Plenary Questions

1. 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).

2. Convection currents can from when liquids and gases are heated. The cold fluid sinks and the hot fluid rises.

3. Energy can travel through empty space by infra-red rays, which can be reflected by mirros like light rays. Dull black surfaces are good radiators and good absorbers. Shiny, bright surfaces are poor radiators and poor absorbers.

4. A vacuum flask uses silvering to cut down heat transfer by radiation and uses a vacuum to cut down heat transfer by conduction and convection.