OUTCOMES:
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Remember... Transfer of heat from one place to another by movement of a fluid is called convection. The moving fluid carries thermal energy with it.
Convection requires the movement of particles and so, convection only occurs within fluids (gases and liquids). The particles of a solid are in a fixed position and they cannot move. Therefore, convection cannot take place in a solid.
The circulation of warm and cold fluid due to convection is called a convection current. Here’s how a convection current works:
Cold fluid is warmed by the heat source.
Warm fluid rises. Warm fluid rises because it is less dense.
The warm fluid cools.
Cool fluid sinks. Cool fluid sinks because it is denser.
Cold fluid moves to replace the warm fluid that moved in the first place.
Demonstration:
Watch the demonstrations of convection currents in liquids.
Activity:
Based on what you saw in the demonstrations, colour and label the convection current diagram and stick in your exercise book.
Convection and Ocean Currents
Convection explains the movement of ocean water. Ocean currents are actually convection currents created by uneven heating of Earth’s ocean water.
Ocean water is warmed most by the sun at the Equator. The warm water moves to cold areas north and south. Cold water moves towards the equator to replace the water that moved north and south.
Demonstration:
Watch the demonstrations of convection currents in gases.
Activity:
Follow the demonstration to make and test a convection fan and explain how it works.
Extension:
This video explaining how to make a convection fan is in Gujarati, can you write and record an explanation that could be used by people who cant speak Gujarati so they know how to make the convection toy and can understand how and why it works?
Convection and Wind
Convection explains the movement of air or wind.
Like ocean water, air is heated unevenly by the sun.
Air on Earth’s surface is heated and rises into the atmosphere. It cools and sinks back down to the surface. This movement of air creates wind currents or wind cells around Earth.