▶️ Answer/Explanation
Chasing after the ball is movement, a physical response of the whole organism.
Bringing the ball back shows the dog is detecting and responding to a stimulus (sensitivity).
Nutrition and growth are not involved in this behaviour at all.
✅ Answer: (C)
Bringing the ball back shows the dog is detecting and responding to a stimulus (sensitivity).
Nutrition and growth are not involved in this behaviour at all.
✅ Answer: (C)
▶️ Answer/Explanation
The cytoplasm of a red blood cell is packed with haemoglobin, which binds oxygen.
The absence of a nucleus increases (not minimises) space for oxygen binding, so A is wrong.
The biconcave shape gives a large surface area to volume ratio and is not related to travel through arteries.
✅ Answer: (C)
The absence of a nucleus increases (not minimises) space for oxygen binding, so A is wrong.
The biconcave shape gives a large surface area to volume ratio and is not related to travel through arteries.
✅ Answer: (C)
▶️ Answer/Explanation
The test for reducing sugar uses Benedict’s solution, which must be heated to form a coloured (brick-red) precipitate.
The fat (ethanol emulsion), protein (biuret) and starch (iodine) tests are all carried out at room temperature.
✅ Answer: (C)
The fat (ethanol emulsion), protein (biuret) and starch (iodine) tests are all carried out at room temperature.
✅ Answer: (C)
▶️ Answer/Explanation
Between X and Y the temperature is still rising towards the optimum, so no denaturation has occurred yet.
As temperature rises, enzyme and substrate molecules gain more kinetic energy and move faster.
This causes more frequent successful collisions between enzyme and substrate, increasing the rate of reaction.
✅ Answer: (D)
As temperature rises, enzyme and substrate molecules gain more kinetic energy and move faster.
This causes more frequent successful collisions between enzyme and substrate, increasing the rate of reaction.
✅ Answer: (D)
▶️ Answer/Explanation
Nitrate ions provide the nitrogen needed to make amino acids, which are then built into proteins.
Magnesium ions are needed to make chlorophyll, the pigment used in photosynthesis.
So statement 2 (nitrate → amino acids) and statement 3 (magnesium → chlorophyll) are both correct.
✅ Answer: (B)
Magnesium ions are needed to make chlorophyll, the pigment used in photosynthesis.
So statement 2 (nitrate → amino acids) and statement 3 (magnesium → chlorophyll) are both correct.
✅ Answer: (B)
▶️ Answer/Explanation
Mechanical digestion physically breaks food into smaller pieces, e.g. by chewing, increasing surface area.
No chemical bonds are broken, so the food molecules themselves are unchanged (statement 2).
Turning large molecules into small soluble ones (statements 3 and 4) is chemical digestion, not mechanical.
✅ Answer: (A)
No chemical bonds are broken, so the food molecules themselves are unchanged (statement 2).
Turning large molecules into small soluble ones (statements 3 and 4) is chemical digestion, not mechanical.
✅ Answer: (A)
▶️ Answer/Explanation
Xylem vessels transport water and dissolved mineral ions absorbed by the roots.
The direction of flow in xylem is always from the roots up to the leaves, driven by transpiration.
Sucrose is carried by phloem, not xylem, ruling out rows A and B.
✅ Answer: (D)
The direction of flow in xylem is always from the roots up to the leaves, driven by transpiration.
Sucrose is carried by phloem, not xylem, ruling out rows A and B.
✅ Answer: (D)
▶️ Answer/Explanation
During gas exchange, some of the oxygen in inhaled air (about 21%) is absorbed into the blood, so expired air contains a lower concentration, around 16%.
Air is moistened as it passes through the airways and lungs, so expired air is always saturated with water vapour.
✅ Answer: (A)
Air is moistened as it passes through the airways and lungs, so expired air is always saturated with water vapour.
✅ Answer: (A)
▶️ Answer/Explanation
In hot conditions, arterioles supplying skin capillaries dilate (vasodilation), increasing blood flow to the skin surface.
This allows more heat to be lost by radiation, cooling the body down.
