Question 1
(a) Subtopic: B6.1 Photosynthesis
(b) Subtopic: B6.1 Photosynthesis
(i) Subtopic: B6.1 Photosynthesis
(ii) Subtopic: B5 Enzymes
(iii) Subtopic: B5 Enzymes
(iv) Subtopic: B6.1 Photosynthesis
(a) State the balanced equation for photosynthesis.
▶️Answer/Explanation
6CO2 + 6H2O → C6H12O6 + 6O2
(b) A student investigates the effect of temperature on the rate of photosynthesis of an aquatic plant.
The student counts the number of bubbles produced per minute at different temperatures. The results are shown in Table 1.1.
(i) State the temperature that resulted in the fastest rate of photosynthesis.
▶️Answer/Explanation
25°C
(ii) Place ticks (✓) next to all the statements that explain the results between 0°C and 10°C.
▶️Answer/Explanation
✓ The kinetic energy of the particles increases.
✓ There are more frequent collisions between the substrate and enzyme.
(iii) Explain the results at 40°C from Table 1.1.
▶️Answer/Explanation
At 40°C, photosynthesis stops because:
1. The enzymes have become denatured
2. The active site has changed shape and is no longer complementary to the substrate
3. Substrate molecules can no longer fit into the active sites of enzymes
(iv) Explain why the light intensity is kept constant during this investigation.
▶️Answer/Explanation
1. A change in light intensity would affect the rate of photosynthesis
2. Only the effect of temperature is being investigated, so all other variables must be kept constant
Question 2
(a) Subtopic: C2.2 Atomic structure and the Periodic Table
(b) (i) Subtopic: C2.2 Atomic structure and the Periodic Table
(ii) Subtopic: C2.2 Atomic structure and the Periodic Table
(c) Subtopic: C2.4 Ions and ionic bonds
(d) Subtopic: C3.3 The mole and the Avogadro constant
(a) Table 2.1 shows some information about the charges and relative masses of three subatomic particles.
| particle A | particle B | particle C | |
|---|---|---|---|
| charge | +1 | no charge | -1 |
| relative mass | 1 | 1 | 1 |
Use the information in Table 2.1 to state the names of particles A, B and C.
▶️Answer/Explanation
Answer:
particle A – proton
particle B – neutron
particle C – electron
Explanation:
From the table:
– Particle A has a +1 charge and relative mass of 1 → proton
– Particle B has no charge and relative mass of 1 → neutron
– Particle C has -1 charge and relative mass of 1 → electron
(b) Fig. 2.1 shows a diagram of an atom of magnesium.
(i) State why this atom of magnesium has a proton number (atomic number) of 12 and a nucleon number (mass number) of 24.
▶️Answer/Explanation
Answer:
proton number of 12 because (magnesium) has 12 protons
nucleon number of 24 because (magnesium) has 12 protons and 12 neutrons
Explanation:
– The proton number (atomic number) is determined by the number of protons in the nucleus.
– The nucleon number (mass number) is the sum of protons and neutrons in the nucleus.
(ii) State the electronic structure of this atom of magnesium.
▶️Answer/Explanation
Answer: 2.8.2
Explanation:
Magnesium (atomic number 12) has electron arrangement:
– First shell: 2 electrons
– Second shell: 8 electrons
– Third shell: 2 electrons
(c) Magnesium reacts with oxygen to form magnesium oxide, MgO. Magnesium oxide is an ionic compound with a melting point of 2852°C. Oxygen reacts with hydrogen to form water, H₂O. Water is a covalent compound with a melting point of 0°C.
Explain the difference in the melting points of magnesium oxide and water in terms of attractive forces.
▶️Answer/Explanation
Answer:
Magnesium oxide has strong (electrostatic) forces of attraction between oppositely charged magnesium ions and oxide ions. Water has weak intermolecular forces between molecules. Strong forces of attraction take more energy to break than weak intermolecular forces.
Explanation:
– MgO is ionic with strong electrostatic attractions between Mg²⁺ and O²⁻ ions requiring much energy to overcome.
