Q: Containers, A, B and C, were set up with the same amount of carbon dioxide at the start of an experiment. For 12 hours, containers A and B were kept in the presence of light while container C was kept in darkness. Which one of the following has correctly arranged the one containing the least amount of carbon dioxide in the water to the one with the most carbon dioxide at the end of the experiment? (Least carbon dioxide → most carbon dioxide)

(2) B, C, A. Container B has a water plant in light: it photosynthesises and uses up carbon dioxide, so it has the least. Container A has snails in light: the snails respire and release carbon dioxide, increasing it. Container C has a snail in darkness: it respires and releases carbon dioxide (and no plant uses it), giving the most. Order least→most: B, A, C.

Q: Daphne wanted to find out whether water plants affect the amount of carbon dioxide in water when exposed to different amounts of light. She prepared two set-ups similar to the one shown (a jar with a water plant in water with liquid X). One set-up was placed in a dark cupboard while the other was placed under a lamp. She then added a few drops of liquid X to the water in the two set-ups. At the start of the experiment, the colour of the water with liquid X was red. Liquid X will change colour based on the amount of carbon dioxide present (less carbon dioxide than at the start → blue; more carbon dioxide than at the start → yellow). What colour would the water with liquid X be in each set-up after 2 days?

(2) Under a lamp: blue, In a dark cupboard: yellow. Under the lamp the plant photosynthesises and uses up carbon dioxide, so there is less CO₂ than at the start → blue. In the dark cupboard the plant cannot photosynthesise but still respires, releasing carbon dioxide, so there is more CO₂ than at the start → yellow. So under a lamp = blue, dark cupboard = yellow.

Question 1

The diagram below shows parts of the human digestive system. In which of the following parts is digestion carried out?

Accepted Answer

(3) A, C and D only. Digestion takes place in the mouth (A), the stomach (C) and the small intestine (D). B is the oesophagus (transport only) and E is the large intestine (water absorption only), so digestion occurs in A, C and D.

Question 2

In the diagram below, A, B, C and D represent the parts of a plant. The arrows represent the movement of substances in the plant. Which one of the following correctly identifies parts A, B, C and D?

Accepted Answer

(2) A: leaf, B: roots, C: roots, D: leaf. Solid arrows show movement of food (made in the leaves and transported away); dashed arrows show movement of water and mineral salts (absorbed by roots and carried up). The two top corners A and D where food originates/water arrives are leaves, the bottom corners B and C are roots. So A=leaf, B=roots, C=roots, D=leaf.

Question 3

A glass tank was placed over a container of ice cubes. This was placed on a table in the kitchen with a room temperature of 30°C. The ice cubes started to melt after some time and it was observed that the air inside the glass tank was cooler than the room temperature. Which of following correctly explain why the temperature of the air in the glass tank was lower after some time?
A  The air inside the tank lost heat to the water.
B  The air inside the tank gained heat from the water.
C  The air inside the tank lost heat to the melting ice cubes.
D  The air inside the tank gained heat from the melting ice cubes.

Accepted Answer

(1) A and C only. The air inside the tank is warmer than both the cold water and the melting ice cubes, so heat flows from the warmer air to the cooler water and cooler ice cubes. Thus the air loses heat to the water (A) and to the melting ice cubes (C), cooling the air.

Question 4

An experiment was conducted to study the effect of temperature on the rate of evaporation of water. The conditions were recorded in the table below. Which of the two set-ups should they use to ensure a fair test?

Accepted Answer

(3) B and C. To study the effect of temperature, only the temperature should differ while exposed surface area and amount of water are kept the same. Set-up B (50 cm², 60°C, 200 ml) and set-up C (50 cm², 80°C, 200 ml) have the same surface area (50) and same amount of water (200) but different temperatures, making it a fair test.

Question 5

Hassan was given a set of drawings which showed 3 glasses of water at different temperatures, 4°C, 32°C and 90°C. The glasses were placed on a table in a room of 32°C. He was told to draw the most likely formation of water droplets on each of the glasses after some time. His drawings are shown below. Which of the above drawings are correct?

