Natural gas is a gas or vapor that is also stored in reservoirs below the ground. Crude oil and natural gas are often referred to as petroleum . Crude oil and natural gas are composed of molecules containing carbon and hydrogen atoms. Hydrogen is most commonly found in water which is composed of two hydrogen atoms and one oxygen atom. The carbon atom, represented by the letter C, is found in the mineral coal or in the carbon dioxide which we exhale when we breathe.
Carbon dioxide is composed of two atoms of oxygen and one atom of carbon.
The chemical formula for carbon dioxide is written CO 2 . Large hydrocarbon molecules, such as those found in petroleum, are formed by joining or bonding of many hydrogen and carbon atoms. The properties of these hydrocarbons depend upon the number of and arrangement of the carbon atoms in their molecules. Crude oil is composed of not just one molecule but a mixture of many molecules composed of different numbers of carbon and hydrogen atoms. The simplest hydrocarbon is composed of one carbon atom and four hydrogen atoms, CH 4 .