Difference between revisions of "Carbon dioxide"
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| − | '''Carbon dioxide''' in an odorless, colorless [[gas]] formed by the [[ | + | [[Image:CO2phase.jpg|thumb|right|300px|[[Phase diagram]] for CO<sub>2</sub>]] |
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| + | '''Carbon dioxide''' in an odorless, colorless [[gas]] formed by the [[oxidation]] of [[hydrocarbon]]s, both naturally, in animals, and artificially, as fuel<ref>If not enough oxygen is present, [[carbon monoxide]] will also be produced, in a process called "incomplete combustion".</ref>. It is one of the human body's major waste products, being excreted through exhalation. | ||
| − | [[ | + | It is used by plants in the process of [[photosynthesis]] to create complex carbohydrates (cellulose and sugars), using water and the energy from sunlight. The waste product in this process is [[oxygen]]. |
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Each molecule of carbon dioxide has one carbon atom and two oxygen atoms, so its chemical formula is CO<sub>2</sub>. | Each molecule of carbon dioxide has one carbon atom and two oxygen atoms, so its chemical formula is CO<sub>2</sub>. | ||
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| + | At room temperature and atmospheric [[pressure]], it is a gas. It becomes solid at -78 ºC at standard atmospheric pressure, forming dry ice. When it thaws, it turns directly into a gas again (see [[sublimation]]). <ref>"Dry ice is frozen carbon dioxide. A block of dry ice has a surface temperature of -109.3 degrees Fahrenheit (-78.5 degrees C). Dry ice also has the very nice feature of sublimation -- as it breaks down, it turns directly into carbon dioxide gas rather than a liquid." [http://www.howstuffworks.com/question264.htm How Stuff Works] </ref> This can be seen from the phase diagram to the right, where at 1 atmosphere of pressure, there is no liquid state separating the solid and gas as temperature rises. | ||
CO<sub>2</sub> is one of the so-called [[greenhouse gas]]es. Heat-trapping by CO<sub>2</sub> has been observed on [[Earth]] and [[Venus]]. The extent of its role in the current increase in average global temperatures is a topic of active political, though not scientific, debate. | CO<sub>2</sub> is one of the so-called [[greenhouse gas]]es. Heat-trapping by CO<sub>2</sub> has been observed on [[Earth]] and [[Venus]]. The extent of its role in the current increase in average global temperatures is a topic of active political, though not scientific, debate. | ||
Revision as of 01:08, May 12, 2007
Carbon dioxide in an odorless, colorless gas formed by the oxidation of hydrocarbons, both naturally, in animals, and artificially, as fuel[1]. It is one of the human body's major waste products, being excreted through exhalation.
It is used by plants in the process of photosynthesis to create complex carbohydrates (cellulose and sugars), using water and the energy from sunlight. The waste product in this process is oxygen.
Each molecule of carbon dioxide has one carbon atom and two oxygen atoms, so its chemical formula is CO2.
At room temperature and atmospheric pressure, it is a gas. It becomes solid at -78 ºC at standard atmospheric pressure, forming dry ice. When it thaws, it turns directly into a gas again (see sublimation). [2] This can be seen from the phase diagram to the right, where at 1 atmosphere of pressure, there is no liquid state separating the solid and gas as temperature rises.
CO2 is one of the so-called greenhouse gases. Heat-trapping by CO2 has been observed on Earth and Venus. The extent of its role in the current increase in average global temperatures is a topic of active political, though not scientific, debate.
The Lewis structure indicates it has two double bonds:
References
- ↑ If not enough oxygen is present, carbon monoxide will also be produced, in a process called "incomplete combustion".
- ↑ "Dry ice is frozen carbon dioxide. A block of dry ice has a surface temperature of -109.3 degrees Fahrenheit (-78.5 degrees C). Dry ice also has the very nice feature of sublimation -- as it breaks down, it turns directly into carbon dioxide gas rather than a liquid." How Stuff Works