Question 1 (Sub-topic B1.1)
What is respiration?
A. breakdown of food by enzymes in the alimentary canal
B. breathing to supply oxygen to cells
C. release of carbon dioxide from the lungs
D. release of energy for body activities
▶️Answer/Explanation
Answer: D
Explanation: Respiration is the process by which cells break down glucose to release energy for body activities. This process occurs in the mitochondria of cells and is essential for all living organisms to function.
Question 2 (Sub-topic B3.1)
What is the effect of increasing the concentration gradient on the rate of diffusion?
▶️Answer/Explanation
Answer: A
Explanation: Increasing the concentration gradient increases the rate of diffusion because there is a greater difference in concentration between two areas, leading to faster movement of particles from an area of high concentration to an area of low concentration.
Question 3 (Sub-topic B4.1)
Three food tests are carried out on a sample of food. The results are shown in the table:
| Food Test | Final Colour |
|---|---|
| Benedict’s | blue |
| Biuret | blue |
| Iodine | blue-black |
From these results, which nutrient is in the food?
A. reducing sugar
B. protein
C. starch
D. vitamin C
▶️Answer/Explanation
Answer: C
Explanation: The iodine test turning blue-black indicates the presence of starch. Benedict’s test remaining blue suggests no reducing sugars, and the Biuret test remaining blue suggests no proteins.
Question 4 (Sub-topic B5.1)
What is an enzyme?
A. a carbohydrate that speeds up the rate of a reaction
B. a carbohydrate that alters the activity of a target organ
C. a protein that alters the activity of a target organ
D. a protein that speeds up the rate of a reaction
▶️Answer/Explanation
Answer: D
Explanation: Enzymes are biological catalysts made of proteins that speed up chemical reactions in the body without being consumed in the process.
Question 5 (Sub-topic B6.1)
The balanced equation for photosynthesis is shown:
What is X?
A. C6H12O6
B. C6H12O12
C. C12H6O6
D. C12H12O2
▶️Answer/Explanation
Answer: A
Explanation: The balanced equation for photosynthesis is 6CO2 + 6H2O → C6H12O6 + 6O2. Therefore, X is glucose (C6H12O6).
Question 6 (Sub-topic B7.3)
Protein shakes can be used by athletes to supplement their diet. They are a drink made by dissolving protein powders in water or milk. Which types of digestion will be required before they can be absorbed?
| Chemical Digestion | Mechanical Digestion |
|---|---|
| A. ✓ | ✓ |
| B. ✓ | ✗ |
| C. ✗ | ✓ |
| D. ✗ | ✗ |
▶️Answer/Explanation
Answer: B
Explanation: Protein shakes are already in liquid form, so mechanical digestion (chewing) is not required. However, chemical digestion (breaking down proteins into amino acids) is necessary for absorption.
Question 7 (Sub-topic B8.3)
A student investigates the effect of humidity on transpiration rate.
A plant is placed on a balance as shown for one hour. The mass of the plant decreases.
The student repeats the experiment in air of higher humidity.
What is the effect of increasing humidity?
A. larger decrease in mass due to a steeper diffusion gradient of water
B. larger decrease in mass due to a less steep diffusion gradient of water
C. smaller decrease in mass due to a steeper diffusion gradient of water
D. smaller decrease in mass due to a less steep diffusion gradient of water
▶️Answer/Explanation
Answer: D
Explanation: Increasing humidity reduces the rate of transpiration because the diffusion gradient of water between the leaf and the surrounding air is less steep. This results in a smaller decrease in the mass of the plant.
Question 8 (Sub-topic B11.1)
A child blows into a rubber balloon. What is the percentage of oxygen inside the balloon?
A. 0%
B. 4%
C. 16%
D. 21%
▶️Answer/Explanation
Answer: C
Explanation: When a person exhales, the percentage of oxygen in the breath is around 16%, as some oxygen is absorbed by the body during respiration.
Question 9 (Sub-topic B13.3)
What is homeostasis?
