Two identical shallow dishes are filled with equal volumes of water and placed in the same room. One dish is placed directly in front of an operating electric fan, while the second dish is placed in a draught-free corner of the room.
State and explain, in terms of water molecules, the difference between the times taken for the water in the two dishes to evaporate completely.
Two identical wet towels contain the same amount of water. One towel is spread out flat on a drying rack, while the other towel is crumpled tightly into a ball and placed on the rack.
State and explain, in terms of water molecules, the difference between the drying times of the two towels.
After running a marathon on a warm day, a competitor sprays water over their skin to cool down. Even though the water is at the same temperature as the surrounding warm air, the runner feels cooler.
Explain, in terms of a change of state of water, why the runner 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.