四级冲刺练习阅读（164）

　　Petroleum products, such as gasoline, kerosene, home heating oil, residual fuel oil, and lubricating oils, come from one source crude oil found below the earths surface, as well as under large bodies of water, from a few hundred feet below the surface to as deep as 25,000 feet into the earths interior. Sometimes crude oil is secured by drilling a hole through the earth, but more dry holes are drilled than those producing oil. Pressure at the source or pumping forces crude oil to the surface.

　　Crude oil wells flow at varying rates, from ten to thousands of barrels per hour. Petroleum products are always measured in 42-gallon barrels.

　　Petroleum products vary greatly in physical appearance: thin, thick, transparent or opaque, but their chemical composition is made up of only two elements; carbon and hydrogen, which form compounds called hydrocarbons. Other chemical elements found in union with the hydrocarbons are few and are classified as impurities. Trace elements are also found, but these are of such minute quantities that they are disregarded. The combination of carbon and hydrogen forms many thousands of compounds which are possible because of the various positions and joinings of these two atoms in the hydrocarbon molecule.

　　The various petroleum products are refined from the crude oil by heating and condensing the vapors. These products are the so-called light oils, such as gasoline, kerosene, and distillate oil. The residue remaining after the light oils are distilled is known as heavy or residual fuel oil and is used mostly for burning under boilers. Additional complicated refining processes rearrange the chemical structure of the hydrocarbons to produce other products, some of which are used to upgrade and increase the octane rating of various types of gasolines.

　　26. Which of the following is NOT TRUE?

　　A. Crude oil is found below land and water.

　　B. Crude oil is always found a few hundred feet below the surface.

　　C. Pumping and pressure force crude oil to the surface.

　　D. A variety of petroleum products is obtained from crude oil.

　　27. Many thousands of hydrocarbon compounds are possible because_______.

　　A. the petroleum products vary greatly in physical appearance

　　B. complicated refining processes rearrange the chemical structure

　　C. the two atoms in the molecule assume many positions

　　D. the pressure needed to force it to the surface causes molecular transformation

　　28. Which of the following is TRUE?

　　A. The various petroleum products are produced by filtration.

　　B. Heating and condensation produce the various products.

　　C. Chemical separation is used to produce the various products.

　　D. Mechanical means such as the centrifuge are used to produce the various products.

　　29. Crude oil is brought to the surface by_______.

　　A. expansion of the hydrocarbons

　　B. pressure and pumping

　　C. vacuum created in the drilling pipe

　　D. expansion and contraction of the earths surface

　　30. Which of the following is not listed as a light oil?

　　A. distillate oil B. gasoline

　　C. lubricating oil D. kerosene

　　26. B 27. C 28. B 29. B 30. C