Reversible Irreversible processes


Reversible and irreversible processes are utilised in thermodynamics to illustrate the system behaviour. Often several chemical and physical happenings are going around people which are often not acknowledged. Some of the procedures cannot even be realised, with their existence often eluding the people. However, the procedures do happen and there is a distinction in the participant's state taking part in the procedures. For example, water boiling, ice melting, things burning and many more. One aspect is similar, that is the difference in nature. Heat or energy exchange is classified under reversible and irreversible processes.

What are reversible and irreversible processes?

A reversible process is demonstrated as the method in which the surroundings and system can be backed to the actual phenomenon from the final stage. This process undergoes without creating any alteration in the properties of thermodynamics of the universe if this procedure is reversed (Magnenet & Schmittbuhl, 2020).

The reversible process takes place in an infinite number of stages. The system of this process assists in attaining equilibrium at the last stage of every procedure. It is considered a thermodynamic process that leaves from equilibrium.

Figure 1: Graph for reversible and irreversible processes

Irreversible processes are demonstrated as the ones in which the environment and system cannot return collaboratively to the exact phase they were in. The irreversibility of the natural process results from thermodynamics’ second law. The flowing of electric current through the conductor with the resistance is referred to as an instance of an irreversible process (Jones, Lautens & McGlacken, 2019).

Irreversible processes possess an irreversible reaction. An irreversible reaction is a reaction that moves forward in a single direction where the products do not mix collaboratively to recreate the reactants. The fuel is a mixture of butane and propane as the fuel in Bunsen burner goes through Combustion.

The second law of thermodynamics

The thermodynamics’ second law helps in representing the results of irreversible processes. As opined by Bekenstein (2020), the law signifies that energy is transformed or transferred. It helps in illustrating the connection between heat or thermal energy and the way energy impacts matter. The second law basically relies on the nature of energy and states that nothing can change from the initial stage. Thermodynamics' second law also demonstrates that there is a probability of the natural tendency of an isolated process to regenerate in a more disorganised state (Gabizon et al. 2020). Irreversible processes ideally follow the second law of thermodynamics in physics which is the most interesting law among the other four laws of thermodynamics.

Types of an irreversible and reversible process

The reversible process generally possesses two types which include internal and external reversible processes.

  • The internally reversible process: Includes no irreversibility within the boundaries of the system. This system mentions that the method goes through the equilibrium stage when it returns; it again alters to a similar stage.

  • External reversible processes : Do not have any irreversibility. For instance, reservoirs and systems can be considered in this factor.

Irreversible processes have external physical factors such as resistance, friction, viscosity, the difference in finite temperature, surface tension and many more. There are no such changes in the internal type of irreversible processes.

Factors behind irreversibility of a process

The process of irreversibility is affected by several factors which lead to the resultant consequences of the process. The friction that is responsible for the conversion of the fuel energy into heat energy adds up to an irreversible process(mpei, 2022). Fluids when expanded without any restriction prevent them from gaining back their original form of heat transfer under a finite amount of temperature.

This inhibits the reversal of the process and in this case, the forward process involved is spontaneous. The mix of two different substances that are not possible to separate because the process of intermixing in this process is spontaneous as well. Therefore the factors of the reversible and irreversible process depend upon the factor of the ability of the substance to return to its original form.

Figure 2: Irreversible process and friction

Provide examples of reversible and irreversible processes

There are various examples out there to exhibit the functionalities of reversible and irreversible processes of work. One of the prime examples of reversible processes involves the slow and steady expansion and compression of fluids which stretches and contracts uniformly throughout the process (Opentextbc, 2022). Extension of springs and electrolysis are also examples of a reversible process. The irreversible process involves various other functions; for example, the relative motion associated with the friction, the effect of throttling, transfer of heat, fission and the flow of electricity through a resistance

Figure 3: reversible and irreversible process


Reversible and irreversible processes affect most of the functions in the daily course of life. In the first case, the object that undergoes certain change retains the ability to transform back to its original shape. However that is not the case with the irreversible process, in this process, the state of the transformed object does not go back to its original form. The flowing electricity through resistance is associated with an irreversible process while the frictionless motion of solids is an example of a reversible process.


Q1. What is a reversible process?

Ans. The process can be defined as a reversible process if both the object and the surroundings involved in the process can return to their original shape. This is a thermodynamic process.

Q2. What is an irreversible process?

Ans. The irreversible process is a process in which neither the system nor the surrounding can return to its original shape nor form once the process of transformation is initiated. In the case of an automobile engine, once the fuel burns and transforms into smoke and heat. It cannot retain back the lost energy nor can it go back to its original shape.

Q3. What are some of the examples of the reversible process?

Ans. Extension of the springs, a slow adiabatic and isothermal expansion and compression of gases are some examples of a reversible process. The process of electrolysis without the presence of resistance in electrolytes is also an example.

Q4. What are some of the examples of irreversible processes?

Ans. The motion relative to the associated friction and transferring of heat are examples of irreversible processes. The process of diffusion is also irreversible.


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