Question 1

Study the life cycles of some animals as shown below.

Which of the following statements are true of the above life cycles of animals?
A: All the adults have wings.
B: Adult 1 could be a dragonfly.
C: All the animals develop from eggs.
D: Both Adult 3 and Adult 4 could be moths.

Accepted Answer

C. B, C and D only. Adult 1 (Egg→Nymph→Adult) is incomplete metamorphosis, so it could be a dragonfly (B true). All four life cycles begin with eggs (C true). Adult 3 (Egg→Caterpillar/Larva→Pupa→Adult) and Adult 4 (Egg→Larva→Pupa→Adult) both undergo complete metamorphosis and could be moths (D true). Statement A is false because Adult 2 is a frog, which has no wings.

Question 2

The following flowchart shows the characteristics of four different organisms, P, Q, R and S.

Which one of the following options correctly identifies organisms P, Q, R and S?

Accepted Answer

B. P=Bracket fungi, Q=Bird's nest fern, R=Mango tree, S=Termite. P does not make its own food but breaks down dead matter → a decomposer fungus (bracket fungi). Q makes food using the Sun and reproduces by spores → a fern (bird's nest fern). R makes food, no spores, and its seeds are dispersed by animals → mango tree. S does not make food and does not break down dead matter → an animal (termite).

Question 3

The chart below shows how a certain type of food is digested in some parts of the human body, X, Y and Z. The width of the band (black shaded region) shows the amount of undigested food present in each part of the digestive system.

Which organs of the digestive system are correctly represented by Parts X, Y and Z?

Accepted Answer

A. X=mouth, Y=stomach, Z=small intestine. The amount of undigested food decreases from X to Z, meaning digestion proceeds and more food is broken down along the tract. Food is digested in the order mouth → stomach → small intestine, with the most undigested food at the mouth (X) and the least after the small intestine (Z).

Question 4

The diagram below shows parts A, B, C and D of a cell.

Which one of the following options correctly describes the labelled parts?

Accepted Answer

C. A: Allows all substances to pass through; B: Controls the transfer of substances in and out of the cell; C: Controls everything that happens in the cell; D: Is held by the cell membrane. A is the cell wall, which is fully permeable and allows all substances to pass through. B is the cell membrane, which controls the transfer of substances in and out of the cell. C is the nucleus, which controls everything that happens in the cell. D is the cytoplasm, which is held in place by the cell membrane.

Question 5

Four children observed two adult cats and their kitten. The table below shows the characteristics of the cats. Colour of fur — Male: Orange, Female: Orange, Kitten: Orange. Colour of eyes — Male: Brown, Female: Blue, Kitten: Blue. Presence of stripes — Male: No, Female: Yes, Kitten: Yes. Presence of fleas — Male: Yes, Female: No, Kitten: Yes.

The four children then gave statements on their observations about the cats.
Aruna: The kitten inherited two characteristics from its father.
Bala: The kitten inherited the colour of its eyes from its mother.
Charlie: The kitten inherited at least one characteristic from each of its parents.
Debbie: The female adult cat shared three common characteristics with the kitten.

Based on the table above, whose statements are correct?

Accepted Answer

C. Bala, Charlie and Debbie only. Bala is correct: the kitten's blue eyes match the mother. Charlie is correct: it shares orange fur with the father and blue eyes/stripes with the mother. Debbie is correct: the kitten and the female cat share three inherited characteristics — orange fur, blue eyes and stripes (fleas are not inherited). Aruna is wrong because fleas are an acquired characteristic, not inherited from the father.

Question 6

The diagram below shows two methods of reproduction, X and Y. Method X (Human); Method Y (Paramecium).

Which of the following statements about the two methods of reproduction, X and Y, are correct?
A: Fertilization takes place in both Method X and Y.
B: For Method X, two parents, a male and a female, are involved while for Method Y, only one parent is involved.
C: For Method X, the young has the same characteristics as the parents but for Method Y, the young does not have the same characteristics as its parent.

Accepted Answer

B. B only. Method X (human) is sexual reproduction needing a male and female parent, with fertilisation. Method Y (paramecium) is asexual reproduction (binary fission) with one parent and no fertilisation. So statement A is false (no fertilisation in Y). Statement C is false (asexual offspring are identical to the parent). Only B is correct.

Question 7

Two rings of different thickness were cut and removed from the stem of a plant as shown below. The plant was left under the sun for a week before the leaves, A, B, C and D were plucked out. A starch test was then conducted on the leaves. (One ring: 'Food-carrying tube is removed.' Another ring: 'Both water-carrying and food-carrying tubes are removed.')

