Convection occurs in fluids, which includes gases and liquids. It cannot occur in solids. This is because convection depends on the movement of the entire substance, not just the molecules. The rule behind it all is quite simple: heat rises. When a liquid or gas warms up, the molecules move around more and the fluid expands (more on that soon). This causes the warm fluid to become less dense, so it rises. As the less dense warm fluid rises and the cooler, denser fluid sinks, a current is produced. This is called a convection current.An example of a convection current is seen when you heat a pot of water on a stove. The water nearest the flame or the burner heats up, rises, and is replaced by cooler water that falls toward the base of the pot. The moving water creates currents. If you were to add a small amount of dye to the water, you would be able to see the circular movements of the convection currents. The currents continue until all of the water is hot. Can you imagine how long it would take to heat a pot of water if we relied only on conduction for the heat transfer?
Convection
Where does convection occur?
Convection occurs in the air, in the waters and in the earth. It also occurs in everyday things like boiling water, opening a window or heating a room.
