▶️ Answer/Explanation
Respiration is defined as the chemical reactions occurring inside living cells.
These reactions break down nutrient molecules (such as glucose) to release energy.
This released energy is used for metabolism, i.e. all the chemical processes needed to keep the organism alive.
✅ Answer: (D)
These reactions break down nutrient molecules (such as glucose) to release energy.
This released energy is used for metabolism, i.e. all the chemical processes needed to keep the organism alive.
✅ Answer: (D)
▶️ Answer/Explanation
The magnification formula is \( \text{magnification} = \frac{\text{image size}}{\text{actual size}} \).
Rearranging gives \( \text{actual size} = \frac{\text{image size}}{\text{magnification}} \).
Substituting values: \( \frac{45}{1000} = 0.045 \) mm.
✅ Answer: (D)
Rearranging gives \( \text{actual size} = \frac{\text{image size}}{\text{magnification}} \).
Substituting values: \( \frac{45}{1000} = 0.045 \) mm.
✅ Answer: (D)
▶️ Answer/Explanation
Linoleic acid is a fatty acid, and fatty acids are one of the two building blocks of lipids.
Lipids form when fatty acids combine chemically with glycerol through a condensation reaction: \( \text{glycerol} + 3\,\text{fatty acid} \rightarrow \text{lipid} + 3\,\text{H}_2\text{O} \).
Oils are simply lipids that are liquid at room temperature, so oil is the larger molecule that may contain linoleic acid.
✅ Answer: (B)
Lipids form when fatty acids combine chemically with glycerol through a condensation reaction: \( \text{glycerol} + 3\,\text{fatty acid} \rightarrow \text{lipid} + 3\,\text{H}_2\text{O} \).
Oils are simply lipids that are liquid at room temperature, so oil is the larger molecule that may contain linoleic acid.
✅ Answer: (B)
▶️ Answer/Explanation
Enzymes are biological catalysts made of protein.
Their protein structure gives them a specific 3D active site that binds only to a complementary substrate molecule.
✅ Answer: (D)
Their protein structure gives them a specific 3D active site that binds only to a complementary substrate molecule.
✅ Answer: (D)
▶️ Answer/Explanation
Photosynthesis is summarised as \( 6CO_2 + 6H_2O \xrightarrow{\text{light}} C_6H_{12}O_6 + 6O_2 \).
This means carbon dioxide must move from the air into the plant, and oxygen must move from the plant into the air.
Arrows 1 (CO₂ in) and 4 (O₂ out) represent this exchange.
✅ Answer: (B)
This means carbon dioxide must move from the air into the plant, and oxygen must move from the plant into the air.
Arrows 1 (CO₂ in) and 4 (O₂ out) represent this exchange.
✅ Answer: (B)
▶️ Answer/Explanation
A low red blood cell count suggests a shortage of iron, since iron is needed to make haemoglobin.
Constipation suggests a shortage of fibre, since fibre adds bulk to help food move through the gut.
Row C shows iron and fibre as the deficient components.
✅ Answer: (C)
Constipation suggests a shortage of fibre, since fibre adds bulk to help food move through the gut.
Row C shows iron and fibre as the deficient components.
✅ Answer: (C)
▶️ Answer/Explanation
Blood from the vena cava travels to the lungs via the pulmonary artery to become oxygenated.
It returns via the pulmonary vein to the heart, then leaves through the aorta.
From the aorta, oxygenated blood reaches the kidney via the renal artery.
✅ Answer: (A)
It returns via the pulmonary vein to the heart, then leaves through the aorta.
From the aorta, oxygenated blood reaches the kidney via the renal artery.
✅ Answer: (A)
▶️ Answer/Explanation
The trachea splits into two bronchi, which divide further into smaller bronchioles.
Bronchioles end in tiny air sacs called alveoli, where gas exchange takes place.
In the diagram, only the alveoli and the trachea are correctly labelled.
✅ Answer: (B)
Bronchioles end in tiny air sacs called alveoli, where gas exchange takes place.
In the diagram, only the alveoli and the trachea are correctly labelled.
✅ Answer: (B)
▶️ Answer/Explanation
Adrenaline is the “fight or flight” hormone released in response to stress or danger.
It increases breathing rate and pulse rate to deliver more oxygen and glucose to the muscles.
It also widens the pupils to improve vision in an emergency.
✅ Answer: (D)
It increases breathing rate and pulse rate to deliver more oxygen and glucose to the muscles.
It also widens the pupils to improve vision in an emergency.
✅ Answer: (D)
▶️ Answer/Explanation
Asexual reproduction involves only one parent and no fusion of gametes.
Because there is no mixing of genetic material from two parents, the offspring are genetically identical to the parent (clones).
