The kids and I made Borax crystals a while ago. I'd actually wanted to do this for a long time but didn't find the time (or energy) to set it up until after Christmas. There are places all over the Internet to tell you How to make Borax Crystals but not many places that tell you why they work. I'm all for making pretty things but sometimes I like to teach my kids the science behind it too. First, shape pipe cleaners into any old shape and tie them to a pencil. Mix a ratio of 1 cup of boiling water : 3 T of Borax and pour them into canning jars and suspend the pipe cleaners in the Borax/water mix overnight.
Why does this work? Because hot water molecules move farther apart from one another than cold ones. When the water is hot, the dissolved Borax has places to go between the water molecules. But as the water molecules cool down and move closer together the Borax gets pushed out of the way.
All Borax crystals, no matter what size, have the same shape. Long rectangular shapes with flat sides. As the Borax gets crowded out by the water, they begin stacking up on one another (like Legos) onto the pipe cleaners. If the water is super saturated with Borax the pipe cleaners will only be able to hold so much and some Borax will crystalize at the bottom of your jar. There you go. Now you can make fancy shmancy Borax crystals but more importantly now you know why they work! Happy Science to you!
Well, now I know! The girls will love this project. Thanks for the idea!
ReplyDeleteI love that you did this! The chemical engineer in me is super happy that you wanted to know why it happens instead of saying "it just does."
ReplyDeleteCrystallization is really neat. Did you know that for some chemicals, it forms different crystals depending on the concentration and temperature of the mixture. (Similar to how snow/ice has different structures depending on how cold it is!)
Another explanation for the crystals coming out is that a super saturated solution is thermodynamically unstable, thus when a nucleation point is offered (the pipe cleaner), the crystals will begin to form until the crystals and solution are in equilibrium with one another. You'll find that the leftover solution will still have borax in it - the amount of borax in solution will depend on the temperature of the room it is in.
Wow, my nerdiness completely just came out there. haha.
@withoutadornment, thanks so much for explaining the chemical process so much better than I did. Now I'm wanting to make these in the middle of the summer when it's 100+ degrees here and see what happens. Thanks for sharing your nerdiness. P.S. I think nerdiness is wonderful and undervalued!
ReplyDeleteI loved making these borax crystals. But, to be completely honest with you I didn't even wonder how it happened. But I was sure excited when it did. But now that I know, I find it very interesting.
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