Which one of the following options correctly shows the colour of iodine solution when it interacted with each leaf?

Accepted Answer

A. A=blue, B=blue, C=blue, D=blue. Iodine turns blue-black where starch is present. All four leaves remained attached to the plant, received water and were exposed to sunlight for a week, so all carried out photosynthesis and produced starch. The removed rings affect the transport of food, not the leaves' own ability to make starch, so iodine turns blue on every leaf.

Question 8

The diagram below shows the human respiratory system. (Part Y and Part Z are labelled.)

What will happen to Part Y and Part Z when air is exhaled?

Accepted Answer

B. Y=expands, Z=moves down. Per the paper's answer key, the correct option is (2). Part Y is the lungs and Part Z is the diaphragm, the structures involved in breathing movements as air moves in and out of the respiratory system.

Question 9

Study the diagram below which represents blood flowing through the body. (Positions W, X, Y and Z are marked on blood vessels around the leg muscle; 'Blood flowing to the heart' on the left and 'Blood flowing from the heart' on the right.) Blood samples of an equal amount, A, B, C and D, were taken from blood vessels at positions W, X, Y and Z in the body. The graph below shows the amount of carbon dioxide present in each of the blood sample.

Which one of the following options correctly shows where the blood samples were taken from?

Accepted Answer

B. W=Sample C, X=Sample A, Y=Sample D, Z=Sample B. Blood flowing from the heart (position X) has just been oxygenated, so it has the lowest carbon dioxide = Sample A (lowest bar). As blood passes through the leg muscle it gains carbon dioxide, so blood flowing back to the heart (position W) has the highest carbon dioxide = Sample C (tallest bar). Positions Y and Z take intermediate values (D then B), matching option B.

Question 10

The diagram below shows the different organisms living in a pond.

Which of the following statements are correct?
A: There are four animal populations.
B: There are at least two different species of submerged plants.
C: All the organisms living together are independent of one another.
D: There are at least two animal populations which spend part of their life cycles in water.

Accepted Answer

D. A, B, C and D. Based on the pond scene, there are four different animal populations (statement A), at least two different kinds of submerged plants (statement B), and at least two animal populations (such as the dragonfly and frog) that spend part of their life cycle in the water (statement D). The paper's answer key marks all four statements as correct (option 4).

Question 11

Ronaldo prepared two set-ups as shown below to investigate how the introduction of the aquatic plant and Tiger fish, respectively, would affect the population of the Spider fish. (Left set-up: plant + Spider fish; Right set-up: Tiger fish + Spider fish.)

Which one of the following set-ups should Ronaldo use as a control for his experiment?

Accepted Answer

A. A tank with only Spider fish and stones/pebbles (no plant, no Tiger fish). A control must have neither of the variables being tested (the aquatic plant and the Tiger fish), keeping everything else the same. Therefore the control tank should contain only the Spider fish (and the stones and pebbles), so its population change can be compared against the two experimental set-ups.

Question 12

Aiden conducted three experiments on food relationships in a community that consisted of a population of a plant and three populations of consumers R, S and T. He set up the experiments and tabulated his results as follows: Experiment A (Plant, R, S): Plant decreases, R remains the same, S remains the same. Experiment B (Plant, R, T): Plant decreases, R decreases, T remains the same. Experiment C (Plant, S, T): Plant decreases, S decreases, T remains the same.

Based on the above results, which one of the following shows a possible food relationship among the plant and the three animals R, S and T?

Accepted Answer

C. Plant→R and Plant→S, with both R and S eaten by T (option 3). The plant decreases in every experiment, so R and S both eat the plant. In Experiment B, R decreases only when T is present, so T eats R; in Experiment C, S decreases only when T is present, so T eats S. T always remains the same as the top consumer. This matches option 3: Plant→R, Plant→S, and both R and S are eaten by T.

Question 13

Mr Poh went to the Jurong Bird Park and obtained feathers from four different birds. He dipped the four feathers in water and recorded the time taken for each of them to dry in the table below. Feather P: 200 seconds; Feather Q: 100 seconds; Feather R: 30 seconds; Feather S: 80 seconds. Bird Z as shown below can be found near a river.

Which one of the following feathers would most likely belong to Bird Z?

Accepted Answer

C. Feather R. A bird living near water (a duck-like bird) has waterproof feathers that repel water, so they hold little water and dry the fastest. Feather R took the shortest time to dry (30 seconds), so it is the most water-repellent and most likely belongs to Bird Z.

