Standard Science Primary 4 Energy

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

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

Worked Solution

Step 1: Metal is a better conductor of heat than glass and expands faster. Step 2: Heating the lid causes it to expand (get slightly larger). Step 3: This makes the fit looser, allowing it to be unscrewed.

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

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