Elephant Toothpaste continued
2
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Tips
• You may want to do this demonstration in the laboratory sink since there is a lot of foam produced. Cleanup, however, is
easy due to the presence of extremely safe products and the generous amount of detergent.
• The cylinder will get hot, so let it cool before handling.
• This demonstration can be easily and safely scaled up for larger audiences. A 500-mL or 1-L Pyrex
®
graduated cylinder
works well in this case.
• The slight brown tinge of the foam at the beginning is due to the presence of free iodine produced by the extreme
oxidizing ability of the 30% hydrogen peroxide.
• Another catalyst that will catalyze this reaction is manganese(IV) oxide, MnO
2
.
• To demonstrate that oxygen is indeed one of the products, light a match and blow it out. Ideally, the center of the match
will still be orange. Hold the match very close to the foam produced—the match should reignite.
Discussion
This demonstration evolves a good deal of heat as shown by the steam coming off of the foam as it is produced. The reaction,
therefore, is exothermic. The action of a catalyst is demonstrated. The catalyst is the I
–
(aq) ion which speeds up the
decomposition of the hydrogen peroxide. The decomposition of hydrogen peroxide produces steam and oxygen gas. The
oxygen gas and water vapor cause the dishwashing liquid to foam.
I
–
(aq)
2H
2
O
2
(aq) → 2H
2
O(g) + O
2
(g) + Energy
Connecting to the National Standards
This laboratory activity relates to the following National Science Education Standards (1996):
Unifying Concepts and Processes: Grades K–12
Evidence, models, and explanation
Content Standards: Grades 5–8
Content Standard B: Physical Science, properties and changes of properties in matter
Content Standards: Grades 9–12
Content Standard B: Physical Science, structure and properties of matter, chemical reactions, interactions of energy
and matter
Acknowledgement
Special thanks to Jim and Julie Ealy of The Peddie School in Hightstown, NJ.
Reference
Stone, C. H. J. Chem. Ed. 1944, 21, 300.
Flinn Scientific—Teaching Chemistry
™
eLearning Video Series
A video of the Elephant Toothpaste activity, presented by DeWayne Leineman, is available in Decomposition Reactions, part of the
Flinn Scientific—Teaching Chemistry eLearning Video Series.