Question 1

Study the table below.
Which two examples have been placed in the wrong group?

Accepted Answer

(2) Moon and fire. Light sources include objects that produce their own light (like the Sun and Stars). Fire also produces light. Non-light sources are objects that reflect light or do not produce light (like a Book, Mirror, and Moon, as the Moon reflects sunlight). In the given table, Moon is incorrectly listed as a light source, and Fire is incorrectly listed as a non-light source. Therefore, Moon and Fire are the two examples placed in the wrong group.

Question 2

Mary had three sheets of materials, J, K and L, made of different materials. She observed that when she placed the ball behind the three sheets, she could not see the ball.
However, when she placed the ball between sheets K and L, she could see the ball and its shadow on sheet L only.
Based on her observations above, which of the following is correct?

Accepted Answer

(1) Allow light to pass through for J, Allow light to pass through for K, Does not allow light to pass through for L. From the second observation, 'when she placed the ball between sheets K and L, she could see the ball and its shadow on sheet L only':
1. For the ball to be seen, light from the torch must reach and illuminate it. This means light must pass through sheet J and sheet K. Therefore, J and K must allow light to pass through.
2. For a shadow to be cast 'on sheet L', sheet L must be opaque (does not allow light to pass through) to act as a screen.
Combining these deductions, J allows light to pass through, K allows light to pass through, and L does not allow light to pass through. This matches option (1).
Let's check this with the first observation: 'when she placed the ball behind the three sheets, she could not see the ball'. If the ball is behind L, and L does not allow light to pass through (is opaque), then the ball would not be visible. This is consistent. (Note: The provided answer key indicates option (2), but this is physically contradictory to the observation 'could see the ball and its shadow on sheet L only' if K does not allow light to pass through, as the ball would not be illuminated by the torch.)

Question 3

Kathy walked from position S to position T, and then walked to position U in a straight line under the light bulb.
Which one of the following graphs shows how the length of her shadow changed as she walked from S to T then to U?

Accepted Answer

(3) Length of shadow decreasing then increasing with position, starting from a longer shadow at S. When an object moves towards a point directly under a light source, its shadow length decreases. When it moves away from that point, its shadow length increases. The light bulb is directly above position T.
- As Kathy walks from S to T, she is moving closer to the point directly under the light source. Therefore, her shadow length will decrease.
- As Kathy walks from T to U, she is moving away from the point directly under the light source. Therefore, her shadow length will increase.
This means the graph should show a decrease in shadow length from S to T, followed by an increase from T to U. Graph (3) correctly depicts this pattern, starting with a longer shadow at S, decreasing to a minimum at T, and then increasing towards U.

Question 4

The diagram below shows a plant.
Which of the following statements represent the function of part W?
A Holds the plant upright
B Absorbs water and mineral salts
C Holds the plant firmly to the ground
D Transports food, water and mineral salts to different parts of the plant
(1) A and B only
(2) A and D only
(3) B and C only
(4) C and D only

Accepted Answer

(3) B and C only. Part W in the diagram represents the roots of the plant. The primary functions of roots are:
- B: Absorbing water and mineral salts from the soil.
- C: Holding the plant firmly to the ground, providing anchorage.

Statement A ('Holds the plant upright') is primarily a function of the stem, although roots contribute by anchoring. Statement D ('Transports food, water and mineral salts to different parts of the plant') is primarily a function of the plant's vascular tissues (xylem and phloem), which are found in the stem, leaves, and roots, but the main transport 'to different parts' happens in the stem. Therefore, the most accurate functions for roots among the given options are B and C. (Note: The provided answer key indicates option (2), which states A and D, but these are not the primary or most accurate functions of the roots themselves in the context of typical primary school biology.)

Question 5

Sue wanted to find out if the amount of roots affect the amount of water a plant absorbs. She placed 4 of plant X in four different set-ups, as shown below.
Which two set-ups should she choose to find out if the amount of roots will affect the amount of water absorbed by the plant?

Accepted Answer

(2) A and D only. To investigate if the 'amount of roots' affects the 'amount of water absorbed', a fair test requires that only the 'amount of roots' (the independent variable) differs between the two set-ups, while all other factors (controlled variables) are kept constant.
- Set-up A: Plant X with many roots, water, and an oil layer.
- Set-up B: Plant X with fewer roots, water, and an oil layer.
- Set-up C: Plant X with many roots, water, but NO oil layer (allows for evaporation, which affects water level change not solely due to plant absorption).
- Set-up D: Plant X with fewer roots, water, and an oil layer.
To compare the effect of root amount, we need one plant with many roots and one with fewer roots, with all other conditions identical. Set-up A (many roots) and Set-up D (fewer roots) both have an oil layer and use Plant X, making them suitable for comparison. Set-up C is unsuitable due to the missing oil layer. Set-ups B and D both have fewer roots, so they cannot be used to compare different amounts of roots.

P4 Science SA1 2025 — Nanyang

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