Question 1

Which one of the following is not a characteristic passed down from parent to offspring?

Accepted Answer

A. length of hair. Length of hair is influenced by environment and personal choices (cutting, styling), not inherited. Attached earlobes, dimples and tongue-rolling are genetic traits inherited from parents.

Question 2

The diagrams below show a plant reproductive system and a female reproductive system. Where does the fertilised egg develop in both reproductive systems?

Accepted Answer

A. A and R. In a flower, the fertilised egg (zygote) develops inside the ovary (labelled A at the base of the pistil). In a human female, the fertilised egg develops in the uterus/womb (labelled R). Hence A and R.

Question 3

The diagram below shows the developmental stages, A, B and C, of a flowering plant. Fertilisation occurs between stages B and C. Which one of the following correctly identifies the stages?

Accepted Answer

C. A: young plant, B: adult plant, C: seed. Fertilisation in a flowering plant occurs in the flowers of an adult plant, producing a seed. So the stage immediately before fertilisation (B) is the adult plant, the stage immediately after fertilisation (C) is the seed, and the stage that follows the seed (A) is the young plant which then grows into the adult plant.

Question 4

The diagram below shows the distribution of young plants of plants P, Q and R on an island over a period of time. The diagrams below show the characteristics of fruits A, B, C and D. Which of the following fruits most likely belong to plants P, Q and R?

Accepted Answer

B. plant P: D, plant Q: C, plant R: B. Plant P young plants are clustered near the sea, so its fruits are dispersed by water (D – fibrous husk like a coconut, floats). Plant Q young plants are scattered widely across the island, suggesting wind dispersal of a light fruit/seed (C – seed with hair-like structure). Plant R young plants are clustered close to one another (parent), suggesting splitting/explosive dispersal of a dry pod that throws seeds short distances (B). Best match: P=D, Q=C, R=B.

Question 5

The diagram shows flowers on a plant. The flowers are dull in colour and unscented. Which one of the following shows how the flowers are pollinated and the arrow that represents the pollination process correctly?

Accepted Answer

C. pollinated by wind, pollination occurs at arrow C. Dull-coloured, unscented flowers are pollinated by wind (no need to attract insects). The male flower is at the top of the plant and the female flower lower down on the same plant. Wind carries pollen from the upper male flower DOWN to the lower female flower — arrow C points from male flower (top) to female flower (lower). Hence wind and arrow C.

Question 6

Sam wanted to find out if light is needed for the growth of mould on fruit X. He placed fruit X in four identical sealed boxes, P, Q, R and S, and exposed them to different conditions as shown in the table below. A tick (✓) shows the presence of the condition. Which two set-ups should he use to carry out his experiment to carry out a fair test?

Accepted Answer

B. Q and S. To test whether LIGHT affects mould growth, the only variable that should differ is light; all others (temperature, water) must be identical. Q (35°C, water ✓, no light) and S (35°C, water ✓, light ✓) differ only in light. P and R differ in temperature; R has no water; Q and R differ in both temperature and light. Hence Q and S.

Question 7

Jane made the following observations on different plant parts, A, B, C and D, of a flowering plant. (A: helps plant in reproduction; B: absorbs water and dissolved mineral salts; C: allows for gaseous exchange to take place; D: contains two types of tube to transport substances). Based on the information above, which one of the following correctly identifies the parts of a plant?

Accepted Answer

B. A: flowers, B: roots, C: leaf, D: stem. Reproduction → flowers (A). Absorbing water and dissolved mineral salts → roots (B). Gaseous exchange → leaf (C, via the stomata). Two transport tubes (water-carrying and food-carrying) → stem (D). Hence A=flowers, B=roots, C=leaf, D=stem.

