activity as shown in Photograph 1.13? (a) What is the combination of senses used in this activity? (b) What is the importance of the combination of sensory organs in carrying out this activity?

Photograph 1.12

Photograph 1.13 1.2.3

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How do Limitation of Senses, Defect in Sensory Organs and Ageing Affect Human Hearing and Sight? Audio visual which combines the senses of hearing and sight, plays an important role in daily life. Let us investigate how limitation of senses, defect in sensory organs and ageing affect the sensitivity of hearing and sight of humans.

SCIENCE INFO Audio visual refers to the use of two components, sound component (audio) and graphic component (visual).

Limitations of Sight

Limitation of sight is the limitation in the ability of the eye to see objects. We cannot see very tiny objects such as microorganisms as well as very distant objects such as planet Jupiter. Limitations of sight include optical illusions and blind spot.

Optical Illusions

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Y Q

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(a) Which line is longer?

(b) Which spot in the centre is larger?

(c) Are the sides of the square straight or curved?

Figure 1.20  Optical illusions

Look at Figure 1.20 and answer the questions given. Check your answer using a straight ruler. Is your answer correct or wrong? Why? Optical illusion occurs when an object that is seen differs from its actual state. Optical illusion occurs because the brain is unable to accurately interpret the object seen by the eye due to distractions around the object. Look at Figure 1.21.

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Optical illusion

Without optical illusion

P

R

P

R

Q

S

Q

S

With distractions around straight lines PQ and RS

Without distractions around straight lines PQ and RS

Figure 1.21 Factor causing an optical illusion 1.2.4

Chapter 1: Stimuli and Responses

Blind Spot Refer to the blind spot shown in Figure 1.8 on page 12. Why are images that fall on the blind spot invisible? We are unaware of the presence of the blind spot in the eye because it is not possible for the image of the same object to fall on the blind spots of both eyes simultaneously. Carry out the following simple activity to investigate the blind spot.

Figure 1.22  Investigating the blind spot

Instructions 1. Hold this book with your right hand and straighten your arm. 2. Cover your left eye and look at the cat in Figure 1.22 with your right eye. 3. Move this book slowly towards your eyes. Does the bird disappear from your sight at a certain position? Why? Photograph 1.14 shows examples of various devices used to overcome the limitations of sight. Name these devices. Gather information on the use of these devices from the Internet, magazines, books, newspapers and other sources. Discuss the information gathered. Present the findings of your discussions collaboratively using multimedia presentation.

Binoculars

Scanning electron microscope

Light microscope

Ultrasound machine

X-ray machine

Photograph 1.14  Examples of devices to overcome limitations of sight 1.2.4

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Defects of Sight and Ways to Correct Them Defects of sight include short-sightedness, long-sightedness and astigmatism. How can these defects of sight be corrected? Study Table 1.2. Table 1.2  Defects of sight and ways to correct them Defect of sight

How it is corrected

Short-sightedness (a) Inability to see distant objects clearly. (b) Distant objects appear blurry because the image is focused in front of the retina. (c) This defect is caused by the eye lens being too thick or the eyeball being too long.

Short-sightedness can be corrected using concave lens.

Eye lens too thick

Distant object

Distant object Image formed in front of the retina

Concave lens

Image formed on the retina

Eyeball too long

Distant object

Distant object

Long-sightedness (a) Inability to see near objects clearly. (b) Near objects appear blurry because the image is focused behind the retina. (c) This defect is caused by the eye lens being too thin or the eyeball being too short.

Long-sightedness can be corrected using convex lens.

Eye lens too thin Near object Near object Image formed behind the retina

Convex lens

Image formed on the retina

Eyeball too short Near object Near object

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1.2.4

Chapter 1: Stimuli and Responses Defect of sight

How it is corrected

Astigmatism (a) Seeing part of an object clearer than the rest of the object (b) This defect is caused by the uneven curvature of the cornea or eye lens. 11

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Astigmatism can be corrected using cylindrical lenses.

1 2

10

3

9 8

Cylindrical lens

4 7

6

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Figure 1.23 Test your eyes by looking at Figure 1.23. Can you see all the lines clearly? If you cannot, you have astigmatism.

Today in history

Limitations of Hearing Limitations of hearing are limitations in the ability of the ear to hear sound. We can only hear sounds of frequencies between the range of 20 Hz to 20 000 Hz. The ears are unable to detect sounds which lie outside this frequency range. The frequency range of hearing of every individual is different. When a person gets older, the frequency range of his hearing gets narrower as his eardrum becomes less elastic. Examples of devices invented and used to overcome the limitations of hearing are shown in Photograph 1.15.

The first stethoscope made of wood was invented by Rene Laennec at Necker-Enfants Malades Hospital, Paris in 1816.

A loudspeaker amplifies sound so that it can be heard from far away.

Stethoscope helps us to listen to the heartbeats.

Photograph 1.15  Examples of equipment used to overcome limitations of hearing 1.2.4

27

Defects of Hearing and Ways to Correct Them Defects of hearing occur when the sense of hearing of a person does not function well. Defects of hearing are normally caused by damage to the ear due to infection by microorganisms, injury, ageing process or continuous exposure to loud sounds. Damages to the outer ear and middle ear can be corrected easily. For example, the clearing of foreign objects in the ear canal. Punctured eardrum and damaged ossicles can also be corrected using medicine or surgery. Damage to the inner ear is more difficult to correct. A damaged cochlea can be corrected using a cochlear implant but a damaged auditory nerve cannot be corrected using medicine or surgery. Photograph 1.16 shows how innovation and technology are applied to invent smaller and more sophisticated hearing aids.

Photograph 1.16 Advancements in hearing aids

The Five Senses – a Gift The five senses is a gift from God that we should appreciate. However, unhealthy lifestyles and high risk careers can affect the sensitivity of the sensory organs. Based on Photographs 1.17 and 1.18, • name the sensory organ whereby the sensitivity is affected in each situation. • describe how each situation can affect the sensitivity of the sensory organ. • what are the devices or safety measures taken to maintain the safety and health of the sensory organ in each situation?

Photograph 1.17 Unhealthy lifestyle

Photograph 1.18 High risk careers

28

1.2.5

Chapter 1: Stimuli and Responses

Activity 1.9 Instructions • CPS, ISS, ICS 1. Work collaboratively in groups. • Technology 2. Each group is assigned by your teacher to create a multimedia based activity presentation such as MS PowerPoint or animation on one of the following topics: • Optical illusion and blind spot • Various types of audio visual defects such as short-sightedness, long-sightedness, astigmatism and defects of hearing • Correction of audio visual defects using concave lenses, convex lenses and hearing aids • Examples and effects of unhealthy lifestyles or high risk careers that can affect the sensitivity of the sensory organs • The five senses – a gift and the importance of practising safety and healthcare of the sensory organs

Formative Practice 1.2 1. Complete the following mechanism of sight. Light



Aqueous Humour

  (a)

  (b)

Eye lens

  (c)

Optic nerve

Vitreous Humour

  (d)

2. Which structure of the ear, if damaged, will not influence the mechanism of hearing? 3. Where is the sensory cell for smell located? 4. State the five tastes that can be detected by the tongue. 5. State two factors that influence the sensitivity of the skin to stimuli. 6. (a) State the type of stimulus that can be detected by the tongue. (b) Explain how the stimulus in question 6 (a) can be detected. 

29

1.3

Stimuli and Responses in Plants

Will a plant grow faster if we talk to it?

Hello plant, please grow faster!

Like humans and animals, plants can also detect stimuli and respond to them. The stimuli that can be detected by plants include light, water, gravity and touch. The responses of plants can be divided into two as shown in Figure 1.24.

After a week… Why is the stimulus given not effective?

Responses Responses of of plants plants

Nastic movement

Tropism

Tropism

Figure 1.24  Responses of plants to stimuli

Tropism is a directional response of plants to stimuli such as light, water, gravity and touch coming from a certain direction. A certain part of a plant will grow towards or move away from the detected stimulus. The part of a plant which grows towards a stimulus is known as positive tropism whereas the part of a plant which grows away from a stimulus is known as negative tropism. The directional response of plants normally occurs slowly and less significantly. Let us carry out Experiment 1.1 to determine the direction of response of plants to light, water, gravity and touch.

Experiment 1.1 A Response of plants towards light or phototropism

Aim: To study the response of plants to light

Problem Statement: Which part of plants responds to light? Hypothesis: Shoots of plants grow in the direction of light. Variables (a) manipulated variable : Direction of light towards the shoots of the seedlings (b) responding variable : Direction of growth of the shoots of the seedlings (c) constant variables : Seedlings of the same type and height, volume of water

30

1.3.1

1.3.2

1.3.3

Experiment Chapter 1: Stimuli and Responses

Materials Green pea seedlings, soil, water and three boxes (one box with an opening at the top and two other boxes with openings at the side) Apparatus Three beakers Procedure Light

Green pea seedlings Light

Light

Beaker Box A

Beaker Box B

Beaker Box C

Figure 1.25 1. Set up the apparatus as shown in Figure 1.25. 2. Observe and sketch the positions of the shoots of the seedlings in boxes A, B and C. 3. Keep all three boxes in the laboratory for five days. Keep the soil moist by watering it with the same amount of water daily. 4. After five days, observe and sketch the positions of the shoots of the seedlings in boxes A, B and C. Conclusion Is the hypothesis accepted? What is the conclusion of this experiment? Questions 1. What is the stimulus used in this experiment? 2. State the part of the plant that responds to the stimulus. 3. Does the part of the plant in question 2 show positive or negative phototropism? Explain your answer.

B Response of plants to gravity or geotropism Aim: To study the response of plants to gravity Problem statement: Which part of plants responds to gravity? Hypotheses: (a) Roots of plants grow in the direction of gravity. (b) Shoots of plants grow in the opposite direction of gravity. Variables (a) manipulated variable : Position of the seedlings relative to the direction of gravity (b) responding variable : Direction of growth of the roots and shoots of the seedlings (c) constant variables : Presence of water, absence of light, seedlings with straight roots and shoots Materials Green pea seedlings with straight roots and shoots, moist cotton wool and plasticine 1.3.1

1.3.2

1.3.3

31

Experiment Apparatus Petri dish Procedure 1. Set up the apparatus as shown in Figure 1.26. Make sure that the green pea seedlings are arranged in different positions in the Petri dish. 2. Observe and sketch the position of the shoots and roots of the seedlings in the Petri dish. 3. Keep the apparatus in a dark cupboard for two days. 4. After two days, observe and sketch the position of the shoots and roots of the seedlings in the Petri dish.

Petri dish Moist cotton wool Seedlings with straight roots and shoots

Plasticine

Figure 1.26 Conclusion Are the hypotheses accepted? What is the conclusion of this experiment? Questions 1. Why is the apparatus kept in a dark cupboard? 2. Based on your observations, state the direction of growth of the: (a) shoots of the seedlings (b) roots of the seedlings 3. Do plants show positive geotropism or negative geotropism? Explain your answer.

C

Response of plants to water or hydrotropism

Aim: To study the response of plants to water Problem statement: Which part of plants responds to water? Hypothesis: Roots of plants grow in the direction of water. Variables (a) manipulated variable : Presence of a source of water (b) responding variable : Direction of growth of roots of seedlings (c) constant variables : Gravity, absence of light and seedlings with straight roots Materials Green pea seedlings with straight roots, moist cotton wool and anhydrous calcium chloride Apparatus Rough wire gauze and two beakers Procedure 1. Set up the apparatus as shown in Figure 1.27. 2. Observe and sketch the positions of the roots of the seedlings in beakers X and Y. 3. Keep both beakers X and Y in a dark cupboard. 4. After two days, observe and sketch the positions of the roots of the seedlings in beakers X and Y.

32

1.3.1

1.3.2

1.3.3

Experiment Chapter 1: Stimuli and Responses

Moist cotton wool Seedlings with straight roots Wire gauze Water

X

Anhydrous calcium chloride

Y

Figure 1.27 Conclusion Is the hypothesis accepted? What is the conclusion of this experiment? Questions 1. What is the stimulus used in this experiment? 2. State the part of the plant that responds to the stimulus. 3. What is the function of the anhydrous calcium chloride in beaker Y? 4. Does the part of the plant in question 2 show positive or negative hydrotropism? Explain your answer.

Plants need to be responsive towards stimuli such as light, gravity and water so that they can respond appropriately to ensure their sustainability and survival. Why do plants need light and water? Name one stimulus that can be detected by plants but not investigated in Experiment 1.1. Phototropism Phototropism is the response of plants towards light. Shoots of plants show positive phototropism which is growth towards the direction of light (Photograph 1.19). As plants need light to carry out photosynthesis, positive phototropism ensures that shoots and leaves of plants obtain enough sunlight to make food through photosynthesis.

Source of light

Grow towards light

Photograph 1.19 Shoots of plants show positive phototropism

Hydrotropism Hydrotropism is the response of plants towards water. Roots of plants show positive hydrotropism which is growth towards the direction of water (Figure 1.28). Positive hydrotropism allows roots of plants to obtain water to carry out photosynthesis and absorb dissolved mineral salts to stay alive.

Water Moist soil

Positive hydrotropism (Grow towards water)

Figure 1.28 Roots showing positive hydrotropism 1.3.1

1.3.2

1.3.3

33

Geotropism Geotropism is the response of plants towards gravity. Roots of plants show positive geotropism which is downward growth towards the direction of gravity. Positive geotropism allows the roots of plants to grow deep into the ground to grip and stabilise the position of the plant in the ground. On the other hand, shoots of plants show negative geotropism which is upward growth in the opposite direction of gravity. Negative geotropism allows the shoots and leaves of plants to grow upwards to obtain sunlight for photosynthesis (Figure 1.29).

Positive geotropism (Grow in the direction of gravity)

Negative geotropism (Grow in the opposite direction of gravity)

Figure 1.29  Roots show positive geotropism whereas shoots show negative geotropism

Thigmotropism Thigmotropism is the response towards touch. Tendrils or twining stems show positive thigmotropism when they cling onto whatever objects or other plants they come into contact (Photograph 1.20). This response enables plants to grow upwards to obtain sunlight and grip objects to obtain support. Roots show negative thigmotropism since they avoid any object that obstructs their search for water.

(a) Cucumber plant has tendrils that twine around objects in contact with it

(b) Morning glory plant has stems that twine around objects in contact with it

Photograph 1.20 Tendrils and stems which twine around objects show positive thigmotropism

34

N CA

E

Nastic movement of the Mimosa sp.

G

Nastic movement is the response towards a stimulus such as touch but does not depend on the direction of the stimulus. What are other stimuli that can cause nastic movement? Why is nastic movement not a type of tropism? Nastic movement occurs more rapidly than tropism. For example, the Mimosa sp. responds to touch by folding its leaves inwards when touched as shown in Photograph 1.21. This nastic movement serves as a defence of the Mimosa sp. against its enemies and strong wind.

S

Nastic Movement

          PA

1.3.1

1.3.2

Chapter 1: Stimuli and Responses

Photograph 1.21  Nastic movement of a leaf of Mimosa sp.

Activity 1.10 To investigate responses of plants in different situations The responses of plants towards the earth’s gravity and the period of exposure to sunlight in a day influence the growth of shoots and roots of plants. These ensure the sustainability and survival of the plants. At the International Space Station (ISS), scientists investigate the growth of plants in the following situations: (a) no gravity (b) period of exposure to sunlight

• CPS • Inquiry-based activity

Instructions Photograph 1.22 A scientist carrying 1. Work in groups. out investigations at the ISS 2. Gather information on the results of the investigations of the scientists on the growth pattern of shoots and roots of plants towards stimuli (gravity and sunlight). 3. Present the outcome of the discussion of each group using multimedia presentation.

Formative Practice 1.3 1. (a) What is tropism? (b) State the type of tropism towards the following stimuli: (i) Touch (ii) Gravity (iii) Light 2. (a) Which parts of a plant show: (i) positive phototropism? (ii) positive geotropism? (iii) positive thigmotropism? (b) What is the importance of hydrotropism to plants? 3. State one similarity and one difference between the responses of tropism and nastic movement. 1.3.1

1.3.2

1.3.3

35

1.4

Importance of Responses to Stimuli in Animals

Stereoscopic and Monocular Visions Study Figure 1.30 to understand stereoscopic and monocular visions. Table 1.3 shows the characteristics and importance of stereoscopic and monocular visions in animals.

• Humans and animals such as cats and owls have a pair of eyes located in front of their head. • They have stereoscopic vision.

What is the importance of the location of eyes to humans and animals?

LIM

• Animals such as rats, chickens and rabbits have a pair of eyes located on opposite sides of their head. • They have monocular vision.

Large overlap

Small overlap

Field of monocular vision

Field of monocular vision

Field of stereoscopic vision

Field of stereoscopic vision

(a) Stereoscopic vision

(b) Monocular vision

Figure 1.30  Stereoscopic and monocular visions

36

1.4.1

Chapter 1: Stimuli and Responses

Table 1.3  Differences between stereoscopic and monocular vision Stereoscopic vision

Monocular vision

Both eyes located in front of the head.

Both eyes located at the sides of the head.

A narrow field of vision.

A wide field of vision.

Fields of vision overlap to a great extent. Overlapping fields of vision produce vision in three dimensions.

Fields of vision do not overlap or overlap only slightly.

Three dimensional images formed in the overlapping fields of vision allow the distance, size and depth of objects to be estimated accurately.

Two dimensional images formed in the nonoverlapping fields of vision prevent the distance, size and depth of objects from being estimated accurately.

The ability to estimate distance accurately helps animals to hunt.

A wide field of vision helps animals to detect their enemies coming from any direction.

Humans and most predators have stereoscopic vision.

Most prey have monocular vision.

Stereophonic Hearing What is the importance of having a pair of ears to humans and animals? Stereophonic hearing is hearing using both ears. Stereophonic hearing allows us to determine the direction of the sound accurately. Look at Figure 1.31. The importance of stereophonic hearing to humans is to determine the location of a source of sound. Stereophonic hearing helps predators to determine the location of their prey. Conversely, stereophonic hearing also helps prey to determine the location of their predators and to escape from them.

BRAIN TEASER How does the ear function as a sense of ‘sight’ for the blind?

1.4.1

Source of sound

Figure 1.31  Stereophonic hearing

Based on the above diagram, the ear which is nearer to the source of sound (right ear) receives sound earlier and louder than the other ear.

LIM

The difference in time and loudness of the sound received by both ears is detected by the brain which then allows us to determine the direction of the source of sound which is from the right.

37

Hearing Frequencies of Animals Different animals can hear sounds of different frequencies as shown in Figure 1.32.

I CAN REMEMBER! Frequencies of sounds that can be detected by the human ear are limited to the range of 20 Hz to 20 000 Hz.

Sea lion 450 – 50 000 Hz

Rat 200 – 80 000 Hz

Dolphin 40 – 100 000 Hz

Frequencies of hearing range

Bat 2 000 – 110 000 Hz

Elephant 16 – 12 000 Hz

Dog 67 – 45 000 Hz

Figure 1.32  Frequencies of hearing range of different animals

Activity 1.11 Instructions 1. Work collaboratively in groups. 2. Each group will be assigned by your teacher to create a multimedia presentation such as MS PowerPoint or animation on one of the following topics: (a) Stereoscopic and monocular visions in animals (b) Stereophonic hearing (c) Different hearing frequencies for different animals

38

• CPS, ISS, ICS • Technologybased activity

1.4.1

Chapter 1: Stimuli and Responses

Sensory Organs Ensure the Survival of Animals on Earth

MARVELS OF

SCIENCE

Responses to stimuli ensure the survival of animals on Earth. The sensory organs and responses of several animals are shown in Photograph 1.23. Carry out Activity 1.12 to investigate the sensory organs and responses of several other animals.

Animals such as ants, snakes, frogs and birds are believed to be able to predict earthquakes. Scientists are investigating the types of stimuli detected by these animals before earthquakes occur.

Sensory organ:

Response:

Lateral line

Secretion of pheromone

Lateral line

Response:

Websites Electric field of an electric eel http://links.andl17.com/BT_ Science_39

Producing electric field

Photograph 1.23 Sensory organs and responses of animals

Activity 1.12 To explain the sensory organs and responses of other animals on Earth

• ICS • Discussion activity

Instructions 1. Work in groups. 2. Each group is required to gather information on how responses of animals in Photograph 1.23 are able to ensure their survival on Earth. 3. Discuss the information gathered. 4. Present the outcome of the discussion of each group in class using multimedia presentation.

Formative Practice 1.4

1. 2. 3. 4. 5.

State two types of vision of animals. State the factor that determines the type of vision of animals. What is the type of vision of a primary consumer? Give your reasons. What is the importance of stereophonic hearing? In the dark, Azman can determine the location of a mewing cat. Explain how Azman is able to determine the location of the cat.

1.4.2

39

40

Summary Stimuli and responses in

Humans

Plants

Other animals

are controlled by

such as

such as

Human nervous system

Sensory organs

Tropism

consists of

such as

that includes

– Central nervous system – Peripheral nervous system

Eye, ear, nose, skin, tongue

Phototropism, geotropism, hydrotropism, thigmotropism

sensitive to stimuli such as

responses to

through

Voluntary action, involuntary action

Light, sound, smell, touch, taste through

Mechanism of hearing and mechanism of sight

Light, gravity, water, touch

Sensitivity to stimuli related to

Number of receptors

Combination of sensory organs

Nastic movement

Stereoscopic vision

Monocular vision

Stereophonic hearing

in

in

which

Predators

Prey

Uses both ears to hear

Sounds with different frequency ranges for different animals

Chapter 1: Stimuli and Responses

Self-reflection After studying this chapter, you are able to: 1.1

Human Nervous System Describe the structures and functions of human nervous system through drawings. Make a sequence to show the pathway of impulses in voluntary and involuntary actions. Justify the importance of human nervous system in life.

1.2 Stimuli and Responses in Human Draw the structures of sensory organs and explain their functions and sensitivities towards stimuli. Explain the mechanism of hearing and sight through drawing. Relate human sensory organs to the sensitivity towards various combination of stimuli. Explain through examples how the limitation of senses, defect in sensory organs and ageing affect human hearing and sight. Justify how innovations and technologies can improve the ability to sense in sensory organs. 1.3

Stimuli and Responses in Plants Describe the parts of a plant that are sensitive towards stimuli. Justify how responses in plants ensure their sustainability and survival. Carry out experiments to study responses in plants towards various stimuli.

1.4 Importance of Responses to Stimuli in Animals Explain with examples the types of sight and hearing in animals. Communicate how sensory organs ensure the survival of animals on Earth.

Summative Practice

1

Answer the following questions: 1. Mark ‘•’ the correct statement and ‘×’ the incorrect statement about the human nervous system. (a) The peripheral nervous system is made up of nerves connecting the brain with the spinal cord. (b) Without a functioning brain, voluntary actions cannot be carried out. (c) Playing badminton is an involuntary action. (d) Impulses can only be interpreted by the brain. 41

2. Figure 1 shows structures P, Q and R of the human nervous system.

P:

Q:

R:



Figure 1

Label P, Q and R in Figure 1. 3. Figure 2 shows responses A and B of the eye.



Response A

Response B Figure 2

(a) State the responses shown in Figure 2. (b) State the stimuli that cause these responses. (c) How do the stimuli cause these responses? (d) These responses protect the eye especially the retina by preventing light of excessive intensity from entering the eye. During the solar eclipse, explain why we should observe this event on the water surface in a basin of water. 4. In a science class, Azura studies the mechanisms of hearing and sight. (a) Draw one flow chart that shows the pathway of sound from a source of sound entering the ear. (b) Draw one flow chart that shows the pathway of light from an object entering the eye.

42

Chapter 1: Stimuli and Responses

5. Figure 3 shows the structure of the human skin. Y:

X:

Figure 3

(a) Label X and Y in Figure 3. (b) Explain why the fingertip and not the palm of the hand is used to detect Braille symbols. (c) Mazlan classifies the tongue as skin that possesses taste receptors. Do you agree with the classification of the tongue as skin? Explain your answer. 6. (a) What is the importance of the sense of smell when we are in the science laboratory? Give one example. (b) Why are dogs in police units trained to detect the presence of drugs kept in bags? 7. (a) State two responses in plants that help photosynthesis. (b) How do the two responses of plants in question 7 (a) help photosynthesis? 8. (a) Name the type of vision of an eagle. (b) What is the importance of the type of vision in question 8 (a) to the survival of the eagle?

Focus on HOTS 9. Pak Dollah who is long-sighted forgot to bring his glasses during breakfast in a restaurant. You are required to invent a lens to enable Pak Dollah to read the newspaper. Your invention must make use of the materials shown in Figure 4.

Transparent plastic bottle

Water Figure 4

43

Chapter Chapter

12 2

Respiration

What are the parts of the human respiratory system? What are respiratory diseases? What are examples of substances that are harmful to the respiratory system?

Let’s study Human respiratory system Movement and exchange of gases in human body Health of human respiratory system Adaptations in respiratory systems Gaseous exchange in plants 44

Science Gallery

(a) Running at high altitude

(b) Running in a hypoxic training room

How can the above two locations increase the efficiency of an athlete’s respiration? The higher the altitude, the lower the concentration of oxygen in the air. Therefore, less oxygen is transported to the cells in the body. Shortage of oxygen in these cells will stimulate the body to respond by: • releasing red blood cells stored in the spleen • increasing the production rate of red blood cells • facilitating the decomposition of oxyhaemoglobin to release oxygen All these responses will increase the efficiency of respiration. What is the importance of this adaptation in human survival?

Keywords Intercostal muscles Trachea Bronchus Bronchiole Alveolus Diaphragm Oxyhaemoglobin Diffusion

Cell respiration Emphysema Lung cancer Bronchitis Asthma Stoma Osmosis Guard cell

45

2.1

Human Respiratory System

Human Respiratory System What are the functions of the human respiratory system?

Breathing is the process of inhaling and exhaling air by the lungs. The system in the body that helps us to breathe is known as the human respiratory system. The structure of the human respiratory system is shown in Figure 2.1.

AIN

Nasal cavity

I CAN REMEMBER!

Nostrils Larynx Pharynx

The human respiratory system functions to supply oxygen and removes carbon dioxide from the body cells.

Bronchus Intercostal muscles

Epiglottis

Bronchiole

Trachea

Right lung

Diaphragm Left lung

Alveolus

Figure 2.1  Human respiratory system

46

2.1.1

Chapter 2: Respiration

Activity 2.1 To explain the structure of the human respiratory system Instructions 1. Work in groups. 2. Search the Internet for the structures of the human respiratory system. 3. Create a multimedia presentation from the results of your search.

• ICS, ISS, CPS • Technologybased activity

Breathing Mechanism Inhale and exhale. Can you feel the air entering and leaving through your nose? Place your hand on your chest. Do you realise that your chest rises and falls during breathing? The direction of air from the nose to the lungs is as shown in Figure 2.2. Nostrils

Nasal cavity

Trachea

Bronchus

Pharynx

Larynx

Alveolus

Bronchiole

Figure 2.2  Direction of air in breathing mechanism

SCIENCE INFO

2.1.1

Inhalation and exhalation

E

N CA

G

S

Most people take breathing for granted to the extent of not realising that they are breathing right now! Are you breathing? In this active world, the correct technique of breathing plays an important role to ensure the physical and mental health of humans. Correct breathing technique will improve the performance during exercise or sports events such as weightlifting.

          PA

47

Inhalation Pathway of air Trachea

Lung

Air is breathed in Rib cage moves upwards and outwards

Intercostal muscles

Volume of the thoracic cavity increases

Rib cage

Diaphragm contracts and moves downwards

Diaphragm (a) Front view

(b) Side view

Figure 2.3  Inhalation

When you inhale,

• intercostal muscles contract and pull the rib cage upwards and outwards as shown in Figure 2.3. • diaphragm muscles contract and pull the diaphragm to descend and become flat. • movements of the rib cage and diaphragm make the thoracic cavity bigger and cause air pressure in the thoracic cavity to decrease. • the higher air pressure outside forces air to enter the lungs as shown in Figure 2.3 (b).

SCIENCE INFO The action of epiglottis during swallowing of bolus and breathing During swallowing of bolus

During breathing

Bolus

Epiglottis drops down

Trachea is opened Esophagus

Epiglottis moves up

Bolus

Epiglottis is upright

Trachea is closed

Trachea is opened

Epiglottis drops down and closes the trachea when a bolus is swallowed into the esophagus.

48

Epiglottis moves up Trachea is opened

Esophagus

Epiglottis moves up causing the trachea to open.

2.1.1

Chapter 2: Respiration

Exhalation

Pathway of air

Lung

Trachea

Air is breathed out Rib cage moves downwards and inwards Volume of the thoracic cavity decreases

Rib cage

Diaphragm (a) Front view

Diaphragm relaxes and curves upwards (b) Side view

Figure 2.4  Exhalation

When you exhale, • intercostal muscles relax and the rib cage moves downwards and inwards as shown in Figure 2.4. • diaphragm muscles relax and curve upwards. • movements of the rib cage and diaphragm make the thoracic cavity smaller and cause the air pressure in the thoracic cavity to increase. • the higher air pressure in the lungs pushes the air out as shown in Figure 2.4 (b).

Activity 2.2 To create a model or simulation to describe the breathing mechanism

• ICS, ISS • Innovationbased activity

Instructions 1. Work in groups. 2. Create a model or multimedia simulation to describe the actions of the diaphragm, intercostal muscles, movement of the rib cage, changes in the volume and air pressure in the thoracic cavity during inhalation and exhalation. 3. Present the breathing mechanism based on the model or simulation created.

2.1.1

49

Experiment 2.1 A Percentage of oxygen in inhaled and exhaled air

Aim To study the difference in the percentage of oxygen in inhaled and exhaled air Problem statement What is the difference in the percentage of oxygen in inhaled and exhaled air? Hypothesis The percentage of oxygen in inhaled air is higher than the percentage of oxygen in exhaled air. Variables (a) manipulated variable : Type of air in gas jar (b) responding variable : Final water level in gas jar (c) constant variables : Air temperature and air pressure, volume of gas jar

Safety Precaution Gas jar filled with exhaled air should be covered with a gas jar cover while being transferred to be inverted over a candle.

Materials Candle, plasticine, matches, permanent marker, water, inhaled air and exhaled air Apparatus Glass basin, gas jar, gas jar cover and gas jar stand Procedure 1. Set up the apparatus as shown in Figure 2.5 (a) and (b). Gas jar

Gas jar

Candle

Water level mark

Glass basin Water Plasticine

Gas jar stand (a)



Volume of gas jar is divided into five equal parts and marked using the permanent marker

Water level mark

(b)

Figure 2.5

2. Light a candle and invert the gas jar filled with air over the candle as shown in Figure 2.6. 3. Observe and record the final water level (in units of the number of equal parts marked on the gas jar) after the candle flame extinguishes. Estimate the percentage of oxygen in the air in the gas jar.

50

Candle

Figure 2.6 2.1.2

Experiment Chapter 2: Respiration

4. Set up the apparatus as shown in Figure 2.7 to collect exhaled air until the water level mark. 5. Repeat steps 2 and 3. Gas jar Exhaled air

Collected exhaled air Water level mark Candle Glass basin Plasticine Water

Gas jar stand

Figure 2.7 Results Type of air in gas jar

Final water level in gas jar (number of parts)

Percentage of oxygen in the air

Inhaled air Exhaled air Conclusion Is the hypothesis of this experiment accepted? What is the conclusion of this experiment? Question In which gas jar does the water level rise higher? Explain your observation.

B Concentration of carbon dioxide in inhaled and exhaled air

Aim To study the difference in concentration of carbon dioxide in inhaled and exhaled air Problem statement What is the difference in concentration of carbon dioxide in inhaled and exhaled air? Hypothesis Concentration of carbon dioxide in exhaled air is higher than concentration of carbon dioxide in inhaled air. Variables (a) manipulated variable : Type of air passed through limewater (b) responding variable : Condition of limewater (c) constant variables : Concentration of limewater, volume of conical flask Materials Limewater, inhaled air and exhaled air Apparatus Conical flask, connecting tube, rubber tubing, glass tube and rubber stopper 2.1.2

51

Procedure 1. Set up the apparatus as shown in Figure 2.8. 2. Close clip A. Inhale and hold your breath. Then, close clip B and open clip A. After that, exhale.

Clip A

Clip B Air breathed in

Air breathed out

Limewater



Figure 2.8 3. Observe and record if the limewater in the conical flasks where inhaled and exhaled air passes through appears clear or cloudy. Results Type of air that passes through limewater

Condition of limewater

Inhaled air Exhaled air Conclusion Is the hypothesis of the experiment accepted? What is the conclusion of this experiment? Question In which conical flask does the limewater become cloudy? Explain your observation.

In theory, Percentage/Concentration

Inhaled air

Exhaled air

Oxygen

Higher

Lower

Carbon dioxide

Lower

Higher

Do the results of Experiment 2.1 support this theory? Explain your answer. 52

2.1.2

Chapter 2: Respiration

Formative Practice

2.1

1. Complete the flow chart below which describes the direction of air during inhalation. Nostrils (a)

Nasal cavity

Pharynx

(b)

Larynx Alveolus

(c)

2. Mark ‘•’ for the correct statements and ‘×’ for the incorrect statements on breathing. (a) Epiglottis is the structure that opens or closes the trachea. (b) Exchange of gases in the body cells occurs in the bronchioles. (c) The diaphragm moves downwards and flattens during exhalation. (d) The percentage of carbon dioxide in exhaled air is less than inhaled air. 3. What is the importance of good ventilation in a class with many students? 4. Figure 1 shows a simple model used to show the breathing mechanism.

Y-shaped glass tube

Glass jar

Balloon



Thin rubber sheet

Figure 1

(a) Name the parts of the human respiratory system represented by the following parts: (i) Glass jar (ii) Thin rubber sheet (iii) Y-shaped glass tube (iv) Balloon (b) Why is a thin rubber sheet used in the above model instead of a thick rubber sheet? (c) Name the breathing processes shown by the following actions performed on the thin rubber sheet: (i) Pulling the thin rubber sheet downwards. (ii) Pushing the thin rubber sheet upwards. (d) Why does the glass jar fail to function as a rib cage in the breathing mechanism using the above model? 53

Movement and Exchange of Gases in the Human Body

2.2

Movement and Exchange of Oxygen and Carbon Dioxide in the Human Body Have you ever wondered about the process of movement of particles such as oxygen and carbon dioxide molecules from an area of higher concentration to an area of lower concentration? What is this process? Observe the movement and exchange of oxygen and carbon dioxide in the alveolus and blood capillaries as shown in Figure 2.9.

Blood with lower concentration of oxygen and higher concentration of carbon dioxide

Inhaled air

Exhaled air

Alveolus

Blood capillary wall

3

Blood capillary

Blood with higher concentration of oxygen and lower concentration of carbon dioxide

Oxygen 1

Red blood cell

Carbon dioxide

KEY: Oxygen (O2) Carbon dioxide (CO2)

2 Blood capillary Red blood cell

6

4 O2 5

CO2 Body cell

Figure 2.9  Movement and exchange of oxygen and carbon dioxide in the human body

54

2.2.1

Chapter 2: Respiration

Activity 2.3 To create a presentation to show the movement and exchange of gases in the human body

• ISS • Innovationbased activity

Instructions 1. Work in groups. 2. Each group needs to create a presentation showing the following: • Exchange of oxygen and carbon dioxide due to the difference in concentration in the alveolus and blood capillaries • Process of diffusion of oxygen from the alveolus into the blood capillaries • Formation of an unstable compound, that is oxyhaemoglobin • Release of oxygen into the body cells • Process of oxidation of food, that is, cellular respiration to produce energy • Diffusion of carbon dioxide from the body cells into the blood capillaries and then into the alveolus

1

The air inhaled into the alveolus has a higher concentration of oxygen compared to the concentration of oxygen in the blood. Therefore, oxygen will diffuse through the wall of the alveolus into the walls of the capillaries and into the blood.

2

In red blood cells, there is a dark red-coloured compound known as haemoglobin. Haemoglobin will combine with oxygen to form oxyhaemoglobin which is an unstable compound and bright red in colour. Haemoglobin + oxygen

4

When the blood reaches the area around the body cells that has a low concentration of oxygen, the oxyhaemoglobin being an unstable compound will decompose to release oxygen molecules and change back into haemoglobin.

oxyhaemoglobin

3

Blood with oxyhaemoglobin is transported from the lungs to the heart and pumped to the other parts of the body.

Oxyhaemoglobin → haemoglobin + oxygen

5

In the body cells, the diffused oxygen oxidises glucose molecules into carbon dioxide, water and energy through the process of cellular respiration as summarised in the following chemical equation. Glucose + oxygen → carbon dioxide + water + energy

2.2.1

6

Carbon dioxide released by the cells diffuses into the blood capillaries and is transported to the alveolus to be removed during exhalation.

55

Importance of the Adaptations of the Alveolar Structure The adaptations of the alveolar structure increase the efficiency and maximise the exchange of gases in the human body. Among the adaptations of the alveolar structure are as shown in Figure 2.10. Thickness of the walls of alveolus and blood capillaries

Moist wall of alveolus

The moist wall of alveolus allows respiratory gases to dissolve and diffuse into the blood The alveolus and blood capillaries have thin capillaries. walls which are made up of only one layer of cells. This structure facilitates and increases the rate of diffusion of gases across the walls of the alveolus and blood capillaries. Adaptations of the alveolar structure Network of capillaries covering the alveolus

Surface area of alveolus The lungs contain millions of alveoli which provide a large surface area for the exchange of gases.

The alveolus is covered by a compact network of capillaries which increases the rate of gaseous exchange between the alveolus and the blood capillaries.

Figure 2.10  Adaptations of the alveolar structure to increase efficiency in the exchange of gases

SCIENCE INFO Other than the alveolar structure, another factor that can increase the exchange of gases in the human body is the difference in concentration of gases in the alveoli and blood capillaries. The greater the difference in concentration of a gas in the alveoli and blood capillaries, the higher the rate of diffusion of the gas between the alveoli and the blood capillaries.

Formative Practice

2.2

1. What factor determines the rate of exchange of oxygen between the alveolus and blood capillaries? 2. Describe the conditions in the following processes: (a) Haemoglobin changes into oxyhaemoglobin (b) Oxyhaemoglobin decomposes into haemoglobin 3. Write a chemical equation to describe cellular respiration 4. What happens to the efficiency of the exchange of oxygen in the human body at a high altitude? Explain your answer 5. State four adaptations that influence the efficiency of the alveolus to maximise the exchange of gases in the body 56

2.2.2

Chapter 2: Respiration

2.3

Health of Human Respiratory System

Substances that are Harmful to the Human Respiratory System

What is the importance of forest reserves to the health of the respiratory system?

The air that we inhale during breathing may contain substances that can be harmful to the respiratory system. Examples of such substances are as follow: • • • • •

Cigarette tar Carbon monoxide Sulphur dioxide Nitrogen dioxide Haze, dust and pollen

AIN

LIM

Forest reserves can reduce the substances that can be harmful to the respiratory system.

BRAIN TEASER Why are forests commonly known as ‘green lungs’?

Cigarette Tar

SCIENCE INFO Cigarette tar and tar used in making roads are different substances. Cigarette tar is normally labelled as ‘tar’ which is the acronym for ‘total aerosol residue’.

Cigarette tar is one of the toxic substances found in cigarette smoke. Cigarette tar in inhaled air sticks to and kills cells in the air passage such as the thorax, pharynx, epiglottis, larynx, bronchi, bronchioles and alveoli. Cigarette tar also increases the production of mucus and phlegm in the lungs. Why do smokers often cough or have flu? Based on the data of lung cancer patients, most of them are smokers. Cigarette tar is an example of a substance in cigarette smoke that can cause lung cancer.

BATTERY

Cadmium Alkaline battery

Stearic acid Candle

Toluene Industrial solvent

Nicotine Insecticide

Butane Lighter fuel Carbon monoxide Smoke from motor vehicle exhaust

FLOOR CLEANER

Ammonia Floor cleaner

Acetone Paint

Methane Sewage fumes

Arsenic Rat poison

Cyanide Poison

Methanol Fuel

Figure 2.11  Harmful substances found in cigarette smoke 2.3.1

57

Carbon Monoxide Carbon monoxide is usually found in cigarette smoke and exhaust gases of motor vehicles. Carbon monoxide is a colourless and odourless gas. When carbon monoxide diffuses from the alveoli into the blood capillaries, it will combine chemically with haemoglobin to form carboxyhaemoglobin which is a stable compound. Carbon monoxide + haemoglobin ⎯→ carboxyhaemoglobin This causes a shortage of oxyhaemoglobin in blood that transports oxygen to the body cells. Due to this shortage, the body cells are unable to produce the required amount of energy through cellular respiration. Can body cells live without energy? Sulphur Dioxide Sulphur dioxide that is released into the air is normally produced by the combustion of coal from power stations as shown in Photograph 2.1. Sulphur dioxide is a colourless gas with a pungent smell. It irritates the air passage causing cough, difficulty in breathing, bronchitis and lung cancer.

BRAIN TEASER Why should we support ‘SAY NO TO SMOKING’ campaigns?

My World of Science The number 220 displayed on this food label is the code for a substance, that is sulphur dioxide, used to preserve food.

Photograph 2.1  Smoke released from a power station

58

2.3.1

Chapter 2: Respiration

Nitrogen Dioxide Nitrogen dioxide that is released into the air is normally produced by the combustion of fuels such as petrol and diesel in motor vehicles as shown in Photograph 2.2. Nitrogen dioxide is a brown-coloured gas with a pungent smell. This gas irritates the air passage and causes cough, difficulty in breathing and asthma.

BRAIN TEASER How does the use of electric buses conserve the human respiratory system?

