CARBON DIOXIDE PRODUCTION BY YEAST

KEY CONCEPTS

  1. Yeast is a simple fungus containing tiny plants that use sugar and oxygen to produce energy. In the process of producing this energy, carbon dioxide is also formed.
  2. This process is called, respiration the opposite of photosynthesis, which is the use of light energy and carbon dioxide to produce sugar and oxygen.
 

MATERIALS

  • teaspoon
  • soda bottle
  • drinking glass
  • warm water
  • sugar
  • package of powdered yeast
  • 18 inches of aquarium tubing
  • modeling clay
  • limewater (see "How to make Limewater" activity)
  • field journal
 
 

PROCEDURE

  
 
 

Activity

  1. Pour 1/2 package of yeast into the soda bottle.
  2. Fill the bottle 1/2 full with warm water.
  3. Add 1 teaspoon of sugar to the bottle.
  4. Place your thumb over the top of the bottle and shake vigorously. You want to mix the contents of the bottle as best you can.
  5. Place one end of the aquarium tube into the bottle (about a quarter inch deep).
  6. Use the modeling clay to 1) hold the tubing within the bottle, and 2) to completely seal off the top of the bottle.
  7. Fill the glass 1/2 full with limewater.
  8. Insert the free end of the tube into a glass that is 1/2 full of limewater. Make sure the tube is within the limewater.
  9. Observe the setup periodically for several days. Keep a journal of what happens.
 
 

Footnote

  • Check the soda bottle for foaming. Bubbles of gas flow out of the tube and into the limewater. The limewater turns cloudy. The cloudiness of the limewater is proof that the bubbles produced by the reaction are carbon dioxide. Why? Limewater only turns cloudy when it is exposed to carbon dioxide gas. Within the soda bottle, the yeast used the sugar and the oxygen to produce energy and carbon dioxide. Why does the carbon dioxide travel up through the tube and into the limewater?
 
 

Assessment Ideas

  • List other types of animals that produce carbon dioxide. Do the opposite of this experiment. Instead of yeast, take a green plant and plant it in the bottle (use soil, water, etc.). You may have to use a bottle with a larger top. Observe the bottle and plant for several days. What happens? Why?
  • Try the experiment with different amounts of sugar, yeast, and warm water. Does it make a difference to the results? Why or why not?
  • What kind of energy is being produced by the system? Is it the same type of energy produced when human beings breath in oxygen?
 
 
 

CROSS-CURRICULAR IDEAS

  • English/Language Arts: Have the students maintain journals. Daily observations should be recorded. The amount of foaming in the bottle, the amount of bubbling, and the color of the limewater need to be observed.
 
 

VOCABULARY

  • energy: vigor or intensity of action. Kinetic energy is the energy created by bodies in motion (like fast moving molecules). Energy is also the inherent power to produce an effect. Why type of effect happens with our chemical reaction?
  • fungus: any non-flowering plant that has no chlorophyll (includes mushrooms, molds, and mildew). Yeast is composed of minute cells of fungi.
  • photosynthesis: the opposite of respiration. The process of using light energy and carbon dioxide to create sugar. Oxygen is a by-product of the process.
  • respiration: the opposite of photosynthesis. The process of using sugar and oxygen to create energy. Carbon dioxide is a by-product of the process.
 
 

SOURCE

  • "Winds of Change" educational CD-ROM, Copyright Caltech and NASA/Jet Propulsion Laboratory