ABSTRACT
Substances exist in the solid, liquid or gaseous state. Substances change state from solid to liquid to gas as the temperature rises. This is because the temperature is a measure of the average kinetic energy of the particles that make up the substance. As a solid is heated, it absorbs energy, which causes increased vibrations of the particles within it. Eventually, the kinetic energy of individual particles becomes so great as to overcome the inter-molecular forces holding the lattice together. During the phase changes the temperature remains constant even though heat is still being applied. This heat is used internally to overcome the attraction of the inter-molecular bonds. The specific latent heat of vaporisation is greater than that of fusion because more energy is required to overcome the intermolecular bonds here to liberate a gas. The latent heat is given out to the surroundings when condensation or freezing occurs.
