Photosynthesis Photosynthesis LabLab

Introduction: Introduction: Green plants use the Green plants use the sun’s energy to make glucose.sun’s energy to make glucose.

A reactant is COA reactant is CO22 gas! gas!

COCO22 + H + H22O makes a weak acid.O makes a weak acid.

The pH indicator Phenol Red can show The pH indicator Phenol Red can show us if photosynthesis is occurring by us if photosynthesis is occurring by

how acidic or basic the water gets in how acidic or basic the water gets in the test tube!the test tube!

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

Purpose: Purpose: The purpose of this lab The purpose of this lab is to put plant cells in different is to put plant cells in different growing conditions in order to see growing conditions in order to see the changing rates of the changing rates of photosynthesis.photosynthesis.

The Big Question: Can you prove The Big Question: Can you prove with data that plants need both with data that plants need both COCO22 and Light to complete and Light to complete photosynthesis?photosynthesis?

Using Phenol Red: Using Phenol Red: 1.1. Phenol Red should not touch your skin!Phenol Red should not touch your skin!2.2. Phenol Red shows a pH range from 6.8 Phenol Red shows a pH range from 6.8 (yellow/orange) – 8.2 (red).(yellow/orange) – 8.2 (red).3.3. Any pH lower than 7 is acidic and above 7 Any pH lower than 7 is acidic and above 7 the solution is basic.the solution is basic.4.4. If the CO If the CO22 is used for photosynthesis and is used for photosynthesis and releases Oreleases O2 2 gas, then the liquid will return to its gas, then the liquid will return to its original color (a reddish-pink). original color (a reddish-pink).

Phenol RedSolution

Phenol RedSolution Phenol Red

SolutionPhenol Red

Solution

TestTube

A

TestTube

B

TestTube

C

TestTube

D

Wrap in Foil Wrap in Foil

Procedure:Procedure:

• 1.1. Put on safety goggles. These must be Put on safety goggles. These must be worn at all times. worn at all times.

• 2.2. Take four test tubes and label them A Take four test tubes and label them A through D. Also, label them with your groups through D. Also, label them with your groups name and period using the China markersname and period using the China markers

• 3.3. Find the phenol red solution in a 250-mL Find the phenol red solution in a 250-mL flask. flask.

• 4.4. Gently Gently blow through the straw. Keep blow through the straw. Keep blowing until there is a significant change in blowing until there is a significant change in the appearance of the phenol red solution. the appearance of the phenol red solution.

• 5. When your solution has changed color 5. When your solution has changed color fully (approximately 2 minutes), pour this fully (approximately 2 minutes), pour this solution into each test tube. You want to fill solution into each test tube. You want to fill each test tube approximately half-full with each test tube approximately half-full with the solution. Carefully put on the parafilm.the solution. Carefully put on the parafilm.

• 6. Record your observations in a data table 6. Record your observations in a data table in your laboratory notebook. in your laboratory notebook.

• 7. Label each of your test tubes according 7. Label each of your test tubes according to the letters indicated in the data table. to the letters indicated in the data table. Be Be sure to put your group’s name on the sure to put your group’s name on the labels too!labels too! Now add an Now add an elodea plantelodea plant to to the specified test tubes. Add the elodea to the specified test tubes. Add the elodea to A and B. A and B.

• Tubes A & C (requiring light) should be Tubes A & C (requiring light) should be placed in the test tube racks. placed in the test tube racks.

• Test Tubes B & D (in the dark) need to be Test Tubes B & D (in the dark) need to be wrapped COMPLETELY in FOILwrapped COMPLETELY in FOIL. .

8. After 24+ hours, examine each test 8. After 24+ hours, examine each test tube, and note any change in the tube, and note any change in the appearance of the appearance of the phenol redphenol red solution. solution.

9. Record your observations in the data 9. Record your observations in the data table.table.

Data Data TableTable

Test Tube: Test Tube: Initial color of Initial color of Phenol Red Phenol Red solution: solution:

Color of solution Color of solution after blowing: after blowing:

Color of solution Color of solution after 24 hours: after 24 hours:

A – Placed in the A – Placed in the Light with Elodea Light with Elodea RedRed OrangeOrange RedRed

B – Placed in the B – Placed in the Dark with Elodea. Dark with Elodea. RedRed OrangeOrange OrangeOrange

C – Placed in the C – Placed in the Light without Light without Elodea Elodea

RedRed OrangeOrange OrangeOrange

D – Placed in the D – Placed in the Dark without Dark without Elodea.Elodea.

RedRed OrangeOrange OrangeOrange

Concentration Of CO2

Con

cen

trati

on

Of

O2

For every 6 CO2 molecules taken in by the plant, 6 O2 molecules are released

Color change due to acidic level of CO2 in solution.

AcidicBasic