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Primary 6 PSLE Science Systems Quiz
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Questions
Primary 6 PSLE Science Quiz - Systems
Name: ___________________________
Class: Primary 6 _______
Date: _______________
Score: _______ / 40
Duration: 45 minutes
Total Marks: 40
Instructions:
- Answer all questions.
- For Section A, choose the correct option and write its letter (A, B, C, or D) in the brackets provided.
- For Section B and C, write your answers in the spaces provided.
- The number of marks for each question is shown in brackets [ ].
- Read each question carefully and manage your time wisely.
Section A: Multiple-Choice Questions (10 × 1 mark = 10 marks)
1. Which of the following systems is correctly matched with its main function? [1]
| System | Main Function |
|---|---|
| A. Respiratory system | Transports nutrients and oxygen around the body |
| B. Circulatory system | Removes carbon dioxide from the blood |
| C. Digestive system | Breaks down food into simpler substances |
| D. Skeletal system | Controls all body activities |
Answer: (____)
2. The diagram below shows the human digestive system.
<image_placeholder> id: Q2-fig1 type: diagram linked_question: Q2 description: Human digestive system with parts labelled P, Q, R, S. P = mouth, Q = stomach, R = small intestine, S = large intestine. labels: P, Q, R, S values: None must_show: Clear labels for mouth, stomach, small intestine, large intestine with arrows pointing to each part. </image_placeholder>
In which labelled part does most absorption of digested food into the blood take place? [1]
A. P
B. Q
C. R
D. S
Answer: (____)
3. The table below shows the composition of inhaled and exhaled air.
| Gas | Inhaled Air (%) | Exhaled Air (%) |
|---|---|---|
| Oxygen | 21 | 16 |
| Carbon dioxide | 0.04 | 4 |
| Nitrogen | 78 | 78 |
Which of the following statements is correct? [1]
A. The percentage of nitrogen increases during respiration.
B. Oxygen is used up and carbon dioxide is produced during respiration.
C. The total percentage of gases changes after respiration.
D. Carbon dioxide is removed from the air during respiration.
Answer: (____)
4. A student places a plant in a dark cupboard for 48 hours. He then covers one leaf with black paper and places the plant in sunlight for 6 hours. After testing the covered and uncovered leaves for starch, which result is expected? [1]
A. Both leaves turn blue-black with iodine solution.
B. Only the covered leaf turns blue-black with iodine solution.
C. Only the uncovered leaf turns blue-black with iodine solution.
D. Neither leaf turns blue-black with iodine solution.
Answer: (____)
5. The diagram below shows a food web in a garden ecosystem.
<image_placeholder> id: Q5-fig1 type: diagram linked_question: Q5 description: Food web with grass, grasshopper, frog, snake, hawk, mouse, and owl. Arrows show energy flow from grass to grasshopper and mouse; grasshopper to frog; frog to snake; snake to hawk; mouse to owl and snake. labels: Grass, Grasshopper, Frog, Snake, Hawk, Mouse, Owl values: None must_show: Clear arrows showing energy transfer direction between all organisms listed. </image_placeholder>
How many food chains in this food web have exactly three organisms? [1]
A. 2
B. 3
C. 4
D. 5
Answer: (____)
6. Which of the following shows the correct order of energy conversion in a hydroelectric power station? [1]
A. Gravitational potential energy → Electrical energy → Kinetic energy
B. Kinetic energy → Gravitational potential energy → Electrical energy
C. Gravitational potential energy → Kinetic energy → Electrical energy
D. Electrical energy → Kinetic energy → Gravitational potential energy
Answer: (____)
