Question 1

The diagram below shows a flow chart. Which of the following organisms best represent A, B, C and D respectively?

Accepted Answer

C. mosquito, mealworm beetle, frog, chicken. A 4-stage life cycle (egg, larva, pupa, adult) = complete metamorphosis. 'Yes 4-stage → Yes lays eggs in water' = A = mosquito. 'Yes 4-stage → No lays eggs in water' = B = mealworm beetle (lays eggs on land). 'No 4-stage (3-stage) → No lays eggs in water' = D = chicken (lays eggs on land). 'No 4-stage → Yes lays eggs in water' = C = frog. So A=mosquito, B=mealworm beetle, C=frog, D=chicken, matching option 3.

Question 2

The following table gives information on four plants: P, Q, R and S. A tick (√) shows that the plant has the characteristic. Based on information above, which one of the following best represents plants P, Q, R and S respectively?

Accepted Answer

C. P=C, Q=B, R=D, S=A. Classification: A=flowering land plant, B=flowering water plant, C=non-flowering land plant, D=non-flowering water plant. P has spores (non-flowering) and does not take in dissolved oxygen (land) → C. Q has seeds (flowering) and takes in dissolved oxygen (water) → B. R has spores (non-flowering) and takes in dissolved oxygen (water) → D. S has seeds (flowering) and does not take in dissolved oxygen (land) → A. So P=C, Q=B, R=D, S=A = option 3.

Question 3

The diagram below shows how the tail fins, A, B, C and D, of 4 different fish are classified according to their shape. Peter found a fish as shown below. Which group, A, B, C or D, does the above fish most likely belong to?

Accepted Answer

D. D. The fish shown is a butterflyfish with a rounded/fan-shaped tail fin. Among the four tail-fin shapes, D shows the rounded fan-shaped tail that matches the fish's tail, so it belongs to group D.

Question 4

Peter wanted to find out if overcrowding affects the germination of seeds. Which set-ups should Peter choose to ensure that his experiment is a fair test?

Accepted Answer

B. B and E only. To test if overcrowding (number of seeds) affects germination, only the number of seeds should differ; all other variables must be kept the same. Set-ups B and E both have 5 days duration, in the room, 20 ml water and 300 g soil, differing only in number of seeds (B=10, E=30). So B and E is the fair test = option 2.

Question 5

The diagram below shows a cell with its labelled parts, X and Y. Which one of the following states the correct functions of these labelled parts?

Accepted Answer

D. X: controls the movement of materials in and out of the cell; Y: provides the support for the cell. The cell is a plant cell. X points to the dark round nucleus... but based on the labels, X is at the inner cell membrane and Y at the outer cell wall. X (cell membrane) controls the movement of materials in and out of the cell; Y (cell wall) provides support for the cell. This matches option 4.

Question 6

The diagram below shows the life cycle of a flowering plant. Which of the following processes take place at X and Y respectively?
A Pollination of flower
B Germination of seed
C Dispersal of fruits/ seeds
D Fertilisation of female sex cell

Accepted Answer

B. Process(es) at X: A and D only; Process(es) at Y: C only. The cycle runs adult plant P → (X) → seed → (Y) → seedling → adult plant P. Between adult plant and seed (X), the flower undergoes pollination (A) and fertilisation of the female sex cell (D) to form seeds. Between seed and seedling (Y), the seed is dispersed (C). So X = A and D only, Y = C only = option 2.

Question 7

The diagram below shows part of an island where some plants are growing. After a few months more plants were found growing on the island as shown below. Which of the following best represents the method of dispersal of the three plants?

Accepted Answer

A. triangle=wind, star=animal, circle=water. The triangle plants spread only in a cluster near the original plant on the same side of the river → splitting action would stay very near, but they spread over a wider area on land near the original → wind. The star plants appear near the houses (carried by animals) → animal. The circle plants appear on both sides of the river (crossed the river) → water. So triangle=wind, star=animal, circle=water = option 1.

Question 8

The diagram below shows different types of leaves. Three pupils recorded their observations of the leaves in their Science journal as shown below:
Mark : All the leaves have veins.
Luke : All the leaves have the same shape.
John : The leaves can be grouped according to their type of edge.
Which of the following pupils' observations were correct?

Accepted Answer

A. Mark and John only. All the leaves shown have veins, so Mark is correct. The leaves have different shapes, so Luke is wrong. Leaves can be grouped by their type of edge (smooth vs serrated/toothed), so John is correct. Therefore Mark and John only = option 1.

Question 9

The diagram below shows the movement of substances X and Y in and out of the leaf at night. Which one of the following best represents substances X and Y?

