What happens to the energy of the liquid during evaporation?

• A. Energy of the liquid increases as high-energy molecules escape
• B. Energy of the liquid decreases as high-energy molecules escape
• C. The energy remains constant
• D. Evaporation adds energy to the liquid

Answer: (B)

When a liquid evaporates, energy is carried away by the escaping molecules. The molecules that escape are typically the ones with higher kinetic energy, so as they leave, the average energy of the remaining liquid drops. That loss of energy from the liquid is why evaporation feels like cooling—the vapor takes energy with it rather than adding energy to the liquid.

So the energy of the liquid decreases as high-energy molecules escape. Energy isn’t staying the same or increasing, and evaporation doesn’t add energy to the liquid.