A. keeping internal conditions constant
B. keeping the body at the same temperature as the environment
C. sweating to keep the body warm
D. vasoconstriction of arterioles to increase heat loss
▶️Answer/Explanation
Answer: A
Explanation: Homeostasis is the process by which the body maintains a stable internal environment, such as constant temperature, pH, and glucose levels, despite changes in external conditions.
Question 10 (Sub-topic B15.1)
Which row about these human cells is correct?
| Type of Human Cell | Chromosome Number | Description |
|---|---|---|
| A. gamete | 23 | diploid |
| B. gamete | 46 | haploid |
| C. zygote | 46 | diploid |
| D. zygote | 23 | haploid |
▶️Answer/Explanation
Answer: C
Explanation: A zygote is formed by the fusion of two haploid gametes (each with 23 chromosomes), resulting in a diploid cell with 46 chromosomes.
Question 11 (Sub-topic B16.1)
The allele for long fur in cats is recessive to the allele for short fur. The pedigree diagram shows the inheritance of long and short fur in a family of cats.
How many cats in the pedigree diagram are heterozygous for fur length?
A. 2
B. 4
C. 5
D. 6
▶️Answer/Explanation
Answer: D
Explanation: Heterozygous individuals carry one dominant and one recessive allele. In the pedigree diagram, 6 cats are heterozygous for fur length, as they have one allele for short fur (dominant) and one for long fur (recessive).
Question 12 (Sub-topic B18.2)
Why do food chains usually have fewer than five trophic levels?
A. All the carnivores consume herbivores.
B. The energy passed on reduces from one trophic level to the next.
C. There is less protein in each individual higher up the chain.
D. There is only one producer in each chain.
▶️Answer/Explanation
Answer: B
Explanation: Energy is lost at each trophic level through processes like respiration, movement, and heat loss. As a result, there is less energy available for organisms at higher trophic levels, limiting the number of trophic levels in a food chain.
Question 13 (Sub-topic B19.1)
What decreases as a result of deforestation?
A. available habitats
B. atmospheric carbon dioxide
C. flooding
D. soil loss
▶️Answer/Explanation
Answer: A
Explanation: Deforestation leads to the destruction of habitats for many species, reducing the availability of habitats. It also increases atmospheric carbon dioxide, flooding, and soil loss, but the question asks for what decreases.
Question 14 (Sub-topic C2.1)
The structures of some substances are shown:
Which row shows the total number of different elements and the total number of atoms in the three structures?
| Total Number of Different Elements | Total Number of Atoms |
|---|---|
| A. 3 | 9 |
| B. 3 | 17 |
| C. 7 | 9 |
| D. 7 | 17 |
▶️Answer/Explanation
Answer: B
Explanation: The three substances contain 3 different elements (H, C, O) and a total of 17 atoms (2 in H2O, 9 in C2H6O, and 5 in CH4).
Question 15 (Sub-topic C3.1)
Pure substance X has a melting point of 110°C. The melting point ranges of four impure samples of substance X are measured. What is the melting point range of the most impure sample of substance X?
| Melting Point/°C |
|---|
| A. 81–85 |
| B. 86–92 |
| C. 98–99 |
| D. 102–110 |
▶️Answer/Explanation
Answer: A
Explanation: Impurities lower and broaden the melting point range of a substance. The most impure sample will have the lowest and broadest melting point range, which is 81–85°C.
Question 16 (Sub-topic C2.5)
Which row explains why the melting points of covalent compounds are lower than those of ionic compounds?
| Covalent Compound | Ionic Compound |
|---|---|
| A. strong attractive forces between molecules | strong attraction between oppositely charged ions |
| B. strong attractive forces between molecules | weak attraction between oppositely charged ions |
| C. weak attractive forces between molecules | strong attraction between oppositely charged ions |
| D. weak attractive forces between molecules | weak attraction between oppositely charged ions |
▶️Answer/Explanation
Answer: C
Explanation: Covalent compounds have weak intermolecular forces, which require less energy to overcome, resulting in lower melting points. Ionic compounds have strong electrostatic forces between oppositely charged ions, requiring more energy to break, resulting in higher melting points.
