Zakia D. Parrish, Ph.D.
Activity 1: Greenhouse Effect Pre-Instruction Essay
At the beginning of the unit, students will be asked to write an essay as to their thoughts on the greenhouse effect and whether they feel it is a real threat or media hype. They will be asked to revisit this position paper at the end of this subunit.
Activity 2: Greenhouse Gas Emission Graphs
Science regularly integrates the other core content areas: History, English, and Mathematics. Students will need to utilize their math skills to construct and interpret graphs of the release of several greenhouse gases and relate it to the changes in temperature experienced on Earth. This will require inter-department collaboration between the Science and Business teachers, who teach ninth graders to use Microsoft Office products. Students will be provided data from the US Inventory of Greenhouse Gas Emissions (16). Emissions data from 1990 - 2005 for three of the greenhouse gases covered in this subunit (fluorinated gases, methane, and carbon dioxide) and their various sources are provided. The students will be asked to construct one of the following two choices of graphs:
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1. Students can choose one gas and construct a graph comparing the emission levels from various sources of that gas.
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2. Students can construct a graph of the total emissions for all three gases and compare the emission levels between the different types.
Regardless of which graph they choose to construct, they will have to write an essay discussing the greenhouse gas(es), the sources, and the trends they observe in the graph. They will also be provided a graph of the average annual global temperature change and the atmosphere carbon dioxide concentration over the geological time scale of the last 150,000 years. They will be asked to discuss the spike in carbon dioxide levels that occurred in the 1800's and what they believe happened around that time to cause the increase. The desired responses are related to the Industrial Revolution, specifically the increased number of factories and the invention of the automobile. Additionally, one of the Science, Technology, and Society (STS) curriculum-embedded performance tasks on the Connecticut Academic Performance Test (CAPT) requires students to be able to utilize Microsoft Excel to create graphs illustrating the energy uses in Connecticut.
Activity 3: Greenhouse Effect Mini-Lab
Students will conduct a mini-experiment to track the effect of a greenhouse on temperature. It is desired that they infer that the effect of greenhouse conditions is similar to that of greenhouse gases in the atmosphere. They will also need to utilize their manual graphing skills and discuss the differences they observe.
Materials:
For each group of two or three students
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1 Two thermometers
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2 Clear plastic rectangular storage box (~ 6 quart size shoe box)
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3 Stopwatch
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4 Graph paper
Procedure:
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1. Set both thermometers outside in the sun and allow them to come to a stable temperature.
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2. Record the initial temperature.
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3. Place one thermometer in the plastic storage box so that the temperature can be read clearly through the box.
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4. Keep the remaining thermometer next to the storage box.
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5. Start the stopwatch and begin measuring the temperature readings on both thermometers at two minute intervals for fifteen to twenty minutes.
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6. Plot the change in temperature over time for both thermometers on the same graph.
Discussion Questions:
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1. At what point in time did the temperature inside of the storage box change dramatically compared to that outside of the box?
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2. Why do you think this occurred?
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3. How is the storage box similar to the Earth's atmosphere?
Activity 4: Carbon Dioxide Measurement Lab
Students will conduct a series of greenhouse gas experiments that require students to detect carbon dioxide production and utilize acid/base chemistry to quantify the amount of carbon dioxide produced. Prior to this subunit students will have learned about acids, bases, pH, and the use of indicators to classify substances. They will also have to compare and contrast the carbon dioxide levels from various sources and discuss alternative energy sources. The NASA Explores program has developed a laboratory experiment entitled "Detection of Carbon Dioxide" in which students determine the amount of carbon dioxide emitted from various natural and anthropogenic sources. The materials, teacher's notes, and procedure are listed below (17).
Materials:
For each group of two or four students
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- Five vials or test tubes
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- Graduated cylinder
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- Funnel straw
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- Marble-size piece of modeling clay
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- Four different colored balloons
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- Four twist-ties
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- 100- or 250-mL Erlenmeyer flask
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- Dropper bottle of bromothymol blue indicator solution
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- Dropper bottle of dilute household ammonia (1 part ammonia to 50 parts distilled water)
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- 100 mL vinegar
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- 5 mL baking soda
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- Safety goggles
Notes:
The air solution in vial A will not turn yellow. The level of CO 2 in air is too low to affect bromothymol blue.
