S-L-G Solids Liquids Gases
Kinetic Theory-Gases • All matter consists of tiny particles that are in constant motion • Particles in a gas are considered to be small, hard spheres with an insignificant volume • The motion of the particles in a gas is rapid, constant and random • All collisions between particles in a gas are perfectly elastic
Gas Pressure • Result of simultaneous collisions of billions of rapidly moving particles in a gas with an object • No particles = no collisions = no pressure is a vacuum • SI unit is a “pascal” (Pa) • 101.3 kPa = 1 atm = 760 mm Hg
Do the following: • What pressure, in kPa and atm, does a gas exert at 385 mm Hg? • 101.3 kPa = 1 atm = 760 mm Hg
Average Kinetic Energy • Related to temperature in °Kelvin (°K) • It is directly proportional, particles at 200 °K have twice the average kinetic energy as particles at 100 °K • 0 °K means the particles have no average kinetic energy
Liquids • Unlike gases, there are attractive forces between particles in a liquid • Reduced space between particles means that liquids are not affected by increased pressures.
Vaporization • Conversion of a liquid to a gas • When boiling is not involved, it is called evaporation • Only those particles with a certain minimum kinetic energy are going to escape the surface of the liquid.
Vapor Pressure • Force exerted by a gas over a liquid evaporation • Liquid Gas condensation Eventually rate of evaporation will equal the rate of condensation