Goal: Students will grow a miniature “forest” to demonstrate the concept of terrestrial sequestration.

Objective: Students will…

• Increase understanding of the carbon cycle
• Recognize how plants can “trap” carbon dioxide
• Be able to explain and diagram the process of photosynthesis

Materials (For class of 28 working in groups of 4)

• Window with sun exposure or 7 --100 watt bulbs and sockets
• 1 bag of potting soil
• 7 sets of equipment to produce CO2 from previous lab
• 4 or 5 bags of radish seeds
• 7 clear tennis ball containers with lids
• 7 CO2 probes with software (Pasport by Pasco. Order through Sargent Welch).
• 7 computers to interface with CO2 probes and software
• Drill with large drill bit
• Computer printer
• 28 copies of Terrestrial Sequestration-Student Sheet

Time Required: 45-60 minutes

Standards Met: S1, S2, S3, S4, S6, DA1, DA2, DA3

Procedure:

PREP

• Drill holes in the tops of the tennis ball containers just large enough so that the CO2 probes fit snugly into them.
• At least one to two weeks before the start of the experiment, the students should set-up seven miniature “forests” by putting about 5 cm of potting soil in each clear tennis ball container and then planting 20-25 radish seed in each.
• Add a small amount of water to each container to just moisten the soil.
• Place the container in a sunny location and add water daily to keep the soil moist.

IN CLASS

• Setup the equipment necessary to produce carbon dioxide gas as in It’s a Gas! for the CO2 generator.
• Setup computers and probes.
• Get students into groups of 3 or 4.
• Hand out student sheets.
• Review the student lab procedure and expectations.
• Review clean up procedure.
• Circulate as students begin the lab.
• Students should continue to monitor the experiment and complete questions.
• Circulate to monitor clean up and disposal of materials.

Assessment:
Completed lab procedures
Completed student sheets

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Terrestrial Sequestration-
Student Sheet

Lab Directions:

• Load the CO2 probe software on the computer.
• Connect the CO2 probe to the computer and place the CO2 probe through the opening on the tennis ball container top.
• Prepare to start the probes software but don’t hit Start Recording yet.
• Begin producing CO2 from the CO2 generator.
• Place the rubber tubing from the CO2 generator near the bottom of the tennis ball container with the plants.
• Let the CO2 generator run for about 1 minute then quickly remove the tube and cap the container.
• Hit Start Recording on the computer.
• Put the container in direct sunlight or within 5 cm of a100-watt light.
• Monitor the amount of CO2 in the container for at least 10-15 minutes.
• At the end of the recording period, print out a graph and table of your results.
• Clean up all of the equipment according to your instructor’s directions.
• Answer the questions below.

Questions for Thought

1. Why did you not have to be concerned about all of the CO2 escaping from the container before you capped it?
   
   
   
2. What process was happening inside of the closed container in the light? Write the chemical equation for this process.
   
   
   
3. How might this small-scale model relate to the “real world?”
   
   
   
4. How would terrestrial sequestration help slow global climate change?
   
   
   
5. From your graph and data table, was the drop in the concentration of CO2 in the container the same for each minute? Why or why not?
   
   
   

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Terrestrial Sequestration-
Teacher Key

1. Why did you not have to be concerned about all of the CO2 escaping from the container before you capped it?
   
   CO2 has a density greater than air and would settle on the bottom of the container.
   
   
2. What process was happening inside of the closed container in the light? Write the chemical equation for this process.
   
   The process of photosynthesis was happening in the container. The chemical equation for photosynthesis is: 6 CO2 + 6 H2O C6H12O6 + 6 O2
   
   
3. How might this small-scale model relate to the “real world?”
   
   The plants represent trees or other green plants, the CO2 from the reaction represents CO2 added to our environment, and the 100-watt bulb represents energy supplied by the sun.
   
   
4. How would terrestrial sequestration help slow global climate change?
   
   Through the process of photosynthesis, green plants trap atmospheric CO2 and convert it to glucose and oxygen, therefore reducing the amount of greenhouse gases in our environment.
   
   
5. From your graph and data table, was the drop in the concentration of CO2 in the container the same for each minute? Why or why not?
   
   Answer will vary.
   

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