Sacrificing Gummy Bears and Zinc Anodes

We are all the way up to the Oxidation-Reduction chapter of our chemistry textbook. I'm excited to have made it this far but anxious about what the students are understanding of it. Rust is the common "real life" example given for "redox chemistry", but watching a iron rust is not much of an engaging 'hook' for students. So I introduced the section with a "Gummy Bear Sacrifice" which is a marvelous lavender flame produced by dropping a gummy bear into molten potassium chlorate. When heated, potassium chlorate decomposes:

2 KClO3(s) → 2 KCl(s) + 3 O2(g)

This provides sufficient oxygen to ignite and oxidize the sugar in the gummy bear, which is an exothermic reaction:

C12H22O11(s) + 3 O2(g) → 9 C(s) + 3 CO2(g) + H2O(g)       ΔH = 5635 kJ



Why is the flame lavender colored?

The following day we talked about boats. Since we live along a major river and a few miles from the ocean, I thought it might make the whole "metals rust" notion relevant with protecting marine props from salt water corrosion with zinc anodes. They started getting the idea of how the electrons move, but are still struggling with writing the equations.