SCIENCE INFO On 23 June 2013, the Air Pollutant Index (API) in Muar, Johor rose up to 746 at 7.00 a.m. far above the minimum hazardous level of 300. This situation caused the government to declare a state of emergency in Muar and Ledang (which was subsequently withdrawn on the morning of 25 June 2013).

Photograph 2.2  Motor vehicles

Haze, Dust and Pollen Haze, dust and pollen are solid particles which are fine, light and suspended in the air. The smoke from motor vehicle exhaust, open burning and forest fires produces haze and dust (Photograph 2.3). Pollen released from anthers into the air is carried by the wind over long distances in all directions. Haze, dust and pollen irritate the respiratory system and cause respiratory diseases such as asthma.

My Malaysia Health Education Division, Ministry of Health Malaysia http://links.andl17.com/BT_Science _59

Photograph 2.3  Condition of the surroundings during haze 2.3.1

59

Respiratory Diseases and their Symptoms Symptoms and ways to treat asthma N CA

G

E

Asthma is triggered by the presence of dust, pollen, haze, smoke from cigarette and motor vehicle exhaust, open burning and forest fires. Symptoms of asthma include shortness of breath, wheezing and coughing.

S

Asthma

Bronchitis

Bronchitis is an inflammation of the bronchus caused by tar and irritants in cigarette smoke. Symptoms of bronchitis include shortness of breath, persistent coughing and insomnia. Emphysema Emphysema is the condition of the alveoli in the lungs which are damaged by harmful substances in the air such as irritants in cigarette smoke. Symptoms of emphysema include shortness of breath, pain when breathing and feeling tired from doing even a light task. Emphysema patients cannot be cured but the symptoms of this disease can be controlled (Photograph 2.4).

(a) Healthy alveoli

          PA

Websites • Is this flu, bronchitis or inflammation of the lungs? http://links.andl17.com/BT_ Science_60_2

Photograph 2.4  Emphysema patients need oxygen supply even while at rest

• Emphysema, symptoms and ways to treat it http://links.andl17.com/BT_ Science_60_3

(b) Damaged alveoli due to emphysema

Figure 2.12  Difference between healthy alveoli and damaged alveoli

60

2.3.1

Chapter 2: Respiration

Lung Cancer Lung cancer is caused by cancer causing chemical substances known as carcinogens. These chemical substances are inhaled during breathing. Cigarette smoke contains various carcinogens, for example tar that causes lung cancer. Symptoms of lung cancer include persistent coughing, blood in the phlegm and feeling pain when breathing. Observe the difference between healthy lungs and the lungs of a cancer patient shown in Photograph 2.5.

Today in history World Cancer Day is celebrated on 4 February every year since 2000.

My Malaysia National Cancer Institute Screening test for lung cancer is provided free of charge to Malaysians between the ages of 50 and 70. http://links.andl17.com/BT_Science _61

(a)  Lungs of a healthy person

(b) Lungs of a cancer patient

Photograph 2.5  Difference between healthy and cancerous lungs

Activity 2.4 To gather and analyse data on respiratory diseases

• ICS

Instructions • Discussion activity 1. Work in groups. 2. Gather and analyse information based on data obtained from the Ministry of Health Malaysia or from other countries on respiratory diseases such as asthma, bronchitis, emphysema and lung cancer.



http://links.andl17. com/BT_Science _61_2

http://links.andl17. com/BT_Science _61_3

3. Discuss the analysed information. 4. Present the outcome of your group's discussion in class in the form of multimedia presentation. 2.3.1

61

yonkinog Sasm to

Effects of Smoking on the Lungs Smoking is not only harmful to the respiratory system of smokers but also to the respiratory system of other people in the vicinity of the smokers. A person who does not smoke but inhales cigarette smoke is known as a passive smoker. The harmful effects of cigarette smoke to the human respiratory system do not only happen in the body of the smoker but also in the body of the passive smoker.

!

CIGARETTE IS HARMFUL

REGARDLESS OF WHAT TYPE IT IS... Are you keen to stop smoking?  

FLOW CHART CLINIC TO STOP SMOKING Reference/Walk in

Registration

Have you ever tried to stop  smoking before  this? 

Examination/ Screening Modification of behaviour (consultation)

Pharmacology treatment (if necessary)

Appointment for 6 months (minimum 6 sessions)

We are ready to help you. Register at the stop smoking clinic in Shah Alam Hospital        now!    

Assessment on the status of stop smoking Contact: Health Education Unit Shah Alam Hospital Tel.: 03-55263000 ext.: 1208/1209

Photograph 2.6  Signboards at the hospital related to smoking

Experiment 2.2 (Demonstration by teacher) Safety Precautions

Aim To study the effects of smoking on the lungs Problem statement What are the effects of smoking on the lungs? Hypothesis Cigarette smoke contains cigarette tar (brown-coloured substance) and acidic gases that damage the lungs. Variables (a) manipulated : Presence of cigarette variable smoke (b) responding : Colour of cotton wool variables and litmus solution at the end of the experiment (c) constant : Rate of suction variable of air using the filter pump Materials Cigarette, cotton wool, litmus solution and matches or lighter

Rubber tube

Clamp of retort stand U-tube Cotton wool Wooden block

• Carry out this experiment in a fume chamber. • Avoid inhaling cigarette smoke. • U-tube and conical flask are fragile. Be careful when handling these apparatus.

Glass tube

To filter pump Conical flask Litmus solution

Figure 2.13 (a) Apparatus U-tube, conical flask, rubber stopper, filter pump, rubber tube, glass tube, retort stand with clamps and wooden block

62

2.3.2

Experiment Chapter 2: Respiration

Procedure 1. Set up the apparatus as shown in Lighted cigarette Figure 2.13 (a). Rubber tube Glass tube 2. Observe and record the colour of the cotton wool and litmus solution. 3. Switch on the filter pump for 10 minutes. Clamp of 4. Switch off the filter pump. retort stand 5. Observe and record the change in U-tube colour of the cotton wool (if any) Cotton and litmus solution in a table. wool 6. Repeat steps 1 to 5 with a Wooden block lighted cigarette as shown in Figure 2.13 (b). Figure 2.13 (b) Observation Presence of cigarette smoke

Colour of cotton wool beginning of experiment

end of experiment

To filter pump Conical flask Litmus solution

Colour of litmus solution beginning of experiment

end of experiment

No Yes Conclusion Is the hypothesis of the experiment accepted? What is the conclusion of this experiment? Questions 1. Name the substance in cigarette smoke that is deposited on the cotton wool. 2. Is cigarette smoke acidic or alkaline? Explain your answer. 3. Name three other harmful substances found in cigarette smoke.

Formative Practice

2.3

1. (a) Name four examples of solids in the air that are harmful to the human respiratory system. (b) Name three examples of gases in the air that are harmful to the human respiratory system. 2. Name one substance released by plants that is harmful to the human respiratory system. 3. State one symptom of each of the following respiratory diseases: (a) Emphysema (c) Bronchitis (b) Lung cancer (d) Asthma 4. Name two types of respiratory diseases that are caused by harmful substances in cigarette smoke. 5. What is meant by passive smoker? 2.3.2

63

2.4

Adaptations in Respiratory Systems

How the Respiratory System Adapts in Different Surroundings The respiratory structures of most organisms including humans have three features to ensure an efficient gaseous exchange with the surroundings. These three features are as follows:

Moist surface of respiratory structures such as the moist surface of alveoli.

Thin respiratory structures such as the walls of alveolus and blood capillaries which are one cell thick.

Large surface area of respiratory structures such as the surface area of millions of alveoli.

Different organisms have different respiratory systems and adapt to maximise the rate of gaseous exchange in different surroundings. The respiratory structures which adapt in different surroundings include moist outer skin, gills and trachea. Moist Outer Skin Amphibians such as frogs are organisms which can live on land and in water. The respiratory structure of frogs can adapt to increase the efficiency of gaseous exchange while they are on land (Figure 2.14). Name one respiratory structure of frogs which can adapt for gaseous exchange while they are on land. Other than lungs, frogs usually use their moist outer skin for gaseous Moist outer exchange. The skin of frogs is thin skin Glottis and very permeable to gas. The skin of frogs is also always moist because it is covered by a layer of mucus Lungs which causes the respiratory gases to Nostril dissolve and diffuse easily. Under the layers of skin is a dense network of blood capillaries to Oral increase the diffusion rate cavity of gases between the skin and the blood capillaries.

Figure 2.14  Respiratory system of a frog

64

2.4.1

Chapter 2: Respiration

Gills Fish is an organism that can only live in water. Therefore, the respiratory structure of fish, namely gills can adapt to increase the efficiency of gaseous exchange in water. Gills are made up of two rows of fine filaments that have many thin and flat projections known as lamellae as shown in Figure 2.15. The number of filaments and lamellae produces a large surface area to facilitate gaseous exchange. Since fish live in water, their gills are surrounded by water and this causes the respiratory gases to dissolve and diffuse easily.

SCIENCE INFO

Mudskippers are classified as amphibious fish because they breathe through their gills like fish and also through their moist outer skin like amphibians.

Network of blood capillaries

Flow of water

Deoxygenated blood

Blood vessel Flow of water Lamella Oxygenated blood

Filament

Flow of blood

Figure 2.15  Structure of gills in fish

Trachea

Trachea

The respiratory system of insects Oxygen Air sacs is the trachea system made up Trachea of air tubes known as trachea Spiracle as shown in Figure 2.16. Air enters or leaves the trachea Tracheole Carbon through breathing pores known dioxide as spiracles. The opening and Muscles Spiracles closing of spiracles are controlled by valves which allow air to leave Figure 2.16  Trachea system of grasshopper and enter the body. Trachea is divided into fine branches known as tracheoles. Tracheoles have thin and moist walls to increase the efficiency of gaseous exchange. The large number of tracheoles also provides a large surface area to facilitate gaseous exchange through diffusion directly into the cells. Some insects such as grasshoppers have air sacs in their trachea system. These sacs are filled with air to increase the rate of exchange of respiratory gases between tissues and the surroundings during energetic activities. 2.4.1

65

Activity 2.5 To create a presentation showing how respiratory system adapts in different surroundings

• ISS • Inovationbased activity

Instructions 1. Work in groups. 2. Each group is required to create a presentation explaining how other organisms carry out respiration through respiratory systems that can adapt in different surroundings through: (a) moist outer skin (b) gills (c) trachea

Activity 2.6 Active reading on the adaptation and ability of the human respiratory system Instructions Active reading Carry out active reading on strategy adaptation and ability of the http://links. human respiratory system in andl17.com/ the following contexts: BT_Science_66_5 (a) Different altitudes (at the bottom of the sea and in mountainous regions). Flashback: Refer to Science Gallery on page 45 (b) Sports activities and lifestyles (athlete and swimmer). Refer Info 1. (c) Sickle cell anaemia. Refer Info 2.

Formative Practice

• CPS

Info 1 The adaptation and ability of the human respiratory system during exercise http://links.andl17. com/BT_Science_66_3 Info 2 Sickle cell anaemia http://links. andl17.com/BT_ Science_66_4

2.4

1. Name the respiratory structure in the following animals: (a) Fish (b) Insects

(c) Amphibians

2. State two adaptations in the outer skin of frogs that facilitate quick and efficient gaseous exchange between the outer skin and the surroundings. 3. Why is the circulatory system of insects not involved in the respiratory mechanism of insects? 4. What is the importance of exercise in maintaining a healthy respiratory system? 5. Choosing a healthy lifestyle is important for respiration. State two examples of healthy lifestyles. 66

2.4.1

Chapter 2: Respiration

2.5

Gaseous Exchange in Plants All living things including plants carry out respiration. During respiration, oxygen is taken in and carbon dioxide is removed.

During the day, besides respiration, plants also carry out photosynthesis by taking in carbon dioxide and giving out oxygen.

SELVI RIFQI

BRAIN TEASER

Mechanism of Gaseous Exchange in Plants Most plants carry out the process of gaseous exchange with their surroundings through their leaves, stems and roots. These three parts provide a large surface area for gaseous exchange. Gaseous exchange in plants is shown in Figure 2.17.

State one function of the aerial roots of mangrove plants as shown in the photograph on the right.

During the day

Taking in carbon dioxide and oxygen

During the night

Giving out oxygen and carbon dioxide

Taking in oxygen

Giving out carbon dioxide

Figure 2.17  Gaseous exchange in plants 2.5.1

67

Diffusion of Carbon Dioxide The structure in leaves that shows the pathway of gaseous exchange is as shown in Figure 2.18. The diffusion of carbon dioxide occurs through the stoma according to the difference in concentration of carbon dioxide in the cells and in the air spaces between the cells during photosynthesis.

1

What is the structure in leaves that allows gases to diffuse either into or out of plant cells to the atmosphere?

When carbon dioxide is used in photosynthesis, the concentration of carbon dioxide in the cells becomes lower compared to the concentration of carbon dioxide in the air space between the cells. This difference in concentrations allows the dissolved carbon dioxide in the moist surface of cells to diffuse from the air space between the cells into the cells.

ADNAN

I CAN REMEMBER! Diffusion is the process of movement of particles from a region of high concentration to a region of low concentration.

Cuticle Upper epidermis

Palisade mesophyll cell

O2

Air space between cells

Xylem Phloem

O CO2 2

Spongy mesophyll cell

Lower epidermis CO2 Guard cell

O2

Stoma

KEY: Carbon dioxide (CO2) Oxygen (O2)

2

This causes the concentration of carbon dioxide in the air space between the cells to become lower compared to the concentration of carbon dioxide in the air outside the stoma. This difference in concentrations causes the diffusion of carbon dioxide from the atmosphere into the air space between the cells through the stoma which is open.

Figure 2.18  Pathway of gaseous exchange in leaves during photosynthesis

68

2.5.1

Chapter 2: Respiration

Stomatal Pore and Guard Cells

Stomatal pore

Stoma is made up of a stomatal pore bounded by a pair of guard cells. Guard cells contain chloroplasts to carry out photosynthesis. Stomata of plants open during photosynthesis when there is light and close when it gets dark or when the plant loses a lot of water on a hot day as shown in Photograph 2.7.

Guard cells

(a) Open stoma

(b) Closed stoma

Photograph 2.7  Open and closed stoma

SCIENCE INFO

Process of Osmosis Affects the Stoma

Stoma – singular Stomata – plural

Concept of Osmosis Osmosis is the process of movement of water molecules from a region of high concentration of water molecules (solution with a low concentration of solutes) to a region of low concentration of water molecules (solution with a high concentration of solutes) through a semipermeable membrane (Figure 2.19). This membrane is permeable to water but not permeable to some solutes such as sucrose molecules. Semipermeable membrane prevents the movement of large solute molecules

Only water molecules are able to pass through the pores of the semipermeable membrane

KEY: Water molecule Solute molecule such as sucrose

Figure 2.19  Osmosis

Process of Osmosis in Guard Cells When there is light, guard cells carry out photosynthesis to produce glucose. The concentration of glucose in guard cells increases and causes water from surrounding cells to diffuse into the guard cells through osmosis. Hence, the guard cells become turgid and curved as shown in Figure 2.20. Conversely, at night or on a hot day, water diffuses out of the guard cells also through osmosis and causes the guard cells to become flaccid and straight. Turgid and curved guard cell

Flaccid and straight guard cell

KEY:

Water diffuses into cell through osmosis Water diffuses out of cell through osmosis

Figure 2.20  Change in shape of guard cells caused by osmosis 2.5.1

69

Effects of Osmosis on Stoma The process shown in Figure 2.20 explains how during the day, water diffuses into the guard cells through osmosis and causes both the guard cells to curve and open the stoma as shown in Figure 2.21. At night or on a hot day, water diffuses out of the guard cells through osmosis and causes both the guard cells to become straight and close the stoma as shown in Figure 2.22. Guard cells

Thin outer wall

Nucleus

Chloroplast

Stomatal pore

Vacuole

Stomatal pore



Nucleus Thin outer wall

Thick inner wall

Figure 2.21  Open stoma

Figure 2.22  Closed stoma

Activity 2.7 To show the mechanism of gaseous exchange in plants

• ICS, ISS

Instructions • Technology 1. Work in groups. based activity 2. Create a multimedia presentation to show the following: • Stomatal pore is controlled by two guard cells • During the day, water diffuses into the guard cells through osmosis and causes both the guard cells to curve and open the stoma • Diffusion of carbon dioxide occurs in the stoma due to the difference in concentration • At night, water diffuses out of the guard cells through osmosis and causes the stoma to close

Importance of Unpolluted Environment for the Survival of Plants The environment, especially unpolluted air, is very important to ensure the growth and survival of plants. Effects of Haze and Dust on the Survival of Plants If the surrounding is hazy and dusty, the polluted air will be harmful to the growth and survival of plants as shown in the article on page 71. Visit the website and study the article published. Other than reducing sunlight from reaching the plants and reducing the rate of photosynthesis, haze and dust that settle on stomata prevent gaseous exchange between plants and their surrounding. What will happen to a plant if its stomata are clogged with dust? 70

2.5.1

2.1.1 2.5.2

Chapter 2: Respiration

http://links.andl17.com/ BT_Science_71_1

Photograph 2.8  Official website of MARDI

Effects of Acidic Gases in the Air on the Survival of Plants Air pollutant gases which are acidic such as sulphur dioxide and nitrogen dioxide dissolve in rainwater to produce acid rain. Acid rain kills plant cells and causes soil to be acidic and less fertile. Most plants cannot live in highly acidic soil. This will reduce agricultural produce and cause food shortage. Among the preventive measures against the effects of pollution on plants in the local and global context are as follows: BRAIN • Ban open burning in Indonesia and Malaysia TEASER • Limit the number of motor vehicles on the road in Why do efforts to prevent air Beijing, China pollution require the cooperation • Encourage the use of alternative energy such as of the global society? solar energy Examples of research and information gathered by scientists on the effects of acid rain and steps taken to prevent air pollution in this region are as follows: Effects of acid rain in Asia http://links.andll17.com/BT_Science_71_3

2.5.2

ASEAN – Haze preventive measures http://links.andl17.com/BT_Science_71_2

71

Activity 2.8 To create a multimedia presentation on the effects of pollution on plants and the preventive measures against pollution in local or global context

• ICS, ISS • Technologybased activity

Instructions 1. Work in groups. 2. Gather and analyse further information on the following: • Effects of pollution on plants • Preventive measures against pollution in the local or global context 3. Discuss the information analysed. 4. Present the findings of each group in the form of multimedia presentation.

Formative Practice

2.5

1. Figure 1 shows mangrove plants.



Figure 1

Name three parts of a mangrove plant where gaseous exchange occurs. 2. Figure 2 shows a structure found in a leaf. P:



Q: Figure 2

Label parts P and Q. 3. (a) Are stomata open or closed during the day? Explain. (b) Are stomata open or closed at night? Explain. (c) Why are stomata closed on hot days? 4. What are the effects of polluted air on the growth and survival of plants? 72

Summary Respiration Human respiratory system Structure consists of

Nostril, nasal cavity, pharynx, epiglottis, larynx, intercostal muscles, trachea, bronchus, bronchiole, alveolus, diaphragm, lungs Breathing mechanism

Movement and gaseous exchange in the human body Exchange of oxygen and carbon dioxide Diffusion of oxygen from alveolus into blood capillaries Formation of oxyhaemoglobin Release of oxygen to body cells

Exhaled air • Less oxygen • More carbon dioxide

Diffusion of carbon dioxide from body cells into capillaries and alveolus

Health harmed by substances such as

Animals

Amphibians

Fish

Insects

Moist outer skin

Gills

Trachea

Cigarette smoke, cigarette tar, dust, haze, pollen, carbon monoxide, sulphur dioxide, nitrogen dioxide cause diseases such as

Asthma, bronchitis, lung cancer, emphysema Thickness Moisture

73

Efficiency of alveolus

Plants

depends

Surface area

on

Network of capillaries

Stoma which

Opens during the day and

Closes at night and on hot days Importance of unpolluted environment to ensure

Growth and survival of plants

Chapter 2: Respiration

Inhaled air • More oxygen • Less carbon dioxide

Cellular respiration produces carbon dioxide and energy

Adaptations in respiratory system

Self-reflection After studying this chapter, you are able to: 2.1 Human Respiratory System Draw and label the internal structures of the human respiratory system and describe the breathing mechanism. Carry out experiments to investigate the differences in the content of gases in inhaled and exhaled air. 2.2 Movement and Exchange of Gases in the Human Body Describe the movement and exchange of oxygen and carbon dioxide in the human body. Justify the importance of adaptations of the alveolar structure to increase efficiency of gaseous exchange in the human body. 2.3 Health of Human Respiratory System Communicate about substances that are harmful to the respiratory system as well as diseases and their symptoms. Carry out an experiment to show the effects of smoking on the lungs. 2.4 Adaptations in Respiratory System Justify how the respiratory system adapts in different situations. 2.5 Gaseous Exchange in Plants Explain the mechanism of gaseous exchange in plants. Communicate to justify the importance of an unpolluted environment for the growth and survival of plants.

Summative Practice

2

Answer the following questions: 1. Complete the following flow chart to show the direction of air that is breathed out from the lungs.

74

Bronchiole

(a)

Larynx

Pharynx

(b)

(c)

Trachea

Nostrils

Chapter 2: Respiration

2. Figure 1 shows the human respiratory system. P: Q: R:

Figure 1

Label P, Q and R in Figure 1 using the following words: Alveolus Bronchiole Bronchus

Trachea

3. Figure 2 shows the breathing mechanism during exhalation.

Rib cage Thoracic cavity Diaphragm



Figure 2

Mark ‘•’ for the correct statements, about the mechanism. (a) Air leaves the lungs when the diaphragm moves upwards. (b) When exhaling, the rib cage moves downwards. (c) Air pressure is lower in the lungs. (d) Volume of thoracic cavity decreases. 4. Underline the correct answers. (a) Percentage of oxygen in inhaled air is (higher/lower) than in exhaled air. (b) Percentage of carbon dioxide in inhaled air is (higher/lower) than in exhaled air.

75

5. (a) What is the function of haemoglobin in the human respiratory system? (b) What is the importance of the characteristic of oxyhaemoglobin as an unstable compound in gaseous exchange in the body? 6. Azura is an asthma patient. (a) Why does the doctor advise Azura to reduce her visits to botanical gardens during Spring? (b) Other than the botanical gardens, state two other locations that should be avoided by Azura. Explain your answer. 7. (a) State four factors that affect the efficiency of the alveolus to maximise gaseous exchange in the human body. (b) State one symptom of each of the following respiratory diseases. What causes the symptom? (i) Asthma Symptom : Cause : (ii) Bronchitis Symptom : Cause : (iii) Emphysema Symptom : Cause : 8. Describe three ways to maintain the health of the respiratory system. 9. Why should waiting areas for public transport such as LRT stations and bus stands be designated as non-smoking areas? 10. (a) Give one similarity in the gaseous exchange between insects and plants. (b) Is the insect respiratory system more or less effective compared to the human respiratory system? (c) Explain your answer in 10 (b). 11. (a) Gas X is harmful to the human respiratory system. Gas X can diffuse into a stationary car with its air conditioning on, windows closed and engine running. Name gas X. (b) Explain the effects of the gas in the situation in 11 (a).

76

Chapter 2: Respiration

Focus on HOTS 12. Changes in the volume of air in the lungs of runners X and Y are as shown in Figures 3 (a) and 3 (b). Volume of air in the lungs of runner X against time

Volume of air in the lungs of runner Y against time 5

4 3 2 1 Walking 0



20

Running

40

60

Figure 3(a)

Walking

80 100 Time (seconds)

Volume of air in the lungs (dm3)



Volume of air in the lungs (dm3)

5

4 3 2 1 0

Walking

20

Walking

Running

40

60

80 100 Time (seconds)

Figure 3(b)

(a) State the maximum volume of air in the lungs of the following runners while walking. (i) Runner X (ii) Runner Y (b) State the maximum volume of air in the lungs of the following runners: (i) Runner X (ii) Runner Y (c) From the graphs in Figures 3 (a) and 3 (b), state the relationship between the types of activity performed and the maximum volume of lungs of each runner. Explain. (d) If one of the runners X or Y is a smoker, which one is the smoker? Explain. (e) How does the increase in the maximum volume of the lungs affect the respiration rate? Explain.

77

Chapter Chapter Chapte hapte pte p er

1 3

Transportation

What is the transport system in organisms? What are the components, constituents and blood groups of humans? What factors affect the rate of transpiration in plants?

Let’s study Transport system in organisms Blood circulatory system Human blood Transport system in plants Blood circulatory system in animals and transport system in plants 78

Science Gallery

In 1966, a science fiction film ‘Fantastic Voyage’ attracted the interest of many viewers including scientists! In this film, a team of medical personnel is put into a submarine which is reduced to microscopic size (size of a red blood cell) for an hour using the technological creation of scientist, Jan Benes. This submarine is then injected into the blood circulatory system in Jan Benes’s body to eliminate a blood clot in his brain using laser. The submarine in Jan Benes’s blood circulatory system needs to travel through the heart, lungs and other parts of the body before reaching the blood clot in his brain. Can the blood clot be eliminated using laser in one hour? Is there a possibility of this film being classified as a science documentary film in the future? Why?

Keywords Heart Artery Vein Capillary Antigen

Antibody Transpiration Guttation Xylem Phloem

79

3.1

Transport System in Organisms

Photograph 3.1 Klang Valley Rail Transit Map

RIFQI

Have you ever used the Klang Valley Rail Transit Map as shown in Photograph 3.1 to plan your trip?

What is the importance of a transit route network in the public transport system?

80

Why is KL Sentral known as the ‘heart’ of the transit route network?

Compare and contrast the public transport system with the transport system in organisms.

AIN

Chapter 3: Transportation

Need for Transport System in Organisms Every cell needs oxygen for cell respiration and nutrients to obtain energy. At the same time, carbon dioxide and other waste products produced by cells need to be eliminated to the external environment. The process of carrying oxygen, nutrients and other useful substances from the external environment into the cells is through diffusion. The process of eliminating waste products from the cells is also through diffusion. What is the system that carries useful substances to all parts of the body of an organism and eliminates waste products from the body? Transport System in Simple Organisms Simple organisms such as unicellular organisms (Photograph 3.2) do not have a specialised transport system. Substances needed by cells such as oxygen and nutrients enter directly into cells via diffusion through the cell membrane. Waste products such as carbon dioxide are also eliminated from cells to the external environment via diffusion through the cell membrane.

Amoeba sp. Euglena E sp.

Transport System in Complex Organisms Complex organisms such as humans, vertebrates and multicellular plants have a specialised transport system as shown in Figure 3.1.

Paramecium sp.

Photograph 3.2 Examples of unicellular organisms Xylem

Heart

Blood vessels

Phloem Xylem Phloem

Stoma Phloem

Xylem

(a) Human

(b) Plant

Figure 3.1 Examples of complex organisms with specialised transport system

The process of exchange of substances needed by cells and waste products between complex organisms and the external environment (via diffusion) occurs slowly and not comprehensively because complex organisms have a large volume. Therefore, complex organisms need to have a specialised transport system. Through this specialised transport system, oxygen and nutrients can be carried to all the body cells in complex organisms and waste products can be eliminated from all the body cells to the external environment. 3.1.1

3.1.2

81

Importance of the Function of Transport System in Organisms The importance of the function and impact of transport system in organisms is as shown in Figure 3.2. Transport system carries substances needed by cells such as oxygen and nutrients that are used to produce energy through cellular respiration. This energy is used for living processes in organisms.

Importance of the function of transport system in organisms

Transport system carries substances needed by plant cells such as mineral salts, water and products of photosynthesis to carry out all living processes in plants.

Transport system eliminates toxic waste products from the cells in organisms to the external environment. Toxic waste products that fail to be eliminated from the cells will poison and kill the organisms.

Figure 3.2 Importance of the function of transport system in organisms

Activity 3.1 To gather and share information on the need, function, importance and impact of transport system in organisms

• ICS • Discussion activity

Instructions 1. Work in groups. 2. Gather and share information on the following: (a) Need for transport system in organisms (b) Function of transport system in organisms (c) Importance of transport system in organisms (d) The impact if transport system cannot function well 3. Discuss the shared information. 4. Present the findings of your group discussion using multimedia presentation such as MS PowerPoint.

Formative Practice

3.1

1. What is the function of the transport system in organisms? 2. State two examples of substances needed by cells and two examples of waste products that are eliminated from cells. 3. What is the importance of the function of transport system in organisms? 4. Explain the impact on organisms if the transport system in the organisms cannot function well. 82

3.1.3

Chapter 3: Transportation

3.2

Blood Circulatory System

Blood Circulatory System in Vertebrates Humans and all vertebrates such as mammals, reptiles, amphibians, birds and fish (complex organisms) have a specialised transport system, that is the blood circulatory system. In the blood circulatory system of all vertebrates, blood flows continuously in blood vessels to all parts of the body in one complete cycle through the heart. However, there are significant differences in the blood circulatory system among mammals, reptiles, amphibians, birds and fish. How many times does the blood flow through the heart of mammals, reptiles, amphibians, birds and fish in one complete cycle to all parts of the body? What is the number of atria and ventricles in the heart of mammals, reptiles, amphibians, birds and fish? Carry out Activity 3.2 to find out the differences.

Activity 3.2 To compare and contrast the blood circulatory system in vertebrates Instructions 1. Carry out active reading to compare and contrast the blood circulatory system in vertebrates such as mammals, reptiles, amphibians, birds and fish as shown in Figures 3.3 and 3.4.

• CPS • Discussion activity

Capillaries in lungs and skin

Capillaries C Capi illaries iin gills

Artery

Ventricle Heart Atrium

Atrium

Atrium V Ventricle Heart

Vein

Ca apilla p aries in the bodyy Capillaries

Capillaries in the body

(a) Fish

(b) Amphibians Figure 3.3

3.2.1

83

C apil illlar l ries iin n th he llu un ngggs Capillaries the lungs

Capillaries C ap piilla llaries ri in i the th he lungs he lun lu un ngs

t m trium Atrium

A Atriu um Atrium

A Atriu um Atrium

Atr rium m Atrium

Ventricle ntricle Ventricle

Ventr Ventricle

Heartt

He eart Heart

Capillaries the body Ca aap pillar p illar ill ries riies in in th hee bo h b od dyy d

Cap C ap piiillllar p lla laarriiies lar es in n th tthe he b h bo odyy Capillaries body

(c) Reptiles

(d)) Mammals Mammals mmals ls aand db bir birds rds Figure 3.4

2. Complete the chart which shows a comparison of the blood circulatory systems of vertebrates such as mammals, reptiles, amphibians, birds and fish. Blood circulatory system of vertebrates

Similarities

Made up of a system that allows blood to continuously flow in blood vessels through the heart which pumps blood to the whole body and back to the heart.

84

Differences

Fish

Amphibians

Reptiles

Mammals and birds

3.2.1

Chapter 3: Transportation

Blood Circulatory System in Humans The human blood circulatory system involves the circulation of blood which is pumped from an organ known as the heart to all parts of the body and specialised blood vessels, namely arteries, capillaries and veins as shown in Figure 3.5.

H Heart

Artery

Vein

5 *(

Figure 3.5 Human blood circulatory system 3.2.1

3.2.2

.

,

:

• Human blood circulatory system • Functions of blood circulatory system

     7(

85

Structure and Functions of the Human Heart

:

The human heart has four chambers, that is two atria and two ventricles as shown in Figures 3.6 and 3.7. 5 *(

Aorta .

,

Pulmonary artery

     7(

Pulmonary veins

Superior vena cava

Left atrium Semilunar valve Bicuspid valve

Right atrium

Semilunar valve

Tricuspid valve

Left ventricle

Inferior vena cava Key: Oxygenated blood Deoxygenated blood

Right ventricle Septum

Figure 3.6 Longitudinal section of the human heart Right atrium has thin muscular wall. Functions: t
Deoxygenated blood from the whole body except the lungs enters the right atrium through the superior and inferior vena cava t
8IFO
UIF
right atrium contracts
deoxygenated blood is forced to flow into the DIBNCFS
CFMPX
JU
OBNFMZ
UIF
right ventricle Tricuspid valve Function: t
"MMPXT
UIF
nPX
PG
CMPPE
JO
POMZ
POF
EJSFDUJPO
GSPN
UIF right atrium to the right ventricle

Right ventricle has thick muscular wall. Function: t
8IFO
UIF
SJHIU
WFOUSJDMF
DPOUSBDUT
EFPYZHFOBUFE
CMPPE
JT
GPSDFE
UP
flow out into the pulmonary artery to be carried to the lungs

86

3.2.2

Chapter 3: Transportation

SCIENCE INFO

Semilunar valves Function: t
4FNJMVOBS
WBMWFT
BU
UIF
pulmonary artery and aorta ensure that blood flows only in one direction and not back into UIF
WFOUSJDMFT

The period of time for blood to make one complete circulation from the heart to all parts of the body including the lungs and back to the heart is approximately 1 minute!

Aorta Semilunar valves Pulmonary artery

Pulmonary vein

Left atrium has thin muscular wall. Functions: t
Oxygenated blood from the lungs enters the left atrium through the pulmonary vein t
8IFO
UIF
MFGU
BUSJVN
DPOUSBDUT
oxygenated blood is forced to nPX
JOUP
UIF
DIBNCFS
CFMPX
JU


namely the left ventricle

Vena cava

Right atrium

Right ventricle

Left atrium

Left ventricle

Bicuspid valve Function: t
"MMPXT
UIF
nPX
PG
CMPPE
JO
POMZ
one direction from the left atrium into the left ventricle

Left ventricle has the thickest muscular wall. Function: t
8IFO
UIF
MFGU
WFOUSJDMF
DPOUSBDUT
PYZHFOBUFE
CMPPE
JT
forced to flow out into the aorta to be carried to all parts of the body except the lungs

Septum is the muscular wall which separates the left side of the heart from the right side of the heart. Function: t
1SFWFOUT
PYZHFOBUFE
CMPPE
from mixing with deoxygenated blood

Figure 3.7 Simple structure of the human heart and circulation of blood through the heart

3.2.2

87

Structure and Functions of Main Blood Vessels There are three human blood vessels, namely arteries, capillaries and veins. Figure 3.8 shows the relationship between the artery, capillary and vein. Observe the direction of the blood circulation through the artery, capillary and vein as shown in the figure. To the heart Lumen

From the heart

Valve

Lumen

Thin wall Thick, muscular and elastic wall

Lumen

Capillary Lumen network Artery

Vein

Figure 3.8 Relationship between the vein, capillary and artery Table 3.1 Structure and functions of the vein, capillary and artery Type of blood vessel Structure

Vein

Capillary

Lumen

One layer of cells

Artery

Lumen

Lumen Valve

• Thin, less muscular and less elastic wall to facilitate blood flow under low blood pressure • Has valves • Large lumen

• Thinnest wall which is one cell thick without any muscle or elastic tissue • No valves • Smallest lumen

• Thick and muscular wall with a lot of elastic tissues to withstand high blood pressure • No valves • Small lumen

Functions

• Transports deoxygenated blood back to the heart from the whole body except the lungs • Pulmonary vein transports oxygenated blood from the lungs to the heart

• Allows the exchange of gases, food and waste products between the blood and body cells via diffusion through the thin wall of the capillary

• Transports oxygenated blood from the heart to the whole body except the lungs • Pulmonary artery transports deoxygenated blood from the heart to the lungs

Circulation of blood

• Slow blood flow under low blood pressure • No pulse

• Slow blood flow under decreasing blood pressure • No pulse

• Rapid blood flow under high blood pressure • Pulse detected

88

3.2.2

Chapter 3: Transportation

‘Double’ Blood Circulatory System Humans and other mammals have a ‘double’ blood circulatory system that is made up of the pulmonary circulatory system and systemic circulatory system. Carry out active reading to compare and contrast the pulmonary circulatory system and systemic circulatory system as shown in Figure 3.9. Pulmonary artery

Pulmonary Circulatory System

Pulmonary vein Lungs

Lungs

Pulmonary artery

Pulmonary vein Heart

Systemic Circulatory System Heart

All parts of the body except the lungs

Artery

Vein

Artery

Vein Heart

All parts of the body except the lungs

Figure 3.9 Pulmonary circulatory system and systemic circulatory system

Activity 3.3 To create a multimedia presentation based on research of a sheep’s heart and, explain its structures and functions

• ICS • Active reading activity

5 *(

.

,

Example: Video on the dissection of a sheep’s heart

:

Instructions 1. Work in groups. 2. Each group is required to create a presentation on the research of the heart of a sheep to explain its structures and functions.

     7(

3.2.2

89

Heartbeat

Have you ever heard the ‘lub dub’ sound produced by a beating heart as shown in Photograph 3.3?

SELVI

Between the ’lub’ and ‘dub’ sounds, which is louder?

Photograph 3.3 Hearing the ‘lub dub’ sound when the heart is beating

Semilunar valves closed

Bicuspid valve open

Tricuspid valve opened

     7(

Bicuspid valves closed

Tricuspid valves closed

DIASTOLE DIAST

,

Figure 3.10 shows the sequence of the opening and vallves lves in the heart during du closing of the valves heartbeats.

5 *(

.

Watch this video to understand the process of diastole and systole

:

How is the ‘lub dub’ sound produced?

Semilunar valves open

SSYSTOLE

The ‘dub’ sound is produced by the closure of the semilunar valves at the aorta and pulmonary artery when relaxation of the ventricles occurs. This condition is known as diastole. The pressure reading of blood flowing into and filling the heart is called the diastolic pressure reading.

The ‘lub’ sound is produced by the closure of the tricuspid and bicuspid valves between the atria and the ventricles when contraction of the ventricles occurs. This condition is known as systole. The pressure reading of blood flowing out of the heart is called the systolic pressure reading.

Figure 3.10 Diastole and systole

90

3.2.3

Chapter 3: Transportation

Measurement of Blood Pressure Blood pressure is usually measured using a sphygmomanometer as shown in Photograph 3.4.

SCIENCE INFO Taking of diastolic and systolic pressure readings from a sphygmomanometer is based on listening to the sounds produced by the blood circulation when diastole and systole occur. Due to this, the use of sphygmomanometer to take readings of diastolic and systolic pressures is usually done by an experienced doctor.

Photograph 3.4 Measuring blood pressure

The systolic pressure reading of a youth is normally 120 mm Hg and the diastolic pressure reading is 75 mm Hg. Hence, this blood pressure reading is normally written as 120/75 mm Hg. Measure and read your blood pressure (systolic and diastolic) using a sphygmomanometer.

BRAIN TEASER Why is the reading of systolic pressure higher than the reading of diastolic pressure?

Pulse Rate Photograph 3.5 shows one of the medical examination activities that is normally carried out by a doctor on a patient. What is the quantity measured as shown in the photograph? Pulse is produced by the contraction and relaxation of the muscular artery wall. Is your pulse rate constant? Give two examples of conditions in your daily life that increase the pulse rate. Let us carry out Experiment 3.1 to study the factors that influence the pulse rate.

Photograph 3.5 Detecting pulse 3.2.3

91

Experiment 3.1 Aim To study the factors that influence the pulse rate Problem statement How does the intensity of a physical activity influence the pulse rate? Hypothesis The more vigorous a physical activity, the higher the pulse rate. Variables (a) manipulated variable : Type of activity (b) responding variable : Pulse rate (c) constant variable : Duration of activity

Type of activity

Number of pulses over a period of 10 seconds

15

5 60

20

55

25

50

30

45

35

40

24 27 30 21 3 18 6 15 12 9

Procedure 1. Rest for 5 minutes. Then, locate your pulse as shown in Figure 3.11. 2. Count and record the number of pulses over a period of 10 seconds in a table. Calculate the pulse rate in number of pulses per minute. 3. Repeat steps 1 and 2 after carrying out each of the following types of activities over a period of 5 minutes: (a) Walking slowly (b) Running

10

Apparatus Watch

Figure 3.11

Pulse rate (number of pulses per minute)

Resting Walking slowly Running Conclusion Is the hypothesis accepted? What is the conclusion of this experiment? Questions 1. How does the type of activity influence the pulse rate? 2. How is the increase in pulse rate while carrying out vigorous activities related to the rate of oxygen intake and release of carbon dioxide?

92

3.2.3

Chapter 3: Transportation

Other Factors that Influence the Pulse Rate Apart from physical activities, other factors which influence the pulse rate are as follows: A Gender The average pulse rate of an adult male is between 70 to 72 beats per minute and the average pulse rate of an adult female is between 78 to 82 beats per minute. The difference in pulse rate between males and females is caused by the difference in the size of the heart. The heart of females which is normally of smaller size pumps less blood for each heartbeat and needs to beat at a much higher rate compared to the heart of males.

B

Photograph 3.6 A modern blood pressure and pulse rate measuring device

Age

Look at Table 3.2. As the age of a person increases, the person’s pulse rate becomes lower. Table 3.2 Average maximum pulse rate based on age Age (years)

Average maximum pulse rate (pulse per minute)

20

200

25

195

30

190

35

185

40

180

45

175

50

170

55

165

60

160

65

155

70

150 (Source: https://healthyforgood.heart.org/move-more/articles/target-heart-rates)

C Body health The pulse rate of a less healthy individual is normally higher or lower than the normal pulse rate. A pulse rate that is too high or too low is dangerous and can be life-threatening. 3.2.3

93

Importance of Maintaining a Healthy Heart The health of a heart should be given attention since its functions are very important in the continuity of human life. How are we able to enhance the knowledge and understanding of the health of the heart among Malaysians? Carry out Activity 3.4.

