Question

Explain why a substance expands on heating.

Answer 1

When a substance is heated, its molecular movement increases. Due to this, the average distance between the molecules also increases, thereby increasing the volume of the substance, i.e., expanding the substance. However, the movement of molecules depends upon the state of matter. Solids have tightly packed molecules; hence, least movement of molecules takes place leading to minimal expansion. In liquids, the molecules are less tightly packed as compared to solids; hence, they expand more than solids. Molecules of gases have no bonding at all; therefore, gases expand the most.