▶️ Answer/Explanation
Plants photosynthesise using \(CO_2\) and water in the presence of light to build organic compounds.
They also need mineral ions (e.g. nitrate, magnesium) absorbed from the soil for growth and making chemicals such as proteins and chlorophyll.
Light energy itself, not organic compounds, is absorbed from outside — organic compounds are made, not taken in.
✅ Answer: (C)
They also need mineral ions (e.g. nitrate, magnesium) absorbed from the soil for growth and making chemicals such as proteins and chlorophyll.
Light energy itself, not organic compounds, is absorbed from outside — organic compounds are made, not taken in.
✅ Answer: (C)
▶️ Answer/Explanation
Cell membrane, nucleus, and cytoplasm are present in both plant and animal cells.
The cell wall, made of cellulose, is a rigid structure found only in plant cells.
It supports the cell and prevents it from bursting due to osmotic water uptake.
✅ Answer: (B)
The cell wall, made of cellulose, is a rigid structure found only in plant cells.
It supports the cell and prevents it from bursting due to osmotic water uptake.
✅ Answer: (B)
▶️ Answer/Explanation
Fats (lipids) are formed from one molecule of glycerol combined with three fatty acid molecules.
Glycogen and starch are polysaccharides built from glucose sub-units, not glycerol.
Proteins are built from amino acid sub-units joined by peptide bonds.
✅ Answer: (A)
Glycogen and starch are polysaccharides built from glucose sub-units, not glycerol.
Proteins are built from amino acid sub-units joined by peptide bonds.
✅ Answer: (A)
▶️ Answer/Explanation
The rate of reaction rises with temperature up to an optimum, then falls sharply.
At point X, past the peak, the falling rate shows the enzyme’s active site is being disrupted.
This happens because the temperature has gone above the optimum, starting to denature the enzyme.
✅ Answer: (D)
At point X, past the peak, the falling rate shows the enzyme’s active site is being disrupted.
This happens because the temperature has gone above the optimum, starting to denature the enzyme.
✅ Answer: (D)
▶️ Answer/Explanation
As light intensity increases from zero, the rate of photosynthesis (and so oxygen produced) increases.
Eventually another factor, such as \(CO_2\) concentration or temperature, becomes limiting.
Beyond this point the graph levels off into a plateau rather than continuing to rise indefinitely.
✅ Answer: (D)
Eventually another factor, such as \(CO_2\) concentration or temperature, becomes limiting.
Beyond this point the graph levels off into a plateau rather than continuing to rise indefinitely.
✅ Answer: (D)
▶️ Answer/Explanation
A large surface area (finger-like villi) maximises contact between food and the absorbing surface.
A good blood supply carries away absorbed glucose and amino acids, keeping the diffusion gradient steep.
Lacteals absorb fatty acids and glycerol into the lymphatic system.
Enzymes act in the small intestine’s lumen for digestion, not for absorption itself, so option 3 doesn’t fit.
✅ Answer: (A)
A good blood supply carries away absorbed glucose and amino acids, keeping the diffusion gradient steep.
Lacteals absorb fatty acids and glycerol into the lymphatic system.
Enzymes act in the small intestine’s lumen for digestion, not for absorption itself, so option 3 doesn’t fit.
✅ Answer: (A)
▶️ Answer/Explanation
Higher temperature increases the kinetic energy of water molecules, so more evaporates from the stomata.
This lowers the water potential inside the leaf, creating a steeper water potential gradient.
Water is drawn up through the xylem (not phloem, which transports sugars) to replace the lost water.
✅ Answer: (A)
This lowers the water potential inside the leaf, creating a steeper water potential gradient.
Water is drawn up through the xylem (not phloem, which transports sugars) to replace the lost water.
✅ Answer: (A)
▶️ Answer/Explanation
Aerobic respiration is summarised as \(glucose + oxygen \rightarrow carbon\ dioxide + water + energy\).
Glucose and oxygen must move into the cell, while carbon dioxide and water move out of the cell.
The correct diagram shows glucose and oxygen as inputs, with carbon dioxide and water as outputs.
✅ Answer: (C)
Glucose and oxygen must move into the cell, while carbon dioxide and water move out of the cell.
The correct diagram shows glucose and oxygen as inputs, with carbon dioxide and water as outputs.