Question 17 (Sub-topic C2.4)
The charges on some ions are shown:
| Positive Ions | Negative Ions |
|---|---|
| Al3+ | N3- |
| Li+ | NO3– |
| Mg2+ | O2- |
| Zn2+ | SO42- |
Which formula is correct?
A. aluminium sulfate – Al2(SO4)3
B. lithium nitrate – Li2NO3
C. magnesium nitride – Mg2N3
D. zinc oxide – ZnO2
▶️Answer/Explanation
Answer: A
Explanation: The correct formula for aluminium sulfate is Al2(SO4)3, as it balances the charges of Al3+ and SO42- ions.
Question 18 (Sub-topic C5.1)
An energy level diagram for a chemical reaction is shown.
Which row describes the energy change and the type of reaction?
| Energy Change | Type of Reaction |
|---|---|
| A. energy is given out to the surroundings | endothermic |
| B. energy is given out to the surroundings | exothermic |
| C. energy is taken in from the surroundings | endothermic |
| D. energy is taken in from the surroundings | exothermic |
▶️Answer/Explanation
Answer: C
Explanation: If energy is taken in from the surroundings, the reaction is endothermic. This means the products have more energy than the reactants.
Question 19 (Sub-topic C6.3)
Which equation represents a redox reaction?
A. Ca(OH)2 + CO2 → CaCO3 + H2O
B. CuCO3 → CuO + CO2
C. Mg + CuSO4 → MgSO4 + Cu
D. Pb(NO3)2 + 2KI → PbI2 + 2KNO3
▶️Answer/Explanation
Answer: C
Explanation: A redox reaction involves both oxidation and reduction. In the reaction Mg + CuSO4 → MgSO4 + Cu, magnesium is oxidized (loses electrons) and copper is reduced (gains electrons).
Question 20 (Sub-topic C7.1)
What reacts with ammonia gas?
| Hydrochloric Acid | Sodium Hydroxide |
|---|---|
| A. ✓ | ✓ |
| B. ✓ | ✗ |
| C. ✗ | ✓ |
| D. ✗ | ✗ |
▶️Answer/Explanation
Answer: B
Explanation: Ammonia gas reacts with hydrochloric acid to form ammonium chloride, but it does not react with sodium hydroxide.
Question 21 (Sub-topic C9.1)
Substance Q is added to cold water. It floats on the water and hydrogen gas is made. What is Q?
A. iodine
B. lithium
C. magnesium
D. zinc
▶️Answer/Explanation
Answer: B
Explanation: Lithium is a highly reactive metal that reacts with cold water to produce hydrogen gas. It is also less dense than water, so it floats.
Question 22 (Sub-topic C9.4)
Four metals W, X, Y and Z are added to different solutions of metal nitrates. The results are shown:
Which statements are correct?
1. Metal Z is the most reactive.
2. Metal W has the lowest tendency to form positive ions.
3. Metal X is less reactive than metal W.
4. Metal Y is more reactive than metal X.
A. 1 and 2
B. 1 and 4
C. 2 and 3
D. 3 and 4
▶️Answer/Explanation
Answer: A
Explanation: Metal Z reacts with all the metal nitrate solutions, indicating it is the most reactive. Metal W does not react with any solution, indicating it has the lowest tendency to form positive ions.
Question 23 (Sub-topic C10.2)
Which statement explains how oxides of nitrogen are formed in a car engine?
A. Nitrogen from the air reacts with the fuel.
B. Oxygen and nitrogen from the air react together.
C. Oxygen from the air reacts with sulfur impurities in the fuel.
D. Oxygen from the air reacts with the fuel.
▶️Answer/Explanation
Answer: B
Explanation: Oxides of nitrogen (NOx) are formed in car engines when nitrogen and oxygen from the air react at high temperatures during combustion.
Question 24 (Sub-topic C10.2)
Other than hydrogen and oxygen, which substance provides only one of the essential elements for plant growth?
A. K3PO4
B. KNO3
C. (NH4)3PO4
D. NH4NO3
▶️Answer/Explanation
Answer: D
Explanation: NH4NO3 provides only nitrogen (N) as an essential element for plant growth, whereas the other options provide multiple elements (e.g., K, P, N).
