what is the effect of change of Pressure

We have learnt that the states of matter can be changed into another by changing the temperature, Pressure is another factor which can also change the state of matter.  

Example:- gases can be

changed into liquids by increasing the pressure or by decreasing the temperature. Similarly, some solids, like solid CO, or dry ice can be changed into gases on decreasing the pressure.

Actually, the states of matter depends upon

inter-particle spaces and inter-particle forces of attraction.All Gases have large interparticle spaces and weakest inter-particle force of attraction. Liquids

have comparatively lesser inter-particle spaces and larger inter-particle force of attraction than gases while the solids have strongest inter-particle force of attraction and smallest inter-particle spaces. Thus,

to convert a gas into liquid or to convert a liquid into solid, the inter-particle spaces must be decreased and inter-particle forces of attraction must be made

stronger.

On increasing pressure the particles of substance come closer to each other, as a result the inter-particle

space decreases. As inter-particle force of attraction is inverse of inter-particle spaces therefore, inter- particle spaces decreases as inter-particle force of attraction increases. This leads to a change in the

physical state of matter.

In order to understand the effect of pressure let us perform an experiment:

Take a gas in a cylinder and apply pressure on it by piston as shown.