Activity 3.4 Enhancing the knowledge and understanding of the health of the heart through project-based learning using STEM approach Aim To study the relationship between dietary habits and lifestyle with health of the heart among the locals

• ICS, ISS, CPS, STEM • Project-based activity

Materials Printed materials and the Internet Instructions 1. Work in groups of five to six. 2. Study the following problem statement: Since 2005, heart disease remains as one of the main causes of death among Malaysians. This problem is closely related to their dietary habits and lifestyles. 3. Gather information related to the given problem statement as follows: (a) Types of heart diseases (b) Causes of heart diseases (c) Ways to prevent heart diseases (d) Other related matters 4. Discuss the information required to complete a K-W-L Chart as a guide to prepare a questionnaire. 5. The K-W-L Chart is prepared for a “Gallery Walk” session. 6. Prepare a questionnaire related to the topic of the study. 7. Carry out the study (at least 30 respondents) and analyse the data of the study. 8. Present the analysis of each item in the questionnaire using chart papers or MS PowerPoint software. 9. Present the findings of the study in the form of graphs using MS PowerPoint software.

94

3.2.4

Chapter 3: Transportation

10. After the presentation and discussion sessions, carry out the following activities in groups under the supervision of your teacher: (a) Presentation of the findings of your study in the school assembly (b) Health talk programme entitled “LET US TAKE CARE OF OUR HEART” as a co-curricular activity (c) Poster competition: Care for Our Heart (d) Produce an infographics brochure on the health care of the heart related to dietary habits and lifestyles

Note: What is the K-W-L Chart Strategy? The K-W-L Chart Strategy is an active reading strategy. It prepares students to predict what is read and is able to get other students to participate in the content of the topic discussed. K-W-L Chart Strategy K – What we know

W – What we want to know

L – What we learn

My Malaysia! M In July 2017, heart specialists at the Institut Jantung Negara (IJN) successfully replaced the damaged aorta of a heart patient with synthetic aorta. Gather further information on this at the following website: http://links.andl17.com/BT_Science_95_1

Formative Practice

3.2

1. What is blood circulatory system? 2. Differentiate the functions of the artery, capillary and vein. 3. State four factors that influence the pulse rate. 4. What is the importance of taking care of the heart? 3.2.4

95

3.3

Human Blood

Components and Constituents of Human Blood Blood transports oxygen and nutrients to the body cells. Blood also transports waste products from the body cells.

Name the component of blood which transports oxygen to all parts of the body. LIM

What is the colour of this component?

Science Careers Haematologists are medical specialists who study the components, constituents and diseases related to human blood.

Blood is a type of mixture because it can be separated into two components, a yellow liquid floating on top of a red liquid as shown in Photograph 3.7. The components of blood are normally separated using the centrifugal method. The mixture of blood is rapidly spun in a centrifuge as shown in Photograph 3.8.

Yellow liquid

Red liquid

Photograph 3.7 Two components of blood

Appearance of blood Appearance of blood before centrifugation after centrifugation Photograph 3.8 Separation of the components of blood using centrifugal method

96

3.3.1

Chapter 3: Transportation

Components of Blood Blood consists of a suspension of red blood cells, white blood cells, platelets and blood plasma as shown in Figure 3.12. Blood plasma is made up of approximately 90% water and 10% dissolved substances flowing to all parts of the body. These dissolved substances include nutrients, carbon dioxide, enzymes, hormones and waste products. Let us carry out Activity 3.5 to study the substances transported by blood.

Blood plasma (55%) White blood cells and platelets (<1%) Red blood cells (45%)

Figure 3.12 Components of human blood

Activity 3.5 To study the substances transported by blood

• CPS

• Discussion Instructions activity 1. Work in groups to gather information on the substances transported by blood, namely nutrients, gases, enzymes, hormones and waste products. 2. Carry out active reading on the gathered information. 3. Discuss the information gathered and present the findings of your group’s discussion. 4. Complete the following tree map to show the substances transported by blood and the characteristics of the substances.

Substances transported by blood

Nutrients

3.3.1

Gases

Enzymes

Hormones

Waste products

97

Human Blood Groups Antigens on Red Blood Cells Human blood can be classified into four blood groups, namely A, B, AB and O according to the type of antigen, if any, present on the red blood cells. The type of antigen present on red blood cells is A antigen or B antigen. The classification of blood groups A, B, AB and O is shown in Figure 3.13. Blood group B

Blood group A

Individuals with blood group B have only the B antigen.

Individuals with blood group A have only the A antigen. Red blood cell

A antigen

B antigen

Blood group AB

Blood group O

Individuals with blood group AB have both A and B antigens. A antigen

Individuals with blood group O do not have A or B antigens.

B antigen

Figure 3.13 Classification of human blood groups

Antibodies in Blood Plasma Blood plasma contains antibodies. The types of antibodies present in blood plasma are Anti-A and Anti-B antibodies. The types of blood, antigens and antibodies are as shown in Table 3.3. Table 3.3 Types of blood, antigens and antibodies Type of blood

Types of antigens (On the surface of red blood cells)

Types of antibodies (In blood plasma)

A

A

Anti-B

B

B

Anti-A

AB

A and B

–

O

–

Anti-A and Anti-B

An antibody will attack its corresponding antigen and cause the coagulation of blood to occur. This may cause death. For example, Anti-A antibody will coagulate with A antigen and Anti-B antibody will coagulate with B antigen. 98

3.3.1

3.3.2

Chapter 3: Transportation

Summary based on Table 3.3 • An individual who has Anti-A antibodies (type B blood) cannot receive types A and AB blood because these two blood types contain A antigen. • An individual who has Anti-B antibodies (type A blood) cannot receive types B and AB blood because these two blood types contain B antigen. • An individual who has type AB blood is free to receive all types of blood because there are no antibodies in his blood (universal recipient). • On the other hand, an individual who has type O blood cannot receive any other blood type because of the presence of Anti-A and Anti-B antibodies in his blood plasma. Therefore, whether a person can receive blood or not depends on the presence of antibodies in his blood plasma.

BRAIN TEASER Why is an individual who has type O blood known as the universal donor?

Compatibility of Blood Groups of Donors and Recipients

Before blood transfusion, we need to know that the blood groups of the donor and the recipient must be compatible as shown in Table 3.4. Otherwise, blood will coagulate. This situation can cause the death of the recipient. Table 3.4 Compatibility of blood groups of donors and recipients Blood group of donor

Blood group of recipient A

B

AB

O

A

✓

×

✓

×

B

×

✓

✓

×

AB

×

×

✓

×

O

✓

✓

✓

✓

Note: Compatibility of blood for transfusion (: compatible

×: not compatible)

Importance of Blood Donation Take note of the facts shown in Figure 3.14. Do you agree with the efforts to justify the importance of blood donation in the context of daily life? Carry out project-based learning using the STEM approach on the importance of blood donation through Activity 3.6.

Every day blood is needed to save lives. Blood is required for surgery, y, y, accident victims or to treat patients with leukaemia, haemophilia and other illnesses.

Figure 3.14 The importance of blood donation 3.3.2

99

Activity 3.6 To understand and solve issues related to blood donation in the context of daily life based on projects using the STEM approach Instructions 1. Work in groups to study the following statement:

• CPS, STEM • Project-based activity

Every day blood is needed to save lives. Blood is required for surgery, accident victims or to treat patients with leukaemia, haemophilia and other illnesses. 2. Prepare a project using the STEM approach to find creative and innovative solutions for the following issues: • Importance of blood donation • Criteria to be a blood donor • Issues related to blood donation • Methods of handling and storing the donated blood 3. Gather the information or existing solutions from the relevant and reliable government or private agencies as follows: National Blood Centre http:// links. andl17.com/BT_ Science_100_1

Ministry of Health Malaysia http://links. andl17. com/BT_Science_100_2

Malaysian Red Crescent http://links. andl17. com/BT_Science_100_3

4. Discuss the solutions obtained. Present the findings of your group discussion.

SCIENCE INFO A healthy individual with a mass of more than 45 kg and between 18 to 60 years old can donate blood. A donor can donate up to 0.5 litres of blood at any one time as shown in Photograph 3.9. When an individual donates blood, the total red blood cells in his body reduces. This forces the bone marrow to produce new cells. The individual will become more energised and able to function better.

Photograph 3.9 Blood donation campaign

100

3.3.2

3.3.3

Chapter 3: Transportation

Formative Practice

3.3

1. State four components of human blood. 2. State the largest component of human blood. 3. Mark ‘✓’ for blood groups of donor and recipient that are compatible and ‘×’ for the blood groups of donor and recipient that are not compatible. Blood group of donor

Blood group of recipient A

B

AB

O

A B AB O

4. (a) What is the importance of blood donation? (b) State two examples of diseases that can be treated through blood transfusion. 5. (a) Why is a blood donor with blood group O known as a universal donor? (b) Why is a blood recipient with blood group AB known as a universal recipient? (c) Why is the blood storage centre known as the blood bank? 6. (a) State two public places where people can donate blood. (b) Give one situation that requires a large amount of donated blood. 7. Figure 1 shows a bag filled with a donor’s blood that has been tested.

Figure 1

(a) Based on Figure 1, state the blood group of the donor. (b) Other than blood group, what else is tested in the blood sample of the donor? (c) The blood bag contains several chemical substances such as sodium citrate. What is the function of sodium citrate?

101

3.4

Transport System in Plants

Look at Figures 3.15(a), (b), (c) and (d). Can you explain the changes to this plant?

(a) Normal

(b) Wilted

LIM

(d) Normal

(c) Watered ered

Figure 3.15 Different conditions of a plant

Transpiration Transpiration is a process of water loss in the form of water vapour from the surface of leaves to the air through evaporation. Study Figure 3.16. Leaves are part of a plant where most water loss occurs through transpiration.

Loss of water through evaporation from the surface of leaves via transpiration

Pathway of water moving upwards in the plant Absorption of water through osmosis into the plant via its roots

Figure 3.16 Transpiration and absorption of water in a plant

102

3.4.1

Chapter 3: Transportation

Cross Section of a Leaf The epidermis of a leaf is made up of a single layer of epidermal cells covering both the upper and lower surfaces of the leaf, namely upper epidermis and lower epidermis as shown in Figure 3.17. Epidermal cells secrete a waxy cuticle which covers the outer surface of the leaf to reduce water loss during transpiration.

Cuticle

Xylem

Spongy mesophyll cell

Phloem

Lower epidermis

Stomatal pore

Figure 3.17 Cross section of a leaf

Function of Stoma during Transpiration Most of the water which is lost during transpiration in plants occurs through the stomatal pores found in the epidermis of the leaf as shown in Photograph 3.10. When photosynthesis takes place during the day, the stoma is usually open as shown in Photograph 3.10(a). What enters the guard cells that causes the stoma to open? Opening of stoma also causes the plant to lose water through transpiration. Photograph 3.10(b) shows closed stoma to reduce the loss of water through transpiration.

Palisade mesophyll cell

Upper epidermis

Guard cells

Stomatal pore

(a) Open stoma

(b) Closed stoma

Photograph 3.10 Open and closed stoma

Exudation (Guttation) Other than water loss from plants through transpiration, water is also lost from plants through exudation or guttation. Exudation or guttation is the water loss from plants in liquid form through hydathodes that are always open at the edges of the leaves. Guttation usually occurs at night or when the air humidity is high. What is the name of the water droplets that come out of leaves as shown in Photograph 3.11? Carry out Activity 3.7 to learn more about transpiration and exudation (guttation).

SCIENCE INFO Guttation is different from dew drops. Dew drops are formed from the condensation process of water vapour in the atmosphere into water.

Photograph 3.11 Exudation (guttation) 3.4.1

103

Activity 3.7 To make observations and create presentations to study the processes of transpiration and exudation (guttation) in plants

• ICS • Innovationbased activity

Instructions 1. Work in groups. 2. Each group is required to create a presentation to study the processes of transpiration and exudation (guttation) in plants.

Rate of Transpiration Transpiration occurs mainly through the stomata. Due to this, the number of stomata affects the rate of transpiration in plants. Transpiration is faster if the plant has more stomata. Other factors affecting the rate of transpiration are as shown in Figure 3.18. Carry out Experiments 3.2, 3.3, 3.4 and 3.5 to study the factors affecting the rate of transpiration.

Light intensity Temperature

Factors affecting transpiration Movement of air

Air humidity

Figure 3.18 Factors affecting the rate of transpiration

SCIENCE INFO The rate of transpiration of plants is normally estimated using a potometer as shown in Figures (a) and (b) below.

Young balsam plant Cotton wool Layer of Layer of oil oil

Cotton wool Conical flask

Young balsam plant Water reservoir Air bubble

Water

230.83 g

(a) Mass potometer

Electronic balance

Ruler

Beaker filled with water

(b) Bubble potometer

Mass potometer measures the rate of transpiration of a plant according to the rate of mass of water absorbed by the plant. Bubble potometer measures the rate of transpiration of a plant according to the rate of volume of water absorbed by the plant.

104

3.4.1

3.4.2

Chapter 3: Transportation

Experiment 3.2 Aim To study the effect of light intensity on the rate of transpiration Problem statement What is the effect of light intensity on the rate of transpiration? Hypothesis Increase in light intensity increases the rate of transpiration. Variables (a) manipulated variable : Light intensity (b) responding variable : Rate of transpiration (c) constant variables : Size and type of plant, air humidity, air movement, temperature and time Materials Young balsam plant, water, cotton wool and oil Apparatus Electronic balance, conical flask, clock and source of light such as sunlight or lamp Procedure 1. Set up the apparatus as shown in Figures 3.19 and 3.20. 2. Measure the mass of both apparatus set-ups and record your observation in a table. 3. After 3 hours, measure the mass of both apparatus set-ups once again and record your observation in the table.

4. Calculate the rate of transpiration of the young balsam plant that is exposed to a light source and also the one kept in the dark in a cupboard using the following formula: change in the mass of the potometer Rate of = transpiration time taken

Light source

Cupboard

Cotton wool

Cotton wool

Layer of oil

Layer of oil

Water 240.03 g

Figure 3.19

Water Electronic balance

242.50 g

Electronic balance

Figure 3.20

Conclusion Is the hypothesis accepted? What is the conclusion of this experiment? 3.4.2

105

Experiment 3.3 Aim To study the effect of air humidity on the rate of transpiration Problem statement What is the effect of air humidity on the rate of transpiration? Hypothesis Increase in air humidity decreases the rate of transpiration. Variables (a) manipulated variable : Air humidity (b) responding variable : Rate of transpiration (c) constant variables : Size and type of plant, light intensity, air movement, temperature and time Materials Young balsam plant, anhydrous calcium chloride, water, cotton wool and oil Apparatus Electronic balance, conical flask, plastic bag, clock and source of light such as sunlight or lamp Procedure 1. Set up the apparatus as shown in Figures 3.21 and 3.22. 2. Measure the mass of both apparatus set-ups and record your observation in a table.

3. After 3 hours, measure the mass of both apparatus set-ups once again and record your observation in the table. 4. Calculate the rate of transpiration in both apparatus set-ups.

Plastic bag

Cotton wool

239.67 g

Figure 3.21

Anhydrous calcium chloride

Cotton wool

Layer of oil

Layer of oil

Water

Water

Electronic balance

237.82 g

Electronic balance

Figure 3.22

Conclusion Is the hypothesis accepted? What is the conclusion of this experiment?

106

3.4.2

Chapter 3: Transportation

Experiment 3.4 Aim To study the effect of air movement on the rate of transpiration Problem statement What is the effect of air movement on the rate of transpiration? Hypothesis Increase in air movement increases the rate of transpiration. Variables (a) manipulated variable : Air movement (b) responding variable : Rate of transpiration (c) constant variables : Size and type of plant, light intensity, air humidity, temperature and time Materials Young balsam plant, water, cotton wool and oil Apparatus Electronic balance, fan, conical flask and clock Procedure 1. Set up the apparatus as shown in Figures 3.23 and 3.24. 2. Measure the mass of both apparatus set-ups and record your observation in a table.

239.52 g

Figure 3.23

3. After 3 hours, measure the mass of both apparatus set-ups once again and record your observation in the table. 4. Calculate the rate of transpiration in both apparatus set-ups.

Cotton wool

Cotton wool

Layer of oil

Layer of oil

Water

Water

Electronic balance

240.04 g

Electronic balance

Figure 3.24

Conclusion Is the hypothesis accepted? What is the conclusion of this experiment?

3.4.2

107

Experiment 3.5 Aim To study the effect of temperature on the rate of transpiration Problem statement What is the effect of temperature on the rate of transpiration? Hypothesis Increase in temperature increases the rate of transpiration. Variables (a) manipulated variable : Temperature (b) responding variable : Rate of transpiration (c) constant variables : Size and type of plant, light intensity, air humidity, air movement and time Materials Young balsam plant, water, cotton wool and oil Apparatus Electronic balance, conical flask and clock Procedure 1. Set up the apparatus as shown in Figures 3.25 and 3.26. 2. Measure the mass of both apparatus set-ups and record your observation in a table.

244.73 g

Figure 3.25

3. After 3 hours, measure the mass of both apparatus set-ups once again and record your observation in the table. 4. Calculate the rate of transpiration in both apparatus set-ups.

Room that is cold or at low temperature

Room that is hot or at high temperature

Cotton wool

Cotton wool

Layer of oil

Layer of oil

Water

Water

Electronic balance

241.20 g

Electronic balance

Figure 3.26

Conclusion Is the hypothesis accepted? What is the conclusion of this experiment?

108

3.4.2

Chapter 3: Transportation

Structures and Functions of the Components in Vascular Bundles of Plants Transpiration facilitates the transportation of water and mineral salts in plants. During transpiration, water and dissolved mineral salts diffuse into plants through the roots to the stem and leaves as shown in Figure 3.27. Xylem Phloem Vascular bundle

Phloem

Xylem

Cross section of leaf Cross section of stem

Sucrose transported from the leaf to other parts of the plant

Xylem Vascular bundle Phloem

Water and mineral salts absorbed by the roots

Cross section of root

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Figure 3.27 Transport system in a flowering plant and distribution of vascular bundles in the leaves, stem and roots

The transport system in flowering plants is made up of two transport tissues, namely xylem and phloem, which are found in a group of vessels known as vascular bundles. Observe the formation pattern of the vascular bundles in the root, stem and leaf as shown in Figure 3.27. Is the formation pattern of vascular bundles in the root, stem and leaf the same or different? Visit the following websites and watch the video to find out the position and structure of the xylem and phloem in a vascular bundle. Info 2 http://links. andl17.com/BT_ Science_109_3

Video 5 *(

.

,

http://links. andl17.com/BT_ Science_109_2

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Info 1

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3.4.3

109

Direction of Water and Food in the Transport System of Plants In Activity 3.8 and Activity 3.9, we will investigate the functions of the xylem and phloem.

Activity 3.8

Inquiry-based activity

Studying the direction of water in plants Aim: To study the direction of water in a plant Materials Balsam plant and eosin solution (red dye) Apparatus Conical flask, glass cover, folding knife, microscope and slide Instructions 1. Wash the roots of the balsam plant carefully with water. 2. Immerse the roots of the balsam plant in a conical flask filled with eosin solution as shown in Figure 3.28. Leaf

Safety Precautions • Avoid coming in contact with the eosin solution as it will stain your clothes. • Be careful when using a folding knife. Eosin solution Roots

Figure 3.28 3. After 30 minutes, make thin cross-sections of the leaf, stem and root of the plant using a folding knife. 4. Examine each of the sections under a microscope. 5. Draw a labelled diagram for each section that has been observed. Identify and label the tissues that have been coloured red by the eosin solution. Questions 1. Is the eosin solution spread evenly or does it have a specific pattern in the leaf, stem and root of the plant? 2. Name the part which is coloured red in the cross-sections of the leaf, root and stem in this activity. 3. What is the conclusion from this activity?

110

3.4.3

Chapter 3: Transportation

Activity 3.9

Inquiry-based activity

Studying the direction of food in plants Aim: To investigate the direction of food in a plant

Safety Precaution

Material Woody plant

Handle the scalpel with care.

Apparatus Scalpel

Instructions 1. Choose a healthy branch of a woody plant. 2. Cut a complete ring out of the bark of the plant including the phloem as shown in Figure 3.29.

Figure 3.29

Figure 3.30

3. Water the plant every day and expose it to enough light so that the plant can carry out photosynthesis as shown in Figure 3.30. 4. Observe and sketch the changes, if any, in the branch of the woody plant with its bark removed after two to three months. Questions 1. Sketch the changes in the part of the branch with its bark removed after two to three months.

(a) Beginning of activity

(b) End of activity

2. What is the conclusion from this activity? 3.4.3

111

Case Study Based on your understanding of the transport system in plants, discuss examples of hypothetical situations such as when there are no xylem or phloem vessels in the following context: Propose and discuss: Ř ways to transport water and dissolved mineral salts in plants without xylem Ř ways to transport sucrose from leaves to all parts of plants without phloem Ř adaptations in the transport system to replace xylem and phloem vessels in plants

Formative Practice 3.4 1. What is the meaning of transpiration? 2. Underline the correct answer on the transport system in plants. (a) Loss of water from plants through transpiration is in the form of (liquid/vapour) while loss of water through exudation is in the form of (liquid/vapour). (b) The tissue that transports water in plants is (phloem/xylem) while the tissue that transports sucrose is (phloem/xylem). 3. State four factors that affect the rate of transpiration in plants. 4. Why is dye used to investigate the direction of water in xylem? 5. Figure 1 shows the structure of xylem and phloem in vascular bundles in different parts of a plant. P:

R:

Q: S: Cross section of stem

T:

Cross section of root

U:

Cross section of leaf

Figure 1

Label P, Q, R, S, T and U using the following words: Xylem

112

Phloem

3.4.3

Chapter 3: Transportation

3.5

Blood Circulatory System in Animals and Transport System in Plants

Studies on the blood circulatory system in animals and transport system in plants have made us aware of the uniqueness of circulatory systems to the continuity of life of organisms created by God. What are the similarities and differences between the blood circulatory system in animals and the transport system in plants? Study Figure 3.31. Blood circulatory system in animals

Similarities

Transport system in plants

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Differences

Tubular system with heart and valves

Structure

Three types of vessels: artery, capillary and vein

Types of transport vessels

Arteries, capillaries and veins are connected to form one continuous vessel

Connection between transport vessels

System of vessels without pump or valve

Two types of vessels: xylem and phloem

Xylem and phloem are not connected and are two separate vessels

Figure 3.31 Comparison between blood circulatory system in animals and transport system in plants

Formative Practice 3.5 Formative Practice 3.5 1. Give one similarity and one difference between the blood circulatory system in animals and the transport system in plants. 2. Why should we be thankful for the uniqueness of the circulatory system to the continuity of life of organisms? 3.5.1

113

114

Summary Transportation in

Simple organisms

Complex organisms involve

No specialised transport system

Substances needed by cells such as oxygen and nutrients from external environment enter the cells through diffusion

Excretory products of cells such as carbon dioxide and water are eliminated from the cells to the external environment through diffusion

Specific transport systems

Transport system in plants

Blood circulatory system in

involves

Humans

Vertebrates

Vascular bundles

involves

Mammals, reptiles, amphibians, birds, fish

made up of

Blood vessels

Heart

needs to be taken care of

Arteries, capillaries, veins

Pulse rate

To ensure healthy heart

Blood

transports substances such as

Nutrients, gas, enzymes, hormones, excretory products

Xylem

Phloem

groups

transports

transports

A, B, AB, O

Water, dissolved mineral salts

Food

Chapter 3: Transportation

Self-reflection S elf lf-refl fle ec cttiion on After studying this chapter, you are able to: 3.1 Transport System in Organisms Describe the function of transport systems in complex and simple organisms. Compare and contrast the functions of transport systems in complex and simple organisms. Justify the importance of the function of transport system in organisms. 3.2 Blood Circulatory System Generalise the meaning of blood circulatory system in animals. Communicate to explain the structure and functions of a heart and blood vessels in human blood circulatory system. Carry out experiments to study factors that affect pulse rate. Justify the importance of maintaining a heathy heart. 3.3 Human Blood Separate the components and constituents of human blood. Identify blood groups and the effects of receiving incompatible blood groups. Communicate the importance of blood donation in context of daily life. 3.4 Transport System in Plants Describe transpiration in plants. Carry out experiments to investigate the factors affecting the rate of transpiration. Differentiate between the structures and functions of components in a vascular bundle of a plant. 3.5 Blood Circulatory System in Animals and Transport System in Plants Compare blood circulatory system in animals with transport sytem in plants.

115

Summative Practice

3

Answer the following questions: 1. Solve the crossword puzzle below with the correct answers. (e) (d) (a)

P

E

P

T

O

(f)

(c)

(b)

A

C

I

Across (a) Carrying out vigorous activities increases the rate of (b) Loss of water from plants occurs through the process of (c) Blood vessel with the thinnest wall is the . Down (d) Sucrose is transported by the (e) The organ which pumps blood is the (f) Blood group A has one type of

. .

. . .

2. Mark ‘✓’ for the correct statement and ‘×’ for the incorrect statement on transport in organisms. (a) Amoeba sp. does not have a specific transport system. (b) The function of transport system is only to carry useful substances to all parts of the body of an organism. (c) In a systemic circulatory system, blood flows from the heart to the lungs and returns to the heart. (d) Coagulation of the blood is an effect from the action of receiving a compatible blood group. 116

Chapter 3: Transportation

3. Figure 1 shows three types of blood vessels in the human body.

P

Q

R

Figure 1

(a) Name the structure in blood vessel P that is not shown in Figure 1. (b) State the function of blood vessel Q. (c) Explain the adaptations in the structure of the following blood vessels: (i) Blood vessel Q (ii) Blood vessel R 4. (a) State five substances that are transported in the human body. (b) State three substances that diffuse through the membrane or wall of plant cells and are transported in plants. (c) Why do plant cells not need a supply of oxygen from outside during the day? 5. (a) Underline the correct answers. (i) The (‘lub’/‘dub’) sound is produced by the closure of the valves at the aorta and pulmonary artery. (ii) The (‘lub’/‘dub’) sound is produced by the closure of the valves between the atria and ventricles. (iii) The pressure reading of blood flowing out of the heart is known as (diastolic/systolic). (iv) The pressure reading of blood flowing into and filling the heart is known as (diastolic/systolic). (b) Between diastolic and systolic pressure readings, which is higher? Explain your answer. 6. (a) Table 1 shows four blood donors from different blood groups. Table 1

Blood donor

Blood group

Dollah

A

Eric

B

Sita

AB

Roy

O

117

A road accident victim lost a lot of blood. He is confirmed to have blood from group B. (i) Which blood donor is suitable to donate blood to the victim? (ii) Explain the effect to the victim if he receives blood from Sita. (b) The Red Crescent Society launched a ‘Let’s Donate Blood’ campaign to replenish the blood bank. Three individuals are interested to take part in the campaign. Table 2 shows their age, gender and body mass. Table 2

Individual

Age (years)

Gender

Body mass (kg)

1

15

Male

62

2

30

Female

70

3

61

Male

66

(i) Based on Table 2, which individual is most suitable to donate blood? Explain your answer. (ii) What is the special additional condition for blood donors with regard to their suitability to donate blood? 7. Figure 2 shows a cross section of the stem of a plant. X

Y

Figure 2

(a) State one function of X. (b) State the structure in the stem of the plant that transports water from the roots to the leaves. (c) (i) What will happen to the plant if a ring of its bark and X are removed? Explain your answer. (ii) What will happen to the plant if X and Y are removed?

118

Chapter 3: Transportation

Focus on HOTS 8. Figure 3 shows the apparatus set-up of an investigation to study the factors that affect the rate of transpiration of a plant and the results after three hours. Light source

Cupboard

Cotton wool

Cotton wool

Layer of oil

Layer of oil

Water 300 g

Water Electronic balance

300 g

Electronic balance

Results: Set

Initial mass (g)

Final mass (g)

A

300

246

B

300

264

Rate of transpiration (g/min)

Figure 3

Calculate the rate of transpiration in this investigation. 9. Three students, Badrul, Azizah and Murad carried out a fitness activity to investigate the health of their heart. Table 3 shows the pulse rates for the three of them before and after the fitness activity. Table 3

Condition

Pulse rate (number of beats per minute) Badrul

Azizah

Murad

63

70

65

Immediately after the activity

130

95

94

15 minutes after the activity

75

71

75

Before the activity

(a) Name the student who is most at risk of having heart disease. Explain your answer. (b) Name the student who has the healthiest heart. Explain your answer. 119

10. All the members of the Science Club in your school have agreed to carry out a project to plant herbs in school. Herbs that are to be planted will grow well when the rate of transpiration is moderate and the exposure to sunlight is sufficient to carry out photosynthesis. Figure 4 shows three areas: • Area A, inside a dark laboratory • Area B, in a shaded bright area • Area C, in a hot school field under the sun

Zinc roof

A

C B

Figure 4

(a) Based on Figure 4, which is the most suitable area for the project site? Explain your answer. (b) Construct the most suitable model to make this project a success. The model is a glasshouse or greenhouse in which the air humidity and light intensity can be controlled. The construction of the model requires the use of the following materials:

Water A tr transparent umbrella

120

Container and a roll of tissue

THEME

2

Exploration of Elements in Nature At the end of the 17th century, the number of metals listed in the reactivity series of metals was only twelve! Why? What changes do you expect in the reactivity series of metals in future?

UNUNUNIUM NUNUNIUM (272)

UNUNBIUM (277)

Colourful fireworks display is one of the applications of thermochemistry. Does the chemical reaction of the fireworks display release or absorb heat? What is the use of heat in the fireworks display ?

121

Chapter Chapter Chapte hapte apte apt p er

1 4

Reactivity of Metals

What are minerals? What are the uses of minerals in daily life? What is the reactivity series of metals? How is the process of tin extraction carried out in Malaysia?

Let’s study Variety of minerals Reactivity series of metals Extraction of metals from their ores

122

Science Gallery According to existing records, the first metal used by humans is gold. Gold was discovered in its mineral element form in a cave in Spain in 40 000 BC. Due to the importance of various metals used in daily life, scientists have constructed a reactivity series of metals to understand the order of metals according to their reactivity towards oxygen as shown in the figure below.

Reactivity of metals towards oxygen increases

K

Potassium

Na

Sodium

Ca

Calcium

Mg

Magnesium

Al

Aluminium

C

Carbon

Zn

Zinc

H

Hydrogen

Fe

Iron

Sn

Tin

Pb

Lead

Cu

Copper

Hg

Mercury

Ag

Silver

Au

Gold

Based on this reactivity series of metals, we can determine the properties of metals such as the reactions of metals with oxygen, acid or water. We can also understand how the extraction of a metal from its ore is carried out. The mining issues of metals can also be highlighted to increase awareness on the importance of sustainable management and development of the environment.

Keywords Mineral Natural compound Element Earth’s crust

Reactivity series of metals Extraction of metal Mining issues Physical characteristic

Chemical characteristic Blast furnace Slag

123

4.1

Variety of Minerals

Look at Photograph 4.1. This photograph shows various types of ores found in Earth’s crust. Each type of ore is different in terms of colour, structure, shape and texture because the ores contain different minerals.

What are the names of these ores?

LIM XUAN YUN

Photograph 4.1 Various types of ores found in Earth’s crust

Try to guess, how many minerals exist on this Earth! Then, compare your guess with the number of minerals listed in the following website: http://links.andl17.com/ BT_Science_124 and click “Recent new minerals”

Is your guess close to the number of minerals listed by the International Mineralogical Association, IMA?

124

SCIENCE INFO Mineralogy or the study of minerals is an active field of science because the number and properties of minerals keep increasing.

My World of Science Soon, all cars using petrol or diesel will be replaced with electric cars. This can be realised with the discovery of two minerals which can produce long lasting batteries. These two minerals are lithium and cobalt.

4.1.1

Chapter 4: Reactivity of Metals

Various Forms of Minerals in Earth’s Crust Minerals are solid elements or compounds present naturally with definite crystalline structures and chemical compositions. Various minerals are contained in rocks found in Earth’s crust. Minerals that can be found in Earth’s crust are made up of the following:

A

Elements

Gold

Silver Photograph 4.2 Gold and silver

B

Compounds

Bauxite

Hematite

Galena

Cassiterite

Photograph 4.3 Bauxite, hematite, galena and cassiterite

The common and systematic names of natural compounds and the combination of their elements are shown in Table 4.1. Table 4.1 Natural compounds and their elements Common name

4.1.1

Systematic name

Combination of elements

Hematite

Iron(III) oxide

Iron, oxygen

Cassiterite

Tin(IV) oxide

Tin, oxygen

Quartz

Silicon dioxide

Silicon, oxygen

Bauxite (aluminium ore)

Aluminium oxide

Aluminium, oxygen

Galena (lead ore)

Lead(II) sulphide

Lead, sulphur

Pyrite

Iron(II) sulphide

Iron, sulphur

Calcite

Calcium carbonate

Calcium, carbon, oxygen

125

Natural Compounds are the Combination of Several Elements BRAIN TEASER The compound shown in this photograph has a common name, that is bauxite or aluminium ore. Its systematic name is aluminium oxide. Who normally uses the common and systematic names for this compound?

My World of Science Photograph 4.4 Limestone quarry

Calcium silicate is a natural compound that can be used as an additive in human food.

Limestone is a mineral that has many uses in daily life such as in the construction of roads and buildings, and for table tops. Is limestone a natural compound made up of a combination of several elements? Let us investigate this by carrying out Activity 4.1. Then, carry out Activity 4.2 to create a multimedia presentation on examples of properties of natural minerals and their uses in daily life.

Activity 4.1

Inquiry-based activity

To show that a natural compound is a combination of several elements Materials Calcium carbonate powder, clear limewater and dilute hydrochloric acid Apparatus Boiling tube labelled P, boiling tube labelled Q, spatula, test tube, Bunsen burner, rubber stopper with delivery tube, filter funnel and retort stand with clamp Instructions 1. Put a spatula of calcium carbonate into boiling tubes P and Q. 2. Pour 10 ml of dilute hydrochloric acid into boiling tube P. 3. Set up the apparatus to test the property of the gas released by passing it through limewater as shown in Figure 4.1.

126

4.1.2

Chapter 4: Reactivity of Metals

Boiling tube P

Boiling tube Q Test tube

Calcium carbonate and dilute hydrochloric acid

Retort stand

Limewater

Test tube

Calcium carbonate

Limewater

Retort stand Heat

Figure 4.1 Apparatus set-up to test gas released

Figure 4.2 Apparatus set-up to heat calcium carbonate

4. Observe and record the changes in the limewater, if any, in a table. 5. Set up the apparatus as shown in Figure 4.2. Heat the calcium carbonate in boiling tube Q strongly until gas is released. 6. Observe and record the changes in the limewater, if any, in the table.

Safety Precaution Do not point the mouth of the boiling tube that is being heated at yourself or others.

Observation Condition of limewater

Action on calcium carbonate

before gas passes through

after gas passes through

Calcium carbonate mixed with dilute hydrochloric acid Calcium carbonate heated strongly Questions 1. Name the gas that is tested using limewater. 2. How is the test for the gas carried out? Explain. 3. Name the gas released when calcium carbonate: (a) reacts with dilute hydrochloric acid (b) is heated strongly 4. Complete the word equation for each reaction in question 3. (a) Calcium carbonate + hydrochloric acid (b) Calcium carbonate

heated

+

+

+

5. Name three elements that are combined in calcium carbonate.

4.1.2

127

SCIENCE INFO Calcium carbonate is a natural compound that exists in various forms, colours and textures such as calcite, limestone, marble, chalk, coral reefs and shells of marine animals.

Limestone Li

M Marble bl

Ch Chalk lk

C Calcite l i

Activity 4.2 To create a multimedia presentation on examples of properties of natural minerals and their uses in daily life

• Technologybased activity

Instructions 1. Work in groups. 2. Gather and discuss information on examples of properties of natural minerals and their uses in daily life. Then, fill in the information in the table as follows: Natural mineral

Physical characteristics

Chemical characteristics

Uses in daily life

3. Present the findings of your group discussion in class.

Formative Practice

4.1

1. What are minerals? 2. Name one example of a mineral in the form of: (a) element (b) natural compound 3. State two examples of minerals, their chemical or physical characteristics and their uses in daily life. 128

4.1.3

Chapter 4: Reactivity of Metals

4.2

Reactivity Series of Metals

Compare and contrast the reactions of metals with oxygen in the air as shown in Photograph 4.5.

(b) Iron exposed to air

(a) Magnesium burning in air

Photograph 4.5 Reactions between metals and oxygen

Is the vigour of the reactions of different metals such as magnesium and iron with oxygen the same or different? In a vigorous reaction between a more reactive metal such as magnesium and oxygen, a bright flame is observed as shown in Photograph 4.5(a).

In a less vigorous reaction between a less reactive metal such as iron and oxygen, only a glow or slow change in colour is observed as shown in Photograph 4.5(b).

Constructing Reactivity Series of Metals Different metals have different reactivities towards oxygen. Metals that are more reactive towards oxygen react more vigorously with oxygen. Reactivity series of metals is a list of metals arranged in order of their reactivity towards oxygen as shown in Figure 4.3.

Au Ag Hg Cu Pb Sn

Fe

Zn

Al

Mg Ca

Na

K

Reactivity of metals towards oxygen increases

Figure 4.3 Reactivity series of metals towards oxygen

Let us carry out Activity 4.3 to compare and contrast the reactivity of several different metals towards oxygen. 4.2.1

129

Activity 4.3

Inquiry-based activity

Investigating the reactivity of several metals towards oxygen Aim: To study the reaction of heating metals such as magnesium, aluminium, zinc, iron and lead with oxygen Materials Potassium manganate(VII) crystals, magnesium powder, aluminium powder, zinc powder, iron powder, lead powder and glass wool Apparatus Boiling tube, retort stand with clamp, porcelain plate, spatula and Bunsen burner Instructions

Safety Precautions • Glass wool fibres are very dangerous. Use forceps to handle them. Make sure you wear safety glasses and cover your mouth and nose when handling glass wool. Do not allow glass wool to enter your body. Wash your hands after handling glass wool. • Potassium manganate(VII) crystals and metal powder can explode if mixed during heating. Make sure both of these materials are always kept apart. • Make sure you wear safety glasses and do not look directly at the flame caused by heating metal powder with oxygen. • Use only a small amount of metal powder.

1. Put a spatula of potassium manganate(VII) crystals into a dry boiling tube. Use some glass wool to prevent it from coming out as shown in Figure 4.4.

Glass wool

Porcelain plate

Potassium manganate(VII) crystals

5 *(

Heat .

,

Heat

Reaction between metal and oxygen :

Metal powder

     7(

Figure 4.4 2. Clamp the boiling tube horizontally onto the retort stand as shown in Figure 4.4. 3. Put a spatula of magnesium powder on a small porcelain plate. Put the porcelain plate into the boiling tube as shown in Figure 4.4.

130

4.2.1

Chapter 4: Reactivity of Metals

4. Heat the magnesium powder strongly. Then, heat the potassium manganate(VII) crystals. 5. Observe the vigour of the reaction. 6. Record your observations in a table. Take a video recording and/or photographs of the reaction. 7. Repeat steps 1 to 6 using the powdered form of the metals listed in the following table: Observations Observation

Metal

Metal burns very quickly and brightly

Metal burns quickly and brightly

Metal burns slowly

Metal glows brightly

Metal glows dimly

Magnesium Aluminium Zinc Iron Lead Questions 1. Complete the word equation for the reaction of each metal with oxygen. (a) Magnesium + oxygen (b) Aluminium + oxygen (c) Zinc + oxygen (d) Iron + oxygen (e) Lead + oxygen 2. State the relationship between the vigour of the reactions and the reactivity of the metals towards oxygen. 3. Based on the results from this activity, complete the following sequence of metals according to their decreasing reactivity towards oxygen.

4.2.1

131

Position of Carbon in the Reactivity Series of Metals The position of a metal in the reactivity series of metals depends on the reactivity of the metal when reacting with oxygen. Can the position of a non-metal such as carbon and hydrogen in the reactivity series of metals be determined according to the reactivity of carbon and hydrogen with oxygen? Let us carry out Activity 4.4 to determine the position of carbon in the reactivity series of metals.

Activity 4.4

BRAIN TEASER Write the word equation for the reaction between: • carbon and oxygen • hydrogen and oxygen

Inquiry-based activity

Determining the position of carbon in the reactivity series of metals Aim: To determine the position of carbon in the reactivity series of metals by heating the following substances: (a) Zinc oxide with carbon (b) Aluminium oxide with carbon (c) Lead(II) oxide with carbon Materials Carbon powder, zinc oxide, aluminium oxide and lead(II) oxide Apparatus Crucible, spatula, Bunsen burner, pipeclay triangle and tripod stand Instructions A Teacher’s demonstration Observe carefully when the teacher conducts a demonstration of steps 1 to 4 as follows: 1. Put a spatula of carbon powder and a spatula of zinc oxide powder into a dry crucible. Mix the powders evenly in the crucible. 2. Place the crucible on a pipeclay triangle on a tripod stand as shown in Figure 4.5. Mixture of carbon and metal oxide

Crucible Pipeclay triangle

5 *(

.

