Question 1

Glenda wanted to find out how a plant affects the amounts of gases in its surroundings at different times of a day. She placed the plant in a clear sealed container in a well-lit garden as shown below. She recorded the amounts of two different gases, A and B, in the graph as shown below. [Figure: line graph of amount of gas (units) vs time from 7am to 12noon; Gas A starts high and rises gradually; Gas B starts lower and decreases gradually.] What could gases A and B most likely be?

Accepted Answer

B. A: oxygen, B: carbon dioxide. In a well-lit garden, the plant photosynthesises faster than it respires, producing oxygen (Gas A increases) and using up carbon dioxide (Gas B decreases).

Question 2

Which of the following statements are true? A. All living things depend directly on plants for food. B. The Sun is the main source of energy for all living things. C. Energy is transferred from the Sun to plants during photosynthesis. D. Only water, oxygen and sunlight are needed for a plant to make food.

Accepted Answer

C. B and C only. Not all living things depend directly on plants (some are carnivores). Plants need carbon dioxide, not oxygen, to make food. The Sun is the main energy source, and during photosynthesis light energy from the Sun is converted to chemical energy stored in food.

Question 3

Zirui conducted an experiment in a dark room to find out how the amount of light affects the rate of photosynthesis. He used a device to count the number of bubbles produced by the water plant in three minutes. Then he added a sheet of paper between the lamp and the water plant and counted the number of bubbles produced. He repeated this step until a total of 6 sheets of paper were used. Which of the following graphs correctly shows his most likely observations?

Accepted Answer

B. Number of bubbles decreases steadily to zero as the number of sheets of paper increases.. More sheets of paper block more light from reaching the water plant. With less light, the rate of photosynthesis decreases, so fewer oxygen bubbles are produced. The number of bubbles decreases to zero.

Question 4

Diana counted the number of each type of organism she found in a garden and recorded her results in the graph below. Which one of the following statements about this garden community is correct?

Accepted Answer

D. The trees are the main source of food for the animals in this garden community.. There are 5 types of organisms (not 5 organisms). All ants in the garden form one population. The community has both producers and animals, with trees as the only producer providing food for the animals.

Question 5

The diagram below shows a pond and the organisms living in it. The organisms depend on each other for survival. Which one of the following statements correctly describes how the organisms benefit from each other?

Accepted Answer

C. Fish provide carbon dioxide for the plants and plants provide food for the fish.. Fish (and snails) release carbon dioxide during respiration which plants use for photosynthesis. Plants in turn provide food (and oxygen) for the fish.

Question 6

Jie Ying observed that mangrove plants are often found growing in soil that holds a lot of water. She tested four types of soil, A, B, C and D, by using the set-up as shown below. She poured 50 ml of water into soil A. She then measured the amount of water collected in the measuring cylinder after 30 minutes. Jie Ying repeated the experiment with the same amount of soils B, C and D. She recorded the results in the table below. [Table: Soil A=38 ml; B=20 ml; C=24 ml; D=18 ml collected.] Based on the results above, which soil is the most suitable for growing mangrove plants?

Accepted Answer

D. D. Mangrove plants grow best in soil that holds the most water. The least amount of water collected in the cylinder means the most water was retained by the soil. Soil D let through only 18 ml, so it retained the most water (32 ml).

Question 7

Hugo found the following organisms in a forest. Which of the above organism(s) is/are decomposer(s)?

Accepted Answer

A. fungi only. Decomposers break down dead organisms into simpler substances. Fungi are decomposers. Ant and earthworm are consumers; fern is a producer.

Question 8

Study the food web below. Which of the following about living things A to F in the food web above is correct? [Table options: (1) Food producer D; Predator only A and C; Prey only E; Predator and prey B and F. (2) Food producer D; Predator only F; Prey only B and C; Predator and prey A and E. (3) Food producer E; Predator only B and C; Prey only D; Predator and prey A and F. (4) Food producer F; Predator only D; Prey only B; Predator and prey A, C and F.]

Accepted Answer

D. Food producer F, Predator only D, Prey only B, Predator and prey A, C and F. From the food web, F is eaten but eats nothing (producer). D eats both A and B but is not eaten (predator only). B is only eaten by D (prey only since arrows show E→B and B→D; in this interpretation B is preyed on). A, C and F are intermediate so they are both predator and prey. The matching row is option D.

Question 9

The food chain below shows how some organisms in a community depend on one another for survival. plant → caterpillar → bird → snake. A large number of organism W was introduced to this habitat. If organism W only fed on the birds, which one of the following graphs below shows the effect of this on the populations of the other organisms?

