Standard Science Primary 4 Energy

Rey found it difficult to open the metal lid of a glass jar. He dipped the lid into hot water for a minute and was then able to open it easily. Why?

A The metal lid expanded more than the glass jar.
B The hot water made the glass jar shrink.
C The glass jar expanded more than the metal lid.
D The hot water acted as a lubricant.
Show Worked Solution

Worked Solution

Step 1: Metal expands when heated. Step 2: Dipping the lid in hot water causes it to expand. Step 3: The lid becomes slightly larger than the jar opening, making it easier to twist off.

Correct answer: The metal lid expanded more than the glass jar.

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