<unk>  (chemical formula:<unk>  is a chemical<unk> mpound<unk> mposed of two oxygen atoms<unk> valently bonded to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state. It is currently at a globally averaged<unk> ncentration of approximately 383 ppm by volume in the Earth's atmosphere, although this varies both by location and time.<unk>  is an important greenhouse gas because it transmits visible light but absorbs strongly in the infrared.<unk>  is produced by all animals, plants, fungi and microorganisms during respiration and is used by plants during photosynthesis. This is to make sugars which may either be<unk> nsumed again in respiration or used as the raw material for plant growth. It is, therefore, a major<unk> mponent of the carbon cycle.<unk>  is generated as a byproduct of the<unk> mbustion of fossil fuels or vegetable matter, among other chemical processes. Inorganic<unk>  is output by volcanoes and other geothermal processes such as hot springs.<unk>  has no liquid state at pressures below 5.1 atm, but is a solid at temperatures below -78 °C. In its solid state,<unk>  is<unk> mmonly called dry ice.<unk>  is an acidic oxide: an aqueous solution turns litmus from blue to pink.
Carbon dioxide
Greenhouse gas
Peroxide
Hydrogen sulfide
Sulfur dioxide
Acrolein
Methane
Hydrocarbon