Cambridge Checkpoint Science Workbook 2 Answers

1 How plants grow

Answers to Cambridge Checkpoint Science Workbook 2 You may award one mark for each answer or part of an answer.

1 How plants grow A test for starch 1 a) 3, 5, 1, 2, 4 b) Green. c) The ethanol takes the green-coloured chlorophyll out of the leaf. d) (i) Black or blue-black. (ii) Brown. 2 In the form of grains. 3 Keep the plant in darkness for 2 or 3 days. Test the leaves to make sure they do not contain any starch.

Investigating the effect of carbon dioxide on starch production 4 a) (i) It is transparent to let light through for photosynthesis. (ii) It keeps the gases around the plant from mixing with air gases. b) Sodium hydrogencarbonate. c) Soda lime. d) Sodium hydrogencarbonate. It releases carbon dioxide gas into the air in the bag.

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1 How plants grow

Investigating oxygen production in plants 5 a)

100 90 80

Bubbles per minute

70 60 50 40 30 20 10

0

0

10

20 30 40 Distance from lamp/cm

50

60

b) The nearer the lamp, the more bubbles are produced. c) 90 d) He could have repeated the procedure a few times and found an average. e) He could collect a tube full of gas and test it with a glowing splint. If it relights, the gas is oxygen. f) Oxygen is produced in photosynthesis, so this shows that as light intensity increases, the rate of photosynthesis increases. g) (i) The distance between the lamp and the test tube. (ii) The number of bubbles produced.

Plants and light 6 Cover one leaf with aluminium foil and another leaf with transparent plastic then leave the plant in the light for over 4 hours. Take each leaf from the plant and test it for starch.

Biomass 7 a) Wet biomass is the mass of a living thing when it is alive. Dry biomass is the mass of a living thing after it has been killed and dried out. b) A 2000 kg, B 3000 kg, C 6000 kg, D 4500 kg.

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1 How plants grow

c)

6500 6000

Biomass of species/kg

5000

4000

3000

2000

1000

0 A

B Time periods

C

D

d) The numbers are going up and the animals might be breeding. e) The average biomass is going down because there are lots of small young ones. f) The smaller ones have been eaten by predators.

Minerals 8 Minerals are needed by plants for growth and development.

The transport of water through a plant 9 a) Root hairs. b) Xylem tissue. c) The root. d) (i) Evaporation. (ii) Water vapour. (iii) Through the stomata.

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2 A healthy diet

The cell structure of a leaf 10 a) A – epidermal cell; B – guard cell; C – chloroplast; D – nucleus. b) Carbon dioxide, oxygen, water vapour. c) (i) The hole closes. (ii) It prevents water escaping from the plant.

2 A healthy diet Nutrients 1 Carbohydrate. 2 Starch. 3 Protein. 4 C, B, D, A (Note the last two could also be A, D) 5 a) Iodine solution. b) Black or blue–black. c) Bread, banana, rice and spaghetti. 6 a) Food

White cloud formed in water

carrot peanut lentil butter cheese lamb orange

Water remained clear ✔

✔ ✔ ✔ ✔ ✔ ✔

b) Make sure all Bunsen burners and spirit burners are turned off.

How the body uses nutrients 7 Protein – building tissues and organs. Fat – making cell membranes. Carbohydrate – quickly released energy store. Fibre – helps food pass along the intestines. Vitamin A – helps us to see in the dark. Vitamin C – prevents scurvy. Calcium – strong bones and teeth. 8 a) B b) A c) E d) D e) B f) C 4

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3 Digestion

9 a)

75 Group 2 70

Weight/g

65 60 55 Group 1

50 45

0

5

10 Days

15

20

b) The average weight rises up to 51 g on day 9 then falls again after day 12. c) The average weight rises steadily to 71 g by day 15. d) It made them increase in weight. e) It showed that the four nutrients did not provide all that was needed for growth. f) Mammals produce milk for the healthy growth of their young. g) (i) They increased in weight. (ii) Their rate of growth slowed down. (in fact they eventually began to lose weight.)

The amounts of nutrients in food 10 a) Fat, iron, calcium, vitamin D. b) (i) Fat. (ii) Calcium and vitamin D. (iii) Milk products. d) He must eat vegetables and fruit, cereals or pulses because they all contain fibre, which forms soft faeces that are easier to release from the body.

A healthy diet 11 At the top should be chocolate, cheese, nuts and olive oil; at the bottom should be pasta, bread, potatoes and rice.