✅ Answer: (A)
Because there is no mixing of genetic material from two parents, the offspring are genetically identical to the parent (clones).
✅ Answer: (A)
▶️ Answer/Explanation
Sperm can carry either an X or a Y chromosome, while all eggs carry an X chromosome.
A male offspring \( (XY) \) results from an X-egg combining with a Y-sperm, while a female offspring \( (XX) \) results from an X-egg combining with an X-sperm.
Row B shows the correct sperm-egg combinations for each.
✅ Answer: (B)
A male offspring \( (XY) \) results from an X-egg combining with a Y-sperm, while a female offspring \( (XX) \) results from an X-egg combining with an X-sperm.
Row B shows the correct sperm-egg combinations for each.
✅ Answer: (B)
▶️ Answer/Explanation
Herbivores are animals that only eat plant material as their source of food.
Since they consume plants directly, they obtain all their energy solely by eating plants.
✅ Answer: (C)
Since they consume plants directly, they obtain all their energy solely by eating plants.
✅ Answer: (C)
▶️ Answer/Explanation
The graph shows atmospheric CO₂ steadily increasing over the years.
Photosynthesis removes CO₂ from the atmosphere: \( 6CO_2 + 6H_2O \xrightarrow{\text{light}} C_6H_{12}O_6 + 6O_2 \).
A reduction in photosynthesis (e.g. through deforestation) means less CO₂ is removed, explaining the rising trend.
✅ Answer: (C)
Photosynthesis removes CO₂ from the atmosphere: \( 6CO_2 + 6H_2O \xrightarrow{\text{light}} C_6H_{12}O_6 + 6O_2 \).
A reduction in photosynthesis (e.g. through deforestation) means less CO₂ is removed, explaining the rising trend.
✅ Answer: (C)
▶️ Answer/Explanation
Filtration is used first to remove the insoluble impurity from the salt solution.
The filtrate (pure salt solution) is then evaporated/crystallised to obtain pure salt crystals.
✅ Answer: (C)
The filtrate (pure salt solution) is then evaporated/crystallised to obtain pure salt crystals.
✅ Answer: (C)
▶️ Answer/Explanation
The formula \( P_4O_{10} \) shows one unit containing 4 phosphorus atoms and 10 oxygen atoms chemically bonded together.
Since phosphorus and oxygen are different elements joined by covalent bonds, this represents a single molecule of a compound.
✅ Answer: (C)
Since phosphorus and oxygen are different elements joined by covalent bonds, this represents a single molecule of a compound.
✅ Answer: (C)
▶️ Answer/Explanation
The nucleon number (mass number) equals the sum of protons and neutrons: \( A = Z + N \).
For a neutral atom, the number of electrons always equals the number of protons.
Row B (12 protons, 12 neutrons, 12 electrons) gives \( 12+12 = 24 \), matching a neutral magnesium atom.
✅ Answer: (B)
For a neutral atom, the number of electrons always equals the number of protons.
Row B (12 protons, 12 neutrons, 12 electrons) gives \( 12+12 = 24 \), matching a neutral magnesium atom.
✅ Answer: (B)
▶️ Answer/Explanation
Lithium (Group I) forms an ion with a single positive charge: \( Li^+ \).
Bromine (Group VII) forms an ion with a single negative charge: \( Br^- \).
Since the charges are equal and opposite, they combine in a 1:1 ratio to give the formula LiBr.
✅ Answer: (A)
Bromine (Group VII) forms an ion with a single negative charge: \( Br^- \).
Since the charges are equal and opposite, they combine in a 1:1 ratio to give the formula LiBr.
✅ Answer: (A)
▶️ Answer/Explanation
To electroplate nickel with copper, the nickel object must be the negative electrode (cathode) and copper the positive electrode (anode).
The electrolyte must be aqueous copper chloride, not molten, so that copper ions are free to move and be deposited onto the cathode.
Diagram D shows copper as the anode and nickel as the cathode in an aqueous solution.
✅ Answer: (D)
The electrolyte must be aqueous copper chloride, not molten, so that copper ions are free to move and be deposited onto the cathode.
Diagram D shows copper as the anode and nickel as the cathode in an aqueous solution.
✅ Answer: (D)
▶️ Answer/Explanation
An endothermic reaction takes in heat energy from the surroundings.
This heat energy is absorbed by the reactants to break bonds, which is why the temperature of the mixture actually decreases.
✅ Answer: (A)
This heat energy is absorbed by the reactants to break bonds, which is why the temperature of the mixture actually decreases.
✅ Answer: (A)
▶️ Answer/Explanation
Oxidation is defined as a reaction in which oxygen is gained.
When methane burns: \( CH_4 + 2O_2 \rightarrow CO_2 + 2H_2O \), carbon and hydrogen atoms gain oxygen atoms to form the products.
