▶️ Answer/Explanation
Plants make their own organic compounds by photosynthesis, so these are not required as inputs.
Photosynthesis requires carbon dioxide (\(\text{CO}_2\)), water (\(\text{H}_2\text{O}\)) and light.
Ions are absorbed separately from the soil for healthy growth.
✅ Answer: (C)
Photosynthesis requires carbon dioxide (\(\text{CO}_2\)), water (\(\text{H}_2\text{O}\)) and light.
Ions are absorbed separately from the soil for healthy growth.
✅ Answer: (C)
▶️ Answer/Explanation
The concentrated salt solution has a lower (more negative) water potential than the cell contents.
Water always moves down a water potential gradient, from a region of higher water potential to lower water potential.
So water moves out of the cells, causing them to plasmolyse (shrink away from the cell wall).
✅ Answer: (B)
Water always moves down a water potential gradient, from a region of higher water potential to lower water potential.
So water moves out of the cells, causing them to plasmolyse (shrink away from the cell wall).
✅ Answer: (B)
▶️ Answer/Explanation
Fats (lipids) are formed from \(1\) molecule of glycerol joined to \(3\) fatty acid molecules.
Glycogen and starch are carbohydrates built from many glucose (\(\text{C}_6\text{H}_{12}\text{O}_6\)) units, not glycerol.
Proteins are built from amino acids.
✅ Answer: (A)
Glycogen and starch are carbohydrates built from many glucose (\(\text{C}_6\text{H}_{12}\text{O}_6\)) units, not glycerol.
Proteins are built from amino acids.
✅ Answer: (A)
▶️ Answer/Explanation
The rate of reaction rises to a peak at around \(40\,^{\circ}\text{C}\), then falls sharply at point X, where the temperature is above \(40\,^{\circ}\text{C}\).
This is beyond the enzyme’s optimum temperature, so the enzyme is starting to denature.
The rate is still greater than \(0\), so the enzyme has not fully stopped working.
✅ Answer: (D)
This is beyond the enzyme’s optimum temperature, so the enzyme is starting to denature.
The rate is still greater than \(0\), so the enzyme has not fully stopped working.
✅ Answer: (D)
▶️ Answer/Explanation
Layer A is the upper epidermis, and layer B shows tall, tightly packed columnar cells — the palisade mesophyll.
Layer C shows loosely packed, irregularly shaped cells with air spaces between them — this is the spongy mesophyll.
Layer D is the lower epidermis.
✅ Answer: (C)
Layer C shows loosely packed, irregularly shaped cells with air spaces between them — this is the spongy mesophyll.
Layer D is the lower epidermis.
✅ Answer: (C)
▶️ Answer/Explanation
Kwashiorkor is a well-known protein-deficiency disease.
Low protein intake lowers blood protein levels, reducing water reabsorption into the blood and causing swelling (oedema).
Poor growth also results from insufficient protein for building new tissue.
✅ Answer: (B)
Low protein intake lowers blood protein levels, reducing water reabsorption into the blood and causing swelling (oedema).
Poor growth also results from insufficient protein for building new tissue.
✅ Answer: (B)
▶️ Answer/Explanation
Deoxygenated blood leaves the heart through the pulmonary artery, travelling to the lungs.
At the lungs, gas exchange oxygenates the blood.
Oxygenated blood then returns to the heart through the pulmonary vein.
✅ Answer: (A)
At the lungs, gas exchange oxygenates the blood.
Oxygenated blood then returns to the heart through the pulmonary vein.
✅ Answer: (A)
▶️ Answer/Explanation
Running increases the rate of respiration, so \(\text{CO}_2\) in the venous blood rises quickly and then levels off.
This rise in \(\text{CO}_2\) is detected by chemoreceptors, causing breathing rate to increase and then plateau at a higher level.
Only graph C shows both breathing rate and \(\text{CO}_2\) concentration rising quickly and then levelling off together.
✅ Answer: (C)
This rise in \(\text{CO}_2\) is detected by chemoreceptors, causing breathing rate to increase and then plateau at a higher level.
Only graph C shows both breathing rate and \(\text{CO}_2\) concentration rising quickly and then levelling off together.
