▶️ Answer/Explanation
Excretion is correctly defined as the removal of excess substances and toxic waste products from the body.
Movement is actually the ability of an organism (or part of it) to change position or place; the description given for B refers to sensitivity, not movement.
Nutrition is the process of taking in and using food for energy and growth, not the breakdown of molecules — that describes respiration.
Respiration is the release of energy from food molecules, not the manufacture of carbohydrates — that describes photosynthesis.
✅ Answer: (A)
Movement is actually the ability of an organism (or part of it) to change position or place; the description given for B refers to sensitivity, not movement.
Nutrition is the process of taking in and using food for energy and growth, not the breakdown of molecules — that describes respiration.
Respiration is the release of energy from food molecules, not the manufacture of carbohydrates — that describes photosynthesis.
✅ Answer: (A)
▶️ Answer/Explanation
Magnification is calculated using the formula: \(\text{Magnification} = \dfrac{\text{image size}}{\text{actual size}}\).
The image (diagram) length is 75 mm and the actual length of the beetle is 5 mm.
So, \(\dfrac{75}{5} = 15\).
✅ Answer: (B)
The image (diagram) length is 75 mm and the actual length of the beetle is 5 mm.
So, \(\dfrac{75}{5} = 15\).
✅ Answer: (B)
▶️ Answer/Explanation
A blue-to-purple colour change with biuret solution confirms protein is present.
A blue-to-black colour change with iodine confirms starch is present.
Benedict’s solution stays blue, meaning no reducing sugar is present, since a positive test would turn it orange/brick-red.
✅ Answer: (C)
A blue-to-black colour change with iodine confirms starch is present.
Benedict’s solution stays blue, meaning no reducing sugar is present, since a positive test would turn it orange/brick-red.
✅ Answer: (C)
▶️ Answer/Explanation
Enzymes are biological catalysts made up of long chains of amino acids.
This amino-acid-chain structure means enzymes are classified as proteins.
Their protein structure gives them a specific active site shape, which is essential for their function.
✅ Answer: (C)
This amino-acid-chain structure means enzymes are classified as proteins.
Their protein structure gives them a specific active site shape, which is essential for their function.
✅ Answer: (C)
▶️ Answer/Explanation
High temperature increases the kinetic energy of water molecules, speeding up evaporation from the leaf surface.
High wind speed removes water vapour from around the leaf quickly, maintaining a steep diffusion gradient.
Both high temperature and high wind speed together give the greatest rate of transpiration.
✅ Answer: (A)
High wind speed removes water vapour from around the leaf quickly, maintaining a steep diffusion gradient.
Both high temperature and high wind speed together give the greatest rate of transpiration.
✅ Answer: (A)
▶️ Answer/Explanation
Fibre (roughage) is the nutrient that adds bulk to food and stimulates peristalsis, helping move food through the alimentary canal.
Row C has the highest fibre content (10.9 g per 100 g) compared with the other rows.
Calcium, protein and sugar do not aid movement of food through the gut in this way.
✅ Answer: (C)
Row C has the highest fibre content (10.9 g per 100 g) compared with the other rows.
Calcium, protein and sugar do not aid movement of food through the gut in this way.
✅ Answer: (C)
▶️ Answer/Explanation
A leaf is least likely to wilt when water uptake is greater than, or closest to, water loss.
For leaf D, uptake (15) exceeds loss (10), meaning water is being replaced faster than it is lost.
In leaves A, B and C, water loss exceeds uptake, so they are more likely to wilt.
✅ Answer: (D)
For leaf D, uptake (15) exceeds loss (10), meaning water is being replaced faster than it is lost.
In leaves A, B and C, water loss exceeds uptake, so they are more likely to wilt.
✅ Answer: (D)
▶️ Answer/Explanation
The graph shows oxygen use per gram falls as body mass increases, so statement 1 is correct.
Lower oxygen use per gram means heavier shrews respire more slowly, not faster, so statement 2 is incorrect.
A smaller surface-area-to-volume ratio in heavier shrews means they lose heat more slowly, so statement 3 is correct.
✅ Answer: (C)
Lower oxygen use per gram means heavier shrews respire more slowly, not faster, so statement 2 is incorrect.
