Convection is a type of heat transfer that occurs
in molecules. It refers to the collective movement of molecules within fluids
and rheids (non-molten solids). Convection happens through the process of
diffusion, advection, or the combination of both. Therefore solids cannot
undergo this process because bulk current flows and significant diffusion
cannot take place within the molecules of solids. Aside from this, solids have
bigger molecules that are too compact and cannot move freely unlike fluids do.
Convection can best be seen through an experiment
when a glass of water is exposed to a heat source. The change in temperature in
the glass causes warm fluid to move into cooler areas which causes it to boil
and bubble.
