lect7_16Sept08 - First TEST CHAPTERS 1 5 Tuesday 23 September HELP SESSION Sunday 21 September 5:00 6:45 PM Heldenfels 100 Do Not Forget CAPA

lect7_16Sept08 - First TEST CHAPTERS 1 5 Tuesday 23...

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1First TEST CHAPTERS 1 – 5Tuesday 23, SeptemberDo Not Forget CAPA ASSIGNMENTS CAPA 4 BEING DISTRIBUTEDHELP SESSION, Sunday 21 September5:00 –6:45 PM Heldenfels 100GASES AND KINETIC-MOLECULAR THEORYSuggested Textbook Problems - CHAPTER 5READ CHAPTER 513, 19, 25, 29, 33, 35, 43, 47, 52, 55, 59, 65, 68, 73, 77, 85, 87The Gas LawsSolidsLiquidsGas - a substance that is characterized by widely separated molecules in rapid motionMixtures of gases are uniform. Gases will expand to fill containersGasesThree States of MatterThree States of MatterExamples of Gaseous SubstancesCommon gases O2 and N2, the major components of "air" Other gases H2F2, Cl2, gaseous diatomic molecules; • H2and He are the ‘lighter than air’ gases
2Gases and VaporsWhat is the difference between a gas and a vapor? – Gases normally in the gaseous state at 25°C and 1 atm pressure – A vapor is the gaseous form of any substance that is normally in the liquid or solid state at normal temperatures and pressures The Gas LawsEarly experiments found that four variables were sufficient to fully describe thestateof a gas Pressure (P)Volume (V) Temperature (T)The amount of the gas in moles (n) Gas pressure results from collisions of gas molecules with the container walls. Pressure depends onthe number of collisions per unit time AND- how hard the gas molecules strike the container wall!PressurePressure is the force per unit area which a Pressure is the force per unit area which a gas exertsgas exertson the walls of the containerAFP=The SI unit of pressure is the Pascal 1 Pa = 1 Newton /m2= 1 kg m s2Composition of the Atmosphere Gas% by VolumeN278.09O220.94Ar0.93CO20.03He, Ne, Kr, Xe0.002CH40.00015H20.00005Composition of Dry AirGravity exerts a force on the earthGravity exerts a force on the earth’s atmospheres atmosphereA column of air 1 mA column of air 1 m2in cross section in cross section exerts a force of 1.01325 x 10exerts a force of 1.01325 x 105N. N. The pressure of a 1 mThe pressure of a 1 m2column of air column of air is 1.01325 x 10is 1.01325 x 105Pa.Pa.Atmospheric PressureAtmospheric Pressure14.70 lbs/ in2Also 760 mm HgOr 760 Torr
3Hg density = 13.6 g/mLCAN WE MAKE A WATER BAROMETER?VacuumYES• But Density of water = 1.00 grams/cm3Therefore Height of Column is = (13.6/1) x 76.0 cm =1.03 x 103 cmor 33.9 feetWhat practical implications does this have for simple hand operated water pumps?The Definition of an Ideal GasIdeal gases - molecules have negligible intermolecular attractive forces –Occupy a negligible volume compared to the container volumeBoyle's Law –The pressure - volume relationship

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