Take a ball and ring apparatus as shown in figure. At room temperature, the ball can just pass through the ring. Now heat the ball over a flame and try to pass it through the ring. You will find that the ball when heated is not able to pass through the ring. The diameter of the ball increases when the ball is heated. This shows the expansion of solid on heating.
Concept: Expansion of Substances (Thermal Expansion) - Expansion of Solids