When heat leaves a meterial, the material usually gets cooler (its temperature drops), and when heat enters a material, the material gets warmer (its temperature rises). When two bodies at different temperatures are placed near eachother, heat will always flow from the hotter body to the cooler body until both bodies are at the same temperature, which is a state called equilibrium. A unit often used to measure heat is the calorie. A calorie is the quantity of heat required to raise the temperature of 1 gram of water by 1ºC. This measurement, however, is not very accurate because the starting temperature of the water effects the amount of calories needed to heat the water 1ºC. The joule is the preferred unit of measurement for heat because a joule always represents the same amount of heat.