SO HOW IS HEAT TRANSFERRED? 3 Methods: Conduction Convection Radiation
1 ST ENERGY TRANSFER SCENARIO… You are making Mac & Cheese on the stove. You leave a metal spoon in the pot for a few minutes while you leave the room. You come back to stir the Mac & Cheese and grab the spoon… What happens?
CONDUCTION!!! Conduction - Heat transferred from one particle of matter to another without the movement of the matter. The hot pot’s fast moving particles collide with the slow moving particles of the cooler spoon. As the particles move faster, the spoon becomes hotter!
2 ND ENERGY TRANSFER SCENARIO… More cooking! You have a pot of water on the stove. What is happening to the water? What is the motion of the water?
CONVECTION!!! Convection - Heat is transferred by the movements of current within a gas or liquid. The heated water from the bottom of the pot rises to the top. Cooler water at the top sinks to the bottom. This flow creates a circular motion called a Convection Current.
3 RD ENERGY TRANSFER SCENARIO… The house is cold and the power goes out!!! Use the fireplace! How are the burning logs warming the house?
RADIATION!!! Radiation - The transfer of energy by electromagnetic waves. Think of the sun. On a cool day, stand in the shade… …then stand in the sunlight! You are being heated by the sun’s radiation!
HEAT TRANSFER… Heat can be transferred in three ways. Conduction– transfer of heat between particles without the movement of matter Convection– transfer of heat by the movement of currents in a fluid Radiation– transfer of energy by electromagnetic waves - The Transfer of Heat
HEAT MOVES ONE WAY If two objects have different temperatures, heat will flow from the warmer object to the colder one.
HOW WELL DOES A MATERIAL TRANSFER HEAT? On a cold morning, step from a rug to a tile floor… Rug feels comfy to the feet… Tile is COLD!!! What is going on?
CONDUCTORS & INSULATORS Conductor - Material that conducts heat well. What can you think of that is a good conductor? Metals, tile, and the like… Insulator - Material that does NOT conduct heat well. What can you think of that is a good insulator? Wool, wood, straw, paper and the like…
- The Transfer of Heat INSULATORS Air between the panes of this window acts as an insulator to slow the transfer of heat.
CLOSING… Give me an example of: Conduction Convection Radiation Give me an example of: Conductor Insulator