六级冲刺练习：阅读（129）
<p> <span word="Evaporation">Evaporation</span>. <span word="In">In</span> <span word="order">order</span> <span word="to">to</span> <span word="understand">understand</span> <span word="why">why</span> <span word="precipitation">precipitation</span> <span word="occurs">occurs</span> <span word="and">and</span> <span word="to">to</span> <span word="appreciate">appreciate</span> <span word="some">some</span> <span word="of">of</span> <span word="the">the</span> <span word="similarities">similarities</span> <span word="and">and</span> <span word="differences">differences</span> <span word="in">in</span> <span word="the">the</span> <span word="various">various</span> <span word="types">types</span> <span word="of">of</span> <span word="precipitation">precipitation</span>, <span word="we">we</span> <span word="must">must</span> <span word="first">first</span> <span word="find">find</span> <span word="out">out</span> <span word="how">how</span> <span word="water">water</span> <span word="gets">gets</span> <span word="into">into</span> <span word="the">the</span> <span word="atmosphere">atmosphere</span>. <span word="This">This</span> <span word="will">will</span> <span word="also">also</span> <span word="help">help</span> <span word="us">us</span> <span word="to">to</span> <span word="understand">understand</span> <span word="some">some</span> <span word="of">of</span> <span word="the">the</span> <span word="other">other</span> <span word="weather">weather</span> <span word="elements">elements</span> <span word="like">like</span> <span word="dew">dew</span> <span word="and">and</span> <span word="frost">frost</span>, <span word="and">and</span> <span word="clouds">clouds</span> <span word="and">and</span> <span word="fog">fog</span>.</p><p> <span word="Of">Of</span> <span word="course">course</span> <span word="you">you</span> <span word="have">have</span> <span word="seen">seen</span> <span word="water">water</span> <span word="disappear">disappear</span> <span word="from">from</span> <span word="a">a</span> <span word="wet">wet</span> <span word="street">street</span> <span word="or">or</span> <span word="from">from</span> <span word="the">the</span> <span word="surface">surface</span> <span word="of">of</span> <span word="a">a</span> <span word="fish">fish</span> <span word="tank">tank</span>. <span word="We">We</span> <span word="call">call</span> <span word="this">this</span> <span word="disappearance">disappearance</span> <span word="evaporation">evaporation</span>. <span word="Why">Why</span> <span word="does">does</span> <span word="water">water</span> <span word="evaporate">evaporate</span> <span word="and">and</span> <span word="where">where</span> <span word="does">does</span> <span word="the">the</span> <span word="water">water</span> <span word="go">go</span>?</p><p> <span word="Scientists">Scientists</span> <span word="know">know</span> <span word="that">that</span> <span word="water">water</span>, <span word="like">like</span> <span word="all">all</span> <span word="other">other</span> <span word="substances">substances</span> <span word="in">in</span> <span word="the">the</span> <span word="universe">universe</span>, <span word="is">is</span> <span word="composed">composed</span> <span word="of">of</span> <span word="countless">countless</span> <span word="billions">billions</span> <span word="of">of</span> <span word="tiny">tiny</span> <span word="particles">particles</span> <span word="known">known</span> <span word="as">as</span> <span word="molecules">molecules</span>. <span word="The">The</span> <span word="molecules">molecules</span> <span word="of">of</span> <span word="water">water</span> <span word="are">are</span> <span word="so">so</span> <span word="small">small</span> <span word="they">they</span> <span word="cannot">cannot</span> <span word="be">be</span> <span word="seen">seen</span> <span word="with">with</span> <span word="even">even</span> <span word="the">the</span> <span word="most">most</span> <span word="powerful">powerful</span> <span word="electron">electron</span> <span word="microscopes">microscopes</span> <span word="ever">ever</span> <span word="devised">devised</span>. <span word="There">There</span> <span word="is">is</span> <span word="ample">ample</span> <span word="proof">proof</span> <span word="of">of</span> <span word="their">their</span> <span word="existence">existence</span>, <span word="however">however</span>, <span word="and">and</span> <span word="we">we</span> <span word="also">also</span> <span word="know">know</span> <span word="that">that</span> <span word="these">these</span> <span word="molecules">molecules</span> <span word="are">are</span> <span word="constantly">constantly</span> <span word="darting">darting</span> <span word="about">about</span> <span word="and">and</span> <span word="colliding">colliding</span>.