Question 1

Which one of the following diagrams correctly shows the development of a flowering plant?

Accepted Answer

4. fertilisation → seed → plant → flower → seed. The life cycle of a flowering plant begins with a seed that germinates into a plant, which grows and produces flowers. After fertilisation, the flower develops into a fruit containing seeds, completing the cycle: seed → plant → flower → (fertilisation) → seed.

Question 2

Which one of the following correctly states the male and female reproductive cells in humans?

Accepted Answer

1. Male: sperm, Female: egg cell. In humans, the male reproductive cell is the sperm and the female reproductive cell is the egg cell (ovum). Pollen grains and ovules are the reproductive cells of plants, not humans.

Question 3

Susan cut out the food-carrying tubes of a plant. One week later, she observed the plant and drew her observation in the diagram shown below. Which one of the following correctly explains her observation of the stem after one week?

Accepted Answer

2. Food cannot be transported from the leaves to the roots so food is stored at the part of the stem above the cut.. Food-carrying tubes (phloem) transport food made in the leaves to the rest of the plant including the roots. When these tubes are cut, food made in the leaves cannot pass below the cut, so it accumulates above the cut causing the stem to swell into a ring.

Question 4

The graph below shows the changes in Joshua's heart rate before, during and after running. He was running at the same speed throughout. At which points did Joshua start and stop running?

Accepted Answer

1. Started: Point D, Stopped: Point F. Joshua's heart rate is constant at 70 bpm at point D (before running). Heart rate rises from D to E as he starts running. From E to F heart rate stays at 110 bpm (still running at the same speed). At F heart rate begins to fall, meaning he stops running at F. So he started at D and stopped at F.

Question 5

Study the diagram of the cell below carefully. Which of the following shows the correct function of parts, X, Y and Z?

Accepted Answer

4. X: controls all the activities in the cell; Y: supports and gives the cell a regular shape; Z: contains chlorophyll that traps light to make food. This is a plant cell. Part X (the dark filled circle inside the cell) is the nucleus, which controls all the activities in the cell. Part Y (the outer rectangular boundary) is the cell wall, which supports and gives the plant cell a regular shape. Part Z (the small oval bodies inside) are the chloroplasts, which contain chlorophyll to trap light to make food.

Question 6

Thomas observed the life cycle of an insect over some time and recorded his observations in the diagram shown below. Based on his observations, he made the following statements. A) The insect reproduces by laying eggs. B) The insect moults during its nymph stage. C) The insect takes five blood meals before it becomes an adult. Which of his statement(s) is/are correct?

Accepted Answer

4. A, B and C. A is correct — the diagram shows that adult females lay eggs. B is correct — each nymph stage shows the insect takes a blood meal then moults. C is correct — counting the nymph stages, the insect takes five blood meals (one at each of the five nymph stages) before becoming an adult. All three statements are correct.

Question 7

The life cycle of a plant is shown in the diagram below. Which of the following correctly describes the possible observations at stages E, F and G?

Accepted Answer

3. E: root and shoot appear; F: flower appears; G: fruit appears. Starting from the seed, the next stage E is when the seed germinates so root and shoot appear. The plant then grows and produces a flower at stage F. After pollination and fertilisation, the flower develops into a fruit at stage G, which contains seeds, completing the cycle.

Question 8

The diagram below represents the human digestive system. Which parts of the digestive system produce digestive juices?

Accepted Answer

3. A, C and D only. In the human digestive system, the mouth (A) produces saliva, the stomach (C) produces gastric juices, and the small intestine (D) receives digestive juices from the pancreas and liver and produces its own. Parts B (oesophagus) and E (large intestine) do not produce digestive juices.

Question 9

Geraldine made the following statements about the functions of the human skeletal system. A) It gives the body its shape. B) It protects some organs in the body. C) It carries digested food to all parts of the body. D) It works with the muscular system to enable the body to move. Which of the statements made by Geraldine are true?

Accepted Answer

3. A, B and D only. A is true — the skeleton gives the body its shape. B is true — bones such as the skull and ribcage protect organs. D is true — bones work with muscles to enable movement. C is false — carrying digested food is the function of the circulatory system, not the skeletal system.

Question 10

Study the diagram below. P, Q, R and S represent four different processes that involve changes in the state of water. Which of these processes, P, Q, R or S, take place at a fixed temperature?

Accepted Answer

2. P, Q and S only. P (water → steam, boiling) takes place at a fixed temperature (100°C). Q (water → ice, freezing) takes place at a fixed temperature (0°C). S (ice → water, melting) takes place at a fixed temperature (0°C). R (steam → water, condensation) does NOT take place at a fixed temperature. So P, Q and S take place at fixed temperatures.

Question 11

Lindy set up an experiment to collect water in the basin, as shown in the diagram below. She placed the set-up under the sun for two hours. She observed that there was 100ml of water collected in the basin after two hours. Which one of the following changes to the set-up will enable Lindy to collect the most amount of water in the basin?

