CAA_Ch11.2B_Lecture.ppt

Chapter11 GASESTHEKELVINSCALEANDCHARLES LAW T TEMPERATURE ALWAYSUSING KELVINS Rememberthisfact CelciusdegreeswillNOTworkwithgasequations TheONLYtemperaturescalethatwillworkisthe Kelvin K Scale Thetemperatureofagasisfoundusingacelciusthermometerthen convertedtoKbyadding273to C K C 273 KelvinsaretheunitsoftheABSOLUTETEMPERATURESCALE ANDMUSTBEUSEDINALLGASPROBLEMS Whatis Kelvin Temperature It sjustCelsius 273 NOT degrees just Kelvins Tryit 100 C howmanyKelvins 50 C howmanyKelvins Now atrickyone 100Kelvins howmany C ThereisNOSUCHTHINGasanegativetemperatureinKelvins 373K223K 173 C Charles Law ChangingVolumeandTemperature Usethisequationwhenonlyvolumeandtemperaturearechanging ALLproblemsinvolvinggastemperatureMUSTusetheKelvinScale Charles Law V Tisconstant Charles Law V T 3L 200K 0 015Ifthetemperatureofagasisdoubled ChangingVolumeandTemperature thevolumeofagasisdoubled Charles Law V T 6 400 0 015 ChangingVolumeandTemperature THERATIOOFVOLUMEOVERTEMPERATURE INKELVINS ISCONSTANT Charles Law V 3L 0 015T200K V 6L 0 015T400K THERATIOOFVOLUMEOVERKELVINTEMPERATUREISCONSTANT WhyKelvinTemperature 273 15 C Ifthevolume orpressure ofagasisplottedagainstCelciustemperature thevolumeofagaswillequalzero theoretically at 273 15 C Thisis0Kelvins or AbsoluteZero NotethereisstillvolumeatO C TheKelvinScale ZeroKelvins iscalled absolutezero nocoldertemperatureispossible Allgasesreach zero volumeatthesametemperature 273 15 C K C 273 thedegreesarethesamesize Therefore C K 273 Practice a 0 C 273 273K b 25 C 273 298K c 100 C 273 373K FindtheKelvinTemperatureof a 0 Cb 25 Cc 100 C Practice CalculatetheratioofV TfromthetableoftemperaturesandvolumesusingKelvintemperatures CalculatetheratioofV TfromthetableoftemperaturesandvolumesusingCelciustemperatures Volume CK1 00L01 11L301 22L60 273 303 333 Practice WhichtemperaturescalewillgiveaconstantratioofV T TheKelvinTemperatures Charles LawstatesthatwhenusingtheKelvintemperaturescale V Tisconstant Therefore V1 V2T1T2 ThisisaDirectproportion AsKelvintemperaturedrops sodoesvolume Whensettingupproblems alwayslabelyourvariables EXAMPLEPROBLEM V1 V2T1T2 WhatisV1 WhatisT1 WhatisV2 WhatisT2 Aballooninafreezerhasavolumeof0 500Lat 13 C Whatisthevolumeoftheballoonifitistakenoutofthefreezerandallowedtowarmupto27 C 0 500L 13 C 273 260KUnknown27 C 273 300K SolveforV2 V2 V1xT2T1 V2 0 500LX300K260K 0 577L TryOne V1 V2T1T2 WhatisV1 WhatisT1 WhatisV2 WhatisT2 Whatisthenewvolumeo