L7 Diffusion I

L7 Diffusion I - Diffusion I Oct. 20, 2009 Learning...

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Diffusion I Oct. 20, 2009
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Learning objectives Be able to state the definition of diffusion, and recognize when it is happening Learn to interpret Fick’s 1 st and 2 nd Laws Given a concentration profile: Determine relative magnitudes and directions of Flux Determine how concentration will change with time
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We are going to be learning about how atoms move around in solids, and how we can put atoms where we want them to be inside a solid.
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Diffusion you already know. .. You are baking an apple pie, and after a while, you can smell apple pie all around the house. The apple pie scent molecules have spread through the air, that is largely diffusion. http://thegazz.com/gblogs/bloginmysoup/files/2008/01/800px-apple_pie.jpg
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QUESTION What if you turn on the fan to blow the aroma throughout the house. Is that still diffusion? A) YES B) NO C) Huh? http://www.publichealth.columbus.gov/Asset/iu_images/NewsAlert/fan.png
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DEFINITION Diffusion is transport of matter by random atomic motion. It does not include mixing and stirring, or convection.
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Diffusion you already know. .. You are marinating some food for a BBQ. If you only leave the food in the marinade for a short while, what part will have the most flavor?
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Diffusion you already know. .. What do you have to do to get the flavor into the middle of the food?
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http://www.cartoonstock.com/lowres/sea0323l.jpg
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To get the flavor deeper into the food: Wait longer. [ effect of time on diffusion] Poke holes in the food. [ effect of easier pathways on diffusion] Increase the temperature. [ effect of temperature on diffusion]
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In these two examples, diffusion was in a gas or in a liquid. Diffusion can also happen in a solid, but it is slower. We will be studying diffusion in solids.
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This note was uploaded on 11/28/2010 for the course MTE 209 taught by Professor Tanyafalten during the Fall '09 term at Cal Poly Pomona.

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L7 Diffusion I - Diffusion I Oct. 20, 2009 Learning...

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