Question

For cooking, why are L.P.G. / P.N.G. fuels better than the other fuels?

Answer 1

Hint: Cooking fuel should be safe to use. It must be economically feasible .The LPG gas is a mixture of propane and butane and PNG is a methane. These have high calorific value. Undergoes the complete combustion and do not produce residue.

Complete answer:
LPG stands for the liquefied petroleum gas and PNG stands for Piped Natural gas.LPG is a mixture of propane and butane gas. It has a higher density. However PNG is a methane gas. It has a low density and has slightly higher calorific value.
LPG is known as the cooking fuel. It is economically accessible fuel. It has an excellent heating capacity which saves a consumption of fuel.LPG on ignition undergoes the complete combustion and it does not produce any residue or the particulate matter. Thus LPG contributes less towards the air pollution. Following are some of the advantages of the LPG fuel over the other fuel.
1) It has a higher calorific value .cooks the food faster than any other fuel.
2) Better control: LPG is easy to control at the on and off of the knob. Household gas cylinders have a knob which allows us to control the flow of LPG to the stove. The adjustment of intensity forms a blue flame which is easy to regulate at a desired temperature of cooking.
3) LPG gas is convenient and safe to use.
4) When compared to the other fuels LPG is more economical. The stoves which used LPG require less maintenance as it undergoes the complete combustion. This does not form any residue.
5) LPG undergoes complete combustion and thus creates least greenhouse gases.LPG helps to reduce the greenhouse gases.
PNG is more advantageous than the LPG. PNG is a biogas and can be prepared in our house yards. The combustion reaction of methane is,
$\text{ C}{{\text{H}}_{\text{4}}}\text{(PNG) + 2}{{\text{O}}_{\text{2}}}\text{ }\to \text{ C}{{\text{O}}_{\text{2}}}\text{ + 2}{{\text{H}}_{\text{2}}}\text{O }$
It is cheaper and easy to use for cooking. Thus LPG and PNG are used for cooking purposes.

Note: Note that, apart from LPG and PNG, kerosene is also used as the cooking fuel. It is a mixture of 10 different hydrocarbons. Kerosene is a less volatile fuel and it has a low calorific value than the LPG .Thus ignition temperature of kerosene is higher than that of LPG. This makes it safe fuel. Laboratory uses spirit or ethanol as the fuel in some cases.