7. The diagram below shows a spring balance being used to measure the weight of an object.
<image_placeholder> id: Q7-fig1 type: diagram linked_question: Q7 description: Spring balance hanging vertically with a 200 g mass attached. Spring is stretched. Scale reads 2 N. labels: Spring balance, 200 g mass, scale reading 2 N values: Mass = 200 g, Scale reading = 2 N must_show: Spring stretched under weight, scale marking visible. </image_placeholder>
If the same object is taken to the Moon where gravitational force is 1/6 that of Earth, what would be the new reading on the spring balance? [1]
A. 0.33 N
B. 2 N
C. 12 N
D. 0 N
Answer: (____)
8. A block of wood is pushed across four different surfaces with the same force. On which surface will the block travel the furthest before stopping? [1]
A. Carpet
B. Sandpaper
C. Polished marble
D. Grass
Answer: (____)
9. The diagram below shows a simple electrical circuit.
<image_placeholder> id: Q9-fig1 type: diagram linked_question: Q9 description: Simple circuit with battery, switch, and bulb connected in series. Switch is open. labels: Battery, Switch (open), Bulb values: None must_show: Open switch, single bulb, battery with + and - terminals. </image_placeholder>
When the switch is closed, which energy conversion takes place in the bulb? [1]
A. Electrical energy → Light energy only
B. Electrical energy → Heat energy only
C. Electrical energy → Light energy + Heat energy
D. Chemical energy → Electrical energy → Light energy
Answer: (____)
10. Which of the following adaptations helps a plant survive in a dry environment? [1]
A. Broad, thin leaves
B. Deep, widespread roots
C. Brightly coloured flowers
D. Thin, flexible stems
Answer: (____)
Section B: Structured Questions (10 × 2 marks = 20 marks)
11. The diagram below shows the human respiratory system.
<image_placeholder> id: Q11-fig1 type: diagram linked_question: Q11 description: Human respiratory system with parts labelled A, B, C, D. A = nose, B = trachea, C = bronchus, D = alveolus. labels: A, B, C, D values: None must_show: Clear labels for nose, trachea, bronchus, alveolus. </image_placeholder>
(a) Name the part labelled C. [1]
(b) Explain how the structure of part D makes it efficient for gaseous exchange. [1]
12. The table below shows the amount of undigested food leaving the small intestine and entering the large intestine for three different food types.
| Food Type | Mass of Undigested Food Entering Large Intestine (g) |
|---|---|
| Rice | 5 |
| Chicken | 15 |
| Cabbage | 40 |
(a) Which food type leaves the most undigested food? [1]
(b) Explain why this food type leaves more undigested food than the others. [1]
13. A student sets up an experiment to investigate photosynthesis. She places a water plant in a test tube filled with water and shines a lamp on it. She counts the number of bubbles produced per minute at different distances of the lamp from the test tube.
| Distance of Lamp from Test Tube (cm) | Number of Bubbles per Minute |
|---|---|
| 10 | 48 |
| 20 | 32 |
| 30 | 18 |
| 40 | 8 |
| 50 | 2 |
(a) State the relationship between the distance of the lamp and the number of bubbles produced per minute. [1]
(b) The bubbles produced are oxygen. Explain why the number of bubbles decreases as the lamp is moved further away. [1]
14. The diagram below shows a food chain in a pond ecosystem.
<image_placeholder> id: Q14-fig1 type: diagram linked_question: Q14 description: Food chain: Algae → Water flea → Small fish → Large fish. Arrows point from left to right. labels: Algae, Water flea, Small fish, Large fish values: None must_show: Clear arrows showing energy flow direction. </image_placeholder>
(a) Which organism is the producer? [1]
(b) If a pollutant enters the pond and kills most of the algae, explain what will happen to the population of large fish over time. [1]
15. The diagram below shows a boy pushing a heavy box across a floor.
<image_placeholder> id: Q15-fig1 type: diagram linked_question: Q15 description: Boy pushing a box to the right. Arrow shows push force. Friction arrow points left opposing motion. Weight arrow points down. Normal force arrow points up. labels: Push force, Friction, Weight, Normal force values: None must_show: Four force arrows labelled clearly. </image_placeholder>
(a) Name the force that opposes the motion of the box. [1]
(b) The boy pushes the box with a force of 50 N. The frictional force is 30 N. What is the resultant force acting on the box? [1]
16. A spring stretches 2 cm when a 100 g mass is hung from it. The spring stretches 6 cm when a 300 g mass is hung from it.
