[Physics Class Notes] on Entropy Thermodynamic Pdf for Exam

Introduction to Entropy Thermodynamic

Students should understand the importance of entropy law as it is very helpful for studying physics. Entropy can be explained in numerous ways. The applications of entropy are useful in thermodynamic stages.  

In 1850, Rudolf, a German physicist, named its entropy. Entropy is a measurement of disorder or randomness found in a system. Many definitions are associated with entropy. In this article, we will know about two definitions of entropy, such as thermodynamic definition as well as statistical definition. 

Entropy Law and Thermodynamics

We will now understand the three laws associated with thermodynamics. 

• The first law of thermodynamics relating to entropy

• The second law of thermodynamics in terms of entropy

• The third law of thermodynamics in terms of entropy

1. First Law of Thermodynamics

This law states that heat is one type of energy that cannot be produced or neither be ruined. Well, thermodynamic processes are there that always consider a state i.e., conservation of energy.

However, heat can be transferred from one place to another, and this sort of energy is only convertible from one form to another. 

Some miscellaneous facts on the first law of thermodynamics

• We notice a surge of entropy when there is a change of state of the mater.

• Also, we encounter the rise of entropy when the number of moles of gaseous products rises more than reactants.

2. Second Law of Thermodynamics

Some specific points are there that can illustrate the entropy and second law of thermodynamics.

• Natural or spontaneous processes are irreversible in terms of thermodynamics.

• Entropy second law of thermodynamics states that the transfer of heat into work is not possible without wasting a certain amount of energy.

• The entropy level for the universe is surging continuously.

• 2nd law of thermodynamics entropy: ∆Stotal =∆Ssurroundings+∆Ssystem >0

The overall sum of the entropy of the system and the surrounding will be above zero.

3. Third Law of Thermodynamics

When the temperature of any solid crystalline has an absolute temperature, then the entropy will appear towards zero. This happens only due to a perfect order that exists in a crystal at absolute zero.

This law has a limitation that it is only applicable for the solid substances which do not have zero entropy at absolute zero such as glassy solid, solid containing a mixture of isotopes.

Entropy Statistical Mechanics

When you talk about the entropy of vaporization, the definition for it can be given as the upsurge of entropy due to the change of a liquid into vapours. 

This phenomenon is happening only due to the rise of molecular movement. This behaviour manifests randomness of motion.

The entropy of vaporization can be stated as the ratio of the enthalpy of vaporization and its boiling point. 

It can be represented as ∆vap S = ∆vap H / Tb 

Spontaneity

Chemical reactions that have Exothermic behaviour possess Spontaneity because ∆Ssurr is positive. This allows the value ∆Stotal to remain positive.

Some of the Endothermic reactions are spontaneous. 

It happens due to ∆Ssystem is positive only. Though ∆Ssurroundings is negative but complete ∆Stotal is positive.

The standards for the change in Free energy are always there for forecasting spontaneity. This concept is superior to entropy change criteria.

This is due to some important requirements that stand only for the free energy change of the system. However, some of the free energy also needs entropy change of both system and surroundings.

Do you know?

Entropy evolves numerous ideas when it comes to nature tending from order to disorder states. It means, the right-hand-side box of molecules existed before the left-side molecules

Conclusion 

Entropy is one of the thermodynamic properties that help us to measure the disorder of a system in detail. We can conclude that when we notice any heat transfer from higher to the lower temperature, the magnitude of entropy decreases. However, in the opposite case, the entropy value increases.