,

Heat

:

Position of carbon in the reactivity series of metals

     7(

Figure 4.5

132

4.2.2

Chapter 4: Reactivity of Metals

3. Heat the mixture in the crucible strongly. 4. Observe the changes that happen to the mixture. Record your observation in a table. B Student’s activity Repeat steps 1 to 4 replacing zinc oxide with aluminium oxide and lead(II) oxide. Observations Mixture

Observation

Reactivity of carbon

Zinc oxide and carbon Aluminium oxide and carbon Lead(II) oxide and carbon Questions 1. Complete the word equation for each reaction of metal oxide with carbon, if any. (a) Zinc oxide + carbon (b) Aluminium oxide + carbon (c) Lead(II) oxide + carbon 2. Name the metal that is less reactive than carbon. Explain your answer. 3. Based on the results of this activity, complete the following sequence to show the arrangement of elements according to their increasing reactivity towards oxygen:

Increasing reactivity

4. Give one application of the position of carbon in the reactivity series of metals for industrial use. Explain your answer. 5. Underline the correct answer for the following statements: (a) If carbon can remove oxygen from a metal oxide, it means carbon is (more/less) reactive than the metal. (b) If carbon cannot remove oxygen from a metal oxide, it means carbon is (more/less) reactive than the metal. 4.2.2

133

Position of Hydrogen in the Reactivity Series of Metals The position of hydrogen in the reactivity series of metals can be determined through interpretation of the data based on Figure 4.6 and Table 4.2. Figure 4.6 shows the apparatus set-up used to determine the position of hydrogen in the reactivity series of metals. Thistle funnel Hydrogen gas

Burning of excess hydrogen gas

Dry hydrogen gas

Combustion tube Dilute sulphuric acid + copper(II) sulphate solution

Heat

:

U-tube

Metal oxide on porcelain plate 5 *(

.

,

Zinc

     7(

Anhydrous calcium chloride

Figure 4.6 Apparatus set-up to determine the position of hydrogen in the reactivity series of metals

Table 4.2 shows the results from activities carried out by chemists to determine the position of hydrogen in the reactivity series of metals. Table 4.2 The results from activities to determine the position of hydrogen in the reactivity series of metals Mixture

Observation

Inference

Hydrogen and aluminium oxide

Aluminium oxide does not glow. Aluminium oxide is white in colour.

Hydrogen does not reduce aluminium oxide.

Hydrogen and zinc oxide

Zinc oxide does not glow. Zinc oxide turns yellow when hot and white on cooling.

Hydrogen does not reduce zinc oxide.

Hydrogen and iron(III) oxide

Iron(III) oxide burns brightly. Reddish brown powder turns shiny grey.

Iron is produced. Hydrogen reduces iron(III) oxide to iron.

Hydrogen and lead(II) oxide

Lead(II) oxide burns brightly. Yellow powder turns shiny grey.

Lead is produced. Hydrogen reduces lead(II) oxide to lead.

Hydrogen and copper(II) oxide

Copper(II) oxide burns very brightly. Black powder turns brown.

Copper is produced. Hydrogen reduces copper(II) oxide to copper.

Based on the results given in Table 4.2, (a) Underline the correct answers about the reactivity of hydrogen. (i) Hydrogen is (less/more) reactive than aluminium. (ii) Hydrogen is (less/more) reactive than zinc. 134

4.2.2

Chapter 4: Reactivity of Metals

(iii) Hydrogen is (less/more) reactive than iron. (iv) Hydrogen is (less/more) reactive than copper. (v) Hydrogen is (less/more) reactive than lead. (b) State the metals which are more reactive than hydrogen. (c) State the metals which are less reactive than hydrogen.

Conclusion on the Position of Carbon and Hydrogen in the Reactivity Series of Metals In Activity 4.3, you have arranged metals according to their reactivity towards oxygen. The arrangement you made is part of the reactivity series of metals. In Activity 4.4 and data interpretation in Table 4.2, you determined the position of carbon and hydrogen in the reactivity series of metals. Even though the reactivity series of metals is an arrangement of non-metals such as carbon metals according to their reactivity towards oxygen, the position of n hydrogen and hy ydroggen is also shown in the reactivityy series of metals (Figure 4.7).

My World of Science

Reactivity Series of Metals

Na

Sodium

Ca

Calcium

Mg

Magnesium

Al

Alumimium

C

Carbon

Zn

Zinc

H

Hydrogen

Fe

Iron

Sn

Tin

Pb

Lead

Cu

Copper

Hg

Mercury

Ag

Silver

Au

Gold

SCIENCE INFO Coal is one of the minerals found Malaysia. About 80% of the coal in Ma found in Sarawak, 19% in Sabah is fou dan 1% in Peninsular Malaysia. The largest coal reserve is located in large Merit Pila, Sarawak.

5 *(

Figure 4.7 Fi 47 R Reactivity eacti tivit ity series seriies off metals mettals l 4.2.2

.

,

Potassium

:

Reactivity of metal towards oxygen increases

K

Lithium Lith Li th batteries will explode whe when heated. Due to this, pas passengers are not allowed to keep lithium batteries in their kee luggage placed in aircrafts. lugg

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135

Formative Practice

4.2

1. What is reactivity series of metals? 2. Figure 1 shows the reaction between metal X and oxygen in the air.

Figure 1

(a) Is metal X reactive towards oxygen? Explain your answer. (b) Metal Y glows brightly when it reacts with oxygen. Is metal Y more or less reactive than metal X? (c) If metal Z does not react with oxygen, arrange metals X, Y and Z in the reactivity series of metals based on their reactions.

Reactivity of metal towards oxygen decreases

3. Underline the correct answers. (a) Metals are arranged in the reactivity series of metals based on the reaction of the metal towards (carbon/oxygen). (b) The most reactive metal in the reactivity series of metals is (calcium/potassium). (c) The reactivity series of metals is applied in the (melting/extraction) of metals from their ores. 4. (a) State the most reactive metal in the reactivity series of metals. (b) State the least reactive metal in the reactivity series of metals. 5. (a) State two non-metal elements that are included in the reactivity series of metals. (b) Why are these two non-metal elements included in the reactivity series of metals? 136

Chapter 4: Reactivity of Metals

4.3

Extraction of Metals from their Ores

Extraction of Metals Extraction of metals is the process to obtain metals from their ores. Observe the relationship between the position of carbon and hydrogen in the reactivity series of metals and the method used to extract metals from their ores as shown in Figure 4.8.

My Malaysia M The extraction of iron from its ore by a local company in Malaysia. http://links.andl17.com/BT_Science _137_2

Reactivity Series of Metals K

Potassium

Na

Sodium

Ca

Calcium

Mg

Magnesium

Al

Aluminium

C

Carbon

Zn

Zinc

H

Hydrogen

Fe

Iron

Sn

Tin

Pb

Lead

Cu

Copper

Hg

Mercury

Ag

Silver

Au

Gold

Extraction through electrolysis of metallic compounds in molten form.

Extraction through reduction of metal oxides by carbon.

For metals higher than carbon in the reactivity series of metals, the extraction of the metal from its metallic compound is through electrolysis.

For metals lower than carbon in the reactivity series of metals, the extraction of the metal from its ore is through the reduction of its oxide with carbon.

Extraction of the metals is done through direct heating of the metallic compounds.

Exist in the form of elements in Earth’s crust.

Figure 4.8 Reactivity series of metals and methods of extracting metals from their ores 4.3.1

137

Process of Iron Extraction

1

A mixture of concentrated iron ore or iron oxide, coke and limestone is added into a blast furnace through the top.

5 *(

.

,

:

The extraction of iron from its ore is carried out in a blast furnace as shown in Figure 4.9.

7(

Blast furnace

2

A very hot blast of air is pumped into the furnace through the bottom.

Slag is released Molten metal is released

Figure 4.9 Extraction of iron in a blast furnace

138

4.3.1

Chapter 4: Reactivity of Metals

3

Reactions that occur in the furnace at high temperature. Production of iron t
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4.3.1

139

Activity 4.5 To create a multimedia presentation explaining how metal extraction is carried out based on the processes of iron and tin extractions in Malaysia

• ICS • Technologybased activity

Instructions 1. Work in groups. 2. Gather materials from various media on how metals are extracted in the mining sector in Malaysia. 3. Examples of websites are as follows: • Source of minerals in Malaysia http://links.andl17.com/ BT_Science_140

• Process of tin extraction in Malaysia http://links.andl17. com/BT_Science_140_2

4. Discuss the processes of iron and tin extractions from their ores. 5. Present the findings of your group discussion using multimedia presentation such as MS PowerPoint.

Mining Issues in Malaysia Mining issues in Malaysia and their impact on life in the local or global context are shown in Figure 4.10.

Usage of large amount of electrical energy

Air pollution due to burning of fuels

Water pollution due to cleaning of ore

Air pollution by gases released from blast furnaces

Mining issues in Malaysia

Soil erosion due to mining of ore

Sound pollution from mining machinery

Destruction of habitat due to construction of mines

Figure 4.10 Mining issues in Malaysia and their impact

Let us carry out Activity 4.6 to study problems of mining issues in Malaysia shown in Figure 4.10. 140

4.3.2

Chapter 4: Reactivity of Metals

Activity 4.6 To solve problems of mining issues in Malaysia Instructions 1. Work in groups. 2. Gather information on issues of poorly planned mining activities in Malaysia and their impact on life in the local or global context. 3. Examples of websites are as follows: • The Ministry of Human Resources http://links.andl17.com/ BT_Science_141_1

• ICS • Discussion/ project-based activity

• Impact of bauxite mining in Kuantan, Pahang http://links.andl17. com/BT_Science_141_2

4. Debate on the information gathered. 5. Generate ideas to solve problems of the adverse effects from mining activities that have been poorly planned to life on Earth. 6. Prepare posters for Gallery Walk on efforts to conserve mining areas towards sustainable development. 7. Display three of the best posters on the science bulletin board.

Formative Practice

4.3

1. State the extraction method of the following metals from their ore or metal oxides: (a) Aluminium oxide (b) Iron ore 2. Figure 1 shows a blast furnace used to extract iron. (a) Name one example of a metal other than iron that is extracted using the blast furnace. (b) Name the substance that is added into the blast furnace through the parts labelled: (i) P (ii) Q (c) Name the substance that is tapped off from the blast furnace through the parts labelled: (i) R (ii) S

P

Q S

R

Figure 1

3. State one adverse effect from unplanned mining activities and ways to solve it in the following contexts: (a) Local context (b) Global context

4.3.2

141

142

Summary Variety of minerals in Earth’s crust

extracted in the sector

that is poorly planned will cause

made up of

Mineral elements

Mineral compounds such as classified

Mining

Adverse effects and impact on

Reactivity series of metals

Metal oxides

Life

examples

based on

examples

that needs

Gold, silver

Vigour of reaction of metal towards oxygen

r
Bauxite (aluminium ore) r
Galena (lead ore) r
Hematite (iron ore) r
Cassiterite(tin ore)

Non-metals

Metals

example

Graphite

in

Extracted from metal ore using electrolysis or carbon as the reducing agent in a blast furnace

To be solved using application of creative and innovative ideas and ways

Chapter 4: Reactivity of Metals

Self-reflection After studying this chapter, you are able to: 4.1 Variety of Minerals Explain with examples minerals that are found in Earth’s crust. Identify elements found in natural compounds. Explain with examples the characteristics of natural minerals and its uses in daily life. 4.2 Reactivity Series of Metals Construct a reactivity series of metals based on its reactivity with oxygen and write the word equation for the reactions. Determine the position of carbon and hydrogen in the reactivity series of metals. 4.3 Extraction of Metals from their Ores Communicate the extraction of metals from its ore using illustrations. Generate ideas on how to solve problems from unplanned mining activities to life on Earth.

Summative Practice

4

Answer the following questions: 1. The following are some of the minerals found in Earth’s crust. Iron

Quartz Galena

Silver Tin

Bauxite Hematite

Potassium Limestone

(a) Classify the above minerals into two groups, namely elements and compounds. Minerals in Earth’s crust

Elements

Compounds

143

(b) Give one example of metal ore and name the elements combined in the metal ore. 2. Figure 1 shows tin ore.

Figure 1

(a) What is the systematic name of tin ore? (b) State the substance used to extract tin from tin ore. (c) Write the word equation for the reaction between tin and oxygen. 3. Mark ' ✓' for the correct statements. (a) The number of minerals in Earth’s crust is the same as the number of elements. (b) Aluminium ore is a mineral compound in Earth’s crust. (c) Calcium oxide that is used to reduce the acidity of soil is basic. (d) Carbon is used to form metal ores.

( ( ( (

4. (a) Name the substance that reacts with metals and is used to determine the position of the metals in the reactivity series of metals. (b) Potassium and sodium are kept in dark reagent bottles filled with paraffin oil. Explain why. 5. Figure 2 shows the apparatus set-up of an activity to test the reaction of a metal towards gas X.

Metal powder

Glass wool

Potassium manganate(VII) crystals

Porcelain plate

Heat

Heat

Figure 2

144

) ) ) )

Chapter 4: Reactivity of Metals

(a) (b) (c) (d)

Name gas X. What is the function of potassium manganate(VII) crystals in this activity? Explain the steps of the correct heating procedure in this activity. State the aim of this activity.

6. How can the position of carbon in the reactivity series of metals determine the method of extraction of metals from their ores or metallic compounds?

Focus on HOTS 7. The construction of 3D (three dimensional) models are normally used in various fields. You are required to make a 3D model of a blast furnace using the following materials:

• • • • • • • • • • •

Drinking straw Empty mineral water bottle Water Cooking oil Iron powder Coke Limestone powder Transparent plastic bag Motor Blade of fan Paper clips

Sketch your 3D model and explain.

145

Chapter Chapter Chapte hapte er

5

Thermochemistry

What is thermochemistry? What are endothermic and exothermic reactions? What is the importance of the concept of endothermic and exothermic reactions in daily life?

Let’s study Endothermic and exothermic reactions

146

Science Gallery Every chemical reaction is followed by a change in the form of energy. When chemical reactions occur, chemical energy stored in the reactants is converted to heat energy and released into the surroundings. Thermochemistry is the study of heat changes when chemical reactions occur. There are many applications of thermochemistry in our daily life which include instant hot packs and instant cold packs as shown in the photographs below. Instant hot packs are used to release heat into the surroundings. The heat released by instant hot packs can relieve muscle cramp and increase the size of lumen in the blood capillaries so that the rate of blood circulation through these capillaries is increased.

Instant cold packs are used to absorb heat from the surroundings. The heat absorbed by instant cold packs can reduce the swelling of wounds, get rid of heat from inflamed tissues or body organs and reduce the size of lumen in the blood capillaries so that the rate of blood circulation through these capillaries is reduced and this helps to stop bleeding.

Keywords Thermochemistry Endothermic reaction Exothermic reaction

Thermal equilibrium Heat Temperature

147

5.1

Endothermic and Exothermic Reactions When sodium is added to water, the chemical reaction that occurs is shown in Photograph 5.1. Name three forms of energy that are released in this chemical reaction.

LIM

What form of energy is released or absorbed in most chemical reactions?

Chemical reactions can be divided into two types based on the heat change that occurs during the reactions. These are the exothermic reactions and endothermic reactions.

Photograph 5.1 Reaction between sodium and water

SCIENCE INFO The prefix ‘exo’ originates from the Greek word which means ‘outside’ while the suffix ‘thermic’ originates from the Greek word which means ‘heat’. The prefix ‘endo’ originates from the Greek word which means ‘inside’.

Sir, how can we identify whether the reaction shown in Photograph 5.1 is an exothermic or endothermic reaction? LIM

RIFQI

That’s easy. We only need to detect the change in temperature of the water in the container. If the water in the container becomes hot, the chemical reaction is an exothermic reaction. If the water in the container becomes cold, the chemical reaction is an endothermic reaction.

148

5.1.1

5.1.2

Chapter 5: Thermochemistry Now, I would like to ask a question. Name one measuring device that is suitable for determining exothermic and endothermic reactions. Then, explain your answer.

A thermometer, sir. A rise in the reading of the thermometer shows that heat is released into the surroundings. This is an exothermic reaction. On the contrary, a drop in the reading of the thermometer shows that heat is absorbed from the surroundings. This is an endothermic reaction.

LIM

RIFQI

Very good! Let’s carry out Experiment 5.1 to compare and contrast the exothermic and endothermic reactions. on

Alright, sir. LIM RIFQI LIM

LIM

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LIM

SCIENCE INFO

5.1

Recall the relationship between temperature and heat, and the concept of thermal equilibrium which you have learnt in Form 2.

Experiment 5.1 Aim Compare and contrast the exothermic and endothermic reactions Problem statement What are the similarities and differences between the exothermic and endothermic reactions? Hypothesis An exothermic reaction is a chemical reaction that releases heat into the surroundings while an endothermic reaction is a chemical reaction that absorbs heat from the surroundings. 5.1.2

5.1.3

149

Variables (a) manipulated variable : Type of chemical substance (b) responding variable : Final temperature reading (c) constant variable : Volume of water Materials Sodium hydrogen carbonate powder, sodium hydroxide, ammonium chloride, 0.1M sodium hydroxide solution and 0.1M hydrochloric acid Apparatus Polystyrene cup, thermometer, spatula and measuring cylinder Procedure 1. Measure and pour 50 ml of water into a polystyrene cup. 2. Leave the water in the polystyrene cup for 2 minutes. 3. Record the initial temperature reading of the water in the given table. 4. Add two spatulas of sodium hydroxide into the polystyrene cup and stir the mixture until all the sodium hydroxide dissolves in the water as shown in Figure 5.1. Thermometer

Spatula Sodium hydroxide

Polystyrene cup Water

Figure 5.1 5. 6. 7. 8. 9. 10.

Record the maximum or minimum temperature in the table. Repeat steps 1 to 5 by replacing sodium hydroxide with ammonium chloride. Measure and pour 25 ml of hydrochloric acid into a polystyrene cup. Leave the acid in the polystyrene cup for 2 minutes. Record the initial temperature of the acid in the given table. Measure and pour 25 ml of sodium hydroxide solution into the polystyrene cup and stir the mixture as shown in Figure 5.2. Thermometer Polystyrene cup Sodium hydroxide solution

Polystyrene cup

Hydrochloric acid

Figure 5.2

150

5.1.3

Chapter 5: Thermochemistry

11. Record the maximum or minimum temperature in the table. 12. Repeat steps 7 to 11 by replacing sodium hydroxide solution with 2 spatulas of sodium hydrogen carbonate powder. Observations

Reactants

Sodium hydroxide and water

Ammonium chloride salt and water

Hydrochloric acid and sodium hydroxide solution

Hydrochloric acid and sodium hydrogen carbonate

Temperature before reaction (°C)

Maximum or minimum temperature during reaction (°C)

Type of reaction

Conclusion Is the hypothesis of the experiment accepted? What is the conclusion of this experiment? Questions 1. What is the operational definition for: (a) the release of heat in this experiment? (b) the absorption of heat in this experiment? 2. (a) What happens when the temperature shown on the thermometer is at maximum or minimum? (b) Explain your answer to question 2(a). 3. State the criteria used in this experiment to classify the reaction as: (a) exothermic (b) endothermic 4. List the exothermic reactions in this experiment. 5. List the endothermic reactions in this experiment. 6. (a) How can the accuracy of the maximum or minimum temperature be increased? (b) Explain your answer to question 6(a).

5.1.3

151

Examples of Exothermic and Endothermic Reactions in Daily Life Examples of exothermic and endothermic reactions in daily life are shown in Photograph 5.2.

Fireworks display

Cake baking

Photosynthesis

Respiration

Photograph 5.2 Examples of exothermic and endothermic reactions

Based on Photograph 5.2: • which are exothermic reactions? • which are endothermic reactions?

152

5.1.4

Chapter 5: Thermochemistry

Designing Materials Using the Concept of Exothermic and Endothermic Reactions to Solve Problems in Daily Life Carry out Activity 5.1 to design materials using the concept of exothermic and endothermic reactions to solve problems in daily life.

Activity 5.1 To study engineering designs to solve problems in daily life Instructions 1. Work in groups. 2. Gather information on the engineering design process to: (a) produce materials to relieve muscle cramp

• ICS, CPS, STEM • Project-based learning activity

(b) produce an emergency lamp when there is a power failure

(c) design a container that can maintain high or low temperature

3. Write the information and research results obtained by your group in the form of a folio.

5.1.5

153

Formative Practice

5.1

1. Define the following types of chemical reactions: (a) Endothermic reaction (b) Exothermic reaction 2. What is thermochemistry? 3. Why does our body temperature increase when performing vigorous physical activities? 4. (a) Name one example of a global phenomenon caused by exothermic reaction. (b) Give one solution to the phenomenon mentioned in question 4(a). 5. (a) Name the reaction produced by materials to relieve muscle cramp. (b) Explain your answer.

Summary Thermochemistry is

The study of heat changes that occur when chemical reactions take place where

Heat is released into the surroundings

Heat is absorbed from the surroundings

in

in

Exothermic reactions

Endothermic reactions

in processes such as

in processes such as

Burning of paper, bomb explosion, respiration, neutralisation of acid with alkali

Photosynthesis, cake baking, extraction of iron from iron ore, dissolving ammonium salt in water

which cause

which cause

A rise in temperature

A drop in temperature

in the

in the

Product of reaction

Product of reaction

154

Chapter 5: Thermochemistry

Self-reflection After studying this chapter, you are able to: 5.1 Endothermic and Exothermic Reactions Define endothermic and exothermic reactions. Relate heat absorbed or released in a chemical reaction to endothermic and exothermic reactions. Carry out an experiment to compare and contrast endothermic and exothermic reactions. Explain with examples exothermic and endothermic reactions. Design materials using the concept of exothermic and endothermic processes to solve problems in life.

Summative Practice

5

Answer the following questions: 1. There are two types of reactions: exothermic reaction and endothermic reaction. Match the examples of processes with the correct type of reaction. (a) Burning of petrol (b) Photosynthesis (c) Respiration

Exothermic reaction

(d) Making bread Endothermic reaction (e) Neutralisation (f) Rusting of iron 2. Underline the correct answers. (a) The burning of a candle is an exothermic reaction because heat is (released/absorbed). (b) Exothermic reaction in the body (increases/decreases) the body temperature. (c) Exothermic reaction is applied in instant (cold/hot) packs. (d) Baking a cake is not an exothermic reaction because heat is (released/absorbed).

155

3. Solve the crossword puzzle below. (e) (b)

P

(a)

E

(f)

(d)

E

T

T

R

(c)

M

Across (a) Study of heat change when chemical reactions take place. (b) Endothermic reaction that occurs in plants. (c) Exothermic reaction that occurs in animals.

R

Down (d) A device that measures change in temperature during exothermic and endothermic reactions. (e) Chemical reaction that absorbs heat from the surroundings. (f) Chemical reaction that releases heat into the surroundings. 4. Figure 1 shows an apparatus set up to heat calcium carbonate.

Calcium carbonate

Limewater Retort stand Heat

Figure 1

Is the heating of calcium carbonate an exothermic reaction or an endothermic reaction? Explain your answer. 156

5.1.1

Chapter 5: Thermochemistry

5. Differentiate the reaction between hydrochloric acid and sodium carbonate, and the reaction between hydrochloric acid and sodium hydrogen carbonate. 6. How can the effects of global warming be reduced by the replanting of trees? 7. (a) Figure 2 shows a thermite reaction, that is the heating of iron(II) oxide, aluminium powder and magnesium tape.

Figure 2

Is a thermite reaction an exothermic reaction or endothermic reaction? Explain your answer. (b) Figure 3 shows an application of a thermite reaction.

Figure 3

Describe the application of thermite reaction in Figure 3.

157

Focus on HOTS HOTS 8. Figure 4 shows an instant hot pack and an instant cold pack used in hospitals to relieve muscle cramps and reduce the swelling of wounds.

INSTANT HOT PACK

INSTANT COLD PACK

Press here

Press here

Figure 4

Using your creativity, modify and make an instant hot pack and an instant cold pack using the following materials. Explain.

Two thin plastic bags (size: small) Two thick plastic bags (size: large)

Toothpick Toot Tooth thp pick ick

Ammonium nitrate Calcium chloride

158

terr Water

THEME

3

Energy and Sustainability of Life

Solar cells are used to generate electricity. What is the importance of the generation of electricity using solar energy in Malaysia?

According to the law in Malaysia, the installation of smoke detectors in buildings such as hospitals, hotels, supermarkets and office buildings is compulsory. Smoke detectors normally contain a small amount of radioactive substance. Name this radioactive substance. What is the importance of handling radioactive substances effectively in daily life?

159

Chapter Chapter Chapte hapt apte apt er

1 6

Electricity and Magnetism

What are renewable and non-renewable energy sources? What are the functions of step-up and step-down transformers? How is the cost of electricity consumption calculated?

Let’s study Generation of electricity Transformer Transmission and distribution of electricity Calculating the cost of electricity consumption

160

Science Gallery According to a report from the Malaysian Nuclear Agency, Malaysia needs to have a nuclear power station in 2030. This power station should generate electricity that is sufficient to meet the electricity needs of our country. Do you agree or disagree with having of this power station in Malaysia? Why? (Source:http://www.utusan.com.my/sains-teknologi/inovasi/lojinuklear-negara-beroperasi-2030-1.146680)

MALAYSIA

# #

Where should nuclear power stations be built in our country?

##

RIFQI

Keywords Power station Induced current Direct current Alternating current Primary coil

Secondary coil Input voltage Output voltage National Grid Network Earth wire

Short circuit Electric shock Kilowatt-hour (kWh) Energy efficiency

161

6.1

Generation of Electricity

Various Energy Sources to Generate Electricity Did you know that our country, Malaysia is a country which is very successful in using various energy sources to generate electricity? What are the energy sources used in Malaysia to generate electricity? Electricity is generated through various energy sources. These different energy sources can be classified into two main groups, namely renewable energy sources and nonrenewable energy sources as shown in Figure 6.1. Figure 6.2 shows renewable and non-renewable energy sources used in power stations in Malaysia.

My Malaysia M Malaysia is currently the leading country in biomass industry in the Southeast Asian region. Sarawak and Sabah are two states in Malaysia that have a variety and a large amount of biomass. The variety of biomass includes the biomass of oil palm, forests, rubber trees, garbage, rice husks and maize. Besides the generation of electricity, biomass is also used to produce innovative products such as building materials.

Energy sources

Renewable energy sources

Non-renewable energy sources

Definition

Definition

Energy sources that can be replaced continually and will never deplete.

Energy sources that cannot be replaced and will deplete.

Examples t

Hydro energy t

Wave energy t

Solar energy t

Tidal energy t

Wind energy t

Biomass energy t

Geothermal energy

Examples

Hybrid power station in Pulau Perhentian Kecil, Terengganu (Energy source: Wind, Solar, Diesel)

t

Nuclear energy t

Coal t

Natural gas t

Petroleum

Figure 6.1 Renewable and non-renewable energy sources

162

6.1.1

Chapter 6: Electricity and Magnetism

Bakun hydroelectric power station in Sarawak (Energy source: Hydro energy) Tuanku Jaafar power station in Negeri Sembilan (Energy source: Natural gas)

Power stations in Malaysia Sultan Azlan Shah power station in Manjung, Perak (Energy source: Coal)

Gelugor power station in Pulau Pinang (Energy source: Diesel) TSH Bio-Energy Sdn. Bhd. Biomass power station in Sabah (Energy source: Biomass)

Figure 6.2 Power stations in Malaysia that use renewable and non-renewable energy sources 6.1.1

163

Process of Generating Electricity A generator is a device used to generate electricity. Look at Photograph 6.1 which shows an example of a generator model. Magnet

Name two main components that generate current in this generator model.

Coil of wire Crank

Magnet LED

RIFQI

Photograph 6.1 Generator model

40 50

0

10

20

10

20

50

50

40

G

–

+

8

Solenoid is moved 6

Connecting wire is moved

Figure 6.3

Figure 6.4

Galvanometer

Galvanometer meter 10

0

10

G

50

30

40

0

G

–

–

10

20

8

50

50

10

+

Solenoid 6

1

Magnet is moved

Connecting wire

Figure 6.5

20

Figure 6.6 6.1.2

50

20

40

4 40

30

20

30

Magnet is moved 40

164

Magnet

1

30

• Movement of the magnet which causes the magnetic field lines to be cut. A magnet is moved as shown in Figures 6.5 and 6.6 so that the magnetic field lines are cut by the connecting wire or solenoid. An induced current is produced in the connecting wire or solenoid, and it flows through the galvanometer. The pointer in the galvanometer deflects.

+

Galvanometer meter 30

50

• Movement of the wire which causes the magnetic field lines to be cut. A connecting wire or solenoid is moved rapidly through the space between the magnetic poles as shown in Figures 6.3 and 6.4. An induced current is produced in the connecting wire or solenoid, and it flows through the galvanometer. The pointer in the galvanometer deflects.

20

40

G

–

6

30

30

10

30

10

20

0

40

When the crank of the generator model is turned, a current known as induced current is produced. The flow of this induced current lights up the LED. In 1831, a scientist named Michael Faraday conducted a series of investigations on the generation of electricity using Galvanometer a magnetic field. Electric current is produced by:

+

Chapter 6: Electricity and Magnetism

Activity 6.1

Inquiry-based activity

To study the production of electric current when magnetic field lines are cut by a copper wire Materials PVC insulated copper wire, connecting wire and cardboard tube with a coil of PVC insulated copper wire (coil of wire/solenoid) Apparatus Bar magnet, U-shaped magnet and centre-zero galvanometer Instructions 1. Connect the PVC insulated copper wire to the centre-zero galvanometer. 2. Move the copper wire downwards between the north and south poles of a U-shaped magnet and then upwards as shown in Figure 6.3. Observe and record the deflection of the galvanometer pointer. 3. Move the U-shaped magnet upwards and then downwards as shown in Figure 6.5. Observe and record the deflection of the galvanometer pointer. 4. Connect the coil of PVC insulated copper wire to the centre-zero galvanometer. 5. Move the coil of wire as shown in Figure 6.4. Observe and record the deflection of the galvanometer pointer. 6. Move the bar magnet as shown in Figure 6.6. Observe and record the deflection of the galvanometer pointer. Observations Step

Deflection of galvanometer pointer

2 3 5 6 Questions 1. What is detected by the galvanometer when the galvanometer pointer deflects? 2. What happens when a magnet moves relative to a copper wire or coil of copper wire? 3. What is produced by the cutting of the magnetic field lines by a copper wire or coil of copper wire?

6.1.2

165

Activity 6.2 To build a simple generator that can light up an LED using magnets and a coil of wire

• ICS, ISS, STEM • Innovationbased activity

Materials PVC insulated copper wire, cellophane tape, connecting wires with crocodile clips and LED Apparatus Armature with axle, two magnadur magnets, wooden plank (base) and C-shaped magnet holder Instructions 1. Work in groups. 2. Construct a simple direct current (d.c.) generator as shown in Figure 6.7. 3. Make sure the axle is stationary. Observe and record if the LED lights up. 4. Rotate the axle. Then, observe and record if the LED lights up. 5. Present your findings. Observation Condition of axle

Cellophane tape to keep commutator in position

Rotating

1

6

Commutator

Carbon brush LED

Ends of the coil of wire to build commutator Magnadur magnet

LED

Stationary

Magnadur magnet

Coil of wire

N

Axle

Rotated

S

LED Figure 6.7 Simple d.c. generator Questions 1. Mark ' ✓ ' for the true statement related to the cutting of magnetic field lines. (a) When the coil of wire and magnet are stationary, the magnetic field lines are cut. (b) When the coil of wire moves inside the stationary magnet, the magnetic field lines are cut. (c) Current will only be induced when the magnetic field lines are cut. 2. 3. 4. 5.

166

How is induced current detected in this activity? How is induced current produced by the d.c. generator? State two forms of energy other than electrical energy produced in this activity. State two advantages of LED as a lighting device compared to a filament bulb.

6.1.2

Chapter 6: Electricity and Magnetism

Electricity Generated at Power Stations Study Figures 6.8 to 6.13. Observe how electricity is generated at power stations using various sources of energy. Power station using non-renewable energy sources such as diesel, natural gas and coal.

1

Boiler

Generator Steam

Transmission tower Turbine

SCIENCE INFO Seawater Fuel

Condenser

Figure 6.8 Thermal power station

A pylon is a tall metal structure to which transmission cables carrying electricity are fixed so that they are safely held high above the ground.

Mechanism Burning of fuel

Boiling water produces steam

Steam rotates the turbine

Generator produces electricity

Energy Change Chemical energy

2

Heat energy

Kinetic energy

Power station using solar energy.

Electrical energy

Solar panel

Mechanism Sunrays

Solar panels convert light energy from the Sun into electricity

Energy Change Solar energy

6.1.2

Electrical energy

Figure 6.9 Power station using solar energy

167

3

Hydroelectric power station. Water reservoir

Power tunnel Generator Transmission tower

Turbine Water flows into river

Figure 6.10 Hydroelectric power station Mechanism High dam stores water

Water flows from high level to low level

Generator produces electricity

Flow of water rotates turbine

Energy Change Gravitational potential energy

4

Kinetic energy

Power station using wind energy.

Electrical energy

Blade Generator

Tower Base

Figure 6.11 Power station using wind energy Mechanism Moving air or wind

Wind moves blades

Blades rotate turbine

Generator produces electricity

Energy Change Kinetic energy

168

Electrical energy

6.1.2

Chapter 6: Electricity and Magnetism

5

Power station using nuclear fuel.

Steam

Uranium

Generator

Pump

Transmission tower

Turbine Nuclear reactor

Pump

Seawater Condenser

Water

Figure 6.12 Nuclear power station Mechanism Nuclear reaction

Boiling water produces steam

Generator produces electricity

Steam rotates the turbine

Energy Change Nuclear energy

6

Power station using biomass.

Heat energy

Kinetic energy

Steam

Electrical energy

Turbine Generator

Boiler Water

Transmission tower

Burning of methane Pump

Seawater

Methane Water

Condenser

Biomass

Figure 6.13 Biomass power station Mechanism Biomass produces methane

Boiling water produces steam

Steam rotates the turbine

Generator produces electricity

Energy Change Chemical energy

6.1.2

Heat energy

Kinetic energy

Electrical energy

169

Activity 6.3 To gather information and understand how electricity is generated at power stations

• ICS, ISS, STEM • Discussion activity

Instructions 1. Work in groups. 2. Gather information on how electricity is generated at power stations using various sources of energy as shown in Figures 6.8 to 6.13: (a) Process of generating electricity from various sources of energy (b) Locations of power stations which use various sources of energy in Malaysia 3. Share the findings of your group discussion in class.

Direct Current and Alternating Current Do you still remember the topic of electric current in Form 2?

Do electric charges flow through a conductor in one direction only or in constantly changing directions?

AIN

Electric current is divided into two types, direct current (d.c.) and alternating current (a.c.). Direct Current (d.c.) Direct current is an electric current that flows in one direction only. Examples of devices that use direct current are shown in Photograph 6.2.

(a) Torchlight

(b) Calculator

((c)) T Toy car

Photograph 6.2 Examples of devices that use direct current

Examples of generators or sources of electricity that produce direct current are shown in Photograph 6.3.

(a) Solar cells

(b) Accumulators

(c) Batteries

Photograph 6.3 Examples of generators or sources of electricity that produce direct current

170

6.1.2

6.1.3

Chapter 6: Electricity and Magnetism

Alternating Current (a.c.) Alternating current is an electric current that flows in constantly reversing directions. Look at Photograph 6.4 which shows examples of devices that use alternating current.

(a) Bread toaster

(b) Hair dryer

(c) Air conditioner

Photograph 6.4 Examples of devices that use alternating current

Do most of the electricity generators in power stations produce d.c. or a.c.?

,

5 *(

.

Cathode Ray Oscilloscope (C.R.O.) is an electronic device that is used to show the differences in the shape of graph, direction of current and voltage change for direct current and alternating current. For this, you are encouraged to gather information on how to handle several control switches on the C.R.O. before carrying out Activity 6.4. For this purpose, observe Photograph 6.5.

:

Cathode Ray Oscilloscope (C.R.O.)

     7(

Y-gain Knob To change the magnitude of the height of the light spot

Intensity Control Knob

Y-shift Knob To adjust the position of the light spot vertically

To control the brightness of the light spot on the C.R.O. screen

Focus Control Knob

X-shift Knob To adjust the position of the light spot horizontally

To control the sharpness of the light spot on the C.R.O. screen

Time-base Knob

Direct Current/ Alternating Current Switch Selected according to the type of input received

To control the movement of the light spot which sweeps across the C.R.O. screen horizontally

Photograph 6.5 Switches and control knobs on the C.R.O. 6.1.3

171

Activity 6.4

Inquiry-based activity

Using a Cathode Ray Oscilloscope (C.R.O.) to show the differences in the shape of graph, direction of current and voltage change for direct current (d.c.) and alternating current (a.c.) Material Dry cell Apparatus Connecting wire, cell holder, C.R.O. and power source Instructions 1. Switch on the C.R.O. and wait for a light spot to appear on the screen. Turn off the time-base knob. Turn the intensity control and focus control knobs to adjust the brightness and sharpness of the light spot shown in Figure 6.14. 2. Use the X-shift and Y-shift knobs to adjust the light spot so that it is at the zero position in the centre of the screen as shown in Figure 6.14. 3. Turn on the time-base knob and observe the trace displayed on the screen as shown in Figure 6.15.

Figure 6.14

Figure 6.15

4. Select the input switch to d.c. and adjust the Y-gain knob to 1 V/division. Turn off the time-base knob. 5. Connect a dry cell to the Y-input (Photograph 6.6).

C.R.O. Dry cell

Y-input

Photograph 6.6

172

6.1.3

Chapter 6: Electricity and Magnetism

6. Observe and record the trace displayed on the screen shown in Figure 6.16. Determine the voltage across the dry cell by multiplying the displacement with the value of Y-gain. 7. Turn on the time-base knob. Observe and record the trace displayed on the screen as shown in Figure 6.17.

Figure 6.16

Figure 6.17

8. Repeat steps 5 to 7 but reverse the connection of the dry cell terminals. Observe and record the trace displayed on the screen shown in Figure 6.18. 9. Turn on the time-base knob. Observe and record the trace displayed on the screen as shown in Figure 6.19.

Figure 6.18 10. Select the input switch to a.c. and adjust the Y-gain knob to 1 V/division. Turn off the time-base knob. 11. Connect a 2 V a.c. terminal from the power supply to the Y-input as shown in Photograph 6.7. 12. Observe and record the trace displayed on the screen as shown in Figure 6.20.

Figure 6.19 Power supply

C.R.O.

Y-input

Photograph 6.7

6.1.3

173

13. Turn on the time-base knob. Observe and record the trace displayed on the screen as shown in Figure 6.21.

Figure 6.20

Figure 6.21

14. Repeat steps 10 to 13 but reverse the connection of the terminals of the power supply. Observe and record the trace displayed on the screen as shown in Figure 6.22. 15. Turn on the time-base knob. Observe and record the trace displayed on the screen as shown in Figure 6.23.

Figure 6.22

Figure 6.23

Observations Step

Trace observed on the screen

6 7 8 9 12 13 14 15

174

6.1.3

Chapter 6: Electricity and Magnetism

Questions 1. What is the function of the C.R.O. in this activity? 2. Compare and contrast the traces displayed on the screen as shown in steps 6 and 8. 3. What two inferences can be made based on your observations of the trace displayed on the screen in steps 7 and 9? (a) First inference (b) Second inference 4. Based on your observations of the trace displayed on the screen in steps 12 and 14, describe the change in voltage produced by the power supply. Explain your answer. 5. What are two inferences that can be made based on your observations of the trace displayed on the screen in steps 13 and 15? (a) First inference (b) Second inference 6. Name the type of electric current supplied by the following energy sources: (a) Dry cell (b) Power supply

Solving Problems Related to Electricity Supply in Life Have you ever experienced disruptions of electricity supply while at home or in school? If disruptions of electricity supply is a big problem in your life, can you imagine the lives of people living in rural areas without any electricity supply? Let us carry out Activity 6.5 to make a model of a generator that can produce electricity.

My Malaysia M ‘Giant’ generators known as gensets from TNB are used to provide backup supply of electricity during disruptions.

Activity 6.5 To create or innovate a model for generating electricity using turbines and generators in rural areas without affecting the environment

• ICS, CPS • Project-based activity

Instructions 1. Work in groups. 2. Create or innovate a model for generating electricity using turbines and generators in rural areas without affecting the environment.

6.1.3

6.1.4

175

Examples of innovations to generate electricity.

Wireless electrical transmission and distribution

Roof with solar cells

Absorbs and changes solar energy to electrical energy without affecting the environment

Changes electrical energy to radio wave or microwave energy to be transmitted and distributed without wires to electrical devices. These electrical devices then change the radio wave or microwave energy back to electrical energy.

rbines and generators to generate electricity 3. Present your model or innovation using turbines electricity.

Formative Practice

6.1

1. What is meant by renewable energy sources and non-renewable energy sources? 2. Figure 1 shows three arrangements, P, Q and R with moving or stationary magnet and coil of wire. Coil remains stationary U

Coil moves towards the magnet U

S

LED

Arrangement P

U

S

LED Magnet moves towards the coil

Coil remains stationary S

LED Magnet remains stationary

Arrangement Q

Magnet remains stationary

Arrangement R

Figure 1

(a) In which arrangement does the LED light up? Explain your answer. (b) In which arrangement does the LED not light up? Explain your answer. 3. What is the function of a cathode ray oscilloscope or C.R.O.? 176

6.1.4

Chapter 6: Electricity and Magnetism

6.2

Transformer Have you ever seen the device shown in Photograph 6.8 in the area where you live? What is the importance of this structure in daily life?

ADAM

Photograph 6.8 Transformer

Step-up Transformer and Step-down Transformer A transformer is a device for changing the voltage of an alternating current (Va.c.). A simple transformer is made up of laminated soft iron core which is wrapped by two insulated coils, the primary coil and the secondary coil as shown in Figure 6.24.

Laminated soft iron core

Load

a.c. supply

Primary coil

Secondary coil

Figure 6.24 Structure of a simple transformer

There are two types of transformers, the step-up transformer and the step-down transformer as described in Table 6.1. 6.2.1

177

Table 6.1 Step-up transformer and step-down transformer Step-up transformer Primary coil

Step-down transformer Secondary coil

Primary coil

Secondary coil

Load a.c. supply

Load a.c. supply

Symbol

Symbol

Primary voltage (input), Vp, across the primary coil is lower than the secondary voltage (output), Vs, across the secondary coil.