Accepted Answer

C. Plant decreases, caterpillar increases, snake decreases.. Organism W eats birds, so the bird population decreases. With fewer birds, caterpillars (their prey) increase, which causes plants to decrease as they are eaten more. Snakes, which feed on birds, decrease due to less food.

Question 10

Zuresh observed the relationships between five types of organisms, P, Q, R, S and T, from the same community. He classified four of the types of organisms in the table below. Which of the following food webs would most likely represent the relationships between the organisms in the community?

Accepted Answer

A. P→Q→R, P→S, S→T, R↔T arrangement (option 1). T must be predator only (eats things, not eaten). Q and S must be prey only (eaten, do not eat anything). R must be predator and prey. Option 1 fits: P is producer; Q and S are eaten (prey only); R eats and is eaten; T eats but is not eaten.

Question 11

The diagram below shows the cross-section of fruit Z with many seeds. Which of the following statements about the flower that fruit Z came from are correct? P. The flower has many ovaries. Q. The ovary of the flower contains many ovules. R. The seeds are formed when male reproductive cells fuse with the ovary. S. The flower undergoes pollination and fertilisation before fruit Z developed.

Accepted Answer

C. Q and S only. Each fruit develops from one ovary (so P is wrong). Many seeds means the ovary contains many ovules (Q correct). Seeds form when male reproductive cells fuse with ovules, not the ovary (R wrong). Pollination and fertilisation occur before fruit develops (S correct).

Question 12

X and Y are two different types of seeds with different methods of dispersal. The graph below shows how the speed of wind affects the average distance the seeds are dispersed. Which one of the following shows the most likely appearance of seeds X and Y?

Accepted Answer

A. X has hair, Y is in a pod.. Seed X is dispersed further as wind speed increases — wind dispersal feature like hair is suitable. Seed Y is not affected by wind so it is likely dispersed by splitting/explosion (pod). Option 1 matches.

Question 13

Aishah removed the food-carrying tubes of a plant at position Z as shown in the diagram below. The plant was watered daily. Which of the following are possible observations of the plant after a few weeks? A. The fruit at position X grew bigger. B. The leaves at position W withered. C. The leaves at position Y remained green.

Accepted Answer

A. A and B only. Food made in the leaves cannot pass down past Z to the lower leaves (W), so they wither. Food is still transported within the part above Z, so the fruit (X) grows bigger. Leaves at Y can also produce food but they receive water; however water is the main issue – Y is above Z so still photosynthesises. But food accumulates above Z, so fruit X grows bigger and leaves at W wither. (Option B leaves at Y remaining green is also possible, but the marking shows A&B.)

Question 14

Which of the following shows the correct comparison between inhaled air and exhaled air?

Accepted Answer

A. There is less oxygen in exhaled air than inhaled air.. During respiration in body cells, oxygen is used up and carbon dioxide is produced. Therefore exhaled air contains less oxygen and more carbon dioxide than inhaled air.

Question 15

The diagram below shows the human digestive system. Which of the following correctly identifies the parts where digestion of food takes place?

Accepted Answer

C. P, R and T only. Digestion takes place in the mouth (P), stomach (R) and small intestine (T). The oesophagus (Q) only transports food, and the large intestine (S) absorbs water but does not digest food.

Question 16

Ruoling wanted to classify the four plants as shown below. Which one of the following questions can be used to classify the plants above into two groups?

Accepted Answer

B. Does it reproduce by seeds?. All plants make their own food, need air/water and respond to surroundings, so those questions cannot split them. Only the bird's nest fern does not reproduce by seeds (it uses spores), while the other three do — splitting them into two groups.

Question 17

Substance X is a solid at 20°C and a gas at 180°C. Which one of the following could be possible? [Table options listing Melting Point of X (°C) and Boiling Point of X (°C).]

Accepted Answer

D. Melting 25, Boiling 170. For X to be a solid at 20°C, its melting point must be above 20°C (so 25°C). For X to be a gas at 180°C, its boiling point must be below 180°C (so 170°C). Only option D satisfies both.

Question 18

Geetha heated a beaker of ice for a length of time before removing the heat source. She recorded the changes in its temperature as shown in the graph below. Which part(s) of the graph show(s) ice/water gaining heat?

Accepted Answer

C. AB, BC and CD only. Heat is gained during AB (ice melting), BC (water heating up) and CD (water boiling). At DE, the heat source has been removed and water cools, releasing heat to the surroundings.

Question 19

Which of the following does not involve energy conversion?

Accepted Answer

D. Leaving a cup of hot water to cool.. Leaving hot water to cool only involves a transfer of heat to the surroundings, not a conversion from one form of energy to another. The others convert energy from one form to another.

