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At room temperature....

How long will the sugar stay suspended once dissolved ?

What governs the rate of settling ?

What part does Brownian motion play ?

Sugar might be a bad example...please substitute as needed.

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1 Answer 1

up vote 3 down vote accepted

Anything dissolved is kept "suspended" by brownian motion. Theoreticly there will be a small gradient of concentration due to gravity, but this is unmeasurable for sugar. (Barometric formula). For much bigger particles (ãbout µm) , this gradient can be determined.

The sugar will stay dissolved until the water evaporates, then the sugar will form a solid residue. (if You are lucky, as crystals) Settling does not occur with molecules.

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I'd like to see an explicit mention of entropy vs internal energy, and a bit more thermodynamics in the answer, rather than just a microscopically detailed mechanical description. –  genneth Feb 21 '11 at 10:14
    
@ genneth, Feel free to write an answer including entropy. –  Georg Feb 21 '11 at 11:02
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