Photosynthesis & Respiration Lab

What is the relationship between photosynthesis and respiration?

Part 1

Investigative Question: What will happen to a carbon dioxide solution of CO2 and water if a water plant is added?

Write your hypothesis:

“If _______________ then__________ because__________________________.”

*Get signed off by your teacher

MaterialsTest tubes x 4

Stoppers x4

Elodea (2cm) Foil

Test tube rack

Bromothymol BlueLamp

The Acid-Base Scale & Bromthymol Blue

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Most least least most

Acidic Neutral Basic

6 7 8

Water

CO2 in water

No CO2 in water,

Regular tap water

Distilled water

Protocol

1. Label your test tubes with your names and the letters A, B, C, and D.

2. Fill each 1/2 full with distilled water.3. Add 1 dropper of acid/base indicator

(bromothymol blue)

A B C DPer5 Per5 Per5 Per5

Name Name Name Name

4. Place a straw into Test Tube A.

5. Gently blow into the solution until it starts to turn yellow- STOP IMMEDIATELY when you see a change in color!!!

STOP!

A

A

6. Repeat Steps 4 & 5 for all test tubes& place 1 sprig of elodea into test tubes A & C.

A B C DPer5 Per5 Per5 Per5

Name Name Name Name

7. Then place stoppers on all test tubes.

A B C DPer5 Per5 Per5 Per5

Name Name Name Name

8. Wrap Test Tubes C & D with foil so that no light can get in.

A B C DPer5 Per5 Per5 Per5

Name Name Name Name

9. Place all test tubes on a test tube rack or holder and place in the tray that will go under a light.

A B C DPer5 Per5 Per5 Per5

Name Name Name Name

Predictions:

Test Tube

Color after 24 hours

pH = ? Why do you think this?

A

B

C

D

Original Data Table

Test

Tube

Color start

(pH = 6-, 7, 8+)

Color after 24 hours

(pH = 6-, 7, 8+)

A

B

C

D

Class Results: Color (pH) changes for Day 1

Group Tube A Tube B Tube C Tube D

1

2

3

4

5

6

7

Mode:

Part 1- Data Collection

1. Observe the results after 24-48 hrs.

2. Record data on data table.

Part 2

Investigative question: What is the role of light in photosynthesis? What might happen if the tinfoil was switched to test tubes A & B?

Write your hypothesis:

“If _______________ then__________ because__________________________.”

*Get signed off by your teacher

Identify the following in this inquiry:

• The manipulated variable _____________• Responding variable_________________• Controlled variables _________________

____________________

• Experimental control _________________• Purpose of the experimental control _____

__________________________________

*Get teacher signature

10. Wrap Test Tubes A & B with the foil so that no light can get in.

C D A BPer5 Per5 Per5 Per5

Name Name Name Name

11. Place all test tubes on a test tube rack or holder and place in the tray that will go into the greenhouse.

C D A BPer5 Per5 Per5 Per5

Name Name Name Name

Part 2 Data Table: pH after light/dark conditions reversed

Test Tube

Color after 24-48 hours

pH = ? Why?

A

B

C

D

Part 2 – Data Collection

• Record your results in your data table.

Analysis Questions Part 1:

1. Explain what happened to the pH of the solution for Test tube A. Why did you get these results?

2. How were these results different than test tube B? Why?

3. How were they different than C? Why?

4. And D? Why?

Analysis Questions Part 2 & 3:

1. What results changed as a result of switching the foil on the test tubes?

2. Why do you think this happened?

3. What is the role of light in photosynthesis?

4. Can plants do respiration? What evidence supports this?

5. What changes would you make to improve this lab and why?