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Primary 6 PSLE Science Practice Paper 3
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TuitionGoWhere Practice Paper - Science Primary 6 PSLE (Answer Key)
TuitionGoWhere Practice Paper (AI) — Version 3
Subject: Science
Level: Primary 6 PSLE
Paper: Practice Paper (Full)
Duration: 1 h 45 min
Total Marks: 100
Section A: Multiple-Choice Questions (56 marks)
| Question | Answer | Explanation |
|---|---|---|
| 1 | (1) | The grasshopper eats grass (prey to grass) and is eaten by the frog (predator to frog). |
| 2 | (2) | Fungi (e.g., mould, yeast) do not make their own food, reproduce by spores, and lack chlorophyll. Organism Q matches these characteristics. |
| 3 | (3) | Mushroom is a fungus, not a plant. Fern, moss, and conifer are non-flowering plants. |
| 4 | (3) | The nucleus contains genetic material (DNA) and controls all cellular activities. |
| 5 | (2) | Bacteria are microscopic and can only be seen under a microscope. Ali is incorrect (some microorganisms are beneficial). Cindy is incorrect (yeast is a fungus). Devi is incorrect (mould reproduces by spores). |
| 6 | (1) | The egg stage does not feed. Larva, pupa, and adult stages feed (though pupa feeds minimally/does not feed in some species; at PSLE level, egg is the clear non-feeding stage). |
| 7 | (3) | Electrical wires need to conduct electricity (Yes) and be flexible (Yes) for installation. Material C fits. Material D conducts electricity but is not flexible. |
| 8 | (3) | Oxygen at room temperature has no definite volume or shape → Gas. |
| 9 | (1) | The steel paper clip becomes a temporary magnet by magnetic induction, with the near end developing opposite polarity to the magnet's pole, causing attraction. |
| 10 | (3) | Object Y rests on the bottom, meaning its density is greater than water (highest among the four). W floats (density < water), X is suspended (density ≈ water), Z is partially submerged (density < water but > W). |
| 11 | (1) | In a series circuit with identical bulbs, current is the same through both, so they light up with equal brightness. |
| 12 | (2) | The plateau at 100°C (10–15 min) represents boiling (change of state from liquid to gas). The first rise (0–10 min) is heating of solid/liquid; the plateau at 0°C would be melting, but the graph shows rising from 0°C, so 0–10 min is heating, not a change of state. |
| 13 | (2) | Condensation is the change of state from gas (water vapour) to liquid (water droplets). |
| 14 | (2) | Without light, photosynthesis cannot occur, so no starch is produced. Iodine solution remains yellow-brown (no blue-black colour). |
| 15 | (3) | Stomata (pores on the leaf surface) allow gaseous exchange (CO₂ in, O₂ out). |
| 16 | (3) | Gaseous exchange (oxygen and carbon dioxide) occurs in the alveoli (air sacs) where capillaries are in close contact. |
| 17 | (1) | Energy transfer between trophic levels is ~10%. Grass (10,000 J) → Grasshopper (1,000 J) → Frog (100 J) → Snake (10 J). |
| 18 | (3) | Structural adaptation: a physical feature of an organism's body (cactus thick stems for water storage). (1) and (4) are behavioural adaptations. (2) is a physiological/behavioural response. |
| 19 | (2) | A fixed pulley changes the direction of force only; it does not reduce the effort needed. Effort = Load = 50 N (ignoring friction). |
| 20 | (2) | Extension per 2 N = 4 cm (from 10→14, 14→18, 18→22). For 8 N (4 × 2 N), extension = 4 × 4 cm = 16 cm. Length = 10 cm + 16 cm = 26 cm. |
| 21 | (1) | Law of reflection: angle of incidence = angle of reflection = 30°. |
| 22 | (1) | Battery stores chemical energy → converted to electrical energy in circuit → bulb converts to light and heat energy. |
| 23 | (2) | Principle of moments: Load × Load arm = Effort × Effort arm. 40 N × 0.5 m = Effort × 1.0 m → Effort = 20 N. |
| 24 | (4) | Higher temperature increases the rate of dissolving (kinetic energy of water molecules increases). |
| 25 | (3) | Male gametes (pollen grains) are produced in the anther (part of the stamen). |