– H₂O is covalent with weaker hydrogen bonds/intermolecular forces between molecules requiring less energy to overcome.
(d) Magnesium oxide reacts with dilute hydrochloric acid, HCl. Magnesium chloride, MgCl₂, is made. The balanced symbol equation for the reaction is shown.
MgO + 2HCl → MgCl₂ + H₂O
In an experiment, 2.0 g of magnesium oxide reacts with excess dilute hydrochloric acid. Calculate the maximum mass of magnesium chloride that can be made. Show your working.
[A: Cl, 35.5; H, 1; Mg, 24; O, 16]
▶️Answer/Explanation
Answer: 4.75 g
Working:
1. Calculate relative formula masses:
– MgO = 24 + 16 = 40
– MgCl₂ = 24 + (2 × 35.5) = 95
2. Find moles of MgO:
moles = mass/RFM = 2.0/40 = 0.05 mol
3. From equation, 1 mole MgO → 1 mole MgCl₂
So 0.05 mol MgO → 0.05 mol MgCl₂
4. Calculate mass of MgCl₂:
mass = moles × RFM = 0.05 × 95 = 4.75 g
Alternative method using ratio:
(2.0 g MgO / 40) × 95 = 4.75 g
Question 3
(a) (i) Subtopic: P1.6.1 Energy
(ii) Subtopic: P1.6.1 Energy
(b) Subtopic: P1.5 Force
(c) (i) Subtopic: P1.5.1 Effects of forces
(ii) Subtopic: P1.5.1 Effects of forces
(iii) Subtopic: P1.5.1 Effects of forces
Fig. 3.1 shows a tennis player throwing a ball in the air before the player hits the ball.
(a) The ball has a mass of 56.25g and is thrown vertically upwards with a velocity of 8.0 m/s.
(i) Calculate the kinetic energy of the ball immediately after it leaves the player’s hand.
▶️Answer/Explanation
Solution:
1. First convert mass to kg: 56.25 g = 0.05625 kg
2. Kinetic energy formula: KE = ½mv²
3. Calculation: KE = 0.5 × 0.05625 × (8.0)² = 1.8 J
Answer: 1.8 J
(ii) The tennis player notices that the ball has a velocity of zero when it reaches its maximum height.
Name the form of energy stored by the ball at its maximum height.
▶️Answer/Explanation
Solution:
At maximum height, all kinetic energy has been converted to gravitational potential energy.
Answer: gravitational potential energy
(b) Fig. 3.2 shows the tennis player hitting the same ball with the racket.
This causes the ball to accelerate at 1600 m/s².
Calculate the force applied to the ball by the racket.
▶️Answer/Explanation
Solution:
1. Force formula: F = ma
2. Calculation: F = 0.05625 kg × 1600 m/s² = 90 N
Answer: 90 N
(c) A student removes one of the nylon strings from the racket to investigate how it deforms when tensile forces are applied.
Fig. 3.3 shows the equipment used.
The student adds masses to the mass hanger and records the extension of the nylon string.
Fig. 3.4 shows the results from this investigation.
(i) Use Fig. 3.4 to find the force required to give an extension of 3 mm.
▶️Answer/Explanation
Solution:
From the graph, at 3 mm extension, the corresponding force is approximately 33 N.
Answer: 33 N
(ii) State Hooke’s law.
▶️Answer/Explanation
Solution:
Hooke’s Law states that the extension of an elastic material is directly proportional to the applied force, provided the elastic limit is not exceeded.
Answer: extension is directly proportional to the force applied
(iii) Describe how the graph in Fig. 3.4 shows that the nylon string does not obey Hooke’s law.
▶️Answer/Explanation
Solution:
1. The graph is a curve rather than a straight line, indicating the extension is not directly proportional to the force.
2. The gradient changes, showing the relationship between force and extension is not constant.
Answer: The graph is a curve/not straight line; force is not directly proportional to extension
Question 4
(a) (i) Subtopic: B13.3 Homeostasis
(ii) Subtopic: B13.2 Hormones
(b) Subtopic: B13.2 Hormones
(c) Subtopic: B13.3 Homeostasis
(d) (i) Subtopic: B7.3 Digestion
(ii) Subtopic: B7.2 Digestive system
(a) A person monitored the concentration of glucose in their blood for 12 hours.
