Heat capacity

Heat capacity or thermal capacity is the ability of an object to store heat. It is abbreviated to C_th, and its SI units are J/K (joule per kelvin). The concept is further discussed in the article on temperature.

Heat capacity is related to thermal capacitance by the formula

where

V = volume (m³)

ρ = density (kg/m³)

c_p = specific heat (J/kgK) at constant pressure

The product ρc_p is known as thermal capacitance or (confusingly) thermal capacity, and has units of J/m³K. Dulong and Petit predicted in 1818 that ρc_p would be constant for all solids (the Dulong-Petit law). In fact, the quantity varies from about 1.2 to 4.5 J/m³K. For fluids it is in the range 1.3 to 1.9, and for gases it is a constant 0.001 J/m³K.