Question 14

Study the table below carefully. Row A — Positive impact: Using a CFC-free hair spray; Negative impact: Using leaded petrol; Activity that causes pollution: Lead poisoning from burning of fuels; Prevention: Use unleaded petrol. Row B — Positive impact: Burning trees to clear the land for plantations; Negative impact: Planting trees in previously deforested areas; Activity: Emission of greenhouse gases; Prevention: Increase the use of fossil fuels. Row C — Positive impact: Taking a taxi to work instead of a bus; Negative impact: Treating sewage before disposal; Activity: Soil erosion; Prevention: Reduce the use of pesticides. Row D — Positive impact: Using genetic selection to increase crop yield; Negative impact: Burning trees to clear the land for plantations; Activity: Excessive use of pesticide; Prevention: Use natural predators to control pests.

Which of the following options have activities that are wrongly classified?

Accepted Answer

B. B and C only. Row A and Row D are correctly classified. Row B is wrong: burning trees is negative (not positive), planting trees is positive (not negative), and increasing fossil-fuel use is harmful (not a prevention). Row C is wrong: taking a taxi instead of a bus is negative (not positive) and treating sewage is positive (not negative). So B and C are wrongly classified.

Question 15

Joyce collected a sample of water from a stream flowing near a farm each month and measured the amount of light that could pass through it using a light sensor connected to a datalogger as shown in the diagram below. The readings for the month of January to June are recorded in the table below. Jan: 25 lux; Feb: 26 lux; Mar: 30 lux; Apr: 25 lux; May: 9 lux; June: 5 lux.

Which one of the following reasons best explains the drastic change in the readings in May and June?

Accepted Answer

C. Many crops were harvested and no new crops were grown before a rainstorm.. The light passing through the water dropped sharply in May and June, meaning the water became murkier. If crops were harvested leaving bare soil before a rainstorm, soil would be washed (eroded) into the stream, making the water cloudy and reducing the amount of light that can pass through.

Question 16

Jason set up an experiment as shown below. When the switch was closed, the rod attracted some iron nails while the rest remained on the tray. He then repeated the experiment using the same set up with rods B, C and D. Jason then recorded the results as shown in the table below. Rod A: 26 nails left on the tray; Rod B: 30; Rod C: 29; Rod D: 10.

Based on the above results, which rod would be the most suitable for making an electromagnet to separate magnetic from non-magnetic material?

Accepted Answer

D. D. The most suitable rod makes the strongest electromagnet, which attracts the most iron nails and therefore leaves the fewest nails on the tray. Rod D left only 10 nails on the tray (the fewest), so it attracted the most nails and makes the strongest electromagnet.

Question 17

An experiment was conducted to investigate whether light can pass through sheets A, B, C and D which were made of different materials. The sheets were arranged at equal interval in two set-ups, X and Y as shown. A bright spot of light was observed on Sheet C in Set-up X and Sheet D in Set-up Y. (Set-up X order: Sheet A, Sheet B, Sheet C, Sheet D. Set-up Y order: Sheet D, Sheet A, Sheet B, Sheet C.)

Based on the results, which one of the following options correctly shows the property of the materials that sheets A, B, C and D are made of (Does it allow light to pass through?)?

Accepted Answer

B. A=Yes, B=Yes, C=No, D=No. In Set-up X (order A, B, C, D) the bright spot appears on C, so light passed through A and B (transparent) and was stopped at C (opaque). In Set-up Y (order D, A, B, C) the bright spot appears on the first sheet D, so D is opaque. This matches: A=Yes, B=Yes, C=No, D=No (option 2).

Question 18

Hashim was given 4 similar beakers, A, B, C and D. Each beaker was filled with different substances as shown in the following diagram. Beaker A: rose syrup; Beaker B: stones; Beaker C: sand; Beaker D: air. He poured water into the beakers at the same rate, one at a time and measured the time taken for the content in each beaker to overflow.

Which one of the following graphs shows the time taken for the content to overflow?

Accepted Answer

C. Increasing bars: A shortest, then B and C, D tallest. The time to overflow depends on how much empty space is left to be filled with water. Beaker A (rose syrup) is already mostly filled, so it overflows fastest (shortest time). Beaker D (only air, empty) has the most space, so it takes the longest. Beakers B (stones) and C (sand) have intermediate amounts of empty space, giving the rising pattern in graph 3 (A lowest, B and C higher, D highest).

Question 19

Christie used wax to attach a plastic cube onto a panel made of Material P as shown below. Christie recorded the time taken for the plastic cube to slide down the panel. She repeated the experiment using similar panels of equal thickness but made of different materials, Q, R and S. The results are shown in the table below. Material P: 50 s; Material Q: 80 s; Material R: 100 s; Material S: 75 s.

