Carbon dioxide

2D structure of carbon dioxide.

Carbon dioxide (chemical formula CO₂) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transparent to visible light but absorbs infrared radiation, acting as a greenhouse gas. Carbon dioxide is soluble in water and is found in groundwater, lakes, ice caps, and seawater.

As the source of available carbon in the carbon cycle, atmospheric CO₂ is the primary carbon source for life on Earth. Plants, algae and cyanobacteria use energy from sunlight to synthesize carbohydrates from carbon dioxide and water in a process called photosynthesis, which produces oxygen as a waste product. In turn, oxygen is consumed and CO₂ is released as waste by all aerobic organisms when they metabolize organic compounds to produce energy by respiration. CO₂ is released from organic materials when they decay or combust, such as in forest fires. Since plants require CO₂ for photosynthesis, and humans and animals depend on plants for food, CO₂ is necessary for the survival of life on earth.

About half of excess CO₂ emissions to the atmosphere are absorbed by land and ocean carbon sinks. These sinks can become saturated and are volatile, as decay and wildfires result in the CO₂ being released back into the atmosphere. CO₂ is eventually sequestered (stored for the long term) in rocks and organic deposits like coal, petroleum and natural gas. Sequestered CO₂ is released into the atmosphere through burning fossil fuels or naturally by volcanoes, hot springs, geysers, and when carbonate rocks dissolve in water or react with acids.

Uses

CO₂ is a versatile industrial material, used, for example, as an inert gas in welding and fire extinguishers, as a pressurizing gas in air guns and oil recovery. It is also a feedstock for the synthesis of fuels and chemicals.

Dependencies

• Carbon
• Oxygen
  • Carbon dioxide
    • Coal
    • Natural gas
    • Petroleum

See also

• Cyanide
• Chemical compounds
• Carbonic Acid

References

This article uses material from the Wikipedia article Carbon_dioxide, which is released under the Creative Commons Attribution-ShareAlike 3.0 Unported License (view authors).