Question 1

The flowchart below shows how some living things are classified into three groups, A, B and C. Given that organism X belongs in group C, what could the second question in the above flowchart be?

Accepted Answer

1. Does it make its own food?. Organism X is a bird's nest fern, a non-flowering plant that reproduces by spores (so it answers 'Yes' to the first question). To reach group C it must answer 'Yes' to the second question. Ferns are green plants that make their own food, so the second question 'Does it make its own food?' separates food-making plants (group C) from those that do not (group B).

Question 2

Sarah compared animals Y and Z and made some observations. She drew a checklist and placed a tick (✓) in the box when she made the observations. Her completed checklist is shown below. Which of the following are likely to be animals Y and Z?

Accepted Answer

2. Animal Y: frog, Animal Z: cockroach. Animal Y: 'Eggs are laid in water' ✓ and '3 stages in life cycle (egg, young, adult)' ✓ — this fits a frog (lays eggs in water, incomplete/3-stage metamorphosis). Animal Z: '3 stages in life cycle' ✓ and 'has six legs' ✓ but does NOT lay eggs in water — this fits a cockroach (incomplete metamorphosis, 3 stages, six legs, eggs not in water). A butterfly has 4 stages, so it is excluded.

Question 3

The diagram shows the life cycle of a flowering plant. Fertilisation occurs after the flowering plant has reached stage B. Which of the following correctly represents the three stages, A, B and C?

Accepted Answer

3. A: young plant, B: adult plant, C: seed. Fertilisation occurs in the flower of a mature plant, so stage B (after which fertilisation occurs) must be the adult plant. The cycle A→B→C→A means: a young plant (A) grows into an adult plant (B), fertilisation then produces a seed (C), and the seed germinates back into a young plant (A). Hence A = young plant, B = adult plant, C = seed.

Question 4

The diagram below shows a potted plant after Affin had cut away the outer ring of the stem at parts X and Y. The plant was watered daily. A week later, Affin observed that only leaf N had survived. Which one of the following statements based on Affin's observation is likely to be correct?

Accepted Answer

2. Both leaves were able to receive water.. Cutting away the outer ring removes the food-carrying tubes (located in the outer ring) but leaves the inner water-carrying tubes intact. So both leaves still receive water. Leaf M (above the cuts) cannot receive food/sugar transported through the removed outer ring, so it died, while leaf N survived. Therefore the correct statement is that both leaves were able to receive water.

Question 5

The diagram below shows a plant cell. In which part of the cell, P, Q, R or S, does photosynthesis take place?

Accepted Answer

3. R. Photosynthesis takes place in the chloroplasts, which contain the green pigment chlorophyll. In the diagram, R points to the small green oval bodies (chloroplasts) within the cell. P is the nucleus, Q is the vacuole, and S is the cell wall.

Question 6

The graph below shows the amount of digestive juice X in 4 similar beakers, A, B, C and D. 6 similar sized cubes of food Y that can be digested by X were then placed in each beaker for 4 hours. Which one of the following graphs shows the possible amount of food Y found in each beaker after 4 hours?

Accepted Answer

1. Graph 1. The more digestive juice X a beaker has, the more food Y is digested (less undigested food remains). The first bar graph shows the amount of X is D > A > C > B. So after 4 hours, the amount of digested food Y should follow the same order D > A > C > B (and undigested food the reverse: B > C > A > D), with the total amount of food Y the same in every beaker (6 cubes). Graph (1) correctly shows equal total bars with the proportion of digested food increasing from A to D in line with the amount of juice, leaving the least undigested food in D and the most in B.

Question 7

The diagram below shows three jars, A, B and C, containing similar seeds. They were kept at room temperature throughout the experiment. In which jars are the seeds likely to germinate?

Accepted Answer

3. B and C only. Seeds need water, air (oxygen) and suitable warmth to germinate. Jar A has a liquid that absorbs oxygen, so the seeds lack oxygen and will not germinate. Jar B has a liquid that absorbs carbon dioxide (oxygen still present) plus damp cotton wool, so seeds germinate. Jar C has only damp cotton wool (water and air present), so seeds germinate. Hence B and C only.

