1. Photosynthesis and Cellular Respiration
This lab will use phenol red as an indicator to determine whether CO2 is being consumed or produced during this activity. To demonstrate this we will observe what happens in a light and dark environment as we add Elodea to a test tube of acidic phenol red.

2. Materials 6 Test tubes 6 Rubber stoppers 2 Test tube racks
Graduated cylinder
Beaker containing 150 mL of phenol red
Sprig of Elodea plant
Light source
CO2 generator
Baking soda
Vinegar
Syringe
Black construction paper

3. Place 3 test tubes in the rack and fill two test tubes with 25 mL of phenol red using the graduated cylinder.

4. Using a CO2 generator change the remaining phenol red to yellow.

5. Fill the remaining 4 test tubes with 25 mL of the phenol red solution that you turned yellow. Submerge a sprig of Elodea completely into the first test tube and fourth test tube. Cover each test tube with a rubber stopper.

6. Place a piece of construction paper over the last three test tubes
Place a piece of construction paper over the last three test tubes. Illuminate the first three test tubes using a light source.

7. In approximately 60 minutes, examine the six test tubes and record your observations.
Under the light source
In the dark

8. Complete the table and answer the question.
Phenol red with Elodea
Observations (color change)
In the dark
In the light
What did this experiment tell us about the role of plants in our environment?

9. When you have finished with this activity, clean up your materials and return them to where you found them.