▶️ Answer/Explanation
Excretion is the removal of waste products of metabolism, e.g. carbon dioxide from respiration.
Release of oxygen from photosynthesis is not excretion, since oxygen is a useful product, not a waste product of the organism’s own metabolism in this context.
✅ Answer: (B)
Release of oxygen from photosynthesis is not excretion, since oxygen is a useful product, not a waste product of the organism’s own metabolism in this context.
✅ Answer: (B)
▶️ Answer/Explanation
All living organisms are built from cells, the smallest unit capable of carrying out life processes.
Eggs and sperm are specific cell types (gametes), and mesophyll is a specific plant tissue — neither describes all organisms.
✅ Answer: (A)
Eggs and sperm are specific cell types (gametes), and mesophyll is a specific plant tissue — neither describes all organisms.
✅ Answer: (A)
▶️ Answer/Explanation
Carbohydrates and fats are made only of carbon, hydrogen and oxygen.
Proteins also contain nitrogen (and often sulfur), so a molecule with only C, H and O cannot be a protein.
✅ Answer: (A)
Proteins also contain nitrogen (and often sulfur), so a molecule with only C, H and O cannot be a protein.
✅ Answer: (A)
▶️ Answer/Explanation
Higher temperature gives particles more kinetic energy, increasing the frequency of effective enzyme–substrate collisions.
This means the curve at 60 °C rises more steeply at the start, so it has the higher initial rate, even though it later plateaus early due to denaturation.
✅ Answer: (D)
This means the curve at 60 °C rises more steeply at the start, so it has the higher initial rate, even though it later plateaus early due to denaturation.
✅ Answer: (D)
▶️ Answer/Explanation
The balanced equation is \(6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6 + 6O_2\), so 6 molecules of \(CO_2\) make 1 molecule of glucose.
To make 6 molecules of glucose, you need \(6 \times 6 = 36\) molecules of \(CO_2\).
✅ Answer: (D)
To make 6 molecules of glucose, you need \(6 \times 6 = 36\) molecules of \(CO_2\).
✅ Answer: (D)
▶️ Answer/Explanation
Statement 1 is correct: cutting the cube into eight smaller pieces increases the total surface area exposed to protease, which is why digestion is faster (80 minutes vs 320 minutes).
Statement 2 is false: chemical digestion can still occur on the whole cube, just more slowly — mechanical digestion is not essential for it to happen at all; statement 3 is correct since the faster digestion time directly shows mechanical digestion speeds up chemical digestion.
✅ Answer: (C)
Statement 2 is false: chemical digestion can still occur on the whole cube, just more slowly — mechanical digestion is not essential for it to happen at all; statement 3 is correct since the faster digestion time directly shows mechanical digestion speeds up chemical digestion.
✅ Answer: (C)
▶️ Answer/Explanation
As humidity increases, the concentration gradient of water vapour between the leaf air spaces and the outside air decreases.
This reduces the rate of diffusion of water vapour out of the stomata, so the rate of transpiration falls as humidity rises — a downward-sloping line.
✅ Answer: (C)
This reduces the rate of diffusion of water vapour out of the stomata, so the rate of transpiration falls as humidity rises — a downward-sloping line.
✅ Answer: (C)
▶️ Answer/Explanation
The oil layer seals out oxygen, so the yeast respires anaerobically: \(glucose \rightarrow ethanol + carbon dioxide\).
Carbon dioxide gas bubbles through the limewater and reacts to form insoluble calcium carbonate, turning it milky; yeast cannot photosynthesise and no oxygen is involved here.
✅ Answer: (A)
Carbon dioxide gas bubbles through the limewater and reacts to form insoluble calcium carbonate, turning it milky; yeast cannot photosynthesise and no oxygen is involved here.
✅ Answer: (A)
▶️ Answer/Explanation
A receptor detects the stimulus and the impulse travels along a sensory neurone to the spinal cord.
There it passes through a relay neurone, then a motor neurone, to the effector (muscle), producing the response.
✅ Answer: (C)
There it passes through a relay neurone, then a motor neurone, to the effector (muscle), producing the response.
✅ Answer: (C)
▶️ Answer/Explanation
Tracing the tube from the testis: sperm travel first along the sperm duct, then past the prostate gland which adds fluid, then out through the urethra.
Matching X, Y, Z in the diagram to this order (urethra, sperm duct, prostate gland) gives the sequence Z, Y, X.
✅ Answer: (D)
Matching X, Y, Z in the diagram to this order (urethra, sperm duct, prostate gland) gives the sequence Z, Y, X.