The results are shown in Fig. 4.1.
(i) The concentration of glucose in the blood increases rapidly after a meal is eaten. Suggest the number of meals the person had during the 12 hours.
▶️Answer/Explanation
The person had 3 meals during the 12 hours. This is evident from the three distinct peaks in the graph where glucose concentration rises sharply, indicating food intake.
(ii) Complete the sentences to explain the results between 2 and 3 hours.
The brain detects an increase in the concentration of glucose in the blood.
The …… releases insulin.
The insulin stimulates the …… to convert glucose to ……
…… and store it.
This lowers the concentration of glucose in the blood.
▶️Answer/Explanation
The pancreas releases insulin.
The insulin stimulates the liver to convert glucose to glycogen
and store it.
Explanation: When blood glucose rises after eating, the pancreas secretes insulin which signals the liver to store excess glucose as glycogen through glycogenesis.
(b) Name two hormones that increase blood glucose concentration.
▶️Answer/Explanation
1 adrenaline
2 glucagon
Note: These are the primary hormones that counteract insulin’s effects. Adrenaline is released during stress, while glucagon is secreted by the pancreas when blood sugar drops too low.
(c) Name the term used to describe the mechanism that is used to return blood glucose concentrations to a normal level.
▶️Answer/Explanation
negative feedback
Explanation: This is a homeostatic mechanism where the body detects deviations from normal glucose levels and triggers responses (insulin/glucagon release) to restore balance.
(d) Glucose is absorbed in the small intestine.
(i) Define the term absorption.
▶️Answer/Explanation
Movement of digested food molecules
across the wall of the small intestine
into the bloodstream
Key points: Absorption involves the transfer of nutrients from the digestive tract into circulation, primarily occurring in the small intestine’s villi.
(ii) Describe how the small intestine is adapted for efficient absorption.
▶️Answer/Explanation
1 Presence of villi and microvilli – These finger-like projections dramatically increase surface area for absorption.
2 Thin epithelial walls – Short diffusion distance for nutrients to enter capillaries.
Additional adaptations: Rich blood supply maintains concentration gradient, and carrier proteins facilitate active transport of glucose.
Question 5
(a) Subtopic: C11.3 Fuels
(b) Subtopic: C11.3 Fuels
(c) Subtopic: C11.1 Formulas and terminology
(d) Subtopic: C11.4 Alkanes
(e) Subtopic: C5.1 Exothermic and endothermic reactions
(f) (i) Subtopic: C5.1 Exothermic and endothermic reactions
(ii) Subtopic: C5.1 Exothermic and endothermic reactions
Petroleum is a fossil fuel. Petroleum can be separated into useful fractions by fractional distillation.
Fig. 5.1 shows a fractionating column.
(a) Explain why it is possible to separate the substances in petroleum by fractional distillation.
▶️Answer/Explanation
Answer: Substances have different boiling points.
Explanation:
Petroleum is a mixture of hydrocarbons with different chain lengths. Longer hydrocarbon chains have higher boiling points, so they condense at higher temperatures in the fractionating column, while shorter chains with lower boiling points rise higher before condensing. This allows for separation based on their different boiling points.
(b) Table 5.1 shows the uses of some of the fractions. Complete Table 5.1.
| fraction | use |
|---|---|
| refinery gas | bottled gas for heating |
| gasoline | fuel (petrol) in cars |
| naphtha | …… |
| diesel oil | …… |
| bitumen | …… |
▶️Answer/Explanation
Answer:
| naphtha | feedstock for making chemicals |
| diesel oil | fuel in diesel engines |
| bitumen | road surfaces |
Explanation:
– Naphtha is used as a chemical feedstock for producing plastics and other petrochemicals.
– Diesel oil is used as fuel for trucks, buses and some cars with diesel engines.
