3. Heating Mercury Thiocyanate

The Science: It is an inorganic chemical compound, the salt of Hg²⁺ and the thiocyanate anion. It is a stable solid at room temperature that has the appearance of white powder with chunks; it can also be gray in color, depending on purity. It will produce a large, winding “snake” when setting on fire. This is known as the Pharaoh’s Serpent.^[2] Though some people still use it for this purpose, it is generally avoided because of the production of toxic gasses when this reaction occurs.

4. Hydrogen Peroxide Catalyzed by Potassium Iodide

The Science: It is a foamy substance caused by the rapid decomposition of hydrogen peroxide. This is often used for classroom demonstrations because it requires only a small amount of ingredients and makes a “volcano of foam”. This is also known as the “Marshmallow Experiment” in some cases, but should not be confused with the psychological Stanford marshmallow experiment.