Question 1

Which animal is not a reptile?

Accepted Answer

C. fish. Reptiles have dry scaly skin and lay eggs on land. Tortoises, crocodiles and geckos are reptiles. A fish lives in water, has wet scales and gills, so it belongs to the fish group, not reptiles.

Question 2

The diagram below shows a pair of scissors. Metal is used to make the blades of the scissors because metal ____.

Accepted Answer

C. does not break easily. Scissor blades must withstand the force of cutting without breaking. Metal is strong and does not break easily, making it suitable for blades.

Question 3

Which organ system is shown in the diagram?

Accepted Answer

D. circulatory system. The diagram shows the heart and a network of blood vessels distributed throughout the body. This is the circulatory system, which transports blood, oxygen and nutrients.

Question 4

Which part, (1), (2), (3) or (4), makes food for the plant?

Accepted Answer

B. leaf. Leaves contain chlorophyll, which captures sunlight to make food through photosynthesis. The flower is for reproduction, the stem supports the plant and transports substances, and the roots absorb water and minerals.

Question 5

Nina made the following observations on the life cycle of an animal. • There are three stages in the life cycle. • The young looks like the adult. Which animal was Nina observing?

Accepted Answer

D. cockroach. A cockroach undergoes incomplete metamorphosis with three stages: egg, nymph, adult. The nymph looks like a smaller version of the adult. Frogs, beetles and butterflies all have four stages.

Question 6

The diagram shows the life cycle of a plant. What is the stage marked X?

Accepted Answer

B. seed. A plant's life cycle starts with a seed, which germinates into a young plant (seedling), then grows into a mature plant that produces new seeds. Stage X is shown as a small oval at the start of the cycle, representing a seed.

Question 7

Study the diagram below. Which of the following statements is true?

Accepted Answer

B. Both objects are the same mass.. A balanced see-saw/beam balance means both sides exert equal downward pull, so the two objects must have the same mass. Their size, shape and volume can clearly differ.

Question 8

Which of the following is a light source?

Accepted Answer

D. candle flame. A light source gives out its own light. A candle flame produces its own light. A mirror, leaf and orange only reflect light from other sources; they are not light sources themselves.

Question 9

Ali used the thermometer below to measure the temperature of the water in the basin. What is the temperature of the water in the basin?

Accepted Answer

C. 24°C. The zoomed-in view of the thermometer shows the red/black liquid level between the 20 and 30 marks, at the second small division above 20, indicating 24°C.

Question 10

Which of the following can be attracted by a magnet?

Accepted Answer

A. steel ball. Magnets attract objects made of magnetic materials such as iron, steel, nickel and cobalt. Steel contains iron and is attracted by a magnet. Rubber, wood and aluminium are non-magnetic.

Question 11

Wen Jie observed two organisms, X and Y, as shown below. He made the following statements about both organisms. A: Both reproduce by spores. B: Both are non-flowering plants. C: Both can make food on their own. Which of the above statement(s) is/are correct?

Accepted Answer

A. A only. Organism X is a mushroom (a fungus) and organism Y is a fern (a non-flowering plant). Both reproduce by spores, so A is correct. B is wrong because the mushroom is a fungus, not a plant. C is wrong because the mushroom (fungus) cannot make its own food.

Question 12

Study the chart below. Which of the following best represents characteristics A and B?

Accepted Answer

C. has three body parts | has gills. Insects are characterised by having three body parts (head, thorax, abdomen) — not all insects have wings. Fish are characterised by having gills. So A is 'has three body parts' and B is 'has gills'.

Question 13

Which of the following is not a function of the skeletal system?

Accepted Answer

D. It carries digested food, water and oxygen in the blood to all parts of the body.. The skeletal system supports the body, gives it shape and protects internal organs. Transporting digested food, water and oxygen in the blood is the function of the circulatory system, not the skeletal system.

Question 14

The diagram below shows part of the human digestive system. The arrows represent the direction of the substances. What do the letters M, N and P represent?

Accepted Answer

A. digested food | undigested food | undigested food. M is the substance moving from the small intestine into the blood — that is digested food (absorbed nutrients). N is the substance moving from the small intestine into the large intestine — undigested food. P is the substance moving from the large intestine out of the body — undigested food (faeces).

Question 15

Study the flowchart below. What can organ A and question B be?

Accepted Answer

C. gullet | Is digestion completed here?. Food is not broken down in the gullet (oesophagus), so 'No' branches to gullet. Among the stomach and small intestine, digestion is completed in the small intestine but not in the stomach. So question B is 'Is digestion completed here?': No → stomach, Yes → small intestine.

Question 16

The diagram below shows the different stages of the life cycle of a plant. At which stage(s) will the plant be able to make its own food?

Accepted Answer

B. A and C only. A plant makes its own food (photosynthesis) only when it has green leaves containing chlorophyll. Stage A (mature plant with leaves) and stage C (seedling with leaves) both have leaves, so both can make food. Stages B and D are seeds, which cannot make food.

Question 17

Shulin planted five seeds each in three identical pots, X, Y and Z. The pots are left at different locations with different temperatures. She gave each plant the same amount of water every day. After one week, she measured and recorded the average height of the seedlings in each pot in the table below. Based on the table above, which of the following statements is correct?

Accepted Answer

B. Seeds are unable to germinate at 45°C.. The table shows that 0 seeds germinated in pot Z at 45°C, indicating seeds cannot germinate at this temperature. The water amount was the same so (A) is not supported. (C) is incorrect because 30°C had more germinations than 15°C. (D) is clearly wrong since results differ across temperatures.