In cold conditions the opposite occurs: arterioles constrict (vasoconstriction) to reduce heat loss.
✅ Answer: (D)
This allows more heat to be lost by radiation, cooling the body down.
In cold conditions the opposite occurs: arterioles constrict (vasoconstriction) to reduce heat loss.
✅ Answer: (D)
▶️ Answer/Explanation
Insect-pollinated flowers have large, often scented petals to attract insects, so statement 2 is correct.
Wind-pollinated flowers have stigmas that dangle outside the flower to catch airborne pollen, so statement 4 is correct.
Statements 1 and 3 describe the features the wrong way round, so they are incorrect.
✅ Answer: (C)
Wind-pollinated flowers have stigmas that dangle outside the flower to catch airborne pollen, so statement 4 is correct.
Statements 1 and 3 describe the features the wrong way round, so they are incorrect.
✅ Answer: (C)
▶️ Answer/Explanation
A diploid nucleus contains two full sets of chromosomes, while a haploid nucleus contains only one set.
So the diploid nucleus always has more chromosomes than the haploid nucleus from the same organism.
Haploid nuclei are produced by meiosis (not mitosis), so B and C are incorrect.
✅ Answer: (A)
So the diploid nucleus always has more chromosomes than the haploid nucleus from the same organism.
Haploid nuclei are produced by meiosis (not mitosis), so B and C are incorrect.
✅ Answer: (A)
▶️ Answer/Explanation
An ecosystem is defined as a unit made up of all the organisms in a given area interacting with each other and with the non-living parts of their environment.
Option B describes a population, and A and D only describe parts of an ecosystem (food chains and energy transfer), not the whole system.
✅ Answer: (C)
Option B describes a population, and A and D only describe parts of an ecosystem (food chains and energy transfer), not the whole system.
✅ Answer: (C)
▶️ Answer/Explanation
Removing trees means less carbon dioxide is absorbed by photosynthesis, so atmospheric carbon dioxide levels increase.
With fewer roots to hold soil together and take up water, rainfall runs off more quickly into rivers, increasing the risk of flooding.
✅ Answer: (D)
With fewer roots to hold soil together and take up water, rainfall runs off more quickly into rivers, increasing the risk of flooding.
✅ Answer: (D)
▶️ Answer/Explanation
For chromatography to work correctly, the spot of ink must be placed above the level of the solvent.
If the solvent covers the ink spot, the ink dissolves straight into the solvent rather than being carried up the paper.
Only diagram C shows the spot correctly positioned above the solvent surface.
✅ Answer: (C)
If the solvent covers the ink spot, the ink dissolves straight into the solvent rather than being carried up the paper.
Only diagram C shows the spot correctly positioned above the solvent surface.
✅ Answer: (C)
▶️ Answer/Explanation
An element is shown as particles of only one type (one colour/shape), while a compound is shown as particles containing two or more different atoms joined together.
A mixture of an element and a compound must show separate single-type particles alongside separate joined two-atom particles, not chemically combined.
Diagram B is the only one showing this combination correctly.
✅ Answer: (B)
A mixture of an element and a compound must show separate single-type particles alongside separate joined two-atom particles, not chemically combined.
Diagram B is the only one showing this combination correctly.
✅ Answer: (B)
▶️ Answer/Explanation
Isotopes are atoms of the same element, so by definition they have the same number of protons (same atomic number).
Isotopes differ in the number of neutrons in the nucleus, which changes their nucleon (mass) number.
Since the number of protons is unchanged, the number of electrons is also the same, ruling out B and C.
✅ Answer: (D)
Isotopes differ in the number of neutrons in the nucleus, which changes their nucleon (mass) number.
Since the number of protons is unchanged, the number of electrons is also the same, ruling out B and C.
✅ Answer: (D)
▶️ Answer/Explanation
The molar mass of \( C_9H_{20} \) is \( (9\times12)+(20\times1)=128 \text{ g/mol} \), so 64 g is \( \frac{64}{128}=0.5 \) mol of nonane.
