Combined Science Paper 2 November 2019

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1. Athe air is warmed to body temperature while it is inside the air passages and lungs.
2. Bthe lungs squeeze the air during breathing out, and squeezing a gas raises its temperature.
3. Cair rubs against the walls of the windpipe as it moves, and this friction heats it up.
4. Dcarbon dioxide is a warm gas, so air rich in carbon dioxide is warmer than ordinary air.

1. Apulls water and the mineral salts dissolved in it up from the roots, and cools the leaves.
2. Bsupplies the leaf with the carbon dioxide it needs for photosynthesis during the daytime.
3. Cmakes the leaf cells lose water so that the stomata close and the plant saves more water.
4. Dadds water vapour to the air spaces of the leaf so that starch can be stored inside them.

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1. Aall the plants of one kind growing in one place, together with the soil they are rooted in.
2. Bthe set of physical conditions on their own, such as rainfall, temperature and wind, in one part of the world.
3. Can area of land that people plant and look after so that the crops and animals in it thrive.
4. Da community of living organisms and the non-living surroundings they interact with, not managed by people.

1. Acontains all the types of nutrient the body needs, in the right proportions for that person.
2. Bcontains a large amount of carbohydrate and fat, so that the body has spare energy at all hours.
3. Cis made up mainly of proteins, because proteins are needed for growth and for repair of tissues.
4. Dsupplies more energy each day than the body uses, so that the extra can be stored for later.

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1. AIt is a liquid at room temperature that does not dissolve in water and conducts electricity as it stands.
2. BIt is a soft solid that melts below one hundred degrees Celsius and does not dissolve in water at all.
3. CIt is a solid at room temperature, melts at a high temperature, and conducts electricity when molten or in solution.
4. DIt is a solid at room temperature with a low melting point, and it conducts electricity well while it is still solid.

1. Aa base, because a base reacts with the excess acid in the stomach and neutralises it.
2. Ban indicator, because it shows how much acid there is and stops more being formed.
3. Can acid, because a second acid added to the stomach cancels out the first one.
4. Da salt, because a salt dissolves in the stomach and washes the acid out of the body.

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1. Areacts with the limestone to form the slag that floats on top of the molten iron in the furnace.
2. Bcoats the iron formed so that it does not react with air and rust while inside the furnace.
3. Cmelts the iron ore so that liquid iron can run to the bottom of the furnace and be tapped off.
4. Dburns in the hot air blast to form carbon monoxide, which reduces iron(III) oxide to iron.

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1. AThe exhaust stroke, because the exhaust valve is open while the piston moves up.
2. BThe power stroke, because both valves are closed and the piston is being driven down.
3. CThe induction stroke, because the inlet valve is open while the piston moves down.
4. DThe compression stroke, because both valves are closed while the piston moves up.

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1. Acompress the mixture of air and petrol in the cylinder before the spark is produced.
2. Bproduce the spark that sets the mixture of air and petrol alight inside the cylinder.
3. Cpush the burnt gases out of the cylinder through the exhaust valve after burning.
4. Dspray petrol into the inlet manifold or the combustion chamber of the engine.

1. Adelivers the same measured amount of petrol to each cylinder, so the engine runs more efficiently.
2. Bworks without an electrical supply of its own, so the engine can be started even when the battery is flat.
3. Cburns the petrol inside itself, so less heat has to be carried away by the cooling system.
4. Dmixes the petrol with air before the mixture reaches any of the cylinders of the engine.

1. Aagainst the shaded wall of the house, where the panel is kept cool and does not crack in the heat.
2. Bon the ground beside the house, where the heat given off by the walls at night can reach it.
3. Con the roof top, where no trees or buildings shade it and it faces the sun for most of the day.
4. Dinside the ceiling space, where warm air trapped under the roof keeps the panel hot at night.

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1. Ais a good absorber of the radiant heat that falls on it from the sun.
2. Bcarries heat along the plate to the water faster than a light coloured surface.
3. Creflects radiant heat back on to the water pipes instead of taking any of it in.
4. Dkeeps the copper plate from rusting when it is left out in the sun and the rain.