| 26 | (3) | Gravitational force acts on all objects with mass, regardless of contact. (1) False: non-living things exert forces. (2) False: friction opposes motion. (4) False: magnetic force acts through non-magnetic materials (e.g., glass, plastic). |
| 27 | (3) | [Assuming diagram shows two bulbs in parallel, then in series with third] Bulbs in parallel share current; the series bulb gets full current. The series bulb is brightest; parallel bulbs are dimmer but equal to each other. |
| 28 | (4) | [Assuming diagram shows electromagnet with more coils/voltage] Strength of electromagnet increases with number of coils, current (voltage), and using a soft iron core. |
Section B: Open-Ended Questions (44 marks)
29. Classification and Characteristics of Living Things [4 marks]
a) State two characteristics of living things shown by the mimosa plant when its leaves fold upon touching. [2]
Answer:
- Sensitivity / Response to stimuli – The plant detects the touch (stimulus) and responds by folding its leaves.
- Movement – The folding of leaves is a visible movement in response to the stimulus.
(Accept: "Respond to changes in the environment" and "Move")
b) The diagram below shows a young plant growing from a seed.
Image pending generation: diagram for Q29b.
Explain why the root grows downwards and the shoot grows upwards. [2]
Answer:
- The root grows downwards due to positive geotropism (gravitropism) — it grows in the direction of gravitational pull to anchor the plant and absorb water and minerals from the soil.
- The shoot grows upwards due to negative geotropism — it grows against gravity to reach sunlight for photosynthesis.
30. Cells and Microscopy [3 marks]
a) Complete the table below to show the function of each cell part. [2]
| Cell Part | Function |
|---|---|
| Cell membrane | Controls the movement of substances in and out of the cell. |
| Chloroplast | Contains chlorophyll to trap light energy for photosynthesis. |
| Cytoplasm | Jelly-like substance where most cellular activities / chemical reactions take place. |
| Nucleus | Controls all activities of the cell; contains genetic information (DNA). |
b) State one difference between a plant cell and an animal cell. [1]
Answer: Plant cells have a cell wall (and chloroplasts, large central vacuole), while animal cells do not.
(Any one correct difference: cell wall, chloroplasts, large vacuole, regular shape vs irregular shape)
31. Matter and Its Properties [4 marks]
a) The diagram below shows the arrangement of particles in three states of matter.
Image pending generation: diagram for Q31a.
Complete the table below using the words: solid, liquid, gas. [2]
| Description | State of Matter |
|---|---|
| Particles are tightly packed in a fixed arrangement. | Solid |
| Particles are close together but can slide past one another. | Liquid |
| Particles are far apart and move freely in all directions. | Gas |
b) Substance X has a melting point of 50°C and a boiling point of 200°C. What is the state of substance X at 150°C? Explain your answer. [2]
Answer: Liquid.
At 150°C, the temperature is above the melting point (50°C) so it has melted, but below the boiling point (200°C) so it has not yet boiled. Hence, it exists as a liquid.
32. Heat and Temperature [4 marks]
a) The diagram below shows a metal spoon placed in a cup of hot tea.
Image pending generation: diagram for Q32a.
The handle of the metal spoon becomes hot after a while. Name the process of heat transfer and explain how it occurs in the metal spoon. [2]
Answer: Conduction.
Metal is a good conductor of heat. When the spoon is in hot tea, the particles at the immersed end gain kinetic energy and vibrate more vigorously. They collide with neighbouring particles, transferring kinetic energy along the spoon to the handle.
b) A beaker of water at 80°C is left in a room at 30°C. After 30 minutes, the water temperature drops to 50°C. Explain why the temperature of the water decreases. [2]
Answer: Heat is lost from the hotter water to the cooler surrounding air through the processes of conduction, convection, and radiation until thermal equilibrium is approached. The water loses thermal energy, so its temperature decreases.
