Fig. 3.1 shows a hot water tank fitted with two electric heaters X and Y. Heater X operates in the daytime, whereas heater Y is used only at night, when electricity is cheaper.
(a(i))[3]
Explain the process responsible for the temperature rise of the water above X.
(a(ii))[2]
Heater Y is left off. Explain why the temperature of the water below heater X rises far more slowly than the temperature of the water above heater X.
(b)[2]
The hot water tank is wrapped in a thick insulating layer. The insulating layer is made of a plastic containing many tiny pockets of trapped air. Explain why this material is a good insulator.
Worked solution & mark scheme
This 7-mark question has a full step-by-step worked solution and mark scheme. One marking point: “When heated, water expands or its molecules move further apart” …