✅ Answer: (C)
▶️ Answer/Explanation
Between X and Y, body temperature rises above the normal set point of about \(37\,^{\circ}\text{C}\).
To lose this excess heat, sweat glands produce more sweat, which cools the skin as it evaporates.
Shivering, and decreased breathing/pulse rate, would not cause cooling.
✅ Answer: (D)
To lose this excess heat, sweat glands produce more sweat, which cools the skin as it evaporates.
Shivering, and decreased breathing/pulse rate, would not cause cooling.
✅ Answer: (D)
▶️ Answer/Explanation
Asexual reproduction produces genetically identical offspring (clones), so statement \(1\) is false.
Asexual reproduction does not require flowers at all, so statement \(2\) is false.
It allows many offspring to be produced quickly without needing a mate, so statement \(3\) is a true advantage.
✅ Answer: (C)
Asexual reproduction does not require flowers at all, so statement \(2\) is false.
It allows many offspring to be produced quickly without needing a mate, so statement \(3\) is a true advantage.
✅ Answer: (C)
▶️ Answer/Explanation
Haploid means one full set of chromosomes, with no matching (homologous) pairs.
The diagram shows \(4\) different, unpaired chromosomes — no two are alike.
The number of chromosomes itself does not define “haploid”; the lack of pairing does.
✅ Answer: (D)
The diagram shows \(4\) different, unpaired chromosomes — no two are alike.
The number of chromosomes itself does not define “haploid”; the lack of pairing does.
✅ Answer: (D)
▶️ Answer/Explanation
A carnivore is an animal that obtains its energy by eating other animals.
Eating plants describes a herbivore, and feeding on dead matter describes a decomposer/saprotroph.
Making its own organic matter describes a producer, such as a green plant.
✅ Answer: (A)
Eating plants describes a herbivore, and feeding on dead matter describes a decomposer/saprotroph.
Making its own organic matter describes a producer, such as a green plant.
✅ Answer: (A)
▶️ Answer/Explanation
Removing trees exposes soil to wind and rain, with no roots left to bind it in place.
This leads to erosion, washing away fertile topsoil.
The other options describe either false effects, or short-term “benefits” rather than undesirable effects.
✅ Answer: (B)
This leads to erosion, washing away fertile topsoil.
The other options describe either false effects, or short-term “benefits” rather than undesirable effects.
✅ Answer: (B)
▶️ Answer/Explanation
\(\text{CO}_2\), Ne and \(\text{N}_2\) are all gases at room temperature, with widely spaced particles.
Zn (zinc) is a solid metal at room temperature.
Particles in a solid are packed tightly together in a fixed arrangement, closer than in a gas.
✅ Answer: (D)
Zn (zinc) is a solid metal at room temperature.
Particles in a solid are packed tightly together in a fixed arrangement, closer than in a gas.
✅ Answer: (D)
▶️ Answer/Explanation
Number of neutrons \(=\) mass number \(-\) proton number.
\(35 – 17 = 18\).
So this chlorine isotope has \(18\) neutrons.
✅ Answer: (B)
\(35 – 17 = 18\).
So this chlorine isotope has \(18\) neutrons.
✅ Answer: (B)
▶️ Answer/Explanation
Non-metal atoms typically form ions by gaining electrons (to complete their outer shell), not by losing them.
Statement B has this backwards, so it is incorrect.
Statements A, C and D are all true descriptions of ion formation and behaviour.
✅ Answer: (B)
Statement B has this backwards, so it is incorrect.
Statements A, C and D are all true descriptions of ion formation and behaviour.
✅ Answer: (B)
▶️ Answer/Explanation
\(1\,\text{g}\) of hydrogen (\(A_r = 1\)) is exactly \(1\) mole, containing \(6 \times 10^{23}\) atoms.
\(1\,\text{g}\) of helium (\(A_r = 4\)) is only \(\frac{1}{4}\) of a mole.
So the number of atoms \(= 6 \times 10^{23} \div 4 = 1.5 \times 10^{23}\).
✅ Answer: (A)
\(1\,\text{g}\) of helium (\(A_r = 4\)) is only \(\frac{1}{4}\) of a mole.
So the number of atoms \(= 6 \times 10^{23} \div 4 = 1.5 \times 10^{23}\).
