Thermodynamics in its totality is concerned about heat. The meaning of heat today is the energy in transit. Before the development of thermodynamic laws, heat was considered as the measure of an invisible fluid, caloric, present in any matter. The capability of a substance to hold this fluid was then referred to as the heat capacity of that substance. The development in thermodynamics and dependence of heat transfer on temperature changed the definition of heat. Modern thermodynamics defines heat as the measure of the total internal energy of a system. In order to quantify the heat energy associated with matter and its dependence on temperature, two properties were defined. These properties were named as specific heat capacity and heat capacity of the system.
Heat energy is the measure of total internal energy of a system. This includes the total kinetic energy of the system and the potential energy of the molecules. It has been seen that internal energy of a system can be changed by either supplying heat energy to it, or doing work on it. The internal energy of a system is found to increase with increase in temperature. This increase in internal energy depends on the temperature difference, the amount of matter, etc. Heat capacity is defined as the amount of heat energy required to raise the temperature of a given quantity of matter by one degree Celsius. Heat capacity for a given matter depends on its size or quantity and hence it is an extensive property. The unit of heat capacity is joule per Kelvin or joule per degree Celsius.
Where, Q is the heat energy required to bring about a temperature change of ΔT and C is heat capacity of the system under study.
Specific Heat Capacity
Scientists needed a quantity that has no dependence on the quantity or size of matter under consideration for thermodynamic studies this made them define specific heat capacity. It is an intensive property as it is independent of quantity or size of the matter. Specific heat capacity for any substance or matter can be defined as the amount of heat energy required to raise the temperature of unit mass of that substance by one degree Celsius. Mathematically it is given as:
Here Q is the amount of heat energy required to change the temperature of m (kg) of a substance by ΔT, s is the specific heat capacity of the system.
Thermodynamics continues to play a vital role in our lives directly or indirectly. Scientists and engineers use the laws of thermodynamics to design new processes for reactions that would have high efficiency and product yield. Chemical and mechanical engineers apply the concepts of thermodynamics for designing heat engines with high efficiency and better outputs. Join Byju’s for the most simplified approaches to your problems. Make learning simple.