Contents
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.
Key Stage 4
Meaning
Internal Energy is the sum of all kinetic and potential energies of particles in a system.
About Internal Energy
- The particles in a material have kinetic energy, because they move, and several types of potential energy because there are forces between adjacent particles.
- Forces of attraction, including chemical bonds, pull particles together. The further apart the particles the more potential energy they poses. As a result the gaseous state of a substance has more potential energy than the liquid state of that substance, even if the temperature of both is the same because the particles are spread apart in a gas and close together in a liquid.
Equation
Internal Energy = All kinetic energies + All potential energies