Why does warm water rise in a pot?
Water warmed near the bottom of a cooking pot can become less dense than the cooler water above. Buoyancy makes it rise, setting up circulation that carries heat.
- The scientific idea
- Convection
- Fields of science
- Physics
How it works
Water warmed near the bottom of a cooking pot can become less dense than the cooler water above it. Under gravity, the warmer region rises and cooler water moves into its place. The resulting circulation carries energy through the pot.
Look closer
This is different from conduction through the metal base: in convection, the material itself travels. Both processes can operate at once. Air behaves as a fluid too, so similar circulation helps distribute heat around a room. The phrase 'heat rises' leaves out the mechanism. Warm fluid can rise because of buoyancy; heat itself can also travel sideways or downward by other routes, including conduction and radiation.