Accepted Answer

(2) A and C only. Water droplets form on the outside of a glass when its surface is cooler than the surrounding air, causing water vapour in the air to condense. Glass A (4°C) is cooler than the 32°C room, so droplets form (correct). Glass B (32°C) is the same as the room, so no droplets should form (B is drawn with droplets, so incorrect). Glass C (90°C) is hotter than the room, so no condensation; droplets would not form on the outside (C is correct in showing none/being warmer). Hence A and C are correct.

Question 6

Which of the following are actions that help to conserve water?
A  Take long showers on a hot day.
B  Turn off the running tap while brushing your teeth.
C  Reuse water used for washing rice to water plants.
D  Use the washing machine only when you have a half load.

Accepted Answer

(2) B and C only. Turning off the tap while brushing (B) and reusing rice-washing water for plants (C) both save water. Long showers (A) waste water, and using the washing machine on half load (D) wastes water (it should only be used with a full load). So only B and C conserve water.

Question 7

Study the diagram of the water cycle below. X and Y are two processes that take place in the water cycle. Based on the diagram above, which of the following statement(s) is/are incorrect?
A  Heat is gained by water vapour during process Y.
B  Process X does not take place at a fixed temperature.
C  There is a change in state of water during processes X and Y.

Accepted Answer

(1) A only. X is evaporation (sea → water vapour) and Y is condensation (water vapour → clouds). During condensation (Y) heat is LOST by water vapour, not gained, so statement A is incorrect. Statement B is correct (evaporation occurs over a range of temperatures, not a fixed one) and statement C is correct (both involve a change of state). Thus only A is incorrect.

Question 8

Jessica had three tubes, X, Y and Z, containing an equal amount of water plants mixed in the same amount of yellow liquid P. This yellow liquid turns green after photosynthesis has taken place. Jessica placed tube X at a distance of 10 cm from the lamp. She switched on the lamp in a dark room and recorded the time taken for the mixture to turn green. She repeated the experiment with tubes Y and Z at various distances from the lamp and recorded the results in the table below (X: 17 min, Y: 9 min, Z: 28 min). Which one of the graphs below correctly represents the distance that tubes X, Y and Z are placed from the lamp?

Accepted Answer

(2) Bar graph: X medium, Y short, Z tallest. The nearer the tube to the lamp, the more light it receives and the faster photosynthesis occurs (shorter time to turn green). Times: Y=9 (fastest → nearest, shortest distance), X=17 (medium), Z=28 (slowest → furthest, greatest distance). So distance order Y < X < Z. The correct bar graph shows Y shortest, X medium and Z tallest (option 2).

Question 9

Containers, A, B and C, were set up with the same amount of carbon dioxide at the start of an experiment. For 12 hours, containers A and B were kept in the presence of light while container C was kept in darkness. Which one of the following has correctly arranged the one containing the least amount of carbon dioxide in the water to the one with the most carbon dioxide at the end of the experiment? (Least carbon dioxide → most carbon dioxide)

Accepted Answer

(2) B, C, A. Container B has a water plant in light: it photosynthesises and uses up carbon dioxide, so it has the least. Container A has snails in light: the snails respire and release carbon dioxide, increasing it. Container C has a snail in darkness: it respires and releases carbon dioxide (and no plant uses it), giving the most. Order least→most: B, A, C.

Question 10

Daphne wanted to find out whether water plants affect the amount of carbon dioxide in water when exposed to different amounts of light. She prepared two set-ups similar to the one shown (a jar with a water plant in water with liquid X). One set-up was placed in a dark cupboard while the other was placed under a lamp. She then added a few drops of liquid X to the water in the two set-ups. At the start of the experiment, the colour of the water with liquid X was red. Liquid X will change colour based on the amount of carbon dioxide present (less carbon dioxide than at the start → blue; more carbon dioxide than at the start → yellow). What colour would the water with liquid X be in each set-up after 2 days?

Accepted Answer

(2) Under a lamp: blue, In a dark cupboard: yellow. Under the lamp the plant photosynthesises and uses up carbon dioxide, so there is less CO₂ than at the start → blue. In the dark cupboard the plant cannot photosynthesise but still respires, releasing carbon dioxide, so there is more CO₂ than at the start → yellow. So under a lamp = blue, dark cupboard = yellow.

