Q1 · Biodiversity and ecosystem services 4 marks
(a)(i) [2]
There are five core values that humans place on biodiversity. State and describe two of these values, using the extract above.
- Economic value — the reserve supplies humans with raw materials, food and income; for example the mangrove habitat supports the nearby fish farms, or tourism brings visitors and revenue.
- Scientific value — the plants and animals provide systematic ecological data that help us understand the natural world; or they may contain bioactive compounds waiting to be discovered.
- Recreational value — the reserve is used for birdwatching, photography and hiking.
- Cultural value — the reserve meets the inspirational, aesthetic, spiritual or educational needs of people in a highly urbanised country.
- Ecological life support — the reserve provides functioning ecosystems that supply clean air and water and act as natural buffers against erosion and flooding.
1 mark per value stated correctly with a description that fits the extract; accept a paraphrase, not a direct copy of the extract. 1/2 mark for a correct value with no acceptable description.
(a)(ii) [2]
State and describe one type of ecosystem service provided by the reserve.
- Provisioning service — the reserve provides food and raw materials such as fish and timber.
- Regulating service — the mangrove forest regulates the climate, prevents coastal erosion, keeps the water clean and pollinates plants.
- Habitat service — the reserve is a stopover for migratory shorebirds and a home for otters and horseshoe crabs.
- Cultural service — the reserve gives visitors spiritual enrichment, recreation and knowledge, and gives researchers information about species diversity.
1 mark for naming the service, 1 mark for the description.
Modelled on NJC 2022 Section B Q1 · Life science
Q2 · The atmosphere of another world 3 marks
(a) [1]
Explain why this atmosphere would be harmful to human health.
- The atmosphere contains 12% carbon monoxide. Carbon monoxide is a poisonous (toxic) gas that binds to haemoglobin in red blood cells, so less oxygen is carried around the body; this causes headaches, fatigue and, in high doses, death.
The mark needs the poisonous nature of carbon monoxide and its binding to haemoglobin. Reject 'carbon monoxide causes breathing difficulties' — that is not what it does.
(b) [2]
Ozone is present in the upper atmosphere of the planet. State one advantage and one disadvantage of ozone.
- Advantage — in the upper atmosphere ozone absorbs harmful ultraviolet radiation from the Sun, reducing the incidence of skin cancer and cataracts.
- Disadvantage — at ground level ozone irritates the eyes, nose and lungs and irritates the respiratory system.
Reject 'breathlessness' and reject 'ozone traps heat and causes global warming'.
Modelled on NJC 2022 Section B Q2 · Air
Q3 · Separating a mixture 6 marks
(a) [2]
Draw a labelled diagram to show how the sand and the potassium nitrate solution can be obtained separately.
- A filter funnel holding folded filter paper, set in a conical flask or beaker, with the mixture poured into the funnel.
- Correct labels: residue (or sand) on the filter paper, and filtrate (or potassium nitrate solution) collected below.
1 mark for a correct set-up, 1 mark for the two correct labels.
(b) [2]
Describe how a dry sample of potassium nitrate crystals can be obtained from the filtrate collected in (a).
- Heat the filtrate until it is saturated, then allow it to cool so that crystals form.
- Filter the mixture to collect the crystals as the residue, then dry them between sheets of filter paper (or in a warm oven).
The second mark is the one most often lost — the crystals must be filtered out and dried, not simply left to evaporate to dryness.
(c) [2]
Read each statement below carefully. Circle TRUE if you think the statement is true, or FALSE if you think it is false.
- (i) TRUE — potassium nitrate is a compound, and every compound can be broken down into simpler substances by chemical means.
- (ii) FALSE — a compound has its own properties, which are different from the properties of the elements it is made from.
1 mark each.
Modelled on NJC 2022 Section B Q3 · Separation techniques
Q4 · Cells in a leaf 8 marks
(a)(i) [2]
Identify the parts of the cells indicated by A and B.
- A — cell wall (cellulose cell wall)
- B — chloroplast
1 mark each.
(a)(ii) [2]
Describe how B is adapted for its function in the plant.
