(i) A fossil fuel is a fuel formed by natural processes, such as anaerobic decomposition of buried dead organisms. Fossil fuels contain high percentage of carbon. The word carbon is derived from the Latin word ‘Carbo’ meaning coal.
(ii) Coal is formed from the remains of trees and other vegetation. Approximately 350 million years ago, these remains were trapped on the bottom of swamps, accumulating layer after layer and creating a dense material called peat. As this peat was buried under more and more ground, the high temperature and pressure transformed it into coal.
(iii) Petrol and diesel are obtained from mineral oil. Mineral oil also called as crude oil or petroleum oil is formed from the remains of plants and animals that lived in the seas millions of years ago. This plant and animal matter has been drawn down and subjected to extremes of temperature and pressure over millions of years ago.
(iv) Mineral oil is commonly formed in rocks under the sea bed. The word petroleum is derived from Latin word ‘Rock oil’. Petrol and Diesel are obtained from mineral oil by the process called as fractional distillation.
Thus petrol, diesel and coal are fossil fuels.