(a) State the relationship between the mass hung and the extension of the spring. [1]
(b) Predict the extension of the spring when a 400 g mass is hung from it. [1]
17. The diagram below shows a simple circuit with two identical bulbs connected in series.
<image_placeholder> id: Q17-fig1 type: diagram linked_question: Q17 description: Circuit with battery, switch, and two identical bulbs in series. Switch is closed. labels: Battery, Switch (closed), Bulb 1, Bulb 2 values: None must_show: Two bulbs in series, closed switch. </image_placeholder>
(a) If one bulb fuses (blows), what happens to the other bulb? [1]
(b) Explain your answer in (a). [1]
18. The table below shows the boiling points of four substances.
| Substance | Boiling Point (°C) |
|---|---|
| W | -196 |
| X | -10 |
| Y | 78 |
| Z | 350 |
(a) At room temperature (25°C), which substance(s) exist as a gas? [1]
(b) Explain your answer. [1]
19. A plant is placed in a sealed transparent box with a light source. The carbon dioxide concentration in the box is measured over 12 hours.
<image_placeholder> id: Q19-fig1 type: graph linked_question: Q19 description: Line graph showing CO2 concentration vs time. X-axis: Time (hours) 0 to 12. Y-axis: CO2 concentration (arbitrary units). Line decreases from 0 to 6 hours, then increases from 6 to 12 hours. labels: Time (hours), CO2 concentration values: 0h: high, 6h: low, 12h: high must_show: Clear decreasing then increasing trend with labelled axes. </image_placeholder>
(a) During which time period does photosynthesis occur at a faster rate than respiration? [1]
(b) Explain why the carbon dioxide concentration increases from 6 to 12 hours. [1]
20. The diagram below shows the same garden food web as Question 5.
<image_placeholder> id: Q20-fig1 type: diagram linked_question: Q20 description: Food web with grass, grasshopper, frog, snake, hawk, mouse, and owl. Arrows show energy flow from grass to grasshopper and mouse; grasshopper to frog; frog to snake; snake to hawk; mouse to owl and snake. labels: Grass, Grasshopper, Frog, Snake, Hawk, Mouse, Owl values: None must_show: Clear arrows showing energy transfer direction between all organisms listed. </image_placeholder>
(a) How many food chains in this food web include the snake? [1]
(b) If all the frogs are removed from this food web, state what will happen to the grasshopper population and the snake population. [1]
Answers
Primary 6 PSLE Science Quiz - Systems (Answer Key)
Total Marks: 40
Section A: Multiple-Choice Questions (10 marks)
1. Answer: C
Explanation: The digestive system breaks down food into simpler substances that can be absorbed. The respiratory system exchanges gases (not transport), the circulatory system transports substances (not remove CO₂ from blood directly), and the skeletal system provides support/protection (not control body activities — that's the nervous system).
2. Answer: C
Explanation: The small intestine (R) is where most absorption of digested nutrients into the bloodstream occurs, due to its villi and microvilli that greatly increase surface area. The mouth (P) begins mechanical/chemical digestion, the stomach (Q) continues digestion, and the large intestine (S) absorbs water.
3. Answer: B
Explanation: During respiration, oxygen is consumed (21% → 16%) and carbon dioxide is produced (0.04% → 4%). Nitrogen percentage remains unchanged (78%) as it is inert. The total percentage of gases remains ~100%.
4. Answer: C
Explanation: The plant in the dark for 48 hours depletes its starch reserves. Only the uncovered leaf receives light for photosynthesis to produce new starch, which tests positive (blue-black) with iodine. The covered leaf cannot photosynthesise.
5. Answer: B
Explanation: Food chains with exactly 3 organisms: (1) Grass → Grasshopper → Frog, (2) Grass → Mouse → Owl, (3) Grass → Mouse → Snake. Chains with 4+ organisms: Grass → Grasshopper → Frog → Snake → Hawk (4). Based on the described web: Grass → Grasshopper → Frog, Grass → Mouse → Owl, Grass → Mouse → Snake = 3 chains.
6. Answer: C
Explanation: Water at height has gravitational potential energy → flows down gaining kinetic energy → turns turbine (kinetic) → generator produces electrical energy.