Since the products are water and carbon dioxide, this confirms oxygen has been gained by methane.
✅ Answer: (B)
When methane burns: \( CH_4 + 2O_2 \rightarrow CO_2 + 2H_2O \), carbon and hydrogen atoms gain oxygen atoms to form the products.
Since the products are water and carbon dioxide, this confirms oxygen has been gained by methane.
✅ Answer: (B)
▶️ Answer/Explanation
Filtration is used first to remove the excess, unreacted insoluble magnesium oxide from the mixture.
The remaining magnesium chloride solution is then evaporated to concentrate it, allowing crystals to form on cooling.
✅ Answer: (B)
The remaining magnesium chloride solution is then evaporated to concentrate it, allowing crystals to form on cooling.
✅ Answer: (B)
▶️ Answer/Explanation
Transition metals typically have high melting points due to strong metallic bonding.
They commonly act as catalysts in industrial reactions, such as iron in the Haber process.
They also form coloured compounds because of their variable oxidation states.
✅ Answer: (D)
They commonly act as catalysts in industrial reactions, such as iron in the Haber process.
They also form coloured compounds because of their variable oxidation states.
✅ Answer: (D)
▶️ Answer/Explanation
Anhydrous cobalt(II) chloride is blue when dry but turns pink when water is added.
This colour change is a reliable chemical test that specifically confirms the presence of water, unlike a physical test such as measuring the boiling point.
✅ Answer: (A)
This colour change is a reliable chemical test that specifically confirms the presence of water, unlike a physical test such as measuring the boiling point.
✅ Answer: (A)
▶️ Answer/Explanation
Sulfur is a non-metallic element, found in Group VI (not VII) of the Periodic Table.
It is a key raw material used industrially to manufacture sulfuric acid, \( H_2SO_4 \), via the Contact Process.
✅ Answer: (B)
It is a key raw material used industrially to manufacture sulfuric acid, \( H_2SO_4 \), via the Contact Process.
✅ Answer: (B)
▶️ Answer/Explanation
Limestone’s main constituent is calcium carbonate, \( CaCO_3 \), not calcium oxide, so statement 1 is incorrect.
Limestone is heated to manufacture lime (calcium oxide), which also releases carbon dioxide: \( CaCO_3 \rightarrow CaO + CO_2 \).
Statements 2 and 3 correctly describe this thermal decomposition process.
✅ Answer: (C)
Limestone is heated to manufacture lime (calcium oxide), which also releases carbon dioxide: \( CaCO_3 \rightarrow CaO + CO_2 \).
Statements 2 and 3 correctly describe this thermal decomposition process.
✅ Answer: (C)
▶️ Answer/Explanation
In a fractionating column, fractions with lower boiling points (like refinery gas) collect at the top, while those with higher boiling points (like bitumen) collect at the bottom.
Naphtha is used to make chemicals and is collected below gasoline, while refinery gas is used for heating/cooking and is collected at the top of the column.
Rows 3 and 4 correctly describe these two fractions.
✅ Answer: (D)
Naphtha is used to make chemicals and is collected below gasoline, while refinery gas is used for heating/cooking and is collected at the top of the column.
Rows 3 and 4 correctly describe these two fractions.
✅ Answer: (D)
▶️ Answer/Explanation
Fermentation is the process in which yeast breaks down sugar into ethanol and carbon dioxide: \( C_6H_{12}O_6 \rightarrow 2C_2H_5OH + 2CO_2 \).
This biological process is the standard method used to produce ethanol.
✅ Answer: (D)
This biological process is the standard method used to produce ethanol.
✅ Answer: (D)
▶️ Answer/Explanation
Distance travelled equals the area under a speed-time graph.
The graph shows a trapezium shape between 2.0 m/s and 8.0 m/s over 10 s.
Area \( = \frac{1}{2}(2.0+8.0)\times10 = 50 \) m.
✅ Answer: (C)
The graph shows a trapezium shape between 2.0 m/s and 8.0 m/s over 10 s.
Area \( = \frac{1}{2}(2.0+8.0)\times10 = 50 \) m.
✅ Answer: (C)
▶️ Answer/Explanation
Weight is a force, so it is measured in newtons (N), following \( \text{weight} = mg \).
Since \( g = \frac{\text{weight}}{\text{mass}} \), the units of \( g \) must be \( N/kg \).
Row D correctly shows N for weight and N/kg for \( g \).
✅ Answer: (D)
Since \( g = \frac{\text{weight}}{\text{mass}} \), the units of \( g \) must be \( N/kg \).
Row D correctly shows N for weight and N/kg for \( g \).
✅ Answer: (D)
▶️ Answer/Explanation
An object is in equilibrium when the resultant force acting on it is zero in all directions.