3 Digestion The breakdown of food  1 a) C P

I

I

I

I

C P P

P

M

M M

M

M

M

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3 Digestion

b) Incisors. c) Premolars and molars. d) Canines. e) It breaks it up into smaller pieces.  2 Large food molecules do not dissolve in water and cannot pass through the lining of the digestive system into the body. Small food molecules do dissolve and can pass through the wall of the digestive system into the body.  3 a) Proteins. b) Because they speed up reactions but are not changed or used up in them.

Along the alimentary canal 4 a) Water, mucin and amylase. b) (i) Amylase. (ii) Carbohydrate. (iii) Sugar molecules. c) Mucin. 5 a) Peristalsis. b) Circular muscles. 6 a) H, B, E, C, G, A, D, F b) Bile duct. c) Duodenum. d) Pancreas. e) Large intestine or colon. 7 a) The stomach. b) Hydrochloric acid, pepsin.

Enzymes 8 a)

Temperature/°C

Time for enzyme to work/min

10 20 30 40

11  9  5  3

b) As the temperature rose, the breakdown of starch increased. c) The starch broke down in 1 minute. d) It took much longer than she predicted.

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4 The circulatory system

e)

11 10 9

Time for starch destruction/minutes

8 7 6 5 4 3 2 1 0

0

10

20 30 Temperature of mixture/°C

40

50

f) The enzyme worked best at 40 °C. A high temperature slowed down the working of the enzyme.

4 The circulatory system 1 Amino acids, glucose, fatty acids, glycerol, oxygen and carbon dioxide.

The heart 2 a) A – right atrium, B – left atrium, C – right ventricle, D – left ventricle. b) 1 – vena cava, 2 – pulmonary artery, 3 – aorta, 4 – pulmonary vein. c) (i) A valve. X (ii)

Y Z

W

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4 The circulatory system

d) The right side. e) The vena cava. f) From the head and body. g) The pulmonary artery. h) The lungs.

blood vessels 3 a) A – artery, B – vein. b) A – artery. c) It has thick elastic walls. d) B – the vein. e) B – the vein. f) A – the artery. 4 a)

140 130

Pulse rate/bpm

120 110 100 90 80 70

0

30

60

90

120 150 Time/seconds

180

210

240

b) 70 bpm. c) 76 bpm. d) From 60 seconds until 120 seconds. e) 120 seconds. f) Adya, Su Lin, Carlos, Clare.  5 a) Capillaries. b) One cell thick. c) Spread throughout the organs.

What is in the blood?  6 Red blood cell – transports oxygen. White blood cell – fights disease. Platelets – help blood to clot. Plasma – transports digested food.

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5 The respiratory system

Moving oxygen to the cells and Moving carbon dioxide to the lungs and Moving glucose to the cells  7 Large.  8 a) Plasma. b) Cells, vein, vena cava, right atrium, right ventricle, pulmonary artery, lung.  9 Small intestine wall.

A healthy heart 10 a) Fatty foods. b) It can make a fatty layer in them. c) Calcium. d) It causes the pressure to rise. e) The heart must work harder. f) A blocked artery. g) (i) Coronary artery. (ii) A heart attack. h) A stroke. 11 a) It is much larger. b) It has to push the blood round a much bigger body. c) It causes a heart attack. d) By eating a balanced diet and cutting down on fatty foods. 12 (in any order) 1 – it makes many organ systems become more efficient, 2 – it prevents large amounts of fat building up in the body.

5 The respiratory system Breathing and respiration 1 The movement of air in and out of the lungs. 2 a) (i) Oxygen. (ii) Glucose. b) Carbon dioxide and water. c) Lungs – carbon dioxide, kidney – water. d) Energy; used for life processes.

The parts of the respiratory system 3 a) Ciliated epithelial cells. b) W – cilia, X – cytoplasm, Y – cell membrane, Z – nucleus. c) Dust and bacteria. d) They beat backwards and forwards to move the mucus up to the top of the windpipe.

