Question

Why does a solid expand on heating?​

Answer 1

Explanation:

When heated the molecules present in the solid expand due to more vibrations within and in-between them. This is why solids expand on heating.

Answer 2

If a substance is heated its atoms and molecules vibrate faster and their kinetic energy increases. As the atoms vibrates faster the space between the atom increases. Due to this the atoms and molecules take up more space and causes increase in size in solids.