Question 1

Which of the following is not a reptile?

Accepted Answer

B. Frog. Reptiles include turtles, snakes and crocodiles. A frog is an amphibian (its young live in water as tadpoles with gills, adults live on land with lungs), so it is not a reptile.

Question 2

The arrows (→) in the diagram show how a substance moves in plants, starting from the roots of the plant.

roots → stem → leaves

What is this substance?

Accepted Answer

D. water. Water (with dissolved mineral salts) is absorbed by the roots and travels up the stem to the leaves. Food is made in the leaves and travels in the opposite direction; air enters mainly through leaves; soil is not transported through the plant.

Question 3

Which animal has a 4-stage life cycle?

Accepted Answer

A. beetle. A beetle undergoes complete metamorphosis with four stages: egg → larva → pupa → adult. Cockroach and grasshopper have a 3-stage life cycle (egg → nymph → adult); chicken has a 3-stage life cycle (egg → young → adult).

Question 4

Which one of the following shows the correct order when food moves through some parts of the digestive system?

Accepted Answer

A. stomach → small intestine → large intestine. Food moves from the mouth to the gullet, then to the stomach, then the small intestine, and finally the large intestine before waste is removed. So among the parts shown, stomach → small intestine → large intestine is the correct order.

Question 5

The diagram below shows a knife.

Metal is used to make the blade of the knife because metal ____.

Accepted Answer

C. does not break easily. A knife blade must be strong and hard so that it does not break or bend when cutting. Metal is chosen because it is strong and does not break easily. Reflecting light, floating, or being opaque are not the reason for using metal in a blade.

Question 6

Study the diagram below.

Which one of the following statements is true?

Accepted Answer

B. Both objects have the same mass.. The two objects are placed on a balance that is level (horizontal), which means the masses on both sides are equal. The objects clearly differ in size, shape and volume, so only mass is the same.

Question 7

The diagram shows a magnet brought near a plastic ball.

What will happen to the plastic ball?

Accepted Answer

B. It will stay still.. Magnets only attract magnetic materials (such as iron, steel, nickel and cobalt). Plastic is non-magnetic, so the magnet exerts no force on the plastic ball, and the ball stays still.

Question 8

Which one of the following is a source of light?

Accepted Answer

C. A lighted matchstick. A source of light gives out its own light. A lighted matchstick produces its own light. The moon, a mirror and a shiny coin do not produce light — they only reflect light from other sources.

Question 9

Malcome wants to measure the temperature of hot water in a beaker. Which one of the following diagrams shows the correct position of the thermometer when taking temperature reading?

Accepted Answer

C. Thermometer upright, bulb fully immersed in the water and not touching the bottom or sides. For an accurate reading, the bulb of the thermometer must be fully immersed in the water (so it reads the water's temperature) but must not touch the sides or bottom of the beaker (so it does not read the beaker's temperature). Option 3 shows this correct placement.

Question 10

Which one of the following properties is true for both air and a balloon?

Accepted Answer

B. They take up space.. All matter takes up space, including air (a gas) and a balloon (a solid rubber object). Air cannot be seen; the balloon and air do not share a fixed shape (air takes the shape of its container); air does not have a fixed volume.

Question 11

Which one of the following is a characteristic of all fungi?

Accepted Answer

C. All fungi cannot make their own food.. Fungi do not have chlorophyll, so none of them can make their own food — they must get nutrients from other living or dead things. Some fungi are poisonous, fungi reproduce by spores (not seeds), and many fungi (such as mushrooms) can be seen with the naked eye.

Question 12

Study the flowchart below.

Based on the information given, which one of the following is true?

Accepted Answer

D. Animal X lives in water throughout its life cycle but Animal Y does not.. From the flowchart: W = does not lay eggs. X = lays eggs AND lives in water throughout its life cycle. Y = lays eggs, does not live in water throughout its life cycle, AND has a 3-stage life cycle. Z = lays eggs, does not live in water throughout its life cycle, AND does not have a 3-stage life cycle. So X lives in water throughout its life cycle while Y does not — option 4 is correct. Option 1 is wrong (both X and Z lay eggs); option 2 is wrong (W does not necessarily live in water; Z does not); option 3 is wrong (Y has the 3-stage life cycle, not Z).

Question 13

The diagram below shows a water plant in a tank of water.

Which of the following plant part and the function is not correct for this plant?

Accepted Answer

B. Stem — Takes in water and minerals. The stem holds the plant upright and transports water/minerals and food through the plant — it does not take in water and minerals. Water and minerals are taken in by the roots. So option 2 is the incorrect plant-part-and-function pairing.

Question 14

The organs in the digestive system are represented by the letters P, Q, R, S and T. The graph below shows the amount of undigested food leaving each organ after a meal.

Based on the above graphs, which of the following is correct?

Accepted Answer

B. Mouth=T, Gullet=Q, Small intestine=S, Large intestine=P. As food passes through the digestive system, more of it is digested and absorbed, so the amount of UNDIGESTED food decreases along: mouth → gullet → small intestine → large intestine. Mouth has the most undigested food (highest bar) and large intestine the least. From the bar heights T (tallest) > Q > S > P (shortest), so Mouth = T, Gullet = Q, Small intestine = S, Large intestine = P. Option 2 matches.

