Standard Science Primary 4 Energy

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

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

Worked Solution

Step 1: Metal is a good conductor and expands when heated. Step 2: Gaining heat from the water caused the lid to increase in size slightly. Step 3: This loosened the grip on the jar.

Correct answer: The metal lid gained heat and expanded.

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