Solution

Liquified Petroleum Gas (LPG) is both liquid and gas in a cylinder while wood is a solid fuel. LPG consists of volatile hydrocarbons such as propane and butane while wood is made up of complex biological hydrocarbons such as cellulose, hemicellulose and lignin. LPG has a very low ignition temperature and can easily catch fire with a flame. When wood is heated a little, it would still not catch fire. The ignition temperature of LPG is lower than that of wood. Thus we need to take special care in storing LPG. Combustion of LPG gives only carbon dioxide and water vapour while combustion of wood gives carbon dioxide, water vapour and ash, which is harmful when inhaled.