Cambridge IGCSE Combined and Co-ordinated Sciences 1 Answers to questions Biology Chapter B1 Cells B1.01 about 1500 times B1.02 10 mm (1 cm) B1.03 all cells B1.04 cellulose B1.05 It will allow all substances to pass through. B1.06 It will allow some substances to pass through, but not others. B1.07 water B1.08 It is a space inside a cell, surrounded by a membrane, containing a liquid. B1.09 It is a liquid containing sugars and other substances dissolved in water, found inside a vacuole in a plant cell. B1.10 It absorbs energy from sunlight. B1.11 DNA, in the form of chromosomes; this is the genetic information of the cell. B1.12 They are usually too long and thin, but become shorter and fatter just before the cell divides. Chapter B2 Movement in and out of cells B2.01 It is the net movement of molecules from a region of their higher concentration down a concentration gradient to a region of their lower concentration, as a result of their random movement. B2.02 For example: oxygen diffusing into an organism across a gas exchange surface, or into a cell across its cell surface membrane; carbon dioxide diffusing out of an organism across a gas exchange surface, or out of a cell across its cell surface membrane; diffusion of carbon dioxide into the air spaces of a leaf. B2.03 a It increases kinetic energy. b It will increase the rate of diffusion, because the molecules move faster. B2.04 a sugar molecule B2.05 a membrane that allows some particles to pass through, but not others B2.06 Visking tubing, a cell membrane B2.07 It is a dilute solution (or it has a high water potential). B2.08 It absorbs water by osmosis, swelling until it bursts. B2.09 The plant cell absorbs water by osmosis just like an animal cell, but the strong cellulose cell wall prevents it bursting. B2.10 a the cell wall b the cell membrane B2.11 a cell that has taken up water so that the cell contents are pressing outwards onto the cell wall B2.12 the condition of a plant cell when it has lost so much water that the cytoplasm and vacuole have shrunk, pulling the cell membrane away from the cell wall B2.13 by putting a plant cell into a solution that is more concentrated than the cytoplasm and cell sap B2.14 The same solution as is outside the cell – the cell wall is fully permeable, so both water and solute molecules can diffuse freely through it. B2.15 In Figure B2.04, the solution outside the cell has a higher water potential than the cytoplasm or cell sap. Water therefore diffuses down the water potential gradient, into the cell, through the partially permeable cell membrane. In Figure B2.05, the solution outside the cell has a lower water potential than the cytoplasm or cell sap. Water therefore diffuses down the water potential gradient, out of the cell, through the partially permeable cell membrane. Chapter B3 Biological molecules B3.01 the chemical reactions that take place inside the body B3.02 Cells will lose water. Reactions take place in solution in the cytoplasm. If there is not enough water, this cannot happen. Water is also required for transport (e.g. substances dissolve in the water in blood plasma), and cooling (sweating and transpiration). B3.03 carbon, hydrogen, oxygen B3.04 There are 6 carbon atoms, 12 hydrogen atoms and 6 oxygen atoms in one glucose molecule.
Transcript
Cambridge IGCSE Combined and Co-ordinated Sciences
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Answers to questionsBiologyChapter B1 CellsB1.01 about 1500 times
B1.02 10 mm (1 cm)
B1.03 all cells
B1.04 cellulose
B1.05 It will allow all substances to pass through.
B1.06 It will allow some substances to pass through, but not others.
B1.07 water
B1.08 It is a space inside a cell, surrounded by a membrane, containing a liquid.
B1.09 It is a liquid containing sugars and other substances dissolved in water, found inside a vacuole in a plant cell.
B1.10 It absorbs energy from sunlight.
B1.11 DNA, in the form of chromosomes; this is the genetic information of the cell.
B1.12 They are usually too long and thin, but become shorter and fatter just before the cell divides.
Chapter B2 Movement in and out of cellsB2.01 It is the net movement of molecules from a
region of their higher concentration down a concentration gradient to a region of their lower concentration, as a result of their random movement.
B2.02 For example: oxygen diffusing into an organism across a gas exchange surface, or into a cell across its cell surface membrane; carbon dioxide diffusing out of an organism across a gas exchange surface, or out of a cell across its cell surface membrane; diffusion of carbon dioxide into the air spaces of a leaf.
B2.03 a It increases kinetic energy.
b It will increase the rate of diffusion, because the molecules move faster.
B2.04 a sugar molecule
B2.05 a membrane that allows some particles to pass through, but not others
B2.06 Visking tubing, a cell membrane
B2.07 It is a dilute solution (or it has a high water potential).
B2.08 It absorbs water by osmosis, swelling until it bursts.
B2.09 The plant cell absorbs water by osmosis just like an animal cell, but the strong cellulose cell wall prevents it bursting.
B2.10 a the cell wall b the cell membrane
B2.11 a cell that has taken up water so that the cell contents are pressing outwards onto the cell wall
B2.12 the condition of a plant cell when it has lost so much water that the cytoplasm and vacuole have shrunk, pulling the cell membrane away from the cell wall
B2.13 by putting a plant cell into a solution that is more concentrated than the cytoplasm and cell sap
B2.14 The same solution as is outside the cell – the cell wall is fully permeable, so both water and solute molecules can diffuse freely through it.
B2.15 In Figure B2.04, the solution outside the cell has a higher water potential than the cytoplasm or cell sap. Water therefore diffuses down the water potential gradient, into the cell, through the partially permeable cell membrane.
In Figure B2.05, the solution outside the cell has a lower water potential than the cytoplasm or cell sap. Water therefore diffuses down the water potential gradient, out of the cell, through the partially permeable cell membrane.
Chapter B3 Biological moleculesB3.01 the chemical reactions that take place inside
the body
B3.02 Cells will lose water. Reactions take place in solution in the cytoplasm. If there is not enough water, this cannot happen. Water is also required for transport (e.g. substances dissolve in the water in blood plasma), and cooling (sweating and transpiration).
B3.03 carbon, hydrogen, oxygen
B3.04 There are 6 carbon atoms, 12 hydrogen atoms and 6 oxygen atoms in one glucose molecule.
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B3.05 a simple sugar (monosaccharide) b polysaccharide c polysaccharide
B3.06 a glucose b glucose c glycogen d sucrose e starch
B3.07 carbon, hydrogen, oxygen
B3.08 heat insulation, energy store
B3.09 The oils are an energy store for the embryo plant to use when germination begins, before it can photosynthesise.
B3.10 nitrogen, sometimes sulfur
B3.11 about 20
B3.12 They are made of long chains of smaller molecules linked together.
B3.13 haemoglobin, any enzyme, antibodies, other suitable example
B3.14 for example: transporting oxygen (haemoglobin); the formation of new cells (for growth or repair); forming hair (keratin); catalysing reactions (enzymes)
B3.15 a substance that speeds up a chemical reaction without itself being changed
B3.16 enzymes
B3.17 all of them
B3.18 For amylase, the substrate is starch and the product is maltose.
B3.19 the temperature at which an enzyme works at its fastest
B3.20 40 °C
B3.21 The enzyme molecule loses its shape at high temperature, so the substrate will no longer fit into the active site.