– Bitumen is a thick, viscous fraction used for waterproofing and road construction.
(c) Butane is a hydrocarbon found in the refinery gas fraction. Complete Fig. 5.2 to show the structure of a butane molecule. Show all the covalent bonds.
▶️Answer/Explanation
Answer:
H H H H
| | | |
H—C—C—C—C—H
| | | |
H H H H
Explanation:
Butane (C₄H₁₀) is an alkane with 4 carbon atoms in a straight chain, each carbon forming 4 single covalent bonds (3 with hydrogen and 1 with adjacent carbon).
(d) Methane, CH₄, is also a hydrocarbon found in the refinery gas fraction. Methane burns in oxygen to form carbon dioxide and water. Construct the balanced symbol equation for the burning of methane.
▶️Answer/Explanation
Answer: CH₄ + 2O₂ → CO₂ + 2H₂O
Explanation:
Balancing steps:
1. Start with CH₄ + O₂ → CO₂ + H₂O
2. Balance C: 1 on both sides (balanced)
3. Balance H: 4 on left → need 2H₂O on right
4. Now balance O: 2O₂ needed on left to match 4 oxygen atoms on right
(e) When methane burns, an exothermic reaction takes place. State what is meant by an exothermic reaction.
▶️Answer/Explanation
Answer: Reaction in which thermal energy is given out to the surroundings.
Explanation:
In exothermic reactions, the energy released from forming new bonds is greater than the energy needed to break the original bonds, resulting in a net release of heat energy.
(f) The reaction of hydrogen with oxygen to make water is another exothermic reaction. Look at the equation for this reaction. It shows all the atoms and all the bonds.
(i) Put a circle around each of the bonds which are broken when the reaction takes place.
▶️Answer/Explanation
Answer: Circle around H—H bond and O=O bond
Explanation:
In the reaction 2H₂ + O₂ → 2H₂O, the bonds that break are:
– The single bond between hydrogen atoms (H—H)
– The double bond between oxygen atoms (O=O)
(ii) Explain why the reaction of hydrogen with oxygen is exothermic. Use ideas about bond breaking and bond making.
▶️Answer/Explanation
Answer:
Bond breaking is endothermic (requires energy) and bond making is exothermic (releases energy). More energy is released when the new O—H bonds form than is absorbed when breaking the H—H and O=O bonds, resulting in a net release of energy.
Explanation:
– Energy required to break bonds: H—H (436 kJ/mol) + O=O (498 kJ/mol) = 934 kJ/mol
– Energy released making bonds: 4 × O—H (463 kJ/mol) = 1852 kJ/mol
– Net energy change: 1852 – 934 = 918 kJ/mol released (exothermic)
Question 6
(a) (i) Subtopic: P1.6.3 Energy resources
(ii) Subtopic: P1.6.3 Energy resources
(b) Subtopic: P2.1.2 Particle model
(c) (i) Subtopic: P4.5.2 The a.c. generator
(ii) Subtopic: P4.5.2 The a.c. generator
(a) Electricity may be obtained using the sources listed.
fossil fuels
geothermal
solar
tidal
wind
(i) State which of the sources of energy is non-renewable.
▶️Answer/Explanation
fossil fuels
Explanation: Fossil fuels are non-renewable because they take millions of years to form and are being depleted much faster than they can be naturally replenished.
(ii) State which two of the sources of energy are not dependent on the Sun.
▶️Answer/Explanation
geothermal and tidal
Explanation: Geothermal energy comes from Earth’s internal heat, and tidal energy comes from gravitational interactions between Earth, Moon and Sun (primarily the Moon’s gravity). Solar energy is directly dependent on the Sun, while wind energy is indirectly dependent (wind is caused by uneven solar heating of Earth’s surface).
(b) Many types of power station use steam to turn a turbine attached to a generator.
Explain, in terms of the forces and distances between molecules and the motion of molecules, why steam is able to fill its container.