✅ Answer: (D)
▶️ Answer/Explanation
A human body cell is diploid and contains 46 chromosomes (23 pairs).
Gametes (sperm and egg cells) are haploid and contain only 23 chromosomes, one of each pair.
✅ Answer: (B)
Gametes (sperm and egg cells) are haploid and contain only 23 chromosomes, one of each pair.
✅ Answer: (B)
▶️ Answer/Explanation
An ecosystem is the whole unit of living organisms together with their physical environment, all interacting with one another.
A food web is a network of food chains, and energy flow diagrams describe processes within an ecosystem — neither is the definition of the ecosystem itself.
✅ Answer: (D)
A food web is a network of food chains, and energy flow diagrams describe processes within an ecosystem — neither is the definition of the ecosystem itself.
✅ Answer: (D)
▶️ Answer/Explanation
Excess fertiliser causes rapid algal growth; as algae and bacteria decompose, they use up dissolved oxygen, so the oxygen concentration falls sharply just after the run-off point.
Further downstream, as the nutrients are diluted and used up, oxygen levels gradually recover towards normal.
✅ Answer: (B)
Further downstream, as the nutrients are diluted and used up, oxygen levels gradually recover towards normal.
✅ Answer: (B)
▶️ Answer/Explanation
A molecule is two or more atoms chemically joined together; a single particle on its own is just an atom.
In the diagrams, W, Y and Z each show atoms bonded in groups (molecules), while X shows a single unjoined particle (an atom).
✅ Answer: (C)
In the diagrams, W, Y and Z each show atoms bonded in groups (molecules), while X shows a single unjoined particle (an atom).
✅ Answer: (C)
▶️ Answer/Explanation
Simple covalent (molecular) compounds have weak intermolecular forces, so they have low melting/boiling points and are volatile.
They contain no free ions or delocalised electrons, so they do not conduct electricity even when molten — giving high volatility and no conductivity.
✅ Answer: (A)
They contain no free ions or delocalised electrons, so they do not conduct electricity even when molten — giving high volatility and no conductivity.
✅ Answer: (A)
▶️ Answer/Explanation
Moles of \(H_2\) = \(\frac{30}{24000} = 0.00125\ mol\) (using 24 dm³ = 24000 cm³ at r.t.p.).
From the equation, moles of \(Na\) = \(2 \times 0.00125 = 0.0025\ mol\), so mass of \(Na\) = \(0.0025 \times 23 = 0.0575\ g\).
✅ Answer: (B)
From the equation, moles of \(Na\) = \(2 \times 0.00125 = 0.0025\ mol\), so mass of \(Na\) = \(0.0025 \times 23 = 0.0575\ g\).
✅ Answer: (B)
▶️ Answer/Explanation
At the cathode, positive ions are attracted and gain electrons (reduction).
Copper is less reactive than hydrogen, so \(Cu^{2+}\) ions are reduced in preference to \(H^+\) ions: \(Cu^{2+} + 2e^- \rightarrow Cu\).
✅ Answer: (A)
Copper is less reactive than hydrogen, so \(Cu^{2+}\) ions are reduced in preference to \(H^+\) ions: \(Cu^{2+} + 2e^- \rightarrow Cu\).
✅ Answer: (A)
▶️ Answer/Explanation
In the diagram, the products are at a higher energy level than the reactants, so energy has been absorbed overall.
A reaction in which energy is taken in from the surroundings (causing a temperature drop) is endothermic.
✅ Answer: (B)
A reaction in which energy is taken in from the surroundings (causing a temperature drop) is endothermic.
✅ Answer: (B)
▶️ Answer/Explanation
An oxidising agent is itself reduced (it loses oxygen, or gains electrons) while it oxidises another substance.
In option D, PbO loses its oxygen and is reduced to Pb, while it supplies that oxygen to oxidise \(H_2\) to \(H_2O\) — so PbO is the oxidising agent.
✅ Answer: (D)
In option D, PbO loses its oxygen and is reduced to Pb, while it supplies that oxygen to oxidise \(H_2\) to \(H_2O\) — so PbO is the oxidising agent.
✅ Answer: (D)
▶️ Answer/Explanation
Dilute hydrochloric acid is a strong acid, turning universal indicator red; sodium chloride solution is neutral, turning it green.
Sodium hydroxide is a strong alkali, turning it purple.
✅ Answer: (D)
Sodium hydroxide is a strong alkali, turning it purple.
✅ Answer: (D)
▶️ Answer/Explanation
Transition elements, including copper, have high densities and high melting points compared with Group I metals.
