Question 1

Which of the following are parts of the digestive system?
A  heart
B  gullet
C  windpipe
D  small intestine

Accepted Answer

B. B and D only. The gullet (oesophagus) and small intestine are parts of the digestive system. The heart belongs to the circulatory system and the windpipe to the respiratory system, so only B and D are correct.

Question 2

Matthew has four containers, A, B, C and D, made of the same material. He filled each container with the same amount of water as shown in the diagram below. The four containers were placed under the sun for an hour. The amount of water left in each container was then measured. Arrange the containers in order, starting from the container with the most amount of water left to the container with the least amount of water left.

Accepted Answer

A. Most → Least: C, A, B, D. Evaporation is faster when the water has a larger exposed surface area. Container C is the tallest and narrowest (smallest surface area) so it loses the least water, while container D is the widest (largest surface area) so it loses the most. Order from most water left to least is C, A, B, D.

Question 3

Devi left a beaker of ice on the table until all the ice had melted and reached room temperature. Which one of the following graphs shows the result that Devi would observe?

Accepted Answer

B. Temperature rises from a low value, levels off at 28°C and stays constant. Ice starts below room temperature. As it gains heat from the surroundings it warms up, the ice melts, and the temperature rises until it reaches room temperature (28°C), where it levels off and stays constant. It cannot rise above room temperature, ruling out 100°C, and it does not fall.

Question 4

Which of the following help to conserve water?
A  Using rainwater to water plants.
B  Using a solar heater to heat up the water.
C  Washing the car using pails instead of a hose.
D  Using water from the washing machine to mop the floor.

Accepted Answer

D. A, C, and D only. Using rainwater (A), washing with pails instead of a hose (C) and reusing washing-machine water to mop (D) all reduce the amount of fresh water used. Using a solar heater (B) only changes how water is heated; it does not save water. So A, C and D conserve water.

Question 5

John placed some ice cubes in an empty paper cup and left them in the classroom as shown in the diagram below. Which of John's actions will enable the ice in the paper cup to melt faster?
A  Blowing into the cup.
B  Replacing the paper cup with a metal cup.
C  Wrapping his hands around the paper cup.
D  Placing a lid to cover the opening of the paper cup.

Accepted Answer

C. A, B and C only. Ice melts faster when it gains heat more quickly. Blowing warm breath in (A), replacing the paper cup with a better heat-conducting metal cup (B), and wrapping warm hands around the cup (C) all transfer more heat to the ice. Covering the opening with a lid (D) does not speed melting. So A, B and C are correct.

Question 6

The diagram below shows a complete water cycle. How many time(s) does water undergo a change of state in one complete cycle?

Accepted Answer

B. 2. In one complete cycle, water evaporates from the river (liquid to gas) = one change of state, then condenses to form clouds (gas to liquid) = second change of state, then falls as rain (still liquid). Water changes state twice.

Question 7

Liwen placed a potted plant in a dark room for two days before wrapping 3 similar leaves in different types of plastic bags of the same size. She left the plant under bright light for some time. Then she plucked the leaves and removed the colour of the leaves by boiling and soaking them in alcohol. Which of the following leaf/leaves would cause iodine solution to turn from yellowish brown to dark blue?

Accepted Answer

C. leaves A and B only. Iodine turns dark blue in the presence of starch, which is made during photosynthesis. Photosynthesis needs light and carbon dioxide. Leaf A (clear bag, sealed) gets light but limited carbon dioxide, leaf B (clear bag with holes) gets both light and carbon dioxide, and leaf C (black bag) gets no light. Both leaves A and B receive light and can make starch, so leaves A and B turn iodine dark blue.

Question 8

Tim set up an experiment in a dark room as shown in the diagram below. A light source was placed 80cm away from the beaker. After a while, he counted and recorded the number of bubbles produced by the plant in one minute. He repeated the experiment by decreasing the distance between the light source and the beaker and counted the number of bubbles produced again. Which one of the following is most likely the aim of Tim's experiment?

