Sci-ber Text - 9th Grade

Earth's Energy - Modeling the Greenhouse Effect

On a global scale, carbon dioxide, water vapor, and other gases present in the atmosphere are similar to the glass in a greenhouse. Ultraviolet radiation from the sun (having a short wavelength) can pass through the glass. Once inside the greenhouse, the ultraviolet radiation is absorbed by soils, plants, and other objects. Upon absorption, it becomes infrared radiation or heat energy having a shorter wavelength. Because of this, infrared radiation cannot escape through the windows. The windows act like a large blanket in which they reradiate the infrared energy back into the greenhouse. This phenomenon naturally causes the overall temperature within the greenhouse to increase. See Figure 1.

The same gases that create a greenhouse (warming) effect, can also create a cooling effect. How is this possible? Refer again to Figure 1. Much of the ultraviolet energy from the sun also gets scattered, absorbed, and reflected by carbon dioxide, water vapor, volcanic dust, solid particulates and aerosols created by humans, methane, and more. The solar energy that is reflected by the mentioned items, does not pass through the troposphere and does not allow for heat generation upon striking Earth's surface. This causes a cooling effect. An increase in carbon dioxide and other greenhouse gases eventually can create a cooling effect which could possibly alter weather and climates.

During this investigation, you will create a model demonstrating the greenhouse effect. The experiment involves crteating a greenhouse environment of carbon dioxide within a container. The investigation provides evidence that carbon dioxide can prevent or slow heat energy from entering an experimental container. You will measure temperature variations caused by the carbon dioxide atmosphere at the surface of the container and inside the container for data.

Materials:

Empty fish aquariam or a large beaker or flask
Dry ice
Gloves or tongs
Safety glasses
Heat lamp
Two thermometers (Celsius or Farenheit)
Styrofoam cup of water

Procedure:

Allow both thermometers to acclimate to room temperature.
Tape one thermometer to the top of the container.
Tape the second thermometer inside the container, near the bottom.
Place a heat lamp over the container.
Turn on the heat lamp.
After three minutes, record the temperature of both thermometers.
Keep the heat lamp on and place a chunk of dry ice into the cup of water and place the cup into the aquarium.
Allow the CO₂ vapor to fill the container.

While this is happening, observe the temperature reading of the outside thermometer and the inside thermometer if you can see it.

When the CO₂ vapor begins to subside, record the temperature of both thermometers and compare them.
Leave the heat lamp on and allow all of the CO₂ to leave the container.
Three minutes later, record the temperature of the two thermometers.
Make observations and conclusions about this experiment.

Safety concerns: Be sure to follow all eye and vision, and chemical safety rules that are specified by your teacher and in all general laboratory experiences. Handle the dry ice only while wearing gloves or using the tongs. Do not place the dry ice in a closed container.As with all science lab activities, the most important safety rule is to follow all teacher directions.

Analysis:

Which of the two thermometers had the highest reading after the carbon dioxide had filled the container? Answer
What happened to the temperature inside of the container as the carbon dioxide filled the container? Answer
If greenhouse gases become too thick in Earth's atmosphere, describe two major effects that they can have on Earth. Answer
Besides carbon dioxide and water vapor, other greenhouse gases and particles that can decrease Earth's air temperature include; methane, aerosols, and solid particulates. What are some natural and manmade processes that produce these? Answer

Extension:
Conduct the suggested activity of this unit again, however, use some temperature probes and Texas Instrument CBL® or a LAB PRO® by Vernier. Follow the same procedure you used for this unit.