Macroscopic approach

Microscopic approach

In this approach a certain quantity of matter is considered without taking into account the events occurring at molecular level . In other words this approach to thermodynamics is concerned with gross or all behaviour . This is known as classical thermodynamics

This approach is considers that the systems is made up of a very large numbers of the discrete particle known as molecules. These molecules have different velocities and energies . The values of these energies are constantly changing with time .

The analysis of macroscopic systems requires simple mathematical formulae

The behaviour of the system is found by using statistical method as the number of molecules is very large. So advanced statistical and mathematical methods are needed to wexplain the changes in the system

The values of the properties of system are their average values. For example consider a sample of a gas in a closed container . The pressure of the gas is the average value of the pressure exerted by millions of individual molecules .

The properties like velocity , momentum , impulse , kinetic energy , force of impact etc , which describe the molecule cannot be easily measured by instruments . Our senses cannot feel them .

In order to describe such a system only a few properties are needed .

Large number of variables are needed to describe such a system . So the approach is complicated .
