Standard Science Primary 4 Energy

Jun Jie pumped air into a bicycle tyre until it was firm. He then left the bicycle under the hot sun for several hours. He noticed the tyre became even harder. Why?

A The rubber of the tyre expanded.
B The air inside the tyre gained heat and expanded.
C The sun added mass to the air inside the tyre.
D More air entered the tyre from the surroundings.
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Worked Solution

Step 1: Gases expand when they gain heat. Step [2-9]: The air inside the tyre gains heat from the sun and expands. Step [2-9]: Since the volume of the tyre is limited, the expanding air increases the internal pressure, making it harder.

Correct answer: The air inside the tyre gained heat and expanded.

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