Primary 5 Science Systems Quiz

Primary 5 Science Quiz - Systems: Answer Key

Total Marks: 40 marks

Section A: Electrical Systems

1. (a) On [1]

(b) The switch is closed, so the circuit is complete. Electricity can flow from the battery, through the switch and bulb, and back to the battery. [1]

Teaching note: A complete/closed circuit is needed for electricity to flow. The switch closes the gap in the circuit.

2. Circuit B [1]

Circuit B has two batteries connected in series, which provides more electrical energy than one battery. More energy means more current flows, making the bulb brighter. [1]

Teaching note: Batteries in series add their voltages (roughly). More voltage pushes more current through the bulb, which glows brighter. The bulb's brightness depends on the electrical energy it receives.

3. Copper [2]

Teaching note: Copper is a good conductor of electricity. It has free electrons that can move easily, allowing electric current to flow. Other acceptable answers: aluminium, silver, gold (any metal). Common mistake: students may write "metal" only — this is too vague for full marks unless specified as "metals like copper."

4. (a) Metal spoon [1]

Teaching note: Metals allow electricity to pass through — they are conductors.

(b) Plastic and wood are insulators. They do not allow electricity to pass through easily because their electrons are held tightly and cannot move freely. [1]

Teaching note: Insulators resist the flow of electricity. The bulb stays off because no current can flow through the plastic ruler or wooden chopstick to complete the circuit.

5. Circuit should show two bulbs connected in parallel with one battery [2]

Marking points:

• [1] Two bulbs both connected to allow current flow
• [1] Parallel arrangement (both bulbs connected across same two points so they have equal brightness)

Teaching note: In parallel, each bulb gets the full voltage of the battery, so both shine equally bright. In series, bulbs share the voltage and would be dimmer. Draw: battery with two separate loops, each with one bulb, returning to battery.

Section B: Human Transport Systems

6. (a) D (left ventricle) [1]

Teaching note: The left ventricle has the thickest muscular wall because it needs to pump blood to all parts of the body through the aorta. The right ventricle only pumps to the lungs, which is a shorter distance.

(b) Pulmonary vein [1]

Teaching note: Veins typically carry blood toward the heart. The pulmonary vein is special — it carries oxygen-rich blood from the lungs back to the heart (left atrium). Don't confuse with pulmonary artery, which carries blood away from the heart to the lungs.

7. (a) Vein [1]

Teaching note: Valves are visible in the diagram as flap-like structures.

(b) Veins carry blood back to the heart against gravity (especially in legs). Valves prevent backflow and ensure blood flows in one direction toward the heart. [1]

Teaching note: Arteries have thick, muscular walls and high pressure from the heart pump, so they don't need valves. Veins have lower pressure and need valves to stop blood pooling or flowing backward due to gravity.

8. (a) (i) Yes [1] (ii) Yes [1]

(b) Plasma [1]

Teaching note: All listed components are parts of blood. Plasma is the yellowish liquid that makes up about 55% of blood volume. It carries dissolved nutrients, hormones, waste products, and blood cells.

9. (a) During exercise, muscles need more energy. They need more oxygen and glucose for respiration, and need to remove more carbon dioxide. The heart beats faster to pump more blood carrying these substances to and from the muscles faster. [2]

Marking breakdown:

• [1] Muscles need more oxygen/glucose/energy during exercise
• [1] Faster heart rate delivers blood (with these substances) more quickly

(b) Respiratory system and muscular system (any two correct systems: muscular, respiratory, nervous) [1]

Teaching note: The respiratory system breathes faster to get more oxygen and remove more CO₂. The nervous system sends signals to increase heart and breathing rates. The muscular system is the one doing the work.

10. (a) 1: Nose/Nostril [1] 5: Air sac/Alveolus [1]

(b) The alveolus has thin walls (one cell thick) and a large surface area. It is surrounded by blood capillaries, allowing oxygen to diffuse quickly into the blood and carbon dioxide to diffuse out. [2]

Marking breakdown:

• [1] Thin walls / large surface area / surrounded by blood capillaries (any one structural feature)
• [1] Allows efficient gas exchange / diffusion of gases

Teaching note: The alveolus is adapted for maximum gas exchange efficiency. Thin walls reduce diffusion distance; large surface area maximizes exchange area; rich blood supply maintains concentration gradient.

Section C: Plant Transport Systems

11. (a) Xylem [1]

Teaching note: Xylem vessels are dead, hollow tubes that transport water and minerals upward from roots to leaves. They have thick, lignified walls for support.

(b) Phloem [1]

Teaching note: Phloem transports food (sugars/glucose produced in photosynthesis) from leaves to other plant parts — roots, fruits, growing areas. Unlike xylem, phloem consists of living cells.

12. (a) The water level will decrease / go down. [1]

(b) The celery stalk and leaves will turn red/blue (the colour of the water). This happens because water is absorbed by the roots and transported up the stem through the xylem to the leaves. [2]

Marking breakdown:

• [1] Observation: coloured water visible in stalk/leaves
• [1] Explanation: water transported up through xylem from roots to leaves

Teaching note: This classic experiment demonstrates capillary action and xylem transport. The coloured water makes the invisible process visible. The water level drops because water is absorbed and also evaporates from the leaf surface.

13. (a) (i) No [1] (ii) Blood / Blood cells and plasma [1]

(b) Plants do not have a muscular pump (heart) like animals. Water moves up through xylem by capillary action and transpiration pull, not by pumping. [2]

Marking breakdown:

• [1] Plants lack a heart / muscular pump / pumping organ
• [1] Water movement relies on transpiration pull / capillary action / evaporation from leaves creating suction

Teaching note: This is a key difference between plant and animal transport. Plant transport is passive (no energy needed for water movement up), while animal circulation is active (heart pumps using energy).

