Heat loss through the evaporation of perspiration from the skin is best described as which mechanism?

• A. Evaporation
• B. Radiation
• C. Conduction
• D. Convection

Answer: (A)

Heat loss through sweating occurs via evaporative cooling: when sweat on the skin changes from liquid to vapor, it absorbs the energy needed for that phase change from the body, taking heat away and cooling the skin. This latent heat of vaporization is drawn from the body's surface, making evaporation a distinct mechanism from other forms of heat transfer.

Radiation would be heat lost as infrared energy without a phase change, conduction requires direct contact to pass energy through a material, and convection involves heat carried away by moving air or fluid. Evaporation specifically uses energy to convert a liquid on the skin to vapor, which is why it’s the best description for heat loss from perspiration.