Where does heat transfer by convection

-- One example of heat transfer by convection is inside a teapot.  Normally,
warm water rises up and cold water sinks down. That's why we put the fire
under the pot and heat the bottom water.

-- Another example is a glass of soda with ice in it.  Normally, warm water
rises up and cold water sinks down. That's why it's such a great accident
that ice happens to float on top of water. That way, it can cool the warm
soda that rises to the top, and once the soda around it gets cold, that soda
sinks to the bottom, and more warm soda rises to where the ice is.