Combined Science Paper 2 November 2025

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1. Agrind and crush food into small pieces before it is swallowed
2. Bcut and bite pieces from food at the moment it enters the mouth
3. Ctear and grip food that is being pulled away from a bone
4. Dhold food still against the roof of the mouth during chewing

1. Araises the temperature of the food so that it dissolves in the blood plasma
2. Bbreaks large insoluble food molecules into small soluble ones that can be absorbed
3. Ccuts the food into smaller lumps so that a greater surface of it is exposed to the saliva
4. Dpushes undigested food along the gut so that it can leave the body as faeces

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1. AIt keeps the air inside the alveolus warm so that oxygen dissolves in the blood.
2. BIt gives oxygen and carbon dioxide a very short distance to diffuse across.
3. CIt makes the alveolus strong enough to resist the blood pressure in the capillaries.
4. DIt allows the alveolus to stretch so that far more air is taken in at each breath.

1. AThe alveoli walls thicken and take in far more oxygen than the healthy walls did.
2. BThe alveoli are replaced by new air sacs that work better than the damaged ones.
3. CThe alveoli walls break down and the sacs join up, so the surface area for gaseous exchange falls.
4. DThe alveoli fill with mucus, which dissolves the oxygen and so carries gaseous exchange out faster.

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1. AIt is very reactive, because it has to lose eight electrons to empty its outer shell.
2. BIt is unreactive, because its outermost shell already holds a full set of electrons.
3. CIt is very reactive, because it gains two more electrons to complete its outer shell.
4. DIt reacts with cold water, forming an alkaline solution and releasing hydrogen gas.

1. Acarbon dioxide and water, together with heat energy given out to the surroundings
2. Bcarbon monoxide and water vapour, together with a large amount of black soot
3. Ccarbon dioxide and hydrogen gas, together with a small amount of black soot
4. Dcarbon monoxide and hydrogen, together with heat energy given out to the surroundings

1. ASelling paraffin stoves at the shopping centre, and repairing the chimneys at the clinic
2. BClosing the kitchen windows at night, and burning dry firewood rather than green firewood
3. CTesting each household for carbon monoxide, and treating those people found to be affected
4. DAwareness campaigns held at the local clinic, and posters displayed at the shopping centre

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1. Afewer trees means less shade over the ground, and this shade is what keeps the air cool
2. Bburning the felled trees uses up the oxygen that would otherwise cool the atmosphere
3. Cless carbon dioxide is taken in, so more of it builds up and traps heat in the atmosphere
4. Dbare soil sends sunlight straight back into space, and this reflected light warms the air

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1. Aholds the load steady on the vehicle, so the springs carry none of its weight
2. Blets the brakes and the tyres slow the vehicle down and bring it to a stop
3. Ccools the moving parts of the engine by carrying heat away from the cylinders
4. Dpushes the vehicle forward on its own, so the engine has to do no work at all

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1. AThey stay in fixed positions but each particle grows larger, so the block takes up more space.
2. BThey gain energy and move far apart from each other, travelling at random in all directions.
3. CThey gain energy, vibrate more and break out of their fixed positions to slide over one another.
4. DThey lose energy and settle into a fixed regular pattern in which they can do no more than vibrate.

1. Awater particles are further apart, so fewer of them are in the way of the sugar
2. Bsugar particles become smaller, so a greater mass of sugar fits between the water particles
3. Cwater can hold more dissolved sugar, so the spoonful takes up less space in the beaker
4. Dparticles gain kinetic energy, move faster and so mix among each other more quickly

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1. AAmylase acts on the protein and breaks it down into molecules of glucose.
2. BBile acts on the protein and breaks it down into maltose and amino acids.
3. CProtease acts on the protein and breaks it down into separate amino acids.
4. DLipase acts on the protein and breaks it down into fatty acids and glycerol.

