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 mv2

• 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 collisions4.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 GasesThe 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 N2 or O2

Chapter 10.2• Pressure Pressure is defined as the force per unit is defined as the force per unit

area on a surface.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

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

Chapter 10.3• Boyle’s LawBoyle’s Law• Pressure X

Volume = Constant

• P1V1 = P2V2

(T = constant)• Pressure is

inversely proportional to volume when temperature is held constant.

• Charles’s LawCharles’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