I. Physical Properties Gases

A. Kinetic Molecular Theory b kinetic-molecular theory: (def) theory of the energy of particles and the forces that act between them; based on idea that particles of matter are always in motion b Kinetic molecular theory describes the motion of an ideal gas

A. Kinetic Molecular Theory b ideal gas: (def) imaginary gas that perfectly fits the assumptions of the kinetic-molecular theory

A. Kinetic Molecular Theory b Particles in an ideal gas… have no volume. have elastic collisions. are in constant, random, straight- line motion. don’t attract or repel each other. have an avg. KE directly related to Kelvin temperature.

B. Real Gases b Particles in a REAL gas… have their own volume attract each other proposed by van der Waals b Gas behavior is most ideal… at low pressures at high temperatures in nonpolar atoms/molecules

C. Characteristics of Gases b Gases expand to fill any container. random motion, no attraction b Gases are fluids (like liquids). no attraction b Gases have very low densities. no volume = lots of empty space

C. Characteristics of Gases b Gases can be compressed. no volume = lots of empty space b Gases undergo diffusion & effusion. random motion

C. Characteristics of Gases b Diffusion: (def) process by which gases spontaneously spread out and mix with other gases; lighter gases diffuse more quickly b Effusion: (def) process by which gases particles under pressure pass through a tiny opening; lighter gases effuse faster

A. Temperature ºF ºC K K = ºC b Always use absolute temperature (Kelvin) when working with gases.

B. Pressure Which shoes create the most pressure? SI unit of force is the Newton

. Pressure b Barometer measures atmospheric pressure - at sea level, height of column is 760 mm - P of Hg is equal to the P of the atmosphere Mercury Barometer

E. Pressure b Manometer measures contained gas pressure - difference in height of tubes indicates the gas pressure U-tube Manometer

E. Pressure b KEY UNITS AT SEA LEVEL kPa (kilopascal) 1 atm 760 mm Hg 760 torr 14.7 psi

PressurePressure UnitSymbolDefinitions PascalPaSI Pressure Unit; 1 Pa = 1 N/m 2 Millimeter of Mercury mm HgP that supports a 1 mm mercury column in a barometer Atmo- sphere atm1 atm = 760 mm Hg = kPa Torrtorr1 torr = 1 mm Hg

C. STP Standard Temperature & Pressure 0°C K 1 atm kPa -OR- STP

D. Dalton’s law b Dalton’s law of partial pressure: P total = P 1 + P 2 + P 3 …+P n (n = number of gases in mixture) **Total P exerted by collection gases is sum of pressure exerted by each gas