Conceptual Physics Heat Transfer 02a: Conduction beodom.com

Conduction – Transfer of heat between materials that are in direct contact. – Energy moves but molecules remain fixed in place. Conduction occurs in solids. Conductor – Material that transmits heat well pixfr.eu

Conduction Demo – rod and wax – Aluminum, brass, copper, iron and steel – Which blob of wax will melt first?? Explain! Metals are generally the best conductors: – Silver, copper, aluminum, iron 8thgradesciteach.blogspot.com

Conduction Good thermal conductors are typically good electrical conductors. Why are metals great conductors? – Atoms vibrate easily – Free electrons drift readily diytrade.com recipetips.com

Conduction Demo – Both blocks were in the freezer for the same amount of time. – Which block feels colder… left block or right block? – Which conducts/transfers heat better? pirt.asu.edu

Conduction How can a toilet seat feel cold in a room where the temperature is 70˚ F? – Air a poor conductor while seat is a better conductor of heat. … recall your butt is at 98˚! Why do tile floors feel cold? – Tile is a “good” conductor of heat. Why do rugs feel warmer? – Rugs are a “poor” conductor of heat.

Conduction Insulators – materials that transmit heat poorly; materials that “delay” heat transfer. How can you prevent heat transfer to (or from) your feet? – Choose a material that doesn’t conduct as well; – a material that insulates better like rugs and slippers! freshome.com

Conduction Why are pan handles made of wood? – They do not conduct heat as well as metal! Why are oven mitts made of thick fabric? – They do not conduct heat as well as flesh!

Conduction Examples of good insulators? – Pipe insulation – Air Fiberglass insulation Thermos Sleeping bag – Wood Cooking utensils nwpublicmedia.typepad.com scienceprojectideasforkids.co m

Conduction Demo – hand/oven – Why can I put my hand in the oven and not get burned? – Why can’t I put my hand on a metal at 350 degrees? Why do windows have argon in the middle? taylorgifts.com

Conduction Liquids and gases are generally good insulators. Back to air… snow is a tremendous insulator. Explain. – Lots of air between crystals. – NOT a source of heat, simply slows down the escape of when heat is present. flickr.com survivalistssite.com greatdreams.com

Conduction Heat is the TRANSFER of thermal energy… it is “something moving”… it’s tangible! Cold is not a thing! – Cold is the absence of thermal energy. We don’t insulate to keep “cold” out, we insulate to prevent the transfer of thermal energy… heat transfer! – Both winter and summer! blog.greenhomesamerica.co m deerparkroofing.com

Conduction Super-coolest-insulator of all times…wait for it… AEROGEL! – Looks like smoke – Feels like an extremely light, stiff packing foam. spaceflightnow.com stardust.jpl.nasa.gov

Paper around metal bar demonstation