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 heatThey 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.

Let’s try a worksheet

There’s one other way!

¡Uno mas!

Good video on infrared!

• http://www.youtube.com/watch?v=XPrVeks2OHI

Infrared radiation

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!

Cooling down!

Time (mins) Temp black can °C Temp shiny can °C

0

1

2

3

4

5

6

7

Etc.

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!

Let’s try a worksheet