Checking each diagram, the forces on object D do not balance to zero horizontally and vertically.
✅ Answer: (D)
Checking each diagram, the forces on object D do not balance to zero horizontally and vertically.
✅ Answer: (D)
▶️ Answer/Explanation
The moment of a force is calculated using \( \text{moment} = \text{force} \times \text{perpendicular distance from the pivot} \).
The perpendicular distance from the pivot to the line of action of the horizontal force is the vertical side of the triangle, 40 cm.
So moment \( = 5.0 \times 40 = 200 \) N cm.
✅ Answer: (B)
The perpendicular distance from the pivot to the line of action of the horizontal force is the vertical side of the triangle, 40 cm.
So moment \( = 5.0 \times 40 = 200 \) N cm.
✅ Answer: (B)
▶️ Answer/Explanation
At P, the skier is at rest at a height, so all their energy is gravitational potential energy.
As the skier moves down the slope, this converts into kinetic energy.
At Q, the skier comes to rest, so the kinetic energy is converted into thermal energy through friction.
✅ Answer: (B)
As the skier moves down the slope, this converts into kinetic energy.
At Q, the skier comes to rest, so the kinetic energy is converted into thermal energy through friction.
✅ Answer: (B)
▶️ Answer/Explanation
When a gas changes into a liquid, it is losing energy and its particles are moving closer together.
This change of state is called condensation.
✅ Answer: (B)
This change of state is called condensation.
✅ Answer: (B)
▶️ Answer/Explanation
The sound travels to the wall and back again, covering a total distance of \( 2 \times 420 = 840 \) m.
Speed is calculated using \( \text{speed} = \frac{\text{distance}}{\text{time}} = \frac{840}{2.4} \).
This gives a speed of 350 m/s.
✅ Answer: (D)
Speed is calculated using \( \text{speed} = \frac{\text{distance}}{\text{time}} = \frac{840}{2.4} \).
This gives a speed of 350 m/s.
✅ Answer: (D)
▶️ Answer/Explanation
In a plane mirror, the image formed is always the same size as the object, never smaller.
The image is also upright, laterally inverted, and the same distance behind the mirror as the object is in front of it.
Statement B is not correct, since the image is not smaller than the student.
✅ Answer: (B)
The image is also upright, laterally inverted, and the same distance behind the mirror as the object is in front of it.
Statement B is not correct, since the image is not smaller than the student.
✅ Answer: (B)
▶️ Answer/Explanation
Charging occurs by the transfer of electrons, never protons, since protons are fixed inside the nucleus.
For the two insulators to repel, they must end up with the same sign of charge.
If both lost the same amount of electrons, both become positively charged with the same sign, so they repel.
✅ Answer: (C)
For the two insulators to repel, they must end up with the same sign of charge.
If both lost the same amount of electrons, both become positively charged with the same sign, so they repel.
✅ Answer: (C)
▶️ Answer/Explanation
Current is related to e.m.f. and resistance by Ohm’s law: \( I = \frac{V}{R} \).
To increase the current, V must increase and/or R must decrease.
Row C shows an increase in V combined with a decrease in R, which both act to increase the current.
✅ Answer: (C)
To increase the current, V must increase and/or R must decrease.
Row C shows an increase in V combined with a decrease in R, which both act to increase the current.
✅ Answer: (C)
▶️ Answer/Explanation
A fuse is always connected in the live wire of a domestic circuit.
This ensures that if excessive current flows and the fuse blows, the live supply is cut off, making the appliance safe to touch.
✅ Answer: (A)
This ensures that if excessive current flows and the fuse blows, the live supply is cut off, making the appliance safe to touch.
✅ Answer: (A)
▶️ Answer/Explanation
The magnetic field around a straight current-carrying wire forms concentric circles around the wire.
The direction of these field lines is given by the right-hand grip rule, based on the direction of current flow.
For current flowing into the page, applying the right-hand rule gives the pattern and direction shown in diagram A.
✅ Answer: (A)
The direction of these field lines is given by the right-hand grip rule, based on the direction of current flow.
For current flowing into the page, applying the right-hand rule gives the pattern and direction shown in diagram A.
✅ Answer: (A)
▶️ Answer/Explanation
The half-life of the isotope is 3.0 days, meaning the number of atoms halves every 3.0 days.
After 3.0 days (1 half-life): \( 4000 \div 2 = 2000 \) atoms remain.
After 6.0 days (2 half-lives): \( 2000 \div 2 = 1000 \) atoms remain.
✅ Answer: (C)
After 3.0 days (1 half-life): \( 4000 \div 2 = 2000 \) atoms remain.
After 6.0 days (2 half-lives): \( 2000 \div 2 = 1000 \) atoms remain.
✅ Answer: (C)