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Elephant toothpaste is an experiment demonstrating a multiple increase in the volume of a substance as a result of a chemical reaction. It is often held in Western schools, since it requires very few readily available reagents , and the result is a “foam volcano”. Another name for this experiment is “marshmallow experiment”, however, it is not related to the more famous psychological experiment of the same name .
Experiment Description
Concentrated (> 30%) hydrogen peroxide is mixed with liquid soap, after which a catalyst is added to it - usually potassium iodide [1] . The catalyst causes the rapid decomposition of peroxide into water and oxygen; the latter, gathering in bubbles, sharply increases the volume of the mixture, creating bubbles and foam in the soap solution. This is an exothermic reaction , so the resulting foam has a high temperature, and a subsequent helps viewers to make sure that the gas released is oxygen [1] .
Under normal conditions, hydrogen peroxide itself decomposes into water and oxygen, but does it too slowly for this process to be noticed:
- 2H 2 O 2 → 2H 2 O + O 2 ↑
Iodide ion becomes a catalyst for the reaction, changing its course as follows:
H 2 O 2 + I - → H 2 O + IO - H 2 O 2 + IO - → H 2 O + O 2 + I - 2H 2 O 2 → 2H 2 O + O 2 ↑ Δ rH ° = −196 kJ / mol
Notes
- ↑ 1 2 NCSU .
Links
- Elephant's Toothpaste Neopr . University of Utah Chemistry Demonstrations . University of Utah. Date of treatment March 21, 2014.
- Elephant's Toothpaste - Kid Version . Steve Spangler Science. Date of treatment March 21, 2014.
- Catalytic Decomposition of H2O2 - Elephant's Toothpaste . NCSU Department of Chemistry Lecture Demonstrations . North Carolina State University. Date of treatment March 21, 2014.
- " Elephant's Toothpaste (slow motion) ." Periodic Table of Videos .
- The Elephant's Toothpaste Experiment