14. (a) Allows gas exchange / allows carbon dioxide to enter and oxygen/water vapour to leave the leaf [1]

Teaching note: Stomata are pores primarily on the leaf underside that regulate gas exchange and transpiration.

(b) When guard cells take in water, they swell and curve apart, opening the stoma. When they lose water, they become flaccid and close together, closing the stoma. [2]

Marking breakdown:

• [1] Turgid/swollen guard cells → stoma open
• [1] Flaccid/shrunken guard cells → stoma closed

Teaching note: Guard cells are the only epidermal cells with chloroplasts (containing chlorophyll). They photosynthesize, producing glucose, which increases solute concentration, causing water to enter by osmosis. The inner wall is thicker, so they bend away from each other when turgid.

15. (a) The plant has not been watered / lacks water / the soil is too dry [1]

(b) Without enough water, the plant cannot transport water to the leaves. The leaves lose turgor pressure and wilt. Also, water is needed for photosynthesis — less water means less food can be made. [2]

Marking breakdown:

• [1] Less water reaching cells / loss of turgor pressure / cells become flaccid
• [1] Water is a raw material for photosynthesis

Teaching note: Turgor pressure keeps plant cells rigid. When water enters plant cells, they push against cell walls, keeping leaves firm. Without water, cells become flaccid (soft) and the leaf droops. Water is also one of the reactants in photosynthesis: CO₂ + H₂O → glucose + O₂.

Section D: Integration and Application

16. (a) No. The switch is open, so the circuit is broken. Electricity cannot flow around a broken circuit. [2]

Marking breakdown:

• [1] No / None of the bulbs will light up
• [1] Switch is open / circuit is broken / incomplete circuit / gap in circuit

(b) The remaining bulbs will not light up. In a series circuit, if one component is removed, the circuit is broken and electricity cannot flow to any other component. [2]

Marking breakdown:

• [1] No bulbs light / circuit stops working
• [1] All components in series / one break stops entire circuit / current path is interrupted

Teaching note: This is a disadvantage of series circuits. A single fault breaks everything. In parallel, other branches continue to work.

17. (a) 5 minutes [1]

(b) Working: Maximum heart rate − Resting heart rate = 120 − 72 = 48 [2]

Answer: 48 beats per minute

Marking breakdown:

• [1] Correct working shown (identifying 72 and 120, subtraction)
• [1] Correct answer with unit

(c) The body still needs extra oxygen to repay the "oxygen debt" / remove lactic acid built up during exercise. The heart continues working harder until the body returns to resting metabolic state. [2]

Marking breakdown:

• [1] Body still needs to remove extra CO₂ / lactic acid / repay oxygen debt
• [1] Metabolism is still elevated / muscles need continued blood flow to recover

Teaching note: During intense exercise, muscles may respire anaerobically (without oxygen), producing lactic acid. After exercise, extra oxygen is needed to break down this lactic acid. This is called "oxygen debt."

18. (a) Cotton wool has tiny spaces/pores between its fibres that allow water to pass through. Plastic wrap has no pores / is non-porous, so water cannot pass through. [2]

Marking breakdown:

• [1] Cotton wool is porous / has spaces / allows water through
• [1] Plastic wrap is non-porous / has no spaces / waterproof

(b) Plastic wrap. It does not allow water to pass through, so it will keep rain/water out and keep the wearer dry. [2]

Marking breakdown:

• [1] Plastic wrap
• [1] Waterproof / does not allow water through / keeps water out

Teaching note: This connects material properties to real-world applications. Porous materials allow fluids to pass; non-porous materials block them. The experiment demonstrates permeability differences.

19. (a) A vacuum contains no matter (no air particles). Heat cannot be transferred by conduction or convection through the vacuum because these need particles. This reduces heat loss from the hot drink. [2]

Marking breakdown:

• [1] Vacuum has no air / no particles / empty space
• [1] Prevents conduction and convection / heat cannot travel through vacuum easily / reduces heat transfer

(b) Plastic is a poor conductor of heat / an insulator. Metal is a good conductor and would allow heat to escape quickly from the drink to the surroundings. Plastic keeps the heat in. [2]

Marking breakdown:

• [1] Plastic is an insulator / poor conductor; metal is a good conductor
• [1] Metal would allow heat loss / plastic reduces heat loss / keeps drink hot longer

Teaching note: The vacuum flask uses multiple methods to reduce heat transfer: vacuum stops conduction/convection; shiny inner surface reflects radiation; plastic/b cork stopper reduces conduction at the opening.

20. (a) A: Evaporation [1] E: Transpiration [1]

(b) When water evaporates from leaf surfaces (transpiration), it creates a suction/pull that draws more water up from the roots through the xylem. This is called the transpiration pull. [2]

Marking breakdown:

• [1] Evaporation from leaves creates suction / pull / low pressure
• [1] This pulls water up from roots / through xylem

(c) The water cycle provides fresh water for drinking and for plants to absorb. It also distributes water around Earth, supports all living things that need water to survive, and helps regulate temperature. [2]

Marking breakdown:

• [1] Provides water for living things / drinking / plant growth / survival
• [1] Distributes water / part of ecosystems / maintains water supply / temperature regulation

Teaching note: Without the water cycle, water would collect in oceans and not return to land. All living things need water for life processes: as a solvent, transport medium, reactant in photosynthesis, temperature regulator, and habitat.

END OF ANSWER KEY