Thermodynamic Equilibrium: Definition, Types [Notes with PDF]

In this segment, we will be studying Thermodynamic Equilibrium Definition and Types with example and in the end, you can download the whole document in PDF format.

So let’s dive to the topic,

The term “Thermodynamic” means it is a branch of physics that deals with the heat, work, and form of energy. The term “Equilibrium” means the state of balance of the system within itself and between the system and surrounding.

What is Thermodynamic Equilibrium?

The system is said to be thermodynamic equilibrium when there is no spontaneous change in any macroscopic property is observed, as the system is isolated from its surroundings is known as thermodynamic Equilibrium.

Types of Thermodynamic Equilibrium:

There is a total 3 thermodynamic equilibrium which are:

  • Chemical Equilibrium
  • Mechanical Equilibrium and
  • Thermal Equilibrium:

Chemical Equilibrium:

A system is said to be chemical equilibrium when no chemical reaction takes place in the system or between system and surrounding. The chemical composition will be the same throughout the system and this will not vary that system in chemical equilibrium. This is a reversible reaction.


CaCO→ CaO + CO

When we heat Calcium Carbonate (CaCO3 ) at temperature 1073K will get CaO and CO

Mechanical Equilibrium:

A system is said to be mechanical equilibrium when there is no unbalanced force within the system or between system and surroundings.

It deals with the force. The pressure in the system is the same at all points and does not change with respect to time.


Treadmill: This is a gym instrument on which we run but we don move forward because the force you trying to push forward the same force acting opposite to push backward. So this is one of the best examples of mechanical equilibrium.

Thermal Equilibrium:

A system is said to be thermal equilibrium when there is no temperature difference present and the temperature remains equal at all point.

Thermodynamic Equilibrium pdf
Thermal Equilibrium


A hot cup of tea has a higher temperature as compared to surrounding so this is not in thermal equilibrium.

But when you keep this in an open environment for some duration, the temperature starts emitting by radiation process to the environment and the surrounding temperature and a cup of tea temperature remains the same at that moment we can say this is in thermal equilibrium.

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Anup Kumar Dey

A Mechanical Engineer with 19 years of working experience in various renowned MNCs.

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