Primary voltage (input), Vp, across the primary coil is higher than the secondary voltage (output), Vs, across the secondary coil.

Number of turns of the primary coil is less than that in the secondary coil.

Number of turns of the primary coil is more than that in the secondary coil.

Carry out Experiment 6.1 to construct and study the functions of simple step-up and step-down transformers.

Experiment 6.1 Aim To construct and study the functions of simple step-up and step-down transformers using laminated soft iron core Problem statement What are the functions of step-up and step-down transformers? Hypothesis (a) In a step-up transformer, the secondary voltage (output) is higher than the primary voltage (input). (b) In a step-down transformer, the secondary voltage (output) is lower than the primary voltage (input). Variables (a) manipulated variable : Number of turns of the secondary coil, Ns (b) responding variable : Brightness of light bulb (c) constant variable : Number of turns of the primary coil, Np Materials Connecting wire, insulated copper wire and light bulbs Apparatus a.c. power supply and laminated C-shaped soft iron core

178

6.2.1

Chapter 6: Electricity and Magnetism

Procedure 1. Wind 30 turns of wire around one arm of the Safety laminated soft iron core to form a primary coil as Precaution shown in Figure 6.25. Practise safety steps while 2. Wind 15 turns of wire around the other arm of the handling power supply. laminated soft iron core to form a secondary coil as shown in Figure 6.25. 3. Connect the primary coil to an a.c. power supply. Then, connect light bulb P to the primary coil and light bulb S to the secondary coil as shown in Figure 6.25. a.c. power supply

INPUT : 220/240V A.C.50/60Hz

OUTPUT; Max 12V AC/DC

ST909T

0FF

7

6

D.C. TOTAL 8 AMP. 0N

LOAD MAX.

A.C.

8 9

5

0

4 3

11 2

VOLTS

Primary coil (30 turns) P Laminated C-shaped soft iron core

Secondary coil (15 turns) S

Figure 6.25 4. Switch on the a.c. power supply and adjust its voltage to 2 V. 5. Observe and compare the brightness of the two bulbs. 6. Repeat steps 3 to 5 but using a primary coil with 30 turns and a secondary coil with 60 turns. Observations Number of turns of primary coil, Np

Number of turns of secondary coil, Ns

30

15

30

60

Brightness of bulb P

S

Conclusion Is the hypothesis of the experiment accepted? What is the conclusion of this experiment?

6.2.1

179

Questions 1. Based on the results of this experiment: (a) What is the effect on the brightness of the bulb if Np > Ns? (b) What is the relationship between Vp and Vs if Np > Ns? (c) What type of transformer is this? 2. Based on the results of this experiment: (a) What is the effect on the brightness of the bulb if Np < Ns? (b) What is the relationship between Vp and Vs if Np < Ns? (c) What type of transformer is this? 3. What happens to the change in voltage of the alternating current in a transformer if the difference between the number of turns in its primary coil and the number of turns in its secondary coil is increased? 4. Why are the numbers of turns in the primary and secondary coils different in all transformers?

Function of Transformer in Home Electrical Appliances In Malaysia, the supply voltage of alternating current provided to our home is 240 V. Give one example of an electrical appliance at home that operates at 240 V alternating current without using a transformer. Most electrical appliances at home use transformers such as those in mobile phone chargers (Photograph 6.9).

SCIENCE INFO An induced current formed in the iron core of a transformer is known as the eddy current. The formation of the eddy current in a transformer will reduce the efficiency of the transformer. Due to this, a laminated iron core is used to reduce eddy current and increase the efficiency of the transformer. A laminated iron core is made up of layers of soft iron and layers of insulators arranged alternately.

Transformer

Photograph 6.9 A mobile phone charger

Laminated iron core

Is the transformer in a mobile phone charger a step-up or step-down transformer? Let us carry out Activity 6.6 to discuss the transformers and their functions in home electrical appliances. 180

6.2.1

6.2.2

Chapter 6: Electricity and Magnetism

Activity 6.6 To discuss the transformer and its functions in home electrical appliances

• ICS • Technologybased activity

Instructions 1. Work in groups. 2. Use various sources to gather information on transformers and their functions in home electrical appliances. Examples of the use of transformers in home electrical appliances

(a) Battery charger of a laptop

(b) Mobile phone charger

(c) Ceiling fan regulator

3. Discuss the gathered information. 4. Present the outcome of the discussion using multimedia presentation.

Solving Problems Related to Transformers in Daily Life Figure 6.26 shows an example of a home electrical appliance which is a ceiling fan regulator that uses a step-down transformer. What is the formula used to determine the number of turns in the secondary coil to lower the input voltage from 240 V to voltages ranging from 2 V to 10 V? Step-down transformer mer

1

2

240 V a.c.

3

0

4 5

5

0V 2V 4V 6V 8V 10 V

0

4 3

2

1

Figure 6.26 Ceiling fan regulator 6.2.2

6.2.3

181

Transformer Equation The ratio of the primary voltage to the secondary voltage is equal to the ratio of the number of turns of the primary coil to the number of turns of the secondary coil in a transformer. This relationship can be written in the following formula: Vp Np = Vs Ns

where

Vp = input voltage of the primary coil or primary voltage Vs = output voltage of the secondary coil or secondary voltage Np = number of turns of primary coil Ns = number of turns of secondary coil

Example Figure 6.27 shows a 40 V bulb connected to a 240 V power supply through a transformer.

240 V

Ns

Np = 120

40 V

Figure 6.27

Find out the number of turns of the secondary coil, Ns, that is required for the bulb to light up at normal brightness?

Solution The bulb will light up at normal brightness if it is supplied with a voltage of 40 V. • Output voltage, Vs = 40 V • Input voltage, Vp = 240 V • Number of turns in primary coil, Np = 120 Vp Np = Vs Ns 240 120 = 40 Ns 40 Ns = 120 × 240 = 20 Number of turns in secondary coil, Ns = 20 182

6.2.3

Chapter 6: Electricity and Magnetism

Formative Practice

6.2

1. What is a transformer? 2. Underline the correct answers. (a) Transformers only function using (direct/alternating) current. (b) In a step-down transformer, the number of turns in the primary coil is (more/less) than the number of turns in the secondary coil. (c) A (step-up/step-down) transformer is used to change 25 kV to 250 kV. (d) A (step-up/step-down) transformer is fixed in a radio. 3. State one example of a home electrical appliance which uses the following types of transformers: (a) Step-up transformer (b) Step-down transformer 4. Figure 1(a) shows a transformer in a 5 V mobile phone charger connected to the 240 V main power supply.

Transformer

Figure 1(a)

Figure 1(b) shows a circuit diagram of the transformer in the mobile phone charger.

240 V

Np

Ns = 10

5V

Mobile phone

Figure 1(b)

(a) Calculate the number of turns in the primary coil. (b) Is the transformer in the mobile phone charger a step-up or step-down transformer? Explain your answer.

183

6.3

Transmission and Distribution of Electricity

Functions of the Components in the Electricity Transmission and Distribution System The electricity transmission and distribution system that connects a power station to your house is shown in Figure 6.28. Alternating current from the power stations is then transmitted to a step-up transformer station (Bn). Here, the voltage of the alternating current is increased to 132 kV, 275 kV or 500 kV using a step-up transformer.

Generators at power stations produce alternating current with a voltage of 11 kV or 25 kV.

$ 132 kV/ 275 kV/ 500 kV

11 kV/ 25 kV

$

%Q

( %W 240 V

House

415 V

415 V

Office KEY: A – Power station Bn – Step-up transformer station Bt – Step-down transformer station

33 kV

Hospital C D E1 E2

– – – –

National Grid Network Switch zone Main substation Branch substation

Figure 6.28 Electricity transmission and distribution system

184

6.3.1

Chapter 6: Electricity and Magnetism

The high voltage alternating current is then transmitted through a network of transmission cables called the National Grid Network (C) as shown in the photographs below.

500 kV alternating current transmission cables along the North-South Highway.

132 kV alternating current transmission cables at the Tanjung Kling Power Station, Malacca

Transmission through long distances At the end of the grid, the alternating current flows to a switch zone (D) at the main substation (E1). This switch zone enables electricity to be sent to the branch substation (E2) when needed. This switch zone is also used to enable specific power stations and grids to be closed for maintenance works without disrupting the electricity supply to consumers.

&

( ' %W 33 kV

Heavy industrial area

33 kV

Switch zone

11 kV

( %W Light industrial area

6.3.1

Main substation

At the main substation (E1) and branch substation (E2), the alternating current is transmitted through a series of step-down transformers (Bt) at the step-down transformer station. The voltage of the alternating current is reduced gradually to different voltage values to be supplied to consumers according to their needs. For example: t

IFBWZ
JOEVTUSJBM
BSFB
BU
33 kV t

MJHIU
JOEVTUSJBM
BSFB
BU
11 kV t

PGmDF
CVTJOFTT
BOE
SFTJEFOUJBM
BSFBT
BU
240 V

185

Impact on Residences Located Near the National Grid Network Pylons High voltage alternating current is transmitted through transmission cables on the National Grid Network pylons as shown in Photograph 6.10. A strong electromagnetic field is produced by the high voltage alternating current and can be detected in the surrounding areas close to the pylons. Observe the effect of this electromagnetic field by using a compass. What happens to the position of the compass needle?

My Malaysia M Go to the following websites: https://www.tnb.com.my/ https://www.sesb.com.my/ http://www.sarawakenergy.com.my/ What are the facilities provided by Tenaga Nasional Berhad (TNB), Sabah Electricity Sdn. Bhd. (SESB) and Sarawak Energy Berhad (Sarawak Energy) to consumers in Malaysia?

Photograph 6.10 Transmission cables on the National Grid Network pylons

Let us carry out Activity 6.7 to discuss the impact of the National Grid Network pylons on nearby residences.

Activity 6.7 To discuss the impact of the National Grid Network pylons on nearby residences Instructions 1. Work in groups. 2. Gather information related to the issues of the impact on residences located near the National Grid Network pylons as follows: (a) Strength of electromagnetic field close to the National Grid Network pylons (b) The impact of electromagnetic field on human health perceived by locals and confirmed by medical experts (c) Ways to solve the issues regarding the electromagnetic field on residential areas close to the National Grid Network pylons 3. Share the outcome of your group discussion in class.

186

• ICS, CPS • Discussion activity

Photograph 6.11 Residences located near a National Grid Network pylon

6.3.1

Chapter 6: Electricity and Magnetism

Electrical Wiring System in Malaysia The electrical wiring system in Malaysia consists of two different types, one-phase wiring (or single-phase) and three-phase wiring as shown in Figures 6.29 and 6.30.

Phase 1

P

BRAIN TEASER Tenaga Nasional Berhad (TNB) suggests that users of singlephase wiring who use more than 10 kW or 50 A to switch to three-phase wiring. Compare and contrast the importance of single-phase wiring and threephase wiring in electricity usage. Does your family accept TNB's suggestion? Give your reasons.

P P: Peak

One cycle

Websites

The single-phase wiring is only suitable and stable enough for electricity usage not exceeding 10 kW or 50 A, such as in rural residential areas.

Ways to identify the types of electrical wiring

Figure 6.29 Single-phase wiring

Phase 1

Phase 2

http://links.andl17.com/BT_ Science _187

Phase 3

P

P

P

P

P One cycle

P

P: Peak

In commercial and industrial areas where electricity usage is more than 10 kW or 50 A, the three-phase wiring which is more stable and reliable is used. Figure 6.30 Three-phase wiring 6.3.2

187

Electricity Supply and Wiring System in Homes Figure 6.31 shows an example of electricity supply and wiring system in homes.

Electric wires from the main cable that are connected to homes are made up of: t
-JWF
XJSF
BU

7 t
/FVUSBM
XJSF
BU

7

Neutral wire

Live wire

Main fuse box with one main fuse

Electric meter t
.FBTVSFT
UIF
UPUBM
VOJUT
PG
electricity used Main switch t
$POUSPMT
UIF
UPUBM
DVSSFOU
nPXJOH
through the circuit in the house

Consumer unit and fuse box

&BSUI
-FBLBHF
$JSDVJU
#SFBLFS
&-$#

t
#SFBLT
UIF
DJSDVJU
XIFO
UPP
NVDI
DVSSFOU
nPXT
UISPVHI
JU

Miniature Circuit Breaker (MCB) t
4FQBSBUFT
UIF
mOBM
DJSDVJU
UP
different electrical appliances

5A

15 A Heating circuit 30 A

KEY:



Air conditioning circuit

-JWF
XJSF /FVUSBM
XJSF Earth wire

30 A

Earth wire

Photograph 6.12 Earthing earth wire

188

6.3.2

Chapter 6: Electricity and Magnetism

-JHIUJOH
DJSDVJU
JT
NBEF
VQ
PG
MJWF
XJSF
BOE
OFVUSBM
wire.

Lighting circuit Power circuit is made up PG
MJWF
XJSF
OFVUSBM
XJSF
and earth wire.

Two way switch

Socket

Socket

Socket

Figure 6.31 Example of electricity supply and wiring system in homes

6.3.2

189

3-pin Plugs and 2-pin Plugs Compare and contrast the structures of the 3-pin plugs and 2-pin plugs shown in Photograph 6.13.

Hong Kong

India

North America

Japan

Europe

Photograph 6.13 3-pin plugs and 2-pin plugs used in different countries

The 3-pin plug and 2-pin plug used in our country are explained in Table 6.2. Table 6.2 3-pin plug and 2-pin plug in the wiring system in homes 3-pin plug

2-pin plug

Electrical appliances such as electric kettles and irons obtain electricity from the sockets on the walls through 3-pin plugs.

Electrical appliances such as hair dryers and electric toothbrushes obtain electricity from the sockets on the walls through 2-pin plugs.

The live wire, neutral wire and earth wire connected to 2-pin and 3-pin plugs are required to follow the international colour code for wiring shown in Figure 6.32 to ensure the safety of electricity use.

Earth wire (yellow and green stripes) 13 A

Neutral wire (blue)

Fuse Live wire (brown)

Figure 6.32 International colour code for wiring

190

6.3.2

Chapter 6: Electricity and Magnetism

Safety Components in the Wiring System in Homes In the wiring system in homes, some of the safety components are shown in Photograph 6.14.

(a) Switch

(d) Miniature circuit breaker (MCB)

(b) 3 A, 5 A, 10 A and 13 A fuses

(c) Earth Leakage Circuit Breaker (ELCB)

(e) Earth wire

(f) Lightning conductor

Photograph 6.14 Safety components in the wiring system in homes

Structure of Fuse A fuse, as shown in Figure 6.33, is a fine and short wire that heats up easily and melts when the current flowing through it exceeds the value of the fuse. If the wire of the fuse melts, the electricity supply will be cut off.

Filled with nitrogen or quartz particles Fuse wire Metal contact cap

$

Fuse

Value of fuse

Glass or porcelain casing

Figure 6.33 Structure of a fuse 6.3.2

6.3.3

191

Cartridge Fuse and Replaceable Wire Fuse The two types of fuses usually used are cartridge fuse and replaceable wire fuse (fuse installed with a fuse wire) as shown in Figure 6.34. Glass casing

Metal cap

(a) Cartridge fuse

Fuse wire

(b) Replaceable wire fuse

Figure 6.34 Two types of fuses

All fuses including cartridge fuses and replaceable wire fuses function as electrical safety devices in circuits or electrical appliances to protect the wires and appliances from any excessive current flow.

Determining the Value of a Fuse The value of a fuse is the maximum value of current that can flow through the fuse without causing its fuse wire to melt. For example, a 5 A fuse wire allows a maximum current of 5 A to flow through it. Some common fuse ratings are 1 A, 2 A, 3 A, 5 A, 10 A, 13 A, 15 A and 30 A. Choosing the value of a fuse depends on the value of the maximum current that flows through a circuit or electrical appliance. The fuse to be used should have a value which is slightly higher than the maximum current that flows through a circuit or electrical appliance in normal operating conditions. For example, an electric kettle that uses a maximum electric current of 11.34 A should be installed with a 13 A fuse.

What is the maximum current that can flow through a 3-pin plug installed with a 13 A fuse?

RIFQI

BRAIN TEASER Why is an electric kettle fixed with a 3-pin plug that has a 13 A fuse?

Activity 6.8 To discuss the safety components in the wiring system in homes

• ICS • Discussion activity

Instructions 1. Work in groups. 2. Identify and discuss the following: (a) Functions, types and values of fuses (b) Function of an earth wire (c) Function of circuit breakers, namely Miniature Circuit Breaker (MCB) and Earth Leakage Circuit Breaker (ELCB) (d) Lightning conductor and switch 3. Use various sources to gather the required information. 4. Present the outcome of the discussion using multimedia presentation.

192

6.3.3

Chapter 6: Electricity and Magnetism

Safety in the Use of Electrical Appliances

Live wire

E

Earth wire

13 A

When using electrical appliances, safety measures should be prioritised. This is because the ratio of deaths due to injury from electrical accidents is high compared to other categories of accidents. Failure to adhere to safety measures will result in serious accidents. One of the safety measures in the use of electrical appliances is shown in Figure 6.35. When an individual touches the metal part that has been earthed, a large current flows to Earth through the earth wire and not through the individual. This large current also melts the fuse which then cuts off the electric circuit. Let us carry out Activity 6.9 to learn more about safety in the transmission and distribution system of electricity and the use of electrical appliances.

N

Neutral wire

The earth wire is connected to the metal casing of the electric iron

Metal casing

Heating element

Figure 6.35 The earth wire connects the metal casing to Earth

Activity 6.9 To create brochures or posters on safety and electrical accidents

• ICS • Project-based activity

Instructions 1. Work in groups. 2. Gather information from various sources regarding the following: (a) Causes of short circuits (b) Causes of electrical accidents (c) Safety measures when using electrical appliances (d) Steps to be taken when an electric shock occurs 3. Discuss the information gathered. 4. Create brochures or posters on the above matters. 5. Display the brochures or posters created on the science bulletin board in your class or science laboratory.

6.3.4

193

Formative Practice

6.3

1. In a science class, Wazir learnt about the components in an electricity transmission and distribution system. Step-up transformer station

Step-down transformer station

Switch zone

Using the words given above, complete the following flowchart. This flowchart shows the sequence of the components in the electricity transmission and distribution system. Power station

(c) Branch substation

(a)

National Grid Network

(b)

Main substation

Step-down transformer

2. Underline the correct answers. (a) The voltage of the alternating current is (increased/decreased) before it is transmitted through the National Grid Network. (b) The voltage of the alternating current is highest at the (power station/National Grid Network/branch substation). (c) The (Switch zone/National Grid Network) enables electricity to be transmitted to the branch substation when needed. 3. (a) State three safety components in the wiring system in homes. (b) What is the function of a fuse? 4. (a) State one example of the cause of a short circuit. Explain your answer. (b) Figure 1 shows several electrical appliances with their respective 2-pin plugs connected to a socket. (i) State the electrical condition as shown in Figure 1. (ii) Give one example of an electrical accident that might occur. Explain your answer.

Figure 1

194

Chapter 6: Electricity and Magnetism

6.4

Calculate the Cost of Electricity Consumption Photograph 6.15 shows electric bulbs connected to a 240 V electrical supply which light up with different brightness. The power of each bulb is as labelled. ADNAN

10 W

20 W

100 W

100 W

Which bulb has the highest efficiency? Explain your answer.

Photograph 6.15 Electric bulbs that light up with different brightness

Energy Efficiency Energy efficiency is the percentage of energy input converted to useful form of energy output. Energy efficiency can be defined as follows: Energy efficiency =

Useful energy output × 100% Energy input supplied

BRAIN TEASER Do you agree that the use of filament bulbs should be banned in Malaysia? Explain your reasons.

Example Photograph 6.16 shows a lighted filament bulb. What is the energy efficiency of the bulb?

8 J of useful energy output in the form of light 100 J of input electrical energy supplied

92 J of energy output wasted (or not beneficial) into the form of heat released to the surroundings

Photograph 6.16

Solution Useful energy output × 100% Energy input supplied 8J = × 100% 100 J = 8%

Energy efficiency of filament bulb =

6.4.1

195

Technology which Applies the Concept of Energy Efficiency The technology of electrical lighting devices which applies the concept of energy efficiency is shown in Table 6.3. Table 6.3 Technology of electrical lighting devices which applies the concept of energy efficiency

Lighting device

Filament lamp

Energy saving lamp (compact fluorescent lamp, CFL)

LED lamp

Maximum electrical energy converted to light energy ≈ 10%

Maximum electrical energy converted to light energy ≈ 50%

Maximum electrical energy converted to light energy ≈ 90%

Structure

Energy efficiency

MARVELS OF

Case Ca C a ase se s e S St Study t dy tu tudy tud y Gather information on technology applying the concept of energy efficiency from various sources including the following website: http://links.andl17.com/BT_Science_196

SCIENCE

The filament bulb lasts approximately 1 000 hours, CFL lasts 8 000 hours and LED lasts between 20 000 to 50 000 hours!

Discuss the information gathered. List examples of technology that apply the concept of energy efficiency in order of their importance in daily life.

Do you know how we can identify an energy efficient electrical appliance? Have you ever seen the energy efficient label introduced by the Energy Commission (EC) shown in Figure 6.36? 196

6.4.2

Chapter 6: Electricity and Magnetism

My Malaysia M The Energy Commission (EC) has launched an energy efficiency labelling program for various types of electrical appliances for public interest. Energy rating: 1 to 5-star

Appliance type Lebih Banyak Bintang Lebih Jimat Belanja More Stars More Energy Saving

PENGGUNAAN TENAGA

Appliance energy rating (Equals the number in the energy rating)

ENERGY CONSUMPTION XXX

Penyaman Udara

GWC09KF-K3DNA6A/1



Information on the brand and model

Energy consumption (in kWh/year)

Penggunaan Tenaga Purata Setahun Average Energy Consumption Per Year

1597 kWh

Energy savings compared to 2-star rated product (in percentage)

Produk ini Menggunakan 51.55% Kurang Tenaga Daripada Produk Biasa This product consume 51.55 % Less Energy Than An Average Product Diuji Mengikut / Tested According To MS ISO 5151: 2004

Suruhanjaya Tenaga

www.st.gov.my

Testing standards used

62229936279

Figure 6.36 Energy efficiency label introduced by the Energy Commission (EC)

Use of Electricity in Electrical Appliances Photograph 6.17 shows an electric meter for a three-phase wiring system. The function of an electric meter is to measure the quantity of electricity used. The reading on the electric meter is taken at the end of every month for the purpose of determining the cost of electricity consumed.

SELVI

Do you know how to read the electric meter in your house? What is the electric meter reading in Photograph 6.17?

Photograph 6.17 Electric meter 6.4.2

6.4.3

197

Electric Power, P Electric power, P, is the rate of electrical energy, E, used by an electrical device. The S.I. unit for power is watt (W). The power of 1 watt (W) means 1 joule (J) of electrical energy used in 1 second (s). Electric power can be defined as follows: Electric power, P (W) =

Electrical energy used, E (J) Time taken, t (s)

Electric Current, I Electric current, I, is defined as the rate of flow of electric charge, Q, through a conductor. The S.I. unit for electric current is ampere (A) and electric charge is coulomb (C). Electric current is defined as follows: Electric current, I (A) =

Electric charge, Q (C) Time taken, t (s)

Voltage, V Voltage, V, is defined as the electrical energy, E, used to move a unit of electric charge, Q, through a conductor. The S.I. unit for voltage is volt (V). Voltage can be defined as follows: Voltage, V (V) =

Electrical energy used, E (J) Electric charge, Q (C)

SCIENCE INFO

40 W

60 W

Photograph 6.18 Two light bulbs with different electrical power Photograph 6.18 shows two light bulbs which are used in homes. The 40 W light bulb uses electrical energy at the rate of 40 J s–1 while the 60 W light bulb uses electrical energy at the rate of 60 J s–1. Therefore, the 40 W light bulb with a lower watt rating uses less energy.

198

6.4.3

Chapter 6: Electricity and Magnetism

Calculating Flow of Current through Electrical Appliances By relating power, voltage and electric current, the total electric current that flows through an electrical appliance can be determined. Observe the following example. Then, carry out Activity 6.10 to learn more about power, voltage and current that flows through electrical home appliance.

BRAIN TEASER

Example Model : SJK-17M MS 472 : 1979 Voltage : 240VAC/50Hz Capacity : 1.7L Watt : 2.2kW Product of Malaysia

Electric jug with Power rating = 2 200 W Voltage rating = 240 V

Photograph 6.19

Can the electric jug manufactured in Malaysia shown in Photograph 6.19 be used in Thailand? In Thailand, the voltage for alternating current supplied to homes is 120 V. What will happen if the electric jug is used in Thailand?

The electric jug shown in Photograph 6.19 is rated 2.2 kW, 240 V. Calculate the current that flows through it.

Solution Using the equation P = VI P I= V 2.2 kW = 240 V 2 200 W = 240 V = 9.17 A

Activity 6.10 To study the power, voltage and current flowing through electrical home appliances

• ICS • Inquiry-based activity

Instructions 1. Work individually. 2. List examples of electrical appliances in your home. Gather information on the power and voltage of these electrical appliances. 3. Calculate the total current that flows through these electrical appliances using the following equation: Power (W) = Voltage (V) × Electric current (A) 4. Present the information you have gathered. 6.4.3

199

Calculating the Cost of Electrical Energy Used The common unit used for electrical energy is kilowatt-hour (kWh) as shown on the electric meter in Photograph 6.17. 1 kilowatt-hour is the amount of electrical energy used at the rate of 1 kilowatt or 1 000 watts in 1 hour. 1 kWh is usually referred to as 1 unit. Electrical energy can be calculated using the following equation: Electrical energy used (kWh) = Power (kW) × Time (h)

Example A 2 kW electric kettle takes 10 minutes to boil water. Calculate the cost of electrical energy used to boil the water if the rate per unit is 21 sen.

Solution Electrical energy used (kWh) = Power (kW) × Time (h) 10 h = 2 kW × 60 1 = kWh 3 1 = unit 3 1 Cost of electrical energy used for the electric kettle = unit × 21 sen/unit 3 = 7 sen Let us carry out Activity 6.11 to audit the cost of electrical energy used at home as a way of saving electrical energy.

Activity 6.11 To audit the cost of electrical energy used at home as a way of saving electrical energy

• CPS • Project-based activity

Instructions 1. Work individually. 2. Gather your home electricity bills for the past three months. 3. Study and draw a conclusion on the pattern of the cost of electrical energy used in your home which is observed based on http://links.andl17.com/ the records of the electricity bills. BT_Science_200 4. Download the PDF page from the URL on the right. 5. Suggest other practices that save electrical energy besides those listed in the electrical energy saving guide. 6. Take measures to save electrical energy for a period of three months. Compare and contrast the pattern of the cost of electrical energy used in your home before and after the measures are taken. 7. Share your findings in class.

200

6.4.4

6.4.5

Chapter 6: Electricity and Magnetism

Ways to Save Electrical Energy Consumption Other than encouraging the saving of electrical energy consumption in homes, the Energy Commission also provides services such as ECOS for the use of industries and businesses that apply the concept of energy conservation. The green building shown in Photograph 6.20 which applies the concept of energy conservation has succeeded in reducing the cost of electrical energy consumption. The construction of green buildings is gradually expanding in Malaysia. Among the features of a green building are as follows: • Efficient ventilation system to reduce the use of air conditioning and fans • Maximising the use of natural lighting to reduce the cost of electrical energy consumption • Installation of solar panels as a renewable energy source to replace conventional energy sources Let us carry out Activity 6.12 to further understand the green building concept in local and global contexts.

Photograph 6.20 A green building

My Malaysia M ECOS – Online system provided by Energy Commission related to energy efficiency. http://links.andl17.com/ BT_Science_202_2

BRAIN TEASER Does a green building mean a building that only has green plants?

Activity 6.12 To understand the green building concept in the local and global contexts Instructions 1. Work in groups. 2. Gather and share information on the following: (a) Green building concept in the local context (b) Green building concept in the global context Latest information on greenhouse and reducing the release of carbon dioxide. http://links.andl17.com/ BT_Science_201

• ICS, ISS • Technology based activity

1. Obey the ethics of social media use. 2. Respect intellectual property rights.

3. Discuss the information shared. 4. Present the findings of your group discussion using multimedia presentation such as MS PowerPoint or social media. 6.4.6

201

Designing a Model of a Green Building Did you build a model of a greenhouse when you were in Form 2? Let us carry out Activity 6.13 to innovate or invent another model of a greenhouse which uses the concept of energy savings.

Activity 6.13 Innovate or design a model of a green building using the concept of energy savings

• ICS, ISS, CPS • Project-based

Instructions 1. Work in groups. 2. Innovate or create a green building model using the concept of energy conservation in a local or global context. Among the points to be emphasized are: (a) energy efficiency (b) power sales (c) appliances with Energy Efficiency Rating and Labelling 3. You can refer to the following websites: TNB – Energy efficiency, power sales, appliances with Energy Efficiency Rating and Labelling http://links.andl17.com_ BT_Science_202_1

ECOS – Energy Commission (EC) services related to energy efficiency http://links.andl17.com/ BT_Science_202_2

4. Present your group's innovation or creation of the green building model in class.

Formative Practice

6.4

1. Give the definition of energy efficiency. 2. The electrical energy used by an air conditioner for 2 minutes is 180 kJ. Calculate the power of this air conditioner in the following units: (a) W (b) kW 3. A microwave oven rated 1.2 kW, 240 V is connected to a 240 V electricity supply. Calculate the current that flows through the oven. 4. An electric rice cooker rated 800 W, 230 V is switched on for 30 minutes. (a) How much electrical energy is used by the rice cooker? (b) Calculate the cost of energy that is used by the rice cooker if the cost per kWh is 30 sen. 5. (a) What is the importance of star rating labelling of an electrical appliance? (b) How many stars in the star rating label of an electrical appliance should be used? Explain your answer. 202

6.4.6

Summary Electricity and magnetism is applied in

Generation of electricity

Electricity generator

Solar cells and dry cells

Transmission and distribution system

Electric efficiency

produces

produce

made up of

depends on

Alternating current

Direct current

With variable voltage

With fixed voltage W

from

Renewable energy sources

Non-renewable energy sources

such as

such as

Hydro, wave, solar, tidal, wind, biomass, geothermal energies

Nuclear energy, y, coal, natural gas, as, petroleum C.R.O. screen

Power station, step-up tra transformer station, Na National Grid Network, ste step-down transformer sta station, main su substation, switch zo zone, branch su substation

C.R.O. screen with

producing

Induced current

increased by

decreased by

Step-up transformer

Step-down transformer

when

magnetic field lines are cut by coil of wire

203

According to the formula: Vp Np = Vs Ns

With fixed d.c. voltage

One-phase and three-phase wiring systems and

Safety components

and

Method of saving electrical energy used Chapter 6: Electricity and Magnetism

With a.c. voltage

Power, voltage, current, energy consumption, cost of energy consumption

Self-reflection After studying this chapter, you are able to: 6.1 Generation of Electricity Describe energy sources in terms of renewable energy and non-renewable energy. Explain with examples the process of generating electricity from various sources of energy. Differentiate between direct current and alternating current. Solve problems related to electricity supply in life. 6.2 Transformer Carry out an experiment to build step-up and step-down transformer. Communicate transformers and the use of transformers in electrical home appliances. Solve numerical problems using formula involving transformers. 6.3 Transmission and Distribution of Electricity Explain the functions of the components in the transmission and distribution of electricity by drawing. Explain with examples electricity supply and wiring systems in homes. Distinguish between safety components in a home electrical wiring system. Communicate safety in transmission and distribution of electricity and the use of electrical appliances. 6.4 Calculate the Cost of Electricity Consumption Define energy efficiency. List examples of technology that applies the concept of energy efficiency. Determine the amount of electricity used in electrical appliances. Relate electrical energy consumption, power and time by calculating the cost of electrical energy used by electrical appliances. Conduct a home energy audit of electrical appliances used as a measure of saving electricity use at home. Communicate ways of saving electrical energy use at home.

Summative Practice

6

Answer the following questions: 1. Determine whether the given statements about electricity or magnetism are True or False. Write your answer in the space provided. (a) Power stations that use wind energy do not contaminate the air. (b) Solar cells can produce alternating current. (c) 2-pin plugs are not connected to the earth wire. 204

Chapter 6: Electricity and Magnetism

2. Match each of the following energy sources with the correct type of energy. Energy source

Type of energy source

(a) Coal Renewable energy source

(b) Biomass

Non-renewable energy source

(c) Geothermal (d) Wave 3. A coil of wire is moved in the direction of the arrow through the space between two magnets as shown in Figure 1. (a) What is the effect on the magnetic field when the coil is moved? (b) What is produced in the coil of wire? (c) What happens to the LED? Explain your answer. (d) Name a device in power stations that applies a similar concept.

LED

Coil of wire

Direction of movement of coil

Figure 1

4. Figure 2(a) shows a device used to investigate electric current.

Figure 2(a)

205

(a) Name the device shown in Figure 2(a). (b) What are the properties of electric current studied using this device? (c) Figures 2(b) and 2(c) show two traces displayed on the screen of this device.

Figure 2(b)

Figure 2(c)

Name the type of electric current represented by the trace on the screen in the following figures: (i) Figure 2(b) (ii) Figure 2(c) 5. Figure 3 shows a type of transformer. (a) Name the type of transformer. (b) Explain your answer in question 5(a). (c) Why is a laminated iron core used in a transformer? (d) If the number of turns in the primary coil is 100 and the number of turns in the secondary coil is 20, calculate the secondary voltage if the primary voltage is 10 V.

Primary coil

Secondary coil

Figure 3

6. (a) Name the safety component in the electrical wiring system in homes supplied by TNB, SEB or SESB. (b) State one similarity and one difference between a fuse and Miniature Circuit Breaker (MCB). (c) What is the suitable fuse rating of a hair dryer rated 700 W, 240 V? Explain your answer.

Focus on HOTS HOTS 7. An electric heater is rated 230 V, 10 A. (a) Calculate the power of the electric heater in kW. (b) Which fuse is most suitable for the electric heater? Explain your answer. (c) Explain why other fuses are not suitable to be used based on the answer for question 7(b).

206

Chapter 6: Electricity and Magnetism

8. Figure 4 shows a model of Miniature Circuit Breaker (MCB). Reset button Contact Iron Fulcrum Current

Spring

Current

Figure 4

(a) What is an MCB? (b) State the function of an MCB and the way it works. (c) You are required to build an MCB model using the materials provided below. Explain the function of each part.

Ice cream stick

Shoe box

Plastic toothpick Copper wire Rubber eraser

Plastic rod Nail

Plasticine

207

Chapter Chapter Chapte hapte apte pte er

77

Energy and Power

What is the definition of work, energy and power? What is meant by gravitational potential energy, elastic potential energy and kinetic energy? What is the Principle of Conservation of Energy?

Let’s study Work, energy and power Potential energy and kinetic energy Principle of Conservation of Energy

208

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Keywords Work Energy Power Gravitational potential energy

Elastic potential energy Kinetic energy Displacement Average force

Principle of Conservation of Energy Oscillation of a simple pendulum Oscillation of a loaded spring Closed system

209

7.1

Work, Energy and Power

Work What is the meaning of work? Compare and contrast your meaning of work with the definition of work in science as follows: Work, W, is defined as the product of force, F, and displacement, s, in the direction of the force, that is W = Fs.

SCIENCE INFO Displacement is the distance travelled in a specified direction.

The S.I. unit for work is joule (J). 1 joule (J) of work is done when a force of 1 newton (N) is used to move an object over a distance of 1 metre (m) in the direction of the force, that is 1 J = 1 Nm. Moment of force and energy are two physical quantities other than work which are measured in units of newton metre (Nm). Larger units such as kilojoule (kJ) and megajoule (MJ) are also used in the measurement of work.

BRAIN TEASER Complete the following: (a) 1 kJ = J (b) 1 MJ = J

Examples of Calculation of Work in Daily Activities Study Figure 7.1 and Photograph 7.1. The figure and photograph show several activities in daily life.

(Correct way to lift a heavy load)

20 N Force against gravitational force, 20 N

Weight of load, 20 N 20 N Activity A Lifting an object vertically through a height of 1 m with a force of 20 N against the gravitational force.

Figure 7.1 Daily activity related to work

210

7.1.1

Chapter 7: Energy and Power Activity B Pushing a trolley over a distance of 5 m with a force of 10 N.

Activity C Pulling a drawer over a distance of 30 cm with a force of 2 N.

Photograph 7.1 Daily activities related to work

The work done in Activities A, B and C are shown in Table 7.1. Table 7.1 Work done in Activities A, B and C Direction of force

Displacement in the direction of the force (m)

Daily activity

Force (N)

Work done

A

20

Vertical

1

W = Fs = 20 N × 1 m = 20 J

B

10

Horizontal

5

W = Fs = 10 N × 5 m = 50 J

C

2

Horizontal

0.3

W = Fs = 2 N × 0.3 m = 0.6 J

Calculating Work Done

Example 1 Figure 7.2 shows a student weighing 400 N carrying a load of 100 N while climbing a flight of stairs of a vertical height of 3 m. Calculate the work done.

Solution W = Fs = (400 + 100) N × 3 m = 500 N × 3 m = 1 500 J 7.1.1

3m

Figure 7.2

211

Example 2 Figure 7.3 shows Ali lifting a box of mass 10 kg from the floor to the top of a cupboard. How much work is done by Ali? (Assume gravitational force acting on an object of mass 1 kg = 10 N)

Solution Weight of box = 10 × 10 N = 100 N W = Fs = 100 N × 2 m = 200 J

Example 3 A labourer pulled a bucket of cement weighing 300 N from the ground to the first floor of a building using a pulley system. The first floor is 10 m from the ground. What is the work done by the labourer?

Solution

2m

Figure 7.3

BRAIN TEASER Is work done in the situation shown in the photograph?

W = Fs = 300 N × 10 m = 3 000 J

Energy and Power Energy is defined as the ability to do work. The S.I. unit for energy is joule (J). When a force of 1 N is used to move an object over a distance of 1 m in the direction of the force, 1 J of energy is used.

Weight of load 10 N

Study Figure 7.4. If Kamal and Ah Kit climbed the steps starting from the ground floor simultaneously, who has a higher power? Why?

Kamal

LIM

Weight of load 10 N

Ah Kit

Power, P, is defined as the rate of doing work, W, that is: Power, P =

Work done, W Time taken, t

Figure 7.4

The S.I. unit for power is watt (W). When 1 joule (J) of work is done in 1 second (s), power of 1 watt (W) is used, that is 1 W = 1 J s–1. 212

7.1.1

Chapter 7: Energy and Power

Examples of Calculation of Power in Daily Activities Figure 7.5 shows several activities in daily life.

B 30 N 2m

A

Activity E Activity D

Aizul pulled a box up a smooth ramp from A to B with a force of 30 N over a distance of 2 m (in the direction of the force) in 5 s.

A monkey weighing 50 N climbed a height of 3 m up a tree in 20 s.

Activity F A 150 N weight is lifted to a height of 1 m in 0.5 s.

Figure 7.5 Daily activities related to power

Work done and power needed in activities D, E and F are shown in Table 7.2. Table 7.2 Work done and power needed in Activities D, E and F Daily activity

D

E

F

Force (N)

50

30

150

Displacement in the direction of force (m)

3

2

1

Work done

W = Fs = 50 N × 3 m = 150 J

Time taken (s)

20 W t 150 J = 20 s = 7.5 W

P= Power needed

7.1.2

W = Fs = 30 N × 2 m = 60 J

W = Fs = 150 N × 1 m = 150 J

5 W t 60 J = 5s = 12 W

P=

0.5 W t 150 J = 0.5 s = 300 W

P=

213

Calculating Work and Power Needed

Activity 7.1

Inquiry-based activity

Aim: To calculate work and power needed Materials 100 g weight, thread and wooden block Apparatus Spring balance, metre rule and stopwatch Instructions 1. Set up the apparatus as shown in Figure 7.6. Wooden block

Spring balance Pull













































Table

Thread

1.0 m

Figure 7.6 2. Pull the spring balance until the wooden block starts to move and record the force shown on the spring balance. 3. Pull the wooden block over a distance of 1.0 m with the force as shown in Figure 7.6. Ask your friend to measure the time taken to move the wooden block by using a stopwatch. 4. Record the time taken. Calculate and record the work done and power needed in a table. 5. Set up the apparatus as shown in Figure 7.7. 6. Lift the 100 g weight to a vertical height of 0.5 m from the floor by using the spring balance. 7. Record the force shown on the spring balance. 8. Ask your friend to measure the time taken to move the weight by using the stopwatch. 9. Record the time taken. Calculate and record the work done and power needed in a table.

0 1 2 3 4 5 6 7 8 9 10 0

0 1

Spring balance

0.5 m

2 3 4 5 6 7 8 9 10

100 g weight Floor

Figure 7.7

214

7.1.1

7.1.2

Chapter 7: Energy and Power

Force (N)

Activity

Distance (m)

Work (J)

Time (s)

Power (W)

Pulling a wooden block over a distance of 1.0 m horizontally Lifting a 100 g weight to a height of 0.5 m vertically Questions 1. State the type of force to overcome when: (a) pulling a wooden block on the surface of the table (b) lifting a 100 g weight vertically from the floor 2. Which activity involves more work? 3. State three factors that affect power. 4. Which activity is carried out with higher power? 5. (a) Give one example of an activity or object in daily (b) Give one example of an activity or object in daily

Formative Practice

Today in history A unit usually used for power in the olden days is horsepower (hp).

life that involves high power. life that involves low power.

