Chapter 15. Microscale Gas Chemistry:

A. Appearance

         Methane, CH4, is a colorless, odorless, flammable gas that burns with a faintly blue flame.  "Natural gas," used by many North Americans for heating and cooking, is primarily methane (>90%).  The 'gas odor' is from an added substance so that gas leaks can be detected.  Pure methane has no odor.  Explosive mixtures of methane with air contain between 5 - 14 % methane.  Mixtures containing more than 14% burn without explosion.

B. Physical Properties of CH4

Molecular mass:   16.0429 g/mol
melting point   -182 ^oC
boiling point   -164 ^oC

    Methane was first prepared in 1899 by Matthews by the method employed in this chapter — heating sodium acetate with sodium hydroxide (J. Amer. Chem. Soc. 21, 647 (1899)):

D. Natural Abundance

     Methane occurs widely in nature.  It is called 'marsh gas' and is one product of anaerobic decay of organic matter.  Methane is a major component of the atmosphere of the outer planets.

    Pure methane can be prepared from the combination of pure carbon and hydrogen at temperatures of at least 1100 oC.  Methane is also produced from natural gas (in North America natural gas is typically 85% methane) and from the fermentation of sewage and other sludges.

F. Industrial Uses

     Used for heating, cooking and illuminating.  Methane is also used in the manufacture of hydrogen which subsequently is use in the manufacture of ammonia.  Methane is used to produce formaldehyde, hydrogen cyanide and numerous organic compounds.

G. Gas Density of CH4

     The density of CH4 is 0.6557 g/L at 25 ^oC and 1 atm.  This is only 55% the density of air.

H. Gas Solubility of CH4

     Methane is not very soluble in water (3.5 mL CH4 per 100 mL water at 17 ^oC and standard pressure).  Methane is soluble in alcohol, ether and many organic solvents.