Petroleum - نفت

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INTRODUCTION

Petroleum, or crude oil, naturally occurring oily, bituminous liquid composed of various organic chemicals. It is found in large quantities below the surface of Earth and is used as a fuel and as a raw material in the chemical industry. Modern industrial societies use it primarily to achieve a degree of mobility—on land, at sea, and in the air—that was barely imaginable less than 100 years ago. In addition, petroleum and its derivatives are used in the manufacture of medicines and fertilizers, foodstuffs, plastics, building materials, paints, and cloth and to generate electricity.

In fact, modern industrial civilization depends on petroleum and its products; the physical structure and way of life of the suburban communities that surround the great cities are the result of an ample and inexpensive supply of petroleum. In addition, the goals of developing countries—to exploit their natural resources and to supply foodstuffs for the burgeoning populations—are based on the assumption of petroleum availability. In recent years, however, the worldwide availability of petroleum has steadily declined and its relative cost has increased. Many experts forecast that petroleum will no longer be a common commercial material by the mid-21st century. World Energy Supply.

سوخت های فسیلی -Fossil Fuels

Fossil Fuels

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INTRODUCTION

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. See also Energy Supply, World.

لامپ های فلوئورسنت - Fluorescent Lamps

Fluorescent Lamp

Fluorescent Lamp, device that produces light by causing a substance called a phosphor to emit light, or fluoresce. Fluorescent lamps are cooler and more efficient than incandescent lamps, which produce light by heating a filament to high temperatures.

Fluorescent lamps use the fluorescing property of a class of materials called phosphors. When exposed to radiation such as ultraviolet light or an electron beam, phosphors emit visible light. Some examples of common phosphors that exhibit this property include zinc silicate and magnesium tungstate, the two materials most often used in fluorescent lamps.

کیسه های هوا در اتومبیل ها - Air Bags

Air Bag

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INTRODUCTION

Air Bag, safety device consisting of a large fabric bag that fills with air and provides protection for the head and upper body of an occupant of a motor vehicle during a collision. In head-on collisions, drivers and passengers are thrown forward inside the vehicles. When an air bag is activated, or deployed, it inflates instantly and creates a firm barrier that counters the forward motion of the driver or the front-seat passenger. Air bags are designed to prevent the driver or front-seat passenger from hitting the windshield or dashboard of the vehicle, thereby eliminating injuries or reducing their severity. An air bag is also known as a supplemental restraint system (SRS), or a supplemental inflatable restraint (SIR). Air bags are designed to work in conjunction with seat belts. However, an air bag alone can provide some protection for a vehicle occupant who is not wearing a seat belt. See also Automobile: Safety Features.

In 2002 over 60 percent of all vehicles in the United States were equipped with drivers air bags. The National Highway Traffic and Safety Administration (NHTSA) estimated that by 2002 air bags had saved the lives of over 9,000 people in the United States.

باران اسیدی

Acid Rain

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INTRODUCTION

Acid Rain, form of air pollution in which airborne acids produced by electric utility plants and other sources fall to Earth in distant regions. The corrosive nature of acid rain causes widespread damage to the environment. The problem begins with the production of sulfur dioxide and nitrogen oxides from the burning of fossil fuels, such as coal, natural gas, and oil, and from certain kinds of manufacturing. Sulfur dioxide and nitrogen oxides react with water and other chemicals in the air to form sulfuric acid, nitric acid, and other pollutants. These acid pollutants reach high into the atmosphere, travel with the wind for hundreds of miles, and eventually return to the ground by way of rain, snow, or fog, and as invisible “dry” forms.

Damage from acid rain has been widespread in eastern North America and throughout Europe, and in Japan, China, and Southeast Asia. Acid rain leaches nutrients from soils, slows the growth of trees, and makes lakes uninhabitable for fish and other wildlife. In cities, acid pollutants corrode almost everything they touch, accelerating natural wear and tear on structures such as buildings and statues. Acids combine with other chemicals to form urban smog, which attacks the lungs, causing illness and premature deaths.