Difference Between Specific Heat Capacity and Heat Capacity

Specific Heat Capacity vs Heat Capacity

Heat capacity and specific heat capacity are two very important concepts in the field of thermodynamics. These concepts play a vital role in most of the applications in thermodynamics. This article will present the differences and similarities between these two concepts.

What is Heat Capacity?

Heat capacity is an extremely important characteristic of matter. Heat capacity is a measurable thermal property. It is defined as the amount of thermal energy required to increase the temperature of a substance by a given temperature. In SI unit system, the heat capacity is defined as the amount of heat required to increase the temperature of a sample by 1 Kelvin. The units of the heat capacity are Joules per Kelvin. The heat capacity of a sample depends on the substances in the sample, their bonding structure and the mass of each substance. The heat capacity of an object is extremely important, because it can be used to measure the amount of heat absorbed or emitted by the object using the temperature change of the object.

The heat capacity of earth’s atmosphere is considered as infinity with respect to the heat exchanges in lab conditions. Therefore, the environment is considered as an infinite heat sink in such processes. However, with large heat generation process such as heat coming from the sun, the earth’s atmosphere cannot be considered as an infinite heat sink. For processes involving gasses, there are two types of heat capacities specially defined. First one is the constant volume heat capacity, and this is the heat capacity measured when the process is done in a constant volume. Since no expansion is possible, the gas cannot do any work on the exterior. Therefore, the total energy input causes a temperature rise. The second type is the constant pressure heat capacity. In this case, the gas can do work on the environment. Since the expansion means doing work, the total heat supplied is not going to raise the temperature.

What is Specific Heat Capacity?

Specific heat capacity is defined as the amount of thermal energy required to raise the temperature of a 1 kilogram object by 1 Kelvin. The units of specific heat capacity are Joule per Kelvin per kilogram. The specific heat capacity of a pure substance is a constant. If the composition of an object is known, specific heat capacity can be easily calculated by adding up the heat capacities of certain substances multiplied by the corresponding proportion. The specific heat capacity of an object is independent of the mass of the object. It can be also taken as the heat capacity of the object divided by the mass of the object.