✅ Answer: (A)
▶️ Answer/Explanation
Calcium ions carry a \(2+\) charge, \(\text{Ca}^{2+}\), not \(1+\).
At the cathode, positive ions gain electrons (reduction) to form the metal atom.
So \(\text{Ca}^{2+}\) must gain \(2\) electrons to balance charge: \(\text{Ca}^{2+} + 2e^- \rightarrow \text{Ca}\).
✅ Answer: (D)
At the cathode, positive ions gain electrons (reduction) to form the metal atom.
So \(\text{Ca}^{2+}\) must gain \(2\) electrons to balance charge: \(\text{Ca}^{2+} + 2e^- \rightarrow \text{Ca}\).
✅ Answer: (D)
▶️ Answer/Explanation
In an exothermic reaction, energy is released, so the products end up at a lower energy level than the reactants.
Diagram D shows the reactant line starting high, rising over the activation energy (\(E_a\)) hump, then finishing lower than the start.
The other diagrams show the products ending at the same or higher energy than the reactants.
✅ Answer: (D)
Diagram D shows the reactant line starting high, rising over the activation energy (\(E_a\)) hump, then finishing lower than the start.
The other diagrams show the products ending at the same or higher energy than the reactants.
✅ Answer: (D)
▶️ Answer/Explanation
In \(2\text{Na} + \text{Cl}_2 \rightarrow 2\text{NaCl}\), sodium atoms lose electrons (oxidation) and chlorine atoms gain electrons (reduction).
The other three equations are thermal decomposition, dehydration, and neutralisation — none involve electron transfer.
A reaction involving both oxidation and reduction together is a redox reaction.
✅ Answer: (C)
The other three equations are thermal decomposition, dehydration, and neutralisation — none involve electron transfer.
A reaction involving both oxidation and reduction together is a redox reaction.
✅ Answer: (C)
▶️ Answer/Explanation
Transition elements are typical metals with high melting points, not low ones.
They do commonly act as catalysts, form coloured compounds, and have high densities.
So “low melting points” is the statement that is not correct.
✅ Answer: (D)
They do commonly act as catalysts, form coloured compounds, and have high densities.
So “low melting points” is the statement that is not correct.
✅ Answer: (D)
▶️ Answer/Explanation
The atmosphere inside the lamp must be unreactive (inert) so it does not react with the hot filament.
Argon is an unreactive noble gas and is denser than air, which helps reduce evaporation of the filament.
Hydrogen and oxygen are reactive and would react with the hot wire.
✅ Answer: (A)
Argon is an unreactive noble gas and is denser than air, which helps reduce evaporation of the filament.
Hydrogen and oxygen are reactive and would react with the hot wire.
✅ Answer: (A)
▶️ Answer/Explanation
Alloys are mixtures of metals, not chemical compounds, since there is no fixed ratio or new type of bonding formed.
Because they are still made of metal atoms delocalised electrons remain free to move, so all alloys retain metallic bonding and conduct electricity.
So gap \(1\) \(=\) “mixtures” and gap \(2\) \(=\) “All”.
✅ Answer: (C)
Because they are still made of metal atoms delocalised electrons remain free to move, so all alloys retain metallic bonding and conduct electricity.
So gap \(1\) \(=\) “mixtures” and gap \(2\) \(=\) “All”.
✅ Answer: (C)
▶️ Answer/Explanation
A more reactive metal reduces the oxide of a less reactive one, so S must be more reactive than both R and P.
Since P cannot reduce R’s oxide but S can, the order so far is: P less reactive than R, less reactive than S.
Since both P and S can reduce Q’s oxide, Q is the least reactive of all \(4\): order is Q, P, R, S from least to most reactive.
✅ Answer: (B)
Since P cannot reduce R’s oxide but S can, the order so far is: P less reactive than R, less reactive than S.
Since both P and S can reduce Q’s oxide, Q is the least reactive of all \(4\): order is Q, P, R, S from least to most reactive.
✅ Answer: (B)
▶️ Answer/Explanation
The Contact process uses a vanadium(V) oxide (\(\text{V}_2\text{O}_5\)) catalyst, not iron, so statement \(1\) is false.
Sulfur trioxide (\(\text{SO}_3\)) is not reacted directly with water, as this is too violent; instead it is dissolved in concentrated sulfuric acid to form oleum, which is then diluted with water, so statement \(4\) is false.
