When a gaseous substance changes into a liquid, the process is known as condensation. This phase transition occurs when the gas is cooled or compressed, causing the molecules to lose energy. As the temperature decreases, the kinetic energy of the gas molecules diminishes, leading them to come closer together, and eventually, the attractive forces between the molecules overcome their kinetic energy, resulting in the formation of a liquid.
Condensation can occur naturally, as seen in the formation of dew on grass or clouds in the atmosphere. It can also be induced artificially, such as when steam condenses into water when it comes into contact with a cooler surface.
If you have a specific gaseous substance in mind or a particular context for this transition, please provide more details!