Virtual Waterweed LabIntroduction:A common way to determine how well a chemical reaction is happening is to measure how much of the products are being formed in a particular amount of time. There are two products to photosynthesis: Glucose and Oxygen. Since the glucose gets stored in the plant, it is difficult to measure. Oxygen, however, gets released from the plant. In water plants, this released gas produces bubbles. The better photosynthesis is working, the more oxygen is produced, the more bubbles! Let’s start by going to the website:

Directions:

  1. There are three variables you can adjust: light level, CO2 level and color of light.
  2. Once you have set up the variables as you want them, you will click start. Bubbles will start coming from the plant. It will count the number of bubbles that rise in 30 seconds time.
  3. EACH TEST MUST BE REPEATED 3 TIMES TO GET AN AVERAGE!!!

Part I: Determine the effect of wavelength on the Rate of Photosynthesis

Set the Light Level to 6.0, and CO2 Level6.0. Adjust the colors to complete the table.

Light Color / Number of Bubbles
(Light = 6.0 | CO2 = 6.0)
Trial 1 / Trial 2 / Trial 3 / Average
Red
Blue
Green
Colorless

Part II: Determine the Effect of Light Level on PhotosynthesisSet color of light to “colorless” and the CO2 level to 6.0. Adjust the level of light.

Light Level / Number of Bubbles
(Light = 6.0 | CO2 = 6.0)
Trial 1 / Trial 2 / Trial 3 / Average
1
3
5
7
9

Part III: Determine the Effect of CO2 Level on Photosynthesis

Now you will develop an experiment to test the effect of the level of CO2on the rate of photosynthesis.

Set up: Describe how the person should do the experiment. Include what conditions they should use for color, intensity and CO2 levels. Describe what they will be measuring. Write it in a stepwise procedure format.

Data Table: Using a ruler, create a blank data table complete with title and headings that a student could use to fill out when completing your experiment above. Use the tables for the previous experiments as models.

Conclusion: In the space below, make predictions about what they should expect to see. EXPLAIN why you made the predictions the way you did. If you are unsure, perform your experiment using the virtual lab and analyze the data that you get.

Discussion questions:

  1. Obtain a piece of graph paper.
  2. On the front, graph your averages from part I.
  3. On the back, graph your averages from part II.
  1. What was the dependent variable for all three experiments?
  2. What was the INDEPENDENT variable for each experiment?
  3. Part I:
  4. Part II:
  5. Part III:
  6. Write the overall chemical reaction for photosynthesis.
  7. Explain the role that each of the following has in photosynthesis:
  8. CO2
  9. Light
  10. Wavelength
  11. What are the bubbles you are measuring in this lab? Why do these bubbles indicate that photosynthesis is happening?

9. For each experiment two variables were NOT CHANGED while you adjusted the third variable.

a. What do we call a variable that is not changed during an experiment?

b. Why is it important to keep these the same?

10. Why is it better to do multiple trials and calculate an average?

Conclusion:

For each experiment, write a conclusion explaining why you got the results you did.

  1. Color of light: What were the best and worst colors for photosynthesis? Explain why
  1. Intensity of light: Which was the best and why?