4 05
Ice cream is made by cooling a mixture of liquid ingredients until they freeze.
Figure 6 shows a bowl used for making ice cream
The walls of the bowl contain a liquid coolant.
The bowl is cooled to -20 °C before the mixture is put in the bowl.
The bowl causes the mixture to cool down and freeze.
Figure 6
Inner metal surface
Liquid
coolant
-20 °C
Outer
plastic
surface
Mixture
0 5.3 Explain why the different thermal conductivities of metal and plastic are important in
the design of the bowl.
[4 marks)