Convection & Radiation

Science: KS3, topic 3.2.29

Convection and Radiation

Two other methods of heat transfer are convection and raditation.

Examples of convection include flying a hot air balloon and a radiator heating your bedroom.
Sea breezes are also examples of convection currents. During the day the breeze will often go from the sea to the land and in the evening the breeze will often blow in the opposite direction.
Heat always moves from hot to cold.

You can see convection currents in liquids if you put a small amount of potassium permanganate in a water and gently heat one corner. The potassium permanganate is coloured and you can see it move around the tank.
A mobile above a Bunsen burner will spin because the heat from the Bunsen will transfer energy to the air particles above the heat source
These particles will move more, expand and so become less dense. The less dense air will rise above the denser air. The gap formed is replaced by cooler air. This spins the mobile.

Heat can be transferred by radiation (infrared radiation)
Infrared radiation is part of the electromagnetic spectrum
No particles are needed unlike convection or conduction
Radiation can travel through a vacuum
It takes around 8 minutes for infrared radiation to leave the sun to reach the Earth’s surface
The distance from the Earth to the sun is 1 Astronomical Unit (150 million km)

Convection is one of the three methods of heat transfer.
You can demonstrate convection currents in air using a mobile hung above a Bunsen burner.
Which statement is true about radiation?
Why does purple dye from potassium permanganate spread around a tank of water after one corner is gently heated?