Convection Current

As noted previously, convection occurs in liquids and gases because these states of matter have free moving molecules. It will only occur when the temperatures in the area are different as well.

Boiling Water (convection current: liquids)

We boil water on a stove to make tea or to boil an egg. When water is heated its molecules increase in temperature and begins to move around more rapidly. The molecules are charged up and produce kinetic energy.

The hot water molecules near the heat source (the fire) become less dense and rise above the cooler denser molecules.

As the hotter molecules rise they cool down and then begin to sink to replace the cooler molecules which have just been heated up. The movements which occur in the boiling water are what we term as convection currents.

This process occurs in a continuous cycle until all the water is relatively hot or warm.

Image of convection in boiling water

IMPORTANT FACTS

Convection currents help in producing rainfall (convectional rainfall). When warm air and cool air meet, the warmer air rises higher into the atmosphere. If this air contains a significant amount of water vapour the water will cool and then drop back down as rain.