Name: __​Josh Harmon​______________ Date: _​4/24/17​_______________________

Student Exploration: Photosynthesis Lab

Vocabulary​:​ carbon dioxide, chlorophyll, glucose, limiting factor, nanometer, photosynthesis,

wavelength

Prior Knowledge Questions ​(Do these BEFORE using the Gizmo​.)

● To survive, what gas do we need to breathe in?

___​Oxygen​________________________________

● Where is this gas produced? ____​Carbon Dioxide​_____

Gizmo Warm-up
During ​photosynthesis​, plants use the energy of light to
produce ​glucose​ (C​6​H​12​O​6​) from ​carbon dioxide​ (CO​2​),
and water (H​2​O). Glucose is a simple sugar that plants use
for energy and as a building block for larger molecules.

A by-product of photosynthesis is oxygen. Plants use some

of the oxygen they produce, but most of it is released. In the
Photosynthesis Lab ​Gizmo™, you can monitor the rate of
photosynthesis by measuring oxygen production.

1. Observe the left pane closely. What do you think the bubbles are? __​CO2

molecules​__________________

2. Select the BAR CHART tab. On the graph, notice the ​Oxygen production ​bar. Move the
Light intensity ​slider back and forth. How does light intensity affect oxygen production?

______​If the light intensity is high and the CO2 level is high then more oxygen is
created.​___________________________________________________________________

3. Experiment with the vertical ​Temperature​ slider (upper left) and the ​CO​2​ level​ slider.

A. How does temperature affect oxygen production? _​If the temperature is too high or
too low, no oxygen will be produced.​__________________________
 ___________________________________________________________________

B. How does CO​2​ level affect oxygen production? _​If the level of CO2 is higher, then
there is a greater chance that the amount of oxygen produced will also be high.
_____________________________

___________________________________________________________________

C. How does oxygen production relate to the rate of photosynthesis? ___​If the oxygen
production rate is high then then rate of photosynthesis will be quicker because the
more elements needed to creater photosynthesis, the faster the process will
go​.___________

___________________________________________________________________
 Get the Gizmo ready​:
Activity A:
● Be sure that the BAR CHART tab is selected.
Ideal conditions
● Turn on ​Show numerical values​.

Question: In the Gizmo, what are the ideal conditions for photosynthesis?

1. Form hypothesis​: During photosynthesis, light energy is used to synthesize carbon dioxide
(CO​2​) and water (H​2​O) into glucose (C​6​H​12​O​6​) and oxygen (O​2​). The complex series of
chemical reactions is summarized by the following formula:

6CO​2​ + 6H​2​O + light energy → C​6​H​12​O​6​ + 6O​2

In the Gizmo, what light intensity and CO​2​ level do you think will maximize the rate of

photosynthesis? __​The highest light intensity and CO2 level will maximize the rate of

photosynthesis.​_________________________________________________

2. Experiment​: Use the Gizmo to find the ideal conditions for photosynthesis. Use any method
you like. When you think you have the answer, list the conditions below.

Temperature Light intensity CO​2​ level Oxygen production

29 (C) 65% 780 (ppm) 36.7 (mL/h)

3. Revise and repeat​: One way to test if you’ve found the ideal conditions is to change each
variable slightly from the value that you recorded above. If the oxygen production decreases
with each change that you make, it is likely you have found the ideal conditions. If a small
change causes oxygen production to increase, continue to experiment.

If necessary, revise your numbers in the table above.

4. Think and discuss​: Think about the process of finding the ideal conditions.

A. Why would it be hard to find the ideal light intensity if the temperature were very hot

or cold? __​Due to the extrerme temperatures, the bubbles can not be created,

therefore decreasing oxygen production. No matter how much light you would put,
 the temperature is so extreme that it would make it difficult to find a light setting that

would help create the

bubbles.​__________________________________________________________

___________________________________________________________________

B. Why would it be hard to find the ideal CO​2​ level if the light intensity were very low?

__​It would be hard to find an ideal CO2 level if the light intensity was low because

light is a main ingredient in photosynthesis. CO2 and light work together to help

create photosynthesis, so one can not supply without the other and if one is low it is

difficult to find the other.​_______________________________________________

___________________________________________________________________
 Get the Gizmo ready​:
Activity B:
● Select the COLOR tab and the BAR CHART tab.
Colored light ​ emperature t​ o 24°C, the ​Light intensity
● Set the T
to 90%, and the ​CO​2​ level ​to 1,000 ppm.

