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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 Theory Volume of individual particles is zero.
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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 Theory • Volume of individual particles is zero. • Collisions of particles with container walls cause pressure exerted by gas. • Particles of matter are ALWAYS in motion • Particles exert no forces on each other. • Average kinetic energy depends Kelvin temperature of a gas. KE= ½ mv2
Ideal gas is an imaginary gas that perfectly fits all the assumptions of the kinetic-molecular theory. • Gases consist of tiny particles that are far apart relative to their size. • Collisions between gas particles and between particles and the walls of the container are elastic collisions • No kinetic energy is lost in elastic collisions • Gas particles are in constant, rapid motion. They therefore possess kinetic energy, the energy of motion • There are no forces of attraction between gas particles • The average kinetic energy of gas particles depends on temperature, not on the identity of the particle.
The Nature of Gases • Gases expand to fill their containers • Gases are fluid – they flow • Gases have low density 1/1000 the density of the equivalent liquid or solid • Gases are compressible • 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 N2 or O2
Chapter 10.2 • 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/meter2 = 1 Pascal (Pa) • 1 standard atmosphere (atm) = 101 325 Pa • 1 atm = 101.325 kPa • 1 atm = 760 mm Hg = 760 torr • 1 torr = 1 mm Hg
Chapter 10.3 • Boyle’s Law • Pressure X Volume = Constant • P1V1 = P2V2 (T = constant) • Pressure is inversely proportional to volume when temperature is held constant.
Charles’s Law V1 V2 T1 T2 • Temperature MUST be in KELVINS! • Gas law problems involving temperature require that the temperature be in KELVINS! Kelvins = C + 273 °C = Kelvins - 273 =
Gay-Lussac’s Law P1 P2 T1 T2 Temperature MUST be in KELVINS! =
The Combined Gas Law P1 V1 P2 V2 T1 T2 =
Dalton’s Law of Partial Pressure PT = P1 + P2 + P3 + …. • Water Displacement Patm= Pgas + PH2O PH2O In table A-8
Absolute Zero • O Kelvin • At this temp. all motion will stop (theory)
“Hindeburg”. January 9, 2007. http://www.arts.rpi.edu/~ruiz/Lessons/Photojournalism/S.%20Shere%20-%20hindenburg.jpg • “Solid, Liquid, Gas”. February 7, 2007. http://www.cofc.edu/~martine/111LectWeek1_files/image008.jpg • “Boyles Law”. February 7, 2007. http://www.grc.nasa.gov/WWW/K-12/airplane/Images/boyle.gif • “Charles Law”. February 7, 2007. http://home.earthlink.net/~dmocarski/chapters/chapter6/graphics/pst2.gif • “Gay Lussacs Law”. February 7, 2007. http://www.chemcool.com/regents/physicalbehaviorofmatter/aim9.h26.gif • “Combined Gas Law”. February 7, 2007. http://www.chem.neu.edu/Courses/1105Tom/05Lecture19_files/image008.jpg • “Daltons Law”. February 7, 2007. http://mooni.fccj.org/~ethall/gaslaw/partial.gif