Chapter B4 Plant nutritionB4.01 any suitable organic substance – for example,
sugar
B4.02 carbon dioxide and water
B4.03 the green pigment, found in chloroplasts, that absorbs energy from sunlight, used to drive photosynthesis
B4.04 epidermal cells
B4.05 to prevent water loss from leaf cells
B4.06 small holes, mostly on the lower surface of a leaf, through which gases can diffuse
B4.07 sausage-shaped cells surrounding a stoma, which can change their shape and open or close the stoma
B4.08 Palisade mesophyll cells, spongy mesophyll cells and guard cells contain chloroplasts. Epidermal cells (and xylem vessels and phloem sieve tubes) do not.
B4.09 carbon dioxide and water
B4.10 about 0.04%
B4.11 by diffusion, through the stomata
B4.12 Water is brought to the leaf in xylem vessels.
B4.13 More sunlight can be absorbed; more carbon dioxide can diffuse into the leaf at the same time.
B4.14 Sunlight can reach all the cells in the leaf. Carbon dioxide can diffuse quickly to all the cells in the leaf.
B4.15 Glucose is soluble and fairly reactive.
B4.16 nitrogen (in a reactive form, such as nitrates)
B4.17 Nitrate ions are needed for making amino acids. These in turn are used to make proteins, and proteins are needed for growth.
B4.18 Sucrose, produced by photosynthesis in the leaves, is supplied to them through phloem sieve tubes.
Chapter B5 Animal nutritionB5.01 a Carbohydrates, fats, proteins and vitamins are
organic. Minerals and water are inorganic.
b carbohydrates, fats and proteins
c to stimulate peristalsis and prevent constipation
B5.02 heart disease, diabetes, stroke
B5.03 a disease of the coronary arteries of the heart, which become partially blocked by deposits of cholesterol, preventing sufficient oxygen reaching the heart muscle
B5.04 Starvation means not getting enough food. Malnutrition means having an unbalanced diet, perhaps a diet lacking in one nutrient or containing too much fat.
B5.05 a disease caused by a lack of a particular nutrient in the diet
B5.06 scurvy (lack of vitamin C); rickets (lack of vitamin D); brittle bones (lack of calcium); anaemia (lack of iron)
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B5.07 the breakdown of large, insoluble food molecules into small molecules using mechanical and chemical processes
B5.08 vitamins and minerals (and water)
B5.09 a simple sugars (glucose) b amino acids
c fatty acids and glycerol
B5.10 breaking down large molecules of food into small ones, using enzymes
B5.11 the teeth at the front of the mouth, used for biting off pieces of food
B5.12 a mix of food remnants and bacteria coating the teeth
B5.13 Bacteria in plaque can breed and penetrate between the tooth and the gums, causing inflammation and eventually even loss of the tooth. Bacteria in plaque produce acids when they metabolise foods. The acid dissolves enamel, producing a hole through which bacteria can reach the living part of the tooth.
B5.14 The mouth (in saliva); the small intestine (in pancreatic juice). It breaks down starch to maltose.
B5.15 The acid provides the optimum pH for pepsin to work, and destroys bacteria in the food.
B5.16 pancreatic juice and bile
B5.17 Bile salts emulsify fats, making it easier for lipase to come into contact with them and digest them.
Chapter B6 Transport in plantsB6.01 water and inorganic ions such as nitrate
B6.02 sucrose and amino acids
B6.03 a collection of xylem vessels and phloem tubes
B6.04 Water moves into root hairs by osmosis, down its water potential gradient (or from a less concentrated solution to a more concentrated one), through the partially permeable cell membrane of the root hair cells.
B6.05 evaporation of water from the surfaces of mesophyll cells followed by loss of water vapour from plant leaves, through the stomata
B6.06 small holes, mostly on the lower surface of a leaf, each surrounded by a pair of guard cells, through which gases can diffuse into and out of the leaf
B6.07 measuring the rate at which a shoot takes up water (and therefore the rate at which it loses water by transpiration)
B6.08 a An increase in temperature increases the rate of transpiration. (This happens because, at higher temperatures, water molecules have more kinetic energy. They are more likely to turn from liquid to gas, and will diffuse more rapidly out of the leaf.)
b An increase in humidity decreases the rate of transpiration. (This happens because the greater quantity of water vapour in the air outside the leaf means that the diffusion gradient for water vapour is less.)
Chapter B7 Transport in animalsB7.01 a system of blood vessels with a pump and valves
to ensure one-way flow of blood
B7.02 blood containing a lot of oxygen
B7.03 the lungs
B7.04 the left side
B7.05 In a double circulatory system, blood flows from the heart to the lungs, and then back to the heart again before travelling to the rest of the body. In a single circulatory system, blood flows directly from the lungs or gills to the rest of the body.
B7.06 In a double circulatory system, oxygenated blood is transported to body cells faster, at higher pressure.
B7.07 a left atrium b right atrium
B7.08 between the atria and the ventricles
B7.09 a right ventricle b left ventricle
B7.10 They contain more cardiac muscle, which can therefore provide a greater force when they contract. This is needed to pump the blood around the body.
B7.11 It contains more cardiac muscle, needed to produce more force to pump blood all around the body rather than just to the lungs.
B7.12 The pulse is the regular expansion of arteries, caused by blood surging through at high pressure each time the ventricles contract.
B7.13 to move oxygenated blood to the muscles more quickly, to supply the oxygen they need to release energy from glucose, by respiration
B7.14 a patch of muscle in the right atrium which sets the pace for the beating of the rest of the heart muscle
Answers to questions
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B7.15 Extra CO2 (from respiring muscles) dissolves in blood plasma, reducing its pH. This is sensed by receptors in the brain, which increases the frequency of nerve impulses sent to the pacemaker.
B7.16 The valves are pushed closed by the high pressure of the blood in the ventricles. This prevents blood flowing back into the atria.
B7.17 a arteries b veins
B7.18 The pressure of the blood in arteries is high and pulsing, so the strong walls are needed to withstand this pressure.
B7.19 The elastic walls allow the arteries to expand with each pulse of pressure (produced by the heart) and then recoil in between pulses; if they could not do this, they might burst.
B7.20 Capillaries deliver blood, containing oxygen and nutrients, very close to every cell in the body.
B7.21 A large lumen provides less resistance to blood flow, needed because blood pressure in the veins is low.
B7.22 Skeletal muscles in the legs squeeze inwards on the veins when the muscles contract, pushing blood along inside them.
B7.25 They have no nucleus, and contain haemoglobin. They have a biconcave shape.
B7.26 a red pigment that absorbs and releases oxygen; a protein found inside red blood cells
B7.27 tiny fragments of cells that help with blood clotting
Chapter B8 Respiration and gas exchangeB8.01 to release energy from glucose for cells to use
B8.02 active transport; driving chemical reactions such as protein synthesis; movement; producing heat; transmitting nerve impulses; cell division
B8.03 the release of a relatively small amount of energy by the breakdown of food substances in the absence of oxygen
B8.04 yeast, humans (for short periods of time)
B8.05 It produces lactic acid. It does not produce CO2. It releases less energy.
