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When people and animals breath their bodies take oxygen into the lungs where it is passed into the blood. This is called respiration. There is another kind of respiration that goes on inside living organisms and that is called cellular respiration. During cellular respiration cells convert oxygen to carbon dioxide and water during a chemical reaction that happens inside the cell.
Yeast is a single cell organism that metabolized sugar and turns it into carbon dioxide and water. In this experiment you will be able to “see” the colorless, odorless gas that is carbon dioxide. You will know it is present because it will fill a balloon.
What You Need:
- Empty Water Bottle
- Warm Water
- 1 tsp Sugar
Put one packet of dry yeast into an empty liter soda bottle. Add about an inch of warm water to the yeast. Now add 1 tsp of sugar. Swirl this mixture around a little bit. Blow up a balloon and then let the air out again just to get it stretched a little. Now take the balloon and stretch its opening over the mouth of the water bottle. Check on the balloon every five minutes for the next half our or so. What happens to the balloon?
Science Experiment Idea: Try this experiment with three different soda bottles. Add the yeast to each one. Make your variable the substance you add to the yeast. Put water in bottle #1, soda in bottle #2, diet soda in bottle #3. You could try different kinds of juice, milk, etc. Which substance do you think will blow up the balloon the best? Why?
Here are some websites and books that will help you understand and explore yeast and cell respiration:
- Exploratorium: Yeast-Air Balloon
- Science Bob: Blow Up a Balloon With Yeast
- The Science of Yeast
- ZOOM Science Rocks: Yeast
- Kitchen Science Experiments – Balloon Blow-Up pages 30-32
- Science Experiments That Fizz and Bubble: Inflations Station (Pages 4-25)
- Science Projects for Curious Kids – Yeast Feast (pages 91-92)
Words to Know:
Respiration – Breathing, bringing oxygen into the blood.
Cell Respiration – The process cells use to convert oxygen into carbon dioxide and water. This is a little different than breathing. During cell respiration the cell takes in oxygen and gives off carbon dioxide during a chemical reaction inside the cell. This is the exact opposite of photosynthesis. During photosynthesis plant cells take in carbon dioxide and water and give off oxygen.
Metabolic – A chemical reaction that happens inside a living organism.
Yeast – A tiny little single cell fungus that can convert sugar into carbon dioxide. It makes a little chemical reaction all by itself.
Carbon Dioxide -A colorless, odorless gas that is made by animals and people when they breath, or by cells when they respirate. Carbon dioxide is absorbed by plants during photosynthesis.