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5 The respiratory system

4

Breathing movement

Inspiration

External intercostal muscles relax Ribs move up Diaphragm muscles contract Chest volume decreases Ribs move down Air moves out Air moves in Diaphragm muscles relax Chest volume increases External intercostal muscles contract

Expiration ✔

✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔

5 a) A b) 400 ml. c) Tidal volume. d) It decreases by 1200 ml. e) It increases by 2800 ml. f) B g) C

Gaseous exchange 6 At the end of the bronchioles. 7 a) and b)

path of oxygen

path of carbon dioxide

c) Diffusion. d) The oxygen combines with haemoglobin to make oxyhaemoglobin.  8 a) To test for carbon dioxide in inhaled and exhaled breath. b) Limewater. c) Make sure the limewater in both tubes is clear; gently breathe in and out of the central tube for 30 seconds; note the appearance of the limewater in both tubes. d) (i) tube A will remain clear and tube B will become cloudy. (ii) The air drawn into tube A does not have enough carbon dioxide in it to turn the limewater cloudy; the air from Paul’s breath has enough carbon dioxide in it to turn the limewater in tube B cloudy. 10

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6 Reproduction in humans

Respiration  9 glucose + oxygen ➔ carbon dioxide + water. 10 a) When the body cannot get enough oxygen for aerobic respiration to take place. b) Sprinting. c) It breathes in large quantities of air quickly to supply the oxygen that is needed to break down the substances made during anaerobic respiration.

Smoking and health 11 a) Nicotine. b) (i) They stop the cilia beating. (ii) It increases. c) Chronic bronchitis, emphysema.

6 Reproduction in humans How the changes begin  1 Puberty is the period of time when a child’s body develops into an adult’s body.

The male and female reproductive organs  2 Male reproductive organs

Female reproductive organs

testes scrotum penis sperm duct

vagina ovary uterus oviduct

The menstrual cycle  3 a) Female. b) Once a month. c) (in any order) 1 – pregnancy, 2 – at the end of the menopause.

Fertilisation  4 Oviduct.  5 B, E, A, F, C, D

The development of the baby  6 Uterus.  7 The zygote.  8 a) (in any order) Food, oxygen, antibodies. b) Carbon dioxide (but accept waste products). c) Umbilical cord. d) Stop the ovaries producing more eggs; stop the wall of the uterus breaking down. Cambridge Checkpoint Science Workbook 2 © Hodder & Stoughton Ltd 2012

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6 Reproduction in humans

 9 Embryo. 10 Foetus. 11 a) Mammal

Gestation periods (weeks approx.)

mouse cat goat cow horse

b)

 3  9 22 40 48 50

40

Time/weeks

30

20

10

0

Mouse

Cat

Goat

Cow

Horse

Mammals

c) The larger the animal, the longer the gestation period. d) (i) Yes. (ii) Adult humans are larger than most goats but smaller than most cows. e) It does not fit in because the guinea pig is smaller than the cat yet has a longer gestation period. f) In the longer gestation period of the guinea pig, the pups have developed much more than the kittens.

Birth 12 D, A, E, F, B, C

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7 Diet, drugs and disease

7 Diet, drugs and disease Diet 1 a)

20 Developed country

Mass/kg

15

Developing country 10

5

0

1

2

3

4

5

6

Age/years

b) The children from developed country have 1 kg more mass than those from developing countries. c) They both increase in mass. d) The children from the developed country put on greater mass from age 4 to 5 than the children from the developing country. e) 16 kg. 2 Marasmus

Kwashiorkor

B C E

A D F

3 a) Fats and carbohydrate. b) Any three from sweets, chocolates, pizzas and crisps or other high-fat, high-carbohydrate food as appropriate. c) They move around less. d) It increases. e) The heart, bones, joints. f) It can rise. g) Type 2 diabetes. h) Blindness, nerve and blood vessel damage in the feet (leading to amputation), kidney damage that could be fatal. i) Eating a balanced diet; taking part in an exercise programme. 4 a) It prepares their bodies to start digesting food again. b) To help the body build up again. c) A month. Cambridge Checkpoint Science Workbook 2 © Hodder & Stoughton Ltd 2012

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7 Diet, drugs and disease

Drugs  5 If more than one line is drawn from any drug, award no mark for that drug. Non-medical drug – reduces ability to fight disease. Alcohol – causes nerve damage. Tobacco – slows down growth.  6 a) Because they are cheaper. b) Body mass is reduced, Appearance – they become thinner. c) Causes memory loss. d) Liver, kidneys, bone marrow. e) Vomit blocking the windpipe.  7 a) B, E, D, C, A b) Any of the following: A – danger of suffocating on vomit; B – leads to having more alcohol to keep state of relaxation but leads to other changes; C – falling over can cause injuries; D – behaviour can lead to fights or dangerous activities, for example balancing on a bridge; E – slow responses may lead to accidents.  8 a) Effect

Drug

Increase activity then sadness; heart and brain damage Hallucinations, mental illness Speeds up reactions and causes confusion Carelessness, sickness, sleeplessness Slows down body to point of death

amphetamines cannabis ecstasy cocaine heroin

b) (i) Heroin. (ii) Users sharing needles. c) Seeing and hearing something that is not there. d) LSD.  9 (i) An addict. (ii) Withdrawal symptoms.

