Question

What is the definition of entropy?

Answer 1

Entropy:

1. It is a measure of the degree of randomness and disorder of the system.
2. For an isolated system, the entropy is high due to the high disorder.

The following is a detailed description:

1. The increase in the entropy is due to the randomness increase in the product as compared to the reactant.
2. When the uniformity of structure decreases then the entropy is increasing. For example, solid material has low entropy as compared to gaseous material.
3. Parameters which affect the entropy: heat and temperature.
4. Heat: The increase in the disorder is caused by the applied heat to the system.
5. Temperature: The heat applied at a lower temperature creates more randomness as compared to the same heat applied at a higher temperature.
6. The relationship of change in entropy ($∆\mathrm{S}$), heat (${\mathrm{q}}_{\mathrm{rev}}$), and temperature ($\mathrm{T}$) is that the entropy is inversely proportional to the temperature:$∆\mathrm{S}=\frac{{\mathrm{q}}_{\mathrm{rev}}}{\mathrm{T}}$
7. The total change in enthalpy for the system and surrounding for the spontaneous reaction is: $∆{\mathrm{S}}_{\mathrm{total}}=∆{\mathrm{S}}_{\mathrm{system}}+∆{\mathrm{S}}_{\mathrm{surrounding}}>0$.
8. The entropy and change in entropy are zero at the equilibrium position.
9. The change in internal energy ($∆\mathrm{U}$) is zero for the reversible and irreversible expansion of gas but $∆{\mathrm{S}}_{\mathrm{total}}$ is not zero for the irreversible process.