Question

Explain why a solid expands when it is heated ?

Answer 1

Hint: The molecules of a solid possess some thermal energy at a given temperature due to which the molecules of the solid vibrate. When the temperature is increased, the thermal energy of the molecules increase due to which the amplitude of the vibrations increase.

Complete answer:
Let us first understand what a solid is. A solid is a state of a material in which the structure of the material is rigid. A solid does not flow and the molecules remain compact in the volume of the solid.A solid is a material in which the forces of attraction between the molecules of the material are maximum such that they remain rigid at a given temperature.

However, the molecules or the atoms of a solid are never stationary and oscillate about their mean position. This is because the molecules possess some thermal energy.The amplitude of vibrations of the molecules depend on the thermal energy. And the thermal energy depends on the temperature of the solid. Higher the temperature, higher is the thermal energy of each molecule and thus greater is the amplitude of the vibrations.

Therefore, when we heat the solid, its temperature increases, which increases the thermal energy of the molecules. As a result, the amplitude of vibrations increases. When the amplitude of vibrations increase the mean spacing between the molecules also increases. As a result, the solid expands.

Note: The difference between temperature and heat. Heat is the exchange of energy between two bodies at different temperatures. It is the energy given to a colder body from a hotter body. Temperature is a measurement of the hotness or coldness of a body.