Question 15

The table below shows the properties of four materials, P, Q, R and S. A tick (✓) indicates that the object has that property.

Based on the table above, which material, P, Q, R or S, is most suitable to make a food tray that can be used in the food centre?

Accepted Answer

A. P. A food tray used in a food centre must be waterproof (to hold spilled drinks/food), strong (to support the weight of food and not break easily) and ideally flexible enough to handle without snapping. Material P is the only one with all three properties (waterproof, flexible, strong). Q lacks 'strong'; R lacks 'flexible'; S lacks 'waterproof'.

Question 16

Ming Hui used the set-up below to test the strength of four bags, A, B, C and D. The bags were of the same size but made of different materials. He put garden soil into the bags and increased the amount of soil in each bag until the bag broke. He recorded his results in the table below.

Based on the results above, which bag is most suitable to be used to carry 2000g of rice?

Accepted Answer

B. B. The bag must be strong enough to hold 2000 g without breaking, so the amount of soil that caused the bag to break must be GREATER than 2000 g. Bag A broke at 580 g (too weak), Bag B broke at 2500 g (strong enough), Bag C broke at exactly 2000 g (would break with the rice), Bag D broke at 1220 g (too weak). Only Bag B can safely carry 2000 g of rice.

Question 17

Harry conducted an experiment using three different objects, W, X and Y. The container of water is filled up to the spout. As each object is placed into the container, some water flowed out from the spout and is collected in a beaker. The amount of water in the beaker was then measured and recorded.

Which of the following can Harry conclude about the above objects W, X and Y?

A  Object Y has the greatest volume.
B  Object X has a greater mass than W.
C  Objects X and Y have the same volume.
D  Object X has a greater volume than W.

Accepted Answer

C. C and D only. The volume of water displaced equals the volume of the submerged object. W displaced 20 ml, X displaced 25 ml, Y displaced 25 ml. So X and Y have the same volume (C is correct) and X has a greater volume than W (D is correct). A is wrong because Y does not have the GREATEST volume (it ties with X). B is wrong because the experiment measures volume, not mass — we cannot conclude anything about mass.

Question 18

Which of the following are not matter?

A  Cloud
B  Ice cubes
C  Shadow of a tree
D  Sound of the school bell

Accepted Answer

D. C and D only. Matter has mass and takes up space. Cloud (made of tiny water droplets) and ice cubes (solid water) are matter. A shadow is the absence of light, and sound is a form of energy — neither has mass nor occupies space, so they are not matter.

Question 19

Substance S changes directly from solid to gas at room temperature. Chun Li placed a piece of 50 cm³ substance S into a box. The volume of the box is 500 cm³. She then sealed the box tightly and left it in a room until all the substance S disappeared.

What is the final volume of air in the box after all of substance S has disappeared?

Accepted Answer

B. 450 cm³. At the start, the box (500 cm³) contained 50 cm³ of solid S and 450 cm³ of air. When S sublimes into a gas, it (together with the air) fills the whole box (since gases take the shape and volume of their container) — but the question asks specifically for the volume of AIR, which does not change. The air still occupies 450 cm³ of space (the amount not taken up by the gas of substance S, which now fills 50 cm³ worth — gases mix, but considering the original air alone, it remains 450 cm³).

Question 20

Study the set-up shown below.

Which one of the following actions would increase the number of steel paper clips attracted to the electromagnet?

Accepted Answer

B. Connect another battery to the circuit.. The strength of an electromagnet (and so the number of paper clips attracted) increases when more batteries are added, when more turns of wire are coiled around the iron rod, or when the magnet is brought closer to the clips. Adding another battery increases the current and the magnetic strength. The other options either do not change the strength (more clips in the tray) or decrease it (fewer turns of wire, moving further away).

Question 21

Rick placed one end of a magnet close to a compass.

Which of the following observation(s) is/are possible?

Accepted Answer

C. B and C only. The needle of a compass is a small magnet whose painted/dark end is the NORTH pole. Opposite poles attract, like poles repel. In set-up A the bar magnet's S pole faces the compass needle's N pole (attraction) — needle's N would point TOWARDS the magnet, not away (so A's observation is wrong). In set-up B the bar magnet's N pole faces the compass needle's N pole (repulsion) — needle's N points AWAY (correct observation shown). In set-up C the bar magnet's S pole faces the compass — the compass N is attracted towards S (needle points towards the magnet, correct). In set-up D the bar magnet's N pole faces the compass — needle's N is repelled away, but the diagram shows the needle pointing towards the magnet (wrong). So B and C only are possible.

Question 22

The diagram below shows a way to separate a mixture of different objects made of various materials.

Which of the following shows the materials that can be found in P and Q?

