5-1Chapter 5Gases and the Kinetic-Molecular Theory
5-2Gases and the Kinetic Molecular Theory5.1 An Overview of the Physical States of Matter5.2 Gas Pressure and Its Measurement5.3 The Gas Laws and Their Experimental Foundations5.4 Rearrangements of the Ideal Gas Law5.5 The Kinetic-Molecular Theory: A Model for Gas Behavior5.6 Real Gases: Deviations from Ideal Behavior
5-3Figure 5.1The three states of matter.
5-4Characteristics of Gases•Gas volume changes significantly with pressure.–Solid and liquid volumes are not greatly affected by pressure.•Gas volume changes significantly with temperature.–Gases expand when heated and shrink when cooled. –The volume change is 50 to 100 times greater for gases than for liquids and solids.•Gases flow very freely.•Gases have relatively low densities.•Gases form a solution in any proportions.–Gases are freely miscible with each other.
5-5Gas Pressure and its MeasurementPressure = forceareaAtmospheric pressure arises from the force exerted by atmospheric gases on the earth’s surface.Atmospheric pressure decreases with altitude.
5-6Sea level1 atm4 miles0.5 atm10 miles0.2 atm5.2Atmospheric pressure - the pressure exerted by earth’s atmosphere
5-7Figure 5.2Effect of atmospheric pressure on a familiar object.
5-8Figure 5.3A mercury barometer.•A barometer is used to measure atmospheric pressure.The height of the mercury column is proportional to atmospheric pressure.•Units of Pressure1 torr = 1 mm Hg1 atm = 760 torr (exactly)1 atm = 101,325 Pa 760 torr = 101,325 Pa
5-9Figure 5.4 AThe Hg levels are equal because both arms of the U tube are evacuated.Closed-end manometer.A gas in the flask pushes the Hg level down in the left arm.The difference in levels, Dh, equals the gas pressure, Pgas.
5-10Figure 5.4 BOpen-end manometer.An open-ended manometer is another method of measuring pressure. When Pgasis greater than Patm, add Dhto Patm.Pgas> PatmPgas= Patm+ Dh
5-11Table 5.1Common Units of Pressure
Sample Problem 5.1Converting Units of PressurePROBLEM:A geochemist heats a limestone (CaCO3) sample and collects the CO2released in an evacuated flask attached to a closed-end manometer. After the system comes to room temperature, Δh= 291.4 mm Hg. Calculate the COpressure in torrs, atmospheres, and kilopascals.PLAN:Construct conversion factors to find the other units of pressure.2
5-13The Gas Laws•The gas laws describe the physical behavior of gases in terms of 4 variables:–pressure (P)–temperature (T)–volume (V)–amount (number of moles, n)•An ideal gas is a gas that exhibits linear relationships among these variables.•No ideal gas actually exists, but most simple gases behave nearly ideally at ordinary temperatures and pressures.
5-15Figure 5.5Boyle’s law, the relationship between the volume and pressure of a gas.
5-16Boyle’s LawAt constant temperature, the volume occupied by a