They also typically form coloured compounds (e.g. blue copper(II) sulfate), unlike most other metals which form white compounds.
✅ Answer: (A)
They also typically form coloured compounds (e.g. blue copper(II) sulfate), unlike most other metals which form white compounds.
✅ Answer: (A)
▶️ Answer/Explanation
For X to displace Y from solution, X must be higher (more reactive) than Y in the reactivity series.
Zinc is more reactive than copper, so zinc metal displaces copper from aqueous copper ions, matching X = zinc and Y = copper.
✅ Answer: (C)
Zinc is more reactive than copper, so zinc metal displaces copper from aqueous copper ions, matching X = zinc and Y = copper.
✅ Answer: (C)
▶️ Answer/Explanation
Warming an ammonium salt with sodium hydroxide releases ammonia gas, so substance Z is sodium hydroxide.
Ammonia is an alkaline gas, identified because it turns damp red litmus paper blue.
✅ Answer: (C)
Ammonia is an alkaline gas, identified because it turns damp red litmus paper blue.
✅ Answer: (C)
▶️ Answer/Explanation
In the Contact process, sulfur dioxide is catalytically oxidised to sulfur trioxide (equation 4), not made by directly burning sulfur in excess oxygen (equation 2 is not part of the real process).
The sulfur trioxide is then absorbed into concentrated sulfuric acid to form oleum, \(H_2S_2O_7\) (equation 3), which is later diluted with water to give more sulfuric acid.
✅ Answer: (D)
The sulfur trioxide is then absorbed into concentrated sulfuric acid to form oleum, \(H_2S_2O_7\) (equation 3), which is later diluted with water to give more sulfuric acid.
✅ Answer: (D)
▶️ Answer/Explanation
Limestone is calcium carbonate, \(CaCO_3\).
Heating it strongly causes thermal decomposition: \(CaCO_3 \rightarrow CaO + CO_2\), producing calcium oxide and carbon dioxide.
✅ Answer: (D)
Heating it strongly causes thermal decomposition: \(CaCO_3 \rightarrow CaO + CO_2\), producing calcium oxide and carbon dioxide.
✅ Answer: (D)
▶️ Answer/Explanation
Both compounds are alkanes (same homologous series), and longer carbon chains have stronger intermolecular forces, giving a higher boiling point and a higher relative molecular mass for \(C_{12}H_{26}\) — so statement 1 is correct, statements 2 and 3 are wrong.
Both are hydrocarbons, so both undergo complete combustion to carbon dioxide and water, making statement 4 correct.
✅ Answer: (B)
Both are hydrocarbons, so both undergo complete combustion to carbon dioxide and water, making statement 4 correct.
✅ Answer: (B)
▶️ Answer/Explanation
An amide linkage is the (-C(=O)-NH-) group, formed between an amine and a carboxylic acid (as in proteins and polyamides such as nylon).
Counting each occurrence of this exact grouping in the displayed structure gives 4 amide linkages.
✅ Answer: (A)
Counting each occurrence of this exact grouping in the displayed structure gives 4 amide linkages.
✅ Answer: (A)
▶️ Answer/Explanation
Using \(v = u + at\), the change in speed is \(\Delta v = at = 2.0 \times 5.0 = 10\ m/s\).
Final speed = \(u + \Delta v = 3.0 + 10 = 13\ m/s\).
✅ Answer: (B)
Final speed = \(u + \Delta v = 3.0 + 10 = 13\ m/s\).
✅ Answer: (B)
▶️ Answer/Explanation
The moment of a force is defined as \(moment = force \times perpendicular\ distance\ from\ the\ pivot\).
This quantity measures how much turning effect the force produces about a pivot — not speed, time, or work done.
✅ Answer: (C)
This quantity measures how much turning effect the force produces about a pivot — not speed, time, or work done.
✅ Answer: (C)
▶️ Answer/Explanation
Total mass = \(70 + 10 = 80\ kg\).
\(E_k = \frac{1}{2}mv^2 = \frac{1}{2} \times 80 \times 6.0^2 = \frac{1}{2} \times 80 \times 36 = 1440\ J\).
✅ Answer: (C)
\(E_k = \frac{1}{2}mv^2 = \frac{1}{2} \times 80 \times 6.0^2 = \frac{1}{2} \times 80 \times 36 = 1440\ J\).
✅ Answer: (C)
▶️ Answer/Explanation
Nuclear fission uses uranium, a finite fuel, so it is not renewable; but it can generate electricity continuously regardless of weather, so it is reliable at all times.