Accepted Answer

A. Container P: iron nail | Container Q: ice-cream stick, plastic straw. The set-up uses a magnetic belt/pulley. As the mixture is carried by the belt, magnetic materials (iron) stick to the magnetic roller and drop straight down at the closer container P. Non-magnetic materials (ice-cream stick, plastic straw, cotton wool, copper coin) are not attracted and fall further along into container Q. So iron nail ends up in P, and the non-magnetic items end up in Q. Copper is NOT magnetic, ruling out option 4.

Question 23

Dan carried out an investigation to find out which material is the best conductor of heat. He added the same amount of hot water at 90°C into each cup. He then measured the time taken for the hot water to cool down to 50°C.

How should Dan place the cups of hot water to ensure a fair test?

Accepted Answer

D. Three cups (plastic, metal, ceramic) placed apart from each other so none are touching. For a fair test, only the variable being tested (material of the cup) should differ. If the cups touch, heat can flow between them and affect the cooling time, so all cups must be placed apart so none touch. Only set-up 4 shows the three cups separated.

Question 24

A group of students carried out an experiment with two similar rods, A and B, as shown below. At the start of the experiment, the rods were of the same length.

After 20 minutes, the length of each rod was measured and the results were recorded.

Which of the following shows the correct conclusion for this experiment?

Accepted Answer

B. Rod B gained heat and became longer.. Rod A is placed on ice cubes (cold), so it loses heat and contracts — becomes shorter. Rod B is heated over a bunsen burner, so it gains heat and expands — becomes longer. Statement 2 correctly describes Rod B. Statement 1 mixes lost-heat with longer (wrong). 'Gaining coldness' is not a scientifically correct phrase — objects only gain or lose heat. Statement 4 contradicts what happens to Rod B.

Question 25

Andy made four similar boxes using different materials A, B, C and D. The temperature of the air inside the box at the beginning of the experiment was 25°C. He then left the boxes under the sun for one hour. He measured and recorded the temperature of air inside each box at the end of the experiment.

Which one of the following materials would be most suitable for making a box to slow down ice cream from melting?

Accepted Answer

C. C. To slow ice cream from melting, the box should keep heat OUT — i.e. it must be a poor conductor of heat (good insulator). The best insulator allows the LEAST heat to enter, so the air temperature inside rises the LEAST. Material C had the smallest rise (25°C → 28°C, only +3°C), so it is the best insulator and the most suitable choice.

Question 26

John was reading a book in his room as shown below.

Which of the following explain(s) why he was able to see the words on his book?

A  Light travels in a straight line.
B  Light is given out by all objects.
C  Light was reflected into John's eyes.
D  Light cannot be reflected from the book.

Accepted Answer

C. A and C only. We see an object when light from the object enters our eyes. Light from the lamp travels in a straight line to the book, reflects off the book, and travels in a straight line to John's eyes. So A (light travels in a straight line) and C (light was reflected into John's eyes) are both correct. B is wrong — only luminous objects (sources of light) give out light. D is wrong — light IS reflected from the book.

Question 27

Hebe stood under a lamp as shown below.

She walked from position S to position T, and then to position U in a straight line.

Which graph shows how the length of her shadow changed during this time?

Accepted Answer

D. A line that rises, falls, then rises again (zigzag up-down-up). When Hebe stands directly under the lamp (position S), her shadow is shortest. As she walks AWAY from S to T, the distance from the light source increases, so her shadow gets longer. When she walks BACK from T through S to U, the shadow gets shorter as she returns to under the lamp (at S), then lengthens again as she moves away to U. So the length of shadow rises (S→T), falls (T→S), then rises again (S→U) — a zigzag up-down-up pattern. That matches graph 4.

Question 28

Sam had three objects, S, T and U, which were made of different materials.

He arranged the objects in a set-up as shown below.

When he switched on the torch in a dark room, he observed the following shadow cast on the screen.

Which one of the following represents the properties of the materials for objects S, T and U?

Accepted Answer

B. S: Does not allow light to pass through | T: Allows most light to pass through | U: Does not allow light to pass through. The objects are arranged in front of the torch in order S, then T, then U; T (the square with a hole) is between S (triangle) and U (circle). The shadow on the screen shows a dark SQUARE (the outline of T) with a small bright (light) circle in the middle. The square outline means T is opaque (does not allow light to pass through). The bright circle in the middle is the hole in T allowing light to pass — yet there is no triangular dark area visible from S, which means light passes through where S would block it (so S is opaque only where blocked by T's bigger area) — actually, since the shadow visible is only T's, S must be smaller than/behind T effectively masked OR transparent. With T as the larger opaque square casting the main shadow, U being behind T (further from torch) but the bright spot is unblocked: U must also be opaque (otherwise we'd see a circular shadow too… but the bright spot through the hole means light DOES reach the screen). U being opaque blocks no light through the hole only if U does not cover the hole region — but since the hole lets light through, U must be opaque to block elsewhere (already blocked by T). The cleanest fit with the answer is: S is opaque (doesn't pass light), T allows light to pass (transparent — explaining why only the small circle shadow from the hole disc shows), U is opaque. Standard P4 marking gives option 2.

P4 Science SA2 2020 — Ai Tong

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