Why can water evaporate without boiling?

• A. Because some water molecules at the surface have enough kinetic energy to escape into the gas phase even at temperatures below the boiling point.
• B. Because atmospheric pressure forces water molecules to leave the liquid phase.
• C. Because evaporation only occurs when water reaches its boiling point.
• D. Because water molecules lose energy and turn into vapor at any temperature.

Answer: (A)

Verified step by step guidance

1. Understand that evaporation is a surface phenomenon where molecules at the surface of a liquid can escape into the gas phase if they have enough kinetic energy.
2. Recognize that temperature is related to the average kinetic energy of molecules, but individual molecules have a range of energies described by the Maxwell-Boltzmann distribution.
3. Realize that even at temperatures below the boiling point, some molecules at the surface have sufficient kinetic energy to overcome intermolecular forces and evaporate.
4. Note that boiling occurs when the vapor pressure of the liquid equals the external atmospheric pressure, allowing bubbles of vapor to form throughout the liquid, which is different from evaporation happening only at the surface.
5. Conclude that evaporation can happen at any temperature because it depends on the kinetic energy distribution of surface molecules, not on reaching the boiling point.