Activity Time: 25 minutes
Recommended Grades: 3 - 8
Objective: Investigate exothermic chemical reactions that will create not only heat, but also foam.

• 3 tablespoons of warm water
• Small cup
• 1 packet of dry yeast
• Clean 16-oz. soda bottle
• ½ cup of 6% solution of hydrogen peroxide
• 1 tablespoon dishwashing soap
• Safety goggles (optional)
• Food coloring (optional)

1. To the clean 16-oz. soda bottle, you will need to pour in ½ cup of the 6% solution of hydrogen peroxide. Because hydrogen peroxide can irritate skin and eyes, we recommend that little scientists wear safety goggles and that an adult carefully pour the hydrogen peroxide into the bottle.
2. Next (optional), add eight drops of your favorite color food coloring into the bottle.
3. Add about one tablespoon of liquid dish soap into the bottle.
4. Lightly move the bottle around to mix it.
5. In the small cup, combine 3 tablespoons of warm water and a full packet of dry yeast.
6. Mix warm water and yeast mixture for about 30 seconds.
7. Once the yeast and water are mixed, pour the mixture into the bottle and watch the eruption begin!

If you look closely at foam, you will see tiny foam bubbles. Each tiny foam bubble contains oxygen. In our experiment, the dry yeast acts as a catalyst to remove the oxygen from the hydrogen peroxide, creating the bubbly foam. A catalyst is a substance that speeds up a chemical reaction. By adding the yeast, we increased the rate of foam formation which resulted in lots of bubbles.

The overall experiment created an exothermic reaction. An exothermic reaction creates heat and doesn’t require a lot of energy. (The opposite of an exothermic reaction is an endothermic reaction which instead of creating heat, requires heat for it to occur.) If you touch the soda bottle, you may notice that it feels warm. How cool is that?