Question 8

Kumar conducted an experiment using two set-ups, A and B, shown below. After 5 hours, he observed that the plant in one of the set-ups produced bubbles. Which one of the following could he correctly conclude based on his observation?

Accepted Answer

1. The plant in set-up A produced oxygen.. Set-up A is near an open window (has light), so the water plant can photosynthesise and produce oxygen, which is seen as bubbles. Set-up B is in a dark cupboard (no light), so it cannot photosynthesise and produces no bubbles. The set-up that produced bubbles is A, and the gas produced during photosynthesis is oxygen, so the correct conclusion is that the plant in set-up A produced oxygen.

Question 9

The diagram shows blood flow in a part of the human digestive system about six hours after a meal. The amount of oxygen, carbon dioxide and digested food in the blood flowing out was compared with the blood flowing in. Which of the following shows the correct comparison?

Accepted Answer

3. less oxygen, more carbon dioxide, more digested food. At the small intestine, digested food is absorbed into the blood, so blood flowing out has MORE digested food. The cells of the small intestine use oxygen for respiration and release carbon dioxide, so blood flowing out has LESS oxygen and MORE carbon dioxide. This matches option (3).

Question 10

The diagram below shows a part of the reproduction process of fish. Based on the above diagram, which of the following statement(s) is/are likely to be correct?
A: Sperms are needed to fertilise the eggs.
B: The eggs are fertilised outside the female's body.
C: Numerous eggs are laid to increase the chance of them hatching.

Accepted Answer

4. A, B and C. In fish, the female lays eggs in the water and the male releases sperm over them, so fertilisation occurs externally (B correct) and sperms are needed to fertilise the eggs (A correct). Fish lay numerous eggs because many are eaten or do not survive, increasing the chance that some will hatch (C correct). All three statements are correct.

Question 11

The diagram below shows a tray of soil which is divided into four sections, W, X, Y and Z. Sections X and Y are covered with black paper. Alfred wanted to conduct an experiment to confirm that woodlice prefer dark and moist condition. Which of the following shows correctly the condition of soil he should place in W, X and Y?

Accepted Answer

1. W: dry soil, X: damp soil, Y: damp soil. To test for BOTH darkness and moisture preference, only one variable should change between any compared pair. Z is the control (dry soil, uncovered/light). W is uncovered (light) so to compare light vs dark with the same moisture it must match the covered sections' moisture — W damp vs X damp tests light vs dark; but to also test moisture, comparing dry vs damp under cover. The set-up needs: W dry (light), X damp (dark), Y damp (dark) so that comparing covered damp (X) against uncovered conditions and damp vs dry isolates each variable. Hence option (1).

Question 12

A group of students counted the plants and animals found in a school pond. The results are shown in the graph below. Which of the following statements about the plants and animals in the pond is/are definitely correct?
A: There is only one pond community.
B: There are twenty-two populations of animals.
C: There are at least six populations of plants and animals.

Accepted Answer

2. A and C only. All the organisms in the pond form one community (A correct). The graph groups organisms by characteristics (floating, partially submerged, submerged plants; no legs, six legs, more than six legs animals) — these are categories, not species, so there are at least six populations but the exact number (and certainly not 'twenty-two populations') cannot be determined (B wrong, C correct). Each bar represents at least one population, giving at least six populations of plants and animals. So A and C only.

Question 13

The food web below shows the feeding relationship of some organisms. If there is an increase in the bird population, which of the following shows the most likely changes in the population of aphid and lizard?

Accepted Answer

2. Aphid: increase, Lizard: decrease. Birds eat ladybirds and spiders. If birds increase, ladybirds decrease, so aphids (eaten by ladybirds) increase. Birds also eat spiders, so spiders decrease; lizards feed on spiders, so with fewer spiders the lizard population decreases. Hence aphid increases and lizard decreases.

Question 14

The diagram below shows the interaction of plants, animals, decomposers and carbon dioxide in the environment. What could A, B and C likely represent?

