Question

2. One of the pots is filled with soup. The soup at the bottom of the pot is warmed by the stove burner, but how does the soup at the top get hot?

Answer 1

Convection. Hot water is less dense than cold water (at least above 4C), so when the water at the bottom of the pot is heated it becomes less dense, and then floats up to the top. Meanwhile, colder water streams down to replace it. Vertical currents, called convection currents, are thereby established which quickly distribute the heat throughout the pot.

Incidentally, the very same process is responsible for plate tectonics -- the slow movement of the large plates that make up the Earth's crust, which result in movement of the continents, formation and destruction of continents and oceans, the uplift of many mountain ranges, include the Himalayas and Andes, and the "Ring of Fire" string of volcanos and earthquakes zones around the Pacific.

In that case, the heat from the Earth's core, partly residual from its formation, and partly from the decay of radioactive elements like uranium and thorium, heats the liquid and semi-liquid rock in the Earth's mantle over it. The heated rock is less dense and floats upward, and cooler rock flows down to take its place. You get huge slow currents that push and pull the crust plates lying on top of the mantle. Here's a nice Wikipedia article on that:

http://en.wikipedia.org/wiki/Mantle_convection

Answer 2

convection