Which statement best defines evaporation?

Which statement best defines evaporation?

• A. Absorption of energy with a change from liquid to gas or vapor state
• B. Transition from gas to liquid with heat loss
• C. Change from solid to liquid at a constant temperature
• D. Release of energy without a phase change

Answer: (A)

Evaporation is the process where a liquid absorbs energy and changes into a gas. Molecules at the surface gain enough energy to overcome the liquid’s cohesive forces and escape into the air. This energy input makes the process endothermic, and it can happen at any temperature below the boiling point, not just at a full boil. The energy required for this phase change is the latent heat of vaporization. The best definition among the options is the absorption of energy with a change from liquid to gas because it accurately describes both the direction of energy transfer (energy in) and the phase change (liquid to gas). The other descriptions refer to different phenomena: gas to liquid with heat loss is condensation, a liquid to solid change at constant temperature is freezing or solidification (not evaporation), and releasing energy without a phase change does not describe evaporation.

Evaporation is the process where a liquid absorbs energy and changes into a gas. Molecules at the surface gain enough energy to overcome the liquid’s cohesive forces and escape into the air. This energy input makes the process endothermic, and it can happen at any temperature below the boiling point, not just at a full boil. The energy required for this phase change is the latent heat of vaporization.

The best definition among the options is the absorption of energy with a change from liquid to gas because it accurately describes both the direction of energy transfer (energy in) and the phase change (liquid to gas).

The other descriptions refer to different phenomena: gas to liquid with heat loss is condensation, a liquid to solid change at constant temperature is freezing or solidification (not evaporation), and releasing energy without a phase change does not describe evaporation.