Petroleum
Category : 8th Class
Petroleum
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.
Composition
The hydrocarbons in crude oil are mostly alkanes, cycloalkanes and various aromatic hydrocarbons while the other organic compounds contain nitrogen, oxygen and sulphur, and trace amounts of metals such as iron, nickel, copper and vanadium. The exact molecular composition varies widely from formation to formation but the proportion of chemical elements vary over fairly narrow limits as follows:
Table: Composition of crude petroleum by weight
Element Percent range
Carbon 83 to 87%
Hydrogen 10 to 14%
Nytrogen 0.1 to 2%
Oxygen 0.1 to 1.5%
Sulfur 0.5 to 6%
Metals Less than 1000 ppm
Characteristics
The chemical composition of all petroleum is principally hydrocarbons, although a few sulphur-containing and oxygen-containing compounds are usually present; the sulphur content varies from about 0.1 to 5 percent. Petroleum contains gaseous, liquid, and solid elements. The consistency of petroleum varies from liquid as thin as gasoline to liquid so thick that it will barely pour. Small quantities of gaseous compounds are usually dissolved in the liquid; when larger quantities of these compounds are present, the petroleum deposit is associated with a deposit of natural gas.
Formation
Petroleum is formed under Earth's surface by the decomposition of marine organisms. The remains of tiny organisms that live in the sea—and, to a lesser extent, those of land organisms that are carried down to the sea in rivers and of plants that grow on the ocean bottoms—are enmeshed with the fine sands and silts that settle to the bottom in quiet sea basins. Such deposits, which are rich in organic materials, become the source rocks for the generation of crude oil. The process began many millions of years ago with the development of abundant life, and it continues to this day. The sediments grow thicker and sink into the seafloor under their own weight. As additional deposits pile up, the pressure on the ones below increases several thousand times, and the temperature rises by several hundred degrees. The mud and sand harden into shale and sandstone; carbonate precipitates and skeletal shells harden into limestone; and the remains of the dead organisms are transformed into crude oil and natural gas.
Environmental Effects of Using Petroleum
Adding to the urgency of'finding alternatives to petroleum and other fossil fuels is the problem of global warming. Petroleum combustion releases carbon dioxide, a greenhouse gas, into the atmosphere, and most atmospheric scientists believe that rising levels of greenhouse gases are driving climate change.
These changes could cause numerous environmental problems, including disrupted weather patterns and polar ice cap melting. Disrupted weather patterns could lead to extensive drought and desertification. Polar ice cap melting could cause flooding and profound changes in ocean circulation.
Which one of the following types of coal is of higher quality than bituminous coal?
(a) Peat
(b) Lignite
(c) Anthracite
(d) All of these
(e) None of these
Answer: (c)
Petroleum mainly consists of:
(a) Carbon
(b) Hydrogen
(c) Nitrogen
(d) Oxygen
(e) None of these
Answer: (a)
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