▶️Answer/Explanation
– Steam particles have high kinetic energy and move rapidly in random directions
– The particles are far apart with weak intermolecular forces between them
– This allows the particles to spread out and fill the available space in the container
– Unlike liquids or solids, steam particles aren’t confined by strong attractive forces
Key points: Steam is a gas where particles have enough energy to overcome intermolecular forces and expand to fill their container.
(c) Fig. 6.1 shows a diagram of a simple a.c. generator.
(i) Explain why the generator produces an a.c. output.
▶️Answer/Explanation
– As the coil rotates in the magnetic field, it cuts through magnetic field lines
– This induces an electromotive force (emf) in the coil
– The direction of the induced current changes every half turn because the coil sides swap positions relative to the magnetic poles
– This continuous change in current direction produces alternating current (a.c.)
Note: The output is a.c. specifically because the current direction reverses periodically as the coil rotates.
(ii) On the grid provided in Fig. 6.2, sketch a graph of voltage output against time for this generator.
You must show at least one full cycle.
▶️Answer/Explanation
[Sine wave graph showing voltage alternating between positive and negative values]
Key features:
– Smooth, periodic sine curve
– Equal positive and negative peaks
– At least one complete cycle shown (360° rotation)
– Voltage crosses zero at regular intervals
Why: The alternating current produced by a simple generator follows a sinusoidal pattern as the coil rotates through the magnetic field.
Question 7
(a) Subtopic: B6.2 Leaf structure
(b) Subtopic: B6.2 Leaf structure
(c) (i) Subtopic: B8.1 Xylem and phloem
(ii) Subtopic: B8.4 Translocation
(d) Subtopic: B8.3 Transpiration
Fig. 7.1 is a diagram of a cross-section of a leaf.
(a) Identify the letter that represents the part in Fig. 7.1:
where most photosynthesis takes place ……
which transports water from roots to leaves ……
which controls gas exchange. ……
▶️Answer/Explanation
- Most photosynthesis takes place: E (palisade mesophyll layer)
- Transports water from roots to leaves: A (xylem)
- Controls gas exchange: C (guard cells/stomata)
Explanation: The palisade mesophyll (E) contains many chloroplasts for photosynthesis. Xylem (A) transports water and minerals from roots. Guard cells (C) regulate stomatal opening for gas exchange.
(b) Draw an X on Fig. 7.1 to identify a spongy mesophyll cell.
▶️Answer/Explanation
X should be placed in the lower layer of mesophyll cells (irregularly shaped cells with air spaces between them).
Explanation: Spongy mesophyll cells are located below the palisade layer and have large air spaces between them to facilitate gas exchange.
(c) The part labelled B in Fig. 7.1 is responsible for translocation.
(i) Name the part labelled B.
▶️Answer/Explanation
Phloem
Explanation: Phloem is the vascular tissue specialized for transporting organic nutrients (translocation) throughout the plant.
(ii) Name the two main substances transported by the part labelled B.
▶️Answer/Explanation
- Sucrose
- Amino acids
Explanation: Phloem primarily transports sucrose (the main photosynthetic product) and amino acids (nitrogen-containing compounds) from source to sink.
(d) Table 7.1 compares the processes of transpiration and translocation.
Place ticks (✓) in the boxes to show the correct features of transpiration and translocation.
| transpiration | translocation | |
|---|---|---|
| transports substances to regions of storage | ||
| transports water | ||
| movement of substances is in one direction only | ||
| transport is from source to sink |
▶️Answer/Explanation
| transpiration | translocation | |
|---|---|---|
| transports substances to regions of storage | ✓ | |
| transports water | ✓ | |
| movement of substances is in one direction only | ✓ | |
| transport is from source to sink | ✓ |
Explanation: Transpiration moves water unidirectionally (roots→leaves). Translocation is bidirectional (source→sink) and transports sugars to storage organs.
