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1、......Level3unit1part1ListeningMatterismadeofatomsandmolecules.Water,forexample,istheH2Omolecule.Thismeansthatamoleculeofwaterhas3atoms.Awatermoleculehas2hydrogenatomsandoneoxygenatom.Substanceslikesugarhavemanyatomsintheirmolecules.Amoleculeofsugarhasma
2、nyatoms,includingcarbine,hydrogenandoxygen.-WhatisH2O?Thewatermolecule.-Whatismattermadeof?-AtomsandmoleculesMatterismadeofmoleculessuchastheH2Owhichisthewatermolecule.Mattercanbeinoneof3states,solid,liquidorgas.Waterandicearethesamesubstance,buttheyarei
3、ndifferentstates.Thesestatesdependonthetemperatureofthemolecules.Whenweheatasubstance,themoleculesmovefasterandtrytotakeupmorespace.Whenwecoolasubstance,themoleculesmovemoreslowly.Whenwecoolasubstancetoitsfreezingpoint,itbecomesasolid.-Howmanystatesofmat
4、terarethere?-Three.--Whathappenswhenweheatasubstance?themoleculesmovefasterandtrytotakeupmorespace.-Whathappensifwecoolaliquidtoitsfreezingpoint?Itbecomesasolid..学习参考.......Inasolid,themoleculesmoveverylittle.Theirpositionsarealmostfixed.Tobefixedmeansth
5、attheirpositionsdontchange.Ifweheatthemolecules,theymovefasterandawayfromeachother.Thesolidbeginstomelt,likeicecreamonahotday.-Howcanwechangeasolidintoaliquid?heatitup.-Howcanwechangealiquidintoasolid?coolitdown.-Atacertaintemperature,asolidbeginstochang
6、eintoaliquid.Thetemperatureatwhichasolidchangesintoaliquiddependsonthesubstances.Forwater,thesolidbeginstochangeintoaliquidwhenitstemperaturerisestoabove0degreesCelsius.Forsomesubstances,suchassteel,thetemperatureatwhichitbecomesaliquidismuchhigher.Steel
7、oftenmeltsataround1370degreesCelsius.-Atwhattemperaturedoesicebegintomelt?Above0degreeCelsius.-Whatdoesthetemperatureatwhichasubstancebeginstomeltdependon?Thesubstances.Ifwecontinuetoheataliquid,themoleculesmoveevenfaster.Atacertaintemperature,theliquidb
8、eginstochangeintoagas.Forwater,theliquidbeginstochangeintoagasat100degreesCelsius..学习参考.......Thatistheboilingpointofwater.-Whathappensifwecontinuetoheataliquid?Moleculesmoveevenfaster.Insideastar,suchasoursun,thetemperatu
