Two identical shallow dishes, each containing equal volumes of water, are left on a laboratory bench. Dish A is placed directly in front of an operating electric fan, while Dish B is sheltered behind a screen from any wind or drafts.
State and explain, in terms of water molecules, the difference in the times taken for the water to evaporate completely from the two dishes.
On another occasion, two identical wet kitchen towels are hung next to each other to dry. Towel X is spread out fully, while Towel Y is folded over multiple times.
State and explain, in terms of water molecules, the difference between the drying times of the two towels.
An athlete sweating during a workout feels a cooling effect as the sweat on their skin dries, even when the sweat is initially at the same temperature as their body.
Explain, in terms of a change of state of water, why the athlete feels cooler.
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.