The chemical formula for methane is CH₄. It is the simplest hydrocarbon since it has one carbon atom bonded to four hydrogen atoms. It is a major component of natural gas and is used as a fuel. It is also used in the production of several chemicals.

Physical properties of Methane

State at room temperature

Form: At room temperature and pressure, methane is a colorless and odorless gas.

Density: At 0°C and 1 atm pressure, methane has a density of approximately 0.717 kg/m³, less than that of air.

Boiling and melting points

Boiling point: The boiling point of methane is approximately -161.5°C at 1 atm pressure.

Melting point: Its melting point is around -182.5°C at 1 atm pressure.

Solubility

Water solubility: Methane is slightly soluble in water. Its solubility in water is about 22 mg/L at 20°C. Because it is nonpolar, it does not readily dissolve in water.

Organic solvents: It is relatively more soluble in organic solvents such as alcohols and ethers.

Molecular weight: The molecular weight of methane is 16.04 g/mol calculated from the sum of the atomic weights of one carbon atom with an atomic weight 12.01 g/mol and four hydrogen atoms with an atomic weight of 1.008 g/mol each.

Flammability: Methane is highly flammable and forms explosive mixtures with either air or oxygen. The limits of its flammability fall within a range from 5% to 15% by volume in air.

Odor: Odorless itself, methane usually has odorants added to it, such as mercaptan in natural gas, that is primarily methane, for safety identification of leaks.

Thermal conductivity: Methane is a bad conductor of heat in terms of thermal conductivity, at around 0.416 W/(m·K) at 25°C.

Viscosity: Methane is actually a very low-viscosity fuel; at approximately 0.0112 mPa·s at 25°C, it flows easily.

Combustion: Methane burns in oxygen to give carbon dioxide and water. The reaction is very exothermic.

CH4+2O2→CO2+2H2O

incomplete combustion: In insufficient oxygen, methane undergoes incomplete combustion to form, besides water, either carbon monoxide [CO] or carbon [C] or both.

2CH4+3O2→2CO+4H2O CH4+2O2→CO+2H2O CH4+O2→C+2H2O

Reaction with halogens

Halogenation: In the presence of UV light, methane is reacted with halogens such as chlorine and bromine to yield haloalkanes.

CH4+Cl2→CH3Cl+HCl

Reaction mechanism: The reaction involves a radical chain reaction, bringing forth more than one chlorinated product of methane such as dichloromethane, CH₂Cl₂, and chloroform, CHCl₃.

Steam reforming: At high temperatures, about 700-1000°C, methane reacts with steam in the presence of a catalyst. It results in hydrogen and carbon monoxide, which is utilized for producing hydrogen.

CH4+H2O→CO+3H2

Water-gas shift reaction: Further, the produced carbon monoxide can react with steam and produce more hydrogen with the production of carbon dioxide.

CH4+O2→CH3OH CH4+O2→CH2O+H2O

Reaction with Oxygen

Partial oxidation: Methane can partly be oxidized into methanol or formaldehyde under certain conditions with the help of a catalyst.

CH4+O2→CH3OH CH4+O2→CH2O+H2O

Reaction with metals

Formation of metal carbides: Methane reacts with metals, such as calcium or magnesium, to form metal carbides.

Ca+2CH4→CaC2+4H2

Acidity and basicity

Non-acidic/non-basic: The methane molecule is electrically neutral and, under normal conditions, does not show acidic or basic nature.

Reaction with nitrogen oxides

Nitrosamine formation: In certain conditions, methane combines with nitrogen oxides, forming nitrosamines; this occurs less frequently compared with the other reactions.

Application of Methane

Energy production fuel: Methane is the main constituent of natural gas and is one of the most widely used fuels for heating, electricity production, and cooking. It is combusted in gas turbines and internal combustion engines to generate electricity.

Compressed natural gas: The raw material methane is compressed into fuel for the purpose of powering road vehicles, including buses and cars. This fuel serves as an alternative to gasoline and diesel. CNG, however, derives its resource value from the lesser amount of emissions it emits compared to conventional fossil fuels.

Chemical industry

Feedstock: Methane is a major feedstock associated with the manufacturing of various chemicals. It usually undergoes steam reforming to produce hydrogen that is utilized in various industrial processes.

Manufacture of methanol: Catalytic processes reduce methane to methanol, CH₃OH. The most significant uses of methanol are as a solvent and antifreeze, and as feedstock for the production of other chemicals like formaldehyde and acetic acid.

Agriculture

Fertilizer production: Methane is used to produce ammonia via the Haber process, which, in turn, is used to manufacture nitrogenous fertilizers like urea and ammonium nitrate.

Biogas: It highly consists of methane, derived from organic waste and anaerobic digestion both in landfills and from livestock manure. Application areas of Biogas: Electrical generation and renewable energy.

Gas: The process of capturing methane from landfills, where organic waste decomposes anaerobically. The recovered methane can be used in energy production or flared, thus decreasing the amount of gas released to the atmosphere.

Greenhouse gas reduction: There are different methods of reducing methane discharge through the rationalization of energy use, apart from methane recovery from agriculture and industry to counter climatic change.

Industrial processes

Hydrogen production: The steam reforming processes utilize methane during the production of hydrogen which is primarily utilized in petroleum refining and ammonia production, among other industrial processes.

Production of syngas: Methane is employed in the production of synthesis gas, better known as syngas-a mixture of hydrogen and carbon monoxide-serving as a precursor to produce many chemicals and fuels.

Refrigeration: Methane sometimes is used in refrigeration systems, though not that common compared to other refrigerants.

Analytical chemistry: Methane is used in the laboratory for a wide range of research analyses as standards in gas chromatography and a number of other chemical analytical techniques.

Cooking and heating: Methane represents one of the major sources of energy when it comes to cooking and heating both at residences and commercial institutions because it contains high energy and burns clean.

Conclusion

Among the chemical and physical properties of methane, what brings out the best in this fuel/feedstock in so many industrial processes, from hydrogen production to the synthesis of organic chemicals, may turn out to be its reactivity with halogens, besides its combustion characteristics, highly important concerning both industrial use and safety, up to its use in domestic appliances.

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