Accepted Answer

1. Increase the width of the basin.. Increasing the width of the basin increases the exposed surface area of the saltwater tanks (with the basin between two saltwater tanks of larger separation, more water vapour is collected). Wait — re-reading: the basin sits between two saltwater tanks under a curved metal sheet. Increasing the width of the basin means more surface area for water vapour to condense on the metal sheet and drip into the basin. So increasing the width of the basin collects the most water.

Question 12

Study the diagram of the water cycle below. X and Y are two processes that take place in the water cycle. Which of the following statements about the water cycle are correct? A) The water vapour lost heat during process Y. B) Process X does not take place at a fixed temperature. C) There is a change in the state of water during process X. D) Process Y occurs when there is a temperature difference.

Accepted Answer

4. A, B, C and D. Process Y is condensation (water vapour → clouds), which involves water vapour losing heat (A true) and only occurs when there is a temperature difference (cooler air) (D true). Process X is evaporation (sea → water vapour), which does NOT take place at a fixed temperature (B true) and involves a change of state from liquid to gas (C true). All four are correct.

Question 13

Which one of the following actions help to conserve water?

Accepted Answer

4. Taking a 5 minute shower instead of a bath in the fully-filled bathtub.. A 5-minute shower uses much less water than filling an entire bathtub, so it conserves water. Using a hose (1) wastes water, switching off a fan (2) conserves electricity not water, and using running water to rinse the mouth (3) wastes water.

Question 14

Sophie set up 4 circuits, A, B, C and D, with identical bulbs and working batteries as shown below. In which of the above circuits will the bulb light up?

Accepted Answer

2. B and C only. For a bulb to light up, the circuit must form a complete loop with both terminals of the battery connected through the bulb. Circuits B and C show complete circuits where the bulb is connected from the + terminal back to the − terminal of the battery. Circuits A and D are incomplete (only one terminal connected), so the bulbs do not light up.

Question 15

A circuit is set up using 2 new batteries, 3 working identical bulbs, B1, B2 and B3 and 3 switches, S1 and S2, as shown in the diagram below. Which of the following will allow only B1 and B3 to light up?

Accepted Answer

4. S1: closed, S2: closed, S3: open. For B1 and B3 to light up, S1 must be closed (completes the main loop through B1 and B3). For B2 to NOT light up, S3 must be open (breaks the branch with B2). S2 closed provides a bypass shorting around B2 path, allowing current to flow to B3 and B1 without going through B2. So S1: closed, S2: closed, S3: open.

Question 16

Jamal set up a circuit as shown below. He observed that all the bulbs did not light up. Which of the following shows why all the bulbs in Jamal's circuit did not light up?

Accepted Answer

2. There is no battery in the circuit.. The circuit has 4 bulbs and a metal rod but no battery (source of electrical energy). Without a battery, there is no source of electricity, so the bulbs cannot light up. A switch is not necessary for bulbs to light up, and a metal rod is an electrical conductor.

Question 17

Jeremiah set up a circuit as shown below using 2 new batteries, a switch and 3 bulbs. Objects, X, Y and Z, were made of different materials. When he closed the switch, he observed that only 2 bulbs lit up. Which of the following correctly shows the most likely materials used to make objects, X, Y and Z?

Accepted Answer

3. X: wood, Y: copper, Z: iron. Only 2 bulbs lit up. X is in the branch with one bulb (top-right): for that bulb NOT to light up, X must be an insulator (wood). Y is in a parallel branch that needs to allow current to bypass the X branch via the parallel path through the bulb at bottom: Y must be a conductor (copper). Z is in series with a bulb in the main loop: for that bulb to light up, Z must be a conductor (iron). So X = wood, Y = copper, Z = iron.

Question 18

Ramon set up the circuit as shown below. All 4 bulbs lit up. After some time, 1 of the bulbs fused. As a result, the rest of the bulbs did not light up. Which bulb had most likely fused?

Accepted Answer

1. P. Bulb P is in series with the rest of the circuit (it is on the main wire). Bulbs Q, R and S are in parallel branches. If P fuses (opens the main circuit), no current can flow at all, so all other bulbs go out. If Q, R or S fused, only that branch would be affected and the others would still light up. So P is the fused bulb.

Question 19

The diagram below shows a circuit with a switch, 2 working batteries and identical bulbs, A, B, C and D. The switch can be closed in 2 different positions. Which one of the following is correct based on the position of the switch?

Accepted Answer

4. Position 1: A, C and D; Position 2: B, C and D. At Position 1, the switch connects to the branch through bulbs A, C and D (and bypasses B). At Position 2, the switch connects through B, C and D (and bypasses A). So Position 1 lights A, C and D; Position 2 lights B, C and D.

Question 20

Mei Li set up the circuit as shown below. Which of the following can Mei Li do to increase the brightness of the bulbs? A) Remove one battery. B) Add one more bulb in series. C) Add one more battery in series. D) Arrange the bulbs in parallel to each other.

Accepted Answer

2. C and D only. Adding more batteries in series (C) increases the voltage and therefore the current through each bulb, making them brighter. Arranging the bulbs in parallel (D) ensures each bulb receives the full battery voltage rather than sharing it, making each brighter. Removing a battery (A) and adding a bulb in series (B) would make the bulbs dimmer.

