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Q & A: diffusion and mixing

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Most recent answer: 10/22/2007
Q:
What does diffusion mean? How is it different from
mixing.
- Harsha (age 7)
A:
Diffusion is the random wandering of things (molecules, atoms, etc.) as they are pushed to and fro by little random jiggles of their neighbors. These little random jiggles are always present- the hotter something is, the more of them there are. Diffusion can mix up different chemicals on a small scale.

On a large scale, diffusion is very slow, because it takes a long time to go anywhere if you keep randomly changing direction. Other types of mixing- say the mixing you can get by stirring a spoon around in a cup, can do a faster job of swirling different materials together on a large scale.

Mike W.

(published on 10/22/2007)

Follow-Up #1: diffusion and life

Q:
so what does diffuison actully do to objects[eg.humans,all living things]?
- cheese (age 1)
holi,yorkshire,england
A:
That's not an easy question to answer because diffusion is present pretty much everywhere. It plays a role in essentially every chemical reaction in our bodies, carrying the reactants around so they get a chance to interact. For example, although our blood carries oxygen out near each cell, to get distributed over the last few microns, the oxygen must just diffuse around randomly.

Mike W.

(published on 10/22/2007)

Follow-up on this answer.