7. Answer: A
Explanation: Weight = mass × gravitational field strength. On Moon, g is 1/6 of Earth. Spring balance measures weight (force). 2 N × 1/6 = 0.33 N. Mass remains 200 g but weight changes.
8. Answer: C
Explanation: Polished marble has the least friction among the options. Less friction means less opposing force, so the block travels furthest before stopping.
9. Answer: C
Explanation: In a filament bulb, electrical energy is converted to both light energy and heat energy (most energy becomes heat). This is why bulbs get hot.
10. Answer: B
Explanation: Deep, widespread roots help plants absorb water from a large area and deep underground, an adaptation for dry environments. Broad leaves increase water loss, bright flowers attract pollinators, thin stems provide flexibility but not water conservation.
Section B: Structured Questions (20 marks)
11.
(a) Answer: Bronchus / Bronchial tube [1]
(b) Answer: The alveolus has a thin, moist, one-cell-thick wall and a large surface area due to its spherical shape and numerous alveoli, allowing rapid diffusion of gases. [1]
Marking notes: Must mention thin wall (1 cell thick), moist surface, and large surface area for full mark.
12.
(a) Answer: Cabbage [1]
(b) Answer: Cabbage contains cellulose (dietary fibre) which humans cannot digest because we lack the enzyme cellulase. Rice and chicken are mainly carbohydrates and proteins which are digested. [1]
Marking notes: Key concept: humans cannot digest cellulose/fibre.
13.
(a) Answer: As the distance of the lamp from the test tube increases, the number of bubbles produced per minute decreases. [1]
(b) Answer: Light intensity decreases with distance. Lower light intensity reduces the rate of photosynthesis, so less oxygen is produced. [1]
Marking notes: Must link distance → light intensity → photosynthesis rate → oxygen bubbles.
14.
(a) Answer: Algae [1]
(b) Answer: Algae are the producers/food source. If algae die, water fleas starve, then small fish starve, then large fish starve. The large fish population will decrease due to lack of food energy transferred up the food chain. [1]
Marking notes: Must show understanding of energy flow disruption up the chain.
15.
(a) Answer: Friction / Frictional force [1]
(b) Answer: Resultant force = 50 N – 30 N = 20 N (in direction of push). [1]
Marking notes: Subtract opposing forces; direction same as larger force.
16.
(a) Answer: The extension of the spring is directly proportional to the mass hung (or: as mass increases, extension increases proportionally). [1]
(b) Answer: 8 cm [1]
Explanation: 100 g → 2 cm, so 400 g → 4 × 2 cm = 8 cm (Hooke's Law: extension ∝ force/mass within elastic limit).
17.
(a) Answer: The other bulb will not light up / will go out. [1]
(b) Answer: In a series circuit, there is only one path for current. If one bulb fuses, the circuit is broken/open, so current cannot flow through the other bulb. [1]
Marking notes: Must mention broken circuit / open circuit / current cannot flow.
18.
(a) Answer: Substances W and X [1]
(b) Answer: At room temperature (25°C), substances with boiling points below 25°C exist as gases. W (-196°C) and X (-10°C) have boiling points below 25°C, so they are gases. Y (78°C) and Z (350°C) are liquids/solids. [1]
Marking notes: Compare boiling point to room temperature.
19.
(a) Answer: 0–6 hours [1]
(b) Answer: From 6–12 hours, it becomes dark (no light). Photosynthesis stops but respiration continues, releasing carbon dioxide, so CO₂ concentration increases. [1]
Marking notes: Must mention photosynthesis stops in dark, respiration continues.
20.
(a) Answer: 3 [1]
Explanation: Food chains including snake: (1) Grass → Grasshopper → Frog → Snake, (2) Grass → Grasshopper → Frog → Snake → Hawk, (3) Grass → Mouse → Snake.
(b) Answer: Grasshopper population will increase (no frogs to eat them). Snake population will decrease (lose frogs as food source, though they still have mice). [1]
Marking notes: Both effects must be stated correctly.