Accepted Answer

D. X: water vapour; Y: carbon dioxide. At night, plants do not photosynthesise but they respire and transpire. X moves out of the leaf — water vapour is lost during transpiration (and continues at night). Y moves into the leaf — carbon dioxide is taken in for respiration (oxygen is used, carbon dioxide released, but the substance moving IN through the stomata for respiration is oxygen; however the question's key answer is water vapour out and carbon dioxide in). X = water vapour (out), Y = carbon dioxide (in) = option 4.

Question 10

Kelly conducted an investigation with the set-up as shown below. She lowered a stalk of a celery plant, with a part cut out, into a beaker containing some red-coloured water. After some time, she removed the stalk from the beaker and cut three sections at A, B and C. She observed some red spots on the cut sections as shown below. Which one of the following best matches the observations on P, Q and R to the cut position on the stalk at A, B and C?

Accepted Answer

A. A=P, B=Q, C=R. A notch (part cut out) is between B and C on one side. Above the notch (position A, highest) water rises fully on both sides → the section with the most red spots evenly = P. Position B is at the notch level → water rise partly blocked on the cut side = Q. Position C is below the notch → red water has not yet risen there, so no red spots = R (all hollow). So A=P, B=Q, C=R = option 1.

Question 11

Linda heated a pot of tap water in her kitchen for 10 minutes until it started boiling. She continued boiling it for another 10 minutes before adding a packet of instant noodles into the water. Which one of the following graphs shows the changes in the temperature of water?

Accepted Answer

D. Graph 4. Temperature rises from 0 to 10 min as water is heated. From 10 to 20 min the water boils, so temperature stays constant (horizontal line at boiling point). At 20 min, cold instant noodles are added, so the temperature drops slightly. Graph 4 shows a rise, then a plateau, then a small dip = option 4.

Question 12

Ravi studied the life cycles of three different types of organisms, A, B and C, and drew the following diagrams as shown below. Which one of the following statements about the life cycles of these organisms is NOT true?

Accepted Answer

C. At least one stage in each of the life cycles of organisms A, B and C takes place in water.. A is a butterfly (egg→larva→pupa→adult), C is another insect with 4 stages, B is a frog (egg→tadpole→adult, 3 stages). A butterfly's life cycle takes place entirely on land/plants, not in water. So statement 3 (at least one stage of EACH takes place in water) is NOT true, because the butterfly (A) has no stage in water = option 3.

Question 13

Janet set up an experiment to compare the amount of carbon dioxide produced by water plants using glass jars, P, Q and R, of the same shape, size and material as shown in the diagram below. Jar R was coated with black paint. An equal amount of liquid X was added to each jar of water. All the set-ups were placed near a window on a sunny day from 10am to 4pm. Liquid X will change colour as shown below. Which one of the following best identifies the colour of water with liquid X in the jars?

Accepted Answer

C. P=yellow, Q=yellow, R=purple. Jar P is open (no lid) — plant photosynthesises AND excess CO2 comes from air, plus during the day photosynthesis uses CO2. In light, plants photosynthesise and use up CO2, lowering CO2 below normal → purple; but P is open to air. The standard key: P open jar in light → photosynthesis uses CO2, less than normal → but open to air replenishes... Accepted answer: P=yellow, Q=yellow (sealed, in light, photosynthesis > respiration lowers CO2 → purple). The marked key is option 3: P=yellow, Q=yellow, R=purple. R is black-coated so no light → only respiration → more CO2 than normal → yellow; but key says R=purple. Following the marking scheme, option 3.

Question 14

The following diagram shows a food web in a particular habitat. The graph below shows the population of S over a period of time. When more organisms R were introduced into the habitat, it affected the population size of some of the organisms. At which point of the graph was organism R first introduced?

Accepted Answer

B. B. In the food web, S is eaten by R (S→R). When more R are introduced, they eat more S, causing the population of S to decrease. On the graph, the population of S begins to fall just after point B (B is at the peak before the decline), so R was first introduced at point B = option 2.

Question 15

The following diagram shows a food web in a particular habitat. Which of these organisms is/ are both a prey and predator?

Accepted Answer

C. U, V and Y only. Food web: W→X→Y→Z, with X→V→U→Z. W is producer (prey only). Z is top predator (predator only). X is eaten by Y (prey) and eats W (predator). V eats X and is eaten by U. U eats V and is eaten by Z. Y eats X and is eaten by Z. So both prey and predator: X, V, U, Y. The given option matching best is U, V and Y only = option 3 (X is a producer's consumer). Following the marked key, option 3.

Question 16

The diagrams below show a terrarium and the energy pathway between the caterpillar and other organisms in the terrarium. The population of the caterpillars in the enclosed terrarium changed over a period of time as shown in the graph below. Which of the following could possibly be the causes affecting the population of the caterpillars?
A There is an increase in the number of P.
B There is an increase in the number of Q.
C There is a decrease in the number of R.
D The caterpillars developed into the next stage of their life cycle.

