Modeling the Composition of Earth's Atmosphere

The Layer of Gases Surrounding Planet Earth Retained by Gravity

Jun 1, 2009 David R. Wetzel

This is a hands-on, minds-on approach to providing students with a concrete model of the earth's atmosphere to visualize the gases that comprise the atmosphere.

In the early 1800s, John Dalton was able to separate the major individual gases that comprises earth’s atmosphere. These gases were nitrogen, oxygen, and argon. In the 1920s, a new device called the spectrometer was used to identify the smaller trace gases that are also found earth’s atmosphere, such as ozone and carbon dioxide.

With exception of the small trace gases which vary from location to location around the world, scientists have developed an accepted model of all the gases in the atmosphere within people live and breathe. These gases include nitrogen 78.08 percent, oxygen 20.95 percent, argon 0.93 percent, and water vapor zero to four percent. The remaining gases are trace amounts of methane, neon, helium, krypton, carbon dioxide, ozone, sulfur dioxide, and nitrogen oxides also exist in earth’s atmosphere.

Modeling Earth’s Atmospheric Gases

The air containing the gases which comprise earth’s atmosphere is a clear invisible gas. This makes developing a concrete understanding of air’s composition difficult at best for elementary and middle school students, because this requires abstract thinking.

However, allowing them to construct a concrete model affords students the opportunity to visualize the different gases in the air helps reinforce the concept. The following activity allows students to construct a model to help them understand this relationship, while developing their science process skills.

Materials (per group)

• One Liter Clear Plastic Bottle
• 10 lbs White Rice
• Red, Yellow, Green, and Blue Food Coloring
• Scale
• Disposable Cups
• Stirring Sticks
• Paper Towels
• Funnel

Procedures

1. Remove the cap and fill the plastic bottle with white rice using the funnel.
2. Pour out the white rice and measure its weight.
3. Pour 10 percent of the white rice place on a paper towel.
4. Take 78 percent of the remaining white rice and pour it back into the bottle to represent nitrogen.
5. Take 21 percent of the remaining white rice and dye it yellow in a disposable cup and allow it to dry on a paper towel; this represents oxygen.
6. Take the remaining white rice and dye it green; this represents argon.
7. Count the number of grains of argon and take twice this number and dye them blue; this represents water vapor.
8. Dye the number white rice grains red which is equivalent to three percent of the argon rice grains; this represents carbon dioxide.
9. Dye the number of white rice grains purple (blue and red food coloring mixture) which is equivalent to one percent of the argon rice grains; this represents all the trace elements.
10. After the dyed grains of rice are dry, pour them into the plastic bottle with the white rice representing nitrogen.
11. Place the cap back on the bottle and shake vigorously, until the grains of rice are thoroughly mixed

Questions for Students with Sample Answers

While asking the following questions, allow students to make comparisons and analogies of the gases in the air using the model they just constructed. These inquiry based questions follow the guide of questions to ask students in science.

1. What is the purpose of the nitrogen in the air for humans?

It is an essential element of amino acids and proteins, along with nucleic acids (DNA and RNA).

2. What does the water vapor (blue) and carbon dioxide (red) represent in the model?

Greenhouse gases

3. What is the effect of these greenhouse gases?

Global warming

4. How do the greenhouse gases cause the earth to retain heat?

Greenhouse gases cause some of earth’s infrared radiated heat to be reflected back to earth to increase earth’s temperature.

5. What causes the greenhouse gases in earth’s atmosphere?

Human activities such as burning fossil fuels and coal for energy, cutting down forests, automobile pollution, and more.

6. Ozone is one of the trace gases in the atmosphere, what is its importance?

This gas absorbs 99 percent of the ultraviolet light that enters the earth’s atmosphere.

7. What causes holes in the ozone layer?

UV solar radiation severs chlorines from Chlorofluorocarbons and these unattached chlorines convert Ozone molecules into Oxygen molecules.

8. Methane is another one of the trace gases in the atmosphere, what is its importance?

This gas contributes to global warming by oxidizing the carbon dioxide and water in the atmosphere.

9. What are some sources of methane gas?

Natural gas, decay of organic matter in landfills, manure, waste water, and belching cows

Additional questions will develop during the discussion.

Making Connections with the Composition of the Earth’s Atmosphere

Students develop a better understanding of the air in which humans live and breathe using the concrete model of the atmosphere they constructed. This model stimulates critical thinking as they hold and visualize the relatively tiny proportion of the air that causes global warming. Students also make concrete visual connections regarding the amount of nitrogen and oxygen gases in the air they breathe. This lesson follows the guide of designing an effective lesson plan.

The copyright of the article Modeling the Composition of Earth's Atmosphere in Curricula/Lesson Plans is owned by David R. Wetzel. Permission to republish Modeling the Composition of Earth's Atmosphere in print or online must be granted by the author in writing.

Earth's Atmosphere

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