Which phenomenon relies on evaporative cooling?

• A. Boiling water
• B. Condensation on a cold surface
• C. Sublimation of dry ice
• D. Sweating

Answer: (D)

Evaporative cooling happens when a liquid at a surface absorbs enough energy to change into a gas, pulling heat from that surface as the liquid evaporates. Sweating fits this perfectly: as sweat on the skin evaporates, it takes heat from your body with it, cooling the skin and helping regulate temperature. The energy needed to transform the water into vapor (latent heat of vaporization) comes from your body, so your skin and surroundings get cooler.

Boiling water also involves evaporation, but it’s driven by adding heat to the liquid, not by cooling a surface in everyday conditions. Condensation on a cold surface is the opposite process—gas turns into liquid and tends to release heat to the surface, warming it rather than cooling. Sublimation of dry ice absorbs heat as a solid becomes gas, so it can cool the surroundings, but it’s a solid-to-gas change, not liquid-to-gas evaporation on the skin. Sweating is the classic, direct example of evaporative cooling as a mechanism for cooling the body.