Materials

• 2 - 2 liter pop bottles with caps (remove company plastic logo)
• erlynmeyer flask with 1-holed rubber stopper
• 1 foot of 1/2" diameter rubber tubing to fit through rubber stopper
• alka seltzer tablets to generate CO₂
• light source (desk lamp with 100+ watt bulb)
• 2 -  thermometers or CBL with 2 temperature probes

    (In this version, we give very specific directions as to how to carry out the lab.  Being inquiry, however, it is very important that the students create their own laboratory procedure.  Therefore, there is a STUDENT LAB PAGE that does not give a step by step procedure for testing the hypothesis.  You can print this one out to give to your students.  It is up to the instructor to determine how much information to give the students.)

    Before you begin, get all of your materials, read through the lab carefully and create your data table.

1.  Dry both bottles thoroughly because water vapor is also a greenhouse gas.

2.  Drill 1 hole in the side of each bottle.  This hole should be placed 3" from bottom.  The hole should be just big enough that thermometer fits through snuggly.

3.  Cap one of the bottles -- this is the control. (Set aside for now.)

4.  Slide rubber tubing through hole in the side of second bottle.  Connect other end to 1-holed rubber stopper.

5.  Place 2 alka seltzer tablets in E. flask.  When ready, add cool water and place rubber stopper over the flask.  Flask will begin to generate CO₂.

6.  Allow carbon dioxide gas to enter bottle.  Do not cap.  Carbon dioxide gas should displace most of the air in the bottle.  Not all of the air needs to get out.  All you want is a CO₂ enriched environment.

7. When bubbling in flask slows down, remove tube and cap bottle.  Slide thermometers into holes of both bottles.

8.  Set each bottle equal distance from "sun"  (light source)

9.  Turn on "sun" and begin measuring the temperature of each bottle every minute for 60 minutes.
 

Analysis

1.  Create a table that will organize and display your data.  Remember to:

• Display your data in an organized table that is easy to understand.  Place a heading on each column of the data table.   Place the x axis information in the left-hand column and the y axis information in the right-hand column.
• Record all measurements as accurately as possible.
• Label all data with correct units.

•  use different colors for the graphs of temperature of each bottle.
•  label your x axis (independent variable) with time in minutes and your y axis (dependent variable) with temperature in Celsius
• determine the range of measurements and create the graph to appropriate size
• give your graph a title

• Write a paragraph that explains what you concluded from your data and why you drew that conclusion.
• Restate your hypothesis and use data from your experiment to support it.

You may use drawings and diagrams to help explain any of your answers.

1.  Compare the temperature of the atmosphere in bottle #1 to temperature in bottle #2.

2.  What is your explanation of why the temperatures in both bottles were not the same?

3.  Would it make any difference if you used some other gas besides CO₂?  Explain.

4.  What other gases could you use to get similar types of results?

5.  How does this investigation relate to the concern about global warming?

6.  If you were to redo your experiment, how would you improve it?

7.  Did performing this investigation lead to other questions you have in relation to global warming and greenhouse gases?

Woodrow Wilson Leadership Program in Environmental Science lpt@www.woodrow.org
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