▶️ Answer/Explanation
Oxygen is a waste product of photosynthesis in the plant’s metabolism.
Its removal from the body through the stomata fits the definition of excretion.
This is not respiration (chemical breakdown of nutrients for energy) or movement.
✅ Answer: (A)
Its removal from the body through the stomata fits the definition of excretion.
This is not respiration (chemical breakdown of nutrients for energy) or movement.
✅ Answer: (A)
▶️ Answer/Explanation
Cell membranes are present in both animal and plant cells, so A and B are incorrect.
Cell walls are a structural feature unique to plant cells (and not present in animal cells).
This rules out C and confirms D as the correct statement.
✅ Answer: (D)
Cell walls are a structural feature unique to plant cells (and not present in animal cells).
This rules out C and confirms D as the correct statement.
✅ Answer: (D)
▶️ Answer/Explanation
Glycogen is a storage polysaccharide built from many glucose molecules joined together.
Fats are made from fatty acids and glycerol, not amino acids, so A is wrong.
Starch is made from glucose (not fatty acid), and protein is made from amino acids (not glycerol), so C and D are wrong.
✅ Answer: (B)
Fats are made from fatty acids and glycerol, not amino acids, so A is wrong.
Starch is made from glucose (not fatty acid), and protein is made from amino acids (not glycerol), so C and D are wrong.
✅ Answer: (B)
▶️ Answer/Explanation
The greatest frequency of effective collisions occurs at the enzyme’s optimum temperature, where kinetic energy and shape/fit of the active site are ideal.
This corresponds to the shortest digestion time on the graph, since the reaction proceeds fastest at that point.
Beyond this temperature, the enzyme begins to denature and collisions become less effective.
✅ Answer: (C)
This corresponds to the shortest digestion time on the graph, since the reaction proceeds fastest at that point.
Beyond this temperature, the enzyme begins to denature and collisions become less effective.
✅ Answer: (C)
▶️ Answer/Explanation
As light intensity increases from zero, the rate of photosynthesis rises steadily because light is the limiting factor.
At higher light intensities, another factor (such as \(CO_2\) concentration or temperature) becomes limiting, so the rate levels off into a plateau.
The correct graph starts at the origin, rises, then flattens out at a maximum rate.
✅ Answer: (D)
At higher light intensities, another factor (such as \(CO_2\) concentration or temperature) becomes limiting, so the rate levels off into a plateau.
The correct graph starts at the origin, rises, then flattens out at a maximum rate.
✅ Answer: (D)
▶️ Answer/Explanation
In the diagram, R represents the pancreas, which produces digestive enzymes.
S represents the large intestine (colon), which absorbs water from undigested food.
P represents the gall bladder, which stores bile produced by the liver.
✅ Answer: (C)
S represents the large intestine (colon), which absorbs water from undigested food.
P represents the gall bladder, which stores bile produced by the liver.
✅ Answer: (C)
▶️ Answer/Explanation
The student stops exercising at \(t = 6\) minutes, where the heart rate is 100 beats per minute.
The heart rate falls back to the resting rate of 60 beats per minute at \(t = 9\) minutes.
So the time taken to return to resting rate is \(9 – 6 = 3\) minutes.
✅ Answer: (A)
The heart rate falls back to the resting rate of 60 beats per minute at \(t = 9\) minutes.
So the time taken to return to resting rate is \(9 – 6 = 3\) minutes.
✅ Answer: (A)
▶️ Answer/Explanation
During extreme exercise, glucose is used up rapidly by respiring muscle cells, so its concentration is low.
Oxygen supply cannot keep pace with demand, so muscles switch to anaerobic respiration, meaning oxygen concentration is also low.
Anaerobic respiration produces lactic acid as a by-product, which builds up to a high concentration.
✅ Answer: (C)
Oxygen supply cannot keep pace with demand, so muscles switch to anaerobic respiration, meaning oxygen concentration is also low.
