Heat and Thermodynamics

Heat and Thermodynamics

Heat and Thermodynamics is the branch of science that deals with the amount of heat energy in a body, work, temperature and its relations with enthalpy, entropy etc.


Heat is a form of energy transferred from one body to another based on the temperature differences between the bodies. Every substance in the universe, whether macroscopic such as celestial objects or microscopic to the level of atoms and molecules, contains some heat energy. Absolute zero is the temperature with a value of 0 K. It is the temperature at which the body is devoid of heat energy. This is a hypothetical temperature, and it is not feasible thermodynamically. The field of heat and thermodynamics finds varied applications in our day-to-day life, such as regulating body temperature, refrigerators, air conditioners, etc.

What are Heat and Thermodynamics?

To understand the concepts of heat and thermodynamics; first, we need to familiarize ourselves with some basic concepts of heat and thermodynamics:

Heat: It is a form of energy that can be transferred from one body to another based on temperature differences.

Thermodynamic Work: The amount of work done in transferring heat between two bodies at different temperatures.

Temperature: The physical quantity that defines the degree of hotness.

Entropy: The state of the randomness of a body is known as its entropy.

Internal Energy: It is the total amount of energy that is stored in a body. The total amount of internal energy cannot be calculated, but only the change in internal energy can be calculated. 

Enthalpy:  It is the sum of a system’s internal energy multiplied by its pressure and volume. The equation can be shown as:


    Here,     H = Enthalpy

        E = internal energy

        P = Pressure

        V = volume

Gibbs free energy: The defined maximum amount of reversible work performed by a system at constant temperature and pressure. The equation for Gibbs free energy can be stated as:


Here,    G = Gibbs free energy (∆ refers to change)

    H = Enthalpy 

    T = Absolute temperature 

    S = Entropy 

Thus, thermodynamics is the study of heat and work regarding the various parameters we talked about in this particular section. After clearing these concepts, we are ready to understand the different laws of thermodynamics. 

Laws of Thermodynamics:Thermodynamics is composed of four universal laws and can be applied to anybody. They are:

Zeroth Law: This law states that if two systems are in thermal equilibrium with a third system, then those two bodies are also in thermal equilibrium with each other. The thermometer is an everyday instrument that uses the zeroth law of thermodynamics.

First Law: This is the law of conservation of energy. It tells us that the internal energy is the difference between the heat energy gained and the thermodynamic work done.


Second Law: the total entropy of an isolated system (the thermal energy per unit temperature that is unavailable for doing useful work) can never decrease.

Third Law: We discussed this law when we talked about absolute zero. It tells us that all processes stop as we approach absolute zero temperature and the system’s entropy is at its lowest.   

Hence these are the four laws of thermodynamics upon which this entire vast field of science has been built.

Practical Applications of Heat and Thermodynamics: The applications of heat and thermodynamics are very widespread in our daily life. Some of them can be mentioned as follows:

All vehicles that run on petrol and diesel engines are run via the Carnot cycle, a derivation of the laws of thermodynamics.

The various heat pumps such as refrigerators, air conditioners, coolers etc. are based on the laws of thermodynamics.

The field of heat transfer has been derived from the laws of thermodynamics. The concepts of conduction, convection and radiation are blessings of heat transfer.

Various types of power plants and renewable energy resources are based on the principles of thermodynamics.

Here we have seen the deep impact of heat and thermodynamics in our lives.


Heat and thermodynamics stand by themselves as a critical and complex field of physics and science in general. It has seen widespread use in automobiles, energy production, heat engines, and even medical sectors. Here we had a brief overview of the different types of terms associated with thermodynamics and learned a few equations of importance. We then examined the four critical laws of thermodynamics upon which this entire branch of science is built. Last but not least, we looked at the real-time applications of thermodynamics because, after all, science is meant to be utilized to make an individual’s life better.