Different types of fossil fuels vary in the quantity of hydrocarbons that they contain and this is the reason that they differ in their burning rates. Each fossil fuel contains a chain of hydrocarbons. This chain of hydrocarbons is then used to create large amount of energy. Any fossil fuel when burnt always releases energy and also produces some harmful gases. Natural gas is one the fossil fuel that do not produce any harmful gases as it burns completely. Coal and oil produce large amount of carbon dioxide and sulphur dioxide that pollutes the environment.