There are two different kettles. The bodies of the kettles are made from different materials. Kettle A is made from shiny silver-coloured metal. Kettle B is made from white plastic. Discuss the suitability of each material in reducing heat losses from the kettles when they are used to boil water.
GCE O-level 5116 Science (Physics) 2009 November Paper 2 Question 10(a)
Answer: Both shiny surfaces (Kettle A) and white surfaces (Kettle B) are poor emitters of thermal radiation and so they help to reduce the thermal energy loss through radiation from the surfaces of the kettles to the surroundings. However, plastic surfaces (Kettle B) are poorer thermal conductors than metal surfaces (Kettle A) and so plastic surfaces are less effective than metal surfaces in transferring thermal energy, which is then lost through radiation, through conduction from the contents of the kettle to the surface of the kettle. Hence, the surface of Kettle B is more suitable in reducing heat loss when it is used to boil water.
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