From the equation, each mole of nonane needs 14 mol of \( O_2 \), so 0.5 mol needs \( 0.5\times14=7 \) mol of \( O_2 \).
Mass of oxygen \( = 7 \times 32 = 224 \text{ g} \) (using \( M_r(O_2)=32 \)).
✅ Answer: (B)
From the equation, each mole of nonane needs 14 mol of \( O_2 \), so 0.5 mol needs \( 0.5\times14=7 \) mol of \( O_2 \).
Mass of oxygen \( = 7 \times 32 = 224 \text{ g} \) (using \( M_r(O_2)=32 \)).
✅ Answer: (B)
▶️ Answer/Explanation
Positively charged aluminium ions, \( Al^{3+} \), are attracted to the negative cathode.
At the cathode each \( Al^{3+} \) ion gains three electrons: \( Al^{3+} + 3e^- \rightarrow Al \).
Gaining electrons is reduction, so this happens at the cathode, not the anode.
✅ Answer: (C)
At the cathode each \( Al^{3+} \) ion gains three electrons: \( Al^{3+} + 3e^- \rightarrow Al \).
Gaining electrons is reduction, so this happens at the cathode, not the anode.
✅ Answer: (C)
▶️ Answer/Explanation
A higher concentration means more acid particles are packed into the same volume, giving more frequent collisions and a faster rate — so A, C and D are all correct effects.
Concentration does not change the energy of individual particles; only a temperature increase does that.
So the statement that particles “have more energy” is the one that is not correct.
✅ Answer: (B)
Concentration does not change the energy of individual particles; only a temperature increase does that.
So the statement that particles “have more energy” is the one that is not correct.
✅ Answer: (B)
▶️ Answer/Explanation
Chlorine gas dissolves in the moisture on the litmus paper to form an acidic solution, which turns the blue litmus red.
Chlorine then bleaches the litmus paper, turning it white.
Ammonia turns damp red litmus blue (not blue litmus red), and CO₂ and oxygen do not bleach litmus at all.
✅ Answer: (C)
Chlorine then bleaches the litmus paper, turning it white.
Ammonia turns damp red litmus blue (not blue litmus red), and CO₂ and oxygen do not bleach litmus at all.
✅ Answer: (C)
▶️ Answer/Explanation
Going down Group I, the outer electron is further from the nucleus and more easily lost, so reactivity with water increases.
Melting points decrease down the group as the metallic bonding gets weaker with increasing atomic size.
✅ Answer: (B)
Melting points decrease down the group as the metallic bonding gets weaker with increasing atomic size.
✅ Answer: (B)
▶️ Answer/Explanation
Argon is a noble gas with a full outer shell of electrons, making it chemically unreactive.
This unreactivity means it does not react with the hot filament in a lamp, preventing it from burning out quickly.
✅ Answer: (D)
This unreactivity means it does not react with the hot filament in a lamp, preventing it from burning out quickly.
✅ Answer: (D)
▶️ Answer/Explanation
Metals more reactive than carbon, such as calcium, cannot be displaced from their ores by carbon reduction.
These very reactive metals must instead be extracted by electrolysis of their molten compounds.
Copper, iron and zinc are all less reactive than carbon and can be extracted by heating with carbon.
✅ Answer: (A)
These very reactive metals must instead be extracted by electrolysis of their molten compounds.
Copper, iron and zinc are all less reactive than carbon and can be extracted by heating with carbon.
✅ Answer: (A)
▶️ Answer/Explanation
The standard industrial conditions for the Haber process are a pressure of 250 atm, a temperature of 450°C, and an iron catalyst.
These conditions balance a reasonably fast rate of reaction with an acceptable equilibrium yield of ammonia.
✅ Answer: (A)
These conditions balance a reasonably fast rate of reaction with an acceptable equilibrium yield of ammonia.
✅ Answer: (A)
▶️ Answer/Explanation
In the Contact process, sulfur is first burned to form sulfur dioxide (reaction 1).
Sulfur trioxide is then dissolved in concentrated sulfuric acid (not water directly) to form oleum, which reacts with water — this is reaction 4, \( H_2SO_4 + SO_3 \rightarrow H_2S_2O_7 \).
