Internal energy
When a material is heated or cooled, two changes may happen to the particles within the material:
- Chemical The chemical link that holds molecules together. between the A general term for a small piece of matter. For example, protons, neutrons, electrons, atoms, ions or molecules. may form, break or stretch. There is a change in the chemical potential store of energy in the material.
- The material will heat up or cool down as the particles within it gain or lose speed. There is a change in the thermal store of energy within the material.
When energy is given to raise the A measure of the average kinetic energy of particles in a substance., particles speed up and they gain kinetic energy.
When the substance melts or boils, energy is put in to breaking the bonds that are holding particles together, which increases the potential energy.
The The principle that the total energy of a system stays the same, that energy cannot be created or destroyed (only stored or transferred). means that, assuming no energy is transferred to the environment, any energy transferred to a material will be distributed between the chemical store and the thermal store of the The total kinetic energy and potential energy of the particles in an object..
Whether the energy breaks bonds, increases the speed of the particles to stretch bonds, or just increases the speed of the particles depends on the temperature and Solid, liquid or gas. Evaporation is a change of state from liquid to gas. of the material.