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## What is Thermodynamics?

The thermodynamic is that branch of Engineering – Science which deals with the energies possessed by gases and vapors. It also includes the conversion of these energies in terms of heat and mechanical work and their relationship with properties of the system.

## Objective Type Questions

### Q.1 Define Thermodynamic System ?

A definite area or a space where some thermodynamic process takes place is known as thermodynamic system.

### Q.2 Explain the following terms

1. 1. Open System
2. 2. Closed System
3. 3. Isolated System

:- Open System :- An open system is one in which both the heat and work as well as mass of the working substance crosses the boundary of the system.For example: A reaction taking place in an open vessel exchanges both energy and matter with the surrounding.

:- Closed System :- A closed system is one in which heat and work crosses the boundary of the system but the mass of the working substances does not crosses the boundary of the system.For example: A reaction taking place in a closed metallic vessel.

:- Isolated System :- In an isolated system, neither the heat and work nor the mass of the working substance crosses the boundary of the system. For example: Water placed in a vessel that is closed as well as insulated.

### Q.3 Explain the Laws of Thermodynamics?

Zeroth Laws of Thermodynamics :- Zeroth laws of thermodynamic states that when two bodies are in thermal equilibrium with third body then they are also thermal equilibrium with each other.

First Laws of Thermodynamics :- First law of thermodynamic states that energy can neither be created nor be destroyed but it can be transform from one form to another form.

Second Law of Thermodynamics:- This law states that “all processes in nature tend to occur with an increase in entropy and the direction of change always lead to the increase in entropy.”

This law states that there is a definite limit to the amount of mechanical energy, which can be obtained from a given quantity of heat energy.

or

Second Laws of Thermodynamics has two statements:-

According to Claussius, this law may be stated as “It is impossible for a self acting machine working on cyclic process, to transfer heat from a body at a lower temperature to a body at a higher temperature without the aid of an external agency”

The second law of thermodynamics has also been stated by Kelvin-Planck as “It is impossible to construct an engine working on a cyclic process, whose sole purpose is to convert heat energy to work.” According to this statement, the second law of thermodynamics is sometimes called as law of degradation of energy.

Third Law of Thermodynamics:- The value of entropy of a completely pure crystalline substance is zero at absolute zero temperature.

## Q.4 State The Third Law Of Thermodynamics. Give Its Limitations And Importance.?

Third Law of Thermodynamics States That : –

“The entropy of a perfect crystal of each element and a compound is zero at absolute zero.”

Limitations: If any disorder like impurity or imperfection is found in a substance then the entropy of such crystal is non-zero at 0 K. For example: The entropy of pure carbon dioxide and nitric oxide is zero at 0K. This shows that there exists disorder in the arrangement of such molecules.

This law is applicable only to pure compounds. Thus we can say that, this law is not applicable to glass which is a supercooled liquid. It is also not applicable to amorphous substance and supercooled solutions.

Importance:

• With the help of this law Thermodynamic properties can be calculated and chemical affinity can be measured.
• This law helps in explaining the behaviour of solids at very low temperature.

### Q.5 Define the following terms?

1. 1. Extensive Properties:- The properties of the system, whose value for the entire system is equal to the sum of their values for the individual parts of the system, are called extensive properties. For example, total volume, total mass, & total energy.
2. 2. Intensive Properties:- The properties of the system, whose value for entire system is not equal to the sum of their values for the individual parts of the system, are called intensive properties. For example, temperature, pressure, & density.

### Q.6 When A Real Gas Behaves Like Ideal Gas?

A real gas behaves like a ideal gas at low pressure and high temperature condition.

### Q.7 State the law of Conservation of Energy?

According to law of conservation, “Energy can neither be created nor be destroyed but it can be transformed from one form to another form.”

### Q.8 What is Carnot Engine?

It was being designed by Carnot and let me tell you that Carnot engine is an imaginary engine which follows the Carnot cycle and provides 100% efficiency.

### Q.9 Which Has More Efficiency Diesel Engine Or Petrol Engines?

Diesel Engine is more efficient than Petrol Engine.

### Q.10 Define perfect gas?

The state of substance whose evaporation from its liquid state is complete, is known as perfect gas.