Question 8
(a) (i) Subtopic: C6.2 Rate of reaction
(ii) Subtopic: C6.2 Rate of reaction
(b) Subtopic: C6.2 Rate of reaction
(c) Subtopic: C12.5 Identification of ions and gases
(d) Subtopic: C3.3 The mole and the Avogadro constant
A scientist investigates the reaction between marble chips (calcium carbonate) and dilute hydrochloric acid. The scientist uses 20 g of marble chips and 40 cm³ of dilute hydrochloric acid. The temperature of the acid is 25 °C. Fig. 8.1 shows the apparatus used.
The scientist measures the mass every 20 seconds until the reaction stops. The scientist calculates the loss in mass. Fig. 8.2 shows the results.
(a)(i) Use Fig. 8.2 to state the loss in mass after 40 seconds.
▶️Answer/Explanation
From the graph at 40 seconds, the loss in mass is 0.3 g.
(a)(ii) Use Fig. 8.2 to state how long it takes for the reaction to stop.
▶️Answer/Explanation
The reaction stops when the graph becomes horizontal at 156 seconds.
(b) The scientist does the experiment again. This time the scientist uses dilute hydrochloric acid which is less concentrated than in the first experiment. The reaction is slower.
Explain why reactions are slower when reactants are less concentrated. Explain your answer in terms of collisions between particles.
▶️Answer/Explanation
In less concentrated acid:
1) There are fewer acid particles per unit volume
2) This results in fewer frequent collisions between acid particles and marble chips
3) Fewer successful collisions per second means a slower reaction rate
(c) Carbon dioxide gas is made in the reaction. State the chemical test and its positive result for carbon dioxide gas.
▶️Answer/Explanation
Test: Bubble the gas through limewater (calcium hydroxide solution)
Positive result: The limewater turns milky/cloudy due to formation of calcium carbonate
(d) In this experiment, 0.47 g of carbon dioxide gas is made. Calculate the volume occupied by 0.47 g of carbon dioxide gas. The molar gas volume at 25 °C is 24 dm3. Show your working.
[Ar : C, 12; O, 16]
▶️Answer/Explanation
Solution:
1) Calculate molar mass of CO₂: 12 + (16×2) = 44 g/mol
2) Moles of CO₂ = mass/molar mass = 0.47/44 = 0.0107 mol
3) Volume = moles × molar volume = 0.0107 × 24 = 0.256 dm³
Final answer: 0.26 dm³ (rounded to 2 significant figures)
Question 9
(a) Subtopic: P3.1 General properties of waves
(b) (i) Subtopic: P3.2.2 Refraction of light
(ii) Subtopic: P3.2.2 Refraction of light
(iii) Subtopic: P3.2.2 Refraction of light
(c) Subtopic: P4.2.5 Electrical energy and electrical power
(d) (i) Subtopic: P4.3.2 Series and parallel circuits
(ii) Subtopic: P4.2.2 Electric current
Visible light is a transverse wave and is part of the electromagnetic spectrum.
(a) State what is meant by a transverse wave.
▶️Answer/Explanation
A transverse wave is a wave where the vibrations or oscillations of the particles are perpendicular to the direction of energy transfer.
(b) Fig. 9.1 shows a ray of visible light from a torch (flashlight) shining into a rectangular glass block.
(i) Complete Fig. 9.1 to show the path the ray takes through and out of the block.
▶️Answer/Explanation
The ray should:
1. Bend towards the normal when entering the glass block
2. Travel straight through the block
3. Bend away from the normal when exiting the block, emerging parallel to the original incident ray
(ii) State the term used to describe what happens to the ray of light as it enters the glass block.
▶️Answer/Explanation
Refraction
(iii) Explain why this happens to the ray of light.
▶️Answer/Explanation
The light changes speed as it moves from air (less dense medium) to glass (more dense medium), causing it to bend. This change in speed occurs because light travels slower in denser materials.
(c) Fig. 9.2 shows the electrical circuit used in the torch.
When the switch is closed, the current in the lamp is 1.8A and the potential difference across the lamp is 3.0V.
Calculate the power output of the lamp.
▶️Answer/Explanation
Using the formula P = IV:
P = 1.8A × 3.0V = 5.4W
Power = 5.4 W
(d) Fig. 9.3 shows two lamps, identical to the torch lamp, connected in parallel.
