In order to understand the chemistry of natural gas, it is important to be familiar with some basic concepts of general chemistry. Here are some definitions you should know:

Matter – anything that has mass and occupies space. Energy – the capacity to do work or transfer heat.

Elements – substances that cannot be decomposed into simpler substances by chemical changes. There are approximately 112 known elements. Examples: carbon, oxygen, and nitrogen.

Atom – the smallest unit in which an element can exist. Atoms are composed of electrons, protons, and neutrons.

Compounds – pure substances consisting of two or more different elements in a fixed ratio. Examples: water and methane.

Molecule – the smallest unit in which a compound can exist or the normal form in which an element exists. Example: One molecule of water consists of two hydrogen atoms and one oxygen atom. One molecule of nitrogen consists of two atoms of nitrogen.

Mixture – combination of two or more pure substances in which each substance maintains its own composition and properties. Examples: natural gas, gasoline, and air.

Bonds

The attractive forces that hold atoms together in compounds are called chemical bonds. There are two major classes of bonds– ionic bonds and covalent bonds. Most of the bonds involved in natural gas components are single covalent bonds. A single covalent bond consists of a pair of electrons shared by two atoms. A double bond is two pair of electrons shared between two atoms. Some minor components of natural gas may contain both single and double bonds. Aromatic molecules, such as benzene, contain covalent bonds where multiple electrons are shared among more than two atoms.