Physical Characteristics of Gases

1
Chapter 10
Physical Characteristics of Gases
2
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

3

• 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.

4
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.

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• 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

6
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

7

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

8
Chapter 10.3

• Boyles Law
• Pressure X Volume Constant
• P1V1 P2V2
• (T constant)
• Pressure is inversely proportional to volume when
  temperature is held constant.

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• Charless 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

10

• Gay-Lussacs Law
• P1 P2
• T1 T2
• Temperature
• MUST be in KELVINS!

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• The Combined Gas Law
• P1 V1 P2 V2
• T1 T2

12

• Daltons Law of Partial Pressure
• PT P1 P2 P3 .
• Water Displacement
• Patm Pgas PH2O PH2O In table A-8

13

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

14

• Hindeburg. January 9, 2007. http//www.arts.rpi.
  edu/ruiz/Lessons/Photojournalism/S.20Shere20-2
  0hindenburg.jpg
• Solid, Liquid, Gas. February 7, 2007.
  http//www.cofc.edu/martine/111LectWeek1_files/im
  age008.jpg
• Boyles Law. February 7, 2007.
  http//www.grc.nasa.gov/WWW/K-12/airplane/Images/b
  oyle.gif
• Charles Law. February 7, 2007.
  http//home.earthlink.net/dmocarski/chapters/chap
  ter6/graphics/pst2.gif
• Gay Lussacs Law. February 7, 2007.
  http//www.chemcool.com/regents/physicalbehaviorof
  matter/aim9.h26.gif
• Combined Gas Law. February 7, 2007.
  http//www.chem.neu.edu/Courses/1105Tom/05Lecture1
  9_files/image008.jpg
• Daltons Law. February 7, 2007.
  http//mooni.fccj.org/ethall/gaslaw/partial.gif