when a liquid is heated, the heat energy will accumulate in the particle. As a result, the particles of the liquid are able to move so faster that the intermolecutar force cannot hold them together, and make the particles move apart freely at high speed. This results in agradual rise in temperature as the liquid continues to be heated until it becomes constant. the temperature at which a liquid becomes a gas is called the boiling point. if the change it is called evaporation.