Statement \(3\) (\(\text{SO}_2 \rightarrow \text{SO}_3\)) and statement \(2\) (oleum diluted with water) are both correct.
✅ Answer: (C)
Sulfur trioxide (\(\text{SO}_3\)) is not reacted directly with water, as this is too violent; instead it is dissolved in concentrated sulfuric acid to form oleum, which is then diluted with water, so statement \(4\) is false.
Statement \(3\) (\(\text{SO}_2 \rightarrow \text{SO}_3\)) and statement \(2\) (oleum diluted with water) are both correct.
✅ Answer: (C)
▶️ Answer/Explanation
Limestone (calcium carbonate, \(\text{CaCO}_3\)) is heated to make calcium oxide (quicklime), \(\text{CaCO}_3 \rightarrow \text{CaO} + \text{CO}_2\).
Because it is a base, it is used to neutralise acidic industrial waste and acidic soils.
Water purification uses processes such as filtration, carbon, and chlorination, not limestone.
✅ Answer: (C)
Because it is a base, it is used to neutralise acidic industrial waste and acidic soils.
Water purification uses processes such as filtration, carbon, and chlorination, not limestone.
✅ Answer: (C)
links.
links.▶️ Answer/Explanation
Addition polymers form when many identical monomer molecules (each usually containing a \(\text{C}=\text{C}\) double bond) join together.
The resulting polymer chain is built from only that one repeating monomer unit, with no double bonds remaining in the chain.
Amide and ester links describe condensation polymers, such as nylon and polyester, not addition polymers.
✅ Answer: (A)
The resulting polymer chain is built from only that one repeating monomer unit, with no double bonds remaining in the chain.
Amide and ester links describe condensation polymers, such as nylon and polyester, not addition polymers.
✅ Answer: (A)
▶️ Answer/Explanation
Mass is the amount of matter in the object, and does not change with location.
Weight is calculated using \(W = mg\), and depends on gravitational field strength \(g\).
Since \(g\) is greater at the North Pole, weight increases while mass stays the same.
✅ Answer: (C)
Weight is calculated using \(W = mg\), and depends on gravitational field strength \(g\).
Since \(g\) is greater at the North Pole, weight increases while mass stays the same.
✅ Answer: (C)
▶️ Answer/Explanation
Weight of \(n\) bricks \(= n \times 1.5 \times 10 = 15n\,\text{N}\).
Using \(P = \frac{F}{A}\): \(5700 = \frac{15n}{0.030}\), so \(15n = 171\), giving \(n = 11.4\).
Since the pressure limit must not be exceeded, the number of bricks must be rounded down to the nearest whole number.
✅ Answer: (A)
Using \(P = \frac{F}{A}\): \(5700 = \frac{15n}{0.030}\), so \(15n = 171\), giving \(n = 11.4\).
Since the pressure limit must not be exceeded, the number of bricks must be rounded down to the nearest whole number.
✅ Answer: (A)
▶️ Answer/Explanation
The standard formula for kinetic energy is \(\text{K.E.} = \frac{1}{2}mv^2\).
\(mgh\) is the formula for gravitational potential energy, not kinetic energy.
The other options incorrectly square the whole \(mv\) term or omit the \(\frac{1}{2}\).
✅ Answer: (B)
\(mgh\) is the formula for gravitational potential energy, not kinetic energy.
The other options incorrectly square the whole \(mv\) term or omit the \(\frac{1}{2}\).
✅ Answer: (B)
▶️ Answer/Explanation
Power is energy transferred per second: \(P = \frac{E}{t}\).
Converting energy: \(400\,\text{kJ} = 400\,000\,\text{J}\).
\(P = \frac{400\,000}{5.0} = 80\,000\,\text{W}\).
✅ Answer: (C)
Converting energy: \(400\,\text{kJ} = 400\,000\,\text{J}\).
\(P = \frac{400\,000}{5.0} = 80\,000\,\text{W}\).
✅ Answer: (C)
▶️ Answer/Explanation
Water is stored at height behind a dam, giving it gravitational potential energy, \(E_p = mgh\).
As it falls, this converts to kinetic energy, turning turbines connected to generators.
