英语六级考试备考阅读美文(十)
<p> <span word="Hydrogen">Hydrogen</span> <span word="and">and</span> <span word="Industries">Industries</span></p><p> <span word="Hydrogen">Hydrogen</span>, <span word="the">the</span> <span word="lightest">lightest</span> <span word="and">and</span> <span word="simplest">simplest</span> <span word="of">of</span> <span word="the">the</span> <span word="elements">elements</span>, <span word="has">has</span> <span word="several">several</span> <span word="properties">properties</span> <span word="that">that</span> <span word="make">make</span> <span word="it">it</span> <span word="valuable">valuable</span> <span word="for">for</span> <span word="many">many</span> <span word="industries">industries</span>. <span word="It">It</span> <span word="releases">releases</span> <span word="more">more</span> <span word="heat">heat</span> <span word="per">per</span> <span word="unit">unit</span> <span word="of">of</span> <span word="weight">weight</span> <span word="than">than</span> <span word="any">any</span> <span word="other">other</span> <span word="fuel">fuel</span>. <span word="In">In</span> <span word="rocket">rocket</span> <span word="engines">engines</span>, <span word="tons">tons</span> <span word="of">of</span> <span word="hydrogen">hydrogen</span> <span word="and">and</span> <span word="oxygen">oxygen</span> <span word="are">are</span> <span word="burned">burned</span>, <span word="and">and</span> <span word="hydrogen">hydrogen</span> <span word="is">is</span> <span word="used">used</span> <span word="with">with</span> <span word="oxygen">oxygen</span> <span word="for">for</span> <span word="welding">welding</span> <span word="torches">torches</span> <span word="that">that</span> <span word="produce">produce</span> <span word="temperatures">temperatures</span> <span word="as">as</span> <span word="high">high</span> <span word="as">as</span> 4, 000 <span word="degrees">degrees</span> <span word="F">F</span> <span word="and">and</span> <span word="can">can</span> <span word="be">be</span> <span word="used">used</span> <span word="in">in</span> <span word="cutting">cutting</span> <span word="steel">steel</span>. <span word="Fuel">Fuel</span> <span word="cells">cells</span> <span word="to">to</span> <span word="generate">generate</span> <span word="electricity">electricity</span> <span word="operate">operate</span> <span word="on">on</span> <span word="hydrogen">hydrogen</span> <span word="and">and</span> <span word="oxygen">oxygen</span>. <span word="Hydrogen">Hydrogen</span> <span word="also">also</span> <span word="serves">serves</span> <span word="to">to</span> <span word="prevent">prevent</span> <span word="metals">metals</span> <span word="from">from</span> <span word="tarnishing">tarnishing</span> <span word="during">during</span> <span word="heat">heat</span> <span word="treatments">treatments</span> <span word="by">by</span> <span word="removing">removing</span> <span word="the">the</span> <span word="oxygen">oxygen</span> <span word="from">from</span> <span word="them">them</span>. <span word="Although">Although</span> <span word="it">it</span> <span word="would">would</span> <span word="be">be</span> <span word="difficult">difficult</span> <span word="to">to</span> <span word="remove">remove</span> <span word="the">the</span> <span word="oxygen">oxygen</span> <span word="by">by</span> <span word="itself">itself</span>, <span word="hydrogen">hydrogen</span> <span word="readily">readily</span> <span word="combines">combines</span> <span word="with">with</span> <span word="oxygen">oxygen</span> <span word="to">to</span> <span word="form">form</span> <span word="water">water</span>, <span word="which">which</span> <span word="can">can</span> <span word="be">be</span> <span word="heated">heated</span> <span word="to">to</span> <span word="steam">steam</span> <span word="and">and</span> <span word="easily">easily</span> <span word="removed">removed</span>. <span word="Hydrogen">Hydrogen</span> <span word="is">is</span> <span word="also">also</span> <span word="useful">useful</span> <span word="in">in</span> <span word="the">the</span> <span word="food">food</span> <span word="industry">industry</span> <span word="for">for</span> <span word="a">a</span> <span word="process">process</span> <span word="know">know</span> <span word="as">as</span> <span word="hydrogenation">hydrogenation</span>. <span word="Products">Products</span> <span word="such">such</span> <span word="as">as</span> <span word="margarine">margarine</span> <span word="and">and</span> <span word="cooking">cooking</span> <span word="oils">oils</span> <span word="are">are</span> <span word="changed">changed</span> <span word="from">from</span> <span word="liquids">liquids</span> <span word="to">to</span> <span word="semisolids">semisolids</span> <span word="by">by</span> <span word="adding">adding</span> <span word="hydrogen">hydrogen</span> <span word="to">to</span> <span word="their">their</span> <span word="molecules">molecules</span>. <span word="Soap">Soap</span> <span word="manufacturers">manufacturers</span> <span word="also">also</span> <span word="use">use</span> <span word="hydrogen">hydrogen</span> <span word="for">for</span> <span word="this">this</span> <span word="purpose">purpose</span>. <span word="Hydrogen">Hydrogen</span> <span word="is">is</span> <span word="also">also</span> <span word="one">one</span> <span word="of">of</span> <span word="the">the</span> <span word="coolest">coolest</span> <span word="refrigerants">refrigerants</span>. <span word="It">It</span> <span word="does">does</span> <span word="not">not</span> <span word="become">become</span> <span word="a">a</span> <span word="liquid">liquid</span> <span word="until">until</span> <span word="it">it</span> <span word="reaches">reaches</span> <span word="temperatures">temperatures</span> <span word="of">of</span> -425 <span word="degrees">degrees</span> <span word="F">F</span>. <span word="Pure">Pure</span> <span word="hydrogen">hydrogen</span> <span word="gas">gas</span> <span word="is">is</span> <span word="used">used</span> <span word="in">in</span> <span word="large">large</span> <span word="electric">electric</span> <span word="generators">generators</span> <span word="to">to</span> <span word="cool">cool</span> <span word="the">the</span> <span word="coils">coils</span>. <span word="In">In</span> <span word="addition">addition</span>, <span word="in">in</span> <span word="the">the</span> <span word="chemical">chemical</span> <span word="industry">industry</span>, <span word="hydrogen">hydrogen</span> <span word="is">is</span> <span word="used">used</span> <span word="to">to</span> <span word="produce">produce</span> <span word="ammonia">ammonia</span>, <span word="gasoline">gasoline</span>, <span word="methyl">methyl</span> <span word="alcohol">alcohol</span>, <span word="and">and</span> <span word="many">many</span> <span word="other">other</span> <span word="important">important</span> <span word="products">products</span>.</p><p> </p>
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