Standard Science Primary 4 Energy

Siti found it difficult to open a glass jar with a metal lid. She poured hot water over the metal lid and was then able to open it easily. Why?

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

Worked Solution

Step 1: Metal is a good conductor of heat. Step 2: When hot water is poured, the lid gains heat and expands. Step 3: Expansion makes the lid slightly larger than the jar opening, making it easier to unscrew.

Correct answer: The metal lid gained heat and expanded.

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