Camphor

Camphor, volatile, white, crystalline compound,with a characteristic aromatic odor. Ordinary camphor is obtained from the camphor tree, Cinnamomum camphora, which grows in Asia and Brazil. The camphor is distilled by steaming chips of the root, stem, or bark. The leaves of certain plants, such as tansy and feverfew, contain a second form of camphor, which is not used commercially. A racemic form is present in the oil of an Asian chrysanthemum and is also produced synthetically for most commercial uses. Camphor is used in the manufacture of celluloid and explosives and medicinally in liniments and other preparations for its mild antiseptic and anesthetic qualities. It is poisonous if ingested in large amounts.

Camphor is insoluble in water, soluble in organic solvents, and melts at 176° C (349° F) and boils at 209° C (405° F).

Ozone

Ozone (Greek ozein, “to smell”), pale blue, highly poisonous gas with a strong odor. Ozone is considered a pollutant at ground level, but the ozone layer of the upper atmosphere protects life on Earth from the Sun’s harmful ultraviolet radiation.

Ozone is one of three forms, called allotropes, of the element oxygen. Ozone is triatomic, meaning that it has three atoms in each molecule (formula O3). Ordinary, or diatomic, oxygen (O2) is more stable than ozone and accounts for the bulk of oxygen in the atmosphere. Electrical sparks and ultraviolet light can cause ordinary oxygen to form ozone. The presence of ozone sometimes causes a detectable odor near electrical outlets.

PROPERTIES

At normal temperatures and pressures ozone is a gas with a specific gravity of 2.144 (about 1.5 times the density of ordinary oxygen gas). Ozone accounts for only a tiny fraction of the atmosphere and is normally invisible, but high concentrations of ozone gas are pale blue. The gas condenses to a liquid at -111.9°C (-169.52°F) and freezes at -192.5°C (-314.5°F). Liquid ozone is deep blue, and is diamagnetic (repelled by magnetic fields). Solid ozone is dark purple. Ozone is much more active chemically than ordinary oxygen. It is used in purifying water, sterilizing air, and bleaching certain foods.

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ENVIRONMENTAL EFFECTS

Chlorofluorocarbons (CFCs)

Chlorofluorocarbons (CFCs), family of synthetic chemicals that are compounds of the elements chlorine, fluorine, and carbon. CFCs are stable, nonflammable, noncorrosive, relatively nontoxic chemicals and are easy and inexpensive to produce. During the 1970s, scientists linked CFCs to the destruction of Earth’s ozone layer. The manufacture of CFCs has since been banned in most countries.

USES

Scientists developed the first CFCs during the late 1920s. The compounds subsequently became used in a wide range of industrial products in the United States, Europe, and Japan. Manufacturers used CFCs as refrigerants in refrigerators, freezers, air conditioners, and heat pumps, and as propellants in aerosols and medical inhalers. CFCs also served as insulating foams in packaging materials, furniture, bedding, and car seats. Cleaning agents for electronic circuit boards, metal parts, and dry cleaning processes also used CFCs.

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• Harmful Effects of CFCs
• Regulation
• Extended Impact
  
  

Allotrope

Allotrope, two or more distinct physical forms of a chemical element in the same physical state. The term allotropy comes from the Greek allos tropos meaning “another shape.” Allotropes arise because of differing arrangements of an element’s atoms within its molecules or crystals.

One of the best-known examples of allotropy is carbon, which has multiple distinct allotropes including graphite, diamond, and buckminsterfullerene. Carbon atoms in diamond form a rigid, three-dimensional structure, with each carbon atom bonded to four other carbon atoms. In graphite the carbon atoms form stacks of flat honeycomb layers with only weak intermolecular forces between layers, while buckminsterfullerene forms balls and tubes with structures reminiscent of the geodesic domes designed by the architect Richard Buckminster Fuller.

Elements exhibiting allotropy include arsenic, antimony, iron, oxygen, phosphorus, selenium, sulfur, and tin.

