Both chemistry and cooking are about combining ingredients to create something completely different. In cooking, certain ingredients, such as yeast and sugar, are vital to the finished product because of the chemical reaction they produce when they're combined. This activity demonstrates how yeast works.
- 3 tablespoons sugar
- 1/2 cup warm water
- 3 small packages active dry yeast
- One empty 1-quart soda or juice bottle
- Rubber band
- Have your child dissolve the sugar in the water.
- Stir in the yeast, then pour the mixture into the bottle.
- Stretch the opening of the balloon over the mouth of the bottle and secure it with the rubber band.
- Set the bottle in a warm place, such as on top of your refrigerator.
- In a while, the balloon will inflate. Why?
- The yeast cells are eating the sugar, and as they do so, they produce a gas called carbon dioxide. Carbon dioxide is heavier than oxygen, so it pushes the oxygen in the bottle up and into the balloon. The same happens with yeast used in cooking. In that case, the release of carbon dioxide helps dough rise.