TRG-TRC003-EN 3
period one
Heat and Refrigeration
notes
These two different masses of water contain the same quantity of heat, yet the
temperature of the water on the left is higher. Why? The water on the left
contains more heat per unit of mass than the water on the right. In other words,
the heat energy within the water on the left is more concentrated, or intense,
resulting in the higher temperature. Note that the temperature of a substance
does not reveal the quantity of heat that it contains.
In the English system of units, the quantity of heat is measured in terms of the
British Thermal Unit (Btu). The Btu is defined as the quantity of heat energy
required to raise the temperature of 1 lb of water by 1°F.
Similarly, in the metric system of units, the quantity of heat is measured in
terms of the kilocalorie (kilogram-calorie or kcal). The kcal is defined as the
amount of heat energy required to raise the temperature of 1 kg of water 1°C.
Alternatively, in the Systeme International (SI) metric system, heat quantity can
be expressed using the unit kiloJoule (kJ). One kcal is equal to 4.19 kJ.
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