1. Activity 81: a producer’s source of energy
Challenge How do scientist’s study the role of light in photosynthesis?
KeyVocabulary:
Photosynthesis – the process of converting light energy into chemical energy.
Producer
Elodea- Aquatic plant that lives in freshwater

2. Read Introduction on Page E-50.
What evidence must have been required to discover the process of photosynthesis?
Evidence for water?
Evidence for Light?
Evidence for sugar being produced?
Evidence for use of Carbon dioxide and production of Oxygen?
These ideas were difficult for scientists too!! They had to investigate the uptake of CO2 and production of Oxygen

3. Is light necessary for photosynthesis?
What evidence do you have for your ideas?
How do you think you could collect evidence to support or disprove these ideas?

4. Photosynthesis – Word Equation *Copy into your journal*
sunlight
Carbon + Water  Glucose + Oxygen
Dioxide
What actually is the food?
6 CO H2O  C6 H12 O O2
GLUCOSE
(FOOD!)

5. What is BTB? – Record in your notebook!
BTB stands for Bromothymol Blue.
BTB is a carbon dioxide indicator
BTB turns green/yellow in the presence of carbon dioxide.

6. Predictions: DATA TABLE 1: Results with BTB Initial BTB color
Final BTB color
Color change show presence of what gas?
Person exhaled into BTB solution
Predictions:

7. Look at vials After your Hypothesis L= Light C= Control D= Dark
Predictions:
L= Will photosynthesize and the water will turn blue
C = Will remain the same
D= Will remain the same (No photosynthesis)

8. Should look like… Which is which?

9. Recording Observations – Part B
Exposed to Light
In the Dark
Initial
Final
Conclusion:

10. Conclusion:
In conclusion, we know that only our plant in the light photosynthesized because the BTB turned blue showing that the plant used the Carbon Dioxide and created Oxygen.

11. Analysis Questions
Discuss #s 1, 2 and 4 with your tables and record the answers in your journal.

12. Analysis #1
The vial with only the BTB was the control. It was used to compare the color change of the other vials.

13. Analysis #2
Leaf placed in light consumed carbon dioxide. Initially the BTB was yellow, indicating a higher level of CO2 . At the end of the experiment, the BTB solution was blue (or yellow-green).
This means that the leaf used the carbon dioxide in the solution for photosynthesis, releasing oxygen.

14. Analysis #4
Based on the results of this experiment, light is necessary for photosynthesis to occur.
The plant in sun changed the BTB solution back to blue (indicating it was using the carbon dioxide) and the plant in the dark did not.
The loss of carbon dioxide provides evidence that photosynthesis is occuring.