Difference Between Methane and Propane    

Methane vs Propane
 

Methane and Propane are the first and the third members of the alkane family. Their molecular formulae are CH4 and C3H8 respectively. The key difference between Methane and Propane is their chemical structure; Methane contains only one carbon atom and four hydrogen atoms whereas Propane contains three carbon atoms with eight hydrogen atoms. Their chemical and physical properties vary due to this difference.

What is Methane?

Methane, also known as carbane, natural gas, marsh gas, carbon tetrahydride, or hydrogen carbide,  is the smallest member of the alkane family. Its chemical formula is CH4 (four hydrogen atoms are bonded to one carbon atom). It is a major constituent of natural gas. Methane is a colorless, odorless and tasteless gas. It can be easily ignited since its vapor is lighter than the air.

Methane can be found naturally under the ground and under the sea floor. The atmospheric methane is considered a greenhouse gas. Methane breaks down into CH3- with water in the atmosphere.

What is Propane?

Propane is the third member of the Alkane family. Its molecular formula is C3H6, and the molecular mass equals to 44.10 g·mol−1. It exists as a gas at standard temperature and pressure, but it can compress into a transportable liquid. Propane does not exist naturally, but it is obtained from the petroleum refining process and as a by-product of natural gas processing.

Propane is a colorless, odorless, non-toxic and flammable gaseous substance and a commercial odorant is added for the identification of leakages.

What is the difference between Methane and Propane?

Characteristics of Methane and Propane

Molecular Structure:

Methane: The molecular formula of methane is CH4, and it is an example of a tetrahedral molecule with four equivalent C–H bonds (sigma bonds). Its structure is given below.Key Difference - Methane vs Propane

Propane: The molecular formula of ethane is C3H8, and its structure is given below.Difference Between Methane and Propane

Chemical Properties:

Combustion:

Methane: Methane burns with a pale-blue non-luminous flame producing carbon dioxide and water in the presence of excess air or oxygen. It is a highly exothermic reaction; thus, it is an excellent fuel.

CH4(g)   +    2O2    →    CO2    +    2H2O   +     890 kJ/mol

It partially burns into carbon monoxide (CO) gas in the presence of insufficient air or oxygen.

2CH4(g)   +   3O2        2CO    +    2H2O   +     energy

Propane: Propane also burns in a similar way as the other alkanes. It completely burns in the presence of excess oxygen producing water and carbon dioxide.

C3H8    +    5O2      →        3CO2     +     4H2O   +    2220 kJ/mol

In the absence of sufficient oxygen for the combustion process, it incompletely burns into carbon monoxide and/or soot carbon.

2 C3H8    +     9O2     →      4CO2    +     2CO    +     8H2O    +      heat

OR

C3H8     +     9O2     →     3C       +     4H2O    +      heat

Propane combustion is much cleaner than the combustion of gasoline, but not as clean as that of natural gas.

Reactions:

Methane: Methane shows substitution reactions with halogens. In these reactions, one or more hydrogen atoms are replaced by an equal number of halogen atoms and it is called “halogenation.”  It reacts with chlorine (Cl) and bromine (Br) in the presence of sunlight.

When a mixture of methane and steam is passed through a heated (1000 K) nickel supported on alumina surface, it can produce hydrogen.

Propane: Propane  also shows halogenation reactions under special conditions producing different products in various proportions.

CH3-CH2-CH3     +     Cl2          CH3-CH2-CH2Cl (45% )     +     CH3-CHCl-CH3 (55%)

CH3-CH2-CH3     +     Br2        CH3-CH2-CH2Br (3%)      +    CH3-CHBr-CH(97%)

Uses of Methane and Propane

Methane: Methane is used in many industrial chemical processes (as a fuel, natural gas, liquefied natural gas) and it is transported as a refrigerated fluid.

Propane: Propane is generally used as a fuel in engines, furnaces, portable stoves, oxy-gas torches, water heaters, laundry dryers and for heating in houses. It is one of the liquefied petroleum gasses such as butane, propylene, and butylene.

Definitions:

Exothermic reaction: An exothermic reaction is a chemical reaction that releases energy by light or heat.

Substitution reactions: Substitution reaction is a chemical reaction which involves the displacement of one functional group in a chemical compound and replaced it with another functional group.

 References:
“Reaction of Propane with Oxygen!” THECOLT84
“Reactions of Alkenes” Michigan State University
 
Image Courtesy:
“Propane” By Holger87 – Own work (CC BY-SA 3.0) via Commons Wikimedia 
“Methane” (Public Domain) via Commons Wikimedia