1. Acopper conducts heat well and the thin walls let that heat pass quickly to the water.
2. Bcopper is a poor conductor, so the heat that reaches the water stays inside the tubing.
3. Cthin tubing holds a small volume of water, so the pump in the system has less work to do.
4. Dcopper reflects the sunlight falling on it, so the water inside is not overheated.

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1. Aholds a much larger volume of blood than the right ventricle holds at each single beat.
2. Bpumps blood a short distance to the lungs, where the thin capillaries could otherwise burst.
3. Creceives blood from the lungs, which arrives at a higher pressure than blood from the body.
4. Dpumps blood at a higher pressure, because that blood must travel all the way round the body.

1. ABouts of shivering and high fever with heavy sweating, headache, vomiting and aching muscles.
2. BA painless swelling of the glands of the neck, with a slow loss of weight over several months.
3. CYellow skin and eyes together with pale stools, coming on an hour or two after a fatty meal.
4. DAn itchy rash of small raised blisters that spreads from the chest to the face, arms and legs.

1. AVomiting and diarrhoea that go on for several days at a time.
2. BBleeding from the gums, the nose and other openings of the body.
3. CA high fever that keeps returning in bouts, with shivering and heavy sweating.
4. DA headache with aching muscles and painful joints all over the body.

1. Athicken the lining of the lungs, so that less of the dust in the air reaches the alveoli.
2. Bimprove the memory for a short while, but leave the person tired the next morning.
3. Craise the amount of oxygen carried in the blood, which then strains the heart and lungs.
4. Ddamage the brain, the liver and the heart, and lead the person into addiction.

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1. Agiving extra protein foods, such as beans and meat, so the bones grow longer and heavier.
2. Bkeeping the child out of the sunlight, because strong sunlight softens the bones of a growing child.
3. Cgiving foods rich in iron, such as liver and dark green vegetables, with every meal of the day.
4. Dgiving foods rich in calcium and vitamin D, such as milk, eggs and fish, and sunlight on the skin.

1. Atestis, urethra, sperm duct, epididymis.
2. Btestis, epididymis, urethra, sperm duct.
3. Ctestis, epididymis, sperm duct, urethra.
4. Dtestis, sperm duct, epididymis, urethra.

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1. Alowers the chance of an unwanted pregnancy and of passing on HIV.
2. Bclears up an infection of the reproductive tract in both partners within a few days.
3. Cprotects the sperm from the acid conditions of the vagina, so that fertility is raised.
4. Dincreases the number of sperm that reach the oviduct at each act of intercourse.

1. Athe repeated division of a zygote to form a hollow ball made of many smaller cells.
2. Bthe fusion of the nucleus of a male sex cell with that of a female sex cell to form a zygote.
3. Cthe release of a mature egg cell from one of the ovaries into the funnel of the oviduct each month.
4. Dthe attachment of a young embryo to the thickened lining of the wall of the uterus.

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1. Ait stops the moisture lining the alveolus from evaporating into the air passages.
2. Bit keeps the distance the gases have to diffuse very short, so they cross quickly.
3. Cit lets whole red blood cells pass into the air space and collect their oxygen there.
4. Dit allows the alveolus to store a large volume of air so that breathing can be slower.

1. AA dry lining that keeps water out of the air spaces so that oxygen dissolves faster.
2. BA thick muscular wall around each air sac that squeezes the air out during breathing out.
3. CMillions of tiny air sacs giving a very large total surface area, each with a moist lining.
4. DA ring of cartilage around each air sac that holds the sac open while air is flowing in.

1. Athe breakdown of the cell wall of a plant cell that has been left in dry soil for many days.
2. Bthe swelling of a plant cell as it takes in water by osmosis until its wall is stretched tight.
3. Cthe bursting of a cell that has taken in far more water than its membrane is able to hold.
4. Dthe shrinking of the protoplasm away from the cell wall as a plant cell loses water by osmosis.

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1. Aa particle made when atoms of two or more different elements join together chemically.
2. Bthe smallest part of a mixture that still keeps the properties of the substances in it.
3. Cthe smallest particle of an element that can take part in a chemical reaction.
4. Da charged particle formed when an element gains or loses one or more of its electrons.

