These cool chemical reactions show why chemistry experiments and demonstrations are among the most exciting in science.
Elephant Toothpaste
Elephant toothpaste is a classic cool chemical reaction between hydrogen peroxide and potassium iodide. The reaction generates a column of steaming foam that looks like giant toothpaste an elephant might use. There are two ways of making elephant toothpaste. One makes a mountain of foam, while the other is safe enough for kids to make.
Dehydration of Sugar
Removing water from a compound is a dehydration reaction. Sulfuric acid reacts with ordinary table sugar (sucrose) in a dehydration reaction, releasing the water as steam and leaving behind a growing snake-like shape of carbon. This is why the dehydration of sugar is also known as the carbon snake reaction.
Make Colored Fire
Coloring flames is less a chemical reaction that it is a demonstration of the emission spectra of metal ions. Basically, you add metal salts to a flame and watch it change color. The oxidation state of the ion matters. For example, copper turns a flame either blue (Cu+) or green (Cu2+). Chemists use all manner of compounds, you it’s also easy to make colored fire at home using familiar ingredients.
Reaction Between Copper and Nitric Acid
Nitric acid reacts with most metals. Reacting it with copper from a wire or a penny causes a color change, heat production, and colored vapor release. It’s a great example of an exothermic reaction and a chemical change.
Reaction Between Sodium and Water
Sodium reacts with water in a rather spectacular fashion. It burns with a yellow flame, releases sparks, and produces hydrogen gas. Other alkali metals react even more vigorously, plus they burn in colors characteristic of their element.
The Thermite Reaction
The thermite reaction is an exothermic reaction between a metal and a metal oxide. Essentially, it’s the rapid oxidation or burning of a metal. The most common reaction is between aluminum and iron oxide. You need an energy source (like a torch or sparkler) to get the reaction going, but once it starts the thermite reaction releases plenty of heat and light and keeps itself going until its fuel burns out.
Supercooling Sodium Acetate
Another name for sodium acetate is “hot ice” because the compound crystallizes into a solid that looks a lot like water ice, but releases heat as it changes phase so it’s hot. You can order sodium acetate online, but all you do to make it yourself is mix baking soda (sodium bicarbonate) and vinegar (weak acetic acid) and boil the liquid until you see tiny crystals form. At this point, there is so little water left that the sodium acetate is supersaturated or supercooled. Disturbing it or lowering its temperature prompts instant crystallization.
References and Further Reading
For finding cool chemical reactions, the author’s favorite source is the series by Bassam Shakhashiri.
- Shakhashiri, Bassam Z. (1983). Chemical Demonstrations: A Handbook for Teachers of Chemistry (1st ed.). University of Wisconsin Press. ISBN: 978-0299088903.
- Summerlin, Lee R.; Borgford, Christie L., Ealy, Julie B. (1988). Chemical Demonstrations: A Sourcebook for Teachers Volume 2 (2nd ed.). American Chemical Society. ISBN: 978-0841215351.