Standard Science Primary 4 Energy

Siti found it difficult to unscrew the metal lid of a glass jar. She placed only the metal lid in a bowl of hot water for a minute. After that, she could unscrew the lid easily. Why?

A The metal lid expanded.
B The glass jar contracted.
C The metal lid contracted.
D The glass jar expanded.
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Worked Solution

Step 1: Metal gains heat from the hot water. Step 2: When a material gains heat, it expands (increases in volume). Step 3: The expanded lid becomes looser on the jar, making it easier to unscrew.

Correct answer: The metal lid expanded.

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