✅ Answer: (C)
▶️ Answer/Explanation
In dim light, the pupil must increase in size to let more light reach the retina.
The radial muscles of the iris contract, pulling the iris outward and widening the pupil.
At the same time the circular muscles relax, offering less resistance to this widening.
✅ Answer: (C)
The radial muscles of the iris contract, pulling the iris outward and widening the pupil.
At the same time the circular muscles relax, offering less resistance to this widening.
✅ Answer: (C)
▶️ Answer/Explanation
Wind-pollinated flowers release huge quantities of light pollen into moving air currents.
Large anthers hanging outside the flower let pollen be caught and carried easily by the wind.
Their stigmas are typically large and feathery, but exposed outside the flower to trap airborne pollen — not small or inside.
✅ Answer: (B)
Large anthers hanging outside the flower let pollen be caught and carried easily by the wind.
Their stigmas are typically large and feathery, but exposed outside the flower to trap airborne pollen — not small or inside.
✅ Answer: (B)
▶️ Answer/Explanation
Meiosis reduces the chromosome number by half, so a cell with \(2n\) produces gametes with \(n\) chromosomes.
Crossing over and independent assortment during meiosis mean the four daughter cells are genetically different.
The correct diagram must therefore show \(n\) chromosomes in each of four genetically different cells.
✅ Answer: (D)
Crossing over and independent assortment during meiosis mean the four daughter cells are genetically different.
The correct diagram must therefore show \(n\) chromosomes in each of four genetically different cells.
✅ Answer: (D)
▶️ Answer/Explanation
Producers are organisms, mainly green plants and algae, that make their own organic food.
They do this through photosynthesis, converting light energy into chemical energy stored in glucose.
Consumers, by contrast, obtain energy by eating plants or other animals rather than making their own food.
✅ Answer: (B)
They do this through photosynthesis, converting light energy into chemical energy stored in glucose.
Consumers, by contrast, obtain energy by eating plants or other animals rather than making their own food.
✅ Answer: (B)
▶️ Answer/Explanation
Removing trees exposes bare soil, so it is no longer bound together by roots.
Without plant cover, wind and rain wash away the topsoil, causing erosion and loss of fertile soil.
Deforestation actually reduces oxygen production and photosynthetic \(CO_2\) uptake, so the other options describe benefits or unrelated effects, not undesirable ones.
✅ Answer: (B)
Without plant cover, wind and rain wash away the topsoil, causing erosion and loss of fertile soil.
Deforestation actually reduces oxygen production and photosynthetic \(CO_2\) uptake, so the other options describe benefits or unrelated effects, not undesirable ones.
✅ Answer: (B)
▶️ Answer/Explanation
The diagram shows particles of one substance spreading out and mixing with particles of another.
This spontaneous mixing, caused by random particle motion, is the process of diffusion.
It is unrelated to a change of physical state, so it isn’t condensation, evaporation, or solidification.
✅ Answer: (B)
This spontaneous mixing, caused by random particle motion, is the process of diffusion.
It is unrelated to a change of physical state, so it isn’t condensation, evaporation, or solidification.
✅ Answer: (B)
▶️ Answer/Explanation
The nucleon (mass) number is calculated as \(\text{protons} + \text{neutrons}\).
Substituting the given values: \(9 + 10 = 19\).
Electrons have negligible mass, so they aren’t included in this calculation.
✅ Answer: (C)
Substituting the given values: \(9 + 10 = 19\).
Electrons have negligible mass, so they aren’t included in this calculation.
✅ Answer: (C)
▶️ Answer/Explanation
Metal atoms lose electrons to form positive ions, since metals are electropositive.
The non-metal gains these electrons, so it causes the metal to be oxidised, making it the oxidising agent.
So statements 2 (metal loses electrons) and 4 (non-metal is oxidising agent) are the correct pair.
✅ Answer: (D)
The non-metal gains these electrons, so it causes the metal to be oxidised, making it the oxidising agent.
So statements 2 (metal loses electrons) and 4 (non-metal is oxidising agent) are the correct pair.
✅ Answer: (D)
▶️ Answer/Explanation
Hydrogen has a relative atomic mass of 1, so 1 g contains one mole, \(6 \times 10^{23}\) atoms.