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1. Aturn the oxygen in the air to a liquid first, so the nitrogen can be drawn off as a gas.
2. Bremove water vapour and carbon dioxide, which would freeze solid and block the pipes.
3. Ckill any bacteria carried in the air so that the nitrogen collected is pure enough to use.
4. Dslow the air down as it enters the plant so that the dust carried in it settles out.

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1. Ais less dense than the liquid oxygen, so it floats out of the top of the fractionating column itself.
2. Bdoes not dissolve in liquid oxygen, so it separates out from the mixture as a gas at once.
3. Chas a lower boiling point than oxygen, so it turns to gas while the oxygen is still liquid.
4. Dhas a higher boiling point than oxygen, so it needs less warming before it can escape.

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1. Araise the temperature of the water so that the two gases are given off more quickly.
2. Bkeep the two gases apart as they are formed at the two electrodes inside the cell.
3. Csupply the free ions that the water needs to carry the current between the electrodes.
4. Dstop the electrodes from being worn away by the gases that collect around them.

1. Aoxygen molecules are much heavier than hydrogen molecules, so they take up half the space.
2. Bhalf of the oxygen that is produced stays dissolved in the acidified water in the cell.
3. Coxygen is given off at both of the electrodes, so its volume is shared out between the two tubes.
4. Dwater holds two hydrogen atoms for every one oxygen atom, so the gases come off in that ratio.

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1. Ais so slow that very little sulphuric acid would be produced in the time available.
2. Bis violent and highly exothermic, and gives a mist of acid droplets that is hard to condense.
3. Ctakes in heat from the surroundings, so that the water would freeze around the sulphur trioxide.
4. Dgives off sulphur dioxide gas again, so all the sulphur trioxide made would be wasted.

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1. Athe two magnets are moved closer together, so that the field between them is stronger.
2. Bthe coil is turned in the magnetic field and cuts the field lines, inducing a current in it.
3. Cheat from the brushes passes into the slip rings, which drives a current round the coil.
4. Da current is passed through the coil, which then turns between the poles of the magnets.

1. Aonce every full turn of the coil, as the coil lies flat exactly midway between the two magnetic poles.
2. Beach time the rate at which the coil is being turned is increased or decreased.
3. Ceach time the magnets of the generator are replaced with a stronger pair of magnets.
4. Donce every half turn of the coil, as each side of the coil passes the opposite magnetic pole.

1. Afalls, because the stronger field opposes the turning of the coil much more strongly.
2. Brises, because the coil cuts more magnetic field lines in each second than before.
3. Cstays the same, because the output voltage depends on how fast the coil is turned.
4. Dfalls to zero, because the field lines are then too close together to cut the coil.

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1. Aa machine gives out more useful work than is put into it, and the extra escapes as heat and sound.
2. Bthe velocity ratio of a machine is fixed by its design and is greater than one.
3. Csome of the work put in goes to overcoming friction and to moving the parts of the machine.
4. Dthe load raised by the machine is heavier than the effort that is applied to it.

1. Aincreasing the load that is lifted, so that more useful work is done for the same effort.
2. Bmaking the moving parts heavier, so that they keep moving once they have started.
3. Coiling the moving parts, fitting ball bearings, and using lighter materials for those parts.
4. Dusing a longer effort arm, so that a smaller effort is needed to raise the same load.

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1. Acoal is burned in a furnace and the heat given out is changed straight into electricity by the boiler.
2. Bwater falling from a dam turns the turbines, which are joined to the shaft of a generator.
3. Csteam is passed over a permanent magnet, and the moving steam pushes a current along the cables.
4. Dcoal is burned to boil water, and the steam at high pressure turns turbines that drive a generator.

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1. Acan be burned in the boilers, but it wears away the blades of the turbines as it burns.
2. Bis non-renewable, and burning it pollutes the air and adds to global warming.
3. Cis renewable, but gives out far less heat for each kilogram burned than firewood does.
4. Dburns without giving off any waste gases, but leaves ash that is costly to bury safely.

1. Afalling water, while in a thermal station they are turned by steam at high pressure.
2. Bthe wind, while in a thermal station they are turned by the burning coal itself.
3. Cthe generator, while in a thermal station they are turned by the boiler of the plant.
4. Dsteam at high pressure, while in a thermal station they are turned by falling water.

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