Accepted Answer

C. To find out how the intensity of light affects the rate of photosynthesis.. Tim changes only the distance between the light source and the plant, which changes the brightness (intensity) of light reaching the plant. The number of bubbles measures the rate of photosynthesis. So the experiment investigates how light intensity affects the rate of photosynthesis.

Question 9

Which one of the following statements about photosynthesis is wrong?

Accepted Answer

D. Water needed for photosynthesis is taken in through the leaves.. Water for photosynthesis is absorbed by the roots and transported up to the leaves, not taken in through the leaves. Statements A, B and C are correct, so the wrong statement is D.

Question 10

Michael de-starched a plant before covering different parts of a leaf, A, B, C and D, with different materials as shown in the diagram below. The plant was left under the sun for two days before Michael tested the leaf for the presence of starch using iodine solution. Michael wanted to find out if light is needed for photosynthesis. Which parts of the leaf should he compare for his experiment?

Accepted Answer

D. B and D only. To test if light is needed, only the amount of light should differ while all else stays the same. Part B is uncovered (gets full light) and part D is covered with aluminium foil (blocks all light); both are otherwise the same leaf. Comparing B (light) with D (no light) isolates light as the only variable.

Question 11

Martin conducted an experiment using two identical plants, A and B. He removed only the food-carrying tubes from the stem of plant B at part W. He left the plants under the sun and watered them regularly. After two weeks, he observed that both plants were still alive and growing well. Which of the following statements about the plants are correct?
A  Water cannot reach the fruits of plant B.
B  The part of the stem above W will become swollen.
C  After a few months, plant A will grow better than plant B.

Accepted Answer

C. B and C only. Only the food-carrying tubes (phloem) were removed; the water-carrying tubes (xylem) remain, so water can still reach the fruits, making A wrong. Food made in the leaves cannot pass down the cut at W, so it accumulates and the stem above W swells (B correct). With food blocked from reaching the roots, plant B will eventually grow less well than plant A (C correct). So B and C are correct.

Question 12

Justin left four identical plants, A, B, C and D, in a dark cupboard for two days before the start of an experiment. He wrapped the plants in different types of plastic bags which were of the same size. Then he placed the plants under bright light for three days and watered them daily. After three days, a leaf from each of the plants was removed and tested for the presence of starch. Which of the following correctly shows if starch is present in the leaf?

Accepted Answer

C. Plant A present, Plant B absent, Plant C absent, Plant D present. Starch forms only when a plant can photosynthesise, which needs light AND carbon dioxide. Plant A (clear bag) has both light and carbon dioxide → starch present. Plant B (black bag) has no light → absent. Plant C (clear bag with a substance absorbing carbon dioxide) lacks carbon dioxide → absent. Plant D (clear bag with a substance absorbing water; still has light and carbon dioxide) → starch present. So A present, B absent, C absent, D present.

Question 13

Junda stroked two steel rods, X and Y, to magnetise them as shown in the diagram below. He stroked the rods an equal number of times using the same bar magnet. He brought one end of rod X near to a steel bar as shown below. He repeated this using rod Y. Which one of the following will Junda observe?

Accepted Answer

C. Rod X: no attraction or repulsion, Rod Y: attraction. Rod X was stroked back and forth in both directions (double arrow), so the strokes cancel and it does not become a magnet — it shows no attraction or repulsion. Rod Y was stroked repeatedly in one direction, so it becomes a magnet. A magnetised rod brought near an unmagnetised steel bar attracts it. So rod X shows no attraction or repulsion and rod Y shows attraction.

Question 14

Bala used the set-up below to test how much light could pass through 3 different objects, X, Y and Z. The experiment was repeated by replacing object X with object Y, and then object Z. The results of the experiment are as shown below: Object X = 0 lux, Object Y = 57 lux, Object Z = 98 lux, none = 100 lux. Which of the following correctly matches the properties of the objects?

