Convection, Conduction, and Radiation

 Heat is…  Thermal energy in transit (moving!)  Molecules are moving and bouncing around – the faster they go – the hotter it gets!  Energy ALWAYS transfers from warmer matter to cooler matter until both reach the same temperature

 Heat always moves from a warmer place to a cooler place.  Hot objects in a cooler room will cool to room temperature.  Cold objects in a warmer room will heat up to room temperature

 If a cup of coffee were left on the table in this room what would happen to it?

 If two scoops of Orange Leaf frozen yogurt was left on the table in this room what would happen to it?

 Energy moves from one place to another…  Three ways for heat to transfer  Conduction  Convection  Radiation

 The process by which heat energy travels through solids.  Heat transfers thanks to direct contact with matter of a higher temperature  Matter must be present and touching

 If one end of a solid material is heated, heat energy passes into it. As this happens, the particles in the heated end of the solid vibrate more quickly and strongly. Because the particles are packed tightly together, they bump into neighboring particles then begin to vibrate more quickly and vigorously, and in turn they bump into particles close to them. In this way heat is transferred along the length of the solid. As this happens, the solid becomes warmer throughout.

 Process where heat energy is transferred by physical contact through a substance. Particles of a substance have to touch each other to pass heat from warmer to cooler. Warmer area, Lots of KE Cooler area, gaining KE… warming up Collision of particles

 Think…hot blacktop!  When you walk on the black asphalt in the summer and it scorches your feet…  PERFECT example of conduction

 A good conductor is a substance that allows heat to transfer through it easily.  A bad conductor (Insulator) is a substance that does NOT allow heat to transfer very well toward the cooler area.

 Think…EARTH! (or oven)  This is the process of heat rising and cool air falling that we’ve talked about

 Convection is the transfer of heat by the actual movement of the warmed matter  Liquids and gases  Matter must be present  Examples:  Heat a pot filled with pasta – rises and falls  Heat from the center of the Earth rising – Causing volcanoes and shifts in plates  Ovens – heat rises and cools  etID=70332e27-f6c4-4ce5-8d5e- c5b6d397d6f7&productCode=DSC&CFID= &CFTOKE N= etID=70332e27-f6c4-4ce5-8d5e- c5b6d397d6f7&productCode=DSC&CFID= &CFTOKE N=

 Think….SUN!  The sun’s rays provide us with heat, maybe even a sunburn! But, it’s so far away we can’t actually touch it…

 Radiation is the transfer of energy through electromagnetic waves  Does not rely on any contact between heat source and heated object  Examples:  Sunburn from Sun’s rays  Heat from campfire toasting marshmallow