(i) When the switch is closed, the ammeter reads 2.6A.
State the current in each lamp.
▶️Answer/Explanation
In a parallel circuit with identical lamps, the current splits equally:
2.6A ÷ 2 = 1.3A
Current = 1.3 A
(ii) Calculate the quantity of charge passing through one of the lamps in Fig. 9.3 when it is switched on for 30 seconds.
Give the correct unit for your answer.
▶️Answer/Explanation
Using Q = It:
Q = 1.3A × 30s = 39 Coulombs
Charge = 39 C (Coulombs)
Question 10
(a) (i) Subtopic: B17.1 Variation
(ii) Subtopic: B17.1 Variation
(iii) Subtopic: B17.1 Variation
(iv) Subtopic: B17.1 Variation
(b) Subtopic: B9.4 Blood
(c) Subtopic: B9.4 Blood
(a) The blood groups of some people are recorded. Fig. 10.1 shows the results.
(i) State the total number of people who had their blood group recorded.
▶️Answer/Explanation
100 people
(ii) Describe the evidence in Fig. 10.1 that shows blood group is an example of discontinuous variation.
▶️Answer/Explanation
The graph shows distinct categories (A, AB, B, O) with no intermediate values between them. This clear separation into distinct groups with no overlap is characteristic of discontinuous variation.
(iii) Complete this sentence about discontinuous variation.
Discontinuous variation is mostly caused by …… alone.
▶️Answer/Explanation
genes
(iv) Name one example of continuous variation in humans.
▶️Answer/Explanation
Height (or other acceptable examples like weight, skin color, etc.)
(b) Blood contains four main components. The boxes on the left show the components of blood. The boxes on the right show the functions of each component. Draw lines to link each component with its function.
▶️Answer/Explanation
plasma → transport of ions, soluble nutrients and hormones
platelet → blood clotting
red blood cell → transport of oxygen
white blood cell → antibody production
Note: The correct matching is the opposite of what might be initially assumed from the question’s layout.
(c) Describe two ways the structure of a red blood cell is adapted to its function.
▶️Answer/Explanation
1. Biconcave shape – increases surface area for oxygen absorption
2. Contains hemoglobin – binds with oxygen molecules
3. No nucleus – more space for hemoglobin (any two of these)
Question 11
(a) Subtopic: C2.4 Ions and ionic bonds
(b) Subtopic: C2.4 Ions and ionic bonds
(c) Subtopic: C3.1 Formulas
(d) Subtopic: C9.6 Extraction of metals
(e) Subtopic: C6.3 Redox
Sodium, Na, is an element in Group I of the Periodic Table. Sodium has the electronic structure 2.8.1.
(a) Sodium atoms can form sodium ions, Na+. Chlorine atoms can form chloride ions, Cl–.
Describe, in terms of electrons, how a sodium atom forms a sodium ion and a chlorine atom forms a chloride ion.
▶️Answer/Explanation
A sodium atom loses one electron to form a Na+ ion, achieving a stable electron configuration (2.8). A chlorine atom gains one electron to form a Cl– ion, completing its outer shell (2.8.8).
Mark Scheme: (sodium atom) loses one electron and (chlorine atom) gains one electron ;
(b) Sodium ions, Na+, form ionic bonds with chloride ions, Cl–. Describe how ionic bonds form between sodium ions and chloride ions.
▶️Answer/Explanation
Ionic bonds form due to the electrostatic attraction between oppositely charged ions (Na+ and Cl–). Sodium donates an electron to chlorine, creating ions that are held together by strong forces of attraction.
Mark Scheme: electrostatic attraction ; between oppositely charged ions ;
(c) Solid aluminium chloride is another ionic compound. Aluminium chloride contains aluminium ions, Al3+, and chloride ions, Cl–.
Determine the formula of aluminium chloride.
▶️Answer/Explanation
Aluminium (Group III) loses 3 electrons to form Al3+, while each chlorine (Group VII) gains 1 electron to form Cl–. To balance the charges, 3 chloride ions are needed for every aluminium ion: AlCl3.