Based on the above results, which of these materials are the most suitable to make the following items (Base of an electric iron / Handle of a frying pan)?

Accepted Answer

D. Base of an electric iron=P, Handle of a frying pan=R. The faster the cube slides, the better the material conducts heat (the wax melts sooner). Material P (50 s) is the best conductor and Material R (100 s) is the best insulator. The base of an electric iron needs a good conductor (P) to transfer heat, while the handle of a frying pan needs a good insulator (R) to keep hands cool.

Question 20

The diagram below shows an empty conical flask with a T-shaped tube. X and Y are two drops of ink in the tube. The conical flask was then immersed in a trough of hot water at 95°C. (Positions 1, 2 and 3 are marked along the tube; drop X near position 1 and drop Y near position 3.)

What will be observed after the conical flask is immersed into the hot water for 10 minutes?

Accepted Answer

B. X will move towards Position 2 and Y will move towards Position 3.. When the flask is immersed in hot water, the air inside is heated and expands. The expanding air pushes the ink drops along the tube in the direction of air flow, so drop X moves towards Position 2 and drop Y moves towards Position 3 (option 2).

Question 21

A beaker of boiling water was left to boil for 10 minutes. It was then left on a table to cool down. When the water reached room temperature for a while, some ice cubes are added. The following graph was plotted to show the change in temperature. (Graph points A-B flat at top, B-C falling, C-D flat, D-E falling; 10 min and 55 min marked.)

Based on the above graph, four students each made a statement.
Winnie: Ice cubes were added at Point D of the graph.
Xue Min: No condensation occurred during the experiment.
Yahya: There was a change of state at Point A to B in the experiment.
Zoe: The water eventually changed to solid state after 55 minutes.

Whose statement(s) is/are correct?

Accepted Answer

C. Winnie and Yahya only. Winnie is correct: the temperature drops again at Point D, which is when the ice cubes were added. Yahya is correct: A to B is the flat boiling stage, where water changes state from liquid to gas. Xue Min is wrong because condensation of steam does occur during boiling. Zoe is wrong: after 55 minutes the water only cools (D to E) and does not freeze into a solid (no plateau at the freezing point).

Question 22

Study the following electrical circuit. (A circuit with several bulbs, two batteries and four switches S1, S2, S3 and S4.)

Which of the following switches S1, S2, S3 and S4 must be closed for all the bulbs to light up?

Accepted Answer

A. S1 and S4 only. For every bulb to light, the switches must be closed so that a complete circuit passes current through all the bulbs. Based on the circuit layout, closing only S1 and S4 completes the path through all the bulbs, so option (1) is correct.

Question 23

Anne used a circuit tester to test a circuit card as shown below. She recorded her observations in the table below. A and B: Does not light up; A and C: Lights up; C and D: Lights up; B and C: Does not light up; B and E: Does not light up; A and D: Lights up.

Based on the above results, which one of the following represents the correct circuit card?

Accepted Answer

B. A joined to C, and C joined to D and E, with B separate (option 2). The bulb lights only when two connected clips are tested. A&C, C&D and A&D light up, so A, C and D are all connected together. A&B, B&C and B&E do not light up, so B is not connected to A, C or E. Option 2 shows A, C, D (and E) joined with B isolated, which fits all the results.

Question 24

Sam carried out an experiment to find out the electrical conductivity of rods W, X, Y and Z as shown below. His findings, when the switch was closed, were shown in the table below. Rods removed from the circuit / Did the bulb light up? — W: yes; X and Y: yes; W, X and Y: no; W, Y and Z: no.

Based on the above results which one of the following correctly represents the materials of rod W, X, Y and Z?

Accepted Answer

A. W=steel, X=glass, Y=copper, Z=plastic. The rods are parallel paths; the bulb lights if any remaining rod is a conductor. Removing W, X and Y leaves only Z and the bulb does not light → Z is an insulator. Removing W, Y and Z leaves only X and the bulb does not light → X is an insulator. Removing W still lights (so Y conducts), and removing X and Y still lights (so W conducts). Thus W and Y are conductors, X and Z are insulators: W=steel, X=glass, Y=copper, Z=plastic (option 1).

Question 25

Devi set up the experiment as shown in Set-up A. She slid the magnet slowly towards the metal paper clip until the paper clip was attracted to magnet. She recorded the distance between the magnet and the metal paper clip when the attraction occurred. Devi then repeated the experiment by using the same wooden plank which is raised to a height as shown in Set-up B. For each set-up, the experiment is repeated twice. Set-up A: 1st try 1.6 cm, 2nd try 1.5 cm; Set-up B: 1st try 0.8 cm, 2nd try 0.7 cm.