A smaller surface-area-to-volume ratio in heavier shrews means they lose heat more slowly, so statement 3 is correct.
✅ Answer: (C)
▶️ Answer/Explanation
P is a sweat gland, which releases sweat onto the skin surface for evaporative cooling.
Q is a hair, which traps an insulating layer of air close to the skin when erect.
R is an erector muscle, which contracts to pull the hair upright in cold conditions.
✅ Answer: (C)
Q is a hair, which traps an insulating layer of air close to the skin when erect.
R is an erector muscle, which contracts to pull the hair upright in cold conditions.
✅ Answer: (C)
▶️ Answer/Explanation
Fertilisation in a flower is the fusion of the male pollen nucleus with the female nucleus inside the ovule.
This fusion must occur after the pollen tube has grown down the style and reached the ovule.
Diagram B correctly shows this nucleus-to-nucleus fusion taking place inside the ovule.
✅ Answer: (B)
This fusion must occur after the pollen tube has grown down the style and reached the ovule.
Diagram B correctly shows this nucleus-to-nucleus fusion taking place inside the ovule.
✅ Answer: (B)
▶️ Answer/Explanation
Variation is the biological term for differences seen between individuals of the same species.
These differences can arise from genetic factors, environmental factors, or a combination of both.
Competition, generation and selection describe different biological processes, not this concept.
✅ Answer: (D)
These differences can arise from genetic factors, environmental factors, or a combination of both.
Competition, generation and selection describe different biological processes, not this concept.
✅ Answer: (D)
▶️ Answer/Explanation
Decomposers, such as bacteria and fungi, feed on dead organisms and waste organic matter.
This process releases nutrients back into the ecosystem for producers to reuse.
Carnivores, consumers in general, and producers obtain energy differently, not from decaying matter specifically.
✅ Answer: (C)
This process releases nutrients back into the ecosystem for producers to reuse.
Carnivores, consumers in general, and producers obtain energy differently, not from decaying matter specifically.
✅ Answer: (C)
▶️ Answer/Explanation
Burning forests releases stored carbon as carbon dioxide directly into the atmosphere.
It also removes trees that would otherwise absorb CO₂ during photosynthesis, worsening the effect.
Planting more crops or using fewer fossil fuels would instead reduce, not increase, atmospheric CO₂.
✅ Answer: (A)
It also removes trees that would otherwise absorb CO₂ during photosynthesis, worsening the effect.
Planting more crops or using fewer fossil fuels would instead reduce, not increase, atmospheric CO₂.
✅ Answer: (A)
▶️ Answer/Explanation
Filtration separates the insoluble chalk from the water and dissolved salt, since chalk does not pass through the filter paper.
Crystallisation then separates the dissolved soluble salt from the filtrate by evaporating the water until crystals form.
Chromatography and distillation are not suited to isolating a solid salt in crystal form from this mixture.
✅ Answer: (D)
Crystallisation then separates the dissolved soluble salt from the filtrate by evaporating the water until crystals form.
Chromatography and distillation are not suited to isolating a solid salt in crystal form from this mixture.
✅ Answer: (D)
▶️ Answer/Explanation
Isotopes are atoms of the same element, so they must have identical proton (and electron) numbers.
They differ only in the number of neutrons in the nucleus, giving them different mass numbers.
Any statement suggesting differing proton or electron numbers cannot describe isotopes of the same element.
✅ Answer: (B)
They differ only in the number of neutrons in the nucleus, giving them different mass numbers.
Any statement suggesting differing proton or electron numbers cannot describe isotopes of the same element.
✅ Answer: (B)
▶️ Answer/Explanation
Oxygen gas exists as the diatomic molecule \(O_2\), so it must be written as \(O_2\), not as a single \(O\) atom.
Aluminium exists as single atoms \(Al\), not as \(Al_2\), so its formula on the reactant side must be \(Al\).
Balancing \(4Al + 3O_2 \rightarrow 2Al_2O_3\) gives equal numbers of Al (4) and O (6) atoms on both sides.
✅ Answer: (D)
Aluminium exists as single atoms \(Al\), not as \(Al_2\), so its formula on the reactant side must be \(Al\).
Balancing \(4Al + 3O_2 \rightarrow 2Al_2O_3\) gives equal numbers of Al (4) and O (6) atoms on both sides.
