Have you seen the new Crayola Crystal Effects Window Markers? You can draw on windows with these markers. Better yet, you can use these markers to teach students some chemistry! After drawing on a window with these markers and waiting a little while, the marker ink appears to crystalize! Check out the video below to see how they work.
I bought some of these for my three sons (they're in 4th, 6th and 8th grade) and they had all kinds of fun using them to draw on the bathroom mirror. Even my college students find these markers interesting. In fact, I first became aware of these markers when two of my upper level chemistry students came by my office one day to ask me how they worked. I had never seen the markers before, but as I watched the marker ink crystalize, I was immediately reminded of a familiar chemistry demonstration: The crystallization of a supersaturated solution of sodium acetate. Sodium acetate is a weak base that can be formed from the reaction between the strong acid sodium hydroxide and the weak acid acetic acid:
NaOH + CH3COOH --> HOH + CH3COONa
Check out the video below to see the crystallization of sodium acetate from a supersaturated solution (skip to 0:57 in the video to skip an explanation of how to prepare the solution).
The similarities I observed between the crystallization of the marker ink and the supersaturated sodium acetate solution made me wonder if the markers contain supersaturated sodium acetate. So I headed into the lab with some of my students to do some experiments to test this idea. Below is a video of one of the experiments that we tried.
We’ve been working on quite a few more experiments on these markers to see if sodium acetate is present in the marker ink. One of my students will be working with these markers for her required small research project in my General Chemistry class. If you have the time, we’d sure appreciate it if you would comment with some ideas of experiments we might try.
The two references below describe how to prepare supersaturated sodium acetate solutions. These two references also describe some interesting experiments with these solutions.