Thermodynamics is a branch of science that deals with the concept of heat and temperature and the inter-conversion of heat and other forms of energy. It mainly deal with the transformation of heat into mechanical work and vice versa.

(I) Thermodynamic System

An assembly of a very large number of particles having a certain value of pressure, volume and temperature is called a thermodynamic system.

(II) Surroundings

Every outside the system which can have a direct effect on the system is called its surroundings.

(III) Thermodynamic Variables

The quantities like pressure (P), volume (V), and temperature (T) which help us to study the behaviour of a thermodynamic system are called thermodynamic variable.

(IV) Equation Of State

The mathematical relation between the pressure(P), volume(V) and temperature(T) of a thermodynamic system is called its equation of state.

The equation of state for n moles of a ideal gas can be written as PV = nRT.

Classification Of Thermodynamic System

(I) Open System

It exchanges both energy and matter, with its surroundings.

(II) Closed System

It exchanges only energy (not matter) with its surroundings.

(III) Isolated System

It exchanges neither energy nor matter with its surroundings.

Adiabatic Wall

A wall that not allows energy flow of heat from one to another is called adiabatic wall.

Diathermic Wall

A wall that allows energy flow or heat from one to another is called diathermic wall.

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