There are two main kinds of allotropy, monotropy and enantiotropy. Monotropy (monotropic allotropy) occurs when one form of a substance is stable at all temperatures, while any other forms are metastable, and change (sometimes very slowly) into the stable form. For carbon, graphite is the stable monotrope, while diamond and buckminsterfullerene change, extremely slowly, into graphite. Phosphorus also exhibits monotropy: Red phosphorus is stable, while white (sometimes called yellow) phosphorus is metastable.

Enantiotropy (enantiotropic allotropy) occurs when one solid form of the substance changes into another solid form of the same substance when at a definite transition temperature. Tin, which changes from white tin to gray tin below 13°C (55°F), is an example of this type of allotropy. Gray tin is much more brittle than white tin. The Greek philosopher Aristotle recorded tin statues collapsing in the intense cold as long ago as the 4th century BC.

Infrared Radiation

Infrared Radiation, emission of energy as electromagnetic waves in the portion of the spectrum just beyond the limit of the red portion of visible radiation (see Electromagnetic Radiation). The wavelengths of infrared radiation are shorter than those of radio waves and longer than those of light waves. They range between approximately 10-6 and 10-3 (about 0.0004 and 0.04 in). Infrared radiation may be detected as heat, and instruments such as bolometers are used to detect it.

Infrared radiation is used to obtain pictures of distant objects obscured by atmospheric haze, because visible light is scattered by haze but infrared radiation is not. The detection of infrared radiation is used by astronomers to observe stars and nebulas that are invisible in ordinary light or that emit radiation in the infrared portion of the spectrum.

An opaque filter that admits only infrared radiation is used for very precise infrared photographs, but an ordinary orange or light-red filter, which will absorb blue and violet light, is usually sufficient for most infrared pictures. Developed about 1880, infrared photography has today become an important diagnostic tool in medical science as well as in agriculture and industry. Use of infrared techniques reveals pathogenic conditions that are not visible to the eye or recorded on X-ray plates. Remote sensing by means of aerial and orbital infrared photography has been used to monitor crop conditions and insect and disease damage to large agricultural areas, and to locate mineral deposits. In industry, infrared spectroscopy forms an increasingly important part of metal and alloy research, and infrared photography is used to monitor the quality of products.

Fossil Fuels

Fossil Fuels, energy-rich substances that have formed from long-buried plants and microorganisms. Fossil fuels, which include petroleum, coal, and natural gas, provide most of the energy that powers modern industrial society. The gasoline that fuels our cars, the coal that powers many electrical plants, and the natural gas that heats our homes are all fossil fuels.

Chemically, fossil fuels consist largely of hydrocarbons, which are compounds composed of hydrogen and carbon. Some fossil fuels also contain smaller amounts of other compounds. Hydrocarbons form from ancient living organisms that were buried under layers of sediment millions of years ago. As accumulating sediment layers exerted increasing heat and pressure, the remains of the organisms gradually transformed into hydrocarbons. The most commonly used fossil fuels are petroleum, coal, and natural gas. These substances are extracted from the earth’s crust and, if necessary, refined into suitable fuel products, such as gasoline, heating oil, and kerosene. Some of these hydrocarbons may also be processed into plastics, chemicals, lubricants, and other nonfuel products. Geologists have identified other types of hydrocarbon-rich deposits that can serve as fuels. Such deposits, which include oil shale, tar sands, and gas hydrates, are not widely used because they are too costly to extract and refine.

The majority of fossil fuels are used in the transportation, manufacturing, residential heating, and electric-power generation industries. Crude petroleum is refined into gasoline, diesel fuel, and jet fuel, which power the world’s transportation system. Coal is the fuel most commonly burned to generate electric power, and natural gas is used primarily in commercial and residential buildings for heating water and air, for air conditioning, and as fuel for stoves and other heating appliances.

Learn more:

• Formation of Fossil Fuels
• Removing and Refining Fossil Fuels
• Commercial Uses
• Environmental Effects of Using Fossil Fuels

Formation of Fossil Fuels

Fossil fuels formed from ancient organisms that died and were buried under layers of accumulating sediment. As additional sediment layers built up over these organic deposits, the material was subjected to increasing temperatures and pressures. Over millions of years, these physical conditions chemically transformed the organic material into hydrocarbons.