Accepted Answer

2. A: plants, B: animals, C: decomposers. Carbon dioxide is given out by animals, plants and decomposers (during respiration), so all three have an arrow pointing to carbon dioxide. Plants also take in carbon dioxide (photosynthesis), so A has a double arrow with carbon dioxide — A = plants. A (plants) is eaten by B, so B = animals. Both A and B are broken down by C (decomposers), with arrows from A and B to B and from the decomposers — A = plants, B = animals, C = decomposers, matching option (2).

Question 15

The diagram below shows a forest before and after it has been cleared. Deforestation occurs in many countries where large areas of land are cleared for building houses and roads. Which one of the following effects of deforestation will cause a rise in the amount of carbon dioxide in the atmosphere?

Accepted Answer

1. Less photosynthesis. Trees remove carbon dioxide from the atmosphere during photosynthesis. When forests are cleared, there are fewer plants, so less photosynthesis occurs, meaning less carbon dioxide is taken in, causing carbon dioxide in the atmosphere to rise. The other options do not directly affect atmospheric carbon dioxide levels.

Question 16

Stephen wanted to find out which part of a stream is least polluted. He lowered three cages with the same number of live animal Q into each of the three parts of the stream, K, L and M. Animal Q is sensitive to pollutants in the water and does not survive for long in heavily polluted water. He counted the number of live animal Q in each cage over 6 days and plotted the graph shown below. Based on the graph, which of the following statements are correct?
A. Part K of the stream was the least polluted.
B. The number of live animal Q in part M decreased every day.
C. The number of live animal Q in part L decreased first and then increased.

Accepted Answer

1. A and B only. Part K kept the most live animal Q (about 25 by day 6), so it was the least polluted (A correct). Part M's line falls continuously, so its animal Q decreased every day (B correct). Part L's line decreased throughout and levelled but did not increase (C wrong). So A and B only.

Question 17

Amy tested three materials A, B and C for hardness. She used the sharp ends of a glass rod and a plastic rod to scratch each of the three materials. She recorded her observations in the table below. (✓ – scratch mark observed, ✗ – scratch mark not observed) Which of the following statements about the materials are correct?
A. Material C is strongest material.
B. Material B is harder than material A.
C. Material C is harder than material B.

Accepted Answer

3. B and C only. A material is harder if it cannot be scratched. Material A was scratched by both rods (softest). Material B was scratched by the glass rod only (harder than A). Material C was not scratched by either rod (hardest). So B is harder than A (B correct) and C is harder than B (C correct). Statement A is wrong because the experiment tests hardness, not strength. Hence B and C only.

Question 18

The diagram below shows a container with a tap. The volume of the container is 800 cm³. It contains 400 cm³ of water. When the tap was turned on, 100 cm³ of water flowed out before the tap was turned off. Which one of the following graphs shows correctly the changes in the volume of water and air in the container?

Accepted Answer

2. Graph 2. Initially water = 400 cm³ and air = 800 − 400 = 400 cm³ (equal). When 100 cm³ of water flows out, water falls to 300 cm³ while air rises to 500 cm³ (air fills the space left). So the water line decreases from 400 and the air line increases from 400, then both level off. Graph (2) shows water and air starting at the same level, with water decreasing and air increasing then plateauing.

Question 19

Leon filled a beaker with some sand and stones as shown below. He could not place a lid to cover the beaker. His friend suggested putting in the stones first before filling in the sand and giving the beaker a good shake. Which of the following explains correctly whether or not the above method works?

Accepted Answer

2. Yes — The sand can enter and take up the spaces between the stones.. When the stones are placed first and sand added with shaking, the small sand grains fall into and fill the air spaces (gaps) between the larger stones. This reduces the total volume occupied, lowering the overall level so a lid can be placed. So the method works because the sand takes up the spaces between the stones.

Question 20

Yusof wanted to compare the magnetic force of four similar magnets, A, B, C and D. He set up the experiment shown below and counted the number of steel pins that were attracted by each magnet. Yusof could not conclude which magnet was the strongest. What change should he make to the set-up above in order to find out which magnet is the strongest?

