During a race, an athlete sweats. As the sweat evaporates from the athlete's skin, their skin temperature decreases.
Which statement best explains, in terms of molecules, why evaporation causes this cooling effect?
The remaining liquid molecules expand and lose thermal energy to fill the space left by those that escaped.
Only the molecules with the highest kinetic energy escape from the surface, leaving behind molecules with a lower average kinetic energy.
The escaping molecules react with the air above the liquid, absorbing heat from the skin through a chemical reaction.
The molecules left in the liquid have more room to move around, which decreases their collision frequency and lowers 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.