Kids' Chemistry: Crystals

Crystals are molecules making regular formations.  This is usually dictated by the chemical properties of the molecule.

Water, for example, is a not just H2O, it's H-O-H.  It's polar: the larger oxygen atom carries a slight charge which bends away from the smaller hydrogen atoms.  This creates a bend in the molecule and causes the water molecules to stick to each other in regular ways.  That's why all snowflakes form with six sides; water crystals are 6 sided.

We started out by looking at examples of crystals in our rock collection.  This was lots of fun, and we got to talk about how different imperfections affect the clarity, color, and shape of the finished crystal.  Pure quartz, for example, is clear.  But different contaminants give it other colors: rose quartz (pink), smoky quartz (brown), citrine (yellow),  or  amethyst (purple). Agate, jasper, carnelian, tiger's eye, and onyx are all other kinds of contaminated quartz.





Next we looked at some salt crystals we had grown earlier.  The crystals which formed quickly were small and irregular.  The ones which had formed more slowly were larger and more perfect.

Then we made rock candy by making a super saturated sugar solution (3 cups of sugar to 1 cup water).

I have had trouble making rock candy before, but this time it worked pretty well.  I dipped the popsicle sticks into the sugar solution, then rolled them in sugar to make seed crystals. before hanging them back in the solution.

After a week, they were large enough to enjoy, although they didn't grow as large (or perfect) as the commercially available rock candy.

Still, it's the most success I've had, and they tasted like sugar!

Lastly, I tried an experiment I've wanted to do since I was a kid: grow a crystal garden!

I never got to do this because my Mom could never find bluing.  But I have the internet!

Here's what you need:
a dish or pie plate
porous substrate: bricks, concrete, charcoal, coal, even wood
2 parts water
4 parts non-iodized salt
2 parts ammonia
2 parts bluing

Put the substrate in the dish.
Mix the rest of the ingredients and pour them over the substrate.
When the liquid is gone, you can make more and add it to the dish (not on the crystals) to keep the crystals growing.

Here's what is happening: you are growing contaminated salt crystals.  The bluing breaks up the cubical form of natural salt crystals to give a feathery "flowery" growth.  The ammonia increases the evaporation and makes the crystals form faster (also interfering with their regular shape).  You know the contaminants make these salt crystals toxic, right?

And that was it for our Kids' Chemistry!  Hooray!  We made it!  And I hope it helps anyone else out there who wants to do a little chemistry exploration with kids!