7.1

1. (a) State the definition of work. (b) What is the S.I. unit for work? 2. What is the meaning of energy? 3. (a) State the definition of power. (b) What is the S.I. unit for power? 4. Figure 1 shows an electromagnetic crane lifting a load weighing 2 500 N to a height of 4 m. (a) Calculate the work done. (b) How much energy is used by the crane to lift the load? (c) If the time taken by the crane to lift the load is 1.2 minutes, calculate the power of the crane. Figure 1

7.1.1

7.1.2

215

7.2

Potential Energy and Kinetic Energy

In a piledriver shown in Photograph 7.2, a hammer is pulled upwards and then released to fall and hit a pile. The force produced by the hammer in a vertical direction drives the pile into the ground.

N CA

G

E

Watch this video to see piling operations

S

Gravitational Potential Energy

PA

Hammer

Pile

(a) Hammer before being dropped

(b) Hammer after being dropped

Photograph 7.2 Gravitational potential energy is used in a piledriver Why is work done?

A hammer lifted to a height, h from the Earth’s surface possesses gravitational potential energy. Gravitational potential energy is the work done to lift an object to a height, h, from the Earth's surface.

RIFQI

What type of force is produced by the hammer? Where does the energy to do the work come from?

Gravitational potential energy = mgh • m is the object mass in kg • g is the gravitational acceleration in m s–2 • h is the height in m

216

SCIENCE INFO Weight = mass, m × gravitational acceleration, g where g is estimated at 10 m s–2 (or 10 N kg–1)

7.2.1

Chapter 7: Energy and Power

Relationship between Work and Gravitational Potential Energy Figure 7.8 shows an object of mass, m, being lifted vertically to a height, h, from Earth’s surface.

Weight

Work done = Force × displacement in direction of force = Weight × height lifted = (m × g) × h = mgh

h

Since there is no other form of energy produced, all work done on the object will be converted to gravitational potential energy. Gravitational potential energy = work done = mgh

Figure 7.8

Example of numerical problem Photograph 7.3 shows a lift at KLCC mall. The lift can carry a load of mass 1 500 kg to a height of 30 m. (a) How much work is done by this lift? (b) What is the gravitational potential energy of this lift at a height of 30 m? (c) What is the relationship between work done by the lift and gravitational potential energy of the lift? (d) What is the power of the lift in kW if the time taken to lift a load of mass 1 500 kg to a height of 30 m is 0.5 minutes? Solution (a) W = Fs = mgh = 1 500 kg × 10 m s–2 × 30 m = 450 000 J (b) Gravitational potential energy = mgh = 1 500 kg × 10 m s–2 × 30 m = 450 000 J (c) Work done by the lift = Gravitational potential energy of the lift W (d) Power, P = t 450 000 J = 0.5 minutes 450 000 J = Additional Examples 30 s http://links. = 15 000 W and l17.com/BT_ Science_217_2 = 15 kW

7.2.1

Photograph 7.3

217

Elastic Potential Energy Photograph 7.4 shows the steps to refill a stapler with staples. There is a spring that is stretched and then released. The force produced by the stretched spring moves the staples in the direction of the force.

What type of force is produced by the spring?

Why is work done? Where does the energy that carries out the work come from? Spring

AIN

Staples

Photograph 7.4 Elastic potential energy used in a stapler

A spring that is compressed or stretched possesses elastic potential energy. Elastic potential energy is the work done to compress or stretch an elastic material over a displacement of x from the position of equilibrium. Elastic potential energy =

1 Fx 2

• F is the stretching or compression force in N • x is the displacement from the equilibrium position in m

218

7.2.2

Chapter 7: Energy and Power

Relationship between Work and Elastic Potential Energy Assume a spring is stretched x m with a force of F N (Figure 7.9(a)). So, the value of force acting on the spring changes from 0 N to F N as shown in the graph (Figure 7.9(b)). For situations involving springs, work done is equivalent to the area under the F-x graph.

Elastic potential energy = work done = area under the graph 1 = Fx 2

Force (N) Original length of spring

F

Extension of spring, x m

Force, 0 N

Force = F N

0

(a)

Extension/ Compression (m)

x

(b)

Figure 7.9 Relationship between work and elastic potential energy

Example of numerical problem The original length of spring S is 20 cm. When the final force exerted on spring S is 20 N, its new length becomes 12 cm. Calculate the elastic potential energy possessed by the compressed spring S. Solution Distance of compression, x = original length – new length = 20 cm – 12 cm = 8 cm = 0.08 m 1 Elastic potential energy = Fx 2 1 = × 20 N × 0.08 m 2 = 0.8 J

7.2.2

Force, 20 N

20 cm

Spring S 12 cm

Figure 7.10

Additional Examples http://links. and l17.com/BT_ Science_219_2

219

Kinetic Energy Kinetic energy is the energy possessed by a moving object. Kinetic energy =

1 mv2 2

• m is mass in kg • v is velocity in m s–1

Example of numerical problem Example 1 When a train of mass 500 000 kilogram moves with a velocity of 360 km h–1, how much kinetic energy is possessed by the train? Solution Velocity of train = 360 km h–1 360 km = 1h 360 000 m = 3 600 s = 100 m s–1

1 mv2 Kinetic energy = 2 of train 1 = × 500 000 kg × (100 m s–1)2 2 = 2 500 000 000 J

Example 2 A ball bearing of mass 0.2 kg possesses kinetic energy of 3.6 J. What is the velocity, v of the ball bearing? Solution 1 mv2 2 1 × 0.2 kg × v2 3.6 J = 2 3.6 J ∴ v2 = 0.1 kg = 36 m2 s–2 v = 36 m2 s–2 = 6 m s–1

Kinetic energy =

Example 3 Calculate the kinetic energy of an electron of mass 9 × 10–31 kg and velocity 4 × 106 m s–1. Solution 1 mv2 2 1 × (9 × 10–31 kg) × (4 × 106 m s–1)2 = 2 = 7.2 × 10–18 J

Kinetic energy of electron =

220

7.2.3

Chapter 7: Energy and Power

Let us carry out Activity 7.2 to discuss the meaning and examples of gravitational potential energy, elastic potential energy and kinetic energy in daily life.

Activity 7.2 To discuss the meaning and examples of gravitational potential energy, elastic potential energy and kinetic energy in daily life

• ICS, ISS • Discussion activity

Instructions 1. Work in groups. 2. Each group needs to search for information on the meaning and examples of gravitational potential energy, elastic potential energy and kinetic energy in daily life. 3. Present the information in a mind map.

Formative Practice 7.2 1. (a) What is the relationship between gravitational potential energy and work? (b) What is the relationship between elastic potential energy and work? 2. Liza lifts a chair weighing 40 N to a height of 50 cm. (a) How much work is done by Liza to lift the chair? (b) What is the form of energy possessed by the chair? (c) How much energy is possessed by the chair? 3. Force, F, is exerted on a plank to compress a spring towards the wall as shown in Figure 1. Given that the original length of the spring is 50 cm, final length is 30 cm and final force exerted on the spring is 20 N. How much elastic potential energy is possessed by the compressed spring? 4. (a) Why are heavy vehicles shown in Figure 2 usually of low velocity but possess high kinetic energy? (b) State one example of a daily object that possesses high kinetic energy in the following conditions: (i) Object of small mass but high velocity (ii) Object of large mass and high velocity

Wall

Plank Spring

Force, F

Figure 1

Figure 2 7.2.3

221

7.3

Principle of Conservation of Energy

Photograph 7.5 Roller coaster

The roller coaster shown in Photograph 7.5 involves transformation in the forms of energy. State the transformation in the forms of energy.

Principle of Conservation of Energy The Principle of Conservation of Energy states that energy cannot be created or destroyed but can only be converted from one form to another. Oscillating systems such as the oscillation of a simple pendulum and the oscillation of a loaded spring always experience transformation in the forms of energy between gravitational potential energy or elastic potential energy and kinetic energy. Do oscillating systems obey the Principle of Conservation of Energy? 222

SCIENCE INFO Useful energy is energy in a form that can be easily converted into other forms to do work. For example, chemical energy stored in fossil fuels is useful energy because the chemical energy can be easily converted to heat energy and light energy through the combustion of fossil fuels.

7.3.1

Chapter 7: Energy and Power

Oscillating Systems Obey the Principle of Conservation of Energy Study Figures 7.11 and 7.12. Let us observe the transformation in the forms of energy that occurs in the oscillation of a simple pendulum and a loaded spring which are the examples of the Principle of Conservation of Energy.

Pendulum bob

X

Z 4

3

Bob released 1

Condition of pendulum bob

At position X 1 From position X to Y At position Y 2 From position Y to Z At position Z 3 From position Z to Y At position Y 4 From position Y to X At position X

Y

2

Transformation in the forms of energy for the bob between gravitational potential energy (gravitational P.E.) and kinetic energy (K.E.) Gravitational P.E. = maximum K.E. = zero

(bob at maximum height) (bob stationary, speed = zero)

Gravitational P.E. of bob decreasing K.E. of bob increasing

(height of bob decreasing) (speed of bob increasing)

Gravitational P.E. = minimum K.E. = maximum

(bob at minimum height) (bob at maximum speed)

Gravitational P.E. of bob increasing K.E. of bob decreasing

(height of bob increasing) (speed of bob decreasing)

Gravitational P.E. = maximum K.E. = zero

(bob at maximum height) (bob stationary, speed = zero)

Gravitational P.E. of bob decreasing K.E. of bob increasing

(height of bob decreasing) (speed of bob increasing)

Gravitational P.E. = minimum K.E. = maximum

(bob at minimum height) (bob at maximum speed)

Gravitational P.E. of bob increasing K.E. of bob decreasing

(height of bob increasing) (speed of bob decreasing)

Gravitational P.E. = maximum K.E. = zero

(bob at maximum height) (bob stationary, speed = zero)

Figure 7.11 Oscillation of a simple pendulum 7.3.1

223

Spring

Z

Z 2

3

Y

Y 1

Equilibrium position

4

X

X Load

Condition of loaded spring

At position X

1 From position X to Y At position Y 2 From position Y to Z At position Z 3 From position Z to Y At position Y

4 From position Y to X At position X

Transformation in the forms of energy for the load between elastic potential energy (elastic P.E.) and kinetic energy (K.E.) Elastic P.E. = maximum K.E. = zero

(spring is most stretched) (spring is stationary, speed = zero)

Elastic P.E. decreasing K.E. increasing

(spring is gradually becoming less stretched) (speed of spring increasing)

Elastic P.E. = minimum K.E. = maximum

(spring at equilibrium) (speed of spring at maximum)

Elastic P.E. increasing K.E. decreasing

(spring is gradually becoming more compressed) (speed of spring decreasing)

Elastic P.E. = maximum K.E. = zero

(spring is most compressed) (spring is stationary, speed = zero)

Elastic P.E. decreasing K.E. increasing

(spring is gradually becoming less compressed) (speed of spring increasing)

Elastic P.E. = minimum K.E. = maximum

(spring at equilibrium) (speed of spring at maximum)

Elastic P.E. increasing K.E. decreasing

(spring is gradually becoming more stretched) (speed of spring decreasing)

Elastic P.E. = maximum K.E. = zero

(spring is most stretched) (spring is stationary, speed = zero)

Figure 7.12 Oscillation of a loaded spring

224

7.3.1

Chapter 7: Energy and Power

Transformation of Kinetic Energy and Potential Energy in a Closed System In a closed system, the transformation of energy between potential energy and kinetic energy obeys the Principle of Conservation of Energy. Therefore, the total potential energy and kinetic energy in a closed oscillation system is constant. An example of a closed oscillation system is shown in Figure 7.13(a). Figure 7.13(b) shows the transformation of energy in a graph. Energy

P.E. = maximum K.E. = zero

P.E. = maximum K.E. = zero –A

Total energy (constant)

O Equilibrium position P.E. = minimum K.E. = maximum

A

Figure 7.13(a) Oscillation of a pendulum in a closed system

Potential energy, P.E.

Kinetic energy, K.E. –A

A Displacement

O Equilibrium position

Figure 7.13(b) Graph of the transformation in the forms of energy

SCIENCE INFO Based on the Principle of Conservation of Energy, energy can transform from one form to another. When energy transforms, a small portion of the energy is converted into useful energy. A large portion of the energy is converted into wasted energy such as heat energy caused by friction. A closed system is a system in which there is no external force such as friction. Hence, heat energy is not produced in a closed system.

Let us carry out Activity 7.3 to discuss daily situations involving transformation of energy.

Activity 7.3 To discuss daily situations involving transformation of energy

• ICS, ISS

Instructions • Discussion activity 1. Work in groups. 2. Each group needs to gather information on transformation of energy in daily situations such as the oscillation of a swing, an object falling from a certain height, a roller coaster and toys with springs such as toy cars and pistols. 3. Label and state the form and transformation of energy at certain positions. 4. Present the outcome of your group discussion in class.

7.3.2

225

Example of numerical problem Figure 7.14 shows a toy pistol. The length of the spring in the toy pistol is 300 mm. If a force of 5 N is used to compress the spring until its length becomes 50 mm, calculate the maximum speed of the plastic ball of mass 50 g when it is fired from the pistol. State an assumption that is made in solving this problem.

50 mm

250 mm

Plastic ball

Solution Based on the Principle of Conservation of Energy, Figure 7.14 elastic potential energy stored in the spring = kinetic energy of the plastic ball. 1 1 Fx = mv 2 2 2 1 250 1 50 ×5N× m= × kg × v2 2 1 000 2 1 000 ∴ v2 = 25 m2 s–2 Additional Example v = 25 m2 s–2 http://links. = 5 m s–1 and l17.com/BT_ Science_226_2 Assumption: No energy loss into the surroundings.

Formative Practice

7.3

1. State the Principle of Conservation of Energy. 2. An oscillating loaded spring as shown in Figure 1 is a closed oscillation system. (a) State the position of the load where the elastic potential energy of the system is maximum. (b) State the position of the load where the elastic potential energy of the system is minimum.

P

Load

Q R

Figure 1

3. Figure 2 shows a metal sphere of mass 2 kg released from a height of 2.5 m from the surface of Earth. (a) Calculate the gravitational potential energy possessed by the metal sphere before being released. (b) What is the maximum speed of the metal sphere after being released?

Figure 2

226

7.3.2

Chapter 7: Energy and Power

Summary Energy is the ability to carry out

Work is related to

is defined as

Work = Force × displacement W = Fs

Work Time W P= t

Power =

measured in S.I. unit

exists in forms such as

Gravitational potential energy = mgh

Elastic potential energy 1 Fx =— 2

Kinetic energy 1 mv2 = — 2

which

joule (J)

measured in S.I. unit

1 J defined as

watt (W)

Can transform from one form to another

1 W defined as

as stated in the

Work of 1 J done in 1 s

Principle of Conservation of Energy

Force of 1 N moving an object over a distance of 1 m in the direction of the force

Self-reflection After studying this chapter, you are able to: 7.1 Work, Energy and Power Define work and solve problems related to energy in the context of daily life. Relate power with work and solve problems in the context of daily life. 7.2 Potential Energy and Kinetic Energy Explain with examples gravitational potential energy and solve problems in the context of daily life. Calculate elastic potential energy in the context of daily life. Explain with examples kinetic energy in the context of daily life. 7.3 Principle of Conservation of Energy Explain with examples the Principle of Conservation of Energy. Solve qualitative and quantitative problems involving the transformation of kinetic energy and potential energy in a closed system. 227

Summative Practice

7

Answer the following questions: 1. There are many forms of energy. Match the following form of energy with its correct definition. Form of energy

Definition Ability to do work

(a) Potential energy Energy possessed by a moving object (b) Kinetic energy Energy possessed by an object due to its position or condition 2. Underline the correct answers. (a) The unit for energy is (J s/N m). (b) (Work/Power) is defined as the product of force and displacement in the direction of the force. (c) A (stationary/moving) object does not possess kinetic energy. (d) The Principle of Conservation of Energy states that Motor energy (can/cannot) transform its form. (e) Weight is the product of mass and (force/acceleration) of gravity. 3. Figure 1 shows a motor lifting a load of mass 5 kg to a height of 2 m. (a) Calculate the work done by the motor. (b) How much energy is used by the motor to lift the load?

2m 5 kg

4. State the formula for the following energy: (a) Gravitational potential energy (b) Elastic potential energy (c) Kinetic energy

Figure 1 motor

5. Figure 2 shows a female archer pulling her bowstring back 0.4 m with a maximum force of 200 N. (a) How much work is done? (b) Calculate the elastic potential energy possessed by the stretched bowstring. (c) Not all the work done to pull the bowstring back is changed into elastic potential energy. Why? 228

Figure 2

Chapter 7: Energy and Power

Focus on HOTS 6. Figure 3 shows the oscillation of a simple pendulum in a closed system. The mass of the pendulum bob is 40 g. (a) State the principle that needs to be obeyed by the oscillation of a simple pendulum in a closed system. (b) At which position does the pendulum possess gravitational potential energy and kinetic energy of equal value? (c) Calculate the difference in gravitational potential energy of the pendulum at positions X and Y.

X

Z

5 cm

Y

Figure 3

7. Figure 4 shows a model of a simple roller coaster.

Figure 4

You are required to build a functional model of a roller coaster using the materials below.

Rubber hose Ball bearing

Retort stands

Sketch your roller coaster model. Explain the special features of the model.

229

Chapter Cha Chapter Chapte hapte pte p ter er

1 8

Radioactivity

When was radioactivity first discovered? What are atom and nucleus? What are ionising radiation and non-ionising radiation? What are the uses of radioactive radiation in daily life?

Let’s study Discovery of radioactivity Atom and nucleus Ionising radiation and non-ionising radiation Uses of radioactive radiation

230

Science Gallery The Sun is the largest radioactive source which is close to Earth. However, many scientific investigations show that the Sun’s rays are normal and do not contain any radioactive radiation. Due to this, the Sun is considered a safe radioactive source because no radioactive radiation is released. Is this fact true? The analysis of gathered data about the coronal mass ejection in the Sun on 6 September 2017 from the astronomical telescope, Fermi, shows that the Sun’s rays also contain gamma rays (radioactive radiation). How do we protect ourselves from these gamma rays? The UV umbrella shown in the photograph below is used to block the ultraviolet rays from the Sun’s rays. Can the UV umbrella protect our body from gamma rays as well? Suggest one material to make an umbrella which is able to block gamma rays. Is the material practical? Explain your answer.

UV umbrella (Umbrella that can block ultraviolet rays)

Keywords Radioactivity Radioactive radiation Radioactive substance Radioactive decay Half-life Becquerel (Bq)

Curie (Ci) Dalton’s Atomic Theory Ionising power Cosmic ray Archaeology Geochronology

231

8.1

Discovery of Radioactivity

History of Radioactivity Study Figure 8.1 on the discovery of radioactivity.

Fins

+ 20 000 V _ Glass Tungsten container target

Electron

Vacuum Anode

Cathode

Window X-ray

Wilhelm Roentgen

Wilhelm Roentgen's X-ray photograph of his wife's hand

Heating filament

To low power supply

X-ray tube

In 1895, Wilhelm Conrad Roentgen, a German physicist, discovered X-ray. He had unintentionally taken an X-ray photograph of his wife’s hand. This success led Wilhelm Conrad Roentgen to receive the first Nobel Prize in Physics in 1901 for the discovery of X-ray.

Science Careers Various types of careers exist in the field of radioactivity. Among them are: t
researcher at Malaysian Nuclear Agency t
nuclear physicist t
nuclear engineer t
nuclear medical specialist

However, Marie Curie died at the age of 67 from a disease caused by prolonged exposure to gamma rays. Since the discovery of radium, the gamma rays emitted by radium have been used in various fields including medicine in cancer treatment. Figure 8.1 The discovery of radioactivity

232

8.1.1

Chapter 8: Radioactivity

α particle

92p 146n

Henri Becquerel

Blackened photographic plate

90p 144n

Rays emitted from the nucleus of uranium

In 1896, Antoine Henri Becquerel, a French physicist, became the first person to successfully discover radioactivity. He found a radioactive compound, uranium and unintentionally produced rays that can blacken a photographic plate even in the dark. The rays were detected based on the ionising property. Due to this, Antoine Henri Becquerel received the Nobel Prize in Physics in 1903 for the discovery of radioactivity.

Less stable radium

More stable radium

Today in history After attending a session of the paperwork presentation by Roentgen on 20 January 1896, Becquerel was surprised because his study could not produce the X-ray. Hence, Becquerel replaced the material being studied with uranium compound.

SCIENCE INFO Marie Curie is the only woman who received two Nobel Prizes, the Nobel Prize in Physics in 1903 and the Nobel Prize in Chemistry in 1911.

Gamma ray

Marie and Pierre Curie with their child

Gamma ray from radium

At the end of 1897, Marie and Pierre Curie, a married couple from Poland, successfully detected radioactive radiation through its ionising power and not through the photographic effect. Beginning with uranium ore which is known as pitchblende, they successfully extracted two radioactive elements, polonium and radium. 8.1.1

Today in history The rays discovered by Becquerel cannot produce X-ray of bones, thus nobody was interested to pursue Becquerel’s study for one and a half years! Perhaps this was what attracted the interest of Marie and Pierre Curie.

233

Radioactivity Radioactivity is a random and spontaneous decay process of an unstable nucleus by emitting radioactive radiation as shown in Figure 8.2. Radioactive radiation consists of: • alpha particles (alpha radiation), α • beta particles (beta radiation), β • gamma ray, γ Product of decay Proton (p) 92p Neutron (n) 146n

90p 144n

2p 2n

Thorium-234

Uranium-238

Helium nucleus Alpha particle, α

(a) Decay of uranium-238

Product of decay

-

Proton (p) 90p Neutron (n) 144n Electron Thorium-234

e-

-

91p 143n Protactinium-234

Radioactive radiation

Electron Beta particle, β

(b) Decay of thorium-234

Proton (p) 27p Neutron (n) 33n

27p 33n Cobalt-60*

Cobalt-60*: nucleus of cobalt is less stable

Cobalt-60

Gamma ray, γ

Cobalt-60: nucleus of cobalt is more stable

(c) Decay of cobalt-60* Figure 8.2 Three types of radioactive radiation emitted from the spontaneous decay of nuclei

Radioactive decay is a random and spontaneous process where an unstable nucleus emits radioactive radiation until the nucleus becomes more stable. Examples of radioactive elements that have unstable nuclei and decay spontaneously by emitting radioactive radiation are as follows: • Carbon-14 (C-14) • Radon-222 (Rn-222) 234

• Thorium-234 (Th-234) • Uranium-238 (U-238) 8.1.2

Chapter 8: Radioactivity

Units of Radioactivity

SCIENCE INFO

The first unit of radioactivity introduced was curie (Ci). The rate of unstable nuclei decay (or activity in nuclei decay) is measured in curie. One curie is 3.7 × 1010 decays per second, that is:

1 Ci is approximately the number of decays per second in 1 g of Radium-226 (Ra-226). Radium-226 is a radioactive substance studied by Marie and Pierre Curie.

1 Ci = 3.7 × 1010 decays/s The S.I. unit of radioactivity is becquerel (Bq). 1 becquerel (Bq) is 1 decay per second, that is:

BRAIN TEASER Complete the following: (a) 1 Ci = __________ Bq (b) 1 Bq = __________ Ci

1 Bq = 1 decay/s

Half-life of Radioactive Decay Half-life, T 12 is the time taken for the number of undecayed nuclei to be reduced to half of its original number (value). The graphic description of the situation when the number of undecayed nuclei decreases with time is shown in Figure 8.3. What is the S.I. unit for half-life?

1 2

0 Undecayed Decayed

1 2

5 days

1 8

1 4 3 4

7 8

10 days

15 days

First half-life

Second half-life

Third half-life

1 2 undecayed 1 decayed 2

1 4 undecayed 3 decayed 4

1 8 undecayed 7 decayed 8

Figure 8.3 Nuclei decay of a radioactive element with half-life of 5 days

Example

1

Protactinium-234(Pa-234) decays to Uranium-234(U-234) with half-life, T 12 , of 5.2 hours. Calculate the mass of Pa-234 after 20.8 hours with its original mass of 80 g. Solution 0 hours 80 g

5.2 hours 40 g

10.4 hours 20 g

15.6 hours 10 g

20.8 hours 5g

Thus, the remaining mass of Pa-234 after 20.8 hours is 5 g. 8.1.2

235

Example

2

A graph of activity against time for radioactive substance P is shown in Figure 8.4. Graph of activity against time for radioactive substance P

Activity (Bq) 1000 800 600 400 200 0

20

40

60

80

100 120 Time (s)

Figure 8.4

Based on the graph, what is the half-life of P?

Graph of activity against time for radioactive substance P

Activity (Bq) 1000

Solution Original activity = 800 Bq Activity at half-life = 1 × 800 Bq 2 = 400 Bq When the activity is 400 Bq, the corresponding time is 40 s as shown by the dotted line on the graph in Figure 8.5. Thus, the half-life of P is 40 s.

800 600 400 200 0

20

40

60

80

100 120 Time (s)

Figure 8.5

Example

3

The activity of radioactive substance Q against time is shown in Table 8.1. Table 8.1 Time (minutes) Activity (Bq)

0

5

10

15

20

25

120

80

56

40

28

20

(a) Draw a graph of activity against time on a piece of graph paper. (b) Based on the graph, what is the half-life of Q? 236

8.1.2

Chapter 8: Radioactivity

Solution (a)

(b) Original activity = 120 Bq Activity at half-life 1 × 120 Bq = 2 = 60 Bq From the graph in Figure 8.6, the half-life of Q is 9 minutes.

Graph of activity against time for radioactive substance Q

Activity (Bq) 140 120 100 80 60 40 20 0 5

10

15

20

25 Time (minutes)

Figure 8.6

Activity 8.1 To gather information on a cloud chamber to view the tracks produced by radioactive substances

• ICS • Inquiry-based activity

Instructions 1. Work in groups. 2. Gather information on the method to build a cloud chamber to view the tracks produced by radioactive substances. 3. Present the findings of your group.

Formative Practice

8.1

1. Name the first person who discovered: (a) the X-ray (b) radioactive radiation (c) gamma rays emitted by radium 2. What is the meaning of radioactivity? 3. (a) Name two units of radioactivity. (b) What is the quantity measured in radioactivity unit? 4. Give three examples of radioactive elements. 5. What is the meaning of half-life? 8.1.2

237

8.2

Atom and Nucleus

Atoms originate from the word ‘atomos’ which means indivisible. In 1808, John Dalton, introduced a theory on the structure of atom. According to Dalton’s Atomic Theory, an atom is the smallest particle and cannot be further divided. However, the development of science has succeeded in finding particles that are even smaller called protons, electrons and neutrons.

Structure of Atom Recall the three subatomic particles in the structure of an atom that you have learnt in Form 1 as shown in Figure 8.7. When the number of protons in an atom is the same as the number of its electrons, the atom is neutral. Positively charged particle (Proton)

Negatively charged particle (Electron)

Nucleus Neutral particle that is not charged (Neutron)

Figure 8.7 Structure of atom

Formation of Positive Ions and Negative Ions When an atom loses or gains electrons, the atom becomes a charged particle known as ion. Positive Ion (Cation) An atom that loses electrons forms a positive ion (cation). Example Table 8.2 Formation of sodium ion, Na+ Sodium ion, Na+

Sodium atom, Na Subatomic particle

Number

neutron, n

12

0

proton, p

11

+11

electron, e

11

–11

The charge on sodium atom, Na

238

Charge

0

Subatomic particle

loses 1 e–

Number

Charge

neutron, n

12

0

proton, p

11

+11

electron, e

10

–10

The charge on sodium ion, Na+

8.2.1

+1

8.2.2

Chapter 8: Radioactivity

Negative Ion (Anion) An atom that gains electrons forms a negative ion (anion). Example Table 8.3 Formation of chloride ion, Cl– Chloride ion, Cl–

Chlorine atom, Cl Subatomic particle

Number

Charge

neutron, n

18

0

proton, p

17

+17

electron, e

17

–17

The charge on chlorine atom, Cl

Formative Practice

Subatomic particle

gains 1 e–

Number

Charge

neutron, n

18

0

proton, p

17

+17

electron, e

18

–18

The charge on chloride ion, Cl–

0

–1

8.2

1. State the property of an atom according to Dalton’s Atomic Theory. 2. Explain how the following ions are formed. (a) Positive ion (b) Negative ion 3. Table 1 shows the number of protons and electrons of particles P, Q, R, S and T. (a) Which particle is a positive ion? Explain your answer. (b) Which particle is a negative ion? Explain your answer. (c) Which particle is neutral? Explain your answer.

Table 1 Particle

Number of protons

Number of electrons

P

4

4

Q

12

10

R

17

18

S

29

27

T

35

36

4. Table 2 shows the formation of an ion. Table 2 Bromine atom, Br Subatomic particle

Number

Ion X Charge

neutron, n

45

0

proton, p

35

+35

electron, e

35

–35

The charge on bromine atom, Br

0

electron transfer

Subatomic particle

Number

neutron, n

45

0

proton, p

35

+35

electron, e

36

–36

The charge on ion, X

–1

Charge

(a) How many electrons are lost or gained by the bromine atom in the formation of ion X? (b) Explain your answer in 4(a). (c) Name ion X that is formed and write its symbol. 8.2.2

239

8.3

Ionising Radiation and Non-ionising Radiation

Ionising Radiation and Non-ionising Radiation When a radiation such as radioactive radiation passes through air and produces positive and negative ions, it is known as ionising radiation as shown in Figure 8.8.

D particle

α particle loses energy

(a) Neutral air molecules

(b) Ionised air

Figure 8.8 Radioactive radiation as ionising radiation

What is the meaning of non-ionising radiation? Examples of ionising radiation and nonionising radiation are shown in Figure 8.9. Non-ionising radiation

Very low frequency wave

Radio

Ionising radiation Infrared Ultraviolet Microwave

X-ray

Visible light

Gamma ray

Figure 8.9 Ionising radiation and non-ionising radiation in an electromagnetic spectrum

Let us carry out Activity 8.2 to learn more about ionising radiation, namely alpha radiation, beta radiation, gamma ray and X-ray.

Activity 8.2 Surf the Internet and share information on ionising radiation

• ICS • Discussion activity

Instructions 1. Work in groups. 2. Surf the Internet to gather information on the following ionising radiation: (a) Alpha radiation, α (alfa particle) (c) Gamma ray, γ (b) Beta radiation, β (beta particle) (d) X-ray 3. Discuss several aspects such as size of particle, ionising power, penetration power, deflection by magnetic field and deflection by electric field. 4. Present the outcome of your group discussion using multimedia presentation.

240

8.3.1

8.3.2

Chapter 8: Radioactivity

Types of Ionising Radiation Three types of radioactive radiation which are ionising radiation are alpha radiation, α, beta radiation, β and gamma ray, γ. Study Table 8.4. Table 8.4 Differences between the three types of ionising radioactive radiations Type of radioactive radiation

Alpha radiation, α

Beta radiation, β

Gamma ray, γ

Natural characteristic

Helium nucleus

High speed electron

Electromagnetic wave

Charge of particle

Positive

Negative

Neutral

Ionising power

High

Moderate

Low

Penetration power

γ Radioactive source

β

α Paper

Aluminium (3 mm)

Low

Moderate

Lead (10 cm)

High

Deflection by electric field

Negative plate

α γ

Radioactive source

β Positive plate Deflection by magnetic field

α (upwards) S

Radioactive source

γ (straight)

N

β (downwards)

8.3.2

241

Sources of Ionising Radiation in the Environment In the environment, sources of ionising radiation are classified as natural sources of ionising radiation and man-made sources of ionising radiation as shown in Figure 8.10.

Sources of ionising radiation in the environment

Natural Examples: – Cosmic rays – Background radiation

Man-made Examples: – Nuclear accidents – Nuclear tests – Use of radioisotope for medical purposes – Background radiation

Figure 8.10 Classification of sources of ionising radiation in the environment

Let us carry out Activity 8.3 to detect natural sources of ionising radiation in the environment.

Activity 8.3 To gather information on natural sources of ionising radiation in the environment

• CPS • Inquiry-based activity

Instructions 1. Work in groups. 2. Gather information on natural sources of ionising radiation in the environment. Gather information on natural sources of ionising radiation in the environment http://links.andl17.com/BT_Science_242 3. Present your group findings.

242

8.3.3

Chapter 8: Radioactivity

Cosmic Rays Cosmic rays are high-energy radiation produced outside the Solar System or from another galaxy. These cosmic rays are also known as galactic cosmic rays. Photograph 8.1 Cherenkov telescope on Mount Hopkins, United States of America used to detect cosmic rays

Background Radiation Background radiation is made up of various types of ionising radiation in the environment. Background radiation is released from various sources including natural sources and man-made sources. Sources of background radiation include: • cosmic rays • radioactive radiation from natural radioactive substances in the surroundings • radioactive wastes from nuclear accidents and nuclear tests • radioisotopes from medical use Unit of Dose Rate Measurement for Background Radiation Ionising radiation that is absorbed into the human body will damage body cells. Due to this, the biological effect from ionising radiation on human body is measured in a quantity known as dose. A dose of 1 Sv is equivalent to 1 joule of BRAIN ionising radiation energy that is absorbed by 1 kilogram of TEASER living tissue. The unit of background radiation dose that is What is the meaning of 1 μSv/h? commonly used is microSievert/hour (μSv/h).

(a) In the garden

(b) In the school compound

Photograph 8.2 Measuring background radiation using a Geiger counter

Study and compare the readings of the dose rate of background radiation on a Geiger Counter in Photograph 8.2. What is the unit of dose rate measurement for background radiation shown in the readings on the counter? 8.3.3

243

Safe Background Radiation Dose in Daily Life Background radiation or ionising radiation SCIENCE dose of less than Safe level of background radiation 0.2 μSv/h is the dose is: normal level or • < 0.2 μSv/h • < 0.0002 mSv/h safe level. Based on • < 1 752 μSv/year Photograph 8.2, the • < 1.752 mSv/year garden and school compound are safe areas because both areas have background radiation dose of less than 0.2 μSv/h. The estimation of dose rate of ionising radiation from various sources in daily life are shown in Figure 8.11. Identify which sources are safe for an individual.

INFO

Outter space: Outer cosmic mic rays 0.35 mSv/year /

Websites Exposure to radiation in daily life

http://links.andl17.com/BT_ Science_244_2 and click “Radiation Level“

TV/computer: ionising radiation 0.01 mSv/h

X-ray 5.5 mSv/medical test

High altitude: cosmic rays 0.3 - 0.5 mSv/year

Smoking: radioactive radiation 55 mSv/cigarette

Flight: cosmic rays 0.003 mSv/h Environment: background radiation 0.4 – 1.0 mSv/year

Food: radioactive radiation 0.1 – 0.5 mSv/year

Building: radioactive radiation 1.5 mSv/year

Figure 8.11 Estimation of dose rate of ionising radiation

244

8.3.3

Chapter 8: Radioactivity

Risks from Exposure to Natural Ionising Radiation Absorption of ionising radiation by the human body imposes health risks which are affected by the dose of ionising radiation received. Several actions can be taken so that the ionising radiation dose received does not exceed the safe level for the human body as shown in Table 8.5. Table 8.5 Among the safety measures that need to be taken so that the ionising radiation dose received does not exceed the safe level for the human body Source of ionising radiation dose received

Safety measures

Background radiation

Use appropriate protective equipment such as spectacles fitted with antiultraviolet film, anti-ultraviolet umbrellas and others

Taking X-ray

X-ray taken with doctor’s prescription

Television

Ensure the distance between the television and the viewer is at least 2 m.

Food contaminated with radioactive substances

Do not eat food produced in areas contaminated with radioactive substances such as fish from the sea contaminated with radioactive substances.

Cosmic rays

Working hours of a pilot are limited to a certain period of time because the pilot is exposed to cosmic rays.

SCIENCE INFO Marie and Irene Curie are the only mother and daughter to have received three Nobel Prizes. Marie Curie received two Nobel Prizes, which are Nobel Prize in Physics in 1903 and Nobel Prize in Chemistry in 1911. Irene Curie, Marie Curie’s daughter, received her Noble Prize in Chemistry in 1935. Without realising the risks of being exposed to ionising radiation, they died of cancer caused by excessive exposure to gamma rays during their research.

Activity 8.4 To interpret data on health risks related to the absorption level of ionising radiation by the human body

• ICS • Simulation activity

Instructions 1. Work in groups. 2. Gather information from various sources on the health risks related to the absorption level of ionising radiation by the human body. 3. Discuss the health risks to the human body due to absorption of the following doses of ionising radiation in a year. (a) Doses of 10 Sv. (b) Doses in the range of 1 Sv to 10 Sv. (c) Doses in the range of 0.1 Sv to 1 Sv. (d) Doses of less than 0.1 Sv. 4. Share the outcome of your group discussion in class. 8.3.4

245

Examples of Absorption of Ionising Radiation Exceeding the Safe Level and Safety Measures that Need to be Taken

Websites

As most cosmic rays are absorbed by the atmosphere, the dose of cosmic rays on the surface of Earth is normally at a value of less than 0.2 μSv/h, which is a normal or safe level. The higher a person is from the surface of Earth, the stronger the cosmic rays he receives. Name an example of a career that involves working at high altitudes.

Safety measures for airline crew members who are exposed to cosmic rays.

http://links.andl17.com/BT_ Science_246

Airline crew members such as pilots (Photograph 8.3), stewards and stewardesses normally receive cosmic ray doses exceeding the safety level. They are exposed to strong cosmic rays in flights at high altitudes. Due to this, their working hours in the sky are limited to a certain period of time. Photograph 8.3 Pilots

Formative Practice

8.3

1. (a) What is ionising radiation? Give one example of ionising radiation. (b) What is non-ionising radiation? Give one example of non-ionising radiation. 2. Underline the correct answers. (a) The ionising power of beta radiation is (higher/lower) than the ionising power of alpha radiation but (higher/lower) than the ionising power of gamma ray. (b) The penetration power of beta radiation is (higher/lower) than the penetration power of alpha radiation but (higher/lower) than the penetration power of gamma ray. 3. (a) State two natural sources of ionising radiation. (b) State three man-made sources of ionising radiation. 4. (a) State the unit of dose rate measurement for background radiation. (b) What is 1 sievert (Sv)? (c) What is considered a safe level of background radiation dose? 5. Why does the absorption level of ionising radiation for an individual working in the aviation sector normally exceed the safety level? 6. A student watches television for 2 hours every day. Calculate the dose rate of ionising radiation received by the student after 5 days. (Dose rate of ionising radiation from television = 0.01 mSv/h) 246

8.3.4

Chapter 8: Radioactivity

8.4

Uses of Radioactive Radiation

Radioactive Radiation in Daily Life Radioactive radiation such as alpha radiation (α), beta radiation (β) and gamma ray (γ) are used in various fields in daily life as follows: Archeology and geochronology Carbon dioxide in the air is made up of carbon-12 (C-12) which is stable and carbon-14 (C-14) which is radioactive. As carbon dioxide is absorbed and released by the body of living organisms, the percentage of C-14 in the tissues of the organisms does not change. As soon as the organisms die, the amount of C-14 in their tissues begins to decline because they decay by emitting beta radiation with a half-life, T 12 , of 5 700 years. By measuring the activity of C-14, the age of the remains can be determined. This method is known as carbon-14 dating and is used by archeologists or geochronologists to determine the age of fossil and artifacts.

Photograph 8.4 Dinosaur bones

Monitoring the thickness of metal sheets (Industry) A thickness control device monitors the thickness of metal sheets in factories. A metal sheet is passed in between a beta radiation source and a beta radiation detector. If the beta radiation detector detects too much beta radiations, this means that the metal sheet is too thin. Photograph 8.5 Monitoring the thickness of metal sheets

Agriculture In agriculture, the rate at which beta radiation is emitted during the nuclei decay of phosphorus-32 (P-32) is used to determine the absorption rate of phosphate fertiliser in plants. Radioactive radiation is also used to kill beetles, control the population of pests by sterilisation, determine the best type of phosphate fertiliser, and modify the characteristics of plants. 8.4.1

Figure 8.12 Determining the absorption rate of phosphorus-32 (P-32) fertiliser

247

Defence Radioactive substances can be used in the field of defence such as the nuclear bomb. Besides heat, radioactive radiation released from the explosion of a nuclear bomb destroys almost all living things including humans and its effect exists for generations.

Today in history On 20 September 2017, Malaysia signed the ICAN agreement to ban nuclear weapons at a United Nations (UN) Conference.

Photograph 8.6 Atomic bomb explosion

Food preservation The Radura logo in Figure 8.13 is used to label food preserved using radioactive radiation such as gamma rays. Gamma rays are used in the preservation of food such as fruits to kill bacteria in the food.

Figure 8.13 Radura logo

Photograph 8.7 Preservation of food using gamma rays

Medical Gamma rays from caesium-137 (Cs-137) or cobalt-60 (Co-60) are used to kill cancer cells. Radioactive radiation is also used to determine the location of blood clots using sodium-24 (Na-24), treat tumours in the brain using technetium-99 (Tc-99), destroy germs using cobalt-60 (Co-60) and treat thyroid glands using iodine-131 (I-131). Photograph 8.8 Gamma rays used to treat cancer

248

8.4.1

Chapter 8: Radioactivity

Activity 8.5 To carry out a Gallery Walk on the use of radioactive radiation in various fields

• ICS • Technologybased activity • STEM

Instructions 1. Work in groups. 2. Gather information from the Internet, print media and other electronic media on the use of radioactive radiation in the areas of agriculture, defence, medicine, archeology or geochronology, industry and food preservation. 3. Discuss the following: (a) Types of radioactive radiation used (b) Ways of using radioactive radiation (c) Careers related to the use of radioactive radiation 4. Carry out the gallery walk activity.

