Chris Sanchez - Elephant Toothpaste

Title: Elephant Toothpaste

Principles Investigated:

catalysts, exothermic reaction, solute and solvent.

Standards: Chemistry

6a. Students know the definitions of solute and solvent

7b. Students know chemical processes can either release (exothermic) or absorb (endothermic) thermal energy.

8c. Students know the role a catalyst plays in increasing the reaction rate.

Materials:

For adults:

· Hydrogen peroxide (30%)

· Sodium iodide solution, 2 M

· Liquid soap (regular, not ‘antibacterial’)

· Food coloring

· Graduated cylinder (500 mL)

· Safety glasses

· Rubber gloves for clean-up

For kids:

· 16 oz empty plastic soda bottle (preferably with a narrow neck)

· 1/2 cup 20-volume hydrogen peroxide (20-volume is 6% solution)

· Squirt of Dawn dish detergent

· 3-4 drops of food coloring

· 1 teaspoon yeast dissolved in approximately 2 tablespoons very warm water

· Funnel

· Foil cake pan with 2-inch sides

· Safety glasses

· Lab smock

Procedure:

Adults:

1. Make sure wearing safety glasses, coat, and gloves
2. Add 20mL of the hydrogen peroxide to the graduated cylinder (cylinder should be in large tray or piece of plastic)
3. Add 5mL of dish soap to the graduated cylinder
4. Add food coloring into the graduated cylinder if desired
5. Add 5mL of sodium iodide to the cylinder and step back (fast reaction so move!)

Kids:

1. Make sure wearing safety glasses, coat, and gloves
2. Add ½ cup of hydrogen peroxide to bottle (bottle should be on the cake pan)
3. Add food coloring to the bottle if desired
4. Add 5mL of Dawn dish detergent
5. Mix 1 teaspoon of yeast in 2 tablespoons of warm water
   1. Add the yeast mixture to the bottle

Student prior knowledge:

This demonstration is intended to be for observations, but students should be familiar with the vocabulary: solute, solvent, exothermic, catalyst.

Explanation:

This explanation is for the “adult version,” the “kid version” works in a similar way. Hydrogen peroxide (H₂O₂), is a powerful oxidizer because it has two oxygen molecules. In the reaction, sodium iodide is a catalyst, which means it speeds up the reaction, or it speeds up the rate at which H₂O₂ breaks down. In the reaction, H₂O₂ breaks down to form water (H₂O) and oxygen (O₂).

H₂O₂ + catalyst à H₂0 + O₂

The soap in the mixture mixes with the water and fills up with O₂ causing it to foam up and overflow. Additionally, you may observe steam, this is because it is an exothermic reaction, meaning it gives off heat.

Questions and Answers:

1. The experiment we are doing is based on a 3% H₂O₂ concentration. What would happen if we used the 30% H₂O₂ solution?

The reaction would be even larger/more pronounced. The concentration of H₂O₂ is ten times greater so there is ten times more water and oxygen being produced at a time. This would cause the reaction (foam) to occur more rapidly. Also, because it is happening at such a faster rate, instead of oozing out, it would erupt from the container.

1. What is the catalyst in this reaction? How do you know? What does the catalyst do?

The catalyst is the yeast solution. We know because after we add it, the reaction occurs incredibly fast. The catalyst lowers the activation energy for H₂O₂ to react, causing it to turn into H₂0 and 0₂.

1. What does the steam tell us about this reaction?

The steam tells us that this is an exothermic reaction. It gives off heat.

Applications to Everyday Life:

1. A catalytic converter in automobiles has platinum and palladium acting as catalysts. These act on unburned fuel by lowering its activation energy enough to break it down into products that will not harm the environment (Levine, 347).
2. Enzymes are examples of catalysts. Almost every action in a cell requires an enzyme at some stage. Enzymes are responsible for breaking down food into small pieces so that nutrients may be absorbed.
3. If you wear contact lenses, chances are you have also cleaned them. Proteases are enzymes found in cleaners that remove proteins in order to prevent infection.
4. Rennin is an enzyme used in toe production of cheese, it hydrolyzes proteins.
5. In baby food the enzyme Trypsin is used to predigest the food.

Pictures:

Videos:

References:

Levine, Joseph S.; Miller, Kenneth R. (1994). Biology Discovering Life. D.C. Heath and Company.

Steve Spangler Science. Elephant’s Toothpaste. http://www.stevespanglerscience.com/experiment/elephants-toothpaste (Accessed 2011. April 11).

Steve Spangler Science. Elephant’s Toothpaste. http://www.stevespanglerscience.com/experiment/hydrogen-peroxide-eruption (Accessed 2011, April 16).

UC Davis Chem Wiki. http://www.chemwiki.ucdavis.edu/VVV_Demos/Elephant_Toothpaste (Accessed 2011, April 16).

Wikipedia. Elephant Toothpaste. http://www.en.wikipedia.org/wiki/Elephant_toothpaste (Accessed 2011, April 15).

Wikipedia. Enzymes. http://www.en.wikipedia.org/wiki/Enzyme (Accessed 2011, April 18).