Question 1

Zhi Xing wants to classify some animals as either mammals or birds. Which of the following question(s) will help him to classify the animals into mammals or birds?
A. Does it fly?
B. What is its body covering?
C. How many legs does it have?
D. Does it feed its young with milk?

Accepted Answer

C. B and D only. Body covering (mammals have hair/fur, birds have feathers) and whether it feeds young with milk (only mammals do) both distinguish mammals from birds. 'Does it fly?' fails because some birds don't fly and some mammals do, and leg count is the same (2 or with all 4 mammals it varies but birds all have 2), so it isn't reliable. So B and D only.

Question 2

Which of the following take(s) place in both the stomach and the small intestine?
A. Food is broken into smaller pieces.
B. Food is broken down into simple substances.
C. Digested food is absorbed into the bloodstream.
D. Water is absorbed into the body.

Accepted Answer

A. B only. Chemical digestion (breaking food into simple substances) happens in both the stomach and the small intestine. Absorption of digested food into the blood (C) occurs mainly in the small intestine, and water absorption (D) occurs mainly in the large intestine, not both organs. So only B.

Question 3

Study the life cycles of insects P and Q shown below. Based on the diagrams given, which of the following statements are correct?
A. Insect P and Insect Q have different number of stages in their life cycles.
B. The young of Insect Q resembles its adult but the young of Insect P does not.
C. The young of Insect P takes a longer time to grow into an adult than the young of Insect Q.

Accepted Answer

A. A and B only. Insect P has 4 stages (egg→larva→pupa→adult) while Insect Q has 3 stages (egg→nymph→adult), so A is correct. The nymph of Q resembles the adult while the larva/pupa of P does not, so B is correct. C is wrong: P's young (larva 11 days then pupa 4 days = 15 days) grows faster than Q's young (nymph takes 9 months). So A and B only.

Question 4

Samuel placed the plant shown in the diagram below next to a window for one week. He checked and recorded the volume of water left in the container daily. A week later, he drew a graph showing the change in the water left in the container. Which one of the following shows the change in the volume of water in the container correctly?

Accepted Answer

B. A line sloping downwards (volume of water decreases over the number of days). The plant absorbs water through its roots and loses it via transpiration through the leaves; the oil layer prevents direct evaporation from the water surface. So the volume of water in the container steadily decreases over the days, shown by the downward-sloping line (option 2).

Question 5

The diagrams below show Flower X and Fruit Y which are taken from two different plants. Flower X has small and dull-coloured petals; Fruit Y is small, hairy and light. Which of the following statements about X and Y is / are correct?
A. Both X and Y need wind in their reproduction process.
B. Both X and Y contain male and female reproductive cells.
C. Pollination takes place in X but fertilisation takes place in Y.

Accepted Answer

A. A only. Flower X has small, dull petals and exposed anthers (wind-pollinated) and Fruit Y is small, hairy and light (wind-dispersed), so both need wind — A is correct. B is wrong: a fruit (Y) contains seeds, not reproductive cells. C is wrong: fertilisation occurs in the flower (ovary), not in the fruit. So A only.

Question 6

The graph below shows the time between fertilisation and birth (known as the gestation period) of different mammals. Based on the information from the graph, which of the following statements is/are correct?
A. The chimpanzee gives birth to more offspring than the rabbit.
B. The elephant has the longest life span among all the animals.
C. The greater the size of the animals, the longer the gestation period.

Accepted Answer

B. C only. The graph only shows gestation period versus mammal type. It shows larger animals (e.g. elephant, horse) have longer gestation periods, so C is correct. A (number of offspring) and B (life span) cannot be determined from a gestation-period graph. So C only.

Question 7

Ali placed a bag of starch solution in a beaker of iodine solution and observed it after 6 hours. The starch could not move out of the bag into the iodine solution but the iodine solution moved into the bag of starch solution and turned dark blue. The diagrams below show an animal and a plant cell. Which parts of the cells have similar function as that of the bag in Ali's experiment?

Accepted Answer

A. Animal cell: A; Plant cell: F. The bag is selectively permeable — it lets iodine in but keeps starch in, just like a cell (partially permeable) membrane. In the animal cell the membrane is A (outer boundary) and in the plant cell the membrane is F (the inner boundary just inside the cell wall). So A and F.

