Yeast in Action!

Materials:

• A packet of yeast (available in the grocery store)
• A small, clean, clear, plastic soda bottle (16 oz. or smaller)
• 1 teaspoon of sugar
• Some warm water
• A small balloon

Instructions:

1. Fill the bottle up with about one inch of warm water.
( When yeast is cold or dry the micro organisms are resting.)

2. Add all of the yeast packet and gently swirl the bottle a few seconds.
(As the yeast dissolves, it becomes active - it comes to life! Don't bother looking for movement, yeast is a microscopic fungus organism. We will observe the yeast under the microscopes later.)

3. Add the sugar and swirl it around some more.
Like people, yeast needs energy (food) to be active, so we will give it sugar. Now the yeast is "eating!"

4. Blow up the balloon a few times to stretch it out then place the neck of the balloon over the neck of the bottle.

5. Let the bottle sit in a warm place for about 20 minutes
If all goes well the balloon will begin to inflate!

Why it Works

As the yeast eats the sugar, it releases a gas called carbon dioxide. The gas fills the bottle and then blows up the balloon as more gas is created. The more the yeast eats, the more gas it creates and the bigger the balloon gets!

Believe it or not, yeast is actually living microorganisms! When bread is made, the yeast becomes spread out in flour. Each bit of yeast makes tiny gas bubbles and that puts millions of bubbles (holes) in our bread before it gets baked. So essential, the bubbles in your bread are waste from microscopic organisms called yeast! Yum?

Questions to investigate:

1. Does  temperature affect how much gas is created by the yeast?
2. What "yeast food" helps the yeast create the most gas? (try sugar, syrup, honey, etc.)