Anaerobic respiration produces lactic acid as a by-product, which builds up to a high concentration.
✅ Answer: (C)
▶️ Answer/Explanation
Vasodilation widens skin arterioles, bringing more blood to the surface where heat can be lost, warming or cooling depending on the accompanying process.
Sweating cools the body because heat is used to evaporate sweat from the skin surface.
Vasodilation combined with sweating therefore both act together to cool the body down, matching option D.
✅ Answer: (D)
Sweating cools the body because heat is used to evaporate sweat from the skin surface.
Vasodilation combined with sweating therefore both act together to cool the body down, matching option D.
✅ Answer: (D)
▶️ Answer/Explanation
The polyp produces genetically identical polyps by mitosis (budding), which is asexual reproduction, so statement 1 is correct.
The medusa stage produces egg and sperm which fuse at fertilisation, which is sexual reproduction, so statement 2 is correct.
Gametes are haploid (from meiosis) and their fusion produces a diploid zygote, so statement 3 is also correct.
✅ Answer: (D)
The medusa stage produces egg and sperm which fuse at fertilisation, which is sexual reproduction, so statement 2 is correct.
Gametes are haploid (from meiosis) and their fusion produces a diploid zygote, so statement 3 is also correct.
✅ Answer: (D)
▶️ Answer/Explanation
Human body cells are diploid, containing 46 chromosomes (23 pairs), while gametes are haploid, containing 23 chromosomes (a single set).
Only diagram B correctly matches “diploid” with body cells at 46 chromosomes and “haploid” with gametes at 23 chromosomes.
The other diagrams either mislabel which cell type is haploid/diploid or attach the wrong chromosome numbers to each.
✅ Answer: (B)
Only diagram B correctly matches “diploid” with body cells at 46 chromosomes and “haploid” with gametes at 23 chromosomes.
The other diagrams either mislabel which cell type is haploid/diploid or attach the wrong chromosome numbers to each.
✅ Answer: (B)
▶️ Answer/Explanation
Carnivores, herbivores and producers each feed at, or occupy, only one specific trophic level in a food chain.
Decomposers break down dead or waste organic material from producers, primary consumers, secondary consumers and any other trophic level.
This means decomposers obtain energy directly from every trophic level, not just one.
✅ Answer: (B)
Decomposers break down dead or waste organic material from producers, primary consumers, secondary consumers and any other trophic level.
This means decomposers obtain energy directly from every trophic level, not just one.
✅ Answer: (B)
▶️ Answer/Explanation
Fewer trees means less photosynthesis occurring overall, so less carbon dioxide is removed from the atmosphere and less oxygen is released.
Cleared vegetation is often burned, which directly adds more \(CO_2\) to the atmosphere through combustion.
Together, these effects cause carbon dioxide levels to rise and oxygen levels to fall.
✅ Answer: (A)
Cleared vegetation is often burned, which directly adds more \(CO_2\) to the atmosphere through combustion.
Together, these effects cause carbon dioxide levels to rise and oxygen levels to fall.
✅ Answer: (A)
▶️ Answer/Explanation
To ensure all the acid reacts and none remains in the final product, an excess of the insoluble solid reactant is used.
Calcium carbonate is insoluble, so excess unreacted solid can simply be filtered off, leaving pure calcium chloride solution.
Crystallisation of the filtrate then yields pure solid calcium chloride: \(CaCO_3 + 2HCl \rightarrow CaCl_2 + H_2O + CO_2\).
✅ Answer: (B)
Calcium carbonate is insoluble, so excess unreacted solid can simply be filtered off, leaving pure calcium chloride solution.
Crystallisation of the filtrate then yields pure solid calcium chloride: \(CaCO_3 + 2HCl \rightarrow CaCl_2 + H_2O + CO_2\).
✅ Answer: (B)
▶️ Answer/Explanation
Boiling, dissolving and melting are physical changes because no new substance is formed and the change is generally reversible.
