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1、Lesson OneNEW WORDS1.sleet n.冻雨，雨夹雪2. depend vi.依赖,取决于3. hail n.雹4. form vt.,vi.形成5. low a.低的6. temperature n.温度7. molecule n.分子8. cling vi.粘着9. droplet n.小水滴10. dust n.灰尘11. particle n.粒子,微粒12. nucleus n.核,原子核13.dew n.露水14.crystal n.晶体15.condensation n.冷凝,凝结16. rapid a.快的17.moisture n.湿气,水分18. free
2、ze vi.结冰19.raindrop n.雨点20.instead ad.代替,替换21.snowflake n.雪片22.shape n.形状23. flake n.薄片24.hexagonal a.六角形的25.lens n.透镜26.strike vt.,vi.打击击中,撞27.thunderstorm n.雷雨28.swift a.迅速的29.current n.气流,潮流30.toss vt.,vi.抛,扔,颠簸31.acquire vt.取得,获得32.hailstone n.冰雹33.stick vi.粘住34.theory n.理论35.explain vt.说明,解释,阐明
3、PHRASES AND EXPRESSIONSThe more the more越 越So that 如此 以致Take place 发生As soon as 一 就High above 大大高于Well below 远远低于Take on 呈现A bit of 一点 A mass of 一块Start out 出发,着手进行 layer of 一层TEXTRAIN, SNOW, SLEET, AND HAILThe forming of rain in a cloud depends upon temperature. The lower the temperature, the more
4、the molecules of water vapor in the cloud cling together. Then they form droplets of water. Usually droplets form around dust or other particles in the air when the dew point is reached. If ice crystals are in the cloud, even more droplets may form.In clouds, condensation may be so rapid that millio
5、ns of droplets of water are formed. As these droplets collect more molecules and therefore become heavier, their weight makes them fall to the earth. If the temperature of the air is above freezing the drops will fall as rain.When the air high above the earth is well below freezing, the moisture in
6、the air does not form raindrops. Instead, it forms snow. Snowflakes take on many interesting shapes. They seem to be formed around a center. Snow is made up of millions of these flakes, each a bit of water vapor that in freezing temperatures was changed into a flake of snow.Snowflakes are really cry
7、stals; they are water molecules grouped in a hexagonal pattern. It is interesting to study snowflake crystals under a hand lens.Sometimes droplets of water start out as rain and change into another form on their way to the earth. The raindrops may start downward through a layer of warm air and then
8、strike a mass of cold air, where each raindrop freezes. These frozen raindrops fall to the earth as sleet; skeet us frozen rain.Sometimes still another change may take place in drops of rain. During a thunderstorm, swift upward currents of air usually carry raindrops with them. As the air grows cold
9、er, these raindrops may form little balls of ice. In a mass of warm air, they may get a coating of moisture, which freezes as soon as they are tossed up again into a colder mass of air. Up and down they are carried, acquiring more and more layers of ice. This goes on until the balls of ice become he
10、avy enough to fall to the earth as hailstones. If you cut a hailstone in two, you can see the layers of ice.Some scientists think that hailstones are formed in a different way. A hailstone nucleus, a tiny droplet of water that is frozen, may form high in the atmosphere. As it falls through a cloud,
11、it meets cold water droplets and snowflakes which stick to this nucleus. The hailstone may meet many of these droplets and snowflakes before it falls from the cloud to the earth. As the droplets of water stick to the hailstone, they add a clear layer of ice. As snowflakes stick to it, they form a cl
12、oudy layer. This theory explains why clear and cloudy layers are found inside the hailstone when it is cut open. EXERCISESI.Complete the following sentences with nouns formed from the verbs given in brackets. 1.Theof rain depends on the and the of tiny droplets of water vapour in the cloud.(form/con
13、dense/combine)2.When the droplets are heavy enough to fall, can take place.(precipitate)3.The and of water can be observed in everyday life.(evaporate/condense)4.The of ice to water and water to water vapour by heating is a good of the change of state of matter.(convert/illustrate)5.The 100 equal ar
14、e made after the byof the boiling point of water and the melting point of ice.(divide/determine/observe)6.The best of what takes place is the of good examples.(explain/provide)7. A lake which is used for wateris sometimes high enough for the of by gravity to transport the water along the pipes to th
15、e houses below.(store/exert/press)8.In science, the Centigrade thermometer is used for the of temperature.(measure)II. Answer the following questions based on information found in the text.1.How is rain formed?2.When does the moisture in the air from snow?3.What is snow made up of?4.What is the difference between rain and sleet?5.Why are clear and cloudy layers found inside a hailstone when it is cut open?III. Give the English equivalents of the following expressions.1.取决于温度2.使雨点落到地面3.呈不同形状4.冷到足以形成小冰珠5.切成两半IV.Explain the different uses of the word “form” in t
