Question

"A substance expands on heating and contracts on cooling”. Justify this statement. [2 MARKS]

Answer 1

Effect of heat : 2 Marks

A substance expands on heating and contracts on cooling. When a substance is heated, the molecules absorb the energy and become excited. Due to this, the random motion inside increases and force of attraction between molecules decreases leading to larger spaces.

When a substance is cooled, it basically implies that the heat is taken away from the substance. This leads to lesser excited molecules and hence, lesser random motion. The force of attraction increases which leads to lesser spaces between molecules which leads to contraction.