Photosynthesis:
Water Weed Virtual Lab
Name
_________________________________
Teacher
_________________________________
Period
_______________
Date
_______________
Due Date _______________
1
Part I. Background
Photosynthesis is the process by which green plants, some bacteria, and some protists use
the energy from sunlight to produce glucose.
The overall chemical reaction can be written:
Light + 6H2O + 6CO2  C6H12O6+ 6O2
The above chemical equation translates to:
Light plus six molecules of water plus six molecules of carbon dioxide produce one
molecule of glucose plus six molecules of oxygen.
The diagram to the left shows a
typical green plant undergoing
photosynthesis.
Used (reactants):
Produced (products):
We cannot directly observe photosynthesis occurring in a plant. Therefore, we must collect
indirect evidence of the process of photosynthesis. To collect this evidence, we must see if
the plant is using up reactants or releasing products of photosynthesis. Since gases, such
as carbon dioxide and oxygen, are colorless and odorless, we cannot see or smell their
presence without the help of an indicator. However, when a plant is in water, bubbles
indicate that a gas is present.
What gas would be present in bubbles produced by an aquatic plant, such as Elodea?
________________________
Objective: To determine the effect of three factors (light intensity, light color, and CO2 level)
on the rate of photosynthesis
Rate of photosynthesis = # O2 bubbles/30 sec
2
Computer Simulation Website:
http://www.saddleworth.oldham.sch.uk/science/simulations/waterweed.htm
PART II: The Effect of Light Intensity on Rate of Photosynthesis
Directions: Set the simulator to a colorless light and a CO2 level of 6.0. Adjust to the level
of light intensity to complete the data table.
Problem/Question:
_______________________ _________________________________________________________________
Hypothesis (If…then…):
_________________________________________________________________________________________
IV
______________________________
DV ______________________________
Constants ______________________________________________________________________________
Light Intensity Level
1.0
2.0
3.0
# O2 Bubbles/30 sec
(Light=Colorless | CO2= 6.0 )
* Based on the data, what
light intensity level results in
the fastest rate of
photosynthesis?
______________________
4.0
5.0
6.0
7.0
8.0
9.0
Line Graph:
Graph your results
on the paper
provided.
10.0
State the relationship between light intensity and rate of photosynthesis.
__________________________________________________________________________________________
__________________________________________________________________________________________
3
PART III. The Effect of Light Color on the Rate of Photosynthesis
Directions: Set the simulator to a 6.0 light intensity level and a 6.0 CO2 level. Adjust the
colors to complete the table.
Problem/Question:
__________________________________________________________________________________________
Hypothesis (If…then…):
__________________________________________________________________________________________
IV
______________________________
DV
______________________________
Constants ______________________________________________________________________________:
Light Color
# O2 Bubbles/30 sec
(Light Level=6.0 |CO2=6.0)
* Based on the data, what
color of light results in the
fastest rate of
photosynthesis?
______________________
Red
Blue
Green
Bar Graph: Graph
your results on the
paper provided.
Colorless
State the relationship between light color and rate of photosynthesis.
__________________________________________________________________________________________
__________________________________________________________________________________________
4
PART IV. The Effect of CO2 Level on Rate of Photosynthesis
Directions: Set the simulator to a 6.0 light intensity level and a colorless light. Adjust the
CO2 levels to complete the table.
Problem/Question:
__________________________________________________________________________________________
Hypothesis (If…then…):
__________________________________________________________________________________________
IV
______________________________
DV
______________________________
Constants ______________________________________________________________________________
CO2 Level
0.0
# O2 Bubbles/30 sec
(Light Level=6.0 |light=colorless)
* Based on the data, what
level of CO2 results in the
fastest rate of
photosynthesis?
______________________
1.0
2.0
3.0
4.0
5.0
6.0
7.0
Line Graph:
Graph your
results on the
paper provided.
8.0
9.0
10.0
State the relationship between CO2 level and rate of photosynthesis.
__________________________________________________________________________________________
__________________________________________________________________________________________
5
PART V. Analysis
1. Based on the simulation, identify the factors that affect the rate of photosynthesis in a
plant. Identify an additional factor, not used in this lab, which might affect the rate of
photosynthesis in plants.
__________________________________________________________________________________________
__________________________________________________________________________________________
__________________________________________________________________________________________
2. Based on the data, which level of CO2 results in the fastest rate of photosynthesis?
Explain why this level results in the fastest rate of photosynthesis.
__________________________________________________________________________________________
__________________________________________________________________________________________
3. Write the chemical equation for photosynthesis.
__________________________________________________________________________________________
4. How do the gas bubbles indicate the rate of photosynthesis?
__________________________________________________________________________________________
6. Why is it important that you keep two variables constant (such as light level and color)
while you test how a third variable (CO2 Level) affects photosynthesis?
__________________________________________________________________________________________
__________________________________________________________________________________________
Application: How might the information gained from this lab apply to a real-life situation?
__________________________________________________________________________________________
__________________________________________________________________________________________
6