An athlete finishes a long run on a warm, breezy afternoon and notices they feel chilly as their sweat evaporates. Why does the evaporation of sweat cause a cooling effect on their skin?
The less energetic water molecules escape quickly, leaving behind warmer liquid.
The more energetic water molecules escape into the air, decreasing the average kinetic energy of the remaining liquid.
The sweat acts as an insulator, preventing warm air from reaching the skin.
The breeze causes the sweat molecules to stop moving, lowering their temperature.
528 exam-style questions on CIE IGCSE Physics 2.2 Thermal properties and temperature, covering 2.2.1 Thermal expansion of solids, liquids and gases, 2.2.2a Internal energy and temperature, 2.2.2b Specific heat capacity, 2.2.3a Melting, boiling, condensation and solidification, 2.2.3b Evaporation, and 2.2.3c Cooling by evaporation. Each one has a worked solution and a mark scheme showing where the marks go.