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What is Carbon Dioxide? - Definition & Explanation

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  • 0:01 What Is Carbon Dioxide?
  • 1:20 Importance of Carbon Dioxide
  • 3:05 Other Uses for Carbon Dioxide
  • 4:35 Lesson Summary
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Lesson Transcript
Instructor: Wendy McDougal

Wendy has taught high school Biology and has a master's degree in education.

Carbon dioxide is a colorless, odorless gas found in our atmosphere, our bodies, and many other places. Learn more about this gas and take the quiz at the end of the lesson.

What is Carbon Dioxide?

You breathe it out every time you exhale. It puts the carbonation, or fizz, into your soda pop. Plants take it out of the air and use it to make food. And you may know it as dry ice, perhaps flowing across a stage as a theater prop. What is this versatile substance that is in our air, bodies, and even our drinks? It is a colorless, odorless gas known as carbon dioxide. In this lesson, we will learn more about where it is found and how we encounter it in our daily lives.

Before we look more closely at the variety of roles carbon dioxide plays in our lives, let's first explore it from a chemistry standpoint. If we break down the name of this gas, we can determine what it is made of. In a molecule of carbon dioxide, there is one atom of carbon bonded with two atoms of oxygen. The chemical formula for carbon dioxide is CO2, and a molecular model looks like this:

Carbon Dioxide Model
Model of Carbon Dioxide

If we were to take one of the oxygen atoms away, we would be left with carbon monoxide, or CO. Removing this one oxygen atom creates this extremely deadly gas. On the other hand, CO2 is harmless in reasonable amounts. It is a gas that is found naturally in our atmosphere.

Carbon Dioxide in the Air

The carbon dioxide in our air is crucial to plants and trees. Remember when we talked about plants using carbon dioxide to make food? Let's look at this process, which is called photosynthesis. Living organisms such as humans breathe in oxygen and release carbon dioxide. Plants do just the opposite: they take in carbon dioxide and release oxygen. The carbon dioxide they take in is used to make sugar, which oftentimes becomes our food. We can represent the process of photosynthesis in an equation:

Photosynthesis Equation
Photosynthesis Formula

In this equation, we know that CO2 represents carbon dioxide, and H2O is water. Using the sun's energy and a pigment found in green leaves called chlorophyll, plants produce glucose, which is a form of sugar. And the O2 is the oxygen gas that is released.

Unlike plants, we produce CO2 as a waste product that our bodies need to get rid of. This is handy for plants, as they must take it in to produce their food. Likewise, it works out well for us that plants give off oxygen to add this important gas to our atmosphere.

Most of the carbon dioxide in our atmosphere is the result of the burning of fossil fuels. When fossil fuels such as natural gas and coal are burned, CO2 is released. In fact, humans have been burning so many fossil fuels over the years that amounts of carbon dioxide in the atmosphere have gotten much higher than they used to be. The higher levels of CO2 are thought by some to have caused a general temperature increase around the earth because more heat gets trapped in the gases. This is known as global warming.

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