Mark Scheme: AlCl3 ;
(d) Fig. 11.1 shows the apparatus used to extract aluminium from aluminium ore.
Describe how aluminium is extracted from aluminium ore. Include the starting materials and the essential reaction conditions.
▶️Answer/Explanation
Aluminium is extracted via electrolysis of molten aluminium oxide (alumina) dissolved in cryolite. Key steps:
1. Cryolite lowers the melting point of alumina, reducing energy costs.
2. At the cathode: Al3+ + 3e– → Al (molten aluminium collects at the bottom).
3. At the anode: 2O2– → O2 + 4e– (oxygen reacts with carbon anodes, producing CO2).
Mark Scheme: molten aluminium oxide / alumina, and cryolite ; electrolysis / use of electricity ; high temperature ;
(e) Copper is extracted from copper ore by heating the copper ore with carbon.
The equation for the reaction is shown:
2CuO + C → 2Cu + CO2
Carbon is the reducing agent in this reaction.
Define, in terms of electrons, what is meant by the term reducing agent.
▶️Answer/Explanation
A reducing agent donates electrons to another substance (here, carbon donates electrons to CuO, reducing Cu2+ to Cu). It is itself oxidised in the process.
Mark Scheme: (species that) loses or donates electrons ;
Question 12
(a) Subtopic: P1.2 Motion
(b) Subtopic: P1.2 Motion
(c) Subtopic: P1.2 Motion
(d) (i) Subtopic: P1.5 Force
(ii) Subtopic: P1.3 Mass and weight
(e) Subtopic: P2.3.3 Radiation
Fig. 12.1 shows a speed-time graph for a train.
(a) Use Fig. 12.1 to calculate the distance travelled by the train in the first 100 s.
▶️Answer/Explanation
Answer: 500 m
Explanation: The distance travelled is the area under the speed-time graph for the first 100 seconds. For a trapezium, area = ½ × (sum of parallel sides) × height. Here, the parallel sides are 0 m/s and 10 m/s, and the height is 100 s. So, distance = ½ × (0 + 10) × 100 = 500 m.
(b) Use Fig. 12.1 to calculate the acceleration of the train from 0 s to 100 s.
▶️Answer/Explanation
Answer: 0.1 m/s²
Explanation: Acceleration is the change in velocity divided by time. From the graph, the speed increases from 0 m/s to 10 m/s in 100 s. So, acceleration = (10 – 0) / 100 = 0.1 m/s².
(c) Use Fig. 12.1 to describe the motion of the train from 100 s to 200 s.
▶️Answer/Explanation
Answer: The train accelerates at a decreasing rate until about 160 s, then maintains a constant speed.
Explanation: From 100 s to 160 s, the slope of the graph decreases, indicating decreasing acceleration. After 160 s, the slope is zero, meaning the train moves at a constant speed (no acceleration).
(d) Fig. 12.2 shows the forces acting on the train when it is travelling at constant speed.
(i) State the magnitude of the force P.
▶️Answer/Explanation
Answer: 2.60 × 10⁴ N
Explanation: At constant speed, the forward force (P) equals the resistive force (2.60 × 10⁴ N) for no net acceleration.
(ii) Calculate the mass of the train.
The gravitational field strength on Earth, g, is 10 N/kg.
▶️Answer/Explanation
Answer: 1.96 × 10⁵ kg
Explanation: Weight = mass × gravitational field strength. Given weight = 1.96 × 10⁶ N and g = 10 N/kg, mass = weight / g = (1.96 × 10⁶) / 10 = 1.96 × 10⁵ kg.
(e) The train is made of steel painted dark grey. On sunny days, the inside of the train can get very hot. Explain why painting the train white would reduce the heating effect.
▶️Answer/Explanation
Answer: White paint reflects more thermal/infrared radiation, absorbing less heat compared to dark grey.
Explanation: Lighter colors reflect more sunlight and absorb less thermal energy, keeping the interior cooler.