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We now offer the Cool It! card game in our Science Store. Cool It! is the new card game from UCS that teaches kids about the choices we have when it comes to climate change.
Here are four different ways chemists use to show a molecule of carbon dioxide. In the colored molecule models, carbon is light gray and oxygen is red.
Click on image for full size
Windows to the Universe original artwork by Randy Russell.

Carbon Dioxide - CO2

Carbon dioxide (CO2) is a kind of gas. There isn't that much carbon dioxide in Earth's atmosphere, but it is still very important. Carbon dioxide is a greenhouse gas. That means it helps trap heat coming from the Sun in our atmosphere through the greenhouse effect. Without carbon dioxide in our air, the Earth would be very cold.

Where does the carbon dioxide in our air come from? When humans and other animals breathe, we take in oxygen and breathe out carbon dioxide. We use the oxygen to get energy from food - this is called respiration.

Burning things also makes lots of carbon dioxide. Natural fires like forest fires make carbon dioxide. Things that humans burn make CO2, too. The smokestacks of factories that burn coal give off carbon dioxide. The engines of cars, trucks, and buses also pump carbon dioxide into the air. They sometimes give off another gas, carbon monoxide, too.

Earth isn't the only place where carbon dioxide is important. Most of the atmosphere of Venus is CO2. The atmosphere of Mars is also mostly carbon dioxide. If carbon dioxide gets really cold, it can freeze into a solid. This kind of ice is called "dry ice". The polar ice caps on Mars are partly made of dry ice!

Last modified October 15, 2011 by Jennifer Bergman.

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Cool It! Game

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Earth's Greenhouse Gases

Only a tiny amount of the gases in Earth’s atmosphere are greenhouse gases. But they have a huge effect on climate. There are several different types of greenhouse gases, but they all have something in...more

Earth's Greenhouse Effect

Not all of the energy from the Sun that arrives at Earth can leave easily. After being transformed into heat, it can become trapped by certain gases in the air. This is a natural process called the greenhouse...more

Oxygen

Oxygen (O2) is a kind of gas. A lot of the air you breathe is oxygen. That's a good thing, since we need oxygen to stay alive! About 4/5ths of the air in Earth's atmosphere is nitrogen (N2). Almost all...more

Respiration

You may have heard of photosynthesis. That's where a plant uses energy from the Sun's rays to make its own food. The opposite of photosynthesis is called respiration. The difference is that respiration...more

Air Pollution Sources

Air pollution comes from many sources. Some natural sources affect air quality. Volcanoes produce sulfur, chlorine, and ash. Wildfires make smoke and carbon monoxide. Cattle and other animals release methane...more

Carbon Monoxide - CO

Carbon monoxide is kind of gas. It is poisonous. A molecule of carbon monoxide (CO) has one carbon atom and one oxygen atom. Earth's atmosphere has a small amount of carbon monoxide in it. The carbon monoxide...more

Hydrocarbons

There is a group of chemicals called hydrocarbons. The molecules of hydrocarbons are made of hydrogen and carbon atoms. Most kinds of fuel have hydrocarbons in them. Hydrocarbons store energy. Coal, oil,...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA