**Entropy** (S) is a state function (thermodynamic quantity). Entropy is used to describe the course of a process. A process can be spontaneous or non-spontaneous. The Second Law of Thermodynamics states that the entropy of an isolated system never decreases. Any system will, if left, will proceed towards thermodynamic equilibrium. The thermal equilibrium is a state which has maximum entropy.

## What Is The Relationship Between The Second Law Of Thermodynamics And Entropy

Entropy (S) is defined as a measure of ‘unavailable energy’ in a closed thermodynamic system. Entropy is also defined as a measure of the system’s disorder or uncertainty of a system. Low Entropy means that more is the energy of a system available to convert to useful work. The least energy that is available to convert to useful work is at a point when the system is at thermal equilibrium.

## What is Entropy?

Entropy is:

- Measure of amount of heat unavailable to do work
- Measure of the disorder of a system
- Measure of the multiplicity of a system

Entropy of universe is ever-increasing! Nature tends to move from order to disorder in isolated systems.

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