Question 11

The diagram below represents a life process that takes place in green plants. Which one of the following correctly identifies S, T, U, V and W?

Accepted Answer

(3) S: carbon dioxide, T: sugar, U: oxygen, V: water, W: light. The life process is photosynthesis. It needs light energy (W = light), takes in carbon dioxide and water from the environment (S = carbon dioxide, V = water), makes sugar/food in the plant (T = sugar) and releases oxygen to the environment (U = oxygen). This matches option 3.

Question 12

Lynn set up an experiment to find out whether carbon dioxide is needed for photosynthesis. She used a plant which had leaves with green areas in the middle and white areas round the edges as shown below. The white areas of the leaves do not contain chloroplasts. One of the leaves was wrapped in a plastic bag containing substance X which absorbs carbon dioxide. The set-up was placed in sunlight. Which of the following two areas should Lynn compare to show that carbon dioxide is needed for photosynthesis?

Accepted Answer

(4) S and R. To show carbon dioxide is needed, compare two green areas (which both contain chloroplasts) that differ only in carbon dioxide availability. S is a green area inside the bag with substance X (no carbon dioxide) and R is a green area outside the bag (carbon dioxide present). Both are green, so the only difference is CO₂. Comparing S and R isolates the effect of carbon dioxide.

Question 13

Jemay clamped a magnet 10 cm away from the base of a retort stand where she laid 10 staples as shown in the diagram below. The magnet attracted some of the staples and she counted the number of staples left on the base of the retort stand. She repeated the experiment, decreasing distance d by 2 cm until all the staples were attracted. She recorded her results in a table (d=10→2 staples, d=8→3, d=6→5, d=4→8, d=2→10). Which one of the following is a correct conclusion based on Jemay's experimental results?

Accepted Answer

(3) The smaller the distance d, the greater the magnetic force exerted on the staples.. As distance d decreases (10→2 cm), the number of staples attracted increases (2→10), showing the magnetic force is stronger when the magnet is closer. So the smaller the distance d, the greater the magnetic force on the staples (option 3). The results say nothing about poles (1), do not support all 10 at 3 cm (2), and option 4 is the opposite of the trend.

Question 14

A cardboard box was set up with a lighted lamp as shown below. An opening was cut in the box such that a wooden disc could be fitted exactly. The disc had three holes which were pasted with three different types of materials (A circle, B square, C diamond). The shadows cast on the screen appeared as shown below (a dark square with a light rectangle and a light diamond, no circle shadow opening). Based on the results given, which one of the following correctly describes the properties of materials A, B and C?

Accepted Answer

(2) Allows most light: C, Allows some light: B, Allows no light: A. On the screen the circle (material A) leaves a dark patch → A allows no light (opaque). The square (material B) shows a faint/partial bright patch → B allows some light (translucent). The diamond (material C) shows the brightest/clearest patch → C allows most light (transparent). So most=C, some=B, none=A (option 2).

Question 15

Tom pasted a film on a glass window to reduce the amount of sunlight coming into the classroom. He noticed that some air bubbles were trapped under the film as shown in Diagram 1. After two weeks, the air bubble became larger as shown in Diagram 2. Which of the following reasons best explains why the gap with air became larger in Diagram 2?

Accepted Answer

(3) The air in the gap gained heat and expanded.. Sunlight warms the trapped air. When air gains heat it expands, so the bubble (gap filled with air) became larger after two weeks. Option 3 correctly states the air gained heat and expanded.

Question 16

Geetha stood on a weighing scale and her classmates made some statements based on their observation. Which one of the statements made by her classmates are correct?
A  Geetha's weight is a force.
B  Geetha's weight will increase as her mass increases.
C  Geetha will weigh less on the moon as there is less gravitational force acting on her there.

Accepted Answer

(4) A, B and C. Weight is the gravitational force acting on an object, so A is correct. Weight depends on mass, so as mass increases weight increases (B correct). The moon has weaker gravity than Earth, so an object weighs less there (C correct). All three statements are correct.

Question 17

Junhao hooked a rubber band to a toy glider. He then stretched the rubber band as shown in the diagram below before releasing the glider held in his hand. Which of the following correctly describe the forces acting on the glider just before it is released?
A  Gravitational force is acting on the toy glider.
B  There is frictional force between the fingers and the toy glider.
C  The stretched rubber band exerts an elastic spring force on the toy glider.