Neutralisation involves an acid reacting with a base to form new substances: a salt and water.
Since new chemical substances are produced, this is a chemical change.
✅ Answer: (D)
Neutralisation involves an acid reacting with a base to form new substances: a salt and water.
Since new chemical substances are produced, this is a chemical change.
✅ Answer: (D)
▶️ Answer/Explanation
From \(Na_3PO_4\), the phosphate ion must have a charge of \(3-\), giving \(PO_4^{3-}\).
From \(Al_2(SO_4)_3\), balancing charges shows the aluminium ion is \(Al^{3+}\).
Combining \(Al^{3+}\) with \(PO_4^{3-}\) requires a 1:1 ratio, since the charges already balance, giving \(AlPO_4\).
✅ Answer: (A)
From \(Al_2(SO_4)_3\), balancing charges shows the aluminium ion is \(Al^{3+}\).
Combining \(Al^{3+}\) with \(PO_4^{3-}\) requires a 1:1 ratio, since the charges already balance, giving \(AlPO_4\).
✅ Answer: (A)
▶️ Answer/Explanation
With inert carbon electrodes, copper(II) ions are discharged at the cathode, depositing an orange-brown solid layer of copper metal.
At the anode, hydroxide ions from water are discharged in preference to sulfate ions, producing bubbles of oxygen gas.
Since carbon electrodes don’t dissolve, there’s no “anode decreases in size” observation, ruling out A and D.
✅ Answer: (C)
At the anode, hydroxide ions from water are discharged in preference to sulfate ions, producing bubbles of oxygen gas.
Since carbon electrodes don’t dissolve, there’s no “anode decreases in size” observation, ruling out A and D.
✅ Answer: (C)
▶️ Answer/Explanation
Magnesium loses electrons to form \(Mg^{2+}\), meaning it is oxidised, so A is incorrect and the reaction does involve both oxidation and reduction, ruling out C.
Chlorine gains electrons to form \(Cl^-\), meaning it is reduced; the substance that is reduced acts as the oxidising agent.
Oxidation and reduction can occur without oxygen, as it is really about electron transfer, so D is incorrect.
✅ Answer: (B)
Chlorine gains electrons to form \(Cl^-\), meaning it is reduced; the substance that is reduced acts as the oxidising agent.
Oxidation and reduction can occur without oxygen, as it is really about electron transfer, so D is incorrect.
✅ Answer: (B)
▶️ Answer/Explanation
Chlorine gas dissolves in the moisture on damp litmus paper and acts as a bleaching agent.
This bleaching action turns the damp red litmus white, rather than simply changing its colour due to acidity.
\(CO_2\) and \(SO_2\) are acidic gases but only turn blue litmus red, not red litmus, and \(H_2\) has no effect on litmus.
✅ Answer: (B)
This bleaching action turns the damp red litmus white, rather than simply changing its colour due to acidity.
\(CO_2\) and \(SO_2\) are acidic gases but only turn blue litmus red, not red litmus, and \(H_2\) has no effect on litmus.
✅ Answer: (B)
▶️ Answer/Explanation
An inert atmosphere is needed during welding to stop the hot metal reacting with gases in the air, such as oxygen.
Argon is a noble gas with a full outer electron shell, making it very unreactive and safe to surround the weld.
Carbon dioxide, fluorine and oxygen can all react chemically at high temperatures, so they are unsuitable.
✅ Answer: (A)
Argon is a noble gas with a full outer electron shell, making it very unreactive and safe to surround the weld.
Carbon dioxide, fluorine and oxygen can all react chemically at high temperatures, so they are unsuitable.
✅ Answer: (A)
▶️ Answer/Explanation
Metals are generally malleable and good thermal conductors, so rows A and B are correctly linked.
Non-metals generally have low melting points (compared with metals) and are typically poor electrical conductors, since they lack the delocalised electrons found in metals.
