HEAT CAPACITY

From our discussion of temperature and other processes from an atomic and molecular point of view, it is obvious that the way to raise the temperature of an object is to add energy. At higher temperatures the average thermal kinetic energy of the molecules increases, and that energy must come from somewhere. Historically the relationship between heat and energy was not so clear. As late as 1798, 71 years after Newton’s death, there were accepted theories that treated heat as a substance called caloric that flowed from hot substances to cooler ones.
It was Benjamin Thomson, later known as Count Rumford, who proposed that heat was, in fact, a form of energy. Rumford was boring cannons for Prince Maximilian of Bavaria, and was quite aware that when the drills were dull, the cannons became hot. Thomson proposed that the mechanical work he put into turning the drills was converted to heat energy that raised the temperature of the cannons. Forty years later, Joule accurately measured the amount of work required to raise the temperature of various substances.
Traditionally heat energy was defined as the amount of heat required to raise the temperature of one gram of water one degree centigrade. This unit of heat is called the calorie. In terms of mechanical energy, the conversion factor is
1 calorie = 4.186 joules (1)
This is the relationship between mechanical work and heat that Joule studied.