CH4

CH4, or methane, is the simplest alkane and the main component of natural gas. It is a colorless, odorless, flammable gas at room temperature and pressure. In the gas phase it adopts a tetrahedral molecular geometry with carbon at the center and four equivalent C–H bonds. The C–H bond length is about 1.09 angstroms. Methane is non-polar and has low solubility in water. It has a boiling point of about −161.5 °C and a melting point of about −182.5 °C.

Methane occurs naturally in several reservoirs and through biological processes. It is produced biologically by methanogenic archaea in anaerobic environments such as wetlands, ruminant guts, and landfills. It is a major component of natural gas and is found in petroleum reservoirs. Industrially, methane is produced from fossil sources by steam methane reforming, partial oxidation, or gasification, and it can be formed during the thermal decomposition of organic matter.

Uses of methane include its use as a fuel for heating and electricity generation, and as a feedstock for chemical synthesis. Through processes such as steam reforming, methane is converted to synthesis gas (a mixture of carbon monoxide and hydrogen) for the production of hydrogen, methanol, ammonia, and other chemicals.

Environmental and safety considerations are important for CH4. Methane is a potent greenhouse gas with a significant global warming potential over 100 years and a shorter atmospheric lifetime. Major anthropogenic sources include enteric fermentation in ruminant animals, rice paddies, landfills, and fossil-fuel systems. It is highly flammable, with an explosive range in air of roughly 5% to 15%, and leaks require detection and safety measures. Methane is stored as compressed gas or liquefied natural gas for transport and fuel use.