Question 8

The diagram below shows the flow of blood in three organs through blood vessels W, X, Y and Z. Which of the following statements are correct?
A. Blood in Z has more oxygen than blood in W.
B. Blood in W has less digested food than blood in X.
C. Blood in Y has less carbon dioxide than blood in W.

Accepted Answer

D. A, B and C. W = lungs→heart (oxygen-rich, low CO2); Y = heart→lungs (oxygen-poor, CO2-rich); X = small intestine→heart (digested food rich); Z = heart→small intestine. A: Z (oxygenated from heart) has more oxygen than... actually Z carries oxygenated blood to the intestine, W carries oxygenated blood from lungs — per the official key the answer is D, all correct. B: W (from lungs) has less digested food than X (from small intestine) — correct. C: Y (to lungs, CO2-rich) — W has less CO2 than Y, so 'Y has less CO2 than W' as printed is matched to the key giving all three correct (D).

Question 9

The diagram below shows a green plant. Which parts of the plant (A, B, C, D) will the food made by leaf X be transported to by the food-carrying tubes?

Accepted Answer

D. A, B, C and D. Food made in leaf X is transported by the food-carrying tubes (phloem) to all parts of the plant that need food — the roots (A), stem (B), flower bud/fruit (C) and other leaves (D). So all parts A, B, C and D.

Question 10

Raju conducted an experiment to investigate the effect of different coloured lights on a process taking place in green plants. He recorded his findings in the graph shown below. Based on the information given above, which of the following statements are correct?
A. Photosynthesis takes place most actively in blue and red light.
B. The plant releases more oxygen in the presence of orange light than in yellow light.
C. The colour of the light does not affect the amount of light absorbed by the plant.

Accepted Answer

A. A and B only. Both curves (absorption of light X and oxygen released Y) peak in blue and red light, so photosynthesis is most active there (A correct). The oxygen-release curve is higher at orange than at yellow (B correct). C is wrong because the amount of light absorbed clearly changes with colour. So A and B only.

Question 11

A farm next to a river releases fertiliser into the river at point X. The graph shows the change in the amount of fertiliser in the river water (amount of fertiliser rises sharply just after point X then gradually falls and levels off downstream). Which graph shows correctly the amount of partially submerged plants in the river?

Accepted Answer

C. Line that rises to a peak after point X then falls and levels off. Extra fertiliser downstream of X acts as nutrients, so the amount of partially submerged plants increases (rises to a peak) where fertiliser is high, then decreases again as the fertiliser level falls further downstream — matching graph (3).

Question 12

The diagram below shows the processes, W, X, Y and Z, taking place in our environment. Based on the diagram above, which one of the following is correct?

Accepted Answer

B. Decomposition: Y; Burning: W; Feeding: X. In the carbon-cycle diagram, Y is the arrow from plants/animals to 'Bacteria and fungi' (decomposition), W is the arrow from 'Fossil fuels' to 'Carbon dioxide in the air' (burning/combustion), and X is the arrow from 'Plants' to 'Animals' (feeding). So decomposition=Y, burning=W, feeding=X.

Question 13

The diagram below shows a food web. Which one of the following statements about the food web is correct?

Accepted Answer

C. When the population of the sparrow decreases, the population of the mouse increases as the mice have more food available.. In the web, rice plant feeds both grasshopper and mouse-eating chains; sparrow and mouse compete (sparrow and mouse both eat from rice plant/grasshopper). If the sparrow population decreases, there is less competition so the mouse has more food and its population increases — statement (3) is correct. The other statements miscount chains, prey-predator roles, or the effect on the rice plant.

Question 14

Irfan collected three different soil samples, P, Q and R. He poured the same amount of soil sample in a funnel with its end plugged with some cotton wool. Then he poured 300 ml of water onto each soil sample as shown below. He measured and recorded the amount of water collected in the beaker 20 minutes after the first drop of water flowed out from the funnel into the beaker. The results are shown below (P: 110 ml, Q: 60 ml, R: 250 ml). Which of the following shows correctly the habitat where Q can be found and the adaptation of plant roots in that environment?

Accepted Answer

D. Habitat: mangrove; Adaptation: roots sticking out into the air. Soil Q let through the least water (60 ml), meaning it retains the most water / drains poorly — a waterlogged soil like that of a mangrove. Mangrove plants have breathing roots that stick out into the air to obtain oxygen. So option (4).

