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Q & A: diffusion vs. stirring

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Most recent answer: 06/18/2017
Q:
What is the difference between diffusion and stirring
- Dingo (age 15)
Melbourne
A:

Diffusion is the result of random thermal motions. It's always present even in thermal equilibrium. Those random thermal motions cause molecules to spread out. The range of the spread grows as the square root of time, so diffusion does a great job of spreading things out short distances. Long distances take very long times.

Stirring is a large-scale non-equilibrium process, just what you might do with a spoon to mix up some cake batter. These large-scale motions can help mix things together on a large scale. diffusion can then complete the process by mixing things on a small scale.

Mike W.


(published on 06/18/2017)

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