HVAC 403A Practice Exam

Evaporation is the process of turning a liquid into vapor when heat is added. As heat increases, the molecules at the liquid’s surface gain enough energy to overcome intermolecular forces and escape into the air as gas. This can occur at temperatures below the liquid’s boiling point and is driven by energy input and surface area. In HVAC, evaporation is key in cooling because the refrigerant absorbs heat as it boils into vapor inside the evaporator. The other options describe condensation (vapor turning into liquid by cooling) or freezing (liquid becoming a solid), which are different phase-change processes.