✅ Answer: (D)
▶️ Answer/Explanation
Electrolysis requires free-moving ions, which exist in molten or aqueous ionic compounds.
Copper wire is a solid metal held together by metallic bonding with delocalised electrons, not free ions.
Aqueous copper chloride, dilute sulfuric acid and molten lead(II) bromide all contain mobile ions and can be electrolysed.
✅ Answer: (B)
Copper wire is a solid metal held together by metallic bonding with delocalised electrons, not free ions.
Aqueous copper chloride, dilute sulfuric acid and molten lead(II) bromide all contain mobile ions and can be electrolysed.
✅ Answer: (B)
▶️ Answer/Explanation
The limewater turning cloudy confirms carbon dioxide gas is produced, showing carbon has removed oxygen from the metal oxide.
Loss of oxygen from a compound is defined as reduction.
The metal oxide is therefore reduced to the free metal while the carbon is oxidised to carbon dioxide.
✅ Answer: (D)
Loss of oxygen from a compound is defined as reduction.
The metal oxide is therefore reduced to the free metal while the carbon is oxidised to carbon dioxide.
✅ Answer: (D)
▶️ Answer/Explanation
A pH decrease shows the solution becoming more acidic, meaning carbon dioxide gas is dissolving in the indicator solution to form a weak acid.
Only a carbonate reacting with an acid produces carbon dioxide gas as a product.
Zinc, zinc oxide, and zinc hydroxide react with the acid but do not release CO₂ gas.
✅ Answer: (B)
Only a carbonate reacting with an acid produces carbon dioxide gas as a product.
Zinc, zinc oxide, and zinc hydroxide react with the acid but do not release CO₂ gas.
✅ Answer: (B)
▶️ Answer/Explanation
Basic oxides are formed by metals; calcium oxide is the oxide of the metal calcium.
Carbon dioxide, nitrogen dioxide, and sulfur dioxide are all oxides of non-metals, making them acidic oxides.
Calcium oxide reacts with acids to form a salt and water, confirming its basic character.
✅ Answer: (A)
Carbon dioxide, nitrogen dioxide, and sulfur dioxide are all oxides of non-metals, making them acidic oxides.
Calcium oxide reacts with acids to form a salt and water, confirming its basic character.
✅ Answer: (A)
▶️ Answer/Explanation
Halogens are diatomic non-metals, not metals, so statement 1 is incorrect.
Halogen atoms have seven electrons in their outer shell, so statement 2 is correct.
Going down the group they change from gas to liquid to solid (not solid to liquid to gas), so statement 3 is incorrect, but they do become darker in colour, so statement 4 is correct.
✅ Answer: (C)
Halogen atoms have seven electrons in their outer shell, so statement 2 is correct.
Going down the group they change from gas to liquid to solid (not solid to liquid to gas), so statement 3 is incorrect, but they do become darker in colour, so statement 4 is correct.
✅ Answer: (C)
▶️ Answer/Explanation
Argon is a noble gas with a full outer electron shell, making it chemically unreactive.
This unreactivity means it will not react with the hot filament inside a lamp, preventing it from burning out quickly.
Being a gas or colourless are true but do not explain why it specifically protects the filament.
✅ Answer: (D)
This unreactivity means it will not react with the hot filament inside a lamp, preventing it from burning out quickly.
Being a gas or colourless are true but do not explain why it specifically protects the filament.
✅ Answer: (D)
▶️ Answer/Explanation
Aluminium ore is a finite resource, since it is not replenished on a human timescale once extracted.
Aluminium is too reactive to be extracted by heating with carbon, so carbon cannot displace it from its oxide.
Instead, molten aluminium oxide is extracted by electrolysis, which splits the compound into aluminium and oxygen.
✅ Answer: (A)
Aluminium is too reactive to be extracted by heating with carbon, so carbon cannot displace it from its oxide.
Instead, molten aluminium oxide is extracted by electrolysis, which splits the compound into aluminium and oxygen.
✅ Answer: (A)
▶️ Answer/Explanation
Sulfur dioxide is released when fossil fuels containing sulfur impurities are burned.
It is a recognised air pollutant that contributes to acid rain and respiratory problems.