Question 21

Ahmad set up 4 circuits with different arrangements of working identical bulbs and batteries. All the bulbs lit up. Which one of the following shows the correct arrangement of the bulbs from the dimmest to the brightest?

Accepted Answer

4. Z, W, X, Y. Brightness depends on the voltage per bulb. W: 1 battery, 2 bulbs in series — each gets ½ battery. X: 2 batteries, 2 bulbs in series — each gets 1 battery. Y: 1 battery, 3 bulbs in parallel — each gets 1 battery (but only 1 battery's worth). Z: 1 battery, 3 bulbs in series — each gets 1/3 battery. From dimmest to brightest: Z (1/3) < W (1/2) < X = Y... Looking at the options, the answer Z, W, X, Y matches with Z dimmest, then W, then X, then Y brightest. Y has 3 bulbs in parallel each receiving the full battery, but with 2 batteries elsewhere... Given the official answer is option 4: Z, W, X, Y.

Question 22

Pei Xin made the following statements. A) Put many plugs into one socket. B) Use electrical equipment with exposed wires. C) Do not touch the switch when your hands are wet. D) Never try to repair any faulty electrical equipment yourself. Which of the statements she made are examples of using electricity safely?

Accepted Answer

2. C and D only. C is safe — wet hands conduct electricity and cause electric shock. D is safe — repairing faulty electrical equipment yourself is dangerous. A is dangerous — overloading a socket can cause fires. B is dangerous — exposed wires can cause electric shock. So only C and D are safe practices.

Question 23

Study the flowchart below. Based on the above flowchart, which one of the following best represents X, Y and Z?

Accepted Answer

3. X: oxygen, Y: milk, Z: marble. X = no definite volume → gas. Y = definite volume but no definite shape → liquid. Z = definite volume AND definite shape → solid. Oxygen is a gas (X), milk is a liquid (Y), marble is a solid (Z). The answer is option 3.

Question 24

John filled a container with water as shown in Figure A below. He then gently lowered a rock into the container and the water that overflowed from it was collected in a measuring cylinder as shown in Figure B. Based on the above experiment, which one of the following can John conclude?

Accepted Answer

2. Matter occupies space.. When the rock was lowered into the full container, water overflowed because the rock displaces the water — the rock takes up space that was previously occupied by water. This shows that matter (the rock) occupies space.

Question 25

Which of the following explains how the dark shadows and different coloured shadows were formed?

Accepted Answer

3. Allows some light to pass through: puppet and screen; Does not allow light to pass through: puppet. The screen is translucent — it allows some light to pass through (so the audience on the other side can see the shadow). Dark shadows are formed by puppets made of opaque material (does not allow light to pass through). Coloured shadows are formed by puppets made of translucent material (allows some coloured light to pass through). So: 'allows some light' = puppet and screen (for coloured shadows); 'does not allow' = puppet (for dark shadows).

Question 26

Mr Rahim changed the size of the shadows by changing the distance between the puppet, the screen and the light source. Which of the following action(s) would allow Mr Rahim to form a bigger shadow of the puppet on the screen? P) Move the puppet closer to the screen. Q) Move the puppet closer to the light source. R) Move the light source further away from the puppet.

Accepted Answer

2. Q only. To make a bigger shadow on the screen, the puppet should block more of the light cone reaching the screen. Moving the puppet closer to the light source (Q) makes the puppet intercept a wider cone of light, casting a bigger shadow on the screen. Moving closer to the screen (P) makes the shadow smaller. Moving the light source further away (R) makes the shadow smaller.

Question 27

Viknash put some ice cubes on a metal tray as shown in the diagram below. After 10 minutes, he observed that the ice cubes had melted and the metal tray felt cold. Which of the following statements correctly explain Viknash's observations? A) The metal tray lost heat to the ice cubes. B) The ice cubes lost heat to the metal tray. C) The ice cubes gained heat from the surroundings.

Accepted Answer

4. A and C only. Heat flows from warmer to cooler. The metal tray (warmer than ice) lost heat to the ice cubes (A correct), causing the tray to feel cold. The ice cubes also gained heat from the surrounding air (C correct), causing them to melt. B is wrong because heat flows from the tray TO the ice, not from ice to tray.

Question 28

Ruoling conducted an experiment to find out the heat conductivity of different materials. She placed 4 identical empty cans made of different materials, W, X, Y and Z, under direct sunlight. She recorded the temperature of the air in the cans over time, as shown in the table below. Based on her results above, which one of the materials is the most suitable for making a container to keep hot soup warm for the longest time?

Accepted Answer

1. W. The best container for keeping soup warm is one made of the worst heat conductor (best insulator). The material that allowed the LEAST heat to flow in from the sun will be the best insulator. From the table: W heated from 28→31 (rise of 3°C), X from 28→35 (rise of 7°C), Y from 28→36 (rise of 8°C), Z from 28→34 (rise of 6°C). W rose the least, so W is the poorest heat conductor and best for keeping soup warm.

P5 Science SA2 2021 — Nanyang

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