Safe and Proper Handling of Radioactive Substances and Radioactive Waste Safety measures in the handling of radioactive sources and radioactive waste are shown in Figure 8.14. Storing radioactive sources or radioactive waste in containers with thick lead walls.

Wearing appropriate protective clothing when handling radioactive substances bstances

Radioactive substances are shielded with thick slabs of lead.

Safety measures when handling radioactive sources and radioactive waste

Robotic hands are used to handle radioactive substances safely.

Detecting the dose rate of radioactive radiation absorbed into the body with detectors such as radiation badges.

Disposal of radioactive waste done safely and properly

Figure 8.14 Safety measures in the handling of radioactive sources and radioactive waste 8.4.1

8.4.2

249

Appreciating the Importance of Radioactive Radiation

Websites

The importance of radioactive radiation for the well-being of humans makes us grateful to the Almighty for creating radioactive particles that have many uses to sustain life. The first artificial radioactive element, phosphorus-30 (P-30), was created by Irene Joliot-Curie, the daughter of Marie Curie. Since 1934, many artificial radioactive elements have been produced by scientists. Artificial radioactive elements cannot be produced without the radioactive particles.

Formative Practice

Handling the disposal of radioactive waste safely and properly

http://links.andl17.com/BT_ Science_250

8.4

1. State one example of the use of radioactive radiation in the following fields: (a) Archeology and geochronology (b) Medicine (c) Agriculture (d) Defence (e) Industry 2. (a) State the type of radioactive radiation used in the preservation of food. (b) How can this type of radioactive radiation preserve food? 3. Why are radioactive sources or radioactive waste kept in boxes with thick lead walls? 4. Figure 1 shows a warning symbol.

Figure 1

(a) What is the meaning of the warning symbol shown in Figure 1? (b) Name one example of a place or area which displays this warning symbol. (c) Among the three types of radioactive radiations, which is the least dangerous? Explain your answer. 5. (a) State one metal that is used to make appropriate protective clothing to handle radioactive substances. (b) State one advantage and one disadvantage of using the metal to make the protective clothing mentioned in 5(a). 250

8.4.2

Marie and Pierre Curie who succeeded in detecting radioactivity through its ionising effects (1897)

Henri Becquerel who discovered radioactivity (1896)

Wilhelm Roentgen who discovered X-ray (1895)

Chronological order

Discovery of radioactivity

Summary

becquerel (Bq), curie (Ci)

units of radioactivity

C-14, Rn-222, Th-234, U-238

Examples of radioactive substances

Decay process of unstable nucleus by emitting radioactive radiation

Natural sources such as cosmic rays, background radiation

Man-made sources such as nuclear tests and artificial radioactive elements

from

Alpha radiation, beta radiation, gamma ray and X-ray

such as

Ionising radiation

by

Formation of positive and negative ions

in the

Applying the understanding of the structure of atom and nucleus

Radioactivity

r
4UPSJOH
PG
SFTPVSDFT
r
1SPUFDUJWF
DMPUIJOH r
4IJFME
JO
MFBE
CPY r
6TF
PG
SPCPUJD
hands r
3BEJBUJPO
CBEHFT r
4BGF
BOE
QSPQFS
disposal

Safety measures

Agriculture, defence, medicine, archeology, geochronology, industry, food preservation

in fields such as

Uses of radioactive radiation

Chapter 8: Radioactivity

251

Self-reflection After studying this chapter, you are able to: 8.1 Discovery of Radioactivity Describe the history of the discovery of radioactivity. Explain with examples radioactive substances, radioactivity and the concept of half-life. 8.2 Atom and Nucleus Draw an atomic structure in a stable state. Explain the formation of positive ions and negative ions. 8.3 Ionising Radiation and Non-ionising Radiation Describe ionising radiation and non-ionising radiation. Differentiate the three types of ionising radiation in radioactive decay. Explain with examples sources of ionising radiation in the environment, natural sources and man-made sources. Discuss ways to manage the risks from exposure to natural and man-made ionising radiation. 8.4 Uses of Radioactive Radiation Communicate the use of radioactive radiation for well-being. Justify the importance of proper handling radioactive substances and radioactive waste.

Summative Practice

8

Answer the following questions: 1. Mark ‘✓’ for the correct statements and ‘×’ for the incorrect statements. (a) Wilhelm Roentgen discovered the X-ray. ( (b) Henri Becquerel used the element radium in his investigations on radioactivity. ( (c) The death of Marie Curie is caused by the exposure to gamma rays. ( 2. What is the meaning of radioactive decay? 3. Name the radioactive substance in the common salt used in the medical field. 4. Pa-234 decays to U-234 by emitting beta radiation. If the half-life of Pa-234 is 5.2 hours, what is the remaining mass of Pa-234 after 20.8 hours given its original mass is 32 g?

252

) ) )

Chapter 8: Radioactivity

5. Tables 1(a) and 1(b) show the formation of ions. Table 1(a) Magnesium ion, Mg2+

Magnesium atom, Mg Subatomic particle Number

Charge

neutron, n

12

0

proton, p

12

+12

electron, e

12

–12

The charge on magnesium atom, Mg

0

Subatomic particle Number

loses two electrons

Charge

neutron, n

12

0

proton, p

12

+12

electron, e

10

–10

The charge on magnesium ion, Mg2+

+2

Table 1(b) Fluoride ion, F –

Fluorine atom, F Subatomic particle Number neutron, n

10

Charge 0

proton, p

9

+9

electron, e

9

–9

The charge on fluorine atom, F

Subatomic particle Number Charge gains one electron

neutron, n

10

0

proton, p

9

+9

electron, e

10

–10

The charge on fluorine ion, F–

0

–1

(a) Is the ion formed in Table 1(a) a positive ion or negative ion? Explain your answer. (b) Is the ion formed in Table 1(b) a positive ion or negative ion? Explain your answer.

Focus on HOTS HOTS 6. (a) State three similarities between X-ray and gamma ray. (b) Figure 1 shows the condition of two samples of strawberries, X and Y, before and after 7 days.

Day one

After 7 days

Day one

Sample of strawberries X

After 7 days

Sample of strawberries Y Figure 1

253

(i) (ii) (iii) (iv)

Which sample has been preserved? Explain your answer. What is the radioactive radiation used to preserve food? How can this radioactive radiation preserve food? Is food preserved using this radioactive radiation safe to be consumed? Explain your answer.

7. (a) Figure 2(a) shows an activity that is normally carried out in a laboratory to study radioactive substances.

Figure 2(a)

Based on the activity in Figure 2(a), describe the safety measures taken when handling radioactive substances. (b) Figure 2(b) shows an example of the use of beta radiation in an industry. Beta radiation is used to monitor the volume of drink in bottles. Beta radiation is directed towards the passing bottle as shown in Figure 2(b). If the bottle is not filled sufficiently, the beta radiation will pass through the bottle and is then detected by a detector. The circuit attached to the detector then removes the bottle.

Beta radiation source

You are required to create a model to show the quality control system that monitors the volume of drink in bottles as shown in Figure 2(b) using the materials below.

• • • •

254

LED Empty mineral water bottle Newspaper Mirror

Radiation detector Bottle of drink Conveyor belt

Bottles removed

Figure 2(b)

THEME

4

Earth and Space Exploration

The RazakSAT-2 satellite is a satellite created entirely by local scientists. One of the uses of this satellite is in the field of defence.

Our life is affected by local weather conditions. For example, we will use an umbrella on a rainy day. What is the importance of space weather?

255

Chapter Chapte Chapt hapte hapt aptter

1 9

Space Weather

What is the structure of the Sun? What phenomena occur on the surface of the Sun? What are the effects of space weather on Earth?

Let’s study Activities of the Sun that affect Earth Space weather

256

Science Gallery

The Sun’s X9.3 class solar flare at 8.02 am on 6 September 2017 On 6 September 2017, coronal mass ejections caused disturbances to telecommunication, navigation system and electric power lines for about an hour. What are the effects of this phenomenon on daily life on Earth?

Keywords Sun Core Radiation zone Convection zone Photosphere Chromosphere Granule

Corona Solar flare Sunspot Solar cycle Solar wind Magnetosphere Prominence

257

9.1

Activities of the Sun that Affect Earth How is helium produced in the Sun?

The Sun appears as a ball of glowing gases as shown in Photograph 9.1. The Sun consists almost entirely of two types of gases, hydrogen and helium.

MEI

Photograph 9.1 The Sun

Structure of the Sun The structure of the Sun consists of the parts shown in Figure 9.1. Carry out Activity 9.1 to learn more about the structure of the Sun.

Convection zone Radiation zone

Corona Three layers that form the Sun’s atmosphere

Core

Chromosphere Photosphere

Figure 9.1 Structure of the Sun

Activity 9.1 To gather and share information on the structure of the Sun consisting of the core, radiation zone, convection zone, photosphere, chromosphere and corona

• ICS, ISS • Discussion activity

Instructions 1. Work in groups. 2. Gather information from the Internet, printed media and other electronic media on the structure of the Sun consisting of the core, radiation zone, convection zone, photosphere, chromosphere and corona. 3. Discuss and share the information gathered. 4. Present the outcome of your group discussion using multimedia presentation.

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Chapter 9: Space Weather

Phenomena that Occur on the Surface of the Sun

Science Careers A career as a solar scientist is relatively new in the field of solar energy. Besides inventing solar energy equipment, a solar scientist also studies and forecasts space weather which greatly affects daily life on Earth.

Phenomena that occur on the surface of the Sun include: • Granules • Sunspots • Solar cycles • Prominences • Solar flares • Coronal mass ejections • Solar winds Granules, Sunspots and Solar Cycle

Sunspot

The photosphere in the Sun’s atmosphere is made up of granules which appear as grainy structures. The granules are the upper part of the convection zone of the plasma which is extremely hot with a temperature as high as 5 800°C. The average diameter of a granule is about 1 000 kilometres! Sunspots are the dark regions seen on the surface of the Sun as shown in Figure 9.2. Sunspots appear dark because their temperatures are lower than their surrounding areas which are made up of granules. Sunspots are the locations of very large eruptions in the photosphere. This phenomenon may last more than a week. Sunspots are phenomena that always exist in pairs or groups. The activity of the sunspots seems to appear and disappear according to a cycle that lasts 11 years known as the solar cycle. Figure 9.3 shows the position of sunspots in the photosphere since 1875.

Granule

Figure 9.2 Granules and sunspots

60°N 30°N Equator 30°S 60°S 1870

1880

1890

1900

1910

1920

1930

1940

1950

1960

1970

1980

1990

2000

2010

2020

(Source: NASA)

Figure 9.3 Position of sunspots on the surface of the Sun 9.1.1

259

Prominence A prominence shown in Photograph 9.2 is a huge loop or arched column of glowing gases over the sunspot. Prominences can reach heights of hundreds of thousands of kilometres and may last for several days or months. Prominences that are very strong can throw out matter from the Sun into space at speeds ranging from 600 km s-1 to more than 1 000 km s-1.

Photograph 9.2 Prominence

Solar Flares A solar flare shown in Photograph 9.3 is a column of large amounts of charged gases erupting from the Sun and often occurs near sunspots. Solar flares are strong and spectacular explosions of gases. Solar flares attain their maximum brightness level within a few seconds or minutes and then become dim after a few minutes or hours. Solar flares spout charged gas particles at high speeds into outer space. The light from solar flares which is at the speed of light takes eight minutes to reach Earth while the charged gas particles take tens of minutes. These charged gas particles often collide with atoms and molecules in Earth’s atmosphere to produce a stunning light display in the sky known as aurora which uniquely occurs only in the air space around Earth’s poles.

Photograph 9.3 Solar flare

Coronal Mass Ejections

Photograph 9.4 Coronal mass ejection

Watch a video on prominences, solar flares and coronal mass ejections. 5 *(

.

,

:

A coronal mass ejection shown in Photograph 9.4 is a huge cloud of plasma that erupts from the Sun and often occurs together with solar flares which are huge and strong. A coronal mass ejection is an ejection of magnetic gas particles. The coronal mass ejection spouts magnetic particles at high speeds into outer space and appears like an expanding cloud. These magnetic particles from the coronal mass ejection take three days to reach Earth. Like the charged gas particles in solar flares, the magnetic gas particles also react with atoms and molecules in Earth’s atmosphere to produce aurora.

     7(

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9.1.1

Chapter 9: Space Weather

Solar Wind Particles in plasma such as electrons, protons and alpha particles that erupt from the Sun to outer space travel together at high speeds known as solar wind as shown in Photograph 9.5. Solar wind also carries the interplanetary magnetic field along with it. The speed of solar wind is supersonic with values ranging from 250 km s-1 to 750 km s-1. However, the speed, temperature and density of the solar wind changes along the course of its movement.

Solar wind

Earth

Photograph 9.5 Solar wind (in yellow)

Earth’s Magnetosphere and its Importance Shape of Earth’s Magnetosphere

Magnetosphere

Earth

Solar wind

Magnetosphere

(a) Earth’s magnetic field

(b) Earth’s magnetosphere

Figure 9.4 Shape of Earth’s magnetosphere

Compare and contrast the pattern of magnetic field lines between Earth’s magnetic field and Earth’s magnetosphere. Even though both of these patterns of magnetic field lines are not fixed, the pattern of Earth’s MARVELS OF magnetic field lines changes slightly while the pattern of SCIENCE the magnetic field lines in the magnetosphere changes a lot Animation that shows based on the interaction between solar wind and Earth’s the relationship between magnetic field. magnetosphere and solar wind. Definition of Earth’s Magnetosphere Earth’s magnetosphere is defined as a region in outer space surrounding Earth where the magnetic field in Earth’s magnetosphere is a combination of Earth’s magnetic field (as the prime magnetic field) and the magnetic field in the region in outer space as shown in Figure 9.4(b). 9.1.2

http://links.andl17.com/BT_ Science_261

261

Formation of Earth’s Magnetosphere Magnetosphere is formed by the interaction between the magnetic field brought by the solar wind and Earth’s magnetic field. As the number and energy of particles brought by the solar wind change, the shape of the magnetosphere also changes. Importance of Earth’s Magnetosphere The importance of magnetosphere is to protect Earth from the adverse effects caused by dangerous particles from the Sun or other bodies in the Universe.

Solar wind (in yellow)

Magnetosphere (magnetic field lines in blue)

Earth protected by magnetosphere

Magnetosphere (magnetic field lines in blue)

Figure 9.5 Protection from Earth’s magnetosphere

The magnetosphere: • functions as a biological shield to protect life on Earth from the adverse effects of solar wind • blocks charged particles such as electrons, protons and alpha particles in the solar wind from reaching Earth. Excessive numbers of charged particles in Earth’s atmosphere will disrupt telecommunication, navigation system and electric power lines • reduces the pressure exerted by solar wind on Earth’s atmosphere

Activity 9.2 To gather and share information on the definition, formation, shape and importance of the magnetosphere

• ICS, CPS, ISS • Discussion activity

Instructions 1. Work in groups. 2. Gather information from the Internet, printed media and other electronic media on the definition, formation, shape and importance of the magnetosphere. 3. Discuss and share the information gathered. 4. Brainstorm on the condition of Earth without the magnetosphere. 5. Present the outcome of your group discussion using multimedia presentation.

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9.1.2

Chapter 9: Space Weather

Formative Practice 9.1 1. 2. 3. 4. 5.

State three structures of the Sun that form the Sun’s atmosphere. State three phenomena that occur on the surface of the Sun where charged gases erupt. Define Earth’s magnetosphere. What influences the shape of the magnetosphere? Name one object in the Solar System that has the same shape as solar wind.

9.2

Space Weather

Space Weather and its Effect on Earth

Websites

Space weather is defined as the phenomena that occur: • on the surface of the Sun such as solar flares, prominences, sunspots and coronal mass ejections • in space such as solar wind, solar radiation storm and geomagnetic storm

Space weather

http://links.andl17.com/BT_ Science_263

Study Figure 9.6. Then, carry out Activity 9.3.

Sunspot

Magnetic field line

Coronal mass ejection

Solar wind Solar radiation storm

Earth Magnetic field line

Earth

Solar flare Geomagnetic storm

Figure 9.6 Space weather 9.2.1

263

Activity 9.3 To gather and share information on the definition of space weather and its effects on Earth

• ICS, CPS, ISS • Discussion activity

Instructions 1. Work in groups. 2. Gather information from the Internet, printed media and other electronic media on the definition of space weather and effects on Earth such as the formation of the aurora, disturbances to telecommunication, navigation system as well as electrical power lines. Space storms http://links.andl17.com/ BT_Science_264_1

Effects of geomagnetic storm, solar radiation storm and disturbances of radio transmission http://links.andl17.com/ BT_Science_264_2

3. Discuss and share the information gathered. 4. Present the outcome of your group discussion using multimedia presentation.

Interpretation of Data on Space Weather Data on space weather is used or analysed to: • forecast when coronal mass ejections occur in the Sun • determine the reasons for the occurrence of solar flares and coronal mass ejections on the surface of the Sun

Activity 9.4 To interpret data on space weather Instructions 1. Work in groups. 2. Gather information or data on space weather from the Internet, printed media and other electronic media.

• ICS, CPS, ISS • Discussion activity

Sources of solar wind in relation to solar cycle http://links.andl17.com/BT_Science_264_3

3. Interpret data on space weather by relating the number of sunspots or solar cycles with the increase in coronal mass ejections and solar winds. 4. Present your group’s interpretation of space weather data using multimedia presentation.

264

9.2.1

Chapter 9: Space Weather

Formative Practice 9.2 1. What is the definition of space weather? 2. State four examples of the effects of space weather on Earth. 3. What is the relationship between the number of sunspots and the increase in coronal mass ejections?

Summary Space weather is influenced by

Sun

Solar wind

Phenomena on the surface of the Sun

which determines the shape of the produce effects such as

Structure

Core, radiation zone, convection zone, photosphere, chromosphere, corona

Phenomena on its surface

Magnetosphere

such as

which

Granules, prominences, solar flares, solar cycles, sunspots, coronal mass ejections, solar winds

Protects Earth from

Adverse effects from harmful particles in solar winds

Formation of aurora, disturbances to telecommunication, navigation system as well as electric power lines which shows

The relationship between the number of sunspots (solar cycle), and the increase in coronal mass ejections and solar winds

265

Self-reflection After studying this chapter, you are able to: 9.1 Activities of the Sun that Affect Earth Explain the structure of the Sun and phenomena that occur on the Sun's surface by drawing. Justify the importance of Earth’s magnetosphere. 9.2 Space Weather Communicate space weather and its effects on Earth.

Summative Practice

9

Answer the following questions: 1. Figure 1 shows the structure of the Sun. A:

D:

B:

E:

C: F:

Figure 1

Name the structures labelled A to F using the following words: Photosphere

Corona

Chromosphere

Core

Convection zone

Radiation zone

2. What is the duration of one solar cycle? 3. State the phenomenon related to solar cycle.

266

Chapter 9: Space Weather

4. State three examples of equipment or service used daily which is disrupted by solar winds. 5. What would happen to the condition of Earth if there is no magnetosphere? Explain your answer.

Focus on HOTS 6. Earth’s magnetosphere shown in Figure 2, is a region in space which protects Earth.

Figure 2

The shape of Earth's magnetosphere is produced by the interaction between Earth’s magnetic field and solar wind. Magnetic field lines from other planets in the Solar System are represented by white lines while Earth’s magnetic field lines are represented by red lines as shown in Figure 2. You are required to create a model of the magnetosphere using the following materials:

• • • • •

Green-coloured plastic bag White thread Red thread Polystyrene cup with a convex cover Plasticine

Sketch the model of the magnetosphere. Explain how the model functions.

267

Chapter Cha Chapter Chapte hapte pte p ter er

1 10 0

Space Exploration

How can the model of the Solar System be improved from time to time? Give three examples of technological invention devices applied in space exploration. Give an example of the use of remote sensing technology in field of geology.

Let’s study Development in astronomy Development of technology and its application in space exploration 268

Science Gallery

International Space Station, ISS The International Space Station n (ISS) is a station that facilitates international nal research tation in space. The function of this station is to carry out research in space e and monitor space. Dato’ Dr Sheikh Muszaphar Shukor Al Masrie bin Sheikh Mustapha is the first astronaut from Malaysia to carry out experiments in space from 10 October to 21 October 2007.

Keywords Geocentric Heliocentric Kepler’s Law Ellipse Focal point Rocket

Satellite Space probe Remote sensing Geology Disaster management Space Telescope

269

10.1

Development in Astronomy

Historical Development of the Solar System Model Study Figure 10.1. Then, carry out Activity 10.1.

History of the Solar System Model

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270

10.1.1

Chapter 10: Space Exploration

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10.1.1

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271

Activity 10.1 To understand the development of the Solar System models built by Ptolemy, Copernicus and Kepler

• ICS • Discussion Activity

Instructions 1. Work in groups. 2. Carry out active reading by visiting websites or going on a study tour to the National Planetarium to gather information on the development of the Solar System models built by: (a) Ptolemy (b) Copernicus (c) Kepler Examples of websites are as follows: Watch these sections of the video 3.01 Historical Solar System Models 3.02 Current Solar System Model http://links.andl17.com/ BT_Science_272_1

Historical attempts to model the Solar System (Take a challenge) http://links.andl17.com/ BT_Science_272_2

History of the Solar System model http://links.andl17.com/BT_Science_272_3

3. Discuss and present to the class how knowledge gained through scientific research is the product of human effort to obtain rational explanations about natural phenomena. 4. Present the outcome of your group discussion using multimedia presentation.

Formative Practice 10.1 1. Name the Solar System model built by the following astronomers: (a) Ptolemy (b) Copernicus (c) Kepler 2. Compare and contrast the Solar System models built by Ptolemy and Copernicus. (a) Similarities (b) Differences 3. Compare and contrast the Solar System models built by Copernicus and Kepler. (a) Similarities (b) Differences 272

10.1.1

Chapter 10: Space Exploration

10.2

Development of Technology and its Application in Space Exploration

Development in Space Exploration Figure 10.2 shows part of the early history of space exploration in terms of technology development and missions in space exploration. 2011: Construction of International Space Station (ISS) completed

1981: First flight of US space shuttle – Columbia

1989: First Neptune flyby – US Voyager 2

1973: First Jupiter flyby – US Pioneer 10

11th century: Chinese invented gunpowder and used primitive rockets in battles

2000: Malaysia’s first microsatellite TiungSAT-1 launched

2002: National Space Agency (Agensi Angkasa Negara) established

1990: US launched Hubble Space Telescope from space shuttle Discovery

1969: First human to set foot on the Moon – Neil Armstrong, US Apollo 11

1609: First telescope used in the field of astronomy by Galileo Galilei

1996: Malaysian satellites MEASAT 1 and 2 launched

1961: First human to orbit Earth – Yuri Gagarin, aboard USSR Vostok 1

1957: First satellite – USSR Sputnik 1

Figure 10.2 Some of the events related to the development of technology in space exploration 10.2.1

273

Applications of Technology in Space Exploration and their Importance Space Telescope Figure 10.3 shows the development of the telescope.

The astronomical sextant is used to measure the altitude of stars

Hubble space telescope was placed in an orbit 500 km from the surface of Earth

Galileo’s Telescope became the most widely used astronomical instrument

The Spitzer space telescope detects very distant activities in space.

Apart from optical telescopes, radio telescopes are also used to detect radio waves from space.

Figure 10.3 Space telescopes

Rocket Rockets are used widely in space explorations. When the fuel in a rocket burns, hot gases are released at high speed through the bottom of the rocket. The release of these gases produces a force which pushes the rocket upwards.

Vostok K Redstone Atlas Voskhod Titan II Soyuz

Saturn 1B

Saturn V

STS

Long March 2F

Falcon 9

SLS

Angara 5P

Atlas V

Photograph 10.1 Rockets used to send humans to space

Based on Photograph 10.1, which rocket was used to send astronauts to the Moon? 274

10.2.1

Chapter 10: Space Exploration

Satellite The first satellite, Sputnik 1 was sent to outer space in 1957. How many satellites are orbiting around Earth today? Which country has the largest number of satellites?

Websites Satellite launch

Photograph 10.2 Weather satellite GOES-16 gathers data on solar flares

Space Probe A space probe is a spacecraft that gathers information and sends it back to Earth. Space probes do not orbit Earth like satellites but travel further into and out of the Solar Photograph 10.3 Space System. Space probes carry probe Cassini cameras and remote sensing instruments as well as radio transmitters and receivers for the purpose of communicating with scientists on Earth.

http://links.andl17.com/BT_ Science_275

MARVELS OF

SCIENCE

In 2017, space probe Cassini was still active orbiting Saturn even after 20 years in space.

Remote Sensing Remote sensing is a method of gathering and recording information from a distance. In Malaysia, remote sensing instruments are fitted to TiungSAT-1 to receive or detect visible, ultraviolet and infrared lights produced by objects on the surface or below the surface of Earth. The information gathered by TiungSAT-1 is then sent to two data receiving stations at the National Planetarium Station, Federal Territory of Kuala Lumpur and the Mission Control Station (MCGS), Bangi, Selangor. Photograph 10.4 shows the pattern and movement of clouds taken from TiungSAT-1’s remote sensing camera. What is the use of the information obtained from this photograph? Remote sensing technology is used in various fields in daily life as follows: • Agriculture – To detect suitable regions for agricultural development • Geology – To detect locations such as mineral sources, mass depletion and land depletion Photograph 10.4 A picture of the pattern and movement of • Disaster management – To identify pollution and forest fires clouds • Defence – To detect intrusions of enemy ships, aircraft and vehicles 10.2.1

275

Activity 10.2 To understand the development of technology in space exploration

• ICS

• Discussion Instructions activity 1. Work in groups. 2. Carry out active reading by visiting websites or going on a study tour to the National Planetarium, MACRES and National Space Agency to gather information on the development of technology in space exploration in: (a) early history of space exploration (b) the construction of rocket, satellite and space probe (c) remote sensing used in agriculture, geology, disaster management and defence 3. Discuss and present the development and technological applications in space exploration and their importance. 4. Present the findings of your group discussion using multimedia presentation.

Activity 10.3 To debate the issue of continual space exploration

• ISS, CPS • Project-based activity

Instructions 1. Work in groups. 2. Gather information from the Internet, printed media and other electronic media on the importance of space exploration in the local and global context. 3. Share and discuss the gathered information. 4. Debate the issue of continual space exploration in the local and global context.

Formative Practice 10.2 1. Name the first technological device used in space exploration. 2. Study Figure 1. (a) What is Discovery? (b) What is Hape? 3. (a) Name the technology used to take aerial photographs. (b) What is the importance of taking aerial photographs during floods? 4. What is the role played by the Malaysian Remote Sensing Agency (MACRES)? 276

Hape

Discovery

Figure 1 10.2.1

10.2.2

Sun and other planets revolving in circular orbits

Earth and other planets revolving in circular orbits

with

Earth and other planets revolving in elliptical orbits

with

Sun as the centre of the Solar System

Sun as the centre of the Solar System

Earth as the centre of the Solar System

with

Kepler

Copernicus

Ptolemy

by

Building of solar system models

such as

Development in astronomy

Summary

Agriculture, geology, disaster management, defense

Remote sensing used in

Gather information on space weather, remote sensing, telecommunication, defence

used to

used to

Send spaceships, satellites, space probes to space

Satellite

such as

used to

Space probe

Gather and send information on distant bodies in space

Development of technology and its application in space exploration

Rocket

is infuenced by

Space exploration

Chapter 10: Space Exploration

277

Self-reflection After studying this chapter, you are able to: 10.1 Development in Astronomy Explain the historical development of the Solar System model by drawing. 10.2 Development of Technology and its Application in Space Exploration Communicate the importance of the development of technology and its application in space exploration. Justify the need to continue space exploration.

Summative Practice

10

Answer the following questions: 1. Figure 1 shows the Spitzer space telescope.

Figure 1

Mark ‘✓’ for the correct statements and ‘×’ for the incorrect statements. (a) The Spitzer space telescope is located on the surface of Earth. (b) The Spitzer space telescope ‘observes’ better than ordinary telescopes. (c) The Spitzer space telescope is used to take photographs of Earth’s surface. (d) The Spitzer space telescope is used as a remote sensing equipment.

278

Chapter 10: Space Exploration

2. Match the Solar System model to the astronomer who built it. Solar System model

Astronomer

(a) Earth is at the centre of the Solar System and the Sun revolves around Earth in a circular orbit.

Copernicus

Kepler (b) The Sun is at the centre of the Solar System and Earth revolves around the Sun in an elliptical orbit.

Ptolemy

3. How can knowledge about astronomy be acquired through scientific investigation? 4. Why are space probes not used to send astronauts into space? 5. Figure 2 shows a space probe sent to Saturn.

Figure 2

(a) What is the function of this space probe? (b) State one example of a phenomenon that occurs on the surface of the Sun that might destroy the space probe. (c) State the source of energy used by the space probe. 6. State two examples of the use of remote sensing technology in the following fields: (a) Agriculture (b) Geology (c) Disaster management (d) Defence 279

Focus on HOTS HOTS 7. Figure 3 shows a rocket.

Figure 3

(a) What is a rocket? (b) What is the function of rocket in space exploration? (c) Explain one misuse of rocket in our daily life. 8. Astronomers have successfully discovered three planets revolving around the TRAPPIST-1 star which are suitable for all life on Earth. As these three planets are extremely far, a special spacecraft needs to be invented to transfer life on Earth to these planets. You are required to invent a model of the spacecraft using the following materials:

• • • •

280

Cardboard Cellophane tape Black plastic sheet Aluminium foil

ANSWERS CHAPTER 1 Stimuli and Responses Activity 1.1 (p. 7) Questions 1. Stimulus:

Seeing your partner let go of the ruler. Response: Catching the ruler using your thumb and index finger. This is a voluntary action because it is a conscious action and is made according to the will of the individual who received the stimulus and is controlled by the brain. 2. The distance moved by the ruler shows the time taken by the student to catch the ruler. The shorter the distance, the faster the reaction time. 3. Different students usually have different reaction time. Besides this, the reaction time of an individual is not constant. 4. In the daily life of humans, reaction time plays an important role to coordinate and control organs and body parts so that they function harmoniously and efficiently.

Activity 1.3 (p. 9) Questions 1. Stimulus:

Intensity of light that enters the eye. Response: Change in size of the pupil. This is an involuntary action because this action occurs spontaneously without any conscious control or prior thoughts. 2. The higher the intensity of light, the smaller the size of the pupil. 3. This response can help protect the eye from injury.

Brain Teaser (p. 10) Muscular system

Formative Practice 1.1 (p. 10) 1. Central nervous system and peripheral nervous system 2. (a) Voluntary actions are conscious actions, carried out according to the wishes of a person and are controlled by the brain. Examples of controlled actions are reading, writing, speaking, eating, drinking, walking, running, exercising and singing. (b) Involuntary actions are spontaneous actions that happen without being realised or thought of beforehand. Examples of uncontrolled actions are heartbeat, breathing, peristalsis, secretion of saliva and sneezing. 3. Injured nerve cells in the human brain are unable to interpret impulses from affectors and cannot send impulses to effectors. Due to this, a person who sustained brain injury is unable to carry out voluntary or involuntary actions involving the brain. 4. The network of nervous system of humans functions to control and coordinate organs and body parts so as to carry out processes in the body and daily activities.

Brain Teaser (p. 15) Excess mucus is produced when a person suffers from a cold. This excess mucus will obstruct receptors from being stimulated by chemical substances in the air entering the nasal cavity.

Brain Teaser (p. 16) A blind person uses the sensitivity of the fingertip to read Braille and sensitivity of the hand to detect vibrations of the walking stick when it hits objects to detect any nearby obstructions.

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Activity 1.6 (pp. 19, 20) Questions 1. Tip of index finger. It has the largest number of receptors. 2. Elbow. It has the least number of receptors. 3. Touch receptor. 4. Number of touch receptors and thickness of epidermis.

Activity 1.7 (p. 21) Questions 1. To ensure no other solutions remain and only the taste of one solution is detected during each attempt. 2. All areas of the tongue can detect all tastes of the solutions. 3. Both sides of the tongue are most sensitive towards taste because they have a large number of taste receptors. 4. The middle part of the tongue is least sensitive to taste because it has a small number of taste receptors. 5. The front part of the tongue is more sensitive to sweet taste, the sides of the tongue are more sensitive to sour and sweet tastes, the back part of the tongue is more sensitive to bitter taste and the middle part of the tongue is more sensitive to umami.

substances in hot food also evaporate to form vapour which enters the nasal cavity and stimulates the smell sensory cells. The combination of sense of taste and sense of smell causes hot food to taste better.

Formative Practice 1.2 (p. 29) 1. (a) Cornea (b) Pupil (c) Retina (d) Brain 2. Semicircular canals 3. At the upper part of the nasal cavity 4. Sweet, sour, salty, bitter, umami 5. Number of receptors and thickness of skin epidermis 6. (a) Five types of taste, touch, pain, hot objects, cold objects, and pressure. (b) Five types of taste can be detected by taste receptors in the taste buds of the tongue. The tongue is protected by skin that has touch, pain, heat, cold and pressure receptors. Therefore, it can detect touch, pain, hot objects, cold objects and pressure.

Experiment 1.1 (pp. 30 – 33)

Activity 1.8 (pp. 22, 23)

A. Questions (p. 31) 1. Light 2. Shoot of the plant 3. The shoot of the plant shows positive phototropism because shoots of plants grow towards the direction of light.

Questions 1. Without the nose being pinched. 2. Taste of the cordial drink is more easily detected using a combination of sense of taste and sense of smell. 3. So that your partner does not use sense of sight to determine the taste of the cordial drink based on the colour such as purple for taste of grape, orange for taste of orange, yellow for taste of mango and red for taste of strawberry. 4. In addition to chemical substances in food which dissolve in saliva and stimulate the taste buds, chemical

B. Questions (p. 32) 1. So that light cannot influence the growth of the seedlings. 2. (a) Grow upwards against the direction of gravity. (b) Grow downwards in the direction of gravity. 3. Roots of plants show positive geotropism because the roots of plants grow towards the direction of gravity. Shoots of plants show negative geotropism because shoots of plants grow against the direction of gravity.

Brain Teaser (p. 22) No. After the tongue is cleaned, the tongue will become more sensitive.

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C. Questions (p. 33) 1. Water 2. Roots of the plant 3. Absorbs water and moisture in the air in beaker Y 4. The roots of the plants show positive hydrotropism because they grow towards water.

Formative Practice 1.3 (p. 35) 1. (a) Tropism is a directed response of plants towards stimuli coming from a certain direction. (b) (i) Thigmotropism (ii) Geotropism (iii) Phototropism 2. (a) (i) Shoots (ii) Roots (iii) Tendrils or winding shoots (b) Positive hydrotropism allows roots to obtain water and dissolved mineral salts to survive. 3. Similarity: Tropism and nastic response are responses of plants towards stimuli. Difference: Tropism is the directed response of plants towards stimuli while nastic response is the response towards stimuli without considering their direction.

cat received by both of Azman’s ears are the same. The brain then informs Azman the direction of the cat making the sound.

Summative Practice 1 (pp. 41 – 43) 1. (a) (b) (c) (d) 2. P: Q: R: 3. (a) (b) (c) (d) 4. (a) (b)

5. (a) (b)

Brain Teaser (p. 37) The blind have a more sensitive sense of hearing. They make use of sound to detect location and estimate distance of nearby objects.

(c)

Formative Practice 1.4 (p. 39) 1. Stereoscopic and monocular vision. 2. Location of eyes on the head. 3. Primary consumer has monocular vision. Monocular vision has a wide field of vision and allows it to detect predators coming from various directions. 4. Stereophonic hearing allows us to determine the direction of sound accurately. 5. Azman uses his stereophonic hearing to determine the cat’s location. The time and loudness of the sound made by the

6. (a)

(b)

×  × 

Brain Spinal cord Peripheral nerve Changes in the size of the pupil of the eye. Intensity of light which enters the eye. The lower the intensity of light directed towards the eye, the larger the size of the pupil of the eye. During a solar eclipse, the bright rays of the sun will enter the eye and damage the cells of the retina. Sound → Earlobe → Ear canal → Eardrum → Ossicles → Oval window → Cochlea → Auditory nerve → Brain Light → Cornea → Aqueous humour → Pupil → Eye lens → Vitreous humour → Retina → Optic nerve → Brain X: Touch receptor Y: Pain receptor Fingertip is more sensitive towards touch stimuli compared to the palm of the hand. Fingertip has a thinner layer of epidermis and more touch receptors compared to the palm of the hand. Agree. The tongue is a sensory organ that has receptors known as taste buds on the surface of the tongue which is protected by skin epidermis. The sense of smell helps us to detect danger such as leakage of gas that might occur in the science laboratory. For example, we can detect the presence of dangerous gases such as chlorine and ammonia from their smell. Dogs have a very sensitive sense of smell because they have more sensory cells for smell than human

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and are more efficient to analyse smell than human. 7. (a) – Positive phototropism – Positive hydrotropism (b) Positive phototropism ensures shoots and leaves of plants obtain sufficient sunlight to make food through photosynthesis. Positive hydrotropism allows roots of plants to grow towards water so that they can absorb water to enable plants to carry out photosynthesis. 8. (a) Stereoscopic vision (b) The eagle is a predatory animal. Stereoscopic vision helps the eagle to hunt its prey by accurately determining the location of its prey. 9. Explanation: – Fill the transparent plastic bottle with water. – It functions as a convex lens. – Place it on top of the newspaper. – Read the newspaper through it.

3. To provide sufficient oxygen and eliminate carbon dioxide from the air. 4. (a) (i) Rib cage (ii) Diaphragm (iii) Trachea and bronchus (iv) Lungs (b) – A thin rubber sheet stretches more easily compared to a thick rubber sheet. – Therefore, a thin rubber sheet is more easily pulled downwards or pushed upwards. (c) (i) Breathing in or inhaling (ii) Exhaling (d) – The structure or volume of the glass jar which represents the rib cage is fixed when the thin rubber sheet is pulled downwards or pushed upwards. – While the structure and volume of the rib cage changes during the processes of inhaling or exhaling.

Formative Practice 2.2 (p. 56)

CHAPTER 2 Respiration Experiment 2.1 (pp. 50 – 52) Question (p. 51) – The water level in the gas jar containing inhaled air is higher. – Composition of oxygen in inhaled air is higher than that in exhaled air. – Burning of candle using the oxygen in the gas jar causes water to enter to fill the space originally filled with oxygen. Question (p. 52) – Limewater in the conical flask where exhaled air was passed through turns cloudy. – Carbon dioxide in the exhaled air reacts with the limewater.

Formative Practice 2.1 (p. 53) 1. (a) Trachea (b) Bronchus (c) Bronchiole 2. (a)  (b) × (c) × (d) ×

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1. Difference in concentrations of oxygen gas in the alveolus and blood capillaries. 2. (a) When concentration of oxygen is high, haemoglobin will combine with oxygen chemically to form oxyhaemoglobin which is unstable. (b) When concentration of oxygen is low, oxyhaemoglobin will decompose to form haemoglobin and oxygen. 3. Glucose + oxygen → carbon dioxide + water + energy 4. Efficiency of exchanging oxygen in the human body decreases at high altitudes. Concentration of oxygen in the air at high altitudes is low. Due to this, the rate of diffusion of oxygen from the alveolus into the blood capillaries is also low. 5. – Thickness of wall of alveolus and blood capillary is one cell thick – The wall of alveolus is moist – Alveolus with large surface area – Dense network of capillaries covering alveolus

Brain Teaser (p. 57) Forests help to maintain the balance of oxygen and carbon dioxide in the atmosphere.

Brain Teaser (p. 58) Smoking endangers the health of the smoker and everyone in the vicinity of the smoker.

Brain Teaser (p. 59)

to this, the health of all systems in the body especially the respiratory system is maintained. 5. Not smoking, frequent exercise

Electric buses do not emit exhaust gases. Therefore, air pollution can be reduced.

Brain Teaser (p. 67)

Experiment 2.2 (pp. 62, 63)

Brain Teaser (p. 71)

Questions 1. Cigarette tar 2. Cigarette smoke is an acidic substance because it changes the purple colour of litmus solution to red. 3. Ammonia, stearic acid, methane, butane, methanol, toluene, cadmium, arsenic, acetone

Air is always moving from one region to another region. Therefore cooperation from the global society is required. Prevention in only one region would not be effective.

Formative Practice 2.3 (p. 63) 1. (a) Tar, pollen, haze and dust (b) Sulphur dioxide, carbon monoxide, nitrogen dioxide 2. Pollen 3. (a) Pain during breathing (b) Blood in phlegm (c) Frequent shortness of breath (d) Wheezing sound when breathing 4. Lung cancer, emphysema, bronchitis, (any two) 5. A person who does not smoke but who breathes in cigarette smoke from smokers nearby.

Formative Practice 2.4 (p. 66) 1. (a) Gills (b) Trachea (c) Moist outer skin 2. Thin outer skin of frogs, dense network of blood capillaries under the layer of skin, very permeable to respiratory gases and moist. 3. Body cells of insects have a direct connection with the respiratory surface. Oxygen that enters the tracheole diffuses directly into the cells while carbon dioxide diffuses out. 4. When we exercise, our rate of respiration increases. Higher rate of transport of oxygen to body cells and higher rate of elimination of carbon dioxide from body cells result in healthier body cells. Due

Organ of gaseous exchange.