Argon and nitrogen are unreactive natural components of air, and carbon dioxide is not classed as a pollutant in this context.
✅ Answer: (D)
It is a recognised air pollutant that contributes to acid rain and respiratory problems.
Argon and nitrogen are unreactive natural components of air, and carbon dioxide is not classed as a pollutant in this context.
✅ Answer: (D)
▶️ Answer/Explanation
Lime (calcium oxide) is manufactured by strongly heating limestone (calcium carbonate) in a process called thermal decomposition.
This reaction releases carbon dioxide gas, leaving solid calcium oxide behind.
Calcium hydroxide is a different compound (slaked lime), formed by adding water to calcium oxide, not by decomposing limestone.
✅ Answer: (B)
This reaction releases carbon dioxide gas, leaving solid calcium oxide behind.
Calcium hydroxide is a different compound (slaked lime), formed by adding water to calcium oxide, not by decomposing limestone.
✅ Answer: (B)
▶️ Answer/Explanation
Petroleum (crude oil) is a mixture of hydrocarbons with different boiling points.
Fractional distillation separates these hydrocarbons into fractions based on their different boiling points.
Cracking breaks larger molecules into smaller ones and is a separate process used after fractional distillation.
✅ Answer: (C)
Fractional distillation separates these hydrocarbons into fractions based on their different boiling points.
Cracking breaks larger molecules into smaller ones and is a separate process used after fractional distillation.
✅ Answer: (C)
▶️ Answer/Explanation
Polymers are large molecules built by joining many small, repeating units together in a chain.
These small repeating units are specifically called monomers.
Alkanes are a family of hydrocarbons, atoms are the basic units of elements, and components is too general a term.
✅ Answer: (D)
These small repeating units are specifically called monomers.
Alkanes are a family of hydrocarbons, atoms are the basic units of elements, and components is too general a term.
✅ Answer: (D)
▶️ Answer/Explanation
Mass is measured in kilograms, \(kg\), since it is a base SI quantity.
Gravitational field strength is defined as force per unit mass, so its unit is newtons per kilogram, \(N/kg\).
Row A is the only row giving both of these units correctly.
✅ Answer: (A)
Gravitational field strength is defined as force per unit mass, so its unit is newtons per kilogram, \(N/kg\).
Row A is the only row giving both of these units correctly.
✅ Answer: (A)
▶️ Answer/Explanation
The volume of the block is \(V = 8.0 \times 1.0 \times 0.10 = 0.80 \text{ m}^3\).
Density is calculated using \(\rho = \dfrac{m}{V} = \dfrac{440}{0.80} = 550 \text{ kg/m}^3\).
This matches option C exactly.
✅ Answer: (C)
Density is calculated using \(\rho = \dfrac{m}{V} = \dfrac{440}{0.80} = 550 \text{ kg/m}^3\).
This matches option C exactly.
✅ Answer: (C)
▶️ Answer/Explanation
Pressure is calculated using \(P = \dfrac{F}{A}\), where \(F\) is the force (weight) and \(A\) is the contact area.
Decreasing the weight reduces the numerator, and increasing the base area increases the denominator.
Both changes together must reduce the overall pressure, since \(P\) decreases whenever \(F\) falls and \(A\) rises.
✅ Answer: (B)
Decreasing the weight reduces the numerator, and increasing the base area increases the denominator.
Both changes together must reduce the overall pressure, since \(P\) decreases whenever \(F\) falls and \(A\) rises.
✅ Answer: (B)
▶️ Answer/Explanation
Work done is defined by the equation \(W = F \times d\), where \(F\) is force and \(d\) is the distance moved in the direction of the force.
Only the magnitude of the force and the distance moved determine the work done.
The mass, volume, or weight of the block do not appear in this equation and so do not directly affect work done.
✅ Answer: (A)
Only the magnitude of the force and the distance moved determine the work done.
The mass, volume, or weight of the block do not appear in this equation and so do not directly affect work done.
✅ Answer: (A)
▶️ Answer/Explanation
Cooling a gas reduces the average kinetic energy of its molecules, so their speed decreases.
Slower-moving molecules collide with the container walls less frequently and with less force.
This means the pressure of the gas also decreases at constant volume.
