The nature of heat

As mentioned in a previous chapter, heat can be thought of as the internal kinetic energy of the atoms and molecules that make up a substance. Being a form of energy, it is measured in the standard unit of Joule, but it is also commonly measured in the following units:

• calorie: this is the heat energy needed to raise 1 gm of water 1 ^oC. 1 calorie is equal to 4.186 Joules.
• Calorie: this is a common unit to measure the energy content of food, with 1 Calorie = 1000 calories.
• BTU: this is a British Thermal Unit, still used as a rating on some furnaces, and is the heat energy needed to raise 1 pound of water 1 ^oF. 1 BTU = 252 calories = 1,054 Joules.