Chemistry Question: - RonO's Ramblings — LiveJournal
|Date:||March 10th, 2009 12:21 pm (UTC)|| |
We had a hard time with growing crystals. Yoou need to supersaturate the liquid and we were no where close.
In at least one case, the solution has to be pretty much saturated, there is salt sitting at the bottom of the container. On the other hand, that may in its self be a sign that something is wrong and the salt came out of solution too soon.
|Date:||March 10th, 2009 08:44 pm (UTC)|| |
What are the salts and which is in what solvent?
He has both table salt (NaCl) and white sugar (glucose?? I have no idea of the chemical formula) dissolved in both the acetone and the vinegar. 4 total tests (and no control).
C12H22O11 = 2 C6H12O6 − H2O
|Date:||March 10th, 2009 09:35 pm (UTC)|| |
We never could get the rock candy thing (supersaturated sugar-water solution + string) to work when we were kids. Don't know if our solution wasn't as super-saturated as we thought, or what.
Heat, my boy.
When I used to make rock candy, I would boil me some water, and stir in sugar while it boiled, till it wouldn't take no more. Quickly pour boiling solution into jar, place lid with string hanging down into jar - DO NOT TIGHTEN LID.
Let cool - when room temp is reached you may already see crystals forming on string. you can then screw on the lid and let nature take it's course.
Why the hell are they having kids use Acetone when both salt and sugar are dissolvable in water? The vinegar i can understand but acetone is an extremely dangerous solvent.
Actually, the experiment was to see if by using a solvent with a higher evaporation point you could grow larger crystals. The problem being that salt and sugar do not dissolve well in acetone. So these solutions were affected by the saturation levels, not just solvent evaporation rates. There are salt crystals formed on the string above the vinegar level though.
I guess my point was - they could have done the evaporation test using something safer, like methyl alcohol.
Ahhh, but it was I who decided to use acetone - not the school - it was cheap and it was there. And, I'm sure kiddo would have wrinkled his nose just as hard at the smell of methanol and he did with the acetone.