✅ Answer: (A)
Slower-moving molecules collide with the container walls less frequently and with less force.
This means the pressure of the gas also decreases at constant volume.
✅ Answer: (A)
▶️ Answer/Explanation
Particles in solids are closely fixed in position, so heating produces only small increases in average separation.
Particles in liquids are more loosely arranged and can expand more freely than solid particles.
Gas particles are free to move and spread out, so gases show the greatest expansion of the three states on heating.
✅ Answer: (A)
Particles in liquids are more loosely arranged and can expand more freely than solid particles.
Gas particles are free to move and spread out, so gases show the greatest expansion of the three states on heating.
✅ Answer: (A)
▶️ Answer/Explanation
A larger amplitude means the sound wave carries more energy, so the sound becomes louder (greater loudness).
A lower frequency means fewer wave oscillations per second, which is heard as a lower pitch.
So increased amplitude gives greater loudness, and decreased frequency gives lower pitch.
✅ Answer: (B)
A lower frequency means fewer wave oscillations per second, which is heard as a lower pitch.
So increased amplitude gives greater loudness, and decreased frequency gives lower pitch.
✅ Answer: (B)
▶️ Answer/Explanation
Charging by friction always involves the transfer of electrons, since protons are fixed within the nucleus and cannot move between objects.
If the rod becomes positively charged, it must have lost negative charge, meaning electrons have moved away from it.
These electrons transfer from the rod onto the cloth, leaving the rod with an overall positive charge.
✅ Answer: (B)
If the rod becomes positively charged, it must have lost negative charge, meaning electrons have moved away from it.
These electrons transfer from the rod onto the cloth, leaving the rod with an overall positive charge.
✅ Answer: (B)
▶️ Answer/Explanation
Metals contain a “sea” of delocalised electrons that are free to move throughout the metal structure.
When a potential difference is applied, these free electrons drift through the wire, constituting an electric current.
Protons and neutrons are fixed within the atomic nuclei of the metal and cannot flow.
✅ Answer: (A)
When a potential difference is applied, these free electrons drift through the wire, constituting an electric current.
Protons and neutrons are fixed within the atomic nuclei of the metal and cannot flow.
✅ Answer: (A)
▶️ Answer/Explanation
Lamp brightness depends on the current flowing through it, which increases as total circuit resistance decreases.
Placing resistors in parallel gives a lower combined resistance than placing them in series with the lamp.
Circuit D has the arrangement giving the lowest total resistance, so it produces the greatest current and the brightest lamp.
✅ Answer: (D)
Placing resistors in parallel gives a lower combined resistance than placing them in series with the lamp.
Circuit D has the arrangement giving the lowest total resistance, so it produces the greatest current and the brightest lamp.
✅ Answer: (D)
▶️ Answer/Explanation
A current-carrying wire produces a magnetic field made up of concentric circles centred on the wire.
The direction of these field lines is found using the right-hand grip rule, which for current out of the page gives anticlockwise circles.
Diagram D correctly shows this concentric, anticlockwise field pattern.
✅ Answer: (D)
The direction of these field lines is found using the right-hand grip rule, which for current out of the page gives anticlockwise circles.
Diagram D correctly shows this concentric, anticlockwise field pattern.
✅ Answer: (D)
▶️ Answer/Explanation
Alpha particles are large and heavily charged, giving them a strong ionising effect but poor penetrating ability.
Gamma rays have no charge and very little mass, making them weakly ionising but highly penetrating.
This gives: alpha is more ionising, while gamma is more penetrating.
✅ Answer: (B)
Gamma rays have no charge and very little mass, making them weakly ionising but highly penetrating.
This gives: alpha is more ionising, while gamma is more penetrating.
✅ Answer: (B)
▶️ Answer/Explanation
A half-life of 4.0 days means the activity halves every 4.0 days going forward, so going backward it doubles every 4.0 days.
8.0 days earlier is exactly \(2\) half-lives before the current time, so \(100 \times 2 \times 2 = 400\) emissions per minute.
This matches option D.
✅ Answer: (D)
8.0 days earlier is exactly \(2\) half-lives before the current time, so \(100 \times 2 \times 2 = 400\) emissions per minute.
This matches option D.
✅ Answer: (D)