Question 25 (Sub-topic C7.3)
What is the chemical name for lime?
A. calcium carbonate
B. calcium hydroxide
C. calcium oxide
D. calcium sulfate
▶️Answer/Explanation
Answer: C
Explanation: Lime is the common name for calcium oxide (CaO).
Question 26 (Sub-topic C6.2)
Which row about the Contact process is correct?
| Temperature/°C | Catalyst |
|---|---|
| A. 200 | iron |
| B. 200 | vanadium(V) oxide |
| C. 450 | iron |
| D. 450 | vanadium(V) oxide |
▶️Answer/Explanation
Answer: D
Explanation: The Contact process for the production of sulfuric acid uses a temperature of around 450°C and vanadium(V) oxide as the catalyst.
Question 27 (Sub-topic C11.3)
Which reaction produces only one product?
A. combustion of ethanol
B. cracking of alkanes
C. fermentation of sugar solution
D. reaction of ethene and steam
▶️Answer/Explanation
Answer: D
Explanation: The reaction of ethene and steam produces only one product, ethanol (C2H5OH).
Question 28 (Sub-topic P1.2)
A car accelerates with constant acceleration from a speed of 3.0 m/s to a speed of 9.0 m/s in 3.0 s. What is the acceleration of the car?
A. 1.0 m/s2
B. 2.0 m/s2
C. 3.0 m/s2
D. 4.0 m/s2
▶️Answer/Explanation
Answer: B
Explanation: Acceleration is calculated using the formula \( a = \frac{\Delta v}{\Delta t} \). Here, \( \Delta v = 9.0 – 3.0 = 6.0 \, \text{m/s} \) and \( \Delta t = 3.0 \, \text{s} \). Therefore, \( a = \frac{6.0}{3.0} = 2.0 \, \text{m/s}^2 \).
Question 29 (Sub-topic P1.5)
Which two quantities can be used to calculate the acceleration of a rocket?
A. the mass of the rocket and its speed
B. the mass of the rocket and its weight
C. the resultant force on the rocket and its mass
D. the resultant force on the rocket and its speed
▶️Answer/Explanation
Answer: C
Explanation: According to Newton’s second law, \( F = ma \), so acceleration (\( a \)) can be calculated using the resultant force (\( F \)) and the mass (\( m \)) of the rocket.
Question 30 (Sub-topic P1.5)
Which statement applies to a system in equilibrium?
A. There is a resultant force and there is a resultant turning effect on the system.
B. There is a resultant force but there is no resultant turning effect on the system.
C. There is no resultant force but there is a resultant turning effect on the system.
D. There is no resultant force and there is no resultant turning effect on the system.
▶️Answer/Explanation
Answer: D
Explanation: In equilibrium, there is no resultant force and no resultant turning effect (moment) acting on the system.
Question 31 (Sub-topic P1.6)
The diagram shows a man diving into water.
Which form of energy is increasing as he accelerates downwards through the air?
A. chemical
B. elastic potential (strain)
C. gravitational potential
D. kinetic
▶️Answer/Explanation
Answer: D
Explanation: As the man accelerates downwards, his speed increases, which means his kinetic energy is increasing.
Question 32 (Sub-topic P1.6)
The Sun is an important energy resource. Which energy source powers the Sun?
A. chemical
B. geothermal
C. nuclear fission
D. nuclear fusion
▶️Answer/Explanation
Answer: D
Explanation: The Sun’s energy is produced by nuclear fusion, where hydrogen nuclei combine to form helium, releasing vast amounts of energy.
Question 33 (Sub-topic P2.3)
Which example of thermal conduction involves energy transfer by electrons?
A. A person’s feet become warm when walking on hot sand.
B. Chocolate becomes warm if it is held in a hand.
C. One end of a metal spoon becomes hot when the other end is placed in hot water.
D. The outside of a plastic mug filled with hot water becomes hot.
▶️Answer/Explanation
Answer: C
Explanation: In metals, thermal conduction occurs primarily through the movement of free electrons. When one end of a metal spoon is heated, electrons transfer energy to the other end.
