Physics 5054 · O Level · Transfer of thermal energy
Transfer of thermal energy — practice question
Fig. 3.1 depicts a laboratory freezer. Its door is shut and the freezer is on. A cold liquid is pumped along the copper pipe at the top of the freezer. The air beside the copper pipe cools rapidly.
(a)[3]
Explain why the temperature of the air elsewhere in the freezer falls.
(b(i))[2]
The thick insulation shown in Fig. 3.1 is made from a plastic material. This plastic is a poor thermal conductor. Describe how thermal energy is transferred through a plastic material.
(b(ii))[3]
The plastic material also contains a large number of small air bubbles. Explain how the air bubbles reduce the transfer of thermal energy through the insulation.
Worked solution & mark scheme
This 8-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Air beside the pipe contracts / its volume decreases and density rises” …