Photosynthesis Lab

Introduction: Green plants use the sun’s energy to make glucose. A reactant is CO 2 gas! CO 2 + H 2 O makes a weak acid. The pH indicator Phenol Red can show us if photosynthesis is occurring by how acidic or basic the water gets in the test tube!

1. Open to a clean sheet of notebook paper. 2. Write the title at the top of the page. “Photosynthesis Lab”

Purpose: The purpose of this lab is to put plant cells in different growing conditions in order to see the changing rates of photosynthesis. The Big Question: Can you prove with data that plants need both CO 2 and Light to complete photosynthesis?

Using Phenol Red: 1. Phenol Red should not touch your skin! 2. Phenol Red shows a pH range from 6.8 (yellow/orange) – 8.2 (red). 3. Any pH lower than 7 is acidic and above 7 the solution is basic. 4. If the CO 2 is used for photosynthesis and releases O 2 gas, then the liquid will return to its original color (a reddish-pink).

Phenol Red Solution Phenol Red Solution Phenol Red Solution Phenol Red Solution Test Tube A Test Tube B Test Tube C Test Tube D Wrap in Foil

Procedure: 1. Put on safety goggles. These must be worn at all times. 1. Put on safety goggles. These must be worn at all times. 2. Take four test tubes and label them A through D. Also, label them with your groups name and period using the China markers 2. Take four test tubes and label them A through D. Also, label them with your groups name and period using the China markers 3. Find the phenol red solution in a 250-mL flask. 3. Find the phenol red solution in a 250-mL flask. 4. Gently blow through the straw. Keep blowing until there is a significant change in the appearance of the phenol red solution. 4. Gently blow through the straw. Keep blowing until there is a significant change in the appearance of the phenol red solution.

5. When your solution has changed color fully (approximately 2 minutes), pour this solution into each test tube. You want to fill each test tube approximately half-full with the solution. Carefully put on the parafilm. 5. When your solution has changed color fully (approximately 2 minutes), pour this solution into each test tube. You want to fill each test tube approximately half-full with the solution. Carefully put on the parafilm. 6. Record your observations in a data table in your laboratory notebook. 6. Record your observations in a data table in your laboratory notebook. 7. Label each of your test tubes according to the letters indicated in the data table. Be sure to put your group’s name on the labels too! Now add an elodea plant to the specified test tubes. Add the elodea to A and B. 7. Label each of your test tubes according to the letters indicated in the data table. Be sure to put your group’s name on the labels too! Now add an elodea plant to the specified test tubes. Add the elodea to A and B. Tubes A & C (requiring light) should be placed in the test tube racks. Tubes A & C (requiring light) should be placed in the test tube racks. Test Tubes B & D (in the dark) need to be wrapped COMPLETELY in FOIL. Test Tubes B & D (in the dark) need to be wrapped COMPLETELY in FOIL.

8. After 24+ hours, examine each test tube, and note any change in the appearance of the phenol red solution. 9. Record your observations in the data table.

Data Table Test Tube: Initial color of Phenol Red solution: Color of solution after blowing: Color of solution after 24 hours: A – Placed in the Light with Elodea RedOrangeRed B – Placed in the Dark with Elodea. RedOrangeOrange C – Placed in the Light without Elodea RedOrangeOrange D – Placed in the Dark without Elodea. RedOrangeOrange

Concentration Of CO 2 Concentration Of O 2 For every 6 CO 2 molecules taken in by the plant, 6 O 2 molecules are released Color change due to acidic level of CO 2 in solution. AcidicBasic