Question 34 (Sub-topic P2.3)
Which colour of outer clothing helps to keep the wearer cool on a hot, sunny day, and why is this clothing effective?
| Colour of Clothing | Why It Is Effective |
|---|---|
| A. black | it is a good absorber of radiation from the Sun |
| B. black | it is a poor absorber of radiation from the Sun |
| C. white | it is a good absorber of radiation from the Sun |
| D. white | it is a poor absorber of radiation from the Sun |
▶️Answer/Explanation
Answer: D
Explanation: White clothing reflects most of the Sun’s radiation, making it a poor absorber of heat. This helps keep the wearer cool on a hot, sunny day.
Question 35 (Sub-topic P3.2)
The diagram represents the surface of a transparent liquid. Two rays of light are travelling in the liquid. They both reach the surface. The path of each ray is shown.
What is the critical angle for this liquid?
A. 35°
B. 40°
C. 50°
D. 55°
▶️Answer/Explanation
Answer: A
Explanation: The critical angle is the angle of incidence in the denser medium (liquid) at which the angle of refraction in the less dense medium (air) is 90°. In this case, the critical angle is 35°.
Question 36 (Sub-topic P4.1)
An unmagnetised soft iron bar is held close to a permanent magnet and becomes attached to the magnet. The soft iron bar is then moved a large distance from the magnet.
What happens at point X when the soft iron bar is attached to the magnet, and what happens when the bar is moved a large distance from the magnet?
| Attached to Magnet | Bar Moved Away |
|---|---|
| A. X becomes an N pole | no pole at X |
| B. X becomes an N pole | remains an N pole |
| C. X becomes an S pole | no pole at X |
| D. X becomes an S pole | remains an S pole |
▶️Answer/Explanation
Answer: A
Explanation: When the soft iron bar is attached to the magnet, it becomes temporarily magnetised, and point X becomes an N pole. When the bar is moved away, it loses its magnetism, and there is no pole at X.
Question 37 (Sub-topic P4.3)
Which combination of resistors has a combined resistance of 2.0 Ω?
▶️Answer/Explanation
Answer: D
Explanation: The combined resistance of resistors in parallel is calculated using \( \frac{1}{R} = \frac{1}{R_1} + \frac{1}{R_2} \). For 2.0 Ω and 1.0 Ω in parallel, \( \frac{1}{R} = \frac{1}{2} + \frac{1}{1} = 1.5 \), so \( R = \frac{1}{1.5} = 0.67 \, \Omega \). However, the closest option is D, which is 2.0 Ω and 1.0 Ω in parallel, giving a combined resistance of 0.67 Ω, which is not 2.0 Ω. This suggests there may be an error in the question or options.
Question 38 (Sub-topic P4.4)
A student connects the circuit shown.
When the switch is closed, the fuse blows and stops the current.
What is a possible reason for this?
A. The current rating of the fuse is too high.
B. The current is too large.
C. The lamp is too dim.
D. The voltage is too small.
▶️Answer/Explanation
Answer: B
Explanation: If the current in the circuit exceeds the fuse’s rating, the fuse will blow to protect the circuit. This indicates that the current is too large.
Question 39 (Sub-topic P4.5)
The diagrams each show a wire carrying a current in the direction of the arrow. Which diagram shows the pattern and the direction of the magnetic field around the wire?
▶️Answer/Explanation
Answer: C
Explanation: The magnetic field around a current-carrying wire forms concentric circles, and the direction of the field can be determined using the right-hand rule. Diagram C correctly shows this pattern and direction.
Question 40 (Sub-topic P5.2)
A radioactive nucleus emits a β-particle. What happens to the proton number (atomic number) of the nucleus?
A. It stays the same.
B. It increases by 1.
C. It decreases by 2.
D. It decreases by 4.
▶️Answer/Explanation
Answer: B
Explanation: When a β-particle (an electron) is emitted, a neutron in the nucleus is converted into a proton. This increases the proton number (atomic number) by 1.