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The term specific heat may also refer to the ratio between the specific heat capacities of a substance at a given temperature and of a reference substance at a reference temperature, such as water at 15 °C; [5] much in the fashion of specific gravity. Specific heat capacity is also related to other intensive measures of heat capacity with ...
Replacing work with a change in volume gives = Since the process is isochoric, dV = 0, the previous equation now gives = Using the definition of specific heat capacity at constant volume, c v = (dQ/dT)/m, where m is the mass of the gas, we get =
Systems do not contain work, but can perform work, and likewise, in formal thermodynamics, systems do not contain heat, but can transfer heat. Informally, however, a difference in the energy of a system that occurs solely because of a difference in its temperature is commonly called heat , and the energy that flows across a boundary as a result ...
where is the specific heat capacity (at constant pressure, in case of a gas) and is the density (mass per unit volume) of the material. This derivation assumes that the material has constant mass density and heat capacity through space as well as time.
For a thermally perfect diatomic gas, the molar specific heat capacity at constant pressure (c p) is 7 / 2 R or 29.1006 J mol −1 deg −1. The molar heat capacity at constant volume (c v) is 5 / 2 R or 20.7862 J mol −1 deg −1. The ratio of the two heat capacities is 1.4. [4] The heat Q required to bring the gas from 300 to 600 K is
This relation was built on the reasoning that energy must be supplied to raise the temperature of the gas and for the gas to do work in a volume changing case. According to this relation, the difference between the specific heat capacities is the same as the universal gas constant. This relation is represented by the difference between Cp and Cv:
Thermodynamic work is one of the principal kinds of process by which a thermodynamic system can interact with and transfer energy to its surroundings. This results in externally measurable macroscopic forces on the system's surroundings, which can cause mechanical work, to lift a weight, for example, [1] or cause changes in electromagnetic, [2] [3] [4] or gravitational [5] variables.
For example, Paraffin has very large molecules and thus a high heat capacity per mole, but as a substance it does not have remarkable heat capacity in terms of volume, mass, or atom-mol (which is just 1.41 R per mole of atoms, or less than half of most solids, in terms of heat capacity per atom).