Now, while I do apply a bit of physics in my cooking, such as knowing that a denser concoction will take more time to heat through than something looser, I certainly don't pay as much attention to it as this author. He's describing the various physics that is involved in cooking, such at the various types of heat transfer.
A stove's burner supplies energy to a pan via conduction - i.e. two surfaces in contact. But here I'm more interested in what's happening inside the pan.
The bottom of the pan is made hot. So liquid at the bottom gets hot enough that it begins to evaporate, forming small bubbles.
When the bubbles get large enough, they peel off the bottom of the pan. Being less dense than the liquid around them, the bubbles float to the surface.
Finally, and less noticeably, some liquid at the surface is cooler than its surroundings, so it in turn sinks. This process is what we call convection.
Yeah, but Hamburger Helper???!! :)