Which process occurs when surface particles of a liquid gain energy and become gas?

• A. Condensation
• B. Sublimation
• C. Evaporation
• D. Deposition

Answer: (C)

Evaporation is the process where surface particles of a liquid gain enough energy to break free and become gas. At the surface, some molecules already have higher kinetic energy. If they gain enough energy to overcome the attractive forces holding them in the liquid, they escape into the air as vapor. This happens at temperatures below the liquid’s boiling point and mainly involves the surface, not the bulk of the liquid. The rate increases with higher temperature, a larger surface area, stronger air flow, and lower ambient humidity because those conditions help remove the vapor and allow more molecules to escape. The other options describe different phase changes: condensation is vapor turning into liquid when energy is lost; sublimation is solid turning directly into gas; deposition is gas turning directly into solid. The described surface-escape into gas is evaporation.