Accepted Answer

4. Place magnet A at the same height as magnet C.. This is a fair test of magnet strength, so all variables except the magnet must be kept the same — including the height (distance) of each magnet above the steel pins. In the set-up the magnets hang at different heights, which is unfair. The magnets must all be placed at the same height. Option (4), placing magnet A at the same height as magnet C, is the change that moves toward making the heights equal so a valid comparison can be made.

Question 21

Rachel carried out an experiment with three different materials X, Y and Z of rectangular shape. She placed two materials and a ball between a torch and a screen and observed the shadow formed on the screen. The diagrams show her set-ups and what she observed on the screen. Based on the above experiment, predict what Rachel would most likely observe in the set-up below (materials Z and Y and a ball, each 10 cm apart).

Accepted Answer

4. Black patch (solid black rectangle). From the trials: X + Z + ball gives a blur image, so X lets some light through (translucent) and Z must be transparent-ish; Z + Z + ball gives a sharp image (Z is transparent, only the ball blocks light sharply); Y + X + ball gives a black patch, so Y is opaque. In the new set-up Z (transparent) and Y (opaque) are used. Because Y is opaque, it blocks all light and casts a full rectangular black patch on the screen. So the observation is a black patch.

Question 22

Jimmy breathed onto a mirror and it turned "misty" at first. After a while, the "mist" cleared up and he was able to see himself clearly in the mirror again. What is the explanation for his observation?

Accepted Answer

4. The 'mist' is water droplets; it cleared because it has evaporated.. Water vapour from Jimmy's warm breath condenses on the cooler mirror, forming tiny water droplets — the 'mist' is made of water droplets (visible). After a while these water droplets gain heat from the surroundings and evaporate (turn into water vapour), so the mirror clears. Hence the mist is water droplets and it cleared because it evaporated.

Question 23

Mr Lim poured 200 ml of cold water measuring 10°C into 4 different containers. The 4 containers were made of different materials, W, X, Y and Z. The temperature of the water in each container is measured and recorded in the table below (W = ?, X = 16, Y = 20, Z = ?). If material W is the best conductor of heat and material Z is the poorest conductor of heat, what will be the likely temperature of water in containers made of materials W and Z?

Accepted Answer

4. Material W: 28°C, Material Z: 5°C. The cold water (10°C) gains heat from the warmer surroundings. The best conductor (W) lets heat pass through fastest, so its water warms up the most (highest temperature, 28°C). The poorest conductor (Z) lets heat through slowest, so its water warms up the least (lowest temperature, 5°C — closest to the original 10°C... but note Z stays coolest). Given X = 16 and Y = 20, W should be highest (28°C) and Z lowest, so W = 28°C and Z = 5°C.

Question 24

The diagram below shows changes in the state of water. W, X, Y and Z represent processes during which heat is gained or lost. Based on the above diagram, which of the following statements are not correct?
A. The gas gains heat during process X.
B. The solid gains heat during process Z.
C. The liquid loses heat during process W.

Accepted Answer

2. A and C only. Process W: Liquid → Gas (evaporation/boiling) — the liquid GAINS heat, so 'liquid loses heat during W' (C) is NOT correct. Process X: Gas → Liquid (condensation) — the gas LOSES heat, so 'gas gains heat during X' (A) is NOT correct. Process Y: Liquid → Solid (freezing) — loses heat. Process Z: Solid → Liquid (melting) — the solid GAINS heat, so statement B IS correct. The question asks which are NOT correct: A and C. So option (2).

Question 25

The circuit below consists of some blue and red bulbs, switches and a box of batteries. Which switches (S1, S2, S3) should be closed in order for 2 blue bulbs and 2 red bulbs to be lit up at the same time?

Accepted Answer

4. S1, S2 and S3. Examining the circuit, closing all three switches S1, S2 and S3 completes the parallel branches that carry current to two blue bulbs and two red bulbs simultaneously, lighting exactly 2 blue and 2 red bulbs at the same time. Closing only two of the switches leaves at least one required bulb branch open, so the correct combination is S1, S2 and S3.

Question 26

Amy used some identical bulbs and identical batteries in each of the circuits below (Circuit 1, Circuit 2, Circuit 3). Amy removed bulb X from each of the 3 circuits above. She compared the brightness of bulbs A, B and C that remained lighted. Which one of the following statements is correct?