Accepted Answer

D. Allows most light: Z; some light: Y; does not allow light: X. More light detected means more light passes through. Z lets through 98 lux (most, nearly transparent), Y lets through 57 lux (some, translucent), and X lets through 0 lux (none, opaque). So Z = allows most light, Y = allows some light, X = does not allow light.

Question 15

Nicholas boiled some water in a beaker for 10 minutes before removing the heat source. He then added ice into the beaker. The graph below shows how the temperature of water changed over time. At which point of the graph was the ice added into the beaker?

Accepted Answer

C. B. The water boils and stays at 100°C until 10 minutes (point A). After the heat is removed, adding ice causes the temperature to start falling. The temperature begins dropping at point B, so the ice was added at point B.

Question 16

Terence conducted an experiment using two springs, A and B. He hung different masses on them and recorded the length of the springs. His results are shown in the graph below. Based on the graph, which of the following statements are true?
A  Spring A stretched more than Spring B for the same load.
B  Spring A extended by 20cm when a mass of 80g was hung.
C  Spring B was longer than Spring A before the start of the experiment.

Accepted Answer

B. A and C only. From the graph, Spring A (dotted) rises more steeply, so it stretches more than Spring B for the same load (A correct). At 0g, Spring B starts at about 5cm and Spring A starts lower (about 2-3cm), so Spring B was longer before the experiment (C correct). For B: Spring A starts near 2-3cm and reaches about 20cm at 80g, an extension of about 17cm, not 20cm, so statement B is wrong. So only A and C are true.

Question 17

For questions 17 & 18, refer to the diagram. Phillip threw a ball into the net and the path that the ball travelled through was shown by the positions P, Q, R and S. Which of the following statement(s) is/are correct?
A  There is no force acting on the ball at S.
B  There is more than one force acting on the ball at P.
C  The effect of the forces at R causes the ball to change direction.

Accepted Answer

D. B and C only. At S the ball is still moving and gravity still acts on it, so A is wrong. At P, the player's push and gravity both act, so more than one force acts (B correct). At R, gravity changes the ball's direction as it curves downward (C correct). So B and C are correct.

Question 18

Which one of the following graphs shows the amount of gravitational force acting on the ball at positions P, Q, R and S?

Accepted Answer

D. Horizontal straight line (constant) across P, Q, R, S. Gravitational force on the ball depends on its mass, which does not change as it moves. So the gravitational force stays the same at all positions P, Q, R and S, shown by a horizontal (constant) line.

Question 19

Sharon made a circuit card with six fasteners, A, B, C, D, E and F, which are connected by wires on the underside. She connected the circuit tester to two of the fasteners at a time and obtained the following results: AB = No, BC = Yes, CD = Yes, DE = No, EF = No, AF = No, BF = Yes. Based on her results, which one of the following connections is correct?

Accepted Answer

D. Connection diagram 4. The bulb lights only when two fasteners are joined by a wire. The 'Yes' results are BC, CD and BF, meaning B, C, D and F are all electrically connected together. Option 4 shows wires linking B, C, D and F (and D-F via the connections) so that exactly those pairs conduct, matching all the results.

Question 20

Hilda set up an electrical circuit with three new batteries, three working bulbs and two switches as shown in the diagram below. Which of the following is/are correctly observed when Hilda controlled the switches, S1 and S2 as shown below?
A  S1 open, S2 open → B1 lit, B2 unlit, B3 unlit
B  S1 close, S2 open → B1 unlit, B2 lit, B3 unlit
C  S1 open, S2 close → B1 lit, B2 unlit, B3 lit
D  S1 close, S2 close → B1 lit, B2 unlit, B3 lit

Accepted Answer

A. B only. Tracing the circuit: B1 is in series with branch S1, and B2 is in the middle branch, while B3 is in series with S2. Working through each switch combination, only row B (S1 close, S2 open giving B1 unlit, B2 lit, B3 unlit) is consistent with the circuit, so B only is correctly observed.

