Question

Explain physical significance of entropy

Answer 1

The entropy of a substance is real physical quantity and is a definite function of the state of the body like pressure, temperature, volume of internal energy.

It is difficult to form a tangible conception of this quantity because it can not be felt like temperature or pressure. We can, however, readily infer it from the following aspects:

 

1. Entropy and unavailable energy

The second law of thermodynamics tells us that whole amount of internal energy of any substance is not convertible into useful work. A portion of this energy which is used for doing useful work is called available energy. The remaining part of the energy which cannot be converted into useful work is called unavailable energy. Entropy is a measure of this unavailable energy. In fact, the entropy may be regarded as the unavailable energy per unit temperature.