Matter & Energy

Matter is composed of atoms or groups of atoms called molecules. The arrangement of particles in a material depends on the physical state of the substance. In a solid, particles form a compact structure that resists flow. Particles in a liquid have more energy than those in a solid. They can flow past one another, but they remain close. Particles in a gas have the most energy. They move rapidly and are separated from one another by relatively large distances.

Natural Gas

Natural Gas, flammable gaseous mixture consisting mostly of hydrocarbons (chemical compounds that contain carbon and hydrogen). Along with coal and petroleum, natural gas is a fossil fuel. Natural gas may contain as much as 85 percent methane and about 10 percent ethane, and also contains smaller amounts of propane, butane, pentane, and other alkanes. Natural gas, which is usually found together with petroleum deposits in Earth’s crust, is extracted and refined into fuels that provide approximately 25 percent of the world energy supply.

Natural gas contains small amounts of impurities, including carbon dioxide, hydrogen sulfide, and nitrogen. Because these impurities can detract from the heating value and properties of natural gas, they are often removed during the refining process and used as commercial by-products.


Natural gas is used both as a fuel and as a raw material in the manufacture of chemicals. As a residential fuel, it is burned in furnaces, water heaters, cooking stoves, and clothes dryers. As an industrial fuel, it is burned in kilns (special furnaces) used to bake bricks and ceramic tiles and to produce cement. Natural gas is also used for generating steam in water boilers and as a source of heat in glass making and food processing.

Natural gas serves as a raw material for creating petrochemicals, which are chemicals that are specifically derived from natural gas or petroleum. In turn, petrochemicals are used as a base product for making fertilizers, detergents, pharmaceuticals, plastics, and numerous other goods.


Natural gas is formed from plankton, water-dwelling microorganisms that include algae and protozoans. As these microorganisms died and accumulated on the ocean floors, they were slowly buried and the remains were compressed under layers of sediment. Over millions of years, the pressure and heat exerted by the overlying sediments chemically transformed this organic material into natural gas.

Because petroleum and natural gas are formed by similar natural processes, these two hydrocarbons are often found together in underground reservoirs. After gradually forming in Earth’s crust, petroleum and natural gas slowly flow into the tiny holes of nearby porous rocks that serve as reservoirs. Because this porous reservoir rock is often filled with water, the petroleum and natural gas, both of which are lighter than water and less dense than the surrounding rock, migrate upward through the crust, sometimes for long distances. Eventually, some of these upward-moving hydrocarbons become trapped by an impermeable (nonporous) layer of rock, known as the cap rock. Natural gas is lighter than petroleum, so it forms a layer over the petroleum. This layer is called a gas cap.

Coal beds contain appreciable quantities of methane, the principal component of natural gas. In coal deposits, methane is often dispersed throughout the pores and fractures of the coal bed. This type of natural gas is often referred to as coal-bed methane.