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Q & A: Sugar Crystals in Salt Water

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Most recent answer: 10/15/2011
Q:
Would sugar crystals form in tap water or salt water? Why, or why not?
- Dillon (age 11)
Gonzales, LA
A:
Dillon -

We're guessing you mean water that has sugar dissolved in it, since sugar crystals wouldn't form in sugar-free tap water or salt water.

If you dissolve some sugar in both salt and tap water, then let enough water evaporate, you will get sugar crystals from the tap-sugar water and a mixture of sugar and salt crystals from the salt-sugar water. The sugar crystals should have almost no salt in them and the salt crystals should have almost no sugar in them. You may be asking how concentrated the sugar solution has to get before crystals start to form. We're not sure how much that depends on the salt concentration, but it shouldn't be too hard an experiment to do.

Mike W.

(published on 10/22/2007)

Follow-Up #1: crystals from solution

Q:
How much sugar/salt do I use in how much water to grow crystals for an experiment?
- zane (age 11)
sebring FL HIGHLANDS
A:
At some temperature there will be a certain amount of (for example) sugar that will stay dissolved per cup of water. If you want new crystals to form you have to somehow get more sugar into solution. The way to do that is to heat up the water, since the amount of sugar (or table salt) that can dissolve goes up as the water gets hotter.

So you can take hot water, dump lots of sugar in it, and stir well for a while to get as much dissolved as you can. Then you can let the sugar settle and pour the very sugary water off the top, separating it from the old crystals. As it cools new crystals will form in it.

Mike W.

(published on 10/15/2011)

Follow-up on this answer.