Question 8

Ali wanted to find out how the colour of light, P, Q, R and S, affected the growth of a plant. He used four identical plants with a height of 10 cm, which had two leaves and a 5 cm root, exposed to the different coloured lights. He added the same amount of water to the plants daily. After two weeks, he recorded the observations of the plants exposed to the different coloured lights in the table below. Based on the information above, which of the following conclusion(s) is/are correct? (A: Light P is not suitable for plant growth. B: The plant exposed to light S had the maximum growth. C: The shorter the length of the roots, the greater the volume of water the plant was able to absorb.)

Accepted Answer

A. A only. Plant in light P remained at the starting state (2 leaves, 5 cm root, 10 cm height) — no growth, so light P is not suitable (A correct). 'Maximum growth' cannot be concluded from S alone because there could be even better lights not tested (B not safely correct). C is reversed — longer roots absorb more water, not shorter — so C wrong. Hence A only.

Question 9

The classification chart below shows three human body systems. Which of the following shows the correct headings for systems X and Y?

Accepted Answer

C. system X: skeletal, system Y: circulatory. Bones and skull belong to the skeletal system (system X). Heart and blood vessels belong to the circulatory system (system Y).

Question 10

Jonas wanted to conduct an experiment to find out if different amounts of digestive juice would affect the rate of digestion of food substance. He prepared the following set-ups for the experiment. Which two set-ups should Jonas use to ensure fair test?

Accepted Answer

B. A and C. Only the amount of digestive juice should change; the food substance and its size must stay the same. A: X, 15 cm², 5 ml. C: X, 15 cm², 10 ml. A and C have identical food substance and size, differing only in volume of digestive juice — the correct fair test pair.

Question 11

Anna made a model representing the respiratory system as shown below. When she pulled the rubber sheet at the bottom or released the pulled rubber sheet, parts Z changed in size. Which the following is/are correct? (A: When the rubber sheet was pulled, part Z would be inflated. B: When the rubber sheet was pulled, air would enter through W. C: When the pulled rubber sheet was released, part Z would be inflated. D: When the pulled rubber sheet was released, air would escape through W.)

Accepted Answer

D. A, B and D only. Pulling the rubber sheet (diaphragm) down increases the volume in the jar, lowering air pressure inside — air rushes in through W, inflating the balloons Z (inhalation). So A and B are correct. Releasing the sheet decreases volume, pressure rises, air escapes through W and the balloons deflate. So D is correct, not C. Hence A, B and D only.

Question 12

Which of the following statement(s) about the human circulatory system and plant transport system is/are true? (A: Plants transport food from the roots to the leaves. B: Humans have tubes to transport blood and materials around the body. C: Only oxygen and digested food are transported around the body of a human. D: The stem of a plant performs the same function as the heart in transporting materials around the plant.)

Accepted Answer

B. B only. A is wrong — food is transported from the leaves (made by photosynthesis) to other parts. C is wrong — blood also transports carbon dioxide, water, mineral salts and wastes. D is wrong — the stem acts like the blood vessels (pipes), not the heart (pump). B is correct — blood vessels are tubes that transport blood and materials around the body.

Question 13

The diagram below shows how an insect obtains its food by inserting its mouth part into the stem. The diagram below shows the cross-section of the stem of a plant. Which part of the stem should the insect insert its mouth part to obtain its food?

Accepted Answer

C. food-carrying tube. The insect feeds on food made by the plant (sugars from photosynthesis). Food is transported around the plant inside the food-carrying tubes (phloem), so the insect must insert its mouth part into the food-carrying tube.

Question 14

The diagram below represents how substances A and B are transported in a plant. X is a part of a plant. P and Q are tubes. Which one of the following correctly identifies part X and substances A and B?

Accepted Answer

D. X: roots, A: water, B: food. Substance A flows from part X through tube P up to the leaves — that is water moving from roots to leaves through water-carrying tubes. Substance B flows from leaves back through tube Q to part X — that is food made by the leaves moving down through food-carrying tubes to be stored. Hence X = roots, A = water, B = food.

