Internal Energy

Key Stage 3

Meaning

Internal Energy is the total energy of all the particles in a material.

About Internal Energy

The particles in a material have kinetic energy because they move and several types of potential energy because they are affected by forces. Internal Energy is all of those energies added together.

Examples

Water can exist as a liquid and a gas at 100°C. The kinetic energy of the particles in both is the same. However, the particles in steam have more internal energy than the particles in water because they are spread apart, giving them more potential energy.

The particles in petrol at 50°C are moving around so they have kinetic energy. The petrol also has a store of chemical potential energy that can be released when petrol burns in the presence of Oxygen. So the Internal Energy of petrol includes both the kinetic energy of the particles and the chemical potential energy.