In thermodynamics, heat capacity is a value specific for each body defined as the ratio of the quantity of heat δQ exchanged by the system with the surroundings to the observed temperature change dT: [1]

History
The modern view of heat as energy in transit was preceded by the idea that a body has a "capacity" for heat. The smaller the temperature change in a body caused by the transfer of a given quantity of heat, the greater its capacity. [2] Most of this work was initiated by Scottish chemist Joseph Black and French chemist Antoine Lavoisier in the 18th century. [3] The first clearly stated definition of heat capacity, together with the first table of specific heat values, however, was published in 1780 by J.M. de Magellan, based on data supplied by Richard Kirwan. [4]

Measurements
Heat capacities are typically measured constant volume (isochoric) or constant pressure (isobaric) conditions:

and

Subsequently, heat capacities at constant volume can be measured by the partial derivative of internal energy U with respect to temperature and heat capacities at constant pressure can be measured by the partial derivative of enthalpy H with respect to temperature. Once these values have been determined via experiment, the calculation of the amount of heat Q released or absorbed by a body can be calculated by the following expression:

where n is the number of particles in the system and ΔT is the temperature change.

References
1. Perrot, Pierre. (1998). A to Z of Thermodynamics (pgs. 139-41). Oxford University Press.
2. Smith, J.M. Van Ness, H.C., and Abbott, M.M. (2005). Introduction to Chemical Engineering Thermodynamics (2.11: Heat Capacity, pgs. 40-44). McGraw-Hill Book Co. Inc.
3. Thomson, Thomas. (1840). An Outline of the Sciences of Heat and Electricity (pg. 54). H. Bailliere.
4. (a) de Magellan, J.H. (1780). “Essai sur law Nouvelle Theorie du Feu Elementaire, et de la Chaleur des Corps.” London.
(b) Fenby, David V. (1987). “Heat: Its measurement from Galileo to Lavoisier.” Pure & Appl. Chem., 59: 91-100.
(c) Salje, Ekhard K.H. (1988). Physical Properties and Thermodynamics Behavior of Minerals (pg. 433). Springer.

External links
● Specific heat capacity – Wikipedia.
● Heat capacity – Eric Weisstein’s World of Physics.