Entropy in Thermodynamics

The relationship between entropy and different laws of thermodynamics is as follows:

First law of Thermodynamics and Entropy

• The first law of thermodynamics, which is a version of the law of conservation of energy, states that the total energy of an isolated system is constant; energy can be transformed from one form to another but can be neither created nor destroyed.

• Entropy, on the other hand, is a measure of the unavailable energy in a closed system and is not a conserved quantity.

• While the first law of thermodynamics deals with energy conservation, entropy is related to the quality of energy and the direction or outcome of spontaneous changes in a system.

• Therefore, the first law of thermodynamics and entropy are distinct concepts describing different thermodynamic systems.

Second Law of Thermodynamics and Entropy

• Second law of Thermodynamics and entropy are closely related. The second law of thermodynamics implies that the Universe’s entropy is continuously increasing, and any spontaneous process will increase the total entropy of the system and its surroundings.

• The relationship between the second law of thermodynamics and entropy is that the second law provides a quantitative measure of the direction of spontaneous processes. In contrast, entropy measures a system’s degree of disorder or randomness.

• For example, when a hot object is placed in contact with a cold object, heat flows spontaneously from the hot object to the cold object. This process increases the total entropy of the system and its surroundings as the energy becomes more dispersed and less available to do work.

• Another example is ice melting, a spontaneous process that increases the system’s entropy. The solid ice has a more ordered structure than the liquid water, and the melting process increases the degree of disorder or randomness in the system.

Third Law of Thermodynamics and Entropy

• Third law of thermodynamics states that the entropy of a system approaches a constant value as the temperature approaches absolute zero.

• The entropy of a system at absolute zero is typically zero, and in all cases, it is determined only by the number of different ground states it has.

• This law has two significant consequences: It defines the sign of the entropy of any substance at temperatures above absolute zero as positive, and it provides a fixed reference point that allows the absolute entropy of any substance to be measured.

Entropy means the amount of disorder or randomness of a system. It is a measure of thermal energy per unit of the system which is unavailable for doing work. The concept of entropy can be applied in various contexts and stages, including cosmology, economics, and thermodynamics. Entropy is a concept that essentially discusses the spontaneous changes that take place in ordinary phenomena or the Universe’s inclination towards disorder.

In this article, we will learn what is meaning of Entropy, the entropy change formula, and how it is associated with the laws of thermodynamics.