Disease 10 STD – sexually transmitted disease, STI – sexually transmitted infection, AIDS – acquired immune deficiency syndrome, TB – tuberculosis, HIV – human immunodeficiency virus, PID – pelvic inflammatory disease. 11 Chlamydia, gonorrhea and syphilis. 12 Malaria. 13 a) German measles. b) Coughs and sneezes. c) It can cause blindness and deafness. d) The heart. 14 Egypt, India, China, Greece, Rome, Islam.

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8 The particle theory

8 The particle theory The properties of matter and the particle theory 1 They all have a definite mass. 2 a) 3 b) Lattice. c) Strong forces of attraction. d) The particles stay in one position but can move to and fro about that position. 3 The forces that hold liquid particles are weaker than in solids and allow the particles to move over each other. 4 The forces between particles in a gas are much weaker and allow the particles to move apart, which means that they can be squashed together. Particles in liquids are already very close so must be squashed much harder to get them closer.

When states of matter change 5 a) He puts the petri dish over the graph paper and the ice cube in the middle of the petri dish. b) A clock. c) He checked that no water had spread out from the cube then set the clock running. He observed the position of the melted water regularly by measuring its edge against the squares of the graph paper and recorded how many squares the water had covered. d) He could set up three sets of apparatus – one in a fridge, one in a shady room, one outside in the Sun. 6 a) Made all the drops the same size. b) It decreases. c) See e). d) The line is not a straight line – it bends to the left and then bends to the right as you come down it. e) 60 50

Time/minutes

40 30 20 10 0

5

0

10

15 20 Temperature/°C

25

30

35

f) The higher the temperature the faster the evaporation.

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9 Elements and atoms

7 a) The particles move faster and the fastest leave the surface as a gas or form a gas bubble, which rises to the surface and bursts, releasing the gas particles into the air. b) The water boils faster. c) Steam. d) (i) Water droplets. (ii) Because the steam is cooled down by the cold water in the jacket and condenses to form water. (iii) They slow down, come together and slide over each other.

Gas pressure 8 a) (i) It is smaller. (ii) The temperature is lower so the particles travel more slowly and push with less force on the wall of the balloon. b) (i) It is larger. (ii) The temperature is higher so the particles travel more quickly and push with greater force on the wall of the balloon.

Diffusion 9 a) Use the same amount of water and ink in all parts of the test. b) Use a thermometer. c) (i) B (ii) The particles at a higher temperature have more energy and spread out faster than the particles at a lower temperature. d) The liquid is completely shaded in.

9 Elements and atoms The discovery of the elements 1 Iron, silver, gold, tin, copper, sulfur, lead. 2 a) Some chemical reactions that make new substances also produce an electric current. b) A battery to produce a current of electricity. c) Humphrey Davy reasoned that as an electric current is produced when some new substances are made then perhaps an electric current could be used to break down a substance into its elements. d) Hydrogen and oxygen. e) He predicted that potash contained an unknown element. f) 1 – He continued his investigation by heating some solid potash on a platinum spoon. 2 – Next he added a small amount of water to the potash.

The link between elements and atoms 3 An element is made from one type of atom. 4 An element cannot be split up into simpler substances by chemical reactions.

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9 Elements and atoms

The properties of elements 5 Element

Colour

mercury bromine

silver red–brown

 6 Any five from: oxygen, nitrogen, hydrogen, helium, chlorine, fluorine, argon, krypton, neon, xenon, radon.  7 Calcium – orange. Copper – green. Magnesium – white. Sodium – golden yellow.

Chemical symbols  8 Collect gold, copper, mercury, tartar, vinegar, soap. Mix in a crucible for an hour. Heat in a bath for a day. Leave for a month. Then put in a bottle.  9 a) Jons Jakob Berzelius in 1813. b) Each element is identified by the first letter of its name. If two or more elements begin with the same letter another letter in the name is also used.