Helium has a relative atomic mass of 4, so 1 g of helium is only \(\frac{1}{4}\) of a mole.
So the number of atoms is \(\frac{6 \times 10^{23}}{4} = 1.5 \times 10^{23}\).
✅ Answer: (A)
Helium has a relative atomic mass of 4, so 1 g of helium is only \(\frac{1}{4}\) of a mole.
So the number of atoms is \(\frac{6 \times 10^{23}}{4} = 1.5 \times 10^{23}\).
✅ Answer: (A)
▶️ Answer/Explanation
In concentrated aqueous NaCl, \(H^+\) ions are preferentially discharged at the cathode (gaining electrons) over \(Na^+\), since hydrogen is less reactive.
At the anode, \(Cl^-\) ions are preferentially discharged (losing electrons) because the chloride concentration is high.
So \(H^+\) gains electrons and \(Cl^-\) loses electrons.
✅ Answer: (A)
At the anode, \(Cl^-\) ions are preferentially discharged (losing electrons) because the chloride concentration is high.
So \(H^+\) gains electrons and \(Cl^-\) loses electrons.
✅ Answer: (A)
▶️ Answer/Explanation
Breaking chemical bonds always requires an input of energy to overcome the bond’s attractive forces.
Taking in energy from the surroundings, by definition, is an endothermic process.
So bond breaking is endothermic, with energy being taken in rather than given out.
✅ Answer: (B)
Taking in energy from the surroundings, by definition, is an endothermic process.
So bond breaking is endothermic, with energy being taken in rather than given out.
✅ Answer: (B)
▶️ Answer/Explanation
In reaction 3, carbon monoxide (\(CO\)) reacts with \(Fe_2O_3\) and gains oxygen to form \(CO_2\).
Gaining oxygen means carbon monoxide is oxidised, while iron oxide is reduced (loses oxygen) to iron.
In reaction 1 carbon gains oxygen, so it’s oxidised (not reduced), ruling out option A.
✅ Answer: (C)
Gaining oxygen means carbon monoxide is oxidised, while iron oxide is reduced (loses oxygen) to iron.
In reaction 1 carbon gains oxygen, so it’s oxidised (not reduced), ruling out option A.
✅ Answer: (C)
▶️ Answer/Explanation
Bromine is the only halogen that is liquid at room temperature (chlorine is a gas, iodine a solid).
Colours of the halogens get darker going down the group, from pale green chlorine to dark grey/purple iodine.
Melting and boiling points actually increase down Group VII, and the halogens are non-metals, not metals, so statements 3 and 4 are wrong.
✅ Answer: (A)
Colours of the halogens get darker going down the group, from pale green chlorine to dark grey/purple iodine.
Melting and boiling points actually increase down Group VII, and the halogens are non-metals, not metals, so statements 3 and 4 are wrong.
✅ Answer: (A)
▶️ Answer/Explanation
Filament lamps need an unreactive gas so the hot filament doesn’t burn or react with the atmosphere inside.
Argon, a noble gas, is chemically inert and cheap, making it the standard choice for this purpose.
Oxygen would allow combustion, while hydrogen is flammable, so neither is suitable.
✅ Answer: (A)
Argon, a noble gas, is chemically inert and cheap, making it the standard choice for this purpose.
Oxygen would allow combustion, while hydrogen is flammable, so neither is suitable.
✅ Answer: (A)
▶️ Answer/Explanation
An alloy is a mixture of a metal with one or more other elements, not a fixed chemical compound.
Since all alloys are still made of metals, delocalised electrons remain free to move throughout the structure.
This means all alloys, not just some, are able to conduct electricity.
✅ Answer: (C)
Since all alloys are still made of metals, delocalised electrons remain free to move throughout the structure.
This means all alloys, not just some, are able to conduct electricity.
✅ Answer: (C)
▶️ Answer/Explanation
Lead is below hydrogen in the reactivity series, so its oxide can be reduced by hydrogen gas.
Calcium is above carbon and hydrogen, so it cannot be extracted by heating with either.
Gold is unreactive and its oxide (if formed) would actually be easily reduced by carbon, and copper cannot reduce its own oxide using an even less reactive metal like gold.
✅ Answer: (D)
Calcium is above carbon and hydrogen, so it cannot be extracted by heating with either.
