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.

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

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

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

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.

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

source.

In approximately 60 minutes, examine the six test tubes and record your observations.

In the dark

Under the light source

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?

When you have finished with this activity, clean up your materials

and return them to where you found them.