1. Athe differences that exist between individual organisms of the same species
2. Bthe differences between one species of organism and a completely different species
3. Cthe change in an organism's body as it grows from a young form into an adult
4. Dthe passing on of features from parents to their offspring through their genes

1. Aa mutation, because the poor grass has brought about a change in the calf's genes
2. Ban inherited variation, because the two calves must have received different genes from their parents
3. Cenvironmental variation, because it was caused by the diet the smaller calf was given
4. Dnot variation at all, because the two calves share a breed and share their parents

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1. Akeep the oxygenated blood on the left of the heart apart from the deoxygenated blood
2. Bopen as the right ventricle contracts, so that blood can pass on into the aorta
3. Cpump blood out of the right ventricle and along the artery leading to the lungs
4. Dclose as the right ventricle contracts, stopping blood flowing back into the atrium

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1. Aroot hair cell pumps water inwards using the energy released by its own respiration
2. Bsoil water is a more dilute solution than the cell sap, so water crosses into the cell
3. Croots pull water in as they grow down through the spaces between the soil particles
4. Dcell sap is a more dilute solution than the soil water, so water crosses into the cell

1. Athe number of separate habitats that can be found in that area
2. Bthe variety of different living organisms found in that area
3. Cthe total number of individual animals living within that area
4. Dthe mass of plant material that the area produces in one year

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1. Aholds fewer organisms in total, so there is little competition for the food available
2. Bkeeps each population at the same size from one season to the next, whatever the weather brings
3. Ccontains species that each survive on their own without feeding on other species
4. Doffers a wide variety of food, so a species losing one food source can feed on another

1. AInfluenza, an infection of the airways caused by a virus spread in droplets of moisture
2. BKwashiorkor, in which the belly swells because the diet holds too little protein
3. CHaemophilia, an inherited condition in which the blood fails to clot properly
4. DMalaria, a disease caused by a parasite carried from person to person by mosquitoes

1. Aharden the bones and the teeth of the developing baby in the last months
2. Bbuild new muscle and other tissue as the developing baby grows in the uterus
3. Cprotect both the mother and the developing baby against infectious disease
4. Dmake the haemoglobin in the red blood cells of the mother and of the baby

1. Aform the bones and the teeth of the developing baby while it is in the uterus
2. Bbreak the proteins in the mother's diet down into the amino acids the baby uses
3. Ccarry oxygen from the mother's lungs to the tissues of the developing baby
4. Dsupply the energy the mother uses in carrying the extra mass of pregnancy

1. AIt is a toxic liquid with a valency of one that acts as an oxidising agent.
2. BIt is a soft metal that reacts with cold water and releases hydrogen gas from it.
3. CIt is a colourless solid with a valency of two in all of its compounds.
4. DIt is an odourless gas that acts as a reducing agent towards metal oxides.

1. ABromine is a colourless gas, while chlorine is a dense yellow solid.
2. BBromine is a shiny grey solid, while chlorine is a colourless liquid.
3. CBromine is a pale green gas, while chlorine is a reddish brown liquid.
4. DBromine is a reddish brown liquid, while chlorine is a pale green gas.

1. Athe oxygen that is compressed into cylinders for use in hospital wards
2. Bagricultural chemicals such as pesticides, and dyes for the textile industry
3. Cthe lime that farmers spread on their fields to reduce the acidity of the soil
4. Dthe graphite electrodes that carry the current into an industrial electrolysis cell

1. AThey dissolve in cold water without any change, giving a solution of the metal itself.
2. BThey gain electrons when they react, forming negatively charged ions in solution.
3. CThey are broken down into simpler substances when they are heated strongly in air.
4. DThey react with dilute acid, forming a salt of the metal and releasing hydrogen gas.

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1. AHeating the gate in air, and standing it on damp soil out of direct sunlight
2. BPainting the gate, and coating it with a thin layer of zinc by galvanising
3. CWiping the gate over with a wet cloth, and leaving it to dry in the open air
4. DRubbing the gate with sandpaper, and rinsing it with clean water after rain

1. AIt reacts with the iron to form a new metal that does not rust in damp air.
2. BIt forms a barrier that keeps air and moisture away from the iron underneath.
3. CIt warms the iron a little, so that any water landing on the gate dries at once.
4. DIt fills the gaps between the iron particles so that oxygen dissolves in the iron.

1. AA physical change can be reversed by physical means, while a chemical change forms a new substance.
2. BA physical change happens when a substance is heated, while a chemical change happens on cooling.
3. CA physical change splits a compound into its elements, while a chemical change mixes elements.
4. DIn a physical change a new substance is formed, while in a chemical change the original substance remains.

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1. AThe electrode connected to the positive terminal of the battery, where bromine is given off
2. BThe electrode connected to the negative terminal of the battery, where molten lead is deposited
3. CThe electrode that is made of carbon, whichever terminal of the battery it is joined to
4. DThe electrode that dips the deeper of the two into the molten lead(II) bromide

1. AColourless bubbles of hydrogen gas appear at one of the electrodes and bubbles of oxygen at the other.
2. BA pale green gas is given off at one electrode and a white solid forms at the other one.
3. CA silvery grey liquid metal collects at one electrode and reddish brown fumes rise at the other.
4. DA silvery grey metal collects at both electrodes and no gas at all is given off at either.

