英语人教版高二第十三单元课件the properties of water.ppt

ThePropertiesofWater,Unit13Reading,Lookatthetitlesandpicturesinthetext.Donotreadthewholetext.Usethestructuresbelowtomakesixquestions.,1.Whatis/are_?2.Whatdoes_looklike?3.Whataredifferentpartsof_?4.Whatcan_becomparedto?5.Howdoes_work?6.Whataresomeexamplesof_?(Variousanswersarepossible),thepropertiesofwater,theearth,theocean,theocean,thespecialair-conditionertheocean,speciesintheocean,Structureofthepassage,1minutetoskimthepassage,focusingonthetitles(titleandsubtitles)inthetextandthenfillinthechartbelow.Youdonotneedtoreadthewholetext.,CHEMICALSTRUCTURE(化学结构),SALINITY(盐度),THEPROPERTIESOFWATER,DENSITY(密度),HEATCAPACITY(热容量),OCEANMOTION(海洋运动),TopicSentenceofthewholetext:Paragraph:_Sentence:,TopicSentenceofSALINITY:,TopicSentenceofCHEMICALSTRUCTURE:,FindingTopicSentences,7,Learningaboutthepropertiesofwaterhelpsusunderstandlifeonourplanet.,Thechemicalstructureofwatermakesitanexcellentmediumforlife.,Thesalinityoftheearthsoceansisaboutthirty-fivepartsperthousand,meaningthatthereareaboutthirty-fivegrammesofdissolvedsolidsandgasesinonekilogrammeofwater.,READING:,TopicSentenceofHEATCAPACITY:,TopicSentenceofDENSITY:,Thedensityofpurewateris1,000kg/m3,meaningthatonecubicmetreofwaterweighsonethousandkilogrammes.,Heatcapacityisthemountofenergyittakestoraisethetemperatureofasubstancebyonedegreecentigrade.,TopicSentenceofOCEANMOTION:,Sincechangesinsalinityandtemperatureaffectwatersdensity,thewaterintheoceanisalwaysmoving.,1.Whatarethepropertiesofwater?2.Whatdoestheearthlooklike?3.Whatcantheoceanbecomparedto?,Thepropertiesofwaterarechemicalstructure,salinity,density,heatcapacityandoceanmotion.,Theearthlookslikeanoceanplanet.,Theoceancanbecomparedtoagreatplacetolivein.,Waterisaliquidatroomtemperature,andithasarelativelyhighfreezingpoint.Thereasonwhywatercandissolvemostsubstancesonearthisthatwaterhashighheatcapacity.Likealltheothersubstances,watergetssmaller(contract缩小)whenitfreezes.Purewaterhasahigherfreezingpointandlighterthansaltwater.Thesalinityoftheearthsoceansisabout3.5%.Whenwaterfreezes,itsdensityincreases.Otherrecoursessuchasoil,gas,goldetcisaspreciousasadropofrain.,Quiz:TrueorFalse,Scanandfillintheform:,TaskThree,Chemicalstructure:Whatisitgoodfor?,Becausewaterispolar,itcanbreakdownnutrientsquickly.Theycanquicklybecomeavailabletootherlivingcreatures.,Thewatermoleculeismadeupoftwohydrogenatomsandoneoxygenatom.Thewatermoleculeispolar-ithasaslightlynegativeandaslightlypositiveend.,Watersuniquechemicalstructure,OxygenAtom,HydrogenAtom,Apolarmolecule,Density:Densityistherelationshipbetweenmassandvolume.,Whatisitgoodfor?Marineanimalsandplantstakeadvantageofthedensityofwater.Ithelpssmallcreaturestofloat.Becausethedensityofwaterdecreaseswhenitfreezes,theoceanneverfreezestotally.,Heatcapacity:Heatcapacityistheamountofenergyittakestoraisethetemperatureofasubstanceonedegreecentigrade.,Whatisitgoodfor?Theheatcapacityofwaterkeepstheoceansatasteadytemperature,whichmakesitagoodplacetoliveforcreaturesthataresensitivetosuddenchangesintemperature.Thewaterintheoceansalsokeepsthetemperatureofearthsteady.,Oceanmotion:Densewatersinksandl