The generators then transfer this to electrical energy.
✅ Answer: (C)
As it falls, this converts to kinetic energy, turning turbines connected to generators.
The generators then transfer this to electrical energy.
✅ Answer: (C)
▶️ Answer/Explanation
Heating the gas increases the average kinetic energy of its molecules.
Faster-moving molecules collide with the container walls more often and with greater force.
At constant volume, this means the pressure of the gas increases.
✅ Answer: (D)
Faster-moving molecules collide with the container walls more often and with greater force.
At constant volume, this means the pressure of the gas increases.
✅ Answer: (D)
▶️ Answer/Explanation
Light travels faster in air, so on leaving the diamond it must bend away from the normal (angle in air \(>\) angle in diamond).
The angle inside the diamond must be less than the critical angle (\(25^{\circ}\)) for the light to refract out rather than totally internally reflect.
Only the diagram with a \(20^{\circ}\) angle in diamond, bending away from the normal into air, satisfies both conditions.
✅ Answer: (D)
The angle inside the diamond must be less than the critical angle (\(25^{\circ}\)) for the light to refract out rather than totally internally reflect.
Only the diagram with a \(20^{\circ}\) angle in diamond, bending away from the normal into air, satisfies both conditions.
✅ Answer: (D)
▶️ Answer/Explanation
An electromagnet’s magnetism depends entirely on current flowing through its coil.
Switching the current on and off rapidly switches the magnetism on and off just as fast.
A permanent magnet’s magnetism cannot be switched off in this way.
✅ Answer: (A)
Switching the current on and off rapidly switches the magnetism on and off just as fast.
A permanent magnet’s magnetism cannot be switched off in this way.
✅ Answer: (A)
▶️ Answer/Explanation
Current is charge per unit time: \(I = \frac{Q}{t}\).
Convert time to seconds: \(3.0\) minutes \(= 180\,\text{s}\).
\(I = \frac{480}{180} = 2.7\,\text{A}\).
✅ Answer: (A)
Convert time to seconds: \(3.0\) minutes \(= 180\,\text{s}\).
\(I = \frac{480}{180} = 2.7\,\text{A}\).
✅ Answer: (A)
▶️ Answer/Explanation
In a parallel circuit, each lamp is on its own separate branch, with the full supply p.d. across it.
If one lamp fails (breaking its branch), current can still flow through the other branches.
In series, a break anywhere stops current everywhere, so all lamps would go out together.
✅ Answer: (D)
If one lamp fails (breaking its branch), current can still flow through the other branches.
In series, a break anywhere stops current everywhere, so all lamps would go out together.
✅ Answer: (D)
▶️ Answer/Explanation
A fuse contains a thin wire designed to melt and break the circuit if the current becomes too large.
This protects the rest of the circuit and its wiring from overheating or fire.
Lamps, resistors and thermistors are not designed to melt as a safety mechanism.
✅ Answer: (A)
This protects the rest of the circuit and its wiring from overheating or fire.
Lamps, resistors and thermistors are not designed to melt as a safety mechanism.
✅ Answer: (A)
▶️ Answer/Explanation
The magnetic field points from the N pole to the S pole, across the gap.
Using Fleming’s left-hand rule with the given current direction and field direction, the force (thrust) points upward, in direction B.
This is the motor effect: a current-carrying wire in a magnetic field experiences a force perpendicular to both the current and the field.
✅ Answer: (B)
Using Fleming’s left-hand rule with the given current direction and field direction, the force (thrust) points upward, in direction B.
This is the motor effect: a current-carrying wire in a magnetic field experiences a force perpendicular to both the current and the field.
✅ Answer: (B)
▶️ Answer/Explanation
Isotopes of the same element must have identical numbers of protons but different numbers of neutrons.
In pair B, both nuclei have the same number of protons (black circles) but a different number of neutrons (white circles).
The other pairs either differ in proton number (different elements) or have identical proton and neutron counts (identical nuclei, not different isotopes).
✅ Answer: (B)
In pair B, both nuclei have the same number of protons (black circles) but a different number of neutrons (white circles).
The other pairs either differ in proton number (different elements) or have identical proton and neutron counts (identical nuclei, not different isotopes).
✅ Answer: (B)