Question 1

Study the diagrams below. Which of the following statements is true of A and B?

Accepted Answer

C. A and B allows carbon dioxide to pass through.. A (gills of fish) allows dissolved oxygen and carbon dioxide to pass through during gas exchange, and B (stomata of leaf) allows carbon dioxide and oxygen to pass through during photosynthesis/respiration. Both structures allow carbon dioxide to pass through.

Question 2

The diagrams below show a flower and the female human reproductive system. Which of the following statement(s) is / are true? A. R receives the pollen grains. B. Fertilisation occurs in R and X. C. T and Y perform the same function. D. Male reproductive cells are stored in S and W.

Accepted Answer

A. A only. R is the stigma which receives pollen grains during pollination. B is wrong as fertilisation in flowers occurs in the ovary (S), not stigma, and in humans in the oviduct (Y), not vagina (X). C is wrong as T is the anther (produces pollen) but Y is the oviduct (transports egg). D is wrong as S is the ovary which stores female cells, and W is also an ovary.

Question 3

The table below shows the conditions in which some seeds of similar mass were planted. Both trays, A and B, were placed in a room with a temperature of 28 °C. Which of the following graphs best represents the changes in the average mass of the seed leaves over two weeks? [Figure: four line graphs showing average mass of seed leaves vs no. of days]

Accepted Answer

B. Graph 2 — A decreases, B stays constant. Tray A has water, oxygen, suitable temperature so seeds germinate. The seed leaves are used up to provide food to the growing seedling, so the average mass of seed leaves decreases. Tray B has no water so seeds do not germinate and the average mass of seed leaves stays constant.

Question 4

Study the set-ups below. A drop of liquid K was added to the water in each tube before the experiment. Liquid K changes colour as shown below. [Table: less than normal CO2 = purple; normal = red; higher than normal = yellow] After a few hours, which of the following shows the colour of water in each set-up?

Accepted Answer

D. A purple, B red, C yellow, D yellow. A (plant + light): plant photosynthesises faster than it respires, takes in CO2, level becomes less than normal → purple. B (plant + snail + light): plant uses CO2 from snail's respiration, balanced → remains red/normal. C (snail only + light): snail respires releasing CO2, level higher than normal → yellow. D (snail in dark box): snail respires releasing CO2, level higher than normal → yellow.

Question 5

Isabelle wanted to find out if the amount of light would affect the size of the tiny openings on a plant. Which of the following should she keep constant for her experiment to be a fair one? A. size of the tiny openings B. amount of light given to the plant C. amount of water given to the plant D. amount of carbon dioxide given to the plant

Accepted Answer

C. C and D only. The independent variable (changed) is amount of light. The dependent variable (measured) is size of the tiny openings — so A cannot be kept constant. B is the variable being changed. Water (C) and carbon dioxide (D) must be kept constant for a fair test.

Question 6

The graph below shows how the rate of photosynthesis of plant A changes with temperature. Based on the graph above, which of the following statements is true?

Accepted Answer

B. 35 °C is the best temperature for photosynthesis to take place.. The graph shows the highest rate of photosynthesis at 35°C compared to 30°C, 40°C and 45°C, so 35°C is the optimum (best) temperature for photosynthesis.

Question 7

An experiment was conducted on a plant which had been kept in the dark for a day and watered. Leaf A and leaf B were then covered on both sides with clear plastic and a piece of black paper respectively as shown above. The plant was then placed under bright sunlight for a day. Both leaves were then tested for starch. Which of the following is correct?

Accepted Answer

D. Leaf B — completely dark blue — Light can pass through the clear plastic so the leaf can make food.. Leaf B is covered with clear plastic which allows light to pass through, so the leaf can photosynthesise and produce starch. Iodine test on starch turns the leaf completely dark blue. Leaf A covered with black paper blocks light, so no photosynthesis, no starch, turns completely yellowish-brown.

Question 8

Ling conducted an experiment with two containers as shown below. The table below shows the results of her experiment. [Table: set-up F wax melts in 30 s; set-up G wax melts in 75 s] Ling used a mixture of water, baking soda and flour to create a flour dough. She then covered 2 identical ice-creams with different amounts of flour dough as shown below. [Figure: ice-cream R covered with thick flour dough with many air bubbles; ice-cream T covered with thinner flour dough with fewer air bubbles] The ice-creams were then deep fried using the same amount of heat for fifteen seconds. She observed that one of the ice-creams melted after being heated. Which of the following is likely to be possible?

Accepted Answer

C. Ice-cream T melted — There were less air bubbles in the flour dough so the ice-cream gained heat faster.. Air is a poor conductor of heat (insulator). Ice-cream T's dough has fewer air bubbles, so less insulation, allowing heat from the oil to be conducted to the ice-cream faster, causing it to melt. Ice-cream R has more air bubbles which insulate it better.

Question 9

Karin conducted an experiment using the set-up shown below. Materials X and Y have the same thickness. The table below shows her results. [Table: A (X+Y) = 180 units; B (Z+Y) = 100 units; C (Z+X) = 70 units] Which of the following shows the correct arrangement of the degree of transparency of the materials X, Y and Z?

