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 Some fun with a fungus!

You can print these instructions out by choosing "PRINT" from your browser.

For this experiment you will need:

  • A packet of yeast (available in the grocery store)
  • A small, clean, clear, plastic (soda) bottle
  • 1 teaspoon of sugar
  • some warm water
  • a small balloon

Here's how to bring the yeast to life!:

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

  • 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.)

  • 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!"

As the yeast absorbs the sugar, it creates a GAS. (carbon dioxide) To demonstrate this, put the neck of the balloon over the top of the bottle and allow the bottle to sit for a while in a warm place, such as a sunny windowsill. Soon the balloon should start to blow up because it is filling with the gas created by the living yeast!

Clean up is easy. Remove the balloon (carefully) and throw it out. You can pour out the yeast solution in the sink. Notice that it smells like fresh bread or beer (which also contains yeast.) The plastic bottle can be reused or recycled.
We all know that there are "holes" in bread, but how are they made? The answer sounds a little like the plot of a horror movie. Most breads are made using YEAST. 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. Naturalist's note - The yeast used in this experiment are the related species and strains of Saccharomyces cervisiae. (I'm sure you were wondering about that.) Anyway, when the bread gets baked in the oven, the yeast dies and leaves all those bubbles (holes) in the bread. Yum.

-Science Bob

The project above is a DEMONSTRATION. To make it a true experiment, you can try to answer these questions:

1. Does room temperature affect how much gas is created by the yeast?

2. Does the size of the container affect how much gas is created?

3. What water/room temperature helps the yeast create the most gas?

4. What "yeast food" helps the yeast create the most gas? (try sugar, syrup, honey, etc.)

See if you can come up with more YEAST POWER experiments!