Thermal Energy Conversions Conduction - Convection - Radiation

Energy Terminology Absorbers - take in the energy Examples: Dark objects like black t-shirts and roof tops Reflectors - reflect the energy Examples: Shiny materials, mirrors, and aluminum foil

Conduction Transfer of thermal energy by direct contact Always from a solid hot object to a solid cold object Takes place in solid, liquid or gases Example: A metal spoon inside a saucepan gets hot while a saucepan is getting heated. If you were the chef in this picture and had to stir the contents for 20 minutes non-stop while on high heat – which type of spoon would you want to use?

Conduction - Continued In order for conduction to occur, there has to be a conductor. Conductors transfer heat easily The more tightly packed the particles of the conductor, the better it is Most often Metals-metal spoon, metal pan, copper, iron, steel, silver

Conduction - Continued The opposite of a conductor is an insulator. Does NOT allow heat to move easily through Most often wood, plastic, glass, fiberglass, air, Styrofoam, and double pane windows that is air between 2 panes of glass R-value - rates insulation for houses higher number the better R-1 R-16 R-20

Convection Transfer of thermal energy in fluids – anything that flows Always between liquids and gases Example: hot air balloon, wind, ocean & air currents, home heating, all the soup in a pot becoming warm warmer fluids (less dense) rise, buoyant convection cooler fluids (more dense) sink wearing sweater keeps the heat from being taken away from the body

Radiation Transfer of thermal energy through waves. Electromagnetic waves-light, ultraviolet rays, x-rays, infrared rays Travels though gas and no air (vacuum) (outer space) Colors reflect waves differently. Black absorbs, White reflects Example: sun’s energy, microwaves and radio waves infrared light bulbs, person warmed by a fire.