Row C wrongly links non-metals with being electrical conductors, so this is the row that does not correctly match.
✅ Answer: (C)
Non-metals generally have low melting points (compared with metals) and are typically poor electrical conductors, since they lack the delocalised electrons found in metals.
Row C wrongly links non-metals with being electrical conductors, so this is the row that does not correctly match.
✅ Answer: (C)
▶️ Answer/Explanation
A more reactive metal can displace and reduce the oxide of a less reactive metal.
Magnesium is more reactive than copper, so it can remove oxygen from copper oxide, reducing it to copper metal.
Calcium and sodium are both more reactive than magnesium, and magnesium oxide is already the oxide of magnesium itself, so these cannot be reduced by magnesium.
✅ Answer: (B)
Magnesium is more reactive than copper, so it can remove oxygen from copper oxide, reducing it to copper metal.
Calcium and sodium are both more reactive than magnesium, and magnesium oxide is already the oxide of magnesium itself, so these cannot be reduced by magnesium.
✅ Answer: (B)
▶️ Answer/Explanation
Zinc is more reactive than iron, not the other way round, so statement 1 is incorrect.
Because zinc is more reactive, it oxidises in preference to iron, protecting the iron underneath — this is sacrificial protection, so statements 2 and 4 are correct.
As long as any zinc coating remains nearby, it continues to protect the iron even if scratched, so statement 3 is incorrect.
✅ Answer: (C)
Because zinc is more reactive, it oxidises in preference to iron, protecting the iron underneath — this is sacrificial protection, so statements 2 and 4 are correct.
As long as any zinc coating remains nearby, it continues to protect the iron even if scratched, so statement 3 is incorrect.
✅ Answer: (C)
▶️ Answer/Explanation
In the Contact process, sulfur dioxide (not sulfur itself) is burned/formed and then catalytically oxidised to sulfur trioxide, so burning solid sulfur directly to \(SO_3\) as shown in A is not a genuine step.
\(2SO_2 + O_2 \rightleftharpoons 2SO_3\) is the key catalytic step of the process, so B does occur.
\(SO_3\) is dissolved in concentrated sulfuric acid to form oleum (\(H_2S_2O_7\)), which is then diluted with water to form sulfuric acid, so C and D both occur.
✅ Answer: (A)
\(2SO_2 + O_2 \rightleftharpoons 2SO_3\) is the key catalytic step of the process, so B does occur.
\(SO_3\) is dissolved in concentrated sulfuric acid to form oleum (\(H_2S_2O_7\)), which is then diluted with water to form sulfuric acid, so C and D both occur.
✅ Answer: (A)
▶️ Answer/Explanation
Limestone is calcium carbonate, which acts as a base and can neutralise excess acidity in soil.
Neutralising acid raises the soil’s pH, making it less acidic and more suitable for crop growth.
Limestone does not supply nitrogen and is not itself classed as a fertiliser, so A, B and C are incorrect.
✅ Answer: (D)
Neutralising acid raises the soil’s pH, making it less acidic and more suitable for crop growth.
Limestone does not supply nitrogen and is not itself classed as a fertiliser, so A, B and C are incorrect.
✅ Answer: (D)
▶️ Answer/Explanation
The bottom fraction contains the largest hydrocarbon molecules, which have the strongest intermolecular forces, so statements 1 and 2 are incorrect.
Larger molecules make the fraction thick and syrupy (most viscous), and their strong intermolecular forces mean they need more energy to vaporise, making them harder to ignite (least flammable).
This means statements 3 and 4 correctly describe the bottom fraction.
✅ Answer: (D)
Larger molecules make the fraction thick and syrupy (most viscous), and their strong intermolecular forces mean they need more energy to vaporise, making them harder to ignite (least flammable).
This means statements 3 and 4 correctly describe the bottom fraction.
✅ Answer: (D)
▶️ Answer/Explanation
In addition polymerisation, the \(C{=}C\) double bond in the monomer opens up and forms a single bond linking each monomer unit into a long chain.
