How does heat transfer through convection work?

Convection is transfer of energy through movement of liquid particles. Let us take some steps back and revise a number of principles. First of all, you should remember the concept of density. If two parts of a liquid have different densities, the less dense part will rise above the denser region (if the student does not understand this point, I would then remind them of the definition of density and how it applies to different material). Second of all, you should also remember that as a material is heated, it will expand; in other words, its volume will increase. Lastly, if you remember the equation for density (d = mass / volume), you can conclude that when the volume of a material increases, its density decreases.Now let us go over what happens in convection. Imagine a kettle full of water being heated on a stove. As the bottom of the kettle is heated, the bottom region of water is heated up. This cases the volume of this region to increase. This increase in volume, cases the density of the bottom region of water to decrease and as a result, it rises above the denser and colder water molecules. This process carries on with cold water replacing warmer water at the bottom of the kettle, resulting in transfer of thermal energy to colder regions of water.