An athlete cools down after a race as sweat evaporates from their skin. Which molecules escape from the sweat and what happens to the average speed of the sweat molecules that remain on the skin?
the more energetic ones escape, and the average speed decreases
the more energetic ones escape, and the average speed increases
the less energetic ones escape, and the average speed decreases
the less energetic ones escape, and the average speed increases
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.