20xx年12月英語六級考試完形填空模擬練習(xí)

20xx年12月英語六級考試完形填空模擬練習(xí)20xx年12月英語六級考試完形填空模擬練習(xí)英語是現(xiàn)在世界上用的最多的'一門語言，許多國家都在學(xué)英語和用英語，所以，學(xué)好了英語，出門就不怕溝通不便利了。下面是為大家搜尋整理的英語六級輔導(dǎo)訓(xùn)練，希望能給大家?guī)韼椭?！ThedifferencebetweenaliquidandagasisobviousundertheconditionsoftemperatureandpressurecommonlyfoundatthesurfaceoftheEarth.Aliquidcanbekeptinanopencontainerandfillittothelevelofafreesurface.Agasformsnofreesurfacebuttendstodiffusethroughoutthe11available;itmustthereforebekeptinaclosedcontainerorheldbyagravitationalfield,asinthe12ofaplanetsatmosphere.Thedistinctionwasa13featureofearlytheoriesdescribingthephasesofmatter.Inthenineteenthcentury,forexample,onetheorymaintainedthataliquidcouldbedissolvedinavaporwithoutlosingitsidentity,andanothertheory14thatthetwophasesaremadeupofdifferentkindsofmolecules.Thetheoriesnowprevailingtakeaquitedifferentapproachbyemphasizingwhatliquidsandgaseshavein15Theyarebothformsofmatterthathaveno16structure,andtheybothflowreadily.Thefundamentalsimilarityofliquidsandgasesbecomesclearlyapparentwhenthetemperatureandpressureare17somewhat.Supposeaclosedcontainer18filledwithaliquidisheated.Theliquidexpands,orinotherwordsbecomeslessdense;someofitevaporates.Incontrast,thevaporabovetheliquidsurfacebecomesdenserastheevaporatedmoleculesare19toit.Thecombinationoftemperatureandpressureatwhichthedensitiesbecome20iscalledthecriticalpoint.A.addedB.caseprominentheldequalpartiallyexamplepreviousspaceliftedpermanentL.particularly