Introduction: ​Plants use a green pigment called ​chlorophyll​ to absorb light and convert its
energy into a form that the plant can use. Chlorophyll gives plants their green color.

Question: What color of light is the best for photosynthesis?

1. Observe​: The color of a light wave is determined by its ​wavelength​. On the COLOR tab,
slowly drag the ​Light wavelength ​slider back and forth and observe the effect on oxygen
production. How does the color of light affect the rate of photosynthesis?

___​If the color of light is close to end of the spectrum on both sides , then the rate of
photosynthesis will be quicker because more oxygen is produced when it is on colors like
Orange, Yellow, and
Blue._________​__________________________________________________________

_________________________________________________________________________

2. Form hypothesis​: Which color of light do you think will maximize the rate of photosynthesis?

_​_If the color is blue, is will maximize the rate of photosynthesis beacause it is a darker color
and able to absorb more light than licghter
colors.​____________________________________________________________________
___

3. Gather data​: Set the ​Light wavelength ​to 400 nm. (The symbol “nm” stands for
nanometers​. A nanometer is a billionth of a meter.) Visible light ranges from 400 to 700 nm.

On the TABLE tab, click ​Record data​. Then set the ​Light wavelength ​to 420 nm, and
repeat. Continue recording data in the Gizmo every 20 nm until the wavelength is 700 nm.

4. Make a graph​: Select the GRAPH tab and select

Wavelength​. Sketch the graph in the space at right.

A. Which colors were absorbed best by the

plant? ________​Blue and

Orange​______________________
 B. Which colors were absorbed worst?

__​Green and yellow​__________________

5. Think and discuss​: When we look at a leaf, we see the colors of light that are reflected off its
surface. How does this explain the relatively low flow of oxygen in green light?

___​The chlorophyll in the plants give it its green color because it can not absorb oxygen
which will cause a decrease in the flow of oxygen in green
light.​_____________________________________________________________________
_

_________________________________________________________________________
 Get the Gizmo ready​:
Extension:
● Select the WHITE tab and the BAR CHART tab.
Limiting factors
● Turn on S​ how numerical values​.

Introduction: ​Photosynthesis requires light, water, and CO​2​ to work. When one of these factors
is in short supply, it is called a ​limiting factor​. Temperature can also be a limiting factor when it
is too hot or too cold for photosynthesis to work well.

Question: What is the effect of limiting factors on photosynthesis?

1. Observe​: Set ​Temperature ​to 24°C, ​Light intensity​ to 50%, and ​CO​2​ level​ to 200 ppm.

A. Move the ​Temperature ​slider up and down. Were you able to increase oxygen

production? ____​No (decrease from current level)​________________ (Return the

slider to 24°C when finished.)

B. Move the ​Light intensity ​slider back and forth. Were you able to increase oxygen

production? ____​No (decrease from current level)​_________________ (Return the

slider to 50% when finished.)

C. Move the ​CO​2​ level ​slider back and forth. Were you able to increase oxygen

production? ___​Yes​__________________ (Return the slider to 200 ppm when

finished.)

2. Analyze​: In this situation, what was the limiting factor? _____​CO2

Level​___________________

How do you know? ____​CO2 was the only variable in this experiment, when increased the
oxygen would also increase and when decreased would also
decrease.​_____________________________________________________

_________________________________________________________________________
3. Challenge​: In each of the situations below, use the Gizmo to find the limiting factor.

Temperature Light intensity CO​2​ level Limiting factor

25°C 60% 700 ppm Temperature
15°C 20% 200 ppm Temperature
30°C 50% 400 ppm Temperature.

4. Think and discuss​: Suppose you were a farmer trying to grow plants in a greenhouse. Why
would it be important to know what the limiting factor is?

___​This way you would know what you would need to which condition affects the growth of
his/her’s plants the
most​._____________________________________________________________________
_

_________________________________________________________________________