MadSci Network: Chemistry

Re: how can I grow sugar crystals in water, need steps to make crystals.

Area: Chemistry
Posted By: Lynn Bry, Collective Enigma Elucidator
Date: Wed Jan 22 21:15:03 1997

I'd recommend going with salt crystals over sugar crystals, simply because sugar solutions often stay 'syrupy' in which case they don't form good crystals.

1) Boil some water - 1 - 2 cups..

2) Add 1 cup of salt to your water. Take the water off the heat and stir it, until as much of the salt goes into solution as possible.

3) Pour your saturated salt solution into a jar or other glass container. If there's still alot of undissolved salt, run it through a strainer or a paper towel to filter the salt grains. Over the top of your container, place a spoon or oblong obect. Tie some string to it so the string dangles in the solution.

4) Now you have two possible ways to make some crystals - one fast, one much slower..

Fast Way

This method makes use of the fact that temperature affects the solubility of many compounds. If you run a search of our site for solubility you can locate other files that discuss the chemistry behind this process. Basically, when you drop the temperature of your steaming salt solution by placing it in a refrigerator, some of the salt will precipitate out of solution to form crystals. The string dangling in the solution acts as a nucleation site for the crystals to form -- salt on a string!

Slower Way

This method uses evaopration to increase the concentration of salt in your original solution. Leave your salt solution uncovered on a counter for a few days. As the water molecules evaporate into the air, the solution becomes more and more concentrated, until the reminaing amout of water just can't hold all the salt in it anymore (a supersaturated solution). At this point the salt will begin to precipitate and form crystals.

Once you get crystals to form you can play with the amount of salt you add to the water, and perhaps try it with other compounds including sugar.

What's the advantage of one way over another? The first way is very fast, you can watch the crystals form right before your eyes. However, the second way (in my experience) tends to give nicer crystals, and you can watch as they develop and grow over many days.

Have fun!

Lynn Bry, MadSci Admin

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