The first twenty elements of the periodic table 10 a) and b) Name

Symbol

Name

Symbol

  1 hydrogen   2 helium   3 lithium   4 beryllium   5 boron   6 carbon   7 nitrogen   8 oxygen   9 fluorine 10 neon

H He Li Be B C N O F Ne

11 sodium 12 magnesium 13 aluminium 14 silicon 15 phosphorus 16 sulfur 17 chlorine 18 argon 19 potassium 20 calcium

Na Mg Al Si P S Cl Ar K Ca

c) Sodium – natrium, potassium – kalium. d) H

VIII

He I

II

III

IV

V

VI

VII

Li

Be

B

C

N

O

F

Ne

Na

Mg

Al

Si

P

S

Cl

Ar

K

Ca

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10 Elements, compounds and mixtures

10 Elements, compounds and mixtures Mixing elements and From elements to a compound 1 a) Property

Iron

Sulfur

Colour Test with a magnet Mixing with water

grey magnetic sinks

yellow not magnetic tends to float

b) The iron springs to the magnet but the sulfur does not. c) The iron sinks and the sulfur tends to float. d) Bunsen burner provides heat; crucible holds the mixture; pipe clay triangle holds the crucible; tripod supports the pipe clay triangle. e) Black, non-magnetic solid that sinks in water. f) Iron sulfide.

Chemical reactions and equations 2 Reactant A + reactant B ➔ product C + product D. 3 a) Oxygen + glucose ➔ carbon dioxide + water. b) Oxygen and glucose. c) Carbon dioxide and water.

Chemical names of compounds 4 a) Copper carbonate – blue-green solid. Sodium hydroxide – colourless solid. Sodium chloride – white crystalline solid. Carbon dioxide – colourless gas. Copper sulfate – bright blue crystals. b) (i) Sodium chloride. (ii) Copper carbonate. (iii) Sodium hydroxide. c) (i) Calcium sulfate. (ii) Calcium, sulfur and oxygen. d) (i) Calcium carbonate. (ii) Calcium, carbon and oxygen. (iii) Snail shells and birds’ eggs.

Mixtures 5 Tiny particles of insoluble solid mixed with a liquid – suspension. Liquid droplets in a gas – aerosol. Tiny water droplets mixed with air – mist. Gas bubbles trapped in a liquid – foam.

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11 Metals and non-metals

 6 a) White spirit. b) Water. c) Propanone. d) Ethanol.  7 a) Solute. b) Solvent. c) Solution.

Separating mixtures  8 a) Decant it. b) The liquid is carefully poured out of the beaker without disturbing the sediment.  9 a) Filtration. b) A – filter funnel, B – filter paper, C – support, D – beaker. c) The filter paper has holes in it, which let the water through but are too small to let the solid particles through. d) Buchner funnel, conical flask with side arm and rubber tube, suction pump. 10 a) A suspension. b) Make sure they all have the same amount of liquid in them. c) (i) They are spun round very fast. (ii) They are forced to the bottom of the test tubes. d) Decanting. 11 a) Chromatography. b) The top one. c) (in any order) 1 – It is more soluble than the other pigment. 2 – It sticks to the paper less than the other pigment. 12 a) Simple distillation. b) Boiling. c) Condensation. d) By putting a cold water jacket around it as in the Liebig condenser. e) Antibumping granules and salt crystals. 13 a) They do not dissolve in each other. b) It forms two layers with the oil being the top layer. c) She pours in the liquids, lets them settle, opens the tap and draws off the vinegar into a beaker and then closes the tap. She then opens the tap again and lets the oil flow into a second beaker.

11 Metals and non-metals  1 It feels hard and cold.

Metals and non-metals in the periodic table  2 a) Helium, silicon, phosphorus, boron, chlorine. b) The right.

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12 Chemistry in everyday life

The uses and properties of metals and The uses and properties of non-metals 3 Aircraft – aluminium, aircraft tyres – nitrogen, street lamps – sodium, toothpaste – calcium, liquid mirror telescope – mercury, party balloon – helium, pencil lead – graphite, fungicide – sulfur, making cells to generate electricity – zinc, disinfectant – bromine, wires in electrical circuits – copper, dyes and inks – potassium. 4 Magnesium – strips burn very brightly. Potassium – explodes in water. Iron – rusts. Sulfur – burns with a blue flame. Bromine – makes red-brown toxic fumes. 5 a) Conductivity of electricity. b) Iron sulfide did not conduct electricity. c) (i) The lamp lit up. (ii) Iron is a metal so it is a conductor of electricity. d) (i) The lamp did not light. (ii) Sulfur is a non-metal and so does not conduct electricity.

