The primary chemical reactions of methane are combustion, steam reforming to syngas, and halogenation. The positions of the hydrogen atoms are not fixed in methane I, i.e. This substance crystallizes in the cubic system ( space group Fm 3m). Cooling methane at normal pressure results in the formation of methane I. Solid methane exists in several modifications. As a gas, it is flammable over a range of concentrations (5.4–17%) in air at standard pressure. Methane has a boiling point of −161.5 ☌ at a pressure of one atmosphere. The familiar smell of natural gas as used in homes is achieved by the addition of an odorant, usually blends containing tert-butylthiol, as a safety measure. This is what gives Uranus and Neptune their blue or bluish-green colors, as light passes through their atmospheres containing methane and is then scattered back out. It does absorb visible light especially at the red end of the spectrum due to overtone bands, but the effect is only noticeable if the light path is very long. Methane is an odorless gas and appears to be colorless. The resulting 'three-over-one' bonding scheme is consistent with photoelectron spectroscopic measurements. Above this energy level is a triply degenerate set of MOs that involve overlap of the 2p orbitals on carbon with various linear combinations of the 1s orbitals on hydrogen. The lowest-energy MO is the result of the overlap of the 2s orbital on carbon with the in-phase combination of the 1s orbitals on the four hydrogen atoms. Its electronic structure is described by four bonding molecular orbitals (MOs) resulting from the overlap of the valence orbitals on C and H.

Methane is a tetrahedral molecule with four equivalent C–H bonds. It has also been detected on other planets, including Mars, which has implications for astrobiology research. The Earth's atmospheric methane concentration has increased by about 150% since 1750, and it accounts for 20% of the total radiative forcing from all of the long-lived and globally mixed greenhouse gases. When methane reaches the surface and the atmosphere, it is known as atmospheric methane. The largest reservoir of methane is under the seafloor in the form of methane clathrates. Naturally occurring methane is found both below ground and under the seafloor and is formed by both geological and biological processes. The relative abundance of methane on Earth makes it an economically attractive fuel, although capturing and storing it poses technical challenges due to its gaseous state under normal conditions for temperature and pressure. It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. Methane ( US: / ˈ m ɛ θ eɪ n/ MEH-thayn, UK: / ˈ m iː θ eɪ n/ MEE-thayn) is a chemical compound with the chemical formula CH 4 (one carbon atom bonded to four hydrogen atoms).

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