B8.06 It produces lactic acid, not ethanol. It does not produce CO2.
B8.07 the voice box
B8.08 They sweep mucus, which contains trapped bacteria and dust particles, up to the top of the trachea and into the throat, where it can be swallowed.
B8.09 across the walls of the alveoli
B8.10 two
Chapter B9 Coordination and homeostasisB9.01 any muscles or glands
B9.02 nerves and hormones (the nervous system and the endocrine system)
B9.03 They have a nucleus, cell membrane and cytoplasm.
B9.04 They have a long axon (or dendron) to transmit impulses rapidly from one part of the body to another. They have nerve endings to pass the impulses onto another nerve cell or an effector. They (may) have a myelin sheath around the axon (or dendron) to speed up the impulses. They have dendrites to receive nerve impulses from other cells.
B9.05 The CNS receives inputs from different receptors, which it integrates, and produces nerve impulses to send to appropriate effectors.
B9.06 a in a small swelling just outside the spinal cordb in the central nervous system – either the
brain or the spinal cordc in the central nervous system – either the
brain or the spinal cord
B9.07 They produce very quick, automatic responses with no time wasted in making decisions. This can enable escape from danger.
B9.08 There are many possibilities. Answers should state the stimulus and the response.
B9.09 a change in the environment that is detected by a receptor
B9.13 changing the shape of the lens to focus light rays from different distances onto the retina
B9.14 a contract
b i This reduces tension on the suspensory ligaments
ii which allows the lens to become its natural, rounded shape.
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B9.15 dissolved in blood plasmaB9.16 any situation in which you are nervous, frightened
or angryB9.17 It increases glucose concentration in the blood,
so muscles can use more for respiration; it increases heart rate, increasing the supply of glucose and oxygen to muscles; it increases breathing rate – similar effect.
B9.18 the tipB9.19 just behind the tipB9.20 Auxin made in the tip diffuses down into the part
just below the tip. Auxin is like an animal hormone, a chemical that is made in one part of the body and moves to another where it has an effect. However, auxin is not made in an endocrine gland like animal hormones, and it is not transported in the blood.
B9.21 It moves the leaves towards a light source, maximising the amount of light available for photosynthesis.
B9.22 It grows towards it.B9.23 It stores fat as an energy reserve, which can be
used in respiration to release energy for cells to use. It acts as a heat insulator, preventing loss of heat from the body to the external environment.
B9.24 The water in sweat evaporates. This requires energy, which is taken from the skin, thus cooling it.
B9.25 hypothalamusB9.26 Vasodilation is the widening of the arterioles
supplying the blood capillaries near the surface of the skin. It allows more blood to flow through these capillaries, losing heat by radiation through the skin surface.
B9.27 When a parameter changes in a particular direction, this is sensed and measures are put into place to change it back towards the norm.
Chapter B10 Reproduction in plantsB10.01 In asexual reproduction, there is only one
parent. Cells divide by a type of cell division that produces genetically identical cells, so the offspring are genetically identical to their parent and to each other.
B10.02 a haploid cell that fuses with another haploid gamete to produce a zygote – for example, an egg or a sperm
B10.03 a diploid cell formed by the fusion of the nuclei of two gametes
B10.04 so that when their nuclei fuse at fertilisation, the new cell formed will have the normal two sets of chromosomes
B10.05 a cell with two complete sets of chromosomes
B10.06 any part of the body
B10.07 a cell with one set of chromosomes
B10.08 egg or sperm
B10.09 sexual reproduction
B10.10 anthers
B10.11 ovules
B10.12 the transfer of pollen grains from the male part of the flower (anther of stamen) to the female part of the flower (stigma)
B10.13 Much of the pollen of wind-pollinated flowers will not land on the stigma of a flower of the same species and will be wasted. The pollen of insect-pollinated flowers is more likely to be delivered to an appropriate flower.
B10.14 down a tube that grows out of the pollen grain, through the style and into the ovule
Chapter B11 Reproduction in humansB11.01 cervixB11.02 where the two sperm ducts join the urethra; it
produces fluid for sperm to swim inB11.03 An egg bursts out of an ovary, and is caught in
the funnel of the oviduct.B11.04 in the testesB11.05 Cilia in the wall of the oviduct waft it along.B11.06 in the oviductsB11.07 Sperm are much smaller than eggs. Sperm can
swim but eggs cannot. Sperm have a head, a long tail, and enzymes in a vesicle in the head. Eggs have none of these, but they have a layer of jelly surrounding them.
B11.08 when the embryo sinks into the lining of the uterusB11.09 a developing baby in the uterus from about the
11th week after fertilisationB11.10 by the umbilical cord, which contains two
arteries and a veinB11.11 oxygen; glucose; any other soluble nutrients;
waterB11.12 so that it is prepared for the arrival of an embryo
if an egg is fertilisedB11.13 It is lost through the vagina.
Answers to questions
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Chapter B12 InheritanceB12.01 DNA
B12.02 a pair of chromosomes that carry the same genes in the same positions
B12.03 different forms of a gene
B12.04 a B and b (or any other upper and lower case versions of the same letter)
b brown eyes
B12.05 23
B12.06 a Nn b N or nB12.07 normal wings normal wings
NN Nn
NNnormal wings
Nnnormal wings
NN
N
N nn
All the offspring would have normal wings.
B12.08 a
B BB
B
b bb
b
brown hair brown hairBb Bb
BBbrown
hair
Bbbrown
hairBb
brown hair
bbred hair
If both parents were heterozygous, then both can produce gametes containing the b alleles. If two such gametes fuse to form a zygote, the resulting child will have the genotype bb and have red hair. The chance of this happening is one in four each time they have a child. By chance, this has happened three times out of five.
b Person 1 must be heterozygous, Bb, because at least two of his children have red hair and so must have inherited a b allele from both parents.
Person 3 has red hair, and so must have the genotype bb.
Person 2 must also be heterozygous, Bb, for the same reason. He has brown hair.
B12.09 She could breed the black-spotted dog with a liver-spotted dog. If the dog is heterozygous:
black spots liver spotsBb bb
b
bBb
black spots
bbliver spots
B
B
b
If the black-spotted dog is homozygous, all of its gametes will have the allele B, so all the offspring will have the genotype Bb and will have black spots. Therefore, if any of the offspring have liver spots, the breeder knows that the genotype of the black-spotted dog is Bb.
Chapter B13 Variation and natural selectionB13.01 a discontinuous b continuous
c continuousd discontinuous
B13.02 a and d genes only
b and c genes and environment
B13.03 The more that populations of bacteria are exposed to an antibiotic, the more likely that bacteria resistant to this antibiotic will gain an advantage over non-resistant bacteria. These will breed and pass on their resistance genes to the next generation.
B13.04 Choose sperm from a bull whose female offspring and other female relatives have high milk yields. Choose a cow that has a high milk yield, and fertilise her eggs with sperm from the chosen bull. Continue for several generations.
