Combined Science Paper 2 June 2023

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1. ABy active transport from cell to cell, using energy from respiration to pump the water towards the xylem.
2. BBy diffusion of water through the cell walls, from a region of low water potential to one of high water potential.
3. CBy transpiration pull acting directly on the cortex cells, whose fully permeable walls let the water through.
4. DBy osmosis from cell to cell, passing from cells of higher water potential to cells of lower water potential.

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1. AIt carries oxygen from the lungs to the tissues, held inside its haemoglobin molecules.
2. BIt engulfs and digests bacteria that get into the body through a cut in the skin.
3. CIt forms a clot at a wound by sticking together where the blood vessel is damaged.
4. DIt transports dissolved food, hormones, carbon dioxide and urea around the body.

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1. AThe limewater is bleached to colourless and a sharp choking smell is given off.
2. BThe limewater turns milky as a white precipitate of calcium carbonate forms.
3. CThe limewater stays clear but bubbles off a gas that relights a glowing splint.
4. DThe limewater turns from colourless to a bright yellow within a few seconds.

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1. AA large surface area with a moist lining, and a wall that is one cell thick.
2. BA thick muscular wall and rings of cartilage that hold the air space open.
3. CA dry lining and a thick layer of connective tissue around each air sac.
4. DA ciliated lining and mucus glands that trap dust before it reaches the blood.

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Answer this when you sit the paper.

Answer this when you sit the paper.

1. AIt conducts electricity well as a solid but stops conducting when molten.
2. BIt has a low melting point and boils below one hundred degrees Celsius, as water does.
3. CIt is a hard crystalline solid at room temperature with a high melting point.
4. DIt is a gas at room temperature that dissolves in organic solvents such as petrol.

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Answer this when you sit the paper.

Answer this when you sit the paper.

Answer this when you sit the paper.

Answer this when you sit the paper.

Answer this when you sit the paper.

Answer this when you sit the paper.

Answer this when you sit the paper.

Answer this when you sit the paper.

Answer this when you sit the paper.

Answer this when you sit the paper.

1. ARubbing created fresh charge on the surface of the balloon, and an equal fresh charge on the wool.
2. BThe balloon gained protons from the wool, and the wool was left short of protons.
3. CThe wool gained electrons from the balloon, so the wool ended up negatively charged.
4. DThe balloon gained electrons from the wool, and the wool was left with fewer electrons.

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Answer this when you sit the paper.

Answer this when you sit the paper.

1. AThe load moves through a much shorter distance than the effort does in a system like this one.
2. BSome of the work done by the effort goes against friction and lifts the moving parts.
3. CThe velocity ratio of the system falls as soon as a heavier load is hung on it.
4. DEnergy is destroyed in the ropes while the effort is applied over a long period.

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Answer this when you sit the paper.

1. AIt kills the bacteria in the food and softens it so that it is easier to swallow.
2. BIt makes the food strongly acidic so that the enzymes of the intestine can work.
3. CIt digests the fats in the food into fatty acids and glycerol, using the lipase enzyme it contains.
4. DIt neutralises the acid brought from the stomach and emulsifies fats into droplets.

1. AIt contains bile salts, which break large fat droplets down into much smaller ones.
2. BIt contains hydrochloric acid, which gives the enzymes of the gut the low pH they need.
3. CIt absorbs the digested food from the gut and carries it away to the liver in the blood.
4. DIt is alkaline and contains enzymes that digest starch, protein and fat in the duodenum.

1. AIt hardens the enamel, so that teeth already lost can grow back in their place.
2. BIt replaces the enamel that acid from the bacteria in the mouth has dissolved.
3. CIt prevents tooth decay and gum disease, and it keeps the breath fresh.
4. DIt raises the amount of saliva made, so that food is fully digested in the mouth.

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1. AA disease that appears in a person who has been given the wrong medicine.
2. BA disease that is inherited from a parent and shows itself later in life.
3. CA disease that is passed from one person to another by direct physical contact.
4. DA disease that takes hold easily in a person whose immune system is weakened.

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1. AThe virus is carried in the air the mother breathes out and into the womb.
2. BThe virus crosses the placenta from the mother's blood into the blood of the foetus.
3. CThe virus is already present inside the ovum before it is fertilised by a sperm cell.
4. DThe virus passes through the mother's skin and into the wall of the uterus.

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1. ABy giving the mother a course of antibiotics in the last month of the pregnancy.
2. BBy boiling the mother's breast milk for several minutes before it is given to the baby to drink.
3. CBy the mother taking antiretroviral medicines and the baby being treated after birth.
4. DBy delaying the birth for as long as possible, so that the virus grows weaker.

