What is CNG ? Give its one use. From which natural substance are liquid fuels formed ? Which gas is the main constituent of LPG ? How was petroleum formed in nature ? Why do green leaves not catch fire easily ?

CNG — Compressed Natural Gas. It is used as a fuel. All liquid fuels are formed from petroleum. Butane is the main constituent of LPG. Petroleum was formed by the sedimentation of dead remains of microscopic marine plants and animals, which were buried under the surface of the earth, millions of years ago. Green leaves do not catch fire easily because they contain moisture.