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'''Carbon dioxide''' in an odorless, invisible [[gas]] formed by the [[combustion]] of [[hydrocarbon]]s, both nataurally, in the human body, and artificially, as fuel. It is one of the human body's major waste products, being excreted through exhalation.   

'''Carbon dioxide''' in an odorless, invisible [[gas]] formed by the [[combustion]] of [[hydrocarbon]]s, both nataurally, in the human body, and artificially, as fuel. 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 generate [[oxygen]].  Plants use carbon dioxide in [[photosynthesis]].

It is used by plants in the process of [[photosynthesis]] to generate [[oxygen]].

At room temperature, it is a gas. It becomes solid at extremely cold temperatures, 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>

At room temperature, it is a gas. It becomes solid at extremely cold temperatures, 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>