Today was take-your-kid-to-work-day.  In honor of this we put on a chemistry show in one of the labs.  Burned some Mg ribbon, shrunk some balloons in LN2, blew up some balloons with dry ice, reduced iodine with ascorbic acid, and we unmixed some NaCl and carbon black. 

One of the barriers to teaching chemistry is a level of physical abstraction that is hard to get around.  It is hard to get around trivial explanations when the audience is not ready to discuss electrons.  Many of the really insightful concepts in chemistry are inherently abstract and age inappropriate for the younger crowd, so to compensate, chemistry demonstrations are often heavy in the whizbang components.  That’s fine.  It should be fun and visually appealing, especially for K-6. 

I like to do mixing and unmixing because it demonstrates something about materials handling.  It also represents an activity that occupies much of our time.  Separation science is not commonly called “unmixing”, but for chemistry demonstrations it causes kids to ponder the problem for a bit.  They all have experience in mixing things- we talk about that.  Then I ask the question “What if I asked you to unmix that KoolAid”?  A few of the more worldly ones might suggest boiling off the water.  But most kids seem to be stumped- they will admit that they would have never considered the possibility of unmixing. 

So we dissolve some NaCl in water and make a solution.  The use of a magnetic stirrer and stirbar makes way for a minor diversion with magnets and iron filings. Then we blend in a bit of carbon black. Using a Buchner Filter, filter paper, and Celite, we do the vacuum filtration, showing the remains of the carbon in the Celite.  The filtrate is then treated with some “Anti-Solvent” like acetone and the salt comes crashing out. 

Yeah, I know. It is pretty tame.  But it can be done cheaply in 45 minutes and the kids can see their parents actually doing something.