Based on the results in the table, which of the following statement(s) is/are correct?
A: The magnetic force of attraction can act at a distance.
B: The magnetic force of attraction is weaker in Set-up A than in Set-up B.
C: The force of gravity acting on the paper clip in Set-up B is more than Set-up A.

Accepted Answer

B. A and B only. Statement A is correct: the paper clip is attracted before touching the magnet, so the magnetic force acts at a distance. Statement C is wrong: it is the same paper clip, so the force of gravity acting on it is the same in both set-ups. The paper's answer key marks A and B as correct (option 2).

Question 26

Ah Soon carried out an experiment with three different springs in which he hung masses on them. Based on his results, he plotted the line graphs as shown below. (Length of spring (cm) against Mass (g) for Spring A, Spring B and Spring C.)

What could Ah Soon conclude from the line graphs above?
A: Spring C is the least elastic.
B: When the mass is doubled, the length of Spring A is also doubled.
C: The extension of Spring A is the same with every 25g of mass added.
D: When a mass of 100g is hung on Spring B, the extension of the spring is 20cm.

Accepted Answer

B. A and C only. Statement A is correct: Spring C stretches the least (smallest slope), so it is the least elastic. Statement C is correct: Spring A's line is straight, so it extends by the same amount for every equal mass added. Statement B is wrong: length includes the original length, so doubling the mass does not double the length. Statement D is wrong: at 100 g Spring B has length 20 cm but its original length is 10 cm, so the extension is only 10 cm.

Question 27

Marie set up a spring suspended on a retort stand as shown in the following diagram. The original length of the spring is 5 cm. She then hung four different objects, A, B, C and D in different combinations on the spring and recorded her results in the table below. A: 10 cm; A and B: 20 cm; B and D: 18 cm; A, C and D: 25 cm.

Based on the above results, arrange the objects according to their mass, from the lightest to heaviest.

Accepted Answer

D. D, A, B and C. Extension = length − 5 cm. Object A: 10−5 = 5 cm. A+B: 20−5 = 15 cm, so B = 10 cm. B+D: 18−5 = 13 cm, so D = 13−10 = 3 cm. A+C+D: 25−5 = 20 cm, so C = 20−5−3 = 12 cm. Since extension is proportional to mass, the order from lightest to heaviest is D (3), A (5), B (10), C (12) = option 4.

Question 28

Wei Wei hung a rubber band on a triangle which is a percussion instrument and then hit it with a metal rod as shown in the diagram below. After hitting for several minutes, the rubber band dropped off the triangle.

Which one of the following options shows the energy conversion from the time the triangle was hit by the metal rod to the point when the rubber band dropped?

Accepted Answer

C. kinetic energy (metal rod) → sound energy (triangle) + kinetic energy (triangle and rubber band). The moving metal rod has kinetic energy. When it strikes the triangle, this kinetic energy is converted into sound energy (the triangle rings) and kinetic energy of the vibrating triangle and rubber band. This matches option 3.

Question 29

Thomas carried out an investigation to measure the distance travelled by a battery operated toy car in 1 minute along different track surfaces made of materials A, B, C and D. He then recorded the results of the investigation in the following table. Track surface A: 37.5 m; B: 40.2 m; C: 35.3 m; D: 29.6 m.

Based on the results, which one of the track surfaces would be the most suitable to make the surface of a slide in the playground?

Accepted Answer

B. B. A slide should be smooth with the least friction so that a person can slide down easily. The track surface with the least friction lets the toy car travel the farthest. Surface B gave the greatest distance (40.2 m), so it has the least friction and is most suitable for a slide.

Question 30

Study the diagram below which shows the energy conversion for activities A, B, C and D. (Electrical energy ↔ Kinetic energy ↔ Heat energy, with conversions labelled A: Electrical→Kinetic, B: Kinetic→Heat, C: Kinetic→Electrical, D: Electrical→Heat.)

Which one of the following options best describes activities A, B, C and D?

Accepted Answer

A. A=switching on a ceiling fan, B=striking a matchstick, C=operating a turbine, D=switching on a toaster. A is Electrical→Kinetic energy = switching on a ceiling fan. B is Kinetic→Heat energy = striking a matchstick (friction). C is Kinetic→Electrical energy = operating a turbine (a generator). D is Electrical→Heat energy = switching on a toaster. This matches option 1.

P6 Science SA2 2015 — Methodist Girls

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P6 Science SA2 2015 — Methodist Girls

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