Standard Science Primary 4 Energy

Ravi tried to open a glass jar but the metal lid was too tight. He poured hot water over the metal lid for a minute and was then able to unscrew it easily. Why?

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

Step 1: Metals expand when they gain heat. Step [2-9]: By pouring hot water, the metal lid expands, becoming slightly larger. Step [2-9]: This creates a gap between the lid and the glass, making it easier to unscrew.

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

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