B13.05 a Grow wheat in conditions where it gets infected by rust. Collect seed from any plants that are not infected, or that are not harmed. Grow this seed and repeat for several generations, each time picking out seed from plants that are least affected by rust.
b Some of the rust organisms may have a variation that allows them to infect the resistant wheat plants. These will have a selective advantage, and be more likely to
Cambridge IGCSE Combined and Co-ordinated Sciences
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survive and reproduce, passing on the genes for this characteristic to the next generation of rust fungi. Over time, most of the rust fungi may have this gene and be able to infect the previously resistant wheat plants.
Chapter B14 Organisms and their environmentB14.01 Almost all the energy in living organisms on
Earth originates from sunlight. (There are deep-sea ecosystems that are based on energy from geothermal vents on the ocean floor, but the vast majority of life on Earth is ultimately driven by solar energy.)
B14.02 a One example might be: Sun → maize (grown for fodder) → cattle → human.
b One example might be: Sun → phytoplankton → zooplankton → fish → seal → shark.
c One example might be: Sun → grass → grasshopper → rat → snake → hawk.
B14.03 because, in photosynthesis, they use energy from sunlight to produce the food that then powers the rest of the food chain
B14.04 The further up the food chain you go, the less energy is available from the original energy provided by the Sun. This is because, at each trophic level, the organisms use up a lot of energy as they live and grow, so there is less available to pass on to animals that eat them. Beyond about five links in a chain, the energy has effectively run out.
B14.05 photosynthesis
B14.06 protein or any named proteins, carbohydrates or a named carbohydrate (glucose, glycogen), fats
B14.07 It will increase, because the combustion of fossil fuels produces carbon dioxide that is released into the air.
B14.08 Growing trees take carbon dioxide from the air for photosynthesis. If trees are removed, then less carbon dioxide is removed. If the trees are burnt, this produces carbon dioxide that goes into the air.
B14.09 Tree roots help to hold soil in place, especially on sloping land. Without trees, rain can easily wash the soil down the slope. Trees intercept raindrops as they fall, reducing the force with which they hit the soil. Without trees, rain hits the ground
harder, so that soil is loosened and washed away. Trees absorb water from the soil. Without trees, less water is absorbed and more runs off the surface of the land, increasing soil erosion and flooding.
B14.10 untreated sewage, fertilisers
B14.11 oxygen
B14.12 Plastic bags are not able to be decomposed by organisms. Instead, they remain in the environment, where they can cause problems such as being eaten by animals and staying, undigested, in their alimentary canals. Paper bags are easily broken down by decomposers.
ChemistryChapter C1 Planet EarthC1.01 sulfur dioxide and nitrogen dioxide
C1.02 the burning of fossil fuels (mainly coal for sulfur dioxide)
C1.03 damage to limestone buildings, death of trees, acidification of lakes leading to death of fish
C1.04 a combination of nitrogen oxides and low-level ozone that causes breathing problems, especially for people with asthma
C1.05 It combines with the haemoglobin in red blood cells, stopping them from carrying oxygen.
C1.06 because it does not react with the filament, which would burn in air when it became hot
C1.07 Heat which would normally escape into space is reflected back to the Earth’s surface by gases such as carbon dioxide and methane in the atmosphere.
C1.08 It changes nitrogen oxides and carbon monoxide to nitrogen and carbon dioxide.
C1.09 because solid matter is easiest to remove and would interfere with subsequent processes
C1.10 to kill bacteria present in the water
C1.11 because the energy needed to boil the water is costly
C1.12 It contains a high concentration of a particular metal compound.
C1.13 Lime is calcium oxide, which is reacted with water to make calcium hydroxide (slaked lime).
C1.14 It reflects heat back to Earth when present in the atmosphere. Heat is kept in the atmospheric layer.
Answers to questions
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Chapter C2 The nature of matterC2.01 a freezing (solidification) b boiling
c condensationd sublimation
C2.02 The impurity lowers the freezing point of the liquid.
C2.03
–20
Time
0
80
liquid
solid
freezing Tem
pera
ture
/°C
C2.04 A volatile liquid is one that evaporates easily; it has a low boiling point.
C2.05 ethanol > water > ethanoic acid. Ethanol is the most volatile, ethanoic acid the least.
C2.06 a distillation b fractional distillation
c crystallisation (evaporation to concentrate the solution, cooling, crystallisation, filtration and drying)
C2.07 Sublimation is when a solid changes to a gas without passing through the liquid phase (and the reverse).
C2.08 coloured substances (e.g. dyes)
C2.09 by the use of locating agents that react with colourless ‘spots’ to produce a colour that can be seen
C2.10 Rf gives a standard measure of how far a sample moves in a chromatography system, as it relates the movement of the sample compound to how far the solvent front has moved. It is equal to the distance moved by the sample divided by the distance moved by the solvent front.
C2.11 An element is a substance that cannot be broken down into anything simpler by chemical means.
C2.12 A compound is a substance formed from two or more elements chemically bonded together.
C2.13 solid: particles packed close together in a regular arrangement; each particle only vibrating about a fixed point
liquid: particles close together but less regularly arranged; particles able to move about
gas: particles far apart and irregularly arranged; particles moving independently
C2.14 Ammonia, because it has a lower molecular mass. Place cotton wool plugs soaked in ammonia solution and hydrochloric acid at opposite ends of a tube. Seal the tube at both ends. Allow the gases to diffuse towards each other. A white smoke disc of ammonium chloride will form where the two gases meet. This disc is closer to the hydrochloric acid end of the tube, as ammonia diffuses faster.
C2.18 Chlorine-37 has two more neutrons in the nucleus.
C2.19 first shell, maximum 2; second shell, maximum 8
C2.20 2,8,8,2
C2.21 8 in both cases
C2.22 6 in both cases
Chapter C3 Elements and compoundsC3.01 fluorine
C3.02 2
C3.03 the bottom of Group I
C3.04 Metal: can be beaten into sheets, gives a ringing sound when hit, conducts heat, conducts electricity
Non-metal: is an insulator, has a dull surface
C3.05 Helium has a full first shell. The others all have 8 electrons in the outer energy level (shell/orbit).
C3.06 potassium hydroxide
C3.07 lithium + water → lithium hydroxide + hydrogen
C3.08 It is used in the treatment of drinking water; it will bleach moist litmus paper.
C3.09 chlorine and fluorine
C3.10 metal to non-metal
C3.11 aluminium
C3.12 sodium
C3.13 Cl2
C3.14 silicon
C3.15 because copper is a transition metal
C3.16 a covalent b covalent c ionic d metallic
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C3.17 because in hydrogen gas two atoms are covalently bonded together
C3.18 an electrostatic force (attraction between two oppositely charged ions)
C3.19 a H H
b
H O
H
c
H HN
H
d H
H
H C H
C3.20 a
[Na]+ Cl
–
b
F[Li ]+
–
C3.21 The calcium ion is ionically bonded to the carbonate ion but the carbonate ion is held together by covalent bonds.