Most organic debris is destroyed at the earth's surface by oxidation or by consumption by microorganisms. Organic material that survives to become buried under sediments or deposited in other oxygen-poor environments begins a series of chemical and biological transformations that may ultimately result in petroleum, natural gas, or coal. Many such deposits occur in sedimentary basins (depressed areas in the earth’s crust where sediments accumulate), and along continental shelves. Sediments may accumulate to depths of several thousand feet in a basin, exerting pressures up to one hundred million pascals (tens of thousands of pounds per square inch) and temperatures of several hundred degrees on the organic material. Over millions of years, these conditions can chemically transform the organic material into petroleum, natural gas, coal, or other types of fossil fuels.

A. Petroleum Formation
B. Coal Formation
C. Natural Gas Formation
D. Other Fossil Fuels

Petroleum Formation

Petroleum formed chiefly from ancient, microscopic plants and bacteria that lived in the ocean and saltwater seas. When these microorganisms died and settled to the seafloor, they mixed with sand and silt to form organic-rich mud. As layers of sediment accumulated over this organic ooze, the mud was gradually heated and slowly compressed into shale or mudstone, chemically transforming the organic material into petroleum and natural gas.

Sometimes, the petroleum and natural gas would slowly fill the tiny holes within nearby porous rocks, which geologists call reservoir rocks. Because these porous rocks were usually filled with water, the liquid and gaseous hydrocarbons (which are less dense and lighter than water) migrated upward, through the earth’s crust, sometimes for long distances. A portion of these hydrocarbons would eventually encounter an impermeable (nonporous) layer of rock in an anticline, salt dome, fault trap, or stratigraphic trap. The impermeable rock would trap the hydrocarbons, creating a reservoir of petroleum and natural gas. Exploration geologists seek these underground formations because they often contain recoverable petroleum deposits. The fluids and gases caught in these geologic traps typically separate into three layers: water (highest density, bottom layer), petroleum (middle layer), and natural gas (low density, top layer).

Coal Formation

Coal is a solid fossil fuel formed from ancient plants—including trees, ferns, and mosses—that grew in swamps and bogs or along coastal shorelines. Generations of these plants died and were gradually buried under layers of sediment. As the sedimentary overburden increased, the organic material was subjected to increasing heat and pressure that caused the organic material to undergo a number of transitional states to form coal. The mounting pressure and temperature caused the original organic material, which was rich in carbon, hydrogen, and oxygen, to become increasingly carbon-rich and hydrogen- and oxygen-poor. The successive stages of coal formation are peat (partially carbonized plant matter), lignite (soft brownish-black coal with low carbon content), subbituminous coal (soft coal with intermediate carbon content), bituminous coal (soft coal with higher carbon and lower moisture content than subbituminous coal), and anthracite (hard coal with highest carbon content and lowest moisture content). Because anthracite is the most carbon-rich, moisture-deficient form of coal, it has the highest heating value.

Natural Gas Formation

Most natural gas is formed from plankton—tiny water-dwelling organisms, including algae and protozoans—that accumulated on the ocean floor as they died. These organisms were slowly buried and compressed under layers of sediment. Over millions of years, the pressure and heat generated by overlying sediments converted this organic material into natural gas. Natural gas is composed primarily of methane and other light hydrocarbons. As discussed previously, natural gas frequently migrates through porous and fractured reservoir rock with petroleum and subsequently accumulates in underground reservoirs. Because of its light density relative to petroleum, natural gas forms a layer over the petroleum. Natural gas may also form in coal deposits, where it is often found dispersed throughout the pores and fractures of the coal bed.

Other Fossil Fuels

Geologists have identified immense deposits of other hydrocarbons, including gas hydrates (methane and water), tar sands, and oil shale. Vast deposits of gas hydrates are contained in ocean sediments and in shallow polar soils. In these marine and polar environments, methane molecules are encased in a crystalline structure with water molecules. This crystalline solid is known as gas hydrate. Because technology for the commercial extraction of gas hydrates has not yet been developed, this type of fossil fuel is not included in most world energy resource estimates.

