Today we talked about heat transfer. The three different ways heat can move from one source to another.
I've included a chapter from my Bite-Size Physics book for homework this week. Please read the chapter and complete the questions at the end. (Please, don't look at the answers until you're done with the questions.)
Also for homework, take a look at four thermoses and/or travel coffee mugs. The job of thermoses/coffee mugs is to not allow heat to transfer out of the drink. Analyze each of the 4 thermoses/coffee cups in relation to all three different methods of heat transfer. Some things to think about:
Conduction: Wiggle and bump. Metals conduct well. So you don't want metals next to your liquids, it will drain the heat right out of them. Plastics, styrofoam, glass etc. do not conduct well, so those are better options.
Convection: This is fluid moving right? So the key to keeping conduction to a minimum, is to try to keep air movement to a minimum. You want to have as little air as possible to move around the liquid. Keeping the thermoses/coffee mugs as full as possible is good and even more important is to have a good lid.
Radiation: In this case, the heat will leave the same way heat leaves your hands, by electromagnetic waves. You don't want anything to absorb those rays so light or reflective surfaces are best to have next to your liquids.
Some more things to think about and answer in your thermos/coffee mug essay.
Some thermoses are "vacuum sealed". Why?
Is the outside surface of the thermos/coffee mug important as far as heat transfer goes? (The heat from the liquid is going into the mug...where does it go then?)
What does heat capacity have to do with the materials that a thermos/coffee mug is made of?
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"Science Jim" Mueller
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