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1. AOestrogen repairs and thickens the uterus lining, and progesterone maintains that lining.
2. BOestrogen breaks down the uterus lining, and progesterone releases the mature ovum.
3. COestrogen makes the sperm cells swim faster, and progesterone thins the uterus lining.
4. DOestrogen brings on menstruation each month, and progesterone stops the ovary from making ova.

1. AIt stays in the oviduct and grows there into an embryo attached to the oviduct wall.
2. BIt divides repeatedly by mitosis and travels down to the uterus, where it implants.
3. CIt divides by meiosis to halve its chromosome number before it reaches the uterus.
4. DIt passes back into the ovary, where the corpus luteum encloses it and feeds it.

1. AThe uterus lining is shed much more slowly, so no blood leaves through the vagina.
2. BProgesterone keeps the thickened uterus lining in place for the implanted embryo.
3. CThe placenta blocks the cervix, so the lining that is shed cannot leave the body.
4. DThe ovaries shut down completely, so no hormone at all reaches the uterus lining.

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1. AIt is compressed and cooled, then allowed to expand, over and over, until about -200 degrees Celsius.
2. BIt is passed through a bed of charcoal, which holds the gases as a liquid in its pores.
3. CIt is dissolved in water under very high pressure, and the cold water is then drawn off as liquid air.
4. DIt is heated under pressure until the gases in it join up and settle out as a liquid.

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1. AOxygen is used to make ammonia fertiliser, and nitrogen is used in steel making furnaces.
2. BOxygen is used in hospitals to help patients breathe, and nitrogen is used to make ammonia.
3. COxygen is used to fill balloons so that they float, and nitrogen is used to bleach paper.
4. DOxygen is used to put out fires in burning buildings, and nitrogen is burnt as a fuel in rockets.

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1. AA is propene and B is propane.
2. BA is propane and B is propene.
3. CA is ethane and B is ethene.
4. DA is butane and B is butene.

1. APropane has only single bonds between its carbon atoms, while propene has a double bond.
2. BPropane has a double bond between two of its carbon atoms, while propene has single bonds.
3. CPropane has four carbon atoms joined in a ring, while propene has a chain of three atoms.
4. DPropane is unsaturated and decolourises bromine water, while propene is saturated.

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Answer this when you sit the paper.

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1. ABy conduction through the air to the pot, and by convection through the metal of the pot.
2. BBy radiation through the metal of the pot, and by evaporation of the water in the pot.
3. CBy radiation from the surface to the pot, and by conduction through the pot to the water.
4. DBy convection from the surface to the pot, and by radiation through the metal of the pot.

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1. AIt is shiny and smooth, so that the heat from the sun is reflected off it.
2. BIt is clear and transparent, so that the sun's rays pass straight through it.
3. CIt is dull and black, so that it takes in as much of the sun's heat as it can.
4. DIt is rough and painted white, so that the heat is spread evenly over the pot.

1. AThe surface turns the sun's light into electricity, which then warms a coil in the pot.
2. BThe glass cover traps cold air beneath it, and that air then warms the pot by convection.
3. CThe curved shiny surface reflects the sun's heat to a focal point where the pot sits.
4. DThe dark surface takes in the sun's heat and stores it until the food is placed on it.

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1. AThe exhaust stroke, because the piston is moving up while the exhaust valve is open.
2. BThe compression stroke, because the piston is moving up while both valves are closed.
3. CThe power stroke, because the piston is moving down while both of the valves are shut.
4. DThe intake stroke, because the piston is moving down while the inlet valve is open.

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1. AIt uses its fuel more efficiently, but it is harder to start in cold weather.
2. BIt uses its fuel more efficiently, but it cannot be fitted to a heavy vehicle.
3. CIt is quieter and lighter to carry, but it burns much more fuel for a given journey.
4. DIt is cheaper to buy than a petrol engine, but its plugs have to be changed often.

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1. AThe piston in the master cylinder presses the brake fluid, which passes the pressure to the wheel pistons.
2. BThe pedal pulls a steel cable, which tightens a metal band around the rim of each of the four wheels.
3. CThe pedal opens a valve that lets compressed air escape, and the falling air pressure stops the wheels turning.
4. DThe pedal closes an electrical switch, and the current sent to the magnets at each wheel slows the car.

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Answer this when you sit the paper.

Answer this when you sit the paper.

Answer this when you sit the paper.

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1. AIt stays the same, because the weight of the block itself has not been changed.
2. BIt falls, because the block is now supported over a shorter length of ground.
3. CIt rises, because the same weight now presses on a smaller area of contact.
4. DIt falls to zero, because the block then rests on its edges instead of on a flat face.