Gold is unreactive and its oxide (if formed) would actually be easily reduced by carbon, and copper cannot reduce its own oxide using an even less reactive metal like gold.
✅ Answer: (D)
▶️ Answer/Explanation
The Contact process uses vanadium(V) oxide (\(V_2O_5\)) as the catalyst for this reaction.
The standard operating conditions are a temperature of about \(450\,°C\) and a pressure of about 2 atm.
These moderate conditions balance a reasonable rate with a good equilibrium yield of \(SO_3\).
✅ Answer: (D)
The standard operating conditions are a temperature of about \(450\,°C\) and a pressure of about 2 atm.
These moderate conditions balance a reasonable rate with a good equilibrium yield of \(SO_3\).
✅ Answer: (D)
▶️ Answer/Explanation
Limestone is heated to manufacture calcium oxide, and calcium compounds neutralise acidic industrial waste and acidic soil.
Purifying water for drinking mainly relies on filtration, sedimentation, and chlorination, not limestone.
So of the four options, purifying water is not a genuine use of limestone.
✅ Answer: (C)
Purifying water for drinking mainly relies on filtration, sedimentation, and chlorination, not limestone.
So of the four options, purifying water is not a genuine use of limestone.
✅ Answer: (C)
▶️ Answer/Explanation
Nylon is a condensation polymer made by joining monomers through amide linkages, \(-CO-NH-\).
Its structure repeats this linkage with carbon chains between successive amide groups.
The correct diagram shows this repeating pattern of \(C(=O)\) and \(NH\) groups linked in a chain.
✅ Answer: (B)
Its structure repeats this linkage with carbon chains between successive amide groups.
The correct diagram shows this repeating pattern of \(C(=O)\) and \(NH\) groups linked in a chain.
✅ Answer: (B)
▶️ Answer/Explanation
The volume of the rock equals the volume of water it displaces: \(650 – 500 = 150\ cm^3\).
Density is calculated as \(\text{density} = \frac{\text{mass}}{\text{volume}}\).
Substituting gives \(\frac{360}{150}\) g/cm³.
✅ Answer: (A)
Density is calculated as \(\text{density} = \frac{\text{mass}}{\text{volume}}\).
Substituting gives \(\frac{360}{150}\) g/cm³.
✅ Answer: (A)
▶️ Answer/Explanation
The load’s distance from the pivot is \(40\ cm\), and the force’s distance from the pivot is \(100 – 40 – 10 = 50\ cm\).
At equilibrium, the principle of moments gives \(70 \times 40 = F \times 50\).
Solving: \(F = \frac{2800}{50} = 56\ N\).
✅ Answer: (B)
At equilibrium, the principle of moments gives \(70 \times 40 = F \times 50\).
Solving: \(F = \frac{2800}{50} = 56\ N\).
✅ Answer: (B)
▶️ Answer/Explanation
The energy transferred to the object is \(50 – 20 = 30\ J\).
Power is calculated using \(\text{power} = \frac{\text{energy transferred}}{\text{time}}\).
Substituting: \(\frac{30}{5.0} = 6.0\ W\).
✅ Answer: (B)
Power is calculated using \(\text{power} = \frac{\text{energy transferred}}{\text{time}}\).
Substituting: \(\frac{30}{5.0} = 6.0\ W\).
✅ Answer: (B)
▶️ Answer/Explanation
Water stored at height in a reservoir possesses gravitational potential energy.
As the water falls, this potential energy converts to kinetic energy, which turns a turbine.
The turbine drives a generator that converts this energy into electrical energy.
✅ Answer: (C)
As the water falls, this potential energy converts to kinetic energy, which turns a turbine.
The turbine drives a generator that converts this energy into electrical energy.
✅ Answer: (C)
▶️ Answer/Explanation
A liquid that expands more per degree gives a bigger movement along the tube for the same temperature change.
This means the thermometer’s sensitivity increases, since smaller temperature changes now produce visible movement.
However, for a fixed-length tube, a bigger expansion per degree means the same tube length now covers a smaller temperature span, so the range decreases.
✅ Answer: (C)
This means the thermometer’s sensitivity increases, since smaller temperature changes now produce visible movement.
However, for a fixed-length tube, a bigger expansion per degree means the same tube length now covers a smaller temperature span, so the range decreases.
