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1、英语流利说Level3.Unit2Part1作者：DingMingListening:StatesofMatter物质状态Matterismadeofatomsandmolecules.Water,forexample,istheH2Omolecule.Thismeansthatamoleculeofwaterhas3atoms.这意味着水分子有3个原子。Awatermoleculehastwohydrogenatomsandoneoxygenatom.Substanceslikesugarhavemanyatoms
2、intheirmolecules.Amoleculeofsugarhasmanyatoms,includingcarbon,hydrogenandoxygen.------------------------------------------------------------------------------------------------------Matterismadeofmolecules,suchasH2O,whichisthewatermolecule.Mattercanbeoneofthree
3、states,solid,liquidorgas.Waterandicearethesamesubstance,buttheyareindifferentstates.Thesestatesdependonthetemperatureofthemolecules.Whenweheatasubstance,themoleculesmovefasterandtrytotakeupmorespace.Whenwecoolasubstance,themoleculesmovemoreslowly.Whenwecoolasub
4、stancetoitsfreezingpoint,itbecomesasolid.-------------------------------------------------------------------------------------------------------------Inasolid,themoleculesmoveverylittle.Theirpositionsarealmostfixed.Tobefixedmeansthattheirpositionsdon’tchange.If
5、weheatthemolecules,theymovefasterandawayfromeachother.英语流利说Thesolidbeginstomelt,likeicecreamonahotday.-----------------------------------------------------------------------------------------------------------Atacertaintemperature,asolidbeginstochangeintoaliqui
6、d.Thetemperatureatwhichasolidchangeintoaliquiddependsonthesubstance.Forwater,thesolidbeginstochangeintoaliquidwhenitstemperaturerisestoabout0degreeCelsius.Forsomesubstances,suchassteel,thetemperatureatwhichitbecomesaliquidismuchhigher.对于某些物质,如钢,它变成液体的温度要高得多。Ste
7、eloftenmeltsataround1370degreesCelsius.-----------------------------------------------------------------------------------------------------------Ifwecontinuetoheataliquid,themoleculesmoveevenfaster.Atacertaintemperature,theliquidbeginstochangeintoagas.Forwater
8、,theliquidbeginstochangeintoagasat100degreesCelsius.Thatistheboilingpointofwater.--------------------------------------------------------------------------------------------
