# Convection

#### Definition: What is convection?

Convection is the transfer of heat by motions in a liquid or gas.

Boiling water. Note what happens to the nucleation of bubbles when different objects are introduced into the boiling water. Two objects are introduced - a pin and a stirring stick.

Video source: Eugenia Etkina, Rutgers University

### Applications

1. Boiling water, exploding oatmeal or spaghetti sauce, operation of a "convection" oven
2. Rising and resulting formation of clouds
3. Vertical overturn of water in lakes and oceans
4. Vertical overturn of rock and molten rock within the Earth

### Engagement, etc.

1. Miso soup convection
2. Man Who Rode the Thunder
3. German Christmas pyramids
5. Convection ovens
6. Roof turbine vents

### Questions for thought

1. If you hold a hot potato in your hand, your hand becomes warm on the inside. Have any of the atoms of that potato moved into your hand? Did convection occur?

### Conceptual flow

1. Convection of one of the core ways in which energy can be transferred from one place to another. It is a universal behavior of matter.
2. In addition to convection, conduction and radiation are the other ways in which energy can be transferred from one place to another.
3. In convection, matter carries energy within it moves. In conduction matter doesn't move very much, and in radiation matter is involved.
4. What is energy?
5. What makes convection start?
6. Convection is triggered by density differences that occur as a result of temperature differences. Other kinds of motion are triggered by spatial differences in addition to density, temperature, gravity, and pressure.
7. Convection of water comes to a boil at a specific temperature when bubbles form. How does the convection of rock and molten rock differ from the case of water in a pot?

### Other definitions - note differences

1. "the movement of matter due to differences in density that are caused by temperature variations; can results in the transfer of energy as heat."
From adopted textbook - Earth Science - California Edition, Holt, 2007.
2. "transfer of heat within a liquid or gas"
From classroomn textook - Glossary, Concepts and Challenges: Earth Science Fourth Edition, Globe Fearon, 2003.
3. "Heat is energy that flows between a system and its environment by virtue of a temprature difference that exists between them."
- Halliday and Resnick, Fundamentals of Physics Third Edition.
© 2007-2008 Earthguide at Scripps Institution of Oceanography.