33. Light and Shadows [4 marks]
a) The diagram below shows a torch shining on a wooden block. A screen is placed behind the block.
Image pending generation: diagram for Q33a.
A shadow is formed on the screen. State two properties of light shown by the formation of this shadow. [2]
Answer:
- Light travels in straight lines.
- Light is blocked by opaque objects (wooden block does not allow light to pass through).
b) The torch is moved closer to the wooden block. What happens to the size of the shadow on the screen? Explain your answer. [2]
Answer: The shadow becomes larger.
When the light source is closer to the object, the light rays diverge more, causing the opaque block to block a larger area on the screen, resulting in a bigger shadow.
34. Electrical Systems [5 marks]
a) The diagram below shows a circuit with two bulbs, B1 and B2, and two switches, S1 and S2.
Image pending generation: diagram for Q34a.
Complete the table below to show whether each bulb lights up (✓) or does not light up (✗). [2]
| Switch S1 | Switch S2 | Bulb B1 | Bulb B2 |
|---|---|---|---|
| Closed | Open | ✓ | ✗ |
| Open | Closed | ✗ | ✓ |
| Closed | Closed | ✓ | ✓ |
| Open | Open | ✗ | ✗ |
b) In the circuit above, the bulbs are connected in parallel. State one advantage of connecting bulbs in parallel compared to in series. [1]
Answer: If one bulb fuses (blows), the other bulb still lights up because the circuit for the other bulb remains complete.
(Accept: Each bulb gets the full voltage from the battery / bulbs are brighter than in series / each bulb can be controlled independently)
c) The diagram below shows a circuit with a battery, a switch, a bulb, and a conductor X.
Image pending generation: diagram for Q34c.
The bulb lights up brightly when conductor X is a copper rod. When conductor X is replaced with a wooden rod, the bulb does not light up. Explain why. [2]
Answer: Copper is a good conductor of electricity — it allows electric current to flow through the closed circuit, lighting the bulb.
Wood is an insulator (poor conductor of electricity) — it does not allow electric current to flow, so the circuit is incomplete (open), and the bulb does not light up.
35. Forces and Energy [5 marks]
a) The diagram below shows a ball at position A on a frictionless track. It is released from rest and moves to position B, then up to position C.
Image pending generation: diagram for Q35a.
i) At which position (A, B, or C) does the ball have the greatest kinetic energy? [1]
Answer: Position B (lowest point).
ii) Explain your answer in terms of energy conversion. [2]
Answer: At position A, the ball has maximum gravitational potential energy and zero kinetic energy (released from rest). As it rolls down to B, gravitational potential energy is converted to kinetic energy. At B (lowest height), potential energy is minimum, so kinetic energy is maximum. At C, some kinetic energy is converted back to potential energy as the ball rises.
b) A box of mass 5 kg is pushed across a horizontal floor with a constant force of 20 N. The frictional force between the box and the floor is 8 N. Calculate the acceleration of the box. [2]
Answer:
Net force = Applied force – Frictional force = 20 N – 8 N = 12 N
Using Newton’s Second Law: ( F = ma )
( a = \frac{F}{m} = \frac{12 \text{ N}}{5 \text{ kg}} = \mathbf{2.4 \text{ m/s}^2} )
36. Plant Transport System [4 marks]
a) The diagram below shows a cross-section of a stem.
Image pending generation: diagram for Q36a.
Name the parts labelled X and Y and state one function of each. [2]
(Assuming X = Xylem, Y = Phloem based on standard diagram)
Answer:
- X: Xylem – Transports water and mineral salts from roots to other parts of the plant. Provides support to the plant.
