Elephant's toothpaste

This week, I would like to talk about a common classroom demonstration—elephant’s toothpaste. The reaction behind this experiment is quite simple. It’s just about the spontaneous decomposition of hydrogen peroxide (H₂O₂) and the equation is showed below:

Here is the “recipe”:

1. 100 mL 30% hydrogen peroxide

2. 2.5 g KI

3. 20 mL surfactant

4. 3 mL fod coloring (or watercolor) in any color you like

    Put these things all together in a cylinder or something is long and has an upward opening than there will be a amazing show like this:

           So… it’s obvious why it gets its name “elephant’s toothpaste” ~~

           I want to talk about the role of each agent now. Hydrogen peroxide, is the main reagent while potassium iodide (KI) serves as catalyst (催化劑) and can be replaced by yeast or ferric cation (Fe³⁺). The present of catalyst makes the reaction much faster. Surfactant is used to retain the oxygen produce by decompose and makes bubbles. Finally, the coloring is optional because they are merely used to make the experiment colorful XD

    Enjoy yourself with this easily-conducted experiment!

*Attention

1. The decomposition reaction is exothermic and will make the container quiet hot!

2. 30% hydrogen peroxide is a strong oxidant which may cause serious result, please handle it with care!

Reference:

1. http://pubs.acs.org/doi/pdf/10.1021/acs.jchemed.5b00037

2. https://en.wikipedia.org/wiki/Elephant_toothpaste