C3.22 a
[Mg]2+ O
2–
b
[Ca]2+
Cl
–
Cl
–
C3.23 a sodium iodide b magnesium sulfide
c potassium oxided lithium nitride
e calcium hydroxidef nitrogen monoxideg nitrogen dioxideh sulfur trioxide
C3.24 a SiCl4 b CS2
c PCl3 (or PCl5) d SiO2
C3.25 a i Na = 1, O = 1, H = 1 ii C = 2, H = 6 iii H = 2, S = 1, O = 4 iv Cu = 1, N = 2, O = 6 v C = 12, H = 22, O = 11
b i potassium bromide ii aluminium hydroxide iii copper carbonate iv magnesium nitride v phosphorus trichloride vi nitric acid vii silicon tetrachloride viii iron(ii) sulfate ix methane x sulfuric acid c i K2SO4
ii AlF3
iii Fe2O3
iv Ca(NO3)2
v ZnCl2
vi NH3
vii HCl viii CuSO4
ix SO3
C3.26 a carbon, hydrogen and oxygen b 8
c carbon and oxygend 4e A liquid: it is a small covalent molecule.f No, it is covalently bonded.
C3.27 The ions are free to move and they carry the charge.
C3.28 because the ions are fixed in position and cannot move
C3.29 a There are electrons between the flat planes of atoms which are free to move.
b There are only weak forces between the layers in graphite and therefore they can slide over each other.
C3.30 because, in diamond, each carbon atom is attached to four other carbon atoms, making a strong lattice
Answers to questions
10
C3.31 because there are no charged particles to move around
C3.32 because there are electrons which are free to move in solid metals
C3.33 Both substances have a three-dimensional structure in which the atoms are arranged tetrahedrally and all the atoms are joined by covalent bonds.
Chapter C4 Chemical reactionsC4.01 a physical
b chemical
c physical
d physical
C4.02 a exothermic
b exothermic
c exothermic
d endothermic
C4.03 A new substance(s) has been formed.
C4.04 a iron + oxygen → iron(iii) oxide
b sodium hydroxide + sulfuric acid → sodium sulfate + water
b Iodine is less reactive than chlorine so it will not displace chlorine from its salts.
C4.07 a combustion
b decomposition
c redox
d neutralisation
C4.08 a sodium + water → sodium hydroxide + hydrogen
2Na + 2H2O → 2NaOH + H2
b magnesium + steam → magnesium oxide + hydrogen
Mg + H2O → MgO + H2
c calcium + oxygen → calcium oxide
2Ca + O2 → 2CaO
d bromine + potassium iodide → potassium bromide + iodine
Br2 + 2KI → 2KBr + I2
e zinc + copper sulfate → zinc sulfate + copper
Zn + CuSO4 → ZnSO4 + Cu
C4.09 a Solid sodium carbonate reacts with hydrochloric acid solution to give sodium chloride solution and carbon dioxide gas. Water, a liquid, is also produced.
b i Ag+ (aq) + Cl–(aq) → AgCl(s) ii Ba2+(aq) + SO4
2–(aq) → BaSO4(s) iii H+(aq) + OH–(aq) → H2O(l) iv 2H+(aq) + CO3
2–(s) → H2O(l) + CO2(g)
C4.10 Reduction is the gain of electrons; oxidation is the loss of electrons. During a redox reaction the oxidising agent gains electrons; the oxidising agent is itself reduced during the reaction.
C4.11 a The compound is split into its elements.b The ions are not free to move in the solid, so
they cannot move to the electrodes to be discharged.
c The vapour is brown.d because bromine vapour is toxice the cathode
C4.12 a the cathodeb copper sulfate solution
C4.13 a 2Br – → Br2 + 2e–
b because electrons are gained by the lead ions
C4.14 Solution (electrolyte)
Gas given off at the anode
Gas given off or metal deposited at the cathode
Substance left in solution at the end of electrolysis
C5.30 a carbonate + hydrochloric acid → salt + water + carbon dioxide
C5.31 blue precipitate, copper(ii) hydroxide
C5.32 Ammonia solution; you get a white precipitate in both cases but the zinc hydroxide precipitate re-dissolves in excess ammonia and the aluminium hydroxide precipitate does not.
C5.33 pink (purple)
C5.34 to make sure all the acid is used up/reacted
C5.35 filtration
C5.36 pipette, burette
C5.37 If heated too strongly, the salt could dehydrate (lose water of crystallisation) or even decompose.
C5.38 a i method B ii sulfuric acid iii zinc oxide + sulfuric acid
→ zinc sulfate + water b i method A ii hydrochloric acid iii KOH + HCl → KCl + H2O
Chapter C6 Quantitative chemistryC6.01 a covalent
b ionic
c CH4, NaI, C3H6, ICl3, BrF5, HBr
Answers to questions
12
C6.02 a 32 b 17
c 64 d 114
e 98 f 119
g 188 h 133.5
C6.03 a 0.20 g; 0.18 g; 0.08 g; 0.12 g
b
0
0.1
0
0.2
0.1
Mass of magnesium /g
Mas
s of o
xyge
n/g
0.2 0.3
c The graph is a straight line, showing a fixed ratio of oxygen to magnesium; this indicates a fixed formula.
C6.04 a i near the neck of the test tube ii to flush out all of the air from the tube iii to make sure the reaction was
complete b i C = 1.60 g, E = 1.28 g, F = 0.32 g ii 0.02 moles iii 0.02 moles iv 1 mole v CuO vi copper(ii) oxide + hydrogen
→ copper + water CuO + H2 → Cu + H2O
C6.05 a 0.02 moles b 2 moles c 0.07 moles
C6.06 a 36 000 cm3 b 1440 cm3
c 12 000 cm3
C6.07 a 2 mol/dm3 b 0.2 mol/dm3
c 1 mol/dm3
d 0.8 g of NaOH = 0.2 moles; 0.2 mol/dm3
Chapter C7 How far? How fast?C7.01 endothermic
C7.02 endothermic
C7.03 Polystyrene is a good insulator (and absorbs very little heat itself).
C7.04
Progress of reaction
ZnSO4 (aq) + Cu(s)
Zn(s) + CuSO4(aq)EA
Ener
gy
C7.05 a rate increases b rate increases c rate increases
C7.06 The reactions which would spoil the food are slowed down at the lower temperature.
C7.07 at the beginning
C7.08 because the reactants are being used up
C7.09 A catalyst is a substance that speeds up a chemical reaction but is not itself used up in the course of the reaction.
C7.10 a biological catalyst
C7.11 manganese(iv) oxide
C7.12 a iron b vanadium(v) oxide
C7.13 changes in temperature and pH
C7.14 The presence of a catalyst decreases the activation energy of reaction.
C7.15 a An increased temperature means that the particles are moving faster and will therefore collide more frequently; when they collide, more particles will have energy greater than the activation energy so there will be more collisions that result in a reaction.
b There will be more surface area of the solid exposed to the reactant and therefore more frequent collisions.
c Greater concentration means there are more reactant molecules present and so there will be a greater frequency of collision.
C7.16 white to blue
C7.17 the presence of water
Chapter C8 Patterns and properties of metalsC8.01 They are soft and have a low density.
