* Energy and Phase Changes: When a gas changes to a liquid (condensation), the gas molecules slow down and come closer together. This means they release energy into the surroundings.

* Breaking vs. Forming Bonds: To break the bonds holding gas molecules apart requires energy (endothermic), but forming the weaker bonds between liquid molecules releases energy (exothermic).

* Heat Transfer: You can feel this energy release if you've ever held a cold can of soda – the condensation on the can is the result of the air condensing into liquid droplets, releasing heat.

In summary: The transition from gas to liquid involves a decrease in energy, meaning the process is exothermic.