Coal is also non-renewable and unreliable in the sense its supply is finite, while wind and tides are renewable but weather/tide-dependent (not reliable at all times) — so only the nuclear row (no, yes) is fully correct.
✅ Answer: (B)
Coal is also non-renewable and unreliable in the sense its supply is finite, while wind and tides are renewable but weather/tide-dependent (not reliable at all times) — so only the nuclear row (no, yes) is fully correct.
✅ Answer: (B)
▶️ Answer/Explanation
Thermal (heat) radiation does not need a medium to travel and is mainly carried by infrared waves.
Radio, ultraviolet and X-rays are not the main carriers of heat transfer by radiation in everyday contexts.
✅ Answer: (A)
Radio, ultraviolet and X-rays are not the main carriers of heat transfer by radiation in everyday contexts.
✅ Answer: (A)
▶️ Answer/Explanation
In the diagram, the particle vibrates parallel to the direction the wave is travelling.
A wave where vibration is parallel to the direction of travel is longitudinal, and sound is the classic example of a longitudinal wave.
✅ Answer: (B)
A wave where vibration is parallel to the direction of travel is longitudinal, and sound is the classic example of a longitudinal wave.
✅ Answer: (B)
▶️ Answer/Explanation
A plane mirror always forms an image that is the same size as the object and the same distance behind the mirror as the object is in front.
The image is upright (top-to-bottom orientation unchanged), only laterally (left–right) inverted, not “inverted” in the upside-down sense.
✅ Answer: (C)
The image is upright (top-to-bottom orientation unchanged), only laterally (left–right) inverted, not “inverted” in the upside-down sense.
✅ Answer: (C)
▶️ Answer/Explanation
A soft-iron rod placed near a magnet’s pole has the opposite pole induced at the nearer end (attraction), and this pattern of opposite poles continues along each rod.
Applying this rule to both rods, sitting between the two magnets, gives the induced pole sequence S, N, S, N at J, K, L and M.
✅ Answer: (D)
Applying this rule to both rods, sitting between the two magnets, gives the induced pole sequence S, N, S, N at J, K, L and M.
✅ Answer: (D)
▶️ Answer/Explanation
Reading the graph at 50 °C gives a resistance of 3000 Ω (3.0 kΩ).
Rearranging \(R = \frac{V}{I}\) gives \(I = \frac{V}{R} = \frac{6.0}{3000} = 0.0020\ A\).
✅ Answer: (A)
Rearranging \(R = \frac{V}{I}\) gives \(I = \frac{V}{R} = \frac{6.0}{3000} = 0.0020\ A\).
✅ Answer: (A)
▶️ Answer/Explanation
Time must be in seconds: \(t = 3.0 \times 60 = 180\ s\).
\(E = IVt = 10 \times 230 \times 180 = 414\,000\ J\).
✅ Answer: (D)
\(E = IVt = 10 \times 230 \times 180 = 414\,000\ J\).
✅ Answer: (D)
▶️ Answer/Explanation
A fuse contains a thin wire that melts and breaks the circuit if the current becomes too large.
This protects the circuit by switching it off before excess current causes the cables to overheat and become a fire hazard.
✅ Answer: (D)
This protects the circuit by switching it off before excess current causes the cables to overheat and become a fire hazard.
✅ Answer: (D)
▶️ Answer/Explanation
In a d.c. motor, the split-ring commutator is connected to the coil. As the coil rotates, the commutator reverses the direction of the current through the coil every half turn (every 180°).
This ensures that the forces on the two sides of the coil always act to produce a torque in the same rotational direction, so the motor continues to spin smoothly. It does not reverse the rotation or the magnetic field.
✅ Answer: (A)
This ensures that the forces on the two sides of the coil always act to produce a torque in the same rotational direction, so the motor continues to spin smoothly. It does not reverse the rotation or the magnetic field.
✅ Answer: (A)
▶️ Answer/Explanation
An alpha particle has a mass number of 4 and an atomic number of 2.
Therefore, when uranium (atomic number 92) emits an alpha particle, the daughter nucleus has atomic number \(92 – 2 = 90\) and mass number \(X – 4 = 234\), so \(X = 238\).
Hence, \(X = 238\) and \(Y = 90\), which corresponds to option C.
✅ Answer: (C)
Therefore, when uranium (atomic number 92) emits an alpha particle, the daughter nucleus has atomic number \(92 – 2 = 90\) and mass number \(X – 4 = 234\), so \(X = 238\).
Hence, \(X = 238\) and \(Y = 90\), which corresponds to option C.
✅ Answer: (C)