This is the simplest hydrocarbon and is the main constituent of natural gas tapped from earth’s upper layers. Methane CH4 gas is found in coal mines and a flame or spark can explode mixture of methane and air. Since this is a dangerous situation which is to be avoided, a safety device called Davy’s safety lamp (named after British scientist Humphrey Davy who invented this device) is used to indicate the presence of methane so that timely action for pumping fresh air to remove methane can be taken. The flame of this lamp is surrounded by metal gauze which dissipates heat and prevents the flame from passing through it. It methane is present, the flame inside the gauze increases in size.
Laboratory Preparation of Methane:
IN the laboratory, methane is prepared by heating a mixture of sodium acetate and soda lime (i.e. a mixture of sodium hydroxide and calcium oxide) in a boiling tube.
The gas being insoluble in water is collected in a boiling tube by displacement of water.
Properties of Methane:
Colorless, odorless, tasteless gas
Lighter than air
Insoluble in water
Soluble in ether, alcohol and carbon tetrachloride
Chemical Properties of Methane:
Methane burns in air with a bluish flame forming CO2 and H2O and large amount of heat and light is produced.
CH4 + 2O2 + 2H2O + Energy (Heat + Light)
It explodes violently when mixed with air or oxygen and ignited. This is the cause of explosions in mines.
Uses of Methane:
Excellent fuel for cooking. Supplied to homes from reservoirs of natural gas through pipelines.
Chemicals such as fertilizers, chloro-carbons, formaldehyde and methanol are made from methane.