Elephant Toothpaste
Ruben Soriano and Candice Goodwin-Ms.
Meyer
Copper Hills High School, West Jordan, Utah
Abstract
Applications: Catalyst, Exothermic
Theory: Hydrogen peroxide typically decomposes at a rate of approximately 10%
per year, producing water and oxygen gas. The rate of this reaction can be
increased by introducing a catalyst—in this case potassium iodide will serve as
the catalyst. Powered potassium iodide or the potassium iodide coating on
potassium chips will also catalyze decomposition of hydrogen peroxide.
Potassium iodide illustrates the idea of catalysts and reactions that give off heat.
Since hydrogen becomes foam when it touches a cut, I think that when the
potassium iodide mixes with the hydrogen peroxide it will decompose the
hydrogen peroxide into water and oxygen. This decomposition gives off heat.
Introduction
During a chemical change, the original substances are changed into a new
substance. A chemical change is recognized by the disappearance of the
reacting substance and the appearance of other substances. Indicators of
chemical change include release of energy in the form of light, release or
absorption of energy in the form of heat, odor change, the production of gas
(bubbling) or a precipitate (solid), and a color change. Chemical changes cannot
be easily reversed. Although in science the term ‘chemical change’ is reserved for
processes in which the reacting chemical substances disappear and other (new)
substances appear, several studies have found that children often use the term
‘chemical change’ to encompass changes in physical states and other physical
transformations, particularly so when the color of a substance alters.
Materials and Methods
Materials: Liquid dishwashing detergent (5ml), 250ml Graduated cylinder, Potassium
Iodide. KI (10g), Hydrogen peroxide. 30% solution H2O2 (50 mL), food coloring, small
containers, Wooden Splint, Water, Lab smock and goggles, and Dishpan.
Methods:
Step 1: Put on your lab smock and goggles
Step 2: Mix liquid dishwashing detergent (5ml), Potassium Iodide KI (10g), and 3-4
drops of food coloring a small container. Then stir with wooden splint
Step 3: Fill a 250ml Graduated Cylinder with 50 ml of Hydrogen Peroxide
Step 4: Set the filled graduated cylinder on top of a dishpan
Step 5: Poor the solution from step 2 into the Graduated Cylinder containing Hydrogen
Peroxide quickly.
Step 6: Clean up equipment with plenty of water
Results
The figure shown below is the result immediately after the solution containing the
Potassium Iodide was poured into the Hydrogen Peroxide. It only took about 3 seconds
for the substances to interact and foam at a very fast rate.
Discussion
In this experiment, Potassium Iodide serves as a catalyst which makes the peroxide
molecule (H2O2) release the oxygen atom faster. A chemical reaction is taking place as
evidenced by a gas being released and a temperature change. The hydrogen peroxide
decomposes to form water and oxygen. 2H2O2
2H2O + O. These results
assure us that our hypothesis is correct. The only thing we did not include was the
colored foaming as displayed in the figure above. Our professor had us adjust that in the
preparation stages of our experiment. Based on these results, we could continue to
explore the topic by figuring out if all the hydrogen peroxide was really decomposed, or if
there was excess remaining.
References
Shakhashiri, B. Z. In Chemical Demonstrations: A Handbook for Teachers of
Chemistry; The University of Wisconsin Press: 1983; Vol. 1, p 180-185.
Lister, T. In Classical Chemical Demonstrations; The Royal Society of Chemistry:
1996; p 145-146.
Trujillo, C. A. J. Chem. Educ. 2005, 82, 855
Stone, C. H. J. Chem. Ed. 1944, 21, 300.
Acknowledgements
Our professor Mrs. Meyer helped us tremendously along the way of our experiment
during stages of confusion. Although she did not directly do any work, her guidance
allowed us to complete this project.
Video
http://youtu.be/HBmtTWYHKuM