Answer: By decrease of temperature and increase of pressure
Explanation: Gas is the state of matter in which particles are very loosely bound and hence can easily move past one another very easily as the inter molecular forces are weakest.
Liquid is the state of matter in which particles are tightly bound as compared to gases as they have strong inter molecular forces as compared to gas.
Thus for converting gas to liquid, the molecules have to brought closer which can be done by decrease of temperature or increase of pressure.
Decrease in temperature decreases the kinetic energy and hence the random movement will be restricted. Increase in pressure will bring the molecules close. Thus converting gas to liquid.
