Standard Science Primary 4 Energy

Siti found it difficult to unscrew the metal lid of a glass jar. She placed the lid under hot running water for a minute and was then able to unscrew it easily. Why?

A The metal lid expanded more than the glass jar.
B The hot water acted as a lubricant.
C The metal lid expanded while the glass jar did not.
D The glass jar expanded more than the metal lid.
Show Worked Solution

Worked Solution

Step 1: Metal is a better conductor of heat than glass and expands faster. Step 2: Hot water causes the metal lid to gain heat and expand. Step 3: As the lid expands, it becomes looser around the jar neck.

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

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