Which term describes the process by which a liquid becomes a gas at the surface and below boiling point?

• A. Hypothesis
• B. Boil
• C. Evaporation
• D. Melts

Answer: (C)

Evaporation is the process by which a liquid becomes a gas at the surface and below the boiling point. It happens when molecules at the surface gain enough energy to overcome the liquid’s intermolecular forces and escape into the air as vapor. This can occur at any temperature below the boiling point, which is why a puddle or wet surface gradually dries rather than boiling away all at once. Because the fastest surface molecules leave, the liquid cools as it evaporates. Evaporation is a surface phenomenon, unlike boiling, which involves rapid vapor formation throughout the liquid at its boiling point. The other terms don’t fit: a hypothesis is just a guess or proposed explanation; to boil means to vaporize at the boiling point with bubbling through the liquid; to melt is the change from solid to liquid.