Chapter 5 Gases and the Kinetic-Molecular Theory - Kevin...

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Kevin Avalo09/29/14Gases and the Kinetic-Molecular TheoryReading Notes5.1 An overview of the physical states of MatterGas volume changes significantly with pressure.Increased pressure decreases volume of gas.Decreased pressure increases volume of gas.Gas volume changes significantly with temperature.Increased temperature increases volume of gas.Decreased temperature decreases volume of gas.Gases flow very freely.Allows gases to be transported more easily through pipes.Con- they leak more rapidly out of small holes or cracks.Gases have relatively low densities.When a gas cools, its density increases because its volume decreases.Gases form a solution in any proportions.5.2 GAS PRESSURE AND ITS MEASUREMENTPressure of gas is the force of collisions between gas particles and walls.P=force/areaGases in the atmosphere exert a force on all surfaces, known as atmospheric pressure.Measuring Gas Pressure: Barometers and ManometersBarometer: measures atmospheric pressure.At sea level and 0⁰C, normal atmospheric pressure is 760mmHg.Pressure decreases with altitude.Manometer: measure the pressure of a gas in an experiment.Closed-end manometer: Hg levels are equal on both arms. The gas pressure is equal todifference in levels.Open-end manometer:When Pgasis less than Patmsubtract difference in levels from Patm.When Pgasis greater than Patmadd difference in levels to Patm.Units of Pressure1 pascal (Pa) = 1 N/m2Standard atmosphere:1 atm = 101.325 kilopascals (kPa) = 1.01325X105Pa1 torr = 1 mmHg = 1/760 atm = 101.325/760 kPa1 bar = 1X102kPa5.3 THE GAS LAWS AND THEIR EXPERIMENTAL FOUNDATIONSIdeal gas-one that exhibits linear relationships among volume, pressure, temperature, andamount.No ideal gas actually exists.The Relationship Between Volume and Pressure: Boyle’s Law
Boyle’s Law-at constant temperature, the volume occupied by a fixed amount of gas isinversely proportional to the applied (external) pressure.V=constant/PPV=constantV is inversely proportional to PV is directly proportional to 1/PIf Vgasincreases, Pgasdecreases and vice versa.The Relationship Between Volume and Temperature: Charle’s LawCharles’ Law-at constant pressure, the volume occupied by a fixed amount of gas is directlyproportional to its absolute (Kelvin) temperature.

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