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1. ALeaving the geyser switched on all day, and fitting bulbs of a higher power rating
2. BRunning the stove and the heater together, and leaving the outside lights on at night
3. CFitting energy saving bulbs, and switching off appliances that are not being used
4. DCharging every appliance overnight, and leaving the refrigerator door open to cool

1. Agrinding maize by hand, heating water in a geyser and running a refrigerator
2. Blighting the rooms, heating water in a geyser and turning a bicycle wheel by pedal
3. Clighting the rooms, heating water in a geyser and running a refrigerator
4. Dlighting the rooms, burning charcoal in a brazier and drawing water from a well

1. Athe coil becomes a magnet whose own field drives a current round without any voltage
2. Ba current flows in the coil for as long as the magnet is held still inside it
3. Ca voltage is induced in the coil whenever the coil and the magnet move relative to each other
4. Dthe magnet loses some of its magnetism, and this lost magnetism appears as a current in the coil

1. AA current is passed into the coil, which then turns in the field and gives out a voltage.
2. BA coil is rotated in a magnetic field, cutting the lines of force, so a voltage is induced in it.
3. CA coil is held still inside a magnetic field, and the voltage is drawn out of the fixed magnet itself.
4. DA chemical reaction inside the coil pushes electrons around the circuit in one direction.

1. AUsing a weaker magnet, and rotating the coil more slowly than before
2. BUsing thicker wire in the coil, and holding the coil still within the field
3. CUsing a stronger magnet, and winding more turns of wire onto the coil
4. DUsing a coil of smaller area, and turning the coil in the opposite direction

1. AThe black can, because a dull black surface absorbs radiation better than a white one
2. BThe white can, because a white surface lets radiation pass straight through to the water
3. CBoth heat at the same rate, because the colour of a surface makes no difference to this
4. DThe white can, because a white surface reflects the radiation onto the water inside it

1. AThe white can, because a white surface loses heat by radiation more readily than black
2. BBoth cool at the same rate, because the water in each can started at one temperature
3. CThe black can, because black paint conducts heat away from the water faster than white
4. DThe black can, because a dull black surface emits radiation better than a white one

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1. AThe friction at the pulley axles, and the weight of the moving pulley blocks
2. BThe length of rope wound onto the drum, and the direction of the effort applied
3. CThe thickness of the rope used, and the time taken to raise the load into place
4. DThe height through which the load is raised, and the mass of the load itself

1. Acools the cylinder block by circulating water around it for as long as the engine is running
2. Bsets the mixture alight at the top of the compression stroke by making a spark
3. Cremoves the burnt gases from the cylinder and passes them into the exhaust pipe
4. Dmixes petrol with air in the right proportion before the mixture enters the cylinder

1. Alet too much fuel into the mixture, so the fuel burns incompletely in the cylinder
2. Blet too much air into the mixture, so the engine runs cooler than it was designed to
3. Cstop the exhaust gases leaving the cylinder, so fresh mixture cannot be drawn in
4. Dweaken the spark at the plug, so the mixture in the cylinder is not set alight at all

1. Alets too little air into the mixture, so the fuel burns incompletely in the cylinder
2. Blets too much air into the mixture, so the fuel burns before it has been fully compressed
3. Cholds the exhaust gases in the cylinder at the end of the power stroke
4. Dcuts the fuel supply off, so the engine stalls as soon as the driver accelerates

1. AA diesel engine is lighter than a petrol engine of the same power and wears out sooner.
2. BA petrol engine turns more of the energy in its fuel into useful work than a diesel does.
3. CA diesel engine uses a fuel injector, while a petrol engine uses a spark plug to fire its fuel.
4. DA diesel engine uses a spark plug, while a petrol engine uses a fuel injector to fire its fuel.

1. Athe engine uses less fuel for each kilometre travelled than any single cylinder engine
2. Beach cylinder burns a different fuel, so the engine runs on whichever of them is the cheapest
3. Cthe engine starts without a battery, since one cylinder sets the next cylinder going
4. Dthe power strokes follow one another, so the engine turns and the vehicle moves smoothly

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