Answers:
a) Thermal energy travels through the bottom of a pan by conduction. The energy is passed from one vibrating atom to the next. All metals are good conductors. Plastics, water and air are poor conductors (good insulators). b) Convection currents can form when liquids and gases are heated. The cold fluid sinks and the hot fluid rises. c) Energy can travel through empty space by radiation rays, which can be reflected by mirrors like light rays. Dull black surfaces are bad radiators and good absorbers. Shiny, bright surfaces are good radiators and bad absorbers. d) A vacuum flask uses silvering to cut down heat transfer by radiation and uses vacuum by conduction and convection. Plenary Questions 19 June 2011 16:20 PFY p.54 [cid:image001.jpg@01CC694E.4CBD9440]
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