1Chapter 10: Gases1.Characteristics of Gases2.Gas Pressure and Its Measurement3.The Gas Laws and Ideal Gas Law4.Gas Law Applications5.Gas Mixtures6.Kinetic-Molecular Theory 7.Effusion and Diffusion8.Non-Ideal Gases CH421. Some Key Gas PropertiesA gasis a physical state of an element or compound.Contrast with liquid or solid states of matter (see Chp. 1):•gases expand to fillthe entire container they are placed in.- move rapidly around container & exert force on its walls.•gases have low densities(<< moles/cm3vs. liquids).- thus they are easily compressedinto smaller volumes.•gases (ideally) interact weakly with other gases and often are highly miscible(forming homogeneous gas mixtures).32. Gases and their Pressure PropertiesElemental gases: He, Ne, Ar, Kr, Xe and H2, O2, N2, F2, Cl2Selected common molecular gases: CH4, NO2, NO, N2O, CO, CO2, NH3, HCl, H2OAir (mixture)78% N2, 21% O2, 1% ArP=F/A2009 Hail Stormmore force (ma)= 1 atm4Gas Pressure (P) DefinedPressure Units:areaonacceleratimassareaforcepressurePa1pascal1smkgm)s/m(kg2221.013 × 105Pa = 101.3 kPa= 1.013 bar= 14.7 lb/in2= 1 atm= 760 mm Hg = 760 torrSI derived unitExample:If you inflate your car’s tires to 27.5 lb/in2, what is this in torr and atm?Ans:torr1214lb/in14.7torr760lb/in27.522(or 1.87 atm)5Mercury (Hg) to Measure PressureBarometerinvented by Torricelli (17thcentury)air pressure on Hg pool= mm HgManometerPgas= 760 + 32.6 torr(no gas)6Manometers – Gas PressuresPgas= PatmPgas< PatmPgas= Patm-hPgas> PatmPgas= Patm+ hopen-end manometerswhen Pgas= 0 torr (mmHg) then h = Patm= 760 mmNote: 0 torr = no gas molecules = a vacuum!