The heat capacity of an object is a measure of how well the object stores heat. Whenever we supply heat to an object, it will necessarily cause an increase in the object's temperature. The heat capacity is defined as the amount of heat required per unit increase in temperature. The heat capacity is defined as a proportionality constant (C) between the heat added to the object and the change in temperature that results:

Q = C(T_f –T_i)

In which T_i and T_f are the initial and final temperatures of an object.

Material with large heat capacities, like water, hold heat well - their temperature do not substantially rise for a given amount of heat - whereas materials with small heat capacities, like copper, don't hold heat well - their temperature will rise significantly when heat is added.

Heat capacity is not widely used because every system would have a different C even if it were made of the same substance. For example, a 100g of pure water and 50g of pure water would each have a different total heat capacity. The heat capacity C is useful for composite systems composed of different substances like a mixture of a fixed amount of water and copper.

A more common concept is specific heat capacity, or simply specific heat, which is the heat energy required to increase the temperature of one gram of a substance by one degree Celsius. Thus, the specific heat of an object is a measure of how well an object absorbs heat. The term “specific” means the measure is a bulk property, and thus is a characteristic of a particular substance. The units of specific heat are Joule/gram•°C.