What is the process in which the molecules of a heated liquid evaporate?

What is the process in which the molecules of a heated liquid evaporate?

• A. Evaporating
• B. Freezing
• C. Boiling
• D. Condensing

Answer: (C)

The process in which molecules of a heated liquid evaporate is known as boiling. Boiling occurs when a liquid reaches a specific temperature at which its vapor pressure equals the surrounding atmospheric pressure, allowing bubbles of vapor to form within the liquid. This is distinct from evaporation, which is a surface phenomenon occurring at any temperature and involves only the molecules at the surface escaping into the gas phase.

During boiling, the heat provided to the liquid increases the energy of the molecules, causing them to move faster and, eventually, transition into the gas phase throughout the entire body of the liquid, rather than just at the surface.

In contrast, freezing refers to the process of a liquid turning into a solid, and condensing describes the transition of a gas back into a liquid. These processes do not involve the evaporation of a heated liquid but rather are the result of temperature and energy changes in the opposite direction. Therefore, boiling accurately describes the behavior of heated liquids as they change into vapor.