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Do now!. Can you continue the CONVECTION worksheet you started last lesson?. Today’s lesson. Describe experiments to demonstrate the properties of good and bad conductors of heat Explain heat transfer in solids in terms of molecular motion
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Do now! Can you continue the CONVECTION worksheet you started last lesson?
Today’s lesson • Describe experiments to demonstrate the properties of good and bad conductors of heat • Explain heat transfer in solids in terms of molecular motion • Recognise radiation as a method of heat transfer that does not require a medium to travel through • Identify infra-red radiation
Thermal energy transfer Can you quickly and quietly gather around Mr Porter?
Heat can travel by Conduction Hot particles vibrate more, so collide with adjacent particles. The heat energy travels from hot to cooler areas. hot cold
Heat can travel by Conduction Metals are good conductors of heat Why?
Heat can travel by Conduction Metals are good conductors of heat They have free electrons that can move from atom to atom carrying thermal energy too
Heat can travel by Conduction Most gases are poor conductors of heat (insulators) Why?
Heat can travel by Conduction Gases are poor conductors of heat (insulators) The atoms are too far apart for the vibrations to be passed easily.
There’s one other way! ¡Uno mas!
Good video on infrared! • http://www.youtube.com/watch?v=XPrVeks2OHI
Infrared radiation Heat can travel by infrared radiation (“Hot light”!)
Infrared radiation Infrared radiation can travel through a vacuum (and through air)
Infrared radiation Black objects are good absorbers of infrared radiation.
Infrared radiation Shiny objects reflect infrared radiation. Nottingham Forest winning the champions league in 1979
Infrared radiation Which would cool fastest? 100°C 100°C Shiny!
Let’s try! 1. Carefully fill two flasks with boiling water. 2. Take their temperature every minute.
Infrared radiation Black objects are good EMITTERS of IR radiation 100°C 100°C Shiny!