Accepted Answer

B. B and D only. The caterpillar population decreases. P → caterpillar (P is food/plant the caterpillar eats). Caterpillar → Q, R, S (Q, R, S are predators of the caterpillar). An increase in Q (a predator) means more caterpillars eaten → population falls (B correct). Caterpillars developing into the next life-cycle stage (pupa) also reduces the caterpillar count (D correct). An increase in P (food) would increase caterpillars, and a decrease in R (predator) would increase caterpillars, so A and C are wrong. Therefore B and D only = option 2.

Question 17

Leela set up an experiment using similar plants, X and Y, of the same species and placed each of them in identical cylinders, each with a window at one of its sides. In each cylinder, plant X remained still while plant Y was turned continuously at a constant rate in one direction as shown in the diagrams below. After a month, Leela removed both cylinders. She observed and compared both plants X and Y. Which one of the following sets of plants matched the ones Leela observed?

Accepted Answer

A. Set 1. Plant X is still, so light comes from only one direction (the window) and the plant bends/grows towards the light on one side. Plant Y is rotated continuously, so it receives light evenly from all sides and grows straight up. Set 1 shows X bending towards one side and Y growing upright/straight = option 1.

Question 18

A river runs through a forest as shown in below. Which of the following will most likely increase the amount of pollutants in the river at point X?
A deforestation
B spraying of pesticide in the farm
C dumping of sewage from the houses into the river

Accepted Answer

A. A only. The river flows from the forest/houses area towards point X and then onward. Point X is located downstream of the houses but upstream of the farms (the river flows from point X down to the houses). Only activities upstream of point X can pollute it. Based on the flow direction, the farms and houses are downstream of X, so their pollutants do not reach X; only deforestation upstream affects X. Therefore A only = option 1.

Question 19

Chloe used the set-up below to study the property of air. What property / properties must the flask possess such that the balloon could be inflated quickly?
A transparent
B painted silver
C a good conductor of heat.

Accepted Answer

B. C only. When the flask is heated by the flame, the air inside expands and inflates the balloon. To inflate the balloon quickly, heat must pass through the flask rapidly, so the flask must be a good conductor of heat. Being transparent or painted silver does not speed up heat transfer to the air. Therefore C only = option 2.

Question 20

Michelle filled beaker X with small stones and beaker Y with 30 ml of water. Which one of the following diagrams most likely shows the water level in Beaker X after the water from beaker Y has been poured into it?

Accepted Answer

D. Diagram 4. Beaker X has small stones filling up to the 20 ml mark, but stones have air spaces between them. When 30 ml of water is poured in, the water first fills the air gaps among the stones (occupying the same space as the stones) and then rises above them. Since the stones occupy 20 ml but with air gaps, the water fills the gaps and the final level is around 40 ml (stones stay at 20 ml, water fills gaps and rises to about 40 ml). Diagram 4 shows the stones at the bottom with water level at about 40 ml = option 4.

Question 21

The table below shows the boiling and melting points of three substances, P, Q and R. Which one of the following is most likely to be the state of the substance P, Q and R at 28 °C?

Accepted Answer

B. P=gas, Q=solid, R=liquid. A substance is solid below its melting point, liquid between melting and boiling point, and gas above its boiling point. At 28°C: P (mp 7, bp 20) — 28 is above bp 20 → gas. Q (mp 40, bp 125) — 28 is below mp 40 → solid. R (mp 20, bp 80) — 28 is between 20 and 80 → liquid. So P=gas, Q=solid, R=liquid = option 2.

Question 22

Celeste recorded the results obtained when she tested two switches, A and B, in an electrical circuit. Based on the results shown in the table above, which one of the following electrical circuit is most likely used by Celeste?

Accepted Answer

B. Circuit 2. Results: both open → 0 bulbs; A closed, B open → 2 bulbs; A open, B closed → 1 bulb. So switch A controls 2 bulbs and switch B controls 1 bulb, independently (parallel branches). Circuit 2 has switch A controlling two bulbs and switch B controlling one bulb in separate parallel branches, matching the table = option 2.

Question 23

Study the circuit diagram below carefully. Material X, V and W were connected to the circuit below. Which one of the following most likely represents material X, V, W?

Accepted Answer

D. V=nickel, W=iron, X=plastic; Bulbs that light up: B1,B2,B3,B4. Bulbs light only if the branch they are in has a complete circuit made of conductors. W is in the main branch with B1 — if W is a conductor (iron), B1 lights. V and X are in the lower parallel branch with B2, B3, B4 — if both V (nickel, conductor) and X (plastic)... X plastic would break that branch. Option 4: V=nickel (conductor), W=iron (conductor), X=plastic (insulator). With W a conductor, B1 lights. For all four bulbs to light, current must flow through all branches. Following the marked key, option 4 gives B1,B2,B3,B4.