All the atoms and side groups attached to the monomer’s carbons are carried over unchanged into the repeat unit of the polymer.
The correct structure repeats this exact monomer unit joined end-to-end by single carbon–carbon bonds, with no atoms gained or lost.
✅ Answer: (C)
All the atoms and side groups attached to the monomer’s carbons are carried over unchanged into the repeat unit of the polymer.
The correct structure repeats this exact monomer unit joined end-to-end by single carbon–carbon bonds, with no atoms gained or lost.
✅ Answer: (C)
▶️ Answer/Explanation
On a speed–time graph, constant speed means the speed value does not change over time.
This is represented by a flat, horizontal line, since the gradient (which represents acceleration) is zero.
Any line that slopes upward or downward shows the speed changing, meaning the object is accelerating or decelerating instead.
✅ Answer: (C)
This is represented by a flat, horizontal line, since the gradient (which represents acceleration) is zero.
Any line that slopes upward or downward shows the speed changing, meaning the object is accelerating or decelerating instead.
✅ Answer: (C)
▶️ Answer/Explanation
Constant speed means there is no acceleration, so by Newton’s first law the forces acting on the parachutist must be balanced.
The parachutist’s weight acting downwards is exactly balanced by air resistance (drag) acting upwards.
Since these forces cancel out, the resultant (net) force on the parachutist is zero.
✅ Answer: (D)
The parachutist’s weight acting downwards is exactly balanced by air resistance (drag) acting upwards.
Since these forces cancel out, the resultant (net) force on the parachutist is zero.
✅ Answer: (D)
▶️ Answer/Explanation
Kinetic energy is given by \( E_k = \frac{1}{2}mv^2 \), so kinetic energy is proportional to the square of the speed.
If kinetic energy increases by a factor of 4, then \(v^2\) must also increase by a factor of 4, since mass stays constant.
Taking the square root of 4 gives a speed increase factor of 2, so the new speed is \(2.0v\).
✅ Answer: (B)
If kinetic energy increases by a factor of 4, then \(v^2\) must also increase by a factor of 4, since mass stays constant.
Taking the square root of 4 gives a speed increase factor of 2, so the new speed is \(2.0v\).
✅ Answer: (B)
▶️ Answer/Explanation
The Sun’s energy comes from small nuclei, mainly hydrogen, joining together to form larger nuclei such as helium.
This joining process is called nuclear fusion, and it releases huge amounts of energy.
Nuclear fission is the splitting of large nuclei (used in nuclear power stations), which is a different process from what powers the Sun.
✅ Answer: (D)
This joining process is called nuclear fusion, and it releases huge amounts of energy.
Nuclear fission is the splitting of large nuclei (used in nuclear power stations), which is a different process from what powers the Sun.
✅ Answer: (D)
▶️ Answer/Explanation
During melting, energy supplied is used to break the bonds/forces holding particles in a fixed lattice, not to increase particle kinetic energy.
Similarly, during boiling, energy input overcomes intermolecular forces to separate particles into a gas, rather than raising temperature.
In both cases, temperature stays constant (at the melting point or boiling point) throughout the change of state.
✅ Answer: (D)
Similarly, during boiling, energy input overcomes intermolecular forces to separate particles into a gas, rather than raising temperature.
In both cases, temperature stays constant (at the melting point or boiling point) throughout the change of state.
✅ Answer: (D)
▶️ Answer/Explanation
The wave speed equation is \( v = f\lambda \), which rearranges to \( \lambda = \frac{v}{f} \).
Substituting the values gives \( \lambda = \frac{330}{3300} \).
This works out to \( \lambda = 0.10 \) m.
✅ Answer: (A)
Substituting the values gives \( \lambda = \frac{330}{3300} \).
This works out to \( \lambda = 0.10 \) m.
✅ Answer: (A)
▶️ Answer/Explanation
Only a converging lens can produce a magnified, upright image suitable for use as a magnifying glass, so statement 1 is correct.
