Standard Science Primary 4 Energy

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

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

Worked Solution

Step 1: Heat causes solids to expand. Step [2-9]: Metals generally expand more and faster than glass when gaining heat. Step [2-9]: The expansion of the lid makes it looser on the jar.

Correct answer: The metal lid gained heat and expanded more than the jar.

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