January 22, 2009

1. Bellringer
2. FanTAKStic Quiz
3. Lab Demo - Elephant Toothpaste
(see recipe below)
4. Homework - Find the secret word for your class period in the blog.

Elephant Toothpaste

Materials

16 oz. empty plastic soda bottle (preferably with a narrow neck such as those made by Coca-Cola)
1/2 cup 20-volume hydrogen peroxide (20-volume is 6% solution, purchased from a beauty supply store)
Squirt of Dawn dish detergent
3-4 drops of food coloring
1 teaspoon yeast dissolved in ~2 tablespoons very warm water
Funnel
Foil cake pan with 2-inch sides
Lab goggles
Lab smock

1. At each student's place: cake pan, plastic bottle, Dawn in small cup, food coloring, funnel, goggles and smock, 1/2 cup peroxide, dissolved yeast mixture. 2. Stand up bottle in the center of the cake pan. Put funnel in opening. Add 3-4 drops of food coloring to the peroxide and pour the peroxide through the funnel into the bottle. Show a water molecule diagram and a peroxide molecule diagram, pointing to the extra oxygen that will be set free. 3. Add the Dawn detergent to the peroxide in the bottle. 4. Pour the yeast mixture into the bottle and quickly remove the funnel. 5. The students can touch the bottle to feel any changes that take place.

Observations

The reaction creates foam that shoots up out of the bottle and pools in the pan. After a minute or so, it begins to come out in a moving stream that looks like toothpaste being squeezed our of a tube. The students can play with the foam as it is just soap and water with oxygen bubbles. The bottle will feel warm to the touch as this is an exothermic reaction.

How does it work?

Talk about the addition of the yeast as a catalyst which makes the peroxide molecule release the oxygen atom faster.