Reversible and Irreversible Processes

In our daily lives, we witness several changes like water boiling, iron rusting, Ice melting, Paper burning, etc. Every human activity takes place in an environment, which may be natural or artificial. From his earliest history, man has attempted to study the phenomenon around him. He first attempts to understand and describe the basic laws which govern natural phenomena.

We can see that the system in question moves from an initial state to a final state in which it absorbs some heat from the environment and performs some work W on the environment in all of these phases.

How many of these systems can the system and its surroundings be returned to their previous state? We may conclude from common examples such as rusting and fermentation that it is not achievable in the great majority of circumstances. In this section, we will look at reversible and irreversible processes.

 What are Reversible Processes?

Reversible processes occur when a system returns to its original state after being disturbed. A classic example of this is the water cycle. A classic example is melting ice and vice versa. Water is originally in liquid condition, then freezes to produce ice, which melts again to give water when heated.

Students should be aware that a reversible process involves two processes. While in the first phase, participants change into another form, the reverse reaction occurs in this second process, with the results returning to the beginning stage.

As a result, comprehending this will aid in further diving into the distinction between reversible and irreversible processes. A process of reversibility set on elements, including non-elasticity, friction, viscosity, electrical resistance, and magnetic resistance, also called hysteresis.

For example, we can quickly push back the piston when the ideal gas expands in a vacuum or double its initial volume and restore its temperature and pressure by extracting some gas’s heat.

What are Irreversible Processes, and how do they work?

Irreversible processes cannot be reversed or at least cannot be reversed without the great expense of time and money. Irreversible processes are controlled by economic considerations (costs), and these considerations usually eliminate one or more variables in the balanced equation. This is because if any of the variables were eliminated, it would destroy the balance of the reaction, and the system would be unable to sustain itself.

For example, in an oil refinery plant where crude oil is converted into valuable products such as gasoline, kerosene, etc., many steps take place as each stage in the process consumes certain portions of the crude oil and turns out certain by-products. Each step in this process can never be reversed because if any one of these steps were eliminated, it would destroy the balance of the reaction.

Another example, consider the situation of a car engine that has traveled a particular distance while using a specific amount of fuel. The fuel burns to provide energy to the engine, producing smoke and heat energy in the process. We will never be able to regain the energy that the fuel has lost, nor will we ever be able to restore it to its former state and thus destroy what is called “economy.”

As a result, depending on their ability to return to their original form from their final state, specific processes are reversible while others are irreversible. Relative motion with friction, Heat transfer throttling, Diffusion Irreversible processes include the flow of electricity across a resistance.

Practically every situation is an example of an irreversible process since both the system and its nature cannot be restored to their initial states simultaneously. Because it is considered a natural phenomenon, the small gradient between the states in the natural process indicates that the process is irreversible.

When heat travels from one substance to another, the temperature difference between the two is finite. More importantly, at no point during the process is the system likely to be in equilibrium or a well-defined state. This is known as irreversibility.

Difference between reversible Process & irreversible process 

1. A reversible process is a process that can be obtained into the initial state of the system whereas, an Irreversible process is a thermodynamic process that cannot be reversed to obtain the initial state of a system.
2. Reversible can be reversed and were as Irreversible process cannot be reversed.
3. In reversible process infinite change occurs in the system, and in the case of the Irreversible process, finite changes occur in the system.
4. There is an equilibrium between the initial state and the system’s final state. However, in an irreversible process, there is no equilibrium in the system.

Thermodynamic Processes: Reversible and Irreversible

Thermodynamic processes can be further classified as either reversible or irreversible. In a reversible process, the system changing can go back to its original state after the process has been completed. Reversible processes occur in many everyday situations:

For example, you can walk on ice and melt it, but it will re-freeze after you have walked on it. The melting rate is slow compared to the rate at which the ice freezes. This is a reversible process.

The second law of thermodynamics

There are two equivalent statements of the second law of thermodynamics.

Kelvin Planck statement 

States that “It is impossible to create a heat engine that operates in cycles”; it means that it is impossible to convert “all” the heat extracted from a hot body into work.

Clausius statement

 states that “Heat never flows spontaneously from a colder object to a hotter object.” This means that it is impossible to transfer heat from a cold body to a hotter body; the term “spontaneously” means that no extra effort has been made

All feasible expressions of the second law of thermodynamics are equivalent, and they all result in containing a large number of molecules or particles.

Conclusion

There are two kinds of change, reversible and reversible. Things can go back to the original state after they are changed in reversible processes, and in irreversible processes, they do not. Irreversible change takes more energy than reversible processes because it is more complex. One of the significant features which separate a reversible process from an irreversible process is time. In irreversible processes, the rate of chemical reaction increases with time and may cause significant changes to several variables. In this lesson, we discuss the different ways to differentiate these two types of processes. As a student, you must understand the concept of thermodynamic processes like Reversible and Irreversible Processes, reversible processes in thermodynamics, and its other parts.