To make them gas, you have to give liquids heat energy.. Explanation:
In order to make liquids change into gaseous state, we need to add heat to the liquid substance. This is because heating the liquid will cause the molecules of a liquid to gain heat due to which they will collide rapidly with each other.
This will lead to move the molecules away from each other and then this will lead to a change in their phase.
For example, when we boil water then at a temperature of it starts to change into vapor phase.