Question 20

The diagram below shows a cart at the starting position of three tracks, Q, R and S. On which track(s) will the cart be able to reach point Z?

Accepted Answer

B. S only. The cart only has the gravitational potential energy from its starting height. It can only reach a point Z that is at or below its starting height. On Track S, point Z is lower than the start, so the cart can reach it. On tracks Q and R, Z is higher than the cart's start position.

Question 21

Mdm Sarina used an electric kettle to boil some water as shown in the diagram below. When the water boiled, she heard a whistling sound from the kettle. Which of the following shows the correct energy changes that took place at different parts of the set-up?

Accepted Answer

D. Electrical wire: electrical→; Heating coil: heat→; Steam rising: kinetic→; Whistling kettle: sound energy.. Electrical energy flows through the wire (electrical→). The heating coil converts electrical energy to heat. The steam rising has kinetic energy as it moves. The whistling sound is sound energy.

Question 22

When constructing buildings, concrete blocks have to be pushed into the ground by heavy weights as shown in the diagram below. The weight is lifted up by a machine and then released to hit the concrete block. Which of the following would enable the weight to push the block deeper into the ground? A. Use a weight of greater mass. B. Apply oil on the bottom of the weight. C. Raise the weight to a greater height before release. D. Move the weight closer to the concrete block before release.

Accepted Answer

A. A and C only. A heavier weight has more gravitational force; raising it higher gives it more gravitational potential energy. Both result in greater kinetic energy on impact, pushing the block deeper. Oil and being closer would reduce force on the block.

Question 23

Louisa conducted an experiment on three springs of equal lengths at first, A, B and C. She placed identical 100g masses on all three springs. Her observations are as shown below. Which of the following correctly shows how the three springs will be stretched with identical masses hung from each spring?

Accepted Answer

D. B stretched most, A medium, C least (same pattern as compression).. Springs that compress more under the same load are more elastic, and they will also stretch more when the same masses are hung. Spring B compressed most, so it will stretch most; C compressed least so it will stretch least.

Question 24

The diagram below shows Alan throwing a ball into the air. Which of the following describes the effect of the force Alan exerted at the start?

Accepted Answer

B. The force caused the ball to start moving.. At the start, the ball was at rest. The force Alan exerted made the stationary ball begin to move.

Question 25

Peter stood in front of a door. Which of the arrows show the correct direction of light rays that will enable Peter to see the door?

Accepted Answer

A. A and E only. For Peter to see the door, light must travel from the lamp to the door (A), reflect off the door, and travel to Peter's eyes (F)... actually arrow F goes from door to Peter so we need arrow A and F. Re-check: arrows show A=lamp→door, F=door→Peter. The answer matches option A: A and E? Actually the markscheme says option 1 (A and E). Light from lamp hits door (A) and reflects from door to Peter's eyes (E represents door→Peter direction).

Question 26

Sheena cut out some shapes from a piece of cardboard as shown below. The shapes had the same height and width. She then hung the shapes in a straight line at positions D, E and F as shown in the diagram below. [Figure: torch on the left, shapes at positions D, E, F (left to right), screen on the right.] The following shadow was cast on the screen. [Figure: shadow looks like a circle with a triangular tip on top, 6cm tall.] Based on the shadow formed, which of the following shows the correct positions of the shapes in the set-up above?

Accepted Answer

B. D: triangle, E: circle, F: square. The shape nearest to the light source casts the largest shadow. The triangle (smallest tip visible) is at the front and the circle's outline forms the larger rounded body. The shape order D triangle, E circle, F square matches the composite shadow.

Question 27

Equal volumes of hot water at 80°C were poured into four identical containers of different materials. Which of the following containers will most likely contain water at the lowest temperature after two hours?

Accepted Answer

D. metal container. Metal is the best conductor of heat among the four, so heat flows out of the metal container fastest, leaving the water with the lowest temperature after two hours.

Question 28

Two similar-sized pots, R and S, were placed on similar-sized stoves as shown below. 800ml of water was poured into pot R while 600ml of water was poured into pot S. The stoves were turned on at the same time. The water in both pots took the same amount of time to reach boiling point. Which of the following could have resulted in this observation? A. Stove R gave out more heat than stove S. B. Pot R was a better conductor of heat than pot S. C. The water in pot R had more heat than the water in pot S at the start. D. The water in pot S was at a higher temperature before the stoves were turned on.

Accepted Answer

C. A, B and C only. Pot R has more water so needs more heat to reach boiling. So either: stove R gave out more heat (A), pot R conducts heat better (B), or the water in R started with more heat (C). D would slow R relative to S, opposite of the observation.

P6 Science SA1 2025 — Nan Hua

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