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
The nature of heat
- 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.