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## Kinetic Theory and Gas Pressure

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### elastic collision- no loss of kinetic energy or momentum ... http://www.aeromech.usyd.edu.au/aero/atmos/stdatm.html. Addison Wesley's Chemistry Text Book ... – PowerPoint PPT presentation

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Title: Kinetic Theory and Gas Pressure

1
Kinetic Theory and Gas Pressure
• Grace Byrne, Mary McDyer, Mike Pileggi,

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

3
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
4
Kinetic Theory Introduction
http//hyperphysics.phy-astr.gsu.edu/hbase/kinetic
/kinthe.html
5
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

6
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
7
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

8
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
9
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

10
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
11
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
12
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
13
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
14
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

15
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

16
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

17
Units of Pressure
• Pascal (Pa) the SI unit of pressure
• Two older units of measure are
• Millimeters of mercury (mm Hg)
• And atmospheres (atm)

18
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.

19
Converting atm to Pa
• 1 atm 1.01325 Pa
• Atm- standard atmosphere
• Pa- pascal
• 1.01325 the standard condition of pressure of 1
atm

20
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

21
tml/MercuryBarometer.jpg
22
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

23
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

24
Bibliography
• 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