This simple experiment serves as an introduction to the greenhouse effect. Students can see for themselves the effects of a greenhouse, and relate this understanding to what occurs in our atmosphere.
1. Help students understand the greenhouse effect as a physical phenomenon.
2. Use simple experimentation techniques including: observing and recording data, use of a control, drawing conclusions from results, use of a model.
For every group of (about) four students:
2 Small thermometers
1 Jar or other see-through container
1 Clock or watch
1 Copy of the worksheet
Sunlamp or access to a sunny area to perform the experiment
Group the students and distribute the materials. Each group should place their thermometers a few inches apart under the sunlamp or in direct sunlight.
Wait about three minutes so the thermometers will be giving accurate readings, and then have the students record the temperature readings on both thermometers as well as the time.
Each group should now place their jar over one of their thermometers, taking care that the jar does not cast a shadow over the uncovered one. If the thermometers are too large to remain horizontal inside the jars, it is fine to stand them against an inner side. Every minute, for ten minutes, the students should record the readings of both thermometers.
The air over the exposed thermometer is constantly changing, and as it gets warm it is replaced by cooler air. Because the air in the jar cannot circulate to the rest of the room, this air stays in the sunlight and gets warmer and warmer. A similar trapping of heat happens in the Earth's atmosphere. Sunlight passes through the atmosphere and warms the Earth's surface. The heat radiating from the surface is trapped by greenhouse gasses. Without an atmosphere, the Earth's temperature would average about 0F. This warming due to heat-trapping gasses is called the "Greenhouse Effect." Both the atmosphere and the jar allow light to enter, but then trap that energy when it is converted to heat. They work differently, however, because the jar keeps in the heated air, while the greenhouse gasses absorb radiative heat.
Students can graph their data. To simulate global warming, the experiment can be done using two jars, one filled with air and the other with carbon dioxide.
The Greenhouse Effect
1) Place the two thermometers in the sunlight for a few minutes to let them get warm.
2) Record the readings of both thermometers at the top of the columns.
3) Record the time next to the starting temperatures and place the jar over thermometer #1.
4) Every minute, record the readings of both thermometers without disturbing them.
Data Observation Number Thermometer #1 Thermometer #2 Time Start 1 2 3 4 5 6 7 8 9 10