Question

How does the kinetic energy of solids, liquids and gases compare?

Answer 1

Solids, liquids and gases are three possible physical states of a substance. They differ in the arrangement and the forces between the molecules. The molecules of every substance possess two types of energy; kinetic energy and potential energy. The motion of molecules gives rise to kinetic energy.

Complete solution:
The arrangement of molecules in solids, liquids and gases are very different from each other.
In solids, the molecules are very closely packed as the force of attraction or wander-vaal forces are very strong. There is hardly any space for the molecules to move around and hence the pressure is very high.

In liquids, the molecules are very close to each other but not as close as in solids. The wander-vaal forces are weaker and the molecules are able to flow easily.

In gases the molecules are far apart and the forces between them are almost negligible. The wander-vaal forces are weakest.

The kinetic energy of solids is the least as they cannot move about, they can only oscillate about their mean position. While the kinetic energy of liquids is more than the solids, its molecules undergo convection due to which they possess kinetic energy. The kinetic energy of molecules of gases is highest as they possess random motion and move at very high speeds randomly.

Therefore, gases have the highest kinetic energy, liquids have lower kinetic energy while the lowest kinetic energy is possessed by solids.

Note:
The kinetic energy of a substance increases with increase in temperature as their energy increases when heat is given. Solids are rigid and have definite shape while liquids and gases take the shape of the container. Liquids and gases exert pressure on the walls of the container due to the kinetic energy of their molecules.