Chemical properties of metals and non-metals 6 Make it take part in a chemical reaction. 7 a) A bright yellow glow. b) Sodium chloride. c) Sodium + chlorine ➔ sodium chloride. 8 a) Sodium oxide powder is produced. b) Sodium + oxygen ➔ sodium oxide. c) An alkaline solution, also accept sodium hydroxide. d) Blue. 9 a) A compound, a gas. b) Sulfur dioxide. c) Sulfur + oxygen ➔ sulfur dioxide. d) (i) Three. (ii) One sulfur atom and two oxygen atoms. e) (i) Red. (ii) The solution is an acid.

12 Chemistry in everyday life Respiration; Combustion; Burning; Explosions caused by dust 1 a) Respiration. b) Energy. c) Respiration and photosynthesis. d) The Sun’s energy is trapped in food by photosynthesis. We use the energy in food to live. 20

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12 Chemistry in everyday life

2 a) Combustion. b) Fuel + oxygen ➔ carbon dioxide + water. c) Energy. 3 It produces a flame. 4 G, B, F, D, A, C, E

Reactions with oxygen 5 A chemical reaction where oxygen is added to a substance. 6 Oils and fats. 7 a) Nitrogen N. b) (i) No. (ii) The mouse needs oxygen for respiration and without it the mouse would die. c) The fats and oils in them have oxidised and made the food rancid. 8 She could take the temperature of the room with a thermometer, open the hand warmer and wrap it round the bulb of the thermometer and observe the rise in temperature. 9 a)

b)

Day

Number of spots

1 2 3 4 5 6 7

0 1 3 6 10 6 3

10 9 8

Number of spots

7 6 5 4 3 2 1 0

1

2

3

4 Days

5

6

7

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13 Speed

c) As the number of spots increases and then decreases, rusting develops early in the experiment and then slows down. d) (i) It is not a good method. (ii) Some of the larger spots join together, which reduces the spot count while the amount of rusting increases. e) Measure the area of the spots either using a ruler to measure distance across or use tissue paper/ transparent plastic with squares on it and measure the number of squares converted to rust each day. 10 a) It makes their mass increase. b) Flakes of rust fall off. c) Zinc is more reactive with oxygen than iron and forms an oxide layer over the bucket, which keeps oxygen away from the iron and so it does not flake off. 11 Silver – tarnish. Bronze – patina. Copper – verdigris.

13 Speed  1 A measure of the distance covered by a moving object in a certain time.  2 To move faster.  3 Accelerate, run steadily, accelerate.

Speed records  4 Distance per minute is 100 × 6 = 600 m, distance per hour is 600 × 60 = 36 000 m = 36 km/hr.  5 a) 80 000 metres divided by 60 = 1333 metres. b) 15 seconds is ¼ of a minute. 1333 divided by 4 = 333 metres. c) (i) 1067 divided by 4 = 266.75 metres. (ii) No. (iii) It is 300 – 266.75 = 33.25 metres away. d) The lion will catch the zebra.

Measuring speed  6 B, E, A, C, F, D  7 a) Radio waves. b) The radio waves are reflected off the vehicle back to the radar gun. c) It compares the time difference between sending the beam and receiving it back.  8 a) They have all got different reaction times. They have all got different views of the start and finish line. b) By using light gates.  9 a) Friction. b) Air resistance. c) (i) 60 × 60 = 3600 metres/hr = 3.6 km/hr. (ii) 90 × 60 = 5400 metres/hr = 5.4 km/hr. (iii) 120 × 60 = 7200 metres/hr = 7.2 km/hr. 22

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14 Sound

d) A 3.5 m, B 5 m, C 1 m. e) Alan – C. Dabir – A. Harum – B. f) They could use one person to go down each zip wire; the person keeps the same shape on each one; all trolleys are oiled to the same degree; if light gates are not used, the same person operates the stopwatch.

Distance/time graphs 10 a)

10 9 8 7

Distance/cm

6 5 4 3 2 1 0

0

10

20

30

40

50 60 Time/seconds

70

80

90

100

b) In the 30 to 40 second period. c) In the 60 to 90 second period. d) 6 cm. e) It jumped or flew.

