Question 1

The diagram shows the change of state of water. Which of the following correctly represents the process X and heat flow at Y?

Accepted Answer

(3) Melting, Heat gain. Process X shows the change from solid to liquid, which is melting. Process Y shows the change from liquid to gas (evaporation or boiling). For a liquid to change to a gas, it must absorb or gain heat from its surroundings. Therefore, Process X is melting, and heat flow at Y is heat gain.

Question 2

Study the water cycle below. Which of the following is correct?

Accepted Answer

(1) Water Vapour, Clouds, Trees. In the water cycle, water from 'rivers and seas' evaporates to form 'A', which is water vapour. This water vapour rises and condenses to form 'B', which are clouds. 'C' represents precipitation from clouds, which can fall as rain and be absorbed by 'Trees' before eventually returning to rivers and seas.

Question 3

Mary placed a cup of tap water in the refrigerator which was set at 5°C. She measured the change in temperature of tap water and plotted a graph. Which of the following is the graph she plotted?

Accepted Answer

(3) Temperature (°C). Tap water typically starts at room temperature (e.g., around 25-30°C), which is higher than 5°C. When placed in a refrigerator set at 5°C, the water will continuously lose heat to its colder surroundings until its temperature drops and stabilizes at the refrigerator's temperature, 5°C. Graph (3) correctly shows the temperature starting high, decreasing over time, and then leveling off at 5°C.

Question 4

Hui Hui poured an equal amount of water into the beakers. However, the temperature of water was different. Water droplets were formed as shown below. Which one of the following shows the beakers of water arranged from the lowest to the highest temperature?

Accepted Answer

(4) C, A, D, B. The amount of water droplets (condensation) formed on the outside of a beaker is proportional to how cold the water inside the beaker is, as a colder surface will cause more water vapour from the surrounding air to condense. Beaker C has the most droplets, indicating the lowest temperature. Beaker A has a moderate amount. Beaker D has fewer droplets than A but more than B. Beaker B has the fewest droplets, indicating the highest temperature. Therefore, from lowest to highest temperature, the order is C, A, D, B.

Question 5

The table shows the state of three substances, P, Q and R, at different temperatures. Which statement can be concluded?

Accepted Answer

(3) R has a higher freezing point than Q.. For P, it is liquid at 10°C, 30°C, and 50°C, so its boiling point must be above 50°C. Statement (1) is incorrect. For Q, it is solid at 30°C and liquid at 50°C, meaning its melting point is between 30°C and 50°C. Statement (2) is incorrect as its melting point is not necessarily 50°C. For R, it is solid at 10°C, 30°C, and 50°C, meaning its melting point (and thus freezing point) is above 50°C. Since Q's freezing point is between 30°C and 50°C, R has a higher freezing point than Q. Statement (3) is correct. For Q, at 40°C, it would be either solid, liquid, or melting, depending on its exact melting point; we cannot conclude it's in both solid and liquid states unless 40°C is its precise melting point. Statement (4) is incorrect.

Question 6

In some buildings, water mist systems are used to cool the surrounding air. Which of the following explains how mist can cool the surrounding air?

Accepted Answer

(3) Warm surrounding air loses heat to the water droplets.. Water mist cools the surrounding air through the process of evaporation. When the tiny water droplets in the mist evaporate, they absorb latent heat from the surrounding environment. This means the warm surrounding air loses heat to the water droplets to facilitate their evaporation, causing the air itself to cool down.

Question 7

Jean conducted an experiment on rate of evaporation using the set-up below. She measured the amount of water left in the bucket after some time. Jean repeated the experiment by increasing variable X and keeping all other variables the same. Her results are shown below. What could variable X be?

Accepted Answer

(1) speed of the fan. The bar chart shows that as Variable X increases, the amount of water left decreases, which means the rate of evaporation increased. Increasing the speed of the fan (more air movement) increases the rate of evaporation by sweeping away water vapour. Options (2) and (3) also increase evaporation with an increase, but given the visual setup explicitly includes a fan, changing the 'speed of the fan' is the most direct manipulation of the shown apparatus to affect evaporation. Increasing the 'distance between the fan and the bucket' would decrease air movement and thus decrease evaporation, contradicting the graph.

Question 8

The diagram below shows the windows of two bedrooms, A and B, when the air conditioner was switched on. Which of the following explains why the windows of both bedrooms was fogged?

Accepted Answer

(2) Water droplets were formed outside the bedroom.. When the air conditioner is switched on, the internal temperature of the bedrooms (and thus the window panes) becomes cool. The surrounding outdoor air is warm and often humid (stated 35°C). When this warm, humid water vapour from *outside* the bedroom comes into contact with the cooler outer surface of the window, it loses heat and condenses into tiny water droplets, forming fog. This means the water droplets are formed outside the bedroom.

Question 9

Jerry observed that there was less fogging on window of bedroom A. Which of the following are the likely causes?
A Water vapour outside bedroom B was warmer.
B The temperature inside bedroom A was higher than B
C The rate of evaporation outside bedroom A was slower than B.
D Water vapour outside bedroom B condensed faster than A.

Accepted Answer

(4) B and D. Less fogging on window A means less condensation occurred on its surface compared to B. Statement B suggests 'The temperature inside bedroom A was higher than B', which would make window A's surface warmer and thus lead to less condensation (less fogging). Statement D, 'Water vapour outside bedroom B condensed faster than A', directly states that B experienced more rapid condensation than A, which aligns with A having less fogging in comparison to B. Statement C is incorrect as fogging is condensation, not evaporation. Statement A is less direct given the uniform surrounding temperature.

P5 Science SA1 2025 — Methodist Girls

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