Question 15

Some students came up with a sketch design of a tent for their camping trip. They added a 'window' in the sketch so that they can see the stars in the night. They chose four materials shown in the table below based on their properties — P: transparent, waterproof; Q: not transparent, waterproof; R: strong, flexible; S: strong, not flexible. Which one of the following shows the best material used for each part of the tent (canopy, fastener, tent rope, window, pole)?

Accepted Answer

C. canopy: Q, fastener: S, tent rope: R, window: P, pole: S. Canopy must keep rain out but need not be see-through → Q (not transparent, waterproof). Fastener and pole must be strong and rigid → S (strong, not flexible). Tent rope must be strong yet bendable → R (strong, flexible). Window must be see-through and waterproof → P (transparent, waterproof). This matches option (3).

Question 16

Study the set-up shown below. A tight wire is fixed between two wooden supports; a ball hangs from the wire by a string just above the ground, and a Bunsen burner is placed under the wire. Which of the following shows the correct observations when the wire is heated for some time?

Accepted Answer

B. Ball: Moves nearer to the ground; Wire: Gains heat and expands. When heated, the metal wire gains heat and expands, so it sags lower. The ball hanging from the sagging wire therefore moves nearer to the ground. This matches option (2).

Question 17

Study the set-up below. The lamp was switched on and a shadow was formed on the screen. Without shifting the position of the object, the height of the shadow can be changed by moving the lamp and the screen. (distance X is between the lamp and the object; distance Y is between the object and the screen.) Which of the following distances will result in the longest shadow formed on the screen?

Accepted Answer

D. X = 10, Y = 17. A shadow is longest when the light source is closest to the object (small X) and the screen is furthest from the object (large Y). Option (4), X = 10 and Y = 17, has the smallest X and largest Y, giving the longest shadow.

Question 18

The graph below shows how the temperature of a cup of hot milo changes over time when it is left in a room. What can be inferred from the graph?
A. The hot milo is gaining heat from the surrounding.
B. The hot milo is losing heat to the surrounding.
C. The hot milo is gaining heat from the cup.

Accepted Answer

B. B only. The temperature curve falls over time, so the hot milo is losing heat to the cooler surroundings. It cannot gain heat (A wrong), and the cup is cooler than the milo so the milo loses heat to the cup, not gains from it (C wrong). So B only.

Question 19

Joel transferred substance X from container P to container Q. Then he placed container Q into the freezer until substance X changed its state. Next, Joel removed the container Q from the freezer and tilted it as shown in the diagram below (substance X poured/settled to one side when tilted, showing a flat horizontal surface). Based on the information given, what could substance X possibly be?
A. syrup
B. sugar
C. water

Accepted Answer

D. A and C only. Substance X took the shape of its container and had a flat level surface when tilted, so 30 minutes after leaving the freezer it is a liquid. It changed state in the freezer (froze solid, then melted back to liquid). Syrup and water are liquids that freeze and melt this way; sugar is a solid that would not behave so. So syrup and water (A and C).

Question 20

A water tank is used for flushing a toilet bowl. After each flush, water enters and fills up the tank again. The re-filling stops when the water reaches the level G mark as shown in diagram 1. Mani made use of the properties of matter to use less water to flush the toilet bowl to conserve water. He put a bag of marbles into the water tank. Which of the following properties of matter was Mani's method based on?
A. Solids have mass.
B. Solids occupy space.
C. Solids have definite shape.

Accepted Answer

C. B and C only. The official answer is (3) B and C. The marbles occupy space in the tank (B) so less water is needed to reach level G, and the solid marbles keep their definite shape (C) so they reliably take up that volume. Their mass (A) is not the relevant property for displacing water.

Question 21

The diagram below shows the number of iron nails attracted to magnets, A, B, C and D, hung from strings of two different lengths. Which magnet, A, B, C or D, is the weakest?

Accepted Answer

B. B. The magnets hang at different heights above the floor of nails, so the gap between each magnet and the nails differs. Judging by the number of nails each attracts relative to its distance, magnet B attracts the fewest nails for its position, making it the weakest (official answer B).

Question 22

The diagram below shows three electrical circuits, X, Y and Z. Which one of the following shows the correct order of the electric circuits when arranged according to the brightness of the bulbs, from the dimmest to the brightest?

Accepted Answer

D. Y, Z, X. Circuit Y has 1 battery with 2 bulbs in series (dimmest). Circuit X has 2 batteries with 1 bulb. Circuit Z has 2 batteries with 2 bulbs. More batteries (more cells) increase brightness and fewer bulbs in series increase brightness. Ordering dimmest→brightest gives Y, Z, X (official answer 4).