- Y: Phloem – Transports food (sugar/sucrose) made in the leaves during photosynthesis to other parts of the plant (roots, stems, fruits, seeds).
b) A ring of bark (including phloem) is removed from a tree trunk as shown below.
Image pending generation: diagram for Q36b.
After a few weeks, a swelling appears above the cut. Explain why. [2]
Answer: The phloem (which transports food) is removed in the ring of bark. Food made in the leaves cannot be transported downwards past the cut, so it accumulates above the cut, causing the swelling. The xylem (water transport) remains intact, so the tree may survive for a while.
37. Human Circulatory System [4 marks]
a) The diagram below shows the human heart.
Image pending generation: diagram for Q37a.
Name the chamber that pumps oxygen-rich blood to the rest of the body. [1]
Answer: Left ventricle
b) The table below shows the composition of blood in the pulmonary artery and pulmonary vein.
| Blood Vessel | Oxygen Content | Carbon Dioxide Content |
|---|---|---|
| Pulmonary artery | Low | High |
| Pulmonary vein | High | Low |
Explain why the blood in the pulmonary artery has low oxygen content. [2]
Answer: The pulmonary artery carries deoxygenated blood from the right ventricle to the lungs to pick up oxygen. This blood has just returned from the body where oxygen was used up by cells for respiration, so it has low oxygen and high carbon dioxide.
c) State one function of the valves in the heart. [1]
Answer: Valves prevent the backflow of blood, ensuring it flows in one direction only (e.g., from atria to ventricles, from ventricles to arteries).
38. Reproduction in Plants [4 marks]
a) The diagram below shows the process of pollination and fertilisation in a flowering plant.
Image pending generation: diagram for Q38a.
i) Name the process where the pollen grain lands on the stigma. [1]
Answer: Pollination
ii) Describe what happens after pollination until a seed is formed. [3]
Answer:
- The pollen grain germinates and grows a pollen tube down the style into the ovary.
- The pollen tube enters the ovule through the micropyle.
- The male gamete (from the pollen tube) fuses with the female gamete (in the ovule) — this is fertilisation.
- The fertilised ovule develops into a seed, and the ovary develops into the fruit.
39. Adaptations and Environment [4 marks]
a) The diagram below shows a polar bear and a camel.
Image pending generation: diagram for Q39a.
State one structural adaptation of the polar bear for keeping warm and explain how it helps. [2]
Answer: Thick fur (or thick layer of fat/blubber).
The thick fur traps a layer of air close to the skin. Air is a poor conductor of heat, so this reduces heat loss from the bear’s body to the cold surroundings, keeping it warm.
b) The camel stores fat in its hump. State two ways this adaptation helps the camel survive in the desert. [2]
Answer:
- The fat can be broken down to release energy and water (metabolic water) when food and water are scarce.
- Concentrating fat in the hump reduces insulation over the rest of the body, allowing better heat loss during the hot day.
40. Environmental Interactions [4 marks]
a) The graph below shows the population of organism X and organism Y in a habitat over time.
Image pending generation: graph for Q40a.
Based on the graph, which organism is the predator and which is the prey? Explain your answer. [2]
Answer: Organism X is the predator; Organism Y is the prey.
The predator population peaks after the prey population peaks. When prey (Y) is abundant, predators (X) have more food, so their population increases. As predators increase, they eat more prey, causing the prey population to decrease. Then predator population decreases due to lack of food.
b) A new predator of organism Y is introduced into the habitat. Predict how the population of organism X will change in the short term. Explain your answer. [2]
Answer: The population of organism X will decrease.
The new predator competes with organism X for the same prey (organism Y). With more predators eating organism Y, the population of Y will decrease, leaving less food for organism X, so its population will drop.
End of Answer Key
Marking Notes:
- Section A: 2 marks per question (56 marks total).
- Section B: Marks as indicated (44 marks total).
- Accept scientifically accurate alternative phrasing.
- For calculation questions, award method marks if final answer is wrong but working is correct.
- Diagrams referenced are described in the question paper; students should refer to those.