Conduction and Convection
DIAGRAMS (click to englarge)
Heat transfer - Conduction
MEMO BOX - remember these!
LIQUIDS AND GASES EXPAND WHEN THEY ARE HEATED.
HEAT ENERGY MOVES FROM HOT PLACES TO COLDER PLACES.
Here's a picture to make everything a bit clearer.
Heat energy can be transferred through objects by conduction and convection. Radiation (infrared) is another mehtod is which heat it transferred but it is different for two reasons: radiation involves PARTICLES and radiation involves ELECTROMAGNETIC waves. Conduction and convection need particles in order to transfer heat energy.
Before you have the slightest understanding of what convection is you must first understand what a fluid is. A fluid is anything that flows. LIQUIDS and GASES fall under this category. Now we've established that, you must know that convection is a method by which heat is transferred through liquids ad gases (fluids).
Heat energy in convection moves from hot places to COLDER places.
Liquid and gas particles move faster when they are heated. This means fluids expand. When they expand, it makes sense that these particles take up more volume. But remember, the size of the particle is the same but the gap between the particles is widened.
Fluids in hot areas are less dense than fluids in colder areas. We mentioned that convection currents move from hot places to colder places right? Taking this into account, the fluids in HOT areas rise as they are less dense and have enough heat energy to rise. However, once they rise to cooler areas they cool down so they become more dense and therefore sink. The process goes on, and on, and on, and on ... yeah.
Here is another EUREKA video. Just make sure you refer to convection rather than buoyancy.