Formative Practice 2.5 (p. 72) 1. Leaves, stem, aerial roots 2. P: Guard cell Q: Stomatal pore 3. (a) Stomata open during the day. Water diffuses into guard cells through osmosis causing the guard cells to bend and open the stoma. (b) Stomata close at night. Water diffuses out of guard cells through osmosis causing the guard cells to straighten up and close the stoma. (c) Stomata are closed on hot days to prevent excessive loss of water through transpiration. 4. Polluted air will reduce the amount of sunlight reaching the plants and reduce the rate of photosynthesis. Hence, the growth and survival of plants will be jeopardised.

Summative Practice 2 (pp. 74 – 77) 1. (a) (b) (c) 2. P: Q: R: 3. (a) (b) (d) 4. (a) (b) 5. (a)

Alveolus Bronchus Nasal cavity Trachea Bronchus Alveolus

  

higher lower Haemoglobin transports oxygen from the red blood cell to body cells. (b) Oxyhaemoglobin easily decomposes into haemoglobin and oxygen when

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6. (a)

(b)

7. (a)

(b)

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it reaches body cells so that oxygen can diffuse into the cells. Azura may be allergic to pollen. In Spring, more pollen is released from anthers. When Azura inhales air containing pollen, there is a higher risk of her getting an asthma attack. Any place that is hazy and dusty. Examples: industrial areas, construction sites and others. Haze and dust also cause asthma attacks in asthma patients. – Thickness of the wall – Moisture of the wall – Surface area – Network of capillaries (i) Asthma Symptom: Shortness of breath Cause: Excessive release of mucus on the surface of alveolus reduces the surface area and rate of gaseous exchange in the alveolus thereby causing shortness of breath. (ii) Bronchitis Symptom: Shortness of breath Cause: Inflammation of the bronchus in bronchitis patients caused by tar and irritants in cigarette smoke reduces the rate of movement of air from the nose to the lungs through the bronchus. This causes bronchitis patients to be frequently breathless. (iii) Emphysema Symptom: Shortness of breath Cause: The alveolus in emphysema patients is damaged by dangerous substances in the air such as irritants in cigarette smoke. Hence, the surface area for

gaseous exchange in the alveolus is reduced causing shortness of breath. 8. – Stop smoking. To avoid harmful substances found in cigarette smoke from entering the lungs and harming the respiratory system. – Avoid places with polluted air. To avoid inhaling air that contains harmful substances such as cigarette tar, carbon monoxide, sulphur dioxide, nitrogen dioxide, haze, dust and pollen which are harmful to the respiratory system. – Have proper exercise and lead a healthy lifestyle. To maintain a healthy respiratory system. 9. Users at the waiting areas will become passive smokers if there are other users nearby who smoke. This is harmful to their health. 10. (a) Gaseous exchange is through diffusion into cells. (b) The respiratory system of insects is more effective than the human respiratory system. (c) Gaseous exchange through direct diffusion into the cells of insects is easier, quicker and more efficient compared to gaseous exchange through transport of gases by blood in the human body. 11. (a) Carbon monoxide (b) When the air in a car which contains carbon monoxide is inhaled, the carbon monoxide combines with haemoglobin to form carboxyhaemoglobin. Therefore, a person in the car will not have sufficient oxygen supply which can be fatal. 12. (a) (i) 3.0 dm3 (ii) 2.5 dm3 (b) (i) 4.0 dm3 (ii) 3.0 dm3 (c) The more active the activity that is performed, the larger the maximum volume of the lungs. From the graphs

in Figures 3(a) and 3(b), the volume of air in the lungs of runners X and Y increases when they are running. (d) Runner Y. Cigarette smoke which damages the alveolus will reduce the maximum volume of air in the human lungs. The maximum volume of air in the lungs of runner Y is less, therefore runner Y is a smoker. (e) Increase in the maximum volume of the lungs increases the rate of respiration because the rate of gaseous exchange in the lungs is increased.

CHAPTER 3 Transportation Formative Practice 3.1 (p. 82) 1. The function of the transport system is to carry substances needed by cells into organisms and eliminate waste products from organisms to the outside surroundings. 2. Examples of substances needed by cells: Oxygen, nutrients Examples of waste products eliminated from cells: Carbon dioxide, water, urea 3. Importance of the functions of transport system in organisms are as follows: – Transport system provides substances needed by cells such as oxygen and nutrients which are used to produce energy through the process of cellular respiration. – Transport system provides substances needed by plant cells such as carbon dioxide and water which are used to carry out photosynthesis. – Transport system also eliminates toxic waste products from the cells of organisms to the surroundings. 4. If the transport system of an organism cannot function well, – cellular respiration cannot be carried out. Without energy, living process cannot occur in the organism. – food cannot be made by green plants through photosynthesis. Without food, plants and animals will die.

– toxic waste products that fail to be eliminated from the body to the outside surroundings will poison and kill the organism.

Activity 3.2 (p. 84) Fish – Fish has a single blood circulatory system where blood flows through the heart only once in one complete cycle to the all the other parts of the body. – Fish’s heart has one atrium and one ventricle. – Deoxygenated blood flows out from the heart to the gills where gaseous exchange occurs in the capillaries of the gills changing deoxygenated blood to oxygenated blood. – Oxygenated blood flows from the heart to the whole body, changes into deoxygenated blood and flows back into the heart. Amphibians – Amphibians have an incomplete double circulatory system where blood flows through the heart twice in one complete cycle to the whole body. – Amphibian’s heart has two atriums and one ventricle. – Deoxygenated blood flows out from the amphibian’s heart to the lungs and skin where gaseous exchange occurs in the blood capillary walls in the lungs or under the skin changing deoxygenated blood to oxygenated blood. – Oxygenated blood flows from the heart to the brain and a mixture of oxygenated and deoxygenated blood flows to all other parts of the body except the lungs. Oxygenated blood changes into deoxygenated blood and flows back into the heart. Reptiles – Reptiles have an incomplete double circulatory system where blood flows through the heart twice in one complete cycle to the whole body. – Reptile’s heart has two atriums and one ventricle with a structure which divides the space in the ventricle into two separate parts.

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– Deoxygenated blood flows out from the heart to the lungs where gaseous exchange occurs in the walls of the blood capillaries in the lungs changing deoxygenated blood to oxygenated blood. – Oxygenated blood flows from the heart to the whole body except the lungs, changes to deoxygenated blood and flows back into the heart. Mammals and birds – Mammals and birds have a double circulatory system where blood flows through the heart twice in one complete cycle to the whole body. – The heart of mammals and birds have two atriums and two ventricles. – Deoxygenated blood flows out from the heart to the lungs where gaseous exchange occurs in the walls of the blood capillaries in the lungs changing deoxygenated blood to oxygenated blood. – Oxygenated blood flows from the heart to the whole body except the lungs, changes to deoxygenated blood and flows back into the heart.

Brain Teaser (p. 91) Systolic pressure is produced when the ventricle pumps blood out from the heart to the whole body. Blood coming out flows with high pressure. Diastolic pressure on the other hand is produced when blood flows into the heart. Blood flows with lower pressure.

Experiment 3.1 (p. 92) Questions 1. The more active the activity, the higher the pulse rate. 2. The rate of intake of oxygen and release of carbon dioxide by body cells increases while carrying out active activity. This causes the heart to beat more frequently and increases the pulse rate to transport oxygen and carbon dioxide more efficiently.

Formative Practice 3.2 (p. 95) 1. Blood circulatory system is a special transport system in complex organisms which functions to transport nutrients, respiratory gases and waste products.

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2.

Artery Transports oxygenated blood (except the pulmonary artery) Capillary Connects arteries to veins and is a place of exchange of substances between cells Vein Transports deoxygenated blood (except pulmonary vein)

3. Type of activity, gender, age, health 4. Caring for our heart is important to ensure continuity of our life.

Brain Teaser (p. 99) An individual who has blood type O can donate blood to all individuals irrespective of their blood type because blood type O does not have any antigens on its red blood cells.

Formative Practice 3.3 (p. 101) 1. Red blood cells, white blood cells, platelets and blood plasma 2. Blood plasma 3. Blood group of Blood group of recipient donor A B AB O A B AB O

 × × 

×  × 

   

× × × 

4. (a) To save lives (b) Leukaemia, haemophilia 5. (a) A person of blood group O can donate blood to any individual because the person has no A antigen and B antigen. (b) A person of blood group AB can receive blood from any individual because his plasma does not contain antibody Anti-A or Anti-B. (c) Blood bank is the place where blood is stored and retrieved. 6. (a) Hospitals, National Blood Centre (b) Road accidents, war 7. (a) Blood group AB (b) Presence of virus and other unwanted substances (c) Prevents clotting of blood

Activity 3.8 (p. 110) Questions 1. The eosin solution stains to form a specific pattern in the leaves, stem and roots of the plant. 2. Xylem 3. Passage of water in plants is through a transport tissue, namely xylem.

Activity 3.9 (p. 111) Questions 1. Part that is swollen

Summative Practice 3 (pp. 116 – 120) 1. (a) (b) (c) (d) (e) (f) 2. (a) (b) (c) (d) 3. (a) (b) (c)

Part that is shrivelled

2. Passage of food in plants is through the phloem.

Formative Practice 3.4 (p. 112) 1. Transpiration is a process of loss of water in the form of water vapour from the surface of plants to the air through evaporation. 2. (a) vapour, liquid (b) xylem, phloem 3. Light intensity, air humidity, temperature, air movement 4. Passage of water in xylem can be detected with the use of dye because water is colourless. 5. P: Phloem Q: Xylem R: Xylem S: Phloem T: Xylem U: Phloem

4. (a) (b) (c)

5. (a)

(b)

Formative Practice 3.5 (p. 113) 1. Similarity:

– Both are transport systems – Both transport water, nutrients and dissolved substances – Both exist in complex organisms Difference: Pick one of the differences shown in Figure 3.31. 2. Organisms cannot continue to live if they do not have a unique circulatory system according to their respective needs.

6. (a) (b)

PULSE TRANSPIRATION CAPILLARY PHLOEM HEART ANTIGEN

 × × ×

Valve Transport oxygenated blood (i) Blood vessel Q has thick walls to withstand high blood pressure. (ii) Blood vessel R has walls which are one cell thick to increase the efficiency of exchange of substances between blood and body cells through diffusion. Oxygen, carbon dioxide, water, digested food, waste products Oxygen, carbon dioxide, water During the day, plant cells carry out photosynthesis and produce oxygen. Hence, plant cells do not need oxygen supply. (i) dub (ii) lub (iii) systolic (iv) diastolic Systolic pressure reading is higher than diastolic pressure reading. Systolic pressure reading is reading of blood pressure which is higher when heart ventricle contracts to force blood out of the heart to be distributed to the whole body. Diastolic pressure reading is reading of blood pressure which is lower when heart ventricle slackens to facilitate blood flowing from the whole body back to the heart. (i) Eric, Roy (ii) Blood will coagulate.The victim may die. (i) Individual 2. This is because she fulfils the age condition of 18 years and above but less than 60 years. She also fulfils the body mass

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7.

8.

9.

10.

condition of more than 45 kg. (ii) Pregnant women are not suitable to donate blood. (a) Transports food (b) Xylem or Y (c) (i) The part above the ring will become swollen. Food collected here cannot be transported to the part below the ring because of the absence of X (phloem). (ii) The plant will dry up and die. 54 g = 0.3 g/min Set A = 180 mins 36 g Set B = = 0.2 g/min 180 mins (a) Badrul. He has the highest pulse rate immediately after activity. (b) Azizah. Her pulse rate returns to its original rate after a time interval of 15 minutes after activity. (a) Location B. Location A is not suitable for the growth of herbs. This is because of the absence of light needed by herbs to carry out photosynthesis. Location C is not suitable for the growth of herbs. High temperature in this location will increase the rate of transpiration of the herbs. Location B is suitable for the growth of herbs. Temperature in this dim location is able to maintain the rate of transpiration of the herbs. In addition, the presence of sunlight in the bright location enables the herbs to carry out photosynthesis. (b) Example of constructed model Transparent umbrella which can reduce the intensity of light that enters

Tissue

CHAPTER 4 Reactivity of Metals Brain Teaser (p. 126) Mineralogists usually use the name bauxite, civilians such as mine workers use the name aluminium ore and scientists use the name aluminium oxide.

Activity 4.1 (pp. 126, 127) Questions 1. Carbon dioxide 2. Flow the gas through limewater. If the limewater turns cloudy, the gas is carbon dioxide. On the other hand, if the limewater does not turn cloudy, the gas is not carbon dioxide. 3. (a) Carbon dioxide (b) Carbon dioxide 4. (a) calcium chloride + carbon dioxide + water (b) calcium oxide + carbon dioxide 5. Calcium, carbon, oxygen

Formative Practice 4.1 (p. 128) 1. Minerals are naturally occurring solid elements or compounds with definite crystalline structures and chemical compositions. 2. (a) Gold, silver, diamond or other mineral elements (Any one) (b) Bauxite, hematite, galena, cassiterite, quartz or other natural mineral compounds (Any one) 3. Calcium oxide that has properties of a base is used to neutralise acidic soil. Silicon dioxide that has a high melting point is used to make glass laboratory apparatus.

Activity 4.3 (pp. 130, 131) Questions 1. (a) Magnesium oxide (b) Aluminium oxide (c) Zinc oxide (d) Iron oxide (e) Lead oxide 2. The more reactive the metal towards oxygen, the more vigorous the reaction. 3. Magnesium → Aluminium → Zinc → Iron → Lead

Brain Teaser (p. 132) Water

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Device to regulate air humidity

Carbon + oxygen → carbon dioxide Hydrogen + oxygen → water

Activity 4.4 (pp. 132, 133) Questions 1. (a) Zinc + Carbon dioxide (b) No change (c) Lead + Carbon dioxide 2. Zinc and lead. Oxides of metals which are less reactive than carbon will turn into the metals when heated with carbon. 3. Aluminium Increasing Carbon reactivity Zinc Lead 4. Metal extraction. Metals which are less reactive than carbon in the reactivity series of metals can be extracted from their ores through the reduction of the oxide of these metals by carbon. 5. (a) more (b) less

Formative Practice 4.2 (p. 136) 1. The reactivity series of metals is an arrangement of metals according to their reactivity towards oxygen. 2. (a) Yes. Metal X is reactive towards oxygen because metal X burns with a bright flame. (b) Metal Y is less reactive than metal X. (c) X Y Z 3. (a) oxygen (b) potassium (c) extraction 4. (a) Potassium (b) Gold 5. (a) Carbon and hydrogen (b) Carbon and hydrogen can react with oxygen.

(b) Air pollution. Air pollution can be avoided by filtering the gases produced before releasing them to the atmosphere.

Summative Practice 4 (pp. 143 – 145) 1. (a) Elements: Iron, Silver, Potassium, Tin Compounds: Quartz, Bauxite, Galena, Hematite, Limestone (b) Bauxite, Aluminium and oxygen 2. (a) Tin(IV) oxide (b) Carbon (c) Tin + oxygen → Tin(IV) oxide 3. (b)  (c)  4. (a) Oxygen (b) Potassium and sodium are very reactive metals. Paraffin prevents potassium and sodium from reacting with oxygen and water vapour in the air. 5. (a) Oxygen (b) To provide oxygen for the reaction. (c) Heat the powdered metal until it glows before heating potassium manganate(VII) to provide oxygen for the reaction. (d) To construct a reactivity series of metals. 6. For metals which are more reactive than carbon, extraction of the metals is through the electrolysis method. For metals which are less reactive than carbon, extraction of the metals is through reaction of the metal ores with carbon. 7. Mixture of iron powder, limestone powder and coke

Formative Practice 4.3 (p. 141) 1. (a) (b) 2. (a) (b)

Electrolysis Reduction of iron ore with carbon Tin (i) Iron ore, limestone, coke (ii) Hot air (c) (i) Slag (ii) Molten iron 3. (a) Soil erosion. Problem of soil erosion can be solved by replanting trees.

Air at room temperature

Bottle/Plastic bag Drinking straw

Air at room temperature Hot air Cooking oil Hot Fan air blade Motor Motor Water Paper clip

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Explanation: Substance

Represent

Bottle

Blast furnace

Cooking oil

Slag

Water

Molten iron

Motor

Heating device

Iron powder

Iron ore

Limestone powder

Limestone

Innovative step: Fan blade is connected in a direction opposite to the normal direction so that sucked air flows through the motor to be heated. Motor is also cooled by this flow of air.

CHAPTER 5 Thermochemistry Experiment 5.1 (pp. 149 – 151) Questions (p. 151) 1. (a) Release of heat is shown by the rise in thermometer reading. (b) Absorption of heat is shown by the drop in thermometer reading. 2. (a) Thermal equilibrium (b) When the net rate of heat transfer between the products of reaction and thermometer is zero, products of reaction and thermometer is in thermal equilibrium. Hence, the temperature reading on the thermometer is fixed at maximum value or minimum value. 3. (a) The temperature during reaction is higher than the temperature before reaction occurred. (b) The temperature during reaction is lower than the temperature before reaction occurred. 4. – Sodium hydroxide dissolving in water – Reaction between sodium hydroxide and hydrochloric acid (Neutralisation) 5. – Ammonium chloride salt dissolving in water

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– Reaction between sodium hydrogen carbonate and hydrochloric acid 6. (a) Wrapping the polystyrene cup with cotton wool or felt cloth, using a lid for the cup. (b) Heat insulators such as cotton wool and felt cloth and lid for cup reduces the transfer of heat to the surroundings.

Formative Practice 5.1 (p. 154) 1. (a) An endothermic reaction is a chemical reaction that absorbs heat from the surroundings. (b) An exothermic reaction is a chemical reaction that releases heat into the surroundings. 2. Thermochemistry is the study of heat changes when chemical reactions occur. 3. The rate of respiration increases when performing vigorous physical activities, because respiration is an exothermic reaction. Heat produced by the exothermic reaction is absorbed into the body. Hence, the body temperature increases. 4. (a) Global warming (b) Reduce burning of fossil fuels. 5. (a) Exothermic reaction. (b) Exothermic reactions release heat into the surroundings and increase the temperature. High temperatures can relieve muscle cramp. Summative Practice 5 (pp. 155 – 158) 1. (a) Exothermic reaction (b) Endothermic reaction (c) Exothermic reaction (d) Endothermic reaction (e) Exothermic reaction (f) Exothermic reaction 2. (a) released (b) increases (c) hot (d) absorbed 3. (a) THERMOCHEMISTRY (b) PHOTOSYNTHESIS (c) RESPIRATION (d) THERMOMETER (e) ENDOTHERMIC (f) EXOTHERMIC

4. Heating of calcium carbonate is an endothermic reaction. Heat is absorbed by the chemical reaction that occurs during the decomposition of calcium carbonate. 5. The reaction between hydrochloric acid and sodium carbonate is an exothermic reaction whereas the reaction between hydrochloric acid and sodium hydrogen carbonate is an endothermic reaction. 6. Replanting of trees will increase the rate of photosynthesis. As photosynthesis is an endothermic reaction, more heat will be absorbed from the surroundings into the plants to carry out photosynthesis. Hence, the surrounding temperatures will drop. 7. (a) Thermite reaction is an exothermic reaction because heat is released into the surroundings. (b) In a thermite reaction, heating of iron(II) oxide, aluminium and magnesium tape produces iron and carbon dioxide through an exothermic reaction. The heat released in this reaction increases the temperature of the iron and carbon dioxide until the iron melts. This molten iron is used to repair and reconnect the broken iron railway rails. 8. Large plastic bag Toothpick Small plastic bag Water

Calcium chloride or ammonium nitrate powder

Instant hot pack: – Use toothpick to prick a hole in the small plastic bag so that water flows out from the plastic bag and mixes with the calcium chloride powder in the large plastic bag. – Dissolving of calcium chloride in water is an exothermic reaction which heats up the large plastic bag.

– Hence, the large plastic bag functions as an instant hot pack. Instant cold pack: – Use toothpick to prick a hole in the small plastic bag so that water flows out from the plastic bag and mixes with the ammonium nitrate powder in the large plastic bag. – Dissolving of ammonium nitrate in water is an endothermic reaction which cools down the large plastic bag. – Hence, the large plastic bag functions as an instant cold pack.

CHAPTER 6 Electricity and Magnetism Activity 6.1 (p. 165) Questions 1. Electric current 2. Cutting of magnetic field lines (by copper wire or coil of wire) 3. Induced current

Activity 6.2 (p. 166) Questions 1. (b)  (c)  2. Induced current is detected based on the lighting up of the LED. Induced current is produced and flows through the LED. Therefore the LED lights up. 3. Current is induced when magnetic field lines are cut. 4. Sound energy, heat energy, light energy 5. – LED lasts longer and does not burn out easily – LED will light up when electric current flows through as compared to filament bulb which only lights up when its filament is hot enough.

Activity 6.4 (pp. 172 – 175) Questions 1. To show the shape of graph, direction of current and voltage change for direct current and alternating current. 2. Similarity: Magnitude of the displacement of the light spot from the zero position

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3.

4.

5.

6.

in steps 6 and 8 is fixed and the same. This shows that the voltage of the battery is fixed and of the same value. Difference: Displacement of the light spot from the zero position in step 6 is positive while displacement of the light spot from the zero position in step 8 is negative. This shows that the current in step 6 flows from positive to negative whereas in step 8 the flow of current in the C.R.O. has been reversed. (a) First inference: The different position of the straight line on the display screen in steps 7 and 9 shows that direct current is the electric current which flows in the opposite direction. (b) Second inference: The position of the straight line from the zero position in steps 7 and 9 which are different shows that direct current in steps 7 and 9 flow in the opposite directions. Voltage produced by the power supply keeps changing. Hence, the light spot on the screen moves up and down to produce a vertical trace on the screen irrespective of the type of terminal connection to the C.R.O. (a) First inference: The shape of graph on the display screen produced by the vertical and horizontal trace made by a light spot shows continuous change in the direction of current flow and the voltage of the alternating current. (b) Second inference: The shape of graph on the display screen in steps 13 and 15 is the same. This shows continuous change in the direction of the current flow and the voltage of the alternating current irrespective of the type of terminal connection to the C.R.O.. (a) Direct current (b) Alternating current and direct current

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Formative Practice 6.1 (p. 176) 1. Renewable energy sources are energy sources that can be replaced continually and will not deplete while non-renewable energy sources are energy sources that cannot be replaced and will deplete. 2. (a) LED lights up in arrangements P and Q. In arrangements P and Q, magnetic field lines are cut by the coil of wire to produce induced current. This induced current flows through the LED causing the LED to light up. (b) LED does not light up in arrangement R. In arrangement R, there is no cutting of magnetic field lines and no induced current flows through the LED. 3. To show the shape of graph, direction of current and voltage change for direct current and alternating current.

Experiment 6.1 (pp. 178 – 180) Questions 1. (a) Bulb P is brighter compared to bulb S. (b) Vp > VS (c) Step-down transformer 2. (a) Bulb S is brighter compared to bulb P. (b) Vp < VS (c) Step-up transformer 3. If the difference between the number of turns in the primary coil and the number of turns in the secondary coil in a transformer is increased, the difference between the primary voltage and secondary voltage becomes bigger. 4. A transformer can only change the voltage of an alternating current if the number of turns of the primary coil and secondary coil is different. On the contrary, if the number of turns in the primary and secondary coil in a transformer is the same, then there is no change in the primary voltage and secondary voltage.

Formative Practice 6.2 (p. 183) 1. A transformer is a device that changes the voltage of an alternating current.

2. (a) (b) (c) (d) 3. (a)

alternating more step-up step-down Microwave oven, washing machine, refrigerator, television (b) Mobile phone charger, laptop/tablet charger Vp Np = 4. (a) Vs N s Np 240 = 10 5 Np = 10 ×

240 5

= 480 Number of turns in primary coil, Np = 480 (b) The transformer in the mobile phone charger is a step-down transformer because: i) the output voltage is lower than the input voltage. ii) the number of turns in the secondary coils, Ns, is less than the number of turns in the primary coils, Np (Ns < Np).

Brain Teaser (p. 187) In one cycle, single-phase wiring has two peaks whereas three-phase wiring has six peaks. Because of this, the current supply of three-phase wiring is more stable.

Brain Teaser (p. 192) Because most electric kettles sold in the market use 10 – 12 A current.

Formative Practice 6.3 (p. 194) 1. (a) (b) (c) 2. (a) (b) (c) 3. (a)

Step-up transformer station Switch zone Step-down transformer increased National Grid Network Switch zone Fuse, earth wire, circuit breaker, lightning conductor (any three) (b) Fuse functions as a safety component that melts and cuts off electric current supply when excessive current flows through it.

4. (a) Damaged wire insulator. Exposed live wire touches the exposed neutral wire. (b) (i) Excessive load (ii) Fire. Large flow of current causes wires, plugs and sockets to become so hot that they burn.

Brain Teaser (p. 199) Can be used in Thailand but the time taken to boil water is longer.

Brain Teaser (p. 201) No. A green building uses the concept of savings on energy, water and material consumption.

Formative Practice 6.4 (p. 202) 1. Energy efficiency is the percentage of energy input converted into useful energy output. 2. (a) Using the formula: E P= t 180 kJ P= 2 minutes 180 000 J = 120 s = 1 500 W (b) Power of air conditioner, P = 1 500 W 1 500 kW = 1 000 = 1.5 kW 3. P = VI 1 200 W = 240 V × I 1 200 W Electric current, I = 240 V =5A 4. (a) E = Pt =

800 30 kW × h 1 000 60

= 0.4 kWh (b) Cost of energy used by rice cooker = Electrical energy used in kWh × cost of energy for each kWh = 0.4 kWh × 30 sen/kWh = 12 sen

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5. (a) Star rating labelling on an electrical appliance shows the energy efficiency of the electrical appliance. (b) At least 3 stars. The more stars on a star rating label means more energy savings.

Summative Practice 6 (pp. 204 – 207) 1. (a) (b) (c) 2. (a) (b) (c) (d) 3. (a) (b) (c)

(d) 4. (a) (b) (c) 5. (a) (b) (c) (d)

True False True Non-renewable energy source Renewable energy source Renewable energy source Renewable energy source Magnetic field lines are cut Induced current LED lights up. Induced current flows through the LED. The flow of current through the LED causes the LED to light up. Generator Cathode ray oscilloscope Shape of graph, direction of current and voltage changes for direct current and alternating current. (i) Alternating current (ii) Direct current Step-down transformer Number of turns in the primary coil is more than the number of turns in the secondary coil. To reduce eddy current and increase the efficiency of the transformer Vp Np Using the formula, V = N s s 100 10 = 20 Vs Secondary voltage, Vs = 10 ×

20 100

=2V 6. (a) Main fuse (b) (i) Fuse and MCB function as safety devices that protect appliance from any excessive current flow. (ii) When the current flowing through a fuse exceeds the value of the fuse, the fuse will melt and cannot be reused without

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replacing the burnt fuse wire with a new fuse wire. An MCB is an electromagnetic switch connected to the live wire. An MCB cuts the circuit by turning off its switch when the current flowing through it exceeds its limit. The MCB can be reused by turning on the switch again without having to do any replacement. (c) Using the formula: P = VI 700 W = 240 V × I 700 W Electric current, I = 240 V = 2.9 A Fuse chosen is a 3 A fuse because the value of the fuse is slightly higher than the value of the electric current flowing through the hair dryer. 7. (a) Using the formula: Electric Power (W) = Voltage (V) × current (A) = 230 V × 10 A = 2 300 W 2 300 kW = 1 000 = 2.3 kW (b) 13 A fuse. 13 A fuse is the most suitable because a 13 A fuse allows a 10 A current to flow through it but does not allow a current exceeding 13 A to flow through the electric heater. A current that is too high will damage the electric heater. (c) A 10 A current that flows through 1A, 2A, 3A and 5A fuses will melt the fuse wires. Hence, the electric heater will not be able to function. 15 A and 30 A fuses allow current which is much greater than 10 A to flow through the electric heater. This will damage the electric heater. 10 A fuse is also not suitable because most 10 A fuses normally allow maximum current of less than 10 A to flow through it. Hence, the

10 A fuse will blow if installed in the electric heater. 8. (a) An MCB is a small electromagnetic switch connected to the live wire. (b) An MCB functions as an electric safety device. An MCB cuts off the circuit when the current flowing through it is too high or exceeds its limit value. (c) Ice cream Plasticine stick

MCB

Plastic rod

Nail

Model of MCB

The iron rotates in an anti-clockwise direction at the fulcrum.

The iron nail rotates in an anti-clockwise direction at the fulcrum on the ice cream stick.

The rotating iron pushes the spring upwards. Finally, the spring is released and it is below the iron.

The rotating iron nail pushes the toothpick upwards. Finally, the toothpick is released and it is below the iron nail.

Reset button when pushed downwards will push the iron downwards until the iron nail is below the spring again.

When the plastic rod is pushed downwards, it will push the iron nail downwards until the iron nail is below the toothpick again.

Fulcrum

Copper Shoe wire box

Rubber eraser

Plastic toothpick

Contact – plasticine Iron – nail Fulcrum – an ice cream stick Reset button – plastic rod Spring – plastic toothpick Iron core – Rubber eraser Electric wire – copper wire Scenario: When the electric current that flows through the MCB exceeds its limit value, the solenoid becomes a strong electromagnet. MCB

Model of MCB

Electric wire that is mounted to the contact and iron is pulled downwards as shown in Figure 4.

Copper wire that is mounted to the plasticine and iron nail is.pulled downwards as shown in the above diagram.

CHAPTER 7 Energy and Power Brain Teaser (p. 210)

(a) 1 000 (or 103) J (b) 1 000 000 (or 106) J

Brain Teaser (p. 212) No

Activity 7.1 (pp. 214, 215) Questions 1. (a) Frictional force (b) Gravitational force 2. Student’s answer 3. Force, displacement in the direction of the force, time 4. Student’s answer 5. (a) Aeroplane that is taking off, moving ERL train. (b) Sleep, sit

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Formative Practice 7.1 (p. 215) 1. (a) Work is defined as the product of force and displacement in the direction of the force. (b) Joule 2. Energy is the ability to do work. 3. (a) Power is defined as the rate of doing work. (b) Watt 4. (a) W = Fs = 2 500 N × 4 m = 10 000 J (b) Energy used = work done = 10 000 J W (c) Power of crane, P = t 10 000 J = 1.2 minutes 10 000 J = 72 s = 138.89 W

Formative Practice 7.2 (p. 221) 1. (a) Gravitational potential energy is the work done to lift an object to a height, h, from the surface of the Earth. (b) Elastic potential energy is the work done to compress or stretch an elastic material over a displacement, x from the position of equilibrium. 2. (a) W = Fs = 40 N × 0.5 m = 20 J (b) Gravitational potential energy (c) Gravitational potential energy of possessed by the chair = work done on it = 20 J 3. Distance of compression of spring = original length – length of of spring compressed spring = 50 cm – 30 cm = 20 cm = 0.2 m Elastic potential energy 1 = Fx 2 1 = (20 N) (0.2 m) 2 =2J

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4. (a) Kinetic energy =

1 mv2 2

where m is mass v is velocity Even though the value of the velocity, v of a heavy vehicle is small, the value of its mass, m is big. Hence, the large mass of these heavy vehicles causes more kinetic energy. (b) (i) Bullet fired from a pistol. (ii) Aeroplane taking off from runway at airport.

Formative Practice 7.3 (p. 226) 1. The Principle of Conservation of Energy states that energy cannot be created or destroyed but can only be converted from one form to another. 2. (a) P, R (b) Q 3. (a) Gravitational potential energy = mgh = 2 kg × 10 m s–2 × 2.5 m = 50 J (b) According to the Principle of Conservation of Energy, Kinetic = Gravitational energy potential energy 1 mv2 = 50 J 2 1 × 2 kg × v2 = 50 J 2 v2 = 50 m2s–2 v =

冑50 m2s–2

= 7.07 m s–1

Summative Practice 7 (pp. 228, 229) 1. (a) Energy possessed by an object is due to its position or condition. (b) Energy possessed by a moving object. 2. (a) N m (b) Work (c) stationary (d) can (e) acceleration 3. (a) W = Fs

(b) 4. (a)

(b)

(c)

5. (a) (b)

(c) 6. (a) (b) (c)

7.

= 5 kg × 10 m s–2 × 2 m = 100 J Energy used by motor = work done = 100 J Gravitational potential energy = mgh where m is the object mass g is the gravitational acceleration h is the height 1 Elastic potential energy = Fx, 2 where F is the compression or stretching force x is the displacement from equilibrium position 1 Kinetic energy = mv2, 2 where m is the mass, v is the velocity Work = force × displacement = 200 N × 0.4 m = 80 J Elastic potential energy 1 Fx = 2 1 = × 200 N × 0.4 m 2 = 40 J Because part of the work done is used to bend the bow. Principle of Conservation of Energy Vertical displacement of 2.5 cm from position Y. Potential energy at X = mgh 40 5 = kg × 10 m s–2 × m 1 000 100 = 0.02 J Potential energy at Y = 0 J, so difference in potential energy = (0.02 – 0) J = 0.02 J Retort stand

Explanation: This model of a roller coaster has vertical, winding and turning loops.

CHAPTER 8 Radioactivity Brain Teaser (p. 235)

(a) 1 Ci = 3.7 × 1010 Bq (b) 1 Bq = 2.70 × 10−11 Ci

Formative Practice 8.1 (p. 237) 1. (a) Wilhelm Roentgen (b) Henri Becquerel (c) Marie and Pierre Curie 2. Radioactivity is the spontaneous decay process of an unstable nucleus by emitting radioactive radiation. 3. (a) curie (Ci), becquerel (Bq) (b) The decay rate of an unstable nucleus. 4. Carbon-14 (C-14), Radon-222 (Rn-222), Thorium-232 (Th-232), Uranium-238 (U-238) 5. Half-life, T 1 , is the time taken for the 2

number of undecayed nuclei to be reduced to half of its original value.

Formative Practice 8.2 (p. 239) 1. According to Dalton’s Atomic Theory, an atom is the smallest particle and cannot be further divided. 2. (a) When an atom loses electrons. (b) When an atom gains electrons. 3. (a) Q and S. In Q and S, the number of protons is more than the number of electrons. (b) R and T. In R and T, the number of electrons is more than the number of protons. (c) P. In P, the number of protons is the same as the number of electrons. 4. (a) One electron is gained. (b) The number of electrons in the ion increases by one. (c) Bromide ion, Br –

Brain Teaser (p. 243)

1 μSv/h is equivalent to 10–6 J of ionising radiation energy absorbed by 1 kilogram of living tissue in a time interval of 1 hour. Rubber hose

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Formative Practice 8.3 (p. 246) 1. (a) Ionising radiation is radiation that produces positive and negative ions while passing through the air. Examples of ionising radiation: alpha radiation, beta radiation, gamma ray and X-ray (any one) (b) Non-ionising is radiation that does not produce ions while passing through the air. Examples of non-ionising radiation: light (visible), infrared, radio waves 2. (a) lower, higher (b) higher, lower 3. (a) Cosmic rays, background radiation (b) Nuclear accidents, nuclear tests, use of radioisotopes in medical field 4. (a) microSievert/hour (μSv/h) (b) 1 Sv is 1 Joule of ionising radiation energy absorbed by 1 kilogram of living tissue. (c) Radiation dose less than 0.2 μSv/h 5. The higher an individual is from the surface of Earth, the stronger the cosmic rays received. Hence, an individual who is in an aeroplane at a high altitude will absorb more cosmic rays causing his ionising radiation dose to exceed the safety level. 6. Ionising radiation dose received by the student = 0.01 mSv/h × 2 h × 5 = 0.1 mSv

Formative Practice 8.4 (p. 250) 1. (a) Carbon-14 dating to determine the age of an ancient object. (b) Cobalt-60 to treat cancer by killing cancer cells. (c) Phosphorus-32 to determine the absorption rate of phosphate fertilisers in plants. (d) Uranium-235 to build weapons such as atomic bombs. (e) β-radiation to monitor the thickness of metal sheets. 2. (a) Gamma rays (b) Gamma rays preserve food by killing the bacteria in the preserved food. 3. Boxes with thick lead walls can prevent all types of radioactive radiation emitted by radioactive sources or radioactive waste from escaping.

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4. (a) Presence of radioactive substance or radioactive radiation. (b) Hospitals, atomic research centres, X-ray rooms. (c) Alpha radiation. It has the lowest penetration power. 5. (a) Lead (or aluminium) (b) For lead: Advantage – Lead is an appropriate shield from all types of radioactive radiation including gamma rays which have high penetration power. Disadvantage – The high density of lead makes the clothing too heavy. For aluminium: Advantage – The lower density of aluminium makes the clothing less heavy. Disadvantage – Aluminium is a less efficient shield from gamma rays which have high penetration power. Summative Practice 8 (pp. 252 – 254) 1. (a)  (b) × (c)  2. Radioactive decay is a spontaneous process by which an unstable nucleus emits radioactive radiation until the nucleus becomes more stable. 3. sodium-24 (Na-24) 4. 0 hours 5.2 hours 10.4 hours 32 g 16 g 8g 15.6 hours 4g

20.8 hours 2g

Therefore the remaining mass of Pa-234 after 20.8 hours is 2 g. 5. (a) Ion formed is a positive ion because Mg atom loses two electrons to form Mg2+ ion. (b) Ion formed is a negative ion because F atom gains one electron to form F– ion. 6. (a) X-ray and gamma ray: • are ionising radiation • have high penetration power in air • are electromagnetic waves (b) (i) Sample Y. This is because the strawberry in sample Y is still in good condition.

(ii) Gamma rays (iii) Gamma rays kill bacteria in food. (iv) Yes. This is because the radioactive radiation dose in preserved food is within the normal level or safe level. 7. (a) • Wear appropriate protective clothing. • Detect radioactive radiation dose found on clothing with detectors such as Geiger Müller tube which gives a warning sound if the dose detected exceeds the normal level. (b) Light rays

Light rays

Mirror

Mirror

Formative Practice 9.2 (p. 265) 1. Phenomena that occur on the surface of the Sun and in outer space. 2. Formation of aurora, disturbances to telecommunication, navigation system and electric power lines 3. When the number of sunspots increases, coronal mass ejections will increase.

Summative Practice 9 (pp. 266 – 267)

LED

LED

Empty mineral water bottles wrapped in newspaper

Explanation: Component in the model

region in space surrounding Earth. It is a combination of the Earth's magnetic field (as the main magnetic field) and the magnetic field in the region in space. 4. Solar wind 5. Comet

Representing component in the system

LED

Beta radiation source

Light rays

Beta radiation

Mineral water bottles wrapped in newspaper

Bottles filled with drinking water

Mirror

Beta radiation detector

CHAPTER 9 Space Weather Formative Practice 9.1 (p. 263) 1. Photosphere, chromosphere, corona 2. Prominence, solar flare, coronal mass ejection 3. Earth’s magnetosphere is defined as a

1. A: Convection zone B: Chromosphere C: Photosphere D: Radiation zone E: Core F: Corona 2. 11 years 3. Sunspots 4. – Smartphone (mobile) – Internet – TV broadcast – Global positioning system (GPS) 5. All living things would die. Ionising radiation in solar winds would reach Earth and be absorbed by living things at levels exceeding the safety level. Hence, the risks to the health of living things would increase and this would be fatal. 6. Sketch of model: Student’s answer Explanation: – Green plastic bag represents ‘Bow Shock’ – White thread represents magnetic field lines from other planets – Red thread represents Earth’s magnetic field – Polystyrene cup represents a protective layer, the magnetosphere – Convex cover represents the part of the magnetosphere that is directed towards the Sun – Plasticine represents Earth

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CHAPTER 10 Space Exploration Formative Practice 10.1 (p. 272) 1. (a) Geocentric model (b) Heliocentric model (c) Modified heliocentric model according to Kepler’s Law 2. (a) Similarity: In the Solar System models built by Ptolemy and Copernicus, Earth or the Sun revolve in orbits. (b) Difference: In the Solar System model built by Ptolemy, Earth is at the centre of the orbit whereas in the Solar System model built by Copernicus, the Sun is at the centre of Earth’s orbit. 3. (a) Similarity: The Solar System models built by Copernicus and Kepler are heliocentric models. (b) Difference: In the Solar System model built by Copernicus, Earth and the planets revolve in circular orbits whereas in the Solar System model built by Kepler, Earth and the planets revolve in elliptical orbits.

Formative Practice 10.2 (p. 276) 1. Telescope 2. (a) Discovery is a space shuttle. (b) Hape is a rocket which sent Discovery to space. 3. (a) Remote sensing technology (b) To identify the locations hit by flood and determine the places to transfer flood victims 4. MACRES is responsible for all remote sensing projects in Malaysia. Summative Practice 10 (pp. 278 – 280) 1. (a) × (b)  (c) × (d) ×

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2. (a) Ptolemy (b) Kepler 3. Through human effort to obtain rational explanation about objects and phenomena in space based on their intellectual abilities. 4. Because space probes are not built to return to Earth. 5. (a) To gather information about Saturn to be sent back to Earth. (b) Solar wind (c) Solar energy 6. (a) – Oversee conditions and usage of land – Predict yield of crops (b) – Explore regions to search for oil and mineral sources – Map Earth’s surface (c) – Oversee natural disasters such as floods – Oversee forest fires, oil spills in the oceans and landslides (d) – Detect enemy invasions from air, land and sea – Detect nuclear tests 7. (a) A rocket is an aircraft that obtains its thrust using a rocket engine. (b) To send astronauts, spaceships, satellites, remote sensing instruments and space probes to space. (c) Functions as a weapon by carrying guided missiles. 8. Sketch of model: Student’s answer Explanation: Material

Function

Aluminium foil

Shield against ionising radiations from space

Cylindrical cardboard

As a rocket

Black plastic sheet

Solar battery/ Source of energy for spaceship

Cardboard in the form of a spaceship

As a spaceship