Standard Science Primary 4 Energy

Jun Jie found it difficult to open a metal lid on a glass jar. He poured hot water over the metal lid and was able to open it easily. Why?

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

Worked Solution

Step 1: Pouring hot water causes the metal lid to gain heat. Step 2: Most materials expand when they gain heat. Step 3: The lid expands and becomes looser on the jar.

Correct answer: The metal lid gained heat and expanded.

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