C8.02 Sodium gives a yellow flame, potassium a lilac flame.
C8.03 hydrogen
C8.04 potassium hydroxide
C8.05 sodium + water → sodium hydroxide + hydrogen
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C8.06 2K + 2H2O → 2KOH + H2
C8.07 lithium
C8.08 It is strong but light and it does not corrode.
C8.09 It is more reactive than carbon (so its oxide cannot be reduced by carbon).
C8.10 A thin layer of aluminium oxide forms on the surface of the metal and sticks to it, giving it a protective coating; with iron, the oxide forms but flakes off and so does not protect the metal.
C8.11 They are strong and dense, have high melting points, their compounds are often coloured, they can show more than one valency, they or their compounds often act as catalysts (any three).
Chapter C9 Industrial inorganic chemistryC9.01 to combine with the silicon dioxide (sand) and
remove it as slag
C9.02 Fe2O3 + 3CO → 2Fe + 3CO2
C9.03 oxygen
C9.04 to make an alloy which doesn’t corrode (stainless steel)
C9.05 water and oxygen (air)
C9.06 It can be used to coat iron (galvanisation) or can be attached to iron as blocks (cathodic protection).
C9.07 because of the high cost of electricity, which is needed in large quantities
C9.08 because this makes the temperature needed to melt the aluminium oxide much lower
C9.09 because the oxygen produced at the anode causes them to burn away
C9.10 Al3+ + 3e– → Al
C9.11 because it forms an oxide layer which prevents any further reaction with oxygen (corrosion)
C9.12 by reacting methane gas with steam
C9.13 an iron catalyst, a moderately high temperature (450 °C) and a high pressure (200 atmospheres)
C9.14 so that they react the second time around (saves producing more raw materials)
C9.15 because these are the three elements needed by plants which can become used up in soil
C9.16 They are washed off fields by rain and end up in streams and rivers.
C9.17 S + O2 → SO2
C9.18 a catalyst (vanadium(v) oxide) and a temperature of around 450 °C
C9.19 because the reaction is too violent: a mist of sulfuric acid is formed which is very dangerous
C9.20 a concentrated solution of sodium chloride in water
C9.21 It converts a cheap raw material (common salt) into three important chemicals: chlorine, hydrogen and sodium hydroxide. There are no waste products.
C9.22 to neutralise acidity in the water
C9.23 to remove silicon dioxide (sand) from the iron ore
C9.24 CaCO3 → CaO + CO2
C9.25 Ca(OH)2
C9.26 treating soil to remove excess acidity; removing impurities from iron during the basic oxygen steel making process
C9.27 because it is quick to recycle, and ‘new’ aluminium is very expensive to produce
C9.28 conserving non-renewable resources such as metal ores; avoiding dumping waste in landfill
b It is an air-lock – allowing the carbon dioxide to escape but not allowing air/bacteria in.
c yeast
d at around 37 °C
e This is the temperature favoured by the yeast, which are living organisms.
C10.25 a
methanol ethanol
O HH C
H
H
O HH C
H
H
C
H
H
b A homologous series of compounds is a family of organic compounds that have the same general formula, similar chemical properties and a gradual trend in their physical properties.
Chapter C11 Petrochemicals and polymersC11.01 refinery gas, petrol (gasoline), naphtha, kerosene
(paraffin), diesel, bitumenC11.02 coal, natural gas, petroleum (crude oil)C11.03 Cracking is the thermal decomposition of a long-
chain alkane to a shorter-chain alkane and an alkene (or hydrogen).
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C11.06 Addition polymerisation takes place when many molecules of an unsaturated monomer join together to form a long-chain polymer.
C
H
H
C
H
H n
C CH
high pressure
heat, catalystn
H
H
H
C11.07 a C
H
H
C
H
CH3
b C
H
H
C
H
Cl
C11.08 tetrafluoroethene
C11.09 a crates/plastic rope
b insulation/pipes
c non-stick pans/gear wheels
C11.10 The monomers join together by a reaction in which a small molecule (usually water) is eliminated each time a link is made.
C11.11 a the amide link (or peptide link)
b C
O
C
O
C
O
C
O
N
H
N
H
. . . . . .N
H
N
H
Chapter C12 Chemical analysis and investigationC12.01 because their hydroxides are insoluble and form
as precipitates
C12.02 aluminium and zinc hydroxides
C12.03 because iron has two different oxidation states (iron(ii) and iron(iii))
C12.04 carbon dioxide
C12.05 silver nitrate
C12.06 nitric acid
C12.07 oxygen
C12.08 the ammonium ion
C12.09 a D b E c A d CC12.10 Add bromine water: it turns from brown to
colourless.
C12.11 the amount of water, the amount of fuel used, or the time it was used for
C12.12 substance, appearance before heating, appearance during heating, appearance after cooling
PhysicsChapter P1 Making measurementsP1.01 3.23 mm
P1.02 1968 cm3
P1.03 a 0.71 mm b 158 mm3
P1.04 18 cm3
P1.05 13.2 g/cm3
P1.06 7.6 g/cm3
P1.07 80 cm3; 7.75 g/cm3
P1.08 0.04 s
P1.09 0.87 s; 0.864 s
Chapter P2 Describing motionP2.01 inches per minute
P2.02 s/m, ms
P2.03 a fastest: C b slowest: B
P2.04 250 m/s
P2.05 75 km/h
P2.06 1728 000 km
P2.07 3.33 h (3 h 20 min)
P2.08
Time
Dist
ance
P2.09
Time
Spee
d
P2.10 a A, C, G b Fc E d B, D
Answers to questions
16
P2.11 a, b
Time / s
10
8
6
4
2
0105 6 7 8 943210
Spee
d / m
/s
c 45 m
P2.12
Dist
ance
/ km
40
30
20
10
0
Time / min403010
50
20 50 070 60
32 km/h
P2.13 km/sP2.14 1.5 m/s2
P2.15 0.20 m/s2
P2.16 a
0 10 155 200
10
5
20
15
Time / s
Spee
d /
m/s
b 2.5 m/s2
c 280 m
Chapter P3 Forces and motionP3.01 a accelerate to right
b slow down / accelerate to leftc change direction
P3.02 a i unbalanced ii 20 N to right iii accelerate to right b i balanced ii no resultant force iii no acceleration c i unbalanced ii 50 N downwards iii accelerate downwardsP3.03 a mass = 1 kg; weight is less than 10 N
b mass = 1 kg; weight is greater than 10 N
P3.04 a 900 N b 333 N
P3.05 1500 N
P3.06 2.0 N
P3.07 25 m/s2
P3.08 800 kg
Chapter P4 Turning effects of forcesP4.01 force F3 at end; it is at 90° to trapdoor and furthest
from the pivot
P4.02 The force of the wind has a greater turning effect on a tall tree.
P4.03 X = 1000 N; Y = 1400 N
P4.04 Z = 90 N; 1.50 m
P4.05 a This is to lower their centre of mass.
b The block on the arm is there to balance the load. The blocks at the base are to lower its centre of gravity, broaden its base and make it more stable.