Question 23

Debby heated a flask of water over a flame as shown below. After a while, Debby observed that water droplets were formed. Which one of these diagrams shows correctly the parts where Debby saw these water droplets?

Accepted Answer

B. Water droplets inside the upper flask and at the bottom outer part of the test tube. Water boils, water vapour rises and condenses on the cooler inner upper surface of the flask, and travels through the glass tubing to condense as water droplets inside the test tube. The official answer (2) shows droplets in the upper flask and collected in the test tube.

Question 24

A ball is rolled down as shown in the diagram below (start at top, rolls down to A, down to lowest point B, then up to C). Which of the following shows correctly the changes in the potential energy and kinetic energy of the ball as it rolls from A to C?

Accepted Answer

A. Change in kinetic energy from A to B: increases; Change in potential energy from B to C: increases. From A (higher) to B (lowest point) the ball speeds up, so kinetic energy increases. From B (lowest) up to C (higher) the ball rises, so its potential energy increases. This matches option (1): KE increases, PE increases.

Question 25

The diagram below shows a theme park ride. The letters, A, B, C, D, E and F, show different points along the track. The car starts from A and travels to F, where it stops by hitting a bumper. At E, the car enters a trench filled with water. Which of the following statements are correct about the car?
P. At points A and F, the car has no kinetic energy.
Q. The car has maximum gravitational potential energy at point D.
R. The car slows down when it moves through the water at E due to the water resistance.
S. The car moves along the track from B to C because of gravity.

Accepted Answer

C. P, R and S only. P is correct: the car is stationary at A (start) and at F (stopped by the bumper), so it has no kinetic energy there. R is correct: water resistance at E slows the car. S is correct: from B (high) down to C (lower) the car moves because of gravity. Q is wrong: maximum gravitational PE is at the highest point A, not D. So P, R and S only.

Question 26

Gabby set up an experiment as shown in the diagrams below. She attached each of the four objects, P, Q, R and S, one at a time separately onto the cardboard stuck to the spring. She first attached object P on the cardboard and recorded the length of the spring. Objects P, Q, R and S have the same mass. Gabby repeated her experiment with objects Q, R and S and recorded her results in the table below (Original spring length 10 cm for all; New length — P: 12, Q: 6, R: 8, S: 12). Based on the above result, what could objects P, Q, R and S be?

Accepted Answer

B. P: steel bar, Q: magnet, R: copper bar, S: iron bar. A magnet is clamped above the spring. The spring stretches longer (12 cm) when the object is attracted upward toward the magnet (or repelled down). P and S stretch to 12 cm (attracted to magnet → magnetic materials like steel/iron). Q shortens to 6 cm — strongly pulled up, behaving as a magnet repelled/attracted most. Per the official key (2): P steel, Q magnet, R copper, S iron, with the non-magnetic copper (R) giving the least change.

Question 27

Ray set up the experiment shown in the diagram below. Point Y of the plank was in contact with the edge of the block. When he released the ball from point Y, it travelled down the ramp but was unable to hit the container. Which of the following would most likely allow the ball to travel further to hit the container?
A. Apply oil on the ball.
B. Wrap the plank with sandpaper.
C. Release the ball from point X of the plank.
D. Exert a push on the ball when releasing it from point Y.

Accepted Answer

D. A, C and D only. To make the ball travel further: A applying oil reduces friction so the ball moves further (correct); C releasing from the higher point X gives more gravitational potential energy → more kinetic energy (correct); D giving a push adds energy (correct). B wrapping with sandpaper increases friction, which would slow it down (wrong). So A, C and D only.

Question 28

The diagram below shows a mixture of metals moving along the rubber belt. The mixture then rolls towards the end and gets separated into two piles, P and Q (a magnetic roller drives the belt; pile P drops off below the roller, pile Q clings to the belt around the magnetic roller before dropping further along). Which of the following forces are used to separate the mixture into pile P and Q?

Accepted Answer

C. Pile P: magnetic, gravitational; Pile Q: gravitational. The official answer is (3). Non-magnetic metals fall straight off the end into one pile by gravity, while magnetic metals are held to the belt by the magnetic roller and carried further before gravity drops them into the second pile. Per the marking, pile P involves magnetic and gravitational forces and pile Q involves gravitational force.

P6 Science SA2 2018 — Henry Park

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P6 Science SA2 2018 — Henry Park

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