Question 21

Dekai had four rods of different materials, W, X, Y and Z. He connected them in a circuit and recorded his observations as shown in the diagram below. He then rearranged the positions of the 4 rods and recorded his observations again. Based on his results, which one of the following shows the possible materials that rods W, X, Y and Z could be made of?

Accepted Answer

C. W silver, X aluminium, Y copper, Z wood. A bulb lights only when its loop contains all conductors. From the two set-ups, the rods that lie in the 'lit up' loops must be conductors and those in the 'did not light up' loops include a non-conductor. Working out which rods are always in a conducting path versus an open path, W, X and Y must be conductors (silver, aluminium, copper) and Z must be a non-conductor (wood). Option 3 fits.

Question 22

Which one of the following advice for handling electrical appliances is incorrect?

Accepted Answer

B. Electrical appliances with exposed wires should be used.. Using electrical appliances with exposed wires is dangerous because it can cause electric shocks or fire, so it should NOT be done. Statements A, C and D are correct safety advice, making B the incorrect statement.

Question 23

A pendulum was released from a starting point A and moved to point D as shown in the diagram below. At which point did the pendulum possess the most potential energy?

Accepted Answer

A. A. Gravitational potential energy is greatest at the highest point. The pendulum is released from A, the highest position of its swing, so it possesses the most potential energy at A.

Question 24

Which one of the following correctly shows the energy conversion correctly when a candle is lit?

Accepted Answer

B. potential energy → light energy + heat energy. A lit candle converts the chemical (potential) energy stored in the wax into light energy and heat energy. Option 2 correctly shows potential energy → light energy + heat energy.

Question 25

Which one of the following groups consists only of renewable sources of energy?

Accepted Answer

B. sun, running water, wind. Renewable sources can be replenished naturally. The sun, running water and wind are all renewable. Coal, crude oil and natural gas are non-renewable fossil fuels. So only option 2 (sun, running water, wind) consists entirely of renewable sources.

Question 26

Chengan hung three balls of the same size but different masses as shown in the diagram below. The balls and strings were not moving. After the strings were cut, the balls dropped and made dents in the tray of sand. (The diagram below is not drawn to scale). Based on the information above, which of the following statements are correct?
A  Ball X will create a dent of the same depth as Ball Y.
B  Ball Y has more gravitational potential energy than ball X.
C  Ball W will create a deeper dent in the sand pit than ball Y.
D  All the balls have the same amount of kinetic energy before the strings were cut.

Accepted Answer

C. B, C and D only. Ball W (700g) hangs 5cm from the bar so it is highest (95cm above sand). Balls X (300g) and Y (700g) hang 11cm from the bar (89cm above sand). Statement A is wrong: X is lighter than Y, so X makes a shallower dent. B is correct: Y (700g) is higher mass than X (300g) at the same height, so more GPE. C is correct: W is heavier and falls from a greater height than Y, so it dents deeper. D is correct: before cutting, all balls are stationary so all have zero (the same) kinetic energy. So B, C and D are correct.

Question 27

In the toy shown below, a ball was held at point A and then released. Which one of the following shows the changes in the energy of the ball when it travelled from point A to point C?

Accepted Answer

B. PE: A→B decrease, B→C increase; KE: A→B increase, B→C decrease. On a U-shaped track, the ball goes down from A to B (lowest point) then up from B to C. From A to B it loses height so potential energy decreases and kinetic energy increases. From B to C it gains height so potential energy increases and kinetic energy decreases. Option 2 matches.

Question 28

Sam attached 3 identical springs, X, Y and Z, at different points on a wall. He then hung objects A, B and C of different masses to the springs as shown below. Which of the following statements about the set-up is correct?

Accepted Answer

B. Spring Y has the most amount of elastic potential energy.. The more a spring stretches, the heavier the object and the more elastic potential energy it stores. Spring Y is stretched the most (object B hangs lowest with the longest spring), so spring Y has the most elastic potential energy. Option 2 is correct.

P6 Science CA1 2018 — Nanyang

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P6 Science CA1 2018 — Nanyang

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