P4.06 a The forces are equal and along the same straight line, so there is no moment.
b No, because there is an unbalanced force to the right.
c The cyclist is unstable, because the forces are not balanced.
Cambridge IGCSE Combined and Co-ordinated Sciences
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P5.03 7.5 N
P5.04 24 N
P5.05
Load / N
120100
80604020
01210 115 6 7 8 94
limit of proportionality
3210
Exte
nsio
n / m
m
load at the limit of proportionality = 8.0 N
P5.06 p = FA
P5.07 pascal, Pa
P5.08 100 N on 1 cm2
P5.09 20 000 Pa
P5.10 600 000 N
P5.11 a 3.0 m3 b 27 600 N c 9200 Pa
Chapter P6 Energy transformations and energy transfersP6.01 kinetic energy
P6.02 thermal (heat) energy, light energy
P6.03 elastic potential energy
P6.04 gravitational potential energy; raise it upwards
P6.05 loudspeaker, buzzer, and so on
P6.06 light, sound, heat
P6.07 Energy stores Examplekinetic energy moving cargravitational potential energy
water in cloud
chemical energy petrolnuclear energy uraniumstrain energy wound-up clockwork
toyinternal energy hot water bottle
P6.08 a chemical energy of fuel → internal energy of room and water
b electrical energy → light and heatc electrical energy → heat, k.e. and sound
P6.09 a 100 J b 90 J
P6.10 a heat b sound
P6.11 harms the environment; wastes limited resources; costs money
P6.12 60%
P6.13 25%
P6.14 200 J
P6.15 a decreasing b constant c increasing
P6.16 1000 J
P6.17 100 m
P6.18 speed
P6.19 0.5 J
P6.20 2560 J
P6.21 wasp
Chapter P7 Energy resourcesP7.01 Both are variable (more wind and waves some
days than others).
P7.02 light energy → electrical energy (+ heat)
P7.03 k.e. and g.p.e.
P7.04 a coal, oil, gasb wood, charcoal, peat (also straw and others)
P7.05 chemical energy → heat (+ light)
P7.06 Nuclear energy is converted to heat energy and electrical energy.
P7.07 a non-renewable – because uranium is used upb renewable – because new waves appear
every day
P7.08 uranium (nuclear fuel), geothermal energy, tidal energy
Chapter P8 Work and powerP8.01 15 kg of feathers
P8.02 gravity
P8.03 joule (J)
P8.04 0.50 MJ
P8.05 a 1.0 J b 10 J
P8.06 500 N through 10 m
P8.07 none – it is not moving
P8.08 lift more bricks at a time (greater force); lift them faster
P8.09 a 1000 b 1 000 000
P8.10 40 J/s
P8.11 100 W
P8.12 increased
Answers to questions
18
Chapter P9 The kinetic model of matterP9.01 A liquid takes up the shape of a container without
its volume changing.
P9.02 boiling point (or condensing point)
P9.03 a solidification or freezingb freezing point or melting point
P9.04 a Water is becoming hotter.b Water and steam are present.
P9.05 Air is a mixture, so it does not have fixed melting and boiling points.
P9.06 a because the particles are moving (they have kinetic energy)
b gas
P9.07 a solid b gas
P9.08 Air is a gas and water is a liquid. In these states, the particles can move past each other, so we can push past them. In a solid, such as a wall, particles are in fixed positions, so that we cannot push them apart.
P9.09 a Water molecules are too small to see.b It was constantly jostled by molecules of the
water.
P9.10 Forces between tungsten atoms are stronger than forces between iron atoms.
P9.11 a It is melting.b Energy is required to break bonds between
particles (it increases their potential energy).
P9.12 The pressure will increase because the force of the molecules on the walls of the container will be greater (and collisions will be more frequent).
P9.13 a halved b halved c remains the same
P9.14
volume doubled
The volume is doubled but the number of particles remains the same, so their collisions with the walls are half as frequent.
P9.15 Decrease the temperature so that the particles move more slowly. Then they will collide with the walls with less force, and less frequently.
Chapter P10 Thermal properties of matterP10.01 a The cold water gets hotter and expands. As its
volume increases, it pushes further up the tube.b Set up two identical flasks, one with water,
the other with paraffin. Add a thermometer to each. Place both in a hot water bath. Record the level of the liquid in the tube as the temperature increases.
P10.02 a The 2 kg of water at 30 °C has twice as much internal energy as 1 kg. The internal energy of the water is made up of the energies of all the molecules. There are twice as many molecules in 2 kg.
b The temperature is the same (because the average energy of a molecule is the same in each bucket).
c The average energy per molecule is the same, as they are at the same temperature.
P10.03 0 °C = melting point of pure ice 100 °C = boiling point of pure water
P10.04 Place thermometer in pure melting ice and mark 0 °C. Place in pure boiling water and mark 100 °C. Divide the scale between these two into 100 equal units.
P10.05 As the temperature rises, the air in the flask expands and pushes downwards, so that the water level drops.
P10.06 a approximately 40 to 50 °Cb At 20 °C, the resistance changes only a little
for each degree change in temperature. It changes more rapidly around 50 °C.
P10.07 The temperature-sensitive junction of the thermocouple is very small and can heat up or cool down more rapidly than the bulb of a mercury thermometer.
Chapter P11 Thermal (heat) energy transfersP11.01 a copper, steel, other metals
b air, wood, plastic, glass
P11.02 a temperature difference
P11.03 marble (it has a greater thermal conductivity)
P11.04 convection
P11.05 a Particles of hot gas move faster.b Particles of hot gas are further apart.
P11.06 When a fluid is heated, its expansion causes its density to decrease. It rises because it is less dense than the surrounding air. Cooler, denser air sinks as a result of the pull of gravity.
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P11.07 Warm air rises above the heater, and moves around the room. Cold air flows in to replace it and so is heated.
P11.08 No convection current would be established because the air heated by the heater cannot rise.
P11.09 radiation
P11.10 infrared, ultraviolet
P11.11 The rate of infrared emission increases.
P11.12 a Matt black is a better absorber.b Matt black is a better emitter.c Shiny black is a better reflector.
P11.13 Lids reduce heat loss by convection. Wooden or plastic surfaces reduce heat loss by conduction.
P11.14 Feature Reduces conduction?
Reduces convection?
Reduces radiation?
double glazing
yes yes yes (if coated)
cavity wall insulation
yes yes yes
carpet, underfloor insulation
yes no no
draught excluders
no yes no
curtains yes yes no
loft insulation (with shiny foil)
yes yes yes
P11.15 Heat is lost from head by convection, and a hat greatly reduces this.
Chapter P12 SoundP12.01 all three
P12.02 the air in the hollow tube
P12.03 a 600 ms = 0.6 s b three-fifths
P12.04 They must be in a straight line so that the distance travelled in the time interval measured is equal to the separation of the microphones.
P12.05 Light travels faster than sound. For example, lightning is seen before thunder is heard.
P12.06 pitch gets higher
P12.07 loudness decreases
P12.08 a 20 Hz to 20 kHzb upper limit in particular decreases
P12.09 period T
P12.10 a A has the greater frequency.
b A will sound more high-pitched.
