WILD WINGS HEADING SOUTH

Classroom Activity: Modeling the Greenhouse Effect

This hands-on, scientific experiment helps students understand how atmospheric gases can turn our planet into a giant greenhouse, causing global warming.

| Introduction | Objective | Concept | Time | Materials | Preparation | Procedure |
| Evaluative Questions | Extensions |

Introduction:

In this experiment, students discover that air trapped in a closed container will heat up more than the air in an open container when both are exposed to the same amount of energy from a light bulb. In a comparable (but different) way, the carbon dioxide in the atmosphere acts as a heat trap for energy from the sun. Students expose to the light two cut-off soda bottles, one of which has its top covered with plastic wrap to simulate the barrier of greenhouse gases in our atmosphere.

Objective:

Students test a physical model analogous to the atmospheric greenhouse effect. (See the diagram of the model.)

Concept:

Physical barriers can trap or slow heat exchange, causing increase in temperatures.

Time:

One to two 40-minute sessions.

Materials:

For each team of four students:

• two 2-liter clear plastic soda bottles
• two thermometers
• three strips of thin cardboard, 1" x 2"
• four cups potting soil
• two colored markers
• one medium rubber band
• one piece of 20" x 20" plastic wrap
• masking tape
• one 100-watt light bulb
• one clip-on or unshaded desk lamp
• one extension cord (if needed)
• one wooden block for securing lamp (if needed)
• four pieces of 1/4" graph paper

(NOTE: Lights are not necessary if this activity is done on a sunny day. The experiment can be placed on a window sill in direct sunlight.)

Preparation:

1. Have students bring in plastic soda bottles, enough for each team of four to have two bottles. Remove labels and cut off the tops. (See the diagram of the model.)

2. Gather the materials listed above. Cut the 1" x 2" pieces from a thin piece of cardboard, three for each team.

3. Prepare graph paper as follows: Working left to right along the bottom, label the horizontal axis 1-30 minutes. Then, from bottom to top on the left side of the paper, label the vertical axis 60^o-104^oF. Each team will need four sheets prepared in this fashion.

Procedure:

First 40-minute Session:

1. Discuss the concept of global climate change and global warming as outlined in the background page, emphasizing how greenhouse gases form a shield-like barrier around the planet, like the glass of a greenhouse. Brainstorm with students the sources of greenhouse gases.

2. Tell students that during the next class session they will get a chance to build a model that will test how a closed system, like a greenhouse, can actually make the temperature of the atmosphere increase. (See the diagram of the model.) They will test a closed system against an open system (the uncovered bottle) to see the different effects on heat absorption and retention. Show the students the supplies and describe the model. Have students sketch a diagram of the model to ensure they understand the set up, and answer any questions regarding its construction so that the next session will go smoothly.

Second 40-minute Session:

1. Divide students into teams of four and distribute graph paper (four pages/group); be sure students know how to graph their results.

2. Distribute materials for building the model.

3. If using the lights, have students assemble the lamps and stands using the blocks to secure them. Test to be sure all lights are working.

4. Tape the thermometers and cardboard strips on the inside of the bottles as shown. It is important that each thermometer's face points toward the outside of the bottle and is positioned away from the light source.

5. Place two cups of soil in each bottle.

6. Using the rubber band, secure the plastic wrap on one of the bottles.

7. Place bottles at equal distances two inches from a sunlit window (or two inches from the lamps if using lights). Use one of the 1" x 2" cardboard pieces as a spacer.

8. Have students predict what they think will happen.

9. Each student should note the initial (starting) temperature for both bottles on a separate piece of graph paper.

10. Graph the temperature in each bottle every two minutes for 30 minutes. Remove from sunlight or turn off light.

11. Using different colored markers, connect the points for each temperature reading.

Evaluative Questions:

How do your results compare with the rest of the class?

Do all the tests show the same results?

How can differences be explained?

Why do we need to build models like this to test an atmospheric phenomenon?

Extension:

Have students use a large sheet of tracing paper to trace the outline of the U.S. from the National Wildlife Refuge System map included in your box of materials. Next, have students draw another line on the tracing paper approximately 1/8" inside of the first line. The second line is a theoretical representation of a new shore line, created after the level of the ocean has risen six feet. Now have students overlay the paper on the map and count the number of National Wildlife Refuges that lie between the two lines. These are the refuges that could, in theory, be affected by a six-foot rise in sea level.

How many refuges are affected?

What could happen to coastal wetlands?

Would some be destroyed?

How might a rise in sea level be beneficial to coastal wetlands?

How might the food webs in these habitats change?

Will migrating birds be affected?

Are river systems influenced by a sea level rise?

What other consequences could there be of a six-foot rise in sea level?

(Potential answers: Coastal groundwater supplies threatened, more damage from storms, coastal communities would be forced to move.)

"Modeling the Greenhouse Effect" is modified and adapted from Session 2 in Global Warming and the Greenhouse Effect, a teacher's guide in the Great Explorations in Math and Science (GEMS) series, and used with permission.

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