</p><p> <span word="Now">Now</span>, <span word="consider">consider</span> <span word="the">the</span> <span word="water">water</span> <span word="in">in</span> <span word="an">an</span> <span word="aquarium">aquarium</span>. <span word="Throughout">Throughout</span> <span word="the">the</span> <span word="tank">tank</span>, <span word="water">water</span> <span word="molecules">molecules</span> <span word="are">are</span> <span word="speeding">speeding</span> <span word="about">about</span> <span word="and">and</span> <span word="bumping">bumping</span> <span word="into">into</span> <span word="each">each</span> <span word="other">other</span>, <span word="The">The</span> <span word="constant">constant</span> <span word="collisions">collisions</span> <span word="prevent">prevent</span> <span word="the">the</span> <span word="tiny">tiny</span> <span word="particles">particles</span> <span word="from">from</span> <span word="getting">getting</span> <span word="very">very</span> <span word="far">far</span>. <span word="At">At</span> <span word="the">the</span> <span word="surface">surface</span> <span word="of">of</span> <span word="the">the</span> <span word="tank">tank</span>, <span word="however">however</span>, <span word="many">many</span> <span word="molecules">molecules</span> <span word="can">can</span> <span word="escape">escape</span> <span word="freely">freely</span> <span word="into">into</span> <span word="the">the</span> <span word="air">air</span>. <span word="This">This</span> <span word="is">is</span> <span word="the">the</span> <span word="process">process</span> <span word="of">of</span> <span word="evaporation">evaporation</span> <span word="and">and</span> <span word="it">it</span> <span word="is">is</span> <span word="through">through</span> <span word="this">this</span> <span word="process">process</span> <span word="that">that</span> <span word="water">water</span> <span word="is">is</span> <span word="constantly">constantly</span> <span word="entering">entering</span> <span word="the">the</span> <span word="atmosphere">atmosphere</span>. <span word="The">The</span> <span word="molecules">molecules</span> <span word="of">of</span> <span word="water">water</span> <span word="are">are</span>, <span word="of">of</span> <span word="course">course</span>, <span word="too">too</span> <span word="small">small</span> <span word="to">to</span> <span word="be">be</span> <span word="seen">seen</span>, <span word="and">and</span> <span word="so">so</span> <span word="we">we</span> <span word="speak">speak</span> <span word="of">of</span> <span word="trie">trie</span> <span word="water">water</span> <span word="in">in</span> <span word="the">the</span> <span word="air">air</span> <span word="as">as</span> <span word="an">an</span> <span word="invisible">invisible</span> <span word="vapor">vapor</span>. <span word="When">When</span> <span word="the">the</span> <span word="temperature">temperature</span> <span word="increases">increases</span>, <span word="the">the</span> <span word="speed">speed</span> <span word="at">at</span> <span word="which">which</span> <span word="the">the</span> <span word="molecules">molecules</span> <span word="move">move</span> <span word="also">also</span> <span word="increases">increases</span>. <span word="Faster">Faster</span>-<span word="moving">moving</span> <span word="molecules">molecules</span> <span word="escape">escape</span> <span word="more">more</span> <span word="rapidly">rapidly</span> <span word="and">and</span> <span word="evaporation">evaporation</span> <span word="is">is</span> <span word="speeded">speeded</span> <span word="up">up</span> <span word="when">when</span> <span word="it">it</span> <span word="is">is</span> <span word="warm">warm</span>.</p>
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