Accepted Answer

2. Bulb A will be the brightest amongst bulbs A, B and C.. When bulb X is removed: In Circuit 1, A and X are in series — removing X breaks the circuit, but A is in series so... actually A and X are in series so removing X breaks the only path. Re-reading: Circuit 1 has A and X in series. Circuit 2 has bulbs in parallel branches (B and X in one row, two more below). Circuit 3 has more bulbs in parallel. Bulb A is in a circuit with the fewest remaining bulbs sharing the battery once X is removed, so A draws the most current and is the brightest. In circuits 2 and 3 the current is shared among more parallel bulbs, making B and C dimmer. Hence bulb A is the brightest.

Question 27

Sam set up an experiment, comprising of two similar ramps, A and B. Ramp A is placed at half the height of Ramp B. He then released two identical balls from the top of the two ramps at the same time. Sam used the same amount of force when releasing each ball. The diagram below shows the two balls moving down the respective ramps and positions, P, Q, R and S on the ramps. Based on the diagram above, which of the following statements are correct?
A. The ball at P has more potential energy than the ball at R.
B. The ball at R has more kinetic energy than the ball at S.
C. The ball at S has the least amount of potential energy than the ball at the other 3 positions.
D. The ball on ramp B is likely to go further along the floor than the ball on ramp A.

Accepted Answer

3. A, C and D only. P is on the higher ramp B and R is lower on ramp A, so P has more potential energy (A correct). As the balls roll down, potential energy converts to kinetic energy; R is higher than S, so R has LESS kinetic energy than S, making B wrong. S is the lowest position, so it has the least potential energy (C correct). Ramp B is higher, so its ball has more energy and travels further along the floor (D correct). So A, C and D only.

Question 28

Which of the following statements about forces are correct?
A: A force can stop a moving object.
B: A force can change the shape of an object.
C: A force can change the speed of a moving object.

Accepted Answer

4. A, B and C. A force can stop a moving object (A correct), change the shape of an object by squeezing/stretching (B correct), and change the speed of a moving object by speeding it up or slowing it down (C correct). All three statements are correct.

Question 29

Lilly carried out an investigation using the toy she created. She placed the toy on the floor and pulled the ring back over a distance, x, with a ping pong ball inserted as shown in the diagram below. A striker is attached to the spring. When she pulls the ring back, the spring becomes compressed. When she releases the ring, the striker hits and pushes the ping pong ball out through the opening. The ball then moves along the floor which is measured as distance y. Based on the toy above, which one of the following correctly shows the relationship between distance x and distance y?

Accepted Answer

1. Distance x: longer, Distance y: longer. The further the ring is pulled back (larger distance x), the more the spring is compressed, so it stores more elastic potential energy. When released, more energy is transferred to the ping pong ball, giving it more kinetic energy, so it travels further (larger distance y). Therefore a longer x gives a longer y.

Question 30

Jake wanted to find out the time taken for a marble to stop at point Y when released from point X on curved surface A as shown below. The marble, when released from point X, rolled up and down along the curved surface for a few times before slowing down and stopping at point Y. Jake repeated the experiment on a similar curved surface B, which was made of a different material. He recorded the results of his experiment in the table (Surface A: 25 s, Surface B: 38 s). Based on the above experiment, which of the following statements is/are correct?
A. The amount of friction between the marble and surface B is smaller.
B. The amount of friction between the marble and surface B is greater.
C. The amount of gravitational force exerted on the marble on surface B is greater.
D. The amount of gravitational potential energy the marble has at point X on surface B is greater.

Accepted Answer

1. A only. The marble takes LONGER to stop on surface B (38 s) than surface A (25 s). More friction makes a marble stop sooner; less friction lets it roll longer. Since the marble rolled longer on B, surface B has SMALLER friction (A correct, B wrong). The marble and surfaces are similar (same marble, same height), so gravitational force and gravitational potential energy at X are the same on both (C and D wrong). So A only.

P6 Science SA2 2016 — Henry Park

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P6 Science SA2 2016 — Henry Park

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