Accepted Answer

(4) A, B and C. Just before release: gravitational force always acts on the glider (A correct); the fingers hold the glider, so frictional force acts between fingers and glider (B correct); the stretched rubber band exerts an elastic spring force pulling the glider (C correct). All three forces act, so A, B and C.

Question 18

Rosnah carried out an experiment as shown in the diagram below. She pulled a wooden block on its larger rectangular surface on a table. She used a spring balance to measure the force needed when the block started to move at a steady speed. Then she repeated the experiment, placing the same wooden block on its smaller square surface and measuring the force needed to move the block. Based on the above information, what is the aim of her experiment?

Accepted Answer

(3) To find out if the surface area of the block in contact with the table affects the force needed to move it.. The only variable changed is the surface area in contact with the table (larger rectangular surface vs smaller square surface), while the same block (same mass and material) is used and the force needed is measured. So the aim is to find out if the surface area in contact affects the force needed to move it (option 3).

Question 19

Anders wanted to find out if the arrangement of bulbs will affect the brightness of the bulbs. He set up four circuits (P, Q, R and S) as shown below. Which two circuits should he use to conduct a fair test?

Accepted Answer

(2) P and S. To test if the arrangement (series vs parallel) of bulbs affects brightness fairly, only the arrangement should differ while the number of bulbs and number of batteries are kept the same. Circuits P and S use the same number of bulbs and the same number of batteries but differ in arrangement, making it a fair test.

Question 20

Gerald carried out an experiment to find out if liquids X, Y and Z are conductors of electricity. He inserted 2 metal plates of similar size connected to an electric circuit in Liquid X as shown in the set-up below. He closed the switch and observed the bulb. He repeated this with the other 2 liquids, Y and Z, and recorded the results in a table (X: did not light up, Y: lit up brightly, Z: lit up dimly). Which variables should he keep the same to ensure that he is conducting a fair test?
A  type of liquid
B  amount of liquid
C  type of metal plate
D  number of batteries

Accepted Answer

(3) B, C and D only. The variable being tested is the type of liquid, so that must be CHANGED, not kept the same (so A is excluded). To be fair, keep constant the amount of liquid (B), the type of metal plate (C) and the number of batteries (D). So the answer is B, C and D.

Question 21

Jieqi set up 3 electrical circuits with two bulbs each. Bulbs P, Q and R are labelled as shown below. All the electrical components are new and working properly. Based on the set-ups, which of the following statement(s) is/are correct?
A  Bulb R lights up the brightest.
B  Bulb Q lights up brighter than Bulb P.
C  Bulbs P and Q have the same brightness.

Accepted Answer

(2) B only. Set-up 2 (bulb Q) has more batteries than Set-up 1 (bulb P), so Q lights up brighter than P (B correct). Set-up 3 (bulb R) has only one battery, so R is dimmer, making A (R brightest) wrong and C (P and Q same brightness) wrong. Only statement B is correct.

Question 22

In the electrical circuit below, only 3 bulbs lit up when all the switches were closed. P, Q, R and S are blocks of different materials. Based on the results, which of the following are possible materials that P, Q, R and S could be made of?

Accepted Answer

(4) P: copper, Q: glass, R: wood, S: aluminium. For exactly 3 bulbs to light, the blocks in the branches carrying those bulbs must conduct while the block(s) in the branch with the unlit bulb must not. The arrangement that allows current through the conducting branches (P, S as conductors) and blocks the branch with the non-conducting blocks (Q, R as insulators) gives 3 lit bulbs. Option 4 (P=copper, Q=glass, R=wood, S=aluminium) makes P and S conductors and Q and R insulators, producing exactly 3 lit bulbs.

Question 23

Keith constructed a circuit puzzle using 2 batteries, 4 bulbs, A, B, C and D and some wire. All the electrical components were in working condition. He covered the circuit with a piece of cardboard with only the bulbs exposed as shown below. Keith removed bulbs A, B, C and D one at a time leaving a gap in the circuit. He observed the effect before re-connecting each bulb and recorded them in the table (Remove A → B and D lit; Remove B → A, C and D lit; Remove C → B and D lit; Remove D → none lit). Based on the above information, which one of the following shows the circuit diagram that Keith had constructed?

