Methane
Overview
Methane (METH-ane) is a colorless, odorless, tasteless, flammable gas that is less dense then air. It is the primary component of natural gas. Methane is the simplest of all hydrocarbons, organic compounds that contain carbon and hydrogen and no other elements.
Key Facts
Other Names:
Marsh gas; methyl hydride
Formula:
CH4
Elements:
Carbon, hydrogen
Compound Type:
Hydrocarbon; alkane (organic)
State:
Gas
Molecular Weight:
16.04 g/mol
Melting Point:
−182.47°C (−296.45°F)
Boiling Point:
−161.48°C (−322.63°F)
Solubility:
Very slightly soluble in water and acetone; soluble in ethyl alcohol, methyl alcohol, and ether
How It Is Made
Methane formed millions of years ago from microscopic underwater plants and bacteria that dropped to the bottom of the ocean when they died. Over millions of years, they were crushed and heated by the pressure of layers of sand, dirt, and other materials that accumulated on top of them. The mineral components of the undersea mud gradually turned into a type of rock known as shale. Some of the organic components turned into natural gas, which is mostly methane. The natural gas became trapped in porous rocks called reservoir rocks and in larger pockets of the rock called reservoirs or geologic traps. Natural gas is now found in pockets by itself, but is more commonly found floating on top of petroleum lakes in underground reservoirs.
Methane is also found in conjunction with pockets of coal. The largest reserves of natural gas in the United States are in Texas, Alaska, Oklahoma, Ohio, and Pennsylvania. Oil and gas companies remove natural gas from the ground by drilling. They then purify the natural gas by separating the components of which it is made, such as methane, ethane, propane, and butane. After isolation from natural gas, methane is often liquefied, which makes its easier to store and transport.
Although abundant supplies of methane exist, it can also be produced synthetically. For example, the reaction between steam and hot coal results in the formation of synthesis gas, a mixture of hydrogen and carbon monoxide. When this mixture is passed over a catalyst containing nickel metal, methane is formed. A very similar process, called the Sabatier process, uses a mixture of hydrogen and carbon dioxide, rather than carbon monoxide, also resulting in the formation of methane. Finally, methane produced during the anaerobic decomposition of manure can be captured and purified.
Common Uses and Potential Hazards
When methane burns, it releases a large amount of energy, making it useful as a fuel. Humans have known about methane as a source of energy for thousands of years. Temples in the ancient world often burned "eternal flames" that may have been fueled by natural gas. In the early nineteenth century, people began using natural gas as a light source. Once oil was discovered in the 1860s, however, its use, and the electricity produced by burning oil, became much more popular, and people abandoned natural gas as a fuel except for limited use in cooking.
Natural gas has become more popular in recent years because its use results in less pollution than petroleum and other fossil fuels. Some uses include heating homes, offices, and factories; powering room heaters and air conditioners; and operating home appliances such as water heaters and stoves.
Interesting Facts
- Methane is sometimes called marsh gas because it forms in swamps as plants and animals decay under water.
- Methane is odorless, but gas companies add traces of sulfur-containing compounds with strong odors so that people will be able to smell gas leaks and avoid suffocation or explosions.
- Some experts estimate that enough methane is present in the Earth's surface to last as much as two hundred years, although extraction of some methane resources may prove to be difficult.
Scientists are now exploring other uses for methane and natural gas with the hope that they might eventually become the most important fuels used by humans. Methane has some advantages over petroleum and coal as a fuel. It burns more cleanly than either of these other fossil fuels, producing only carbon dioxide and water as combustion products. Some experts believe that methane could be used as a power source of fuel cells, cells that burn hydrogen to produce electricity. Adding natural gas to oil- or coal-fired burners would also help reduce the greenhouse gas emissions of these appliances.
In addition to its applications as a fuel, methane is used in the manufacture of a number of organic and inorganic compounds. For example, ammonia, which is the tenth most important chemical compounds in the United States, based on quantity produced, is made from hydrogen and nitrogen gases. Over 90 percent of the hydrogen used to make ammonia is now obtained by reacting methane with water at high temperatures over a catalyst of iron oxide (Fe3O4). Other compounds produced from methane include methanol (methyl alcohol), acetylene (ethyne), formaldehyde (methanal), hydrogen cyanide, carbon tetrachloride, chloroform, methylene chloride, and methyl chloride.
Methane is not toxic, but it can cause suffocation by reducing or eliminating the oxygen a person needs to breathe normally. The primary hazard posed by the gas is its flammability and explosive tendency.
Words to Know
Describing a process that takes place in the absence of oxygen. One of several gases, including carbon dioxide and ozone, that causes the greenhouse effect on Earth.For Further Information
"Chemical of the Week: Methane." Science Is Fun. http://scifun.chem.wisc.edu/chemweek/methane/methane.html (accessed on October 17, 2005).
"Methane." U.S. Environmental Protection Agency. http://www.epa.gov/methane/ (accessed on October 17, 2005).
"Methane Madness: A Natural Gas Primer." The Coming Global Oil Crisis. http://www.oilcrisis.com/gas/primer/ (accessed on October 17, 2005).
Sherman, Josepha, and Steve Brick. Fossil Fuel Power. Mankato, MN: Capstone Press, 2003.
See Also
Propane
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