Which phase transition is an example of an exothermic process?

In the context of phase transitions, an exothermic process is one that releases heat to the surroundings. Condensation, which is the process where a substance changes from a gas to a liquid, is indeed an exothermic process. During condensation, gas molecules lose energy and come closer together to form a liquid. This release of energy is what is referred to as the exothermic nature of the transition.

In contrast, phase transitions like melting, vaporization, and sublimation require the absorption of heat. Melting involves the transition from solid to liquid, vaporization involves the transition from liquid to gas, and sublimation is the direct transition from solid to gas. All of these processes require energy input to overcome intermolecular forces and phase boundaries, resulting in heat being absorbed rather than released. Therefore, the correct identification of condensation as an exothermic process highlights the key principle that during this phase change, heat is expelled, making it an essential concept in thermodynamics and phase behavior of substances.