Solids, liquids, and gases dissolve to form solutions. In chemistry class, students made a concentrated solution of calcium acetate in water. By mixing together this concentrated calcium acetate solution with ethyl alcohol, students form a colloidal gel that acts like the commercial product Sterno®. The formation of the gel is a physical phenomenon and not a chemical reaction. When this gel is burned, it can be used as a heat source more desirable than pure alcohol because it is less likely to spill.
2 C2H5OH + 7 O2 -> 4 CO2 + 6 H2O
Students roasted their homemade marshmallows over the sterno. The homemade marshmallows roasted differently than store-bought ones, giving a creamier and smoother melted interior.
The exact structure of the gel is not known, but the calcium acetate solution probably traps the alcohol inside a flexible lattice. If the gel were to sit for several days, the alcohol and water would evaporate, leaving behind the solid calcium acetate.
The video that follows was assembled a few years ago. A newer video was created this week, but was overly large for this post. I have tried to reduce the size but it has not been going well.
A scientist and teacher, I am a life-long learner who enjoys camping, gardening, hiking, canoeing, and figuring things out! (Figuring stuff out is what science is all about.) After 18 years as an Environmental Consultant, I began teaching high school science and love it. My writings here reflect some of my thoughts about teaching, as they occur. I look forward to conversations with other thoughtful teachers.