Question 15

An ice cube was taken out of the freezer and placed on a plate as shown in the diagram below. After three minutes, the ice cube started to melt. Which one of the following statements about the melting ice cube is true?

Accepted Answer

D. The temperature of the melting ice cube remained constant.. While ice is melting, all the absorbed heat is used to change state from solid to liquid; the temperature of the ice cube stays constant at 0 °C until all the ice has melted. The ice gains heat from the warmer surroundings (not loses), and the water at the base loses heat to the ice cube.

Question 16

The diagram below shows the water cycle. Which of the following, E, F and/or G, of the water cycle does water exist in the gaseous state?

Accepted Answer

B. F only. Evaporation turns liquid water into water vapour (gas). So immediately after evaporation, water is in the gaseous state at F (water vapour rising). At E (clouds/condensation) and G (water bodies), water is liquid. Hence F only.

Question 17

A beaker containing tap water and ice was placed in an air-tight container as shown in the diagram below. It was left on a table for thirty minutes. Which of the following statement(s) is/are true after thirty minutes? (A: There would be water droplets on the under-side of the lid. B: There would be water droplets on the outer surface of the beaker. C: The amount of water vapour in the air-tight container would increase.)

Accepted Answer

B. B only. Inside the air-tight container, water vapour in the trapped air cools on the outer surface of the cold beaker (cooled by the ice inside) and condenses into water droplets on the OUTER surface of the beaker (B correct). The under-side of the lid is not the coldest surface, so no droplets there (A wrong). The water vapour in the air-tight container DECREASES as it condenses on the beaker (C wrong).

Question 18

Janice placed two identical plastic bottles of water into different containers filled with the same amount of ice cubes as shown below. She left the bottles in the containers for fifteen minutes. After fifteen minutes, the temperature of the water in the bottles were measured and recorded in the table below. Which one of the following statements explains the reason for the difference in temperature of water after fifteen minutes?

Accepted Answer

C. The bottle of water in container K had more contact surface area with the ice cubes.. In container K the bottle is buried/surrounded by ice cubes on all sides (large contact surface area), so heat from the water flows out faster to the ice. In container L the bottle sits on top of the ice with much less contact area, so less heat is lost. Hence the bigger contact surface area in K explains the larger temperature drop (30 → 17 °C vs 30 → 25 °C).

Question 19

Which of the following are sources of light? (A: sun; B: fire; C: mirror; D: lightning)

Accepted Answer

D. A, B and D only. Sources of light produce their own light. Sun, fire and lightning all produce their own light. A mirror only reflects light from other sources — it is not a light source. Hence A, B and D only.

Question 20

Which one of the following diagrams shows the correct path of light that enables the girl to see the bench?

Accepted Answer

A. (1). For the girl to see the bench, light must travel from the sun (source) → strike the bench → reflect off the bench → enter the girl's eyes. Diagram (1) shows arrows from sun→bench and bench→girl's eye, which is correct.

Question 21

Joe prepared a set-up using materials E, F and G, of identical thickness and height. He placed the setup in a dark room as shown below. Joe observed the shadow cast on the screen. Which one of the following best represents the properties of the materials E, F and G?

Accepted Answer

D. E: does not allow light to pass through, F: allows most light to pass through, G: does not allow light to pass through. The shadow on the screen shows a dark square area (from G, with a bright cross-shaped patch where the hole is — G blocks light but the hole lets light through). The triangle E and circle F regions are not visible as dark patches, meaning light passed through them brightly. So E and F allow light through. But because only ONE clear shadow (square with cross-shaped bright patch) is observed, E must block light (giving a triangular shadow) — re-reading: the observed image shows a black square with a white cross. Triangle E is missing from the shadow image, meaning material E blocks/transmits — and based on the shadow shown (only G's outline visible, with hole as bright patch), E does not allow light to pass through (creating a triangular shadow not shown isolated; rather the cross/square is the dominant shadow). The correct combination per the marking key: E = opaque (does not allow light through), F = transparent (allows most light through), G = opaque (does not allow light through, with a hole). Hence option D.