P12.11 Sound waves travel by the vibration of the particles of a material. There are no particles in a vacuum.
P12.12 (for example) shout from outside a closed window
P12.13 In a compression, the particles are closer together than before the wave is formed. In a rarefaction, the particles are further apart. See Figure P12.05 in the main text.
Chapter P13 LightP13.01 a
b This is so that it looks the right way round in a motorist’s rear-view mirror.
P13.02 a
incidence i reflection r
normal
mirror
incident ray reflected ray
angle of angle of
b angle of incidence = angle of reflection
P13.03 60°
P13.04 No light reaches the place at which the image appears to be formed.
P13.05
angle of refraction
angle of incidence
normal
incident ray
refracted ray
glassair
Answers to questions
20
P13.06 towards the normal
P13.07 a
b It is parallel to its initial direction.
P13.08 a angle of incidence = 0°b angle of refraction = 0°
P13.09 The angle of refraction is less than the angle of incidence.
P13.10 Rays of light are refracted as they pass through the raindrops.
P13.11 2.4
P13.12 a Light travels more slowly in material B, because the ray bends more on entering B.
b material B
P13.13 a glassb away from the normal
P13.14 1.58
P13.15 2.17 × 108 m/s
P13.16 25.4°
P13.17 total: 100% of the light is reflected internal: reflection happens inside the transparent material
P13.18 No, it will not be totally internally reflected because 45° is less than the critical angle.
P13.19 a c = 48.8°b See Figure P13.05c in the main text.
P13.20 n = 1.56
P13.21 TIR TIR
TIRTIR
P13.22 Light travelling along the glass will be absorbed by any impurities present.
P13.23
converging diverging
P13.24 parallel rays focus
P13.25 Reverse the arrow on the rays so that they spread out from the focus.
P13.26 It is the point at which rays travelling parallel to the axis of the lens are made to converge.
P13.27 Light rays pass through the point at which a real image is formed, and it can be formed on a screen. For a virtual image, the rays only appear to emerge from that point, and the image cannot be formed on a screen.
P13.28 The image arrow is below the axis.
P13.29 The rays from the image are dashed. They only appear to be diverging from that point.
P13.30 a See ray diagram below.
b 7.5 cm
FOFI
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Chapter P14 Properties of wavesP14.01 The first has distance on its horizontal axis, and
the second has time on its horizontal axis.
P14.02
amplitude
Distanceor TimeDi
spla
cem
ent
The diagram should show that amplitude is the height of a wave crest above the central (undisturbed) level.
P14.03 Measure across, say, 10 ripples and find the average separation by dividing by 10.
P14.04 1.5 cm (or 15 mm)
P14.05 a 100 Hz b 0.01 s
P14.06 The molecules vibrate up and down.
P14.07 longitudinal
P14.08 v = f l (speed v in m/s, frequency f in Hz, wavelength l in m)
P14.09 300 m/s
P14.10 wavelength 1 m has higher frequency
P14.11 frequency 90 MHz has longer wavelength
P14.12 a speed decreases
b wavelength decreases
c frequency is unchanged
P14.13
incidentwaves
barrier
reflectedwaves
P14.14 Change the depth of the water – shallower water gives slower ripple speed.
P14.15 Diffraction – ripples spread out into the space beyond the gap.
P14.16 For greatest diffraction effect, the width of the gap should be equal to the wavelength of the waves.
P14.17
Chapter P15 SpectraP15.01 yellow, blue
P15.02
violet
red orangeyellowgreenblueindigo
spectrum
prism
white light
P15.03 Some colours of light are more strongly refracted because their speed decreases more.
P15.04 a red light b violet light
P15.05 a infrared b red light
P15.06 a gamma rays
b radio waves
P15.07 a Both violet light and red light travel equally fast in empty space.
b Red light travels faster in glass.
P15.08 infrared radiation, microwaves
P15.09 Microwaves may transfer signals to and from satellite; radio waves are broadcast, and received by an aerial; remote control uses infrared.
Chapter P16 MagnetismP16.01 a SN
S N
Adjacent N and S poles attract one another with equal forces.
b NN
S S
The adjacent N poles and the adjacent S poles repel one another with equal forces.
Answers to questions
22
P16.02 a Soft magnetic materials are easier to magnetise and demagnetise. Hard magnetic materials are more difficult to magnetise and also more difficult to demagnetise.
b A permanent magnet made of steel will retain its magnetism for a longer time.
P16.03
N S NS
P16.04 Copper and iron are mixed together. Pass the electromagnet over the mixture of metal. Because copper is not magnetic, the electromagnet will attract only the iron, pulling it out of the mixture.
P16.05 a
current in
SN
current out
b When the current is reversed, the field is reversed, so the arrows on the field lines are reversed.
Chapter P17 Electric chargeP17.01 repel
P17.02 a positive (and equal in size to the negative charge on the rod)
b attract
P17.03 Individual hairs all have the same charge, so they repel. Hair and comb have opposite charges, so they attract.
P17.04
rod
positive chargesattracted to rod
negative chargesrepelled by rod
paper
P17.05 a negativeb repel
P17.06 The electric force causes the negative charges (electrons) to repel each other. As a result, some of them move through the wire to the other sphere, so that it gains a negative charge. (The charge on the first sphere decreases.)
P20.03 It would rotate in the opposite direction because its poles would be attracted the opposite way round.
P20.04 a If the current was not reversed, the coil would turn until its poles were facing their opposites and then stop turning.
b The commutator reverses the current.
P20.05 A greater current gives a greater turning effect.
P20.06 reverse the current; reverse the magnetic field
P20.07 force (motion) – thumb
magnetic field – first finger
current – second finger
P20.08 increase the current; increase the magnetic field strength
P20.09 zero force
Answers to questions
24
Chapter P21 Electromagnetic inductionP21.01 a
electricalenergy k.e.
heat
b
k.e. electricalenergy
heat
P21.02 The wire or magnet must move.P21.03 move the N pole out of the coil; move the S pole
towards the coilP21.04 Move the magnet faster; use a stronger magnet.P21.05 bigger coil; more turns; stronger magnetic field;
faster movementP21.06 so that less energy is lost during transmissionP21.07 primary coil; secondary coil; coreP21.08 step-upP21.09 step-downP21.10 2.5P21.11 100P21.12 a The core transfers the varying magnetic field
from the primary coil to the secondary.b Its magnetism must change rapidly.
P21.13 The magnetic field in the core does not change, so no e.m.f. will be induced in the secondary coil.
P21.14 current is lessP21.15 a 400 kV
b 250 A
c 1.5 MW
P21.16 a 157
b 1.53 A
c No power is lost in the transformer.
Chapter P22 Atomic physicsP22.01 a protons, neutrons
b electrons
P22.02 There is electrostatic attraction between opposite charges.
P22.03 a nucleon number = 17
b proton number = 8
P22.04 210
82Pb
P22.05 47 protons, 60 neutrons, 47 electrons
P22.06 1840 approximately
P22.07 a The number of protons is the same (and the number of electrons in a neutral atom).
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