Standard Science Primary 4 Energy

Jun Jie could not unscrew the metal lid of a glass jar. He inverted the jar and dipped ONLY the metal lid into a bowl of hot water for one minute. Why did this help him unscrew the lid?

A The metal lid contracted and became smaller.
B The hot water acted as a lubricant.
C The metal lid expanded and became larger.
D The glass jar expanded and became smaller.
Show Worked Solution

Worked Solution

Step 1: Metal is a good conductor of heat and expands when heated. Step 2: Hot water transfers heat to the lid. Step 3: The lid expands (gets bigger), making it looser on the jar.

Correct answer: The metal lid expanded and became larger.

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