14 Sound  1 The sound goes lower as the vibrating length increases. The sound goes higher as the vibrating length decreases.

From vibration to sound wave  2 It is a to-and-fro or backwards-and-forwards movement about a fixed point.  3 Any ten, but must have a variety from: people, animals, vehicles, machines, musical instruments, weather conditions.

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14 Sound

 4 Particles.  5 a) Particles. b) The air pressure rises. c) The particles move apart and the air pressure falls. d) Regions of low and high pressure. e) A sound wave.  6 a) Solid. b) Liquid. c) Gas.  7 B, F, C, E, A, D

Describing a wave  8 a) A – wavelength, B – amplitude. b) 1 – the distance from one crest top to the next, 2 – the distance from the bottom of one trough to the next.

Detecting sound waves  9 C, E, G, A, H, D, F, B

Oscilloscopes 10 a) It allows you to see waves produced by sounds. b) Cathode ray oscilloscope. c) (i) A spot. (ii) A picture of the sound wave. d) It can store the displays made on the screen and build up a data bank of sound waves for further study.

The loudness of a sound 11 The loudness increases. 12 Whisper – b) – 20. Road drill – a) – 110. Normal speech – c) – 55.

The pitch of a sound 13 The frequency decreases. 14 a) The pitch is raised. b) It will be lower than the others. c) It will go higher. d) A – quiet, high pitched, B – quieter, lower pitched, C – loud, high pitched, D – very quiet, very low pitch.

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15 Light

15 Light  1 a) Examples could include Sun, stars, fire, lamp, TV screen, computer screen, phone screen. b) Anything from things like clothes, furniture and furnishings to desk items and food and drink.

Light rays 2 Some of the light is reflected from dust in the atmosphere. 3 Long, straight lines of light with straight edges.

Classifying non-luminous objects 4 Transparent – can see clearly through – light is not scattered as it passes through. Translucent – cannot see clearly through – light is scattered as it passes through. Opaque – cannot see through it – light does not pass through.

Shadows 5 a) When light shines on an opaque object. b) On the side away from the light source. c) Dark region without light. d) The position of the light source and where the shadow falls. 6 a) A sharp-edged shadow equally dark in all areas. b) The shadow centre is dark but the edges are lighter. c) It gets larger.

Reflecting light 7

normal incident ray

angle of incidence

reflected ray

angle of reflection mirror

8 a) (i) A cinema screen. (ii) A mirror or smooth shiny surface. b) Same way up, same size, same distance from mirror. c) Wrong way round. 9 The light rays are scattered in all directions.

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15 Light

Passing light through transparent materials 10 a)

normal

incident ray

angle of incidence

angle of refraction

refracted ray

b) A change in the speed of light. 11

water level refracted ray

coin

Colour 12 a) C, D, A, F, E, B b) With your back to the Sun. 13 Red, orange, yellow, green, indigo, violet. 14 a) (i) The chloroplasts appear black. (ii) The green colour is filtered out so no light comes from the chloroplasts. 15 Stage requirements

Filters needed

White light Blue light Yellow light Cyan light

Red, blue and green filters Blue filter Green and red filters Blue and green filters

16 a) By mixing yellow and magenta. b) By mixing cyan and yellow. c) By mixing magenta, yellow and cyan. d) All the light is absorbed.

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16 Magnetism

16 Magnetism 1 Cobalt, iron, nickel, steel. 2 a) Lodestone. b) Magnetite.

The behaviour of magnets 3 a)

7 6 North pole Number of paper clips

5 4 3 2 1

South pole

0

1

2

3 4 Number of cards

5

b) The power of the magnet decreases with distance from its poles. c) The north pole is stronger than the south pole. d) (i) The south pole with cards 4 and 5. (ii) They both have the same result, which goes against the pattern set up in the rest of both graphs.

Inside a magnet 4 Domains.

The magnetic field 5 a) and c) line of force

S

N

b) Magnetic field pattern. Cambridge Checkpoint Science Workbook 2 © Hodder & Stoughton Ltd 2012

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16 Magnetism

The Earth’s magnetic field 6 The two parts of the iron and nickel core moving at different speeds.

The link between magnetism and electricity 7 A magnetic field is generated around it. 8 The magnetic force increases. 9 a) It is a coil of wire wrapped round a piece of iron. b) The magnetic field of the current induces magnetism in the piece of iron and turns it into a magnet. c) The wire loses its magnetic field and the iron loses its magnetism.

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