Convection
Another mode of heat transfer is convection, which involves the movement of liquids and gases. When cooking, how is heat spread out in a pot? Heat from the source is transferred to the pot by conduction. The water molecules at the bottom of the pot get hot before the rest of the pot does because they are closest to the source of heat. The heat makes the water molecules expand.
Increase in the volume of a molecule makes it become less dense. The hotter, less dense water molecules rise to the surface, while the colder and denser molecules sink to the bottom. This rising and sinking of the molecules form a circling motion known as convection current.
In your home, observe how, when someone is cooking in the kitchen, the air inside the room becomes heated. If the room has good ventilation, the heat inside the room transfers outside, therefore somehow cooling the room.