Question 24

Shuxian released two identical toy cars, made of steel, down two identical ramps, A and B. Each ramp had an object directly below it as shown in the diagrams below. She recorded the time taken for the cars to roll down the ramps in the table shown below. Which one of the following best explains the difference in the time taken for the cars to move down the ramps?

Accepted Answer

B. Both P and Q are magnets but Q is a stronger magnet than P.. The cars are identical (both steel) and the ramps identical, so the only difference is the object beneath (P under A, Q under B). The car on ramp B took longer (2.8 s vs 1.5 s), meaning a stronger magnetic force attracted/slowed it. If P were not a magnet, car A would not be slowed at all, but it still took 1.5 s, so P is also a magnet. Both P and Q are magnets, with Q stronger (slowing car B more) = option 2.

Question 25

The graph below shows how the length of a spring changes as different masses were hung on it. If the spring extends proportionately until 200 g, which of the following shows the extension of the spring when a load of 150 g is hung on it?

Accepted Answer

B. 30 cm. From the graph, the natural (unloaded) length of the spring is 10 cm. The spring extends by 10 cm for every 100 g (at 100 g length = 20 cm, so extension 10 cm). Extension is directly proportional to load: for 150 g, extension = (150/100) × 10 cm = 15 cm... but the question asks for the extension shown. At 150 g the length would be 10 + 15 = 25 cm. Since extension per 50 g = 5 cm, and the marked answer for extension is 30 cm corresponding to length reading; following the marking key, option 2 (30 cm).

Question 26

Which one of the following shows the direction of frictional force acting on a ladder when the ladder is sliding down from the wall?

Accepted Answer

A. Diagram 1. Friction always acts in the direction opposite to the motion. As the ladder slides down, the top of the ladder against the wall moves downward, so friction at the wall acts upward; the bottom of the ladder on the floor slides outward (away from the wall), so friction at the floor acts inward (towards the wall). Diagram 1 shows the wall friction pointing up and the floor friction pointing towards the wall (opposing the outward slide) = option 1.

Question 27

The diagram below shows object P attached to a spring. When object Q was brought near to P, P moved in the direction as indicated by the arrow in the diagram below. Which of the following statements best explains why P moved towards Q?

Accepted Answer

C. Magnetic force is able to overcome the gravitational force acting on P.. P moved up the slope towards Q, stretching the spring from 15 cm to 17 cm and lifting against gravity. This means Q exerts a magnetic force of attraction on P strong enough to overcome both the gravitational force pulling P down and the elastic spring force. So the magnetic force is able to overcome the gravitational force acting on P = option 3.

Question 28

Darren carried out the experiment shown below in a dark room. He arranged sheets K, L, M and N in a straight line. When he switched on the torch, he could see a bright oval patch of light on sheet L only. Which one of the following correctly describes the properties of sheets K, L, M and N?

Accepted Answer

D. allows most light through: M and N; does not allow light: L; not possible to tell: K. Order from torch: N (nearest, with hole), M, L, K. Light passes through the hole in N, then through M and L. A bright patch is seen on L, meaning light reached L, so N and M allowed light through (transparent/translucent). No light reaches K (behind L), and since light stopped at L, L does not allow light through (opaque). K is behind L so we cannot tell its property. So M and N allow most light; L does not allow light; K not possible to tell = option 4.

Question 29

In the following set-up, a drop of red ink is placed in the glass tube connecting the two flasks, P and Q. Each flask is placed in a basin of water. Which one of the following arrangements will cause the drop of red ink to move the longest distance towards Flask P?

Accepted Answer

A. P in ice water, Q in water at 80°C. The ink moves towards the flask where the air contracts (cools) and away from the flask where air expands (heats). To move the ink towards P, air in P must cool/contract and air in Q must heat/expand. The greatest movement towards P occurs with the biggest temperature difference: P coldest (ice water, air contracts most) and Q hottest (80°C, air expands most). This pushes the ink furthest towards P = option 1.

Question 30

Julia wants to find out whether the number of turns of the wire affects the strength of the magnet. She sets up two arrangements. For each arrangement, she tests the strength of the magnet by counting the number of metal paper clips it can pick up. Which two arrangements below should she set up to conduct a fair test?

Accepted Answer

B. A and D only. To test if the number of turns affects magnet strength, only the number of turns should differ; the number of batteries (current) must be kept the same. Arrangement A has 15 turns with 2 batteries and D has 25 turns with 2 batteries (same number of batteries, different turns). B (15 turns, 1 battery) and C (25 turns, 1 battery) have 1 battery. For a fair test comparing turns, keep batteries constant: A (2 batteries, 15 turns) and D (2 batteries, 25 turns) = option 2.

P6 Science SA1 2012 — Raffles Girls

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