Chapter #10 Physical Characteristics of Gases

Chapter 10.1 Kinetic-molecular theory is based on the idea that particles of matter are always in motion. Kinetic Molecular TheoryKinetic Molecular Theory 1.Volume of individual particles is  zero. 2.Collisions of particles with container walls cause pressure exerted by gas. 3.Particles of matter are ALWAYS in motion 4.Particles exert no forces on each other. 5.Average kinetic energy depends Kelvin temperature of a gas. KE= ½ mv 2

Ideal gas is an imaginary gas that perfectly fits all the assumptions of the kinetic-molecular theory. 1.Gases consist of tiny particles that are far apart relative to their size. 2.Collisions between gas particles and between particles and the walls of the container are elastic collisions 3.No kinetic energy is lost in elastic collisions 4.Gas particles are in constant, rapid motion. They therefore possess kinetic energy, the energy of motion 5.There are no forces of attraction between gas particles 6.The average kinetic energy of gas particles depends on temperature, not on the identity of the particle.

The Nature of Gases 1.Gases expand to fill their containers 2.Gases are fluid – they flow 3.Gases have low density 1/1000 the density of the equivalent liquid or solid 4.Gases are compressible 5.Gases effuse and diffuse Diffusion: describes the mixing of gases. The rate of diffusion is the rate of gas mixing. Effusion: is a process by which gas particles under pressure pass through a tiny opening.

Real gas is a gas that does not behave completely according to the assumptions of the kinetic-molecular theory. The kinetic molecular theory is more likely to hold true for gases whose particles have little attraction for each other. Diatomic molecules N 2 or O 2

Chapter 10.2 Pressure is defined as the force per unit area on a surface.Pressure is defined as the force per unit area on a surface. Is caused by the collisions of molecules with the walls of a container is equal to force/unit area SI units = Newton/meter 2 = 1 Pascal (Pa) 1 standard atmosphere (atm) = Pa 1 atm = kPa 1 atm = 760 mm Hg = 760 torr 1 torr = 1 mm Hg

Standard temperature and pressure (STP) = 1 atm and 0*C

Chapter 10.3 Boyle’s LawBoyle’s Law Pressure X Volume = Constant P 1 V 1 = P 2 V 2 (T = constant) Pressure is inversely proportional to volume when temperature is held constant.

Charles’s LawCharles’s Law V 1 V 2 T 1 T 2 Temperature MUST be in KELVINS! Gas law problems involving temperature require that the temperature be in KELVINS! Kelvins =  C °C = Kelvins =

Gay-Lussac’s Law P 1 P 2 T 1 T 2 Temperature MUST be in KELVINS! =

The Combined Gas Law P 1 V 1 P 2 V 2 T 1 T 2 =

Dalton’s Law of Partial Pressure P T = P 1 + P 2 + P 3 + …. Water Displacement P atm = P gas + P H 2 O P H2O In table A-8

Absolute Zero O Kelvin At this temp. all motion will stop (theory)

“Hindeburg”. January 9, alism/S.%20Shere%20-%20hindenburg.jpg alism/S.%20Shere%20-%20hindenburg.jpg “Solid, Liquid, Gas”. February 7, “Boyles Law”. February 7, /airplane/Images/boyle.gifhttp:// 12/airplane/Images/boyle.gif “Charles Law”. February 7, “Gay Lussacs Law”. February 7, “Combined Gas Law”. February 7, g g “Daltons Law”. February 7,