Prince. An initial answer. You have to think of how you are going to increase the pressure of a gas. I can think of two methods …..imagine a gas in a Coke tin. The gas particles ar rapidly moving around, bouncing of each other and the sides of the container. We can increase the pressure by (1) decreasing the volume of the coke can ….the particles therefore will hit the sides more often (increasing pressure) or (2) increasing the amount of gas in the can which again increases the number of gas particles that hit the side of the can, again increasing pressure. In both these cases the intermolecular forces are quite small. Most gas particles are fairly inert , they have inter molecular forces but they are slight. Water (H2O) and NH3 (ammonia) are probably exceptional. HOWEVER as you increase the pressure further the gas molecules have less room to move and they get closer to each other …the intermolecular forces increase UNTIL they are so strong, because there are so many molecules in the small space that the gas becomes a LIQUID. This is helped if you reduce the temperature at the same time (molecular movement is temperature dependant).
Sorry a big explanation …will tidy up in due course.