Question 18

A dented ping pong ball will become round again when put into a basin of hot water. What causes the ping pong ball to become round again?

Accepted Answer

C. The air inside the ping pong ball gains heat and expands.. Hot water transfers heat to the air inside the ball. The air gains heat and expands, pushing the dent outward, returning the ball to its round shape.

Question 19

Ravi joined two 500 cm³ flasks, A and B, to an air pump shown below. He pushed down the plunger to pump in 300 cm³ of air into both flasks. What was the final volume of air in each flask after the pump?

Accepted Answer

D. 500 | 300. Air takes up all available space (it has no fixed volume). Flask A is empty so the air occupies the entire 500 cm³. Flask B already contains 200 cm³ of water, leaving 500 − 200 = 300 cm³ of space for air. The volumes are therefore 500 cm³ and 300 cm³ regardless of how much air is pumped in.

Question 20

Huifen set up the experiment below. When the cardboards were placed in a straight line, Huifen could see the plant. However, when she shifted one of the boards slightly to the left, she could not see the plant anymore. Which property of light explains Huifen's observation?

Accepted Answer

A. Light travels in a straight line.. Light from the plant reaches Huifen's eye only if it travels in a straight path through all three holes. When one cardboard is shifted, the holes are no longer aligned and light cannot reach her eye, so she cannot see the plant.

Question 21

Mrs Tay added some ice cubes into a glass of juice as shown below. Which of the following correctly describes her observation after 15 minutes?

Accepted Answer

B. solid to liquid | decrease. The ice cubes (solid) gain heat from the juice and melt into liquid water. The juice loses heat to the ice cubes, so its temperature decreases.

Question 22

Rudy wanted to investigate how different materials affect the amount of light passing through them using the set-up shown below. Which of the following variables should be kept constant for a fair test? A: The material of the object B: The thickness of the object C: The brightness of the torch D: The distance between the torch and the light sensor

Accepted Answer

D. B, C and D. The material is the variable being changed (independent variable). To ensure a fair test, all other variables must be kept constant: thickness of object (B), brightness of torch (C) and distance between torch and sensor (D).

Question 23

Janelle placed 3 shapes A, B and C, at different distance in front of a torch as shown below. The shapes were all 5 cm tall and hollow in the center. The diagram below shows the shadow that was formed on the screen. Which of the following correctly represents shapes A, B and C?

Accepted Answer

D. square | triangle | circle. An object closer to the light source casts a larger shadow; the farther it is from the torch, the smaller its shadow. The largest outline on the screen is a square (so A, closest to the torch, is a square), the next is a triangle (B), and the smallest is a circle (C, farthest from the torch).

Question 24

The man in the diagram below walks from position M to N, then to O and finally to P. Which of the following shows how the length of the shadow will most likely change as he walks from M to P?

Accepted Answer

A. length: tall at M, short at N, short at O, tall at P. The lamp is directly above the region between N and O. When the man is far from the lamp (at M or P), the light hits him at a low angle, casting a long shadow. When directly below or close to the lamp (at N and O), the shadow is much shorter. So shadow lengths are: long at M, short at N, short at O, long at P.

Question 25

Cedric placed 4 similar uncooked eggs into beakers A, B, C and D, which contained water at different temperatures and different volumes. The eggs were left in the beakers for 10 minutes. After 10 minutes, Cedric cracked each of the eggs to find out how cooked it was. Arrange the eggs in order, from the most cooked to the least cooked.

Accepted Answer

B. A | D | B | C. Higher water temperature cooks the egg more; greater water volume also provides more heat. A (600 ml at 80°C) is the most cooked. D (400 ml at 80°C) is next (same temperature but less water than A). B (400 ml at 50°C) is third. C (200 ml at 30°C) is the least cooked. Order: A → D → B → C.

Question 26

A metal spoon is placed in a bowl of ice cream as shown below. After a while, the spoon becomes cold. Which of the following statements explains why the spoon becomes cold after a while?

Accepted Answer

C. The spoon loses heat to the ice cream.. Heat always flows from a hotter object to a colder one. The spoon is warmer than the cold ice cream, so heat flows from the spoon to the ice cream. The spoon loses heat and becomes cold.

Question 27

Emma set up the experiment below. She used the magnets to make the toy car fall off the table. What are the likely poles of X, Y and Z?

Accepted Answer

D. South | North | South. For magnet Z to push the toy car off the edge, the three magnets must all repel one another so Z is pushed outward. Like poles repel. With X-Y-Z labelled left poles S-N-S, X's right pole (N) meets Y's left (N) → repel; Y's right pole (S) meets Z's left (S) → repel. The chain of repulsions pushes Z toward the car and off the table.

Question 28

Mr Wong had two electromagnets, P and Q, as shown below. He placed an iron nail in between the two electromagnets. What should Mr Wong do if he wants the iron nail to move towards electromagnet Q? A: Add more batteries to P. B: Add more batteries to Q. C: Increase the number of coils around P. D: Increase the number of coils around Q.

Accepted Answer

D. B and D only. To pull the iron nail toward Q, electromagnet Q must be stronger than P. The strength of an electromagnet increases when more batteries are added (B) or when the number of coils is increased (D). Adding batteries or coils to P would make P stronger and pull the nail the wrong way.

P4 Science SA2 2023 — Red Swastika

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