Kinetic Theory and Gas Pressure

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Kinetic Theory and Gas Pressure

• Grace Byrne, Mary McDyer, Mike Pileggi,
  Bernadette Smith and Tri Tran

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Topics

• Kinetic Theory
• Introduction
• Part 1
• Part 2
• Part 3
• Gas Pressure
• Barometers
• Quiz

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Kinetic Theory Introduction

• Kinetic energy the energy an object has because
  of motion
• Kinetic theory states that tiny particles in
  all forms of matter are constantly in motion

http//www.hometrainingtools.com/images/phases20o
f20matter.jpg
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Kinetic Theory Introduction
http//hyperphysics.phy-astr.gsu.edu/hbase/kinetic
/kinthe.html
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Kinetic Theory Part 1

• Applied to Gases
• Made up of objects with defined mass and no
  volume
• Particles travel in random straight-line motion
• All collisions are elastic, kinetic energy is
  conserved
• Gas particles do not interact with each other or
  walls of container
• Gas has kinetic energy proportionate to
  temperature

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Kinetic Theory Part 1

• Gas is composed of particles, usually molecules
  or atoms
• Particles considered to be small hard spheres
• Small particles relative to distance apart
• Frequent collisions between molecules
• Travel in straight line until collide

http//www.schulenberg.com/gifs/kinetic_theory.gif
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Kinetic Theory Part 1

• Each individual molecules has the standard
  physical properties of mass, momentum, and energy
• Dmass of molecules/volume which the gas occupies
• Pressure of gas is a measure of the linear
  momentum of the molecules
• Force/areapressure

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Kinetic Theory Part 1

• Temperature of a gas is a measure of the mean of
  kinetic energy
• The higher the temperature, the greater the
  kinetic energy

http//www.grc.nasa.gov/WWW/K-12/airplane/kinth.ht
ml
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Kinetic Theory Part 2

• All particles constantly move in random motion.
• The only time that particles are not in motion is
  when they are at Absolute Zero
• Absolute Zero temperature at which gases use no
  pressure
• Particles move independently.
• They do not move in groups and each particle has
  its own path

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Kinetic Theory Part 2

• Particles move in straight paths.
• The only way they change direction is if they
  collide with another particle or with the side of
  the container they are in.
• Gases fill their containers no matter its shape
  or volume.

http//www.bcpl.net/kdrews/kmt/kmtpart2.htmlPart
202
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Kinetic Theory Part 2

• Uncontained gases diffuse into space.
• If a gas is contained it will expand to fill the
  volume or leave the container.
• Gases should diffuse to the point of even
  distribution, but cant because of effects of the
  environment.

http//www.bcpl.net/kdrews/kmt/kmtpart2.htmlPart
202
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Kinetic Theory Part 3

• The particles collide elastically.
• elastic collision- no loss of kinetic energy or
  momentum
• Energy from elastic collisions transfers from one
  object to another and no heat or sound is
  generated.
• examples billiard balls, swinging balls

http//www.bcpl.net/kdrews/kmt/kmtpart3.htmlPart
203
http//hyperphysics.phy-astr.gsu.edu/hbase/elacol.
html
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Kinetic Theory Part 3

• Hard spheres are nearly elastic
• Elastic means return exactly to original shape
• An inelastic collision- change in kinetic energy
• heat is generated
• examples car crash, puddy

http//www.bcpl.net/kdrews/kmt/kmtpart3.htmlPart
203
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Gas Pressure

• Gas particles exert small amounts of force when
  they are alone
• Many collisions of gas particles occurring at the
  same time produce measurable amounts of force
• Gas pressure is the result of simultaneous
  collisions of a number of gas particles on an
  object

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Gas Pressure

• Gas pressure - the force exerted by a gas per
  unit surface area of an object
• If no gas particles are present , then there is
  no pressure
• Vacuum - the empty space with no gas particles

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Gas Pressure

• Air exerts pressure on earth because of gravity
  holding air in Earths atmosphere
• Atmospheric pressure results from collisions of
  air molecules with objects
• As elevation increases, atmospheric pressure
  decreases because of thinning air
• Barometers measure atmospheric pressure

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Units of Pressure

• Pascal (Pa) the SI unit of pressure
• Two older units of measure are
• Millimeters of mercury (mm Hg)
• And atmospheres (atm)

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Standard Atmosphere (atm)

• Standard Atmosphere (atm)
• A unit of pressure
• The pressure required to support 760 mm of
  mercury in a mercury barometer at 25 C.

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Converting atm to Pa

• 1 atm 1.01325 Pa
• Atm- standard atmosphere
• Pa- pascal
• 1.01325 the standard condition of pressure of 1
  atm

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How Barometers Work

• A straight glass tube filled with mercury and
  closed at one end
• The tube was placed in a dish of mercury so that
  the open end was below the surface of the mercury
  in the dish.
• The height of mercury in the tube depends on the
  pressure created by collisions of air molecules
  with the surface of the mercury in the dish

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http//www.atmos.washington.edu/2005Q3/101/LINKS-h
tml/MercuryBarometer.jpg
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Quiz

• 1. The kinetic energy of a gas is ________ to the
  temperature.
• a. Proportional b. Disproportional c.
  Not Related
• 2. Gas particles travel in straight paths until
  they ________. a. combust b. disappear c.
  collide
• 3. The higher the temperature the ________ the
  kinetic energy. a. less b. greater c. they
  are equal
• 4. Gases fill their containers no matter its
  ______or volume. a. shape b. temperature
  c. neither
• 5. The temperature at which gases use no pressure
• a. Absolute Zero b. boiling point c.
  freezing

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Quiz

• 6. Gas particle collide __________.
• a. they dont collide b. elastically c.
  reflectively
• 7. The force exerted by a gas per unit surface
  area of an object
• a. Gas pressure b. pressure leak c. air
  pressure
• 8. The empty space with no gas particles is
• a. vacuum b. black hole c. duster
• 9. _________ measure atmospheric pressure.
• a. Thermometer b. Barometer c. calorimeter
• 10. What element is used in barometers?
• a. Mercury b. Iron c. Copper

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Bibliography

• http//www.answers.com/topic/absolute-zero
• http//www.bcpl.net/kdrews/kmt/kmt.html
• http//www.grc.nasa.gov/WWW/K-12/airplane/kinth.ht
  ml
• http//www.schulenberg.com/gifs/kinetic_theory.gif
  
• http//hyperphysics.phy-astr.gsu.edu/hbase/elacol.
  html
• http//www.launc.tased.edu.au/online/sciences/phys
  ics/elas.htm
• http//www.iadeaf.k12.ia.us/Momentum.htm
• http//hyperphysics.phy-astr.gsu.edu/hbase/kinetic
  /kinthe.html
• http//comp.uark.edu/jgeabana/mol_dyn/
• http//www.bom.gov.au/info/aneroid/aneroid.shtmlme
  
• http//www.physics.nist.gov/Pubs/SP811/appenB.html
  
• http//www.aeromech.usyd.edu.au/aero/atmos/stdatm.
  html
• Addison Wesleys Chemistry Text Book