- B contains chlorophyll, which absorbs light energy so that the cell can carry out photosynthesis to make food for the plant.
- B is elongated (or present in large numbers) to increase the surface area exposed to light, so that more light is absorbed for photosynthesis.
Accept any two sound adaptation points; follow-through from (a)(i) is allowed.
(b) [1]
Based only on the structures that can be seen in Fig. 4, state one way in which this cell is similar to an animal cell.
- Both cells have a cell membrane (and cytoplasm).
Reject 'nucleus' and 'vacuole' — neither can be seen in the figure.
(c) [1]
Explain the importance of division of labour in a living organism.
- Different cells, tissues or organs carry out specialised functions at the same time and work together, so the organism can survive and function efficiently.
Reject vague answers that say 'parts' of the organism instead of cells, tissues or organs.
(d) [2]
Cyanobacteria are prokaryotic cells that can photosynthesise and are often mistaken for plant cells. Describe how a cyanobacterium differs from the cell in Fig. 4.
- A cyanobacterium has a nucleoid region, while the cell in Fig. 4 has a nucleus.
- A cyanobacterium has no membrane-bound organelles, while the cell in Fig. 4 has membrane-bound organelles.
The two differences must be in separate sentences. Reject answers that only say 'prokaryotic versus eukaryotic' without naming what differs.
Modelled on NJC 2022 Section B Q4 · Cells
Q5 · A mirror at a blind corner 4 marks
(a) [3]
Complete the ray diagram in Fig. 5.1 to show how the driver sees the image of the oncoming car in the mirror. Mark the position of the driver with an 'X' and the position of the image with the letter 'I'.
- Point I drawn the same perpendicular distance behind the mirror as the car is in front of it, with the construction lines extended behind the mirror (dotted, no arrow) up to I.
- The reflected ray drawn at the same angle to the normal as the incident ray, with arrowheads showing the light travelling from the mirror to the driver's eye, and with solid lines in front of the mirror.
- X placed on the reflected ray, inside the shaded area.
0.5 mark deducted for each of the following: missing construction lines behind the mirror up to I; solid where dotted or dotted where solid should be; missing or wrong arrowheads; extra unnecessary rays.
(b) [1]
Other than removing blind spots, state one other application of reflection.
- Mirrors in a periscope, so that a person can see over a high obstacle such as a wall.
- Mirrors in a camera or a light box, to reflect light onto a surface and soften shadows.
- A mirror used to check one's own appearance.
- Seeing a non-luminous object: light reflects off its surface into our eyes.
Exactly one mark for any one logical application.
Modelled on NJC 2022 Section B Q5 · Light — reflection
Q6 · A kingfisher over a pond 4 marks
(a) [1]
Measure and record the angle of incidence and the angle of refraction in Fig. 6.1, both measured from the normal.
- Angle of incidence = 48°
- Angle of refraction = 34°
Both angles must be measured from the normal and correct to within 1°. Award the mark only if both are correct — measuring from the surface instead of the normal is the common error.
(b) [2]
A second ray travels along the same path in the opposite direction, from the kingfisher in the air into the water, in Fig. 6.2. Complete Fig. 6.2 to show where the fish sees the image of the kingfisher.
- The refracted ray in the water is extended backwards with a dotted line that carries no arrowhead.
- The apparent image of the kingfisher is marked above its actual position (the image is further from the surface than the bird really is).
Award each mark separately; an arrowhead on the extension line loses the first mark.
(c) [1]
The speed of light in the pond water is 2.26 × 10⁸ m/s. Calculate the refractive index of the water. Show your working.
- n = speed of light in air / speed of light in the water
- n = (3.0 × 10⁸) / (2.26 × 10⁸) = 1.33 (to 3 s.f.)
No mark without working. The answer must not carry units.
Modelled on NJC 2022 Section B Q6 · Light — refraction
Q7 · An incense stick in a room 5 marks
(a) [2]
Using the kinetic model of matter, explain the difference in the movement and the arrangement of the particles in the solid incense stick and in the smoke particles.
- The particles of the solid incense vibrate about fixed positions, while the smoke particles move about at high speed in random directions.
