All matter exists in one of three states. Solid, liquid or gas. As solids heat up they become liquid (melting) then turn into gas (evaporating). As gasses are cooled they become liquids (condensation) and then with more cooling, solids (freezing). Sound travels fastest in solids and slowest in gases. Each clip contains examples of different states or changes in state. When listening, try to work out what states are present. Are there any changes in state?