Elephant's toothpaste explained

Elephant's toothpaste is a foamy substance caused by the rapid decomposition of hydrogen peroxide using potassium iodide (KI) or yeast and warm water as a catalyst.[1] How rapidly the reaction proceeds will depend on the concentration of hydrogen peroxide.[2] [3] [4]

Because it requires only a small number of ingredients and makes a "volcano of foam", it is a popular experiment for children to perform in school or at parties.

Explanation

Description

About 50 ml of concentrated (>12%)[5] hydrogen peroxide is first mixed with liquid soap or dishwashing detergent. Then, a catalyst, often around 10 ml potassium iodide solution or catalase from baker's yeast, is added to make the hydrogen peroxide decompose very quickly. Hydrogen peroxide breaks down into oxygen and water. As a small amount of hydrogen peroxide generates a large volume of oxygen, the oxygen quickly pushes out of the container.[6] The soapy water traps the oxygen, creating bubbles, and turns into foam.[6] About 5-10 drops of food coloring could also be added before the catalyst to dramatize the effect. How rapidly the reaction occurs will depend on the concentration of hydrogen peroxide used.[7]

Chemical explanation

This experiment shows the catalyzed decomposition of hydrogen peroxide. Hydrogen peroxide (H2O2) decomposes into water and oxygen gas, which is in the form of foam, but normally the reaction is too slow to be easily perceived or measured:

2H2O2 -> 2H2O + O2 ^In normal conditions, this reaction takes place very slowly, therefore a catalyst is added to speed up the reaction, which will result in rapid formation of foam. The iodide ion from potassium iodide acts as a catalyst and speeds up the reaction while remaining chemically unchanged in the reaction process.[8] The iodide ion changes the mechanism by which the reaction occurs:

\begin\ce&+\ \ce&\ce&+\ \ce\\\ce&+\ \ce&\ce&+\ \ce&+\ \ce\\\hline\ce& &\ce&+\ \ce& &\Delta_\mathrmH^\circ = -196\text\endThe reaction is exothermic; the foam produced is hot (about 75°C or 167°F). A glowing splint can be used to show that the gas produced is oxygen.[9] The rate of foam formation measured in volume per time unit has a positive correlation with the peroxide concentration (v/V%), which means that more foam will be generated per unit time when a more concentrated peroxide solution is used.[10]

Variations

YouTube science entertainer Mark Rober has created a variation of the experiment, named "Devil's Toothpaste", which has a far more pronounced reaction than the version usually performed in classroom settings.[11] [12] The ingredients to create the devil's toothpaste reaction are the same as the regular elephant's toothpaste reaction, the only difference being the use of 50% H2O2 instead of the usual 35%. [13]

See also

External links

Notes and References

  1. Web site: Elephant Toothpaste. Imagination Station. 2017-10-27. https://web.archive.org/web/20171028042309/https://www.imaginationstationtoledo.org/educator/activities/elephant-toothpaste. 2017-10-28. live.
  2. Web site: Elephant's Toothpaste. University of Utah Chemistry Demonstrations. University of Utah. 21 March 2014. https://web.archive.org/web/20141223011338/http://www.chem.utah.edu/_documents/pdf/undergrad_program/elephants%20toothpaste.pdf. 23 December 2014. live.
  3. Web site: Elephant's Toothpaste - Kid Version. Steve Spangler Science. 21 March 2014. https://web.archive.org/web/20140318040009/http://www.stevespanglerscience.com/lab/experiments/elephants-toothpaste#sthash.aQZSJeLD.dpuf. 18 March 2014. live.
  4. Dirren. Glen. Gilbert. George. Juergens. Frederick. Page. Philip. Ramette. Richard. Schreiner. Rodney. Scott. Earle. Testen. May. Williams. Lloyd. Chemical Demonstrations. A Handbook for Teachers of Chemistry.. 1983. 1. 1 . 180–185. 10.1021/ed062pA31.2. 1985JChEd..62R..31K. free.
  5. Elephant's Toothpaste (slow motion). Periodic Table of Videos. The University of Nottingham. 2016-09-14. https://web.archive.org/web/20160928022022/https://www.youtube.com/watch?v=nfGXG8Lnndc. 2016-09-28. live.
  6. Web site: The Great Elephant Toothpaste Experiment!. PBS Parents. 2013-10-09. 2019-04-26. https://web.archive.org/web/20190426082059/https://www.pbs.org/parents/adventures-in-learning/2013/10/the-great-elephant-toothpaste-experiment/. 2019-04-26. live.
  7. Web site: Elephant Toothpaste: A Hydrogen Peroxide Chemistry Experiment. Using Hydrogen Peroxide. 2017-10-19. https://web.archive.org/web/20171011223907/http://www.using-hydrogen-peroxide.com/elephant-toothpaste.html. 2017-10-11. live.
  8. Dirren. Glen. Gilbert. George. Juergens. Frederick. Page. Philip. Ramette. Richard. Schreiner. Rodney. Scott. Earle. Testen. May. Williams. Lloyd. Chemical Demonstrations. A Handbook for Teachers of Chemistry.. 1983. 1. 1 . 180–185. 10.1021/ed062pA31.2. 1985JChEd..62R..31K. free.
  9. Web site: Catalytic Decomposition of H2O2 – Elephant's Toothpaste. NCSU Chemistry Lecture Demonstrations. 2015-12-06. https://web.archive.org/web/20160125045148/https://ncsu.edu/project/chemistrydemos/Kinetics/Elephants%20Toothpaste.pdf. 2016-01-25. live.
  10. Elephant Toothpaste. Journal of Chemical Education. 94. 7. 907–910. 10.1021/acs.jchemed.7b00040. 2017. Hernando. Franco. Laperuta. Santiago. Kuijl. Jeanine Van. Laurin. Nihuel. Sacks. Federico. Ciolino. Andrés. 11336/43230. free.
  11. Web site: NASA Engineer Sets Elephant Toothpaste Fountain World Record .
  12. Web site: YouTuber Mark Rober throws birthday party for Rocky River boy with brain cancer . 22 September 2020 .
  13. Web site: Mark Rober's Secret Devil's Toothpaste Recipe Revealed . March 2023.

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