Researchers have established that coffee is best drunk at 60 ^{\circ}C. A designer has created a new cup intended to keep coffee at 60 ^{\circ}C. Figure 8.1 shows the cup. The labelled parts are: plastic lid, inner steel walls, shiny outer steel wall, vacuum, coffee, material Z. Material Z has a melting point of 60 ^{\circ}C. At room temperature, material Z is solid. Coffee at 90 ^{\circ}C is poured into the cup, and the coffee cools quickly to 60 ^{\circ}C.
(a)[1]
State the change that occurs to material Z when the hot coffee is poured into the cup.
(b)[5]
Explain how the cup’s features allow the coffee to stay at 60 ^{\circ}C for a long time. Include: plastic lid; vacuum; shiny outer steel wall; material Z.
Worked solution & mark scheme
This 6-mark question has a full step-by-step worked solution and mark scheme. One marking point: “material Z undergoes melting” …