Procedure
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1. Add 15 mL of water and 10 drops of bromothymol blue indicator solution to each vial or test tube. Label the vials A, B, C, D, and Control.
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2. Fill each balloon as follows until it has a 7.5 diameter.
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§ Sample A (Air) -- Use a tire pump to inflate the balloon to the required diameter. Twist the rubberneck of the balloon and fasten it shut with a twist tie. The tie should be at least 1 cm from the opening of the balloon. Record the color of the balloon used for this sample.
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§ Sample B (Human Exhalation) -- Have one team member blow up a balloon to the required diameter. Twist and tie the balloon, and record the balloon color.
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§ Sample C (Automobile Exhaust) -- Your teacher will supply you with this balloon. Record the color of the balloon.
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§ Sample D (Nearly pure CO 2) -- Put 100 mL of vinegar in the flask. Using a funnel, add 5 mL of baking soda. Let the mixture bubble for 3 seconds to drive the air out, and then slip the balloon over the neck of the bottle. Inflate the balloon to the proper diameter. Twist and tie the balloon, and record the color.
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3. Soften the clay, and wrap it around one end of the straw to make a small airtight collar that will fit into the neck of a balloon. The collar should look like a cone with the straw in its middle, and should be large enough to plug the neck of the balloon.
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4. Pick up Balloon A. Keeping the tie on it; slip the balloon's neck over the clay collar. Hold it against the collar to make an airtight seal. Place the other end of the straw into the vial of water and bromothymol blue labeled A. Have another partner remove the tie on the balloon, and slowly untwist the balloon. Keeping the neck of the balloon pinched to control the flow of gas, gently squeeze the balloon so the gas slowly bubbles into the solution.
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5. Repeat the same procedure with the other balloons and their respective vials. In some cases, the bromothymol blue solution will change color, from blue to yellow, indicating the presence of carbonic acid formed from CO 2.
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6. Analyze each of the samples by titrating them with drops of diluted ammonia. Ammonia neutralizes the carbonic acid. The bromothymol blue will return to a blue color when all the acid has reacted. Add drops of ammonia to each of the samples that turned yellow, carefully counting the number of drops needed until they are about the same color as your control. Record the results.
Discussion Questions
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1. Which samples had the most and the least carbon dioxide?
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2. Why didn't the air sample turn yellow?
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3. Why is automobile exhaust a concern?
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4. How could a city reduce the amount of CO 2 emissions?
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5. What alternative power sources could be used with cars?
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6. Why might it be difficult for the public to start using an alternative source?
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Why should we be concerned about global warming?
Activity 5: "An Inconvenient Truth"
Towards the end of the subunit students will be shown "An Inconvenient Truth". This should take approximately one 82-minute class period. Students will answer the following questions about the movie (18).
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1. What are the layers of the atmosphere?
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2. Which layer plays a role in global warming?
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3. What percent of solar energy is reradiated back?
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4. Which wavelength of light is trapped in the atmosphere by greenhouse gases?
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5. How can trapping infrared radiation by the earth's atmosphere be a
GOOD
thing?
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6. How can trapping infrared radiation by the earth's atmosphere be a
BAD
thing?
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7. Sketch the general trend of the "CO2 Level" versus time between 1958 and 2000 on the graph paper provided.
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8. Discuss the relationships you observe in the graph created above.
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9. During what time period did the levels of CO2 increase the most?
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10. What branch of science involves the study of ice and sediment cores?
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11. How much has the sea level risen over the last 100 years?
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12. What would be the result of the melting of the ice sheets in Western Antarctica?
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13. What are some natural sources of carbon dioxide?
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14. How much do they contribute to atmospheric carbon dioxide emissions?
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15. Which countries produce the most carbon dioxide emissions?
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16. What percentage of the global population do the populations of those countries make up?
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17. What is the Kyoto Protocol and why is it important?
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18. Why didn't the United States sign the Kyoto Protocol?
Activity 6: Greenhouse Effect Post-Instruction Essay
Finally, students will be asked to re-examine the essay they wrote at the beginning of the subunit. They will need to utilize the Internet to locate documentation to support their position on whether or not the greenhouse effect is a true danger. For this activity to be most effective, students should have a working knowledge of how to evaluate the reliability and credibility of websites. A CAPT-STS curriculum-embedded task that will provide the students with these skills should have been completed in a previous marking period.