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Chapter 5Gases and the Kinetic-molecular TheoryDr. Shamindri M. Arachchige[email protected]Surge 117
2Chapter 5Gases and the Kinetic-molecular TheoryThe Three States of Matter.Macroscopic ViewMicroscopic View
Three Phases of Matter: Gas Liquid Solid Particles are far apart The particles of a gas fill up the space in which they are contained. Compressible Particles are close together Not compressible Particles are tightly packed Not compressible Chapter 5Gases and the Kinetic-molecular Theory
Chapter 5Gases and the Kinetic-molecular Theory
5Chapter 5Gases and the Kinetic-molecular TheoryGases consist of particles. The kinetic molecular theory accounts for the macroscopic gas behavior at the level of individual particles (atoms and molecules).Gas particles are tiny with large spaces between them. Gas particles have negligible volumes.Gas particles are in constant, random, straight-line motion except when they collide with each other or with the container walls. All collisions are elastic.Pressure:The particles are assumed to exert noforces on each other; they are assumed to neither attract nor repel each other.The average kinetic energy of a collection of gas particles is directly proportional to the kelvin temperature of the gas. (Kinetic energy = ½ mv2)According to the kinetic-molecular theory, molecules of different gases at the same temperature always have the same average kinetic energy. Average kinetic energy depends only on the temperature.
6Figure 5.14Distribution of molecular speeds for N2at three temperatures.Chapter 5Gases and the Kinetic-molecular Theory
Gas Pressure Atmospheric pressure: Barometer: Units of pressure: 1 atm = 760 mm Hg=760 Torr= 14.7 lb/in2= 29.9 in Hg = 1.01325 x 105Pascals (Pa) 1 Pa = 1 N/m27Chapter 5Gases and the Kinetic-molecular TheoryGas pressure is a result of the gas particles colliding with the walls of the container.Device used to measure atmospheric pressure. Pressure = forcearea
8Chapter 5 Gases and the Kinetic-molecular TheoryP V V 1/P Gas Laws: Relationships Between Gas Pressure, Volume, Temperature, and Moles
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