What term describes the condition where liquids can change into vapor or vapor into liquid?

• A. Condensation
• B. Saturation
• C. Boiling
• D. Freezing

Answer: (B)

Saturation is the condition where liquid and its vapor are in equilibrium at a given pressure. At this point, both phases can exist together, so liquid can continuously vaporize into vapor and vapor can condense back into liquid. The temperature and pressure lie on the saturation line, which marks the boundary between all-liquid and all-vapor states; crossing away from it leads to either subcooled liquid or superheated vapor.

Boiling is the process of vaporization occurring when heat is added at or above the boiling point, forming vapor bubbles within the liquid. Condensation is the process where vapor becomes liquid. Freezing is liquid turning into a solid. In the context of the question, saturation best describes the state where the two phases are in balance and can interchange.