1. COLLISION FREQUENCY
The number of collision which takes place in one second among the molecules present in one centimeter cube of the gas is called collision frequency.it is usually represented by Z.
Z=1/√2πνσ2n2
Thus Z is directly proportional to
1)average velocity of the gas molecules(v)
2)Square of the molecular diameter (σ2)
3)Square of the molecules per cm cube (n2)

2. THE MEAN FREE PATH but Nc=√2πνσ2n therefor l=v/ √2πνσ2n l=1/ √2πσ2n
Gas molecules encounter collisions with other gas molecules and with the walls of the container
Mean free path as the average distance between successive molecular collisions.
l=v/Nc
but Nc=√2πνσ2n
therefor l=v/ √2πνσ2n
l=1/ √2πσ2n

3. THE MEAN FREE PATH
Different free path of a molecule

4. IDEAL AND REAL GASES IDEAL GAS:-
A gas which obeys the gas equation (PV=nRT) under all condition of temperature and pressure is called an ideal gas.
The concept of ideal gas is only hypothetical.for example: hydrogen, oxygen, nitrogen
REAL GAS:-
A gas which obeys the gas laws fairly well under low pressure or high temperature.
The concept of real gases is real.for example: carbon dioxide,sulpur dioxide , ammonia

5. DEVIATION FROM THE GAS LAWS AND EXPLAINATION IN TERM OF COMPRESSIBILITY FACTOR AND BOYLE TEMPERATURE
The Effect of temperature and pressure on the behaviour of a gas may be studied in terms of a quantity ‘z’called compressibility factor which is defined as
z=PV/nRT

6. Effect of pressure : compressibility factor
Compressibility factor ,z is mathmatically expressed as
z=PV/nRT
In case of ideal gas,PV=nRT
z=1
In case of real gas,PV≠nRT
z≠1
Thus in case of real gases ,the value of z can be <1 or > 1.
When z<1, it indicates negtive deviation.
When z>1 ,it indicates positive deviation .it means gas is less compressible .

7. PLOT OF COMPRESSIBILITY FACTOR (z ) VS PRESSURE FOR SOME GASES

8. EFFECT OF TEMPERATURE:BOYLE TEMPERATURE
The deviation from ideal behaviour become less and less with increase in temperature.The temperature at which a real gas behave like an ideal gas is called boyle’s temperature. The boyle temperature is different for different gases.

9. PLOT OF COMPRESSIBILITY FACTOR z vs pressure FOR N2 AT DIFFERENT TEMPERATURE.
Ideal gas z
50⁰C
0⁰C
-50⁰C
P(Atmosphere)