- The particles of the solid incense are very closely packed in an orderly arrangement, while the smoke particles are very far apart and randomly arranged.
1 mark for the movement of both, 1 mark for the arrangement of both — or one mark for each state described completely. Reject 'less closely packed' or 'less orderly' for the smoke particles: those words describe a liquid.
(b) [2]
A bottle of air freshener holds a liquid. Explain, using the kinetic model of matter, why a liquid has a fixed volume but no fixed shape.
- A fixed volume means the particles are still close together and cannot be squeezed into a smaller space.
- No fixed shape means the particles are not locked in position: the forces between them allow them to slide past one another to take the shape of the container.
1 mark for the volume, 1 mark for the shape.
(c) [1]
Using the idea of diffusion, explain why a person standing at the other end of the room can smell the incense.
- Incense particles diffuse from the region of higher concentration near the stick to the region of lower concentration at the other end of the room, so they reach the person's nose.
The move from a higher to a lower concentration must be put in context (from the stick to the other end of the room).
Modelled on NJC 2022 Section B Q7 · Kinetic model and diffusion
Q8 · Atoms, ions and bonding 11 marks
(a) [2]
Fill in the blanks in the table above.
- Ca²⁺: 20 neutrons, 18 electrons
- Cl⁻: 18 neutrons, 18 electrons
1/2 mark for each correct value.
(b) [1]
Chlorine-35 is an isotope of chlorine-37. Define the term isotope.
- Isotopes are atoms of the same element that have the same number of protons (and electrons) but different numbers of neutrons.
The comparison must be stated: same protons, different neutrons.
(c)(i) [1]
Calcium chloride is spread on roads to melt ice. Draw the dot-and-cross diagram of calcium chloride, CaCl₂.
- Two chloride ions, each with a complete outer shell showing the electron transferred from the calcium, and one calcium ion shown as Ca²⁺ with no electrons left in its outer shell.
The charges and the number of electrons in each ion must both be correct.
(c)(ii) [1]
Natural gas is mainly methane, CH₄. Draw the dot-and-cross diagram of methane.
- One carbon atom sharing four pairs of electrons, one pair with each of four hydrogen atoms; each hydrogen has two electrons in its outer shell.
Each shared pair must contain one dot and one cross, and all outer shells must be complete.
Modelled on NJC 2022 Section B Q8 · Atoms and bonding
Q8 · Atoms, ions and bonding 11 marks (continued)
(c)(iii) [3]
Calcium chloride and methane have the same kind of formula ratio, XCl₂ and CH₄. Calcium chloride melts at 772 °C, while methane melts at −182 °C. With reference to structure and bonding, account for the difference in their melting points.
- Calcium chloride is an ionic compound: it has a giant ionic lattice structure held by strong ionic (electrostatic) bonds between the Ca²⁺ cations and the Cl⁻ anions.
- Methane is a simple covalent molecule: it has weak forces of attraction between its molecules.
- Much more energy is needed to overcome the strong ionic bonds in calcium chloride than the weak forces between the methane molecules, so calcium chloride has a much higher melting point.
1 mark for identifying the bonding, 1 mark for identifying the structure, 1 mark for comparing the energy needed.
(c)(iv) [2]
Solid calcium chloride dissolves in water to form a solution that conducts electricity. With reference to structure, explain why the solution conducts electricity.
- When calcium chloride dissolves, the giant ionic lattice breaks down and the ions are no longer held in fixed positions.
- The Ca²⁺ and Cl⁻ ions become mobile charge carriers, so the solution conducts electricity.
The mobile charge carriers must be named as the ions — a wrong particle loses the whole part.
(c)(v) [1]
Unlike calcium chloride, graphite does not dissolve in water, yet it conducts electricity in the solid state. With reference to structure, explain how.
- In graphite each carbon atom is bonded to three other carbon atoms, so one valence electron per atom is not used in bonding. These delocalised electrons are free to move along the layer and act as mobile charge carriers.
The general idea of a delocalised electron free to move is enough for the single mark.
Modelled on NJC 2022 Section B Q8 · Atoms and bonding