Tar sands are heavy, asphaltlike hydrocarbons found in sandstone. Tar sands form where petroleum migrates upward into deposits of sand or consolidated sandstone. When the petroleum is exposed to water and bacteria present in the sandstone, the hydrocarbons often degrade over time into heavier, asphaltlike bitumen. Oil shale is a fine-grained rock containing high concentrations of a waxy organic material known as kerogen. Oil shale forms on lake and ocean bottoms where dead algae, spores, and other microorganisms died millions of years ago and accumulated in mud and silt. The increasing pressure and temperature from the buildup of overlying sediments transformed the organic material into kerogen and compacted the mud and silt into oil shale. However, this pressure and heat was insufficient to chemically break down the kerogen into petroleum. Because the hydrocarbons contained in tar sand and oil shale are not fluids, these hydrocarbons are more difficult and costly to recover than liquid petroleum.

Removing and Refining Fossil Fuels

Geologists use a variety of sophisticated instruments to locate underground petroleum, natural gas, and coal deposits. These instruments allow scientists to interpret the geologic composition, history, and structure of sedimentary basins in the earth’s crust. Once located, petroleum and natural gas deposits are removed by wells drilled down into the deposit, while coal is removed by excavation.

Petroleum and Natural Gas
To locate deposits of petroleum and natural gas, exploration geologists search for geologic regions containing the ingredients necessary for petroleum formation: organic-rich source rock, burial temperatures sufficiently high to generate petroleum from organic material, and petroleum-trapping rock formations.

When potentially petroleum-rich geologic formations are identified, wells are drilled into the sedimentary basin. If a well intersects porous reservoir rock containing significant petroleum and natural gas deposits, pressure inside the trap may force the liquid hydrocarbons spontaneously to the surface. However, pressure inside the trap typically declines to the point where the petroleum must be pumped to the surface.

Once petroleum has been extracted from the ground, it is transported by pipeline, truck, or tanker to a refinery to be separated into liquid and gas components. Raw petroleum is heated to distill hydrocarbons by molecular weight. Lighter molecules are separated and refined into gasoline and other fuels, while heavier molecules are processed into engine lubricants, asphalt, waxes, and other products. Because demand for fuel far exceeds demand for the products made from the heavier hydrocarbons, refiners often break apart the heavy molecules into lighter ones that can be refined into gasoline. They do so by means of processes called thermal cracking and catalytic cracking.

Coal
Because of their enormity, the world’s most extensive coal beds have already been identified. Modern underground mining commonly employs machines called longwall miners to remove coal. These machines use rotating drums studded with picks to rip coal from seams in large chunks.

Surface-mine operators use mammoth earth-moving shovels to mine coal. These shovels first remove overlying soil and rock so the coal beds can be blasted apart. The blasted coal is scooped up and loaded into the beds of huge trucks for transport.

Fossil Fuels: Commercial Uses

Once fossil fuel has been extracted and processed, it can be burned for direct uses, such as to power cars or heat homes, or it can be combusted for the generation of electrical power.

Direct Combustion
Fossil fuels are primarily burned to produce energy. This energy is used to power automobiles, trucks, airplanes, trains, and ships around the world; to fuel industrial manufacturing processes; and to provide heat, light, air conditioning, and energy for homes and businesses.

To provide fuel for transportation, petroleum is refined into gasoline, diesel fuel, jet fuel, and other derivatives used in most of the world’s automobiles, trucks, trains, aircraft, and ships.

Demand for natural gas, historically considered a waste by-product of petroleum and coal mining, is growing in business and industry because it is a cleaner-burning fuel than petroleum or coal. Natural gas, which can be piped directly to commercial plants or individual residences and used on demand, is used for heating and for air conditioning. Residential uses of natural gas also include fuel for stoves and other heating appliances.

Electricity Generation
In addition to direct combustion for commercial uses, fossil fuels are also burned to generate most of the world’s electric power. In 2001 fossil fuel fired power plants produced 64 percent of the world’s electrical power, down from 71 percent in the late 1970s. In 2001 the world’s remaining electricity supply was generated primarily by hydroelectric power (17 percent) and nuclear fission (17 percent), with solar, geothermal, and other sources accounting for a relatively small amount.