Accepted Answer

(4) Circuit diagram 4. When D is removed all bulbs go out, so D is in series with the battery (on the main line). When A is removed, B and D stay lit (C goes out) and when C is removed, B and D stay lit (A goes out) — this shows A and C are on separate parallel branches such that removing one cuts only the bulb in series with it, while B remains in a branch on its own. The circuit in option 4 matches: D in the main series line, B in one parallel branch, and A in series with C in another parallel branch.

Question 24

Ashlyn held a toy between her hands as shown below. She rotated the toy by sliding her right hand forward and her left hand backwards before releasing it. The toy flew to a certain height after it left her hands. She rotated the same toy from the same starting position again. However, the toy flew to a higher height than it did before. Which one of the following could explain why the toy flew to a greater height?

Accepted Answer

(3) The toy had a greater kinetic energy.. Spinning the toy faster gives it more kinetic energy, which is converted into more gravitational potential energy, allowing it to fly higher. So a greater kinetic energy (option 3) explains the higher flight.

Question 25

Dave conducted an experiment with four set-ups A, B, C and D. He used two metal blocks of the same size but of different masses. He released the blocks from different heights as shown below (A: 250 g from 1 m; B: 450 g from 1 m; C: 250 g from 0.5 m; D: 450 g from 0.5 m). Dave wanted to find out how the distance travelled by the block is affected by its mass and the height from which it was released. Which pairs of set-ups should he use in his investigation?

Accepted Answer

(3) Mass: C and D; Height: B and D. To test the effect of mass, keep height the same and change mass: C (250 g, 0.5 m) and D (450 g, 0.5 m). To test the effect of height, keep mass the same and change height: B (450 g, 1 m) and D (450 g, 0.5 m). So mass = C and D; height = B and D (option 3).

Question 26

The diagram below shows a man sitting in a capsule of a ferris wheel. Which one of the following graphs shows the change in the amount of gravitational potential energy of the capsule as the man travelled from position A to position D?

Accepted Answer

(4) Graph rising to a peak at B then falling steadily to a low at D. Following the wheel's movement from A (side, mid-height) up to B (top, highest), then down past C (other side, mid-height) to D (bottom, lowest), the height increases from A to B then decreases continuously to D. Gravitational potential energy rises to a peak at B then falls steadily to a minimum at D, which matches graph 4.

Question 27

The diagram below shows that electrical energy can be converted to other useful forms of energy in the 6 electrical appliances (radio → sound; lamp → light; washing machine → A; fan → B; toaster → C; television → D). Which useful forms of energy are necessary for the appliances to function as represented by A, B, C and D?

Accepted Answer

(2) A: Kinetic Energy, B: Kinetic Energy, C: Heat Energy, D: Light and Sound Energy. Washing machine (A) converts electrical energy to kinetic energy (drum turning); fan (B) to kinetic energy (blades spinning); toaster (C) to heat energy; television (D) to light and sound energy. This matches option 2.

Question 28

Four pupils released a ball at Point W as shown in the diagram below. It rolled down the slope, moved along the floor and stopped at Point Z. The pupils then made the following statements.
David: At points X and Y, the ball only has kinetic energy.
Ravi: The ball has the greatest amount of gravitational potential energy at point W.
Sue: The ball would have rolled further if the experiment had been done on a glass floor.
Kim: The ball would have rolled faster along the slope if angle a had been larger.
Which of the pupils had made a correct statement?

Accepted Answer

(3) Kim, Ravi and Sue only. David is wrong: at X and Y the ball is partway down the slope, so it has BOTH kinetic and gravitational potential energy, not only kinetic. Ravi is correct: at the highest point W the ball has the greatest gravitational potential energy. Sue is correct: a smoother glass floor has less friction, so the ball rolls further. Kim is correct: a steeper slope (larger angle a) makes the ball roll faster. So Kim, Ravi and Sue are correct.

P6 Science CA1 2017 — Nanyang

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P6 Science CA1 2017 — Nanyang

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