Question

why do solids expand when heated?​

Answer 1

All three states of matter (solid, liquid and gas) expand when heated. The atoms themselves do not expand, but the volume they take up does. When a solid is heated, its atoms vibrate faster about their fixed points. The relative increase in the size of solids when heated is therefore small.

Answer 2

Explanation:

the particles of solid vibrate about their mean position . When we heat the solid , the particles start vibrating at a larger amplitude . This results in the particles moving apart from the neighbouring particles. This causes an increase in volume of solid and it expands.

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