For a converging lens to magnify in this way, the object must be placed closer to the lens than its focal length, so statement 2 is correct.
This arrangement always produces a virtual image, which is why the image appears larger but cannot be projected onto a screen, so statement 3 is correct.
✅ Answer: (D)
For a converging lens to magnify in this way, the object must be placed closer to the lens than its focal length, so statement 2 is correct.
This arrangement always produces a virtual image, which is why the image appears larger but cannot be projected onto a screen, so statement 3 is correct.
✅ Answer: (D)
▶️ Answer/Explanation
When an unmagnetised iron bar is brought near a magnet, it becomes magnetised by induction, with the nearer end always taking the opposite polarity to the pole facing it.
Since the magnet’s South pole faces end Y, end Y is induced to become a North pole, so that it is attracted to the magnet.
The opposite end, X, is then induced to become a South pole.
✅ Answer: (C)
Since the magnet’s South pole faces end Y, end Y is induced to become a North pole, so that it is attracted to the magnet.
The opposite end, X, is then induced to become a South pole.
✅ Answer: (C)
▶️ Answer/Explanation
First find the current using \( I = \frac{V}{R} = \frac{6.0}{30} = 0.2 \) A.
Charge is found using \( Q = It \), where \(t\) is the time in seconds.
Substituting gives \( Q = 0.2 \times 5.0 = 1.0 \) C.
✅ Answer: (A)
Charge is found using \( Q = It \), where \(t\) is the time in seconds.
Substituting gives \( Q = 0.2 \times 5.0 = 1.0 \) C.
✅ Answer: (A)
▶️ Answer/Explanation
House lighting circuits connect lamps in parallel, so each lamp receives the full supply voltage and works independently of the others.
This means each lamp can have its own switch, allowing it to be turned on or off separately without affecting the rest.
In a series circuit, lamps would share the voltage and all switch off together if one fails, which is not how house lighting works.
✅ Answer: (A)
This means each lamp can have its own switch, allowing it to be turned on or off separately without affecting the rest.
In a series circuit, lamps would share the voltage and all switch off together if one fails, which is not how house lighting works.
✅ Answer: (A)
▶️ Answer/Explanation
For a fixed power output, \( P = IV \) shows that increasing the voltage means the current must decrease proportionally.
Energy is lost as heat in the cables according to \( P_{loss} = I^2R \), so a lower current greatly reduces this wasted energy.
Less energy wasted as heat means a greater proportion of the power reaches its destination, so efficiency increases.
✅ Answer: (B)
Energy is lost as heat in the cables according to \( P_{loss} = I^2R \), so a lower current greatly reduces this wasted energy.
Less energy wasted as heat means a greater proportion of the power reaches its destination, so efficiency increases.
✅ Answer: (B)
▶️ Answer/Explanation
The nucleon number (mass number), 9, is the total number of protons and neutrons in the nucleus.
The proton number (atomic number), 4, tells us there are 4 protons.
The number of neutrons is found using \( \text{neutrons} = A – Z = 9 – 4 = 5 \).
✅ Answer: (B)
The proton number (atomic number), 4, tells us there are 4 protons.
The number of neutrons is found using \( \text{neutrons} = A – Z = 9 – 4 = 5 \).
✅ Answer: (B)
▶️ Answer/Explanation
Gamma radiation has no charge, so it passes straight through the electric field undeflected — this must be X.
Beta particles are negatively charged and light, so they deflect strongly towards the positive plate — this must be Y.
Alpha particles are positively charged but much heavier, so they deflect less sharply, and towards the negative plate — this must be Z.
✅ Answer: (B)
Beta particles are negatively charged and light, so they deflect strongly towards the positive plate — this must be Y.
Alpha particles are positively charged but much heavier, so they deflect less sharply, and towards the negative plate — this must be Z.
✅ Answer: (B)