Accepted Answer

B. Allow least → most: Z, X, Y. A (X+Y)=180 most light, B (Z+Y)=100, C (Z+X)=70 least. Comparing A and B (Y constant): X allows more light than Z. Comparing B and C (Z constant): Y allows more light than X. So order least to most transparent: Z, X, Y.

Question 10

Meena conducted an experiment using two identical cones in a dark room as shown below. Shadows were formed on screens K and L. Which of the following shadows would be observed for each screen?

Accepted Answer

D. Screen A — circle; Screen B — triangle pointing left. Cone K stands point-up under the lamp, so viewed from above, the light sees the circular base of the cone — shadow on screen K is a circle. Cone L lies on its side, so the lamp from above sees the triangular profile of the cone — shadow on screen L is a triangle pointing in the same horizontal direction as the cone's point.

Question 11

The diagram below shows three containers of different shapes. 500 ml of water was poured into each container. The containers were then left in a room. The amount of water remaining in the containers were measured after three days. Which of the following shows correctly the comparison of the amount of water left in the containers after three days?

Accepted Answer

A. Most → Least: B, C, A. The larger the exposed surface area of water, the faster the rate of evaporation, so less water remains. A has the largest exposed surface area → least water left. C has the smallest exposed surface area → most water remains, then B, then A.

Question 12

The table below shows the conditions for four set-ups Q, R, S and T. Same amount of water was used for all the set-ups. Based on the set-ups above, which of the following are possible aims? A. To find out if the presence of light affects rate of evaporation. B. To find out if the presence of wind affects the rate of evaporation. C. To find out if the surrounding temperature affects the rate of evaporation. D. To find out if the amount of exposed surface area of water affects the rate of evaporation

Accepted Answer

D. C and D only. Compare R and S: only temperature differs (26°C vs 35°C), so aim C is possible. Compare Q and R: only exposed surface area differs (25 vs 50 cm²), so aim D is possible. There is no set-up with constant temperature and surface area but differing wind only that isolates wind alone properly without varying strength type comparisons matching; light is not varied at all. So C and D are valid aims.

Question 13

The diagram below shows a toy aeroplane that works on batteries. When Leon played with the toy, he made the following observations. [Table: X only — Propeller did not move, Canopy was lit; Y only — Propeller moved, Canopy did not light up; Both X and Y — Propeller moved, Canopy was lit] Which of the following shows the correct circuit inside the toy aeroplane? [Figure: four circuit diagrams labelled (1)–(4)]

Accepted Answer

B. Circuit 2. Switch X controls only the canopy (bulb) and switch Y controls only the motor (propeller), so the bulb and motor must be on two separate parallel branches, each with its own switch in series. Circuit 2 shows this parallel arrangement with X in the bulb branch and Y in the motor branch.

Question 14

Which of the following is a not safe way to use electricity?

Accepted Answer

D. Inserting a metal rod to the electrical outlet to insert a 2-pin plug easily.. Metal is a good conductor of electricity. Inserting a metal rod into an electrical outlet allows current to flow through the user, causing electric shock — unsafe. The other options are safe practices.

Question 15

Four balls of the same material W, X, Y and Z, were dropped from different heights as shown below. Which of the following statements about the four balls in the diagram above are true? A. Ball X has more potential energy than Ball Z. B. Ball X has the same amount of potential energy as Ball W. C. Ball Y makes a louder sound when it hits the ground than Ball Z. D. Gravitational potential energy is converted to kinetic energy when the balls are dropped.

Accepted Answer

C. A, C and D only. GPE depends on mass and height. X (120 g, 60 m) > Z (80 g, 30 m) → A true. X (120 g, 60 m) > W (80 g, 60 m) → B false. Y (heavier, higher than Z) has more kinetic energy on impact, louder sound → C true. As balls fall, GPE converts to KE → D true. So A, C and D.

Question 16

A toy car was wound a few times and released as shown in the diagram below. The toy car was only able to travel a short distance up the ramp to point W. Which of the following shows the changes that could be made to the set-up above to allow the car to travel as high up the ramp as possible?

Accepted Answer

C. Number of turns — increase; Distance R — decrease; Height of ramp — decrease. Increase number of turns → more elastic potential energy → more kinetic energy. Decrease distance R → less friction loss before reaching ramp → more KE retained. Decrease ramp height (gentler slope) → car can travel a greater distance up the ramp. So increase turns, decrease R, decrease height.

Question 17

The diagram below shows some solar panels installed on the roof of a house. Which of the following shows the main energy conversion that allows a lamp in the house to work?

Accepted Answer

D. Light energy → Electrical energy → Light energy + Heat energy. Solar panels convert light energy (from the sun) into electrical energy. The lamp then converts electrical energy mainly into light energy, with some heat energy as a by-product.

Question 18

The diagram below shows the conversion of electrical energy to other forms of energy by some electrical appliances. Which of the following best represents the forms of energy in P, Q, R and S respectively?

Accepted Answer

A. P light, Q sound, R kinetic, S heat. Table lamp converts electrical → light (P = light). Washing machine converts electrical → kinetic (drum spins) and sound (Q = sound or kinetic, R = the other). Rice cooker converts electrical → heat (S = heat). Option A matches: P light, Q sound, R kinetic, S heat.

P6 Science CA1 2025 — CHIJ

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