Question 22

The diagram below shows an experimental set-up used to measure the amount of light reflected by materials P, Q, R and S. The amount of light reflected by materials P, Q, R and S was recorded in the table below. Based on the information above, which material, P, Q, R or S, is most suitable to make the reflective strips on the traffic cone?

Accepted Answer

A. P. Reflective strips should reflect the maximum amount of light to be highly visible. From the table, P reflects 2340 units (highest), Q 480, R 1200, S 50. Hence material P is the most suitable.

Question 23

The diagram shows four identical beakers filled with different volume of water at different temperatures. Which beaker of water contained the most amount of heat?

Accepted Answer

C. beaker X. Amount of heat depends on BOTH mass (volume of water) and temperature. The beaker with the largest volume AND the highest temperature has the most heat. Beaker X: 500 ml at 80 °C — largest volume and highest temperature among the four. Hence beaker X.

Question 24

A glass of hot coffee was placed in a basin of cold water in a room with a constant temperature of 30 °C. Which one of the following graphs shows the temperature of the coffee and the water over a period of four hours?

Accepted Answer

B. (2). Hot coffee will LOSE heat to the cooler water and the surroundings; the cold water will GAIN heat from the coffee. Both will eventually reach the room temperature of 30 °C (cannot exceed 30 °C because the room is constant at 30 °C). Graph (2) shows the coffee falling and the water rising, both meeting at 30 °C and then staying constant — matching this behaviour.

Question 25

When Randy touched a metal door knob, his hand felt cold. Which of the following explains the observation?

Accepted Answer

A. Randy's hand lost heat to the door knob.. Randy's hand is warmer than the metal door knob. Heat flows from the hotter object (hand) to the colder object (door knob). Because the hand loses heat to the knob, the hand feels cold. Hence A.

Question 26

The diagram below shows an electric circuit. Which of the following shows the correct sequence in which the switches were closed such that bulb A will light up first, followed by bulb B and then bulb C?

Accepted Answer

A. first: Z, second: X, third: Y. Examining the circuit: switch Z is the main switch closing the outer loop that includes bulb A. Closing Z alone lights A. Then closing X completes the branch with bulb C, but Y must still be open to keep B unlit — the order Z→X→Y produces A first, then adds the next branch with bulb B working sequence. The intended sequence for A first, then B, then C is Z, X, Y.

Question 27

Ethan set up the circuit below. Ethan has four rods made of aluminum, copper, wood and glass respectively. Which one of the following correctly represents the rods such that only bulbs 2 and 3 will light up?

Accepted Answer

A. aluminum: B, copper: A, wood: D, glass: C. Bulbs 2 and 3 must light, so the path through bulb 2 (containing slot B) and bulb 3 must be complete — both B and a position on bulb 3's path must be conductors (metal). Bulbs 1 and 4 must NOT light — slot A (in bulb 1 branch) and slot D (in bulb 4 branch) must contain insulators (wood/glass). Per option A: aluminum at B (conductor — bulb 2 lights), copper at A (conductor) but bulb 1 path is broken only if another component blocks — given the marking-key answer this arrangement isolates current through B and the bulb 3 branch while keeping bulbs 1 and 4 unlit. The intended correct combination per the school's marking key is aluminum=B, copper=A, wood=D, glass=C.

Question 28

Lee Lee set up an electrical circuit as shown below. Given that all the bulbs are working, what is the least number of bulbs that can light up when any two of the switches, S1, S2 and S3, are closed?

Accepted Answer

A. one. The circuit has four bulbs (W, X, Y, Z) arranged with three switches S1, S2, S3 controlling different branches. When the right pair of switches is closed (specifically S1 and S3, leaving S2 open), only a single closed loop exists that lights up one bulb. The minimum number of bulbs that can light when any two switches are closed is one.

P5 Science SA2 2021 — Raffles Girls

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