Reactions 2 and 3 describe a different, non-standard route via sulfurous acid, which is not the industrial process.
✅ Answer: (B)
Sulfur trioxide is then dissolved in concentrated sulfuric acid (not water directly) to form oleum, which reacts with water — this is reaction 4, \( H_2SO_4 + SO_3 \rightarrow H_2S_2O_7 \).
Reactions 2 and 3 describe a different, non-standard route via sulfurous acid, which is not the industrial process.
✅ Answer: (B)
▶️ Answer/Explanation
But-1-ene has 4 carbon atoms with the C=C double bond starting at carbon 1.
This gives the structure \( CH_3CH_2CH{=}CH_2 \), with the double bond between the first and second carbons.
Option D is but-2-ene (double bond in the middle), and B is butane (no double bond).
✅ Answer: (C)
This gives the structure \( CH_3CH_2CH{=}CH_2 \), with the double bond between the first and second carbons.
Option D is but-2-ene (double bond in the middle), and B is butane (no double bond).
✅ Answer: (C)
▶️ Answer/Explanation
In addition polymerisation, the C=C double bond in each chloroethene monomer opens up to form a single bond.
Monomers then join end-to-end through these single bonds, keeping the chlorine atom attached to every other carbon.
The repeat unit must show single C–C bonds throughout the backbone with one Cl per carbon, which matches diagram A.
✅ Answer: (A)
Monomers then join end-to-end through these single bonds, keeping the chlorine atom attached to every other carbon.
The repeat unit must show single C–C bonds throughout the backbone with one Cl per carbon, which matches diagram A.
✅ Answer: (A)
▶️ Answer/Explanation
The gradient of a speed–time graph represents acceleration, and the curve is steep at first then flattens out over time.
A decreasing gradient means the acceleration is getting smaller as time goes on, even though the speed itself keeps increasing.
The gradient equals acceleration, not distance travelled (distance is the area under the graph), ruling out C.
✅ Answer: (B)
A decreasing gradient means the acceleration is getting smaller as time goes on, even though the speed itself keeps increasing.
The gradient equals acceleration, not distance travelled (distance is the area under the graph), ruling out C.
✅ Answer: (B)
▶️ Answer/Explanation
The extension of the spring is \( 25 – 15 = 10 \text{ cm} \) for a 20 N load, so extension is directly proportional to load, as Hooke’s Law requires.
This means the graph must be a straight line through the origin.
Only diagram D shows a straight line through the origin passing through the point (20, 10).
✅ Answer: (D)
This means the graph must be a straight line through the origin.
Only diagram D shows a straight line through the origin passing through the point (20, 10).
✅ Answer: (D)
▶️ Answer/Explanation
Work done is calculated as \( W = F \times d \), using only the force and the distance moved in the direction of the force.
\( W = 4.0 \text{ N} \times 8.0 \text{ m} = 32 \text{ J} \).
The time of 4.0 s given in the question is not needed for this calculation.
✅ Answer: (D)
\( W = 4.0 \text{ N} \times 8.0 \text{ m} = 32 \text{ J} \).
The time of 4.0 s given in the question is not needed for this calculation.
✅ Answer: (D)
▶️ Answer/Explanation
Total electrical energy input \( = 4000 + 12\,000 = 16\,000 \text{ J} \).
Efficiency \( = \dfrac{\text{useful energy output}}{\text{total energy input}} \times 100 = \dfrac{4000}{16\,000}\times100 \).
This gives an efficiency of 25%.
✅ Answer: (A)
Efficiency \( = \dfrac{\text{useful energy output}}{\text{total energy input}} \times 100 = \dfrac{4000}{16\,000}\times100 \).
This gives an efficiency of 25%.
✅ Answer: (A)
▶️ Answer/Explanation
Heating the gas gives the molecules more kinetic energy, so they move faster and hit the walls harder and more often.
Reducing the volume packs the same number of molecules into a smaller space, so they hit the walls more frequently, but each collision is no harder since their speed hasn’t changed.
