Rate of Photosynthesis

Background (write a paragraph)

1. Where in the plant cell does photosynthesis occur?

2. What is the purpose of photosynthesis?

3. Write the general equations for photosynthesis. Identify reactants and products of the reaction.

4. What factors may influence the rate of photosynthesis?

Problem

The purpose of this lab is to investigate the influence of light intensity on the rate of photosynthesis. Write the problem.

Hypothesis

Write a hypothesis for this experiment using the “If…then…” format.

Materials

Large test tube / 0.5% sodium bicarbonate solution / Lamp / Thermometer
Plant sample / Watch with a seconds hand / Meter stick / Heat sink

Procedure

  1. Obtain a plant sample.
  2. Place the plant sample in a large test tube.
  3. Completely cover the plant sample with 0.5% sodium bicarbonate solution.
  4. Construct the set-up demonstrated in class. The initial set-up should be at the furthest distance you are testing.
  5. Turn on the lamp and wait five minutes. This will allow the system to reach equilibrium.
  6. Observe and record the number of bubbles generated in 5 min.
  7. Decrease the distance of the lamp from the large test tube by 20cm.
  8. Repeat steps 4 and 5 for a second distance.
  9. Decrease the distance of the lamp from the large test tube by 20cm.
  10. Repeat steps 4 and 5 for a third distance.
  11. Clean-up lab area and return supplies.
  12. Add your group’s data to the board and complete your data table.

Data

Distance from Lamp / 60cm / 40cm / 20cm
Bubbles Observed : Group Data
Bubbles Observed : Average of class data
Light Intensity = 1/ distance from the lamp (cm)

Graph

Graph the light intensity on the x-axis and the average number of bubbles (class data) for each distance on the y-axis. Is this a line graph or a bar graph?

Analysis questions

  1. Identify your independent and dependent variables as well as your control group and experimental group for this experiment.
  1. Why did we use 0.5% sodium bicarbonate solution (NaHCO3) in the lab? Hint: What does the plant need to photosynthesize?
  1. What gas was the plant producing in the lab?
  1. What is the relationship between light intensity and distance from the light source?
  1. Using your data table, how does the distance from lamp affect the rate of photosynthesis?
  1. Using your graph, how does the light intensity affect the rate of photosynthesis?
  1. Identify one other factor or variable that could influence the rate of photosynthesis? Describe an experiment to test the factor you identify.

Conclusion (write in a paragraph)

Refer to your experiment outcome, your data, to explain whether your hypothesis is supported or refuted. If your results deviate from the expected outcome, please explain how this may have happened (what are some sources of error?).