1. Natural Sciences Grade 7
Term 3: Energy and Change
Heat transfer

2. Natural Sciences - Grade 7
Topic 3 Heat transfer
Convection
Natural Sciences - Grade 7

3. Natural Sciences - Grade 7
Convection images
Natural Sciences - Grade 7

4. Natural Sciences - Grade 7
Convection [part 1]
Convection is the transfer of heat from one place to another by the movement of gas / liquid particles.
Fluids are substances that do not have a fixed shape, which means that gases and liquids are fluids.
Convection currents can occur in gases [e.g. air] and in liquids [e.g. water].
4. Convection only occurs through convection
currents.
Natural Sciences - Grade 7

5. Natural Sciences - Grade 7
Convection [part 2]
As soon as air is heated, it expands and the particles move upwards.
Convection currents occur as soon as the air particles move up and down.
7. The fluid’s cooler part becomes heavier and it sinks which results in heat moving around in a gas / liquid.
Natural Sciences - Grade 7

6. Natural Sciences - Grade 7
Convection [part 3]
Look at the pot on the stove:
Convection in a pot of water that is being warmed.
Fluids – substances that contain particles that can move around quite freely.
Convection current – circular movement of fluids caused by convection.
Natural Sciences - Grade 7