Which of the following best explains why water evaporates at room temperature?

• A. Some water molecules have enough kinetic energy to overcome intermolecular forces and escape into the gas phase.
• B. Evaporation occurs only when water is heated to its boiling point.
• C. Water evaporates because air molecules push liquid water into the gas phase.
• D. Water molecules lose energy and condense into vapor.

Answer: (A)

Verified step by step guidance

1. Understand that evaporation is the process where molecules transition from the liquid phase to the gas phase at temperatures below the boiling point.
2. Recognize that in a liquid, molecules have a range of kinetic energies due to their thermal motion; some molecules move faster than others.
3. Identify that evaporation occurs when individual water molecules at the surface gain enough kinetic energy to overcome the intermolecular forces (like hydrogen bonding) holding them in the liquid.
4. Note that this process does not require the entire liquid to reach the boiling point; it happens continuously at room temperature as higher-energy molecules escape.
5. Conclude that the correct explanation is that some water molecules have enough kinetic energy to overcome intermolecular forces and escape into the gas phase, leading to evaporation.