✅ Answer: (B)
Reducing the volume packs the same number of molecules into a smaller space, so they hit the walls more frequently, but each collision is no harder since their speed hasn’t changed.
✅ Answer: (B)
▶️ Answer/Explanation
Metals contain free (delocalised) electrons that can move freely through the metal lattice.
These electrons gain kinetic energy at the hot end and transfer it quickly through the metal by colliding with other electrons and ions.
Non-metals lack these free electrons, so they can only transfer energy by slower atomic vibrations.
✅ Answer: (C)
These electrons gain kinetic energy at the hot end and transfer it quickly through the metal by colliding with other electrons and ions.
Non-metals lack these free electrons, so they can only transfer energy by slower atomic vibrations.
✅ Answer: (C)
▶️ Answer/Explanation
As the car moves further away, less sound energy reaches the observer, so the amplitude (loudness) decreases.
Because the source is moving away, the sound waves are stretched out, giving a lower frequency (the Doppler effect), which is heard as a lower pitch.
✅ Answer: (A)
Because the source is moving away, the sound waves are stretched out, giving a lower frequency (the Doppler effect), which is heard as a lower pitch.
✅ Answer: (A)
▶️ Answer/Explanation
The rod is attracted no matter which pole of the magnet faces it, so it cannot itself be a permanent magnet (a magnet would be repelled by one pole).
This rules out A, and it must instead be a magnetic material such as iron, which is always attracted to either pole.
Aluminium and copper are not magnetic materials, so they would not be attracted at all.
✅ Answer: (D)
This rules out A, and it must instead be a magnetic material such as iron, which is always attracted to either pole.
Aluminium and copper are not magnetic materials, so they would not be attracted at all.
✅ Answer: (D)
▶️ Answer/Explanation
Resistance is calculated using \( R = \dfrac{V}{I} \) for each row.
For row D: \( R = \dfrac{8.0}{4.0} = 2.0\ \Omega \), which matches.
Checking the others: A gives 0.5 Ω, B gives 0.5 Ω, and C gives 0.5 Ω, so only D gives 2.0 Ω.
✅ Answer: (D)
For row D: \( R = \dfrac{8.0}{4.0} = 2.0\ \Omega \), which matches.
Checking the others: A gives 0.5 Ω, B gives 0.5 Ω, and C gives 0.5 Ω, so only D gives 2.0 Ω.
✅ Answer: (D)
▶️ Answer/Explanation
In parallel, each lamp gets the full battery voltage, stays lit independently if the other breaks, and can be switched individually — so A, B and C are genuine benefits.
However, in parallel the total current drawn from the battery is actually larger (it’s the sum of the branch currents), not smaller.
So “smaller current in the battery” is not a real benefit of parallel connection.
✅ Answer: (D)
However, in parallel the total current drawn from the battery is actually larger (it’s the sum of the branch currents), not smaller.
So “smaller current in the battery” is not a real benefit of parallel connection.
✅ 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 and appliance from damage or fire caused by excessive current, such as from a fault.
A fuse does not regulate current or voltage to a constant value — it simply disconnects the circuit when overloaded.
✅ Answer: (B)
This protects the circuit and appliance from damage or fire caused by excessive current, such as from a fault.
A fuse does not regulate current or voltage to a constant value — it simply disconnects the circuit when overloaded.
✅ Answer: (B)
▶️ Answer/Explanation
Using Fleming’s left-hand rule, with the thumb (force) pointing up and the second finger (current) in the given direction, the First finger (field) must point from P to Q.
This orientation of the three mutually perpendicular directions is what produces an upward force on the wire.
✅ Answer: (A)
This orientation of the three mutually perpendicular directions is what produces an upward force on the wire.
✅ Answer: (A)
▶️ Answer/Explanation
Beta particles are negatively charged, so they are attracted towards the positive plate and deflected in that direction.
Gamma rays have no charge and no mass in the usual sense, so they pass straight through an electric field undeflected.
✅ Answer: (C)
Gamma rays have no charge and no mass in the usual sense, so they pass straight through an electric field undeflected.
✅ Answer: (C)