✅ Answer: (C)
▶️ Answer/Explanation
When air is heated, its particles gain energy and move further apart, so the air expands.
This expansion reduces the air’s density compared with the surrounding cooler air.
Being warmer and less dense, this air experiences an upward buoyant force and rises.
✅ Answer: (C)
This expansion reduces the air’s density compared with the surrounding cooler air.
Being warmer and less dense, this air experiences an upward buoyant force and rises.
✅ Answer: (C)
▶️ Answer/Explanation
Light travelling from diamond (denser) into air (less dense) bends away from the normal.
The angle of incidence inside the diamond is 20°, which is less than the critical angle of 25°, so refraction (not total internal reflection) occurs.
Since air is less dense, the refracted angle in air must be larger than the incident angle, so it comes out at 30°, bent away from the normal.
✅ Answer: (D)
The angle of incidence inside the diamond is 20°, which is less than the critical angle of 25°, so refraction (not total internal reflection) occurs.
Since air is less dense, the refracted angle in air must be larger than the incident angle, so it comes out at 30°, bent away from the normal.
✅ Answer: (D)
▶️ Answer/Explanation
Sound travels fastest through solids, since their particles are packed most closely together, allowing vibrations to pass on quickly.
It travels slower in liquids, where particles are more spread out, and slowest in gases, with particles furthest apart.
So the lowest speed (480 m/s) corresponds to a gas, the middle speed (1500 m/s) to a liquid, and the highest (1800 m/s) to a solid.
✅ Answer: (A)
It travels slower in liquids, where particles are more spread out, and slowest in gases, with particles furthest apart.
So the lowest speed (480 m/s) corresponds to a gas, the middle speed (1500 m/s) to a liquid, and the highest (1800 m/s) to a solid.
✅ Answer: (A)
▶️ Answer/Explanation
An electromagnet’s magnetic field exists only while current flows through its coil.
Switching the current on and off rapidly instantly creates and removes the magnetic field.
A permanent magnet’s field comes from its fixed internal structure and cannot be switched off this way.
✅ Answer: (A)
Switching the current on and off rapidly instantly creates and removes the magnetic field.
A permanent magnet’s field comes from its fixed internal structure and cannot be switched off this way.
✅ Answer: (A)
▶️ Answer/Explanation
Charging by friction transfers electrons from one surface to the other; nothing is created or destroyed.
Since the rod ends up negatively charged, it must have gained electrons, which came from the cloth.
Having lost electrons, the cloth is left with an excess of positive charge.
✅ Answer: (D)
Since the rod ends up negatively charged, it must have gained electrons, which came from the cloth.
Having lost electrons, the cloth is left with an excess of positive charge.
✅ Answer: (D)
▶️ Answer/Explanation
A fuse rating must be higher than the normal operating current of 3.1 A, or it would blow during ordinary use.
A 3 A fuse would blow immediately since 3.1 A exceeds this rating.
The next standard rating above 3.1 A is 5 A, which allows normal operation but still blows if the current rises dangerously higher.
✅ Answer: (C)
A 3 A fuse would blow immediately since 3.1 A exceeds this rating.
The next standard rating above 3.1 A is 5 A, which allows normal operation but still blows if the current rises dangerously higher.
✅ Answer: (C)
▶️ Answer/Explanation
This is the motor effect: a current-carrying wire in a magnetic field experiences a force.
Using Fleming’s left-hand rule, with the First finger along the field (S to N) and seCond finger along the current, the thuMb gives the force direction.
Applying this to the given field and current directions gives the force acting in direction B.
✅ Answer: (B)
Using Fleming’s left-hand rule, with the First finger along the field (S to N) and seCond finger along the current, the thuMb gives the force direction.
Applying this to the given field and current directions gives the force acting in direction B.
✅ Answer: (B)
▶️ Answer/Explanation
Isotopes are atoms of the same element, so they must have identical proton numbers.
They differ only in neutron number, giving them different nucleon (mass) numbers.
The correct pair shows two nuclei with the same number of protons but a different number of neutrons.
✅ Answer: (B)
They differ only in neutron number, giving them different nucleon (mass) numbers.
The correct pair shows two nuclei with the same number of protons but a different number of neutrons.
✅ Answer: (B)