托福习题练习
| 托福考试易错题（2019/6/21） |
| 第1题： Physical andChemical Properties andChanges Sugar, water, and aluminum are different substances.Each substance has specific properties that do not depend on the quantity of the substance. Properties that can be used to identify or characterize a substance--and distinguish that substance from other substances--are called characteristic properties. They are subdivided into two categories: physical properties and chemical properties. The characteristic physical properties of a substance are those that identify the substance without causing a change in the composition of the substance. They do not depend on the quantity of substance.  Another example of a physical property is water. Whether a small pan of water is raised to its boiling point or a very large kettle of water is raised to its boiling point, the temperature at which the water boils is the same value, 100 degreesC、or 212 degrees F. 1.Does it burn in air 2.Does it decompose (break up into smaller substances) when heated 3. What happens when it is placed in an acid 4. What other chemicals will it react with, and what substances are obtained from the reaction Characteristic physical and chemical properties also called intensive properties are used to identify a substance. In addition to the characteristic physical properties already mentioned, some intensive physical properties include the tendency to dissolve in water, electrical conductivity, and density, which is the ratio of mass to volume. Additional intensive chemical properties include the tendency of a sub-stance to react with another substance, to tarnish, to corrode, to explode, or to act as a poison or carcinogen (cancer-causing agent). Extensive properties of substances are those that depend on the quantity of the sample, including measurements of mass, volume, and length. Whereas intensive properties help identify or characterize a particular kind of matter, extensive properties relate to the amount present. If a lump of candle wax is cut or broken into smaller pieces, or if it is melted(a change of state), the sample remaining is still candle wax. When cooled, the molten wax returns to a soliD、In these examples, only a physical change has taken place; that is, the composition of the substance was not affecteD、 When a candle is burned, there are both physical and chemical changes.After the candle is lighted, the solid wax near the burning wick melts. This is a physical change; the composition of the wax does not change as it goes from solid to liquiD、Some of the wax is drawn into the burning wick where a chemical change occurs. Here, wax in the candle flame reacts chemically with oxygen in the air to form carbon dioxide gas and water vapor. In any chemical change, one or more substances are used up while one or more new substances are formeD、The new substances produced have their own unique physical and chemical properties. The apparent disappearance of something, like the candle |
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| 第2题：Glaciers are large masses of ice on land that show evidence of past or present movement. They grow by the gradual transformation of snow into glacier ice. A、fresh snowfall is a fluffy mass of loosely packed snowflakes, small delicate ice constals grown in the atmosphere.As the snow ages on the ground for weeks or months,(5) the crystals shrink and become more compact, and the whole mass becomes squeezed together into a more dense form, granular snow.As new snow falls and buries the older snow, the layers of granular snow further compact to form firm, a much denser kind of snow, usually a year or more old, which has little pore space. Further burial and slow cementation―a process by which crystals become bound together in a mosaic of(10)intergrown ice crystals―finally produce solid glacial ice. In this process of recrystallization, the growth of new crystals at the expense of old ones, the percentage of air is reduced from about 90 percent for snowflakes to less than 20 percent for glacier ice. The whole process may take as little as a few years, but more likely ten or twenty years or longer. The snow is usually many meters deep by the time the lower layers art convened(15)into ice. In cold glaciers those formed in the coldest regions of theEarth, the entire mass of ice is at temperatures below the melting point and no free water exists. In temperate glaciers, the ice is at the melting point at every pressure level within the glacier, and free water is present as small drops or as larger accumulations in tunnels within or beneath the ice.(20)Formation of a glacier is complete when ice has accumulated to a thickness (and thus weight) sufficient to make it move slowly under pressure, in much the same way that solid rock deep within theEarth can change shape without breaking. Once that point is reached, the ice flows downhill, either as a tongue of ice filling a valley or as thick ice cap that flows out in directions from the highest central area where the most snow accumulates. The up down leads to the eventual melting of ice.The word "converted" in line 14 is closest in meaning to A、changed B．delayed C．promoted D．dissolved |
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| 第3题：(Few substances) lock less (alike than )coal and diamonds, yet both (are fashioned) (from same) elemental carbon. A、Few substances B．alike than C．are fashioned D．from same |
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| 第4题： Bubbles, flaws, and other irregularities diffuse the light that passes through stained glass, （） the glass sparkle. A. which making B. and making C. making D. to making |
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| 第5题： {$mediaurl} What are two key features of rain-shadow deserts mentioned in the discussionClick on 2 answers. A、They occur mostly in subtropical regions. B、They lie next to mountain ranges. C、They receive only a small amount of sun. D、Their exposure to moist air currents is blockeD、 |
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