Standard Science Primary 4 Energy

Siti observed that the metal lid of a glass jar was too tight to open. She dipped the lid into hot water and it opened easily. Why?

A The hot water acted as a lubricant.
B The glass jar lost heat and contracted.
C The metal lid gained heat and expanded.
D The air inside the jar expanded.
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Worked Solution

Step 1: Metal is a good conductor of heat. Step 2: When the lid is dipped in hot water, it gains heat. Step 3: Materials expand when they gain heat, making the lid slightly larger and easier to unscrew.

Correct answer: The metal lid gained heat and expanded.

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