When the liquid is at or above saturation temperature, what process occurs?

• A. Boiling
• B. Condensation
• C. Freezing
• D. Evaporation without boiling

Answer: (A)

Boiling happens when a liquid is at or above its saturation temperature for the given pressure. The saturation temperature is where the liquid’s vapor pressure equals the surrounding pressure, so the liquid can start to transform into vapor. When heat is added at this point, it goes into latent heat of vaporization rather than raising the temperature, and bubbles form throughout the liquid as it vaporizes—this is boiling. By contrast, evaporation occurs for temperatures below that point and mainly at the surface, condensation is vapor turning into liquid when vapor cools or is compressed, and freezing is the transition to a solid when the temperature drops enough.