The Property of Gases

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(No Transcript)
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The Property of Gases Kinetic Molecular Theory
And Pressure
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Kinetic Molecular Theory of Gases

• The word kinetic refers to motion.
• Kinetic energy is the energy an object has
  because of its motion.
• Kinetic Molecular Theory makes assumptions about
• Size
• Motion
• Energy of gas particles

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Kinetic Molecular Theory Part 1

• According to the KMT all matter consists of tiny
  particles that are in constant, random motion
• Move in a straight line until they collide with
  other particles or with the walls of the
  container.

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Kinetic Molecular Theory Part 2

• 2. Gas particles are much smaller than the
  distances between them. Most of a gas consists of
  empty space.
• Gas consists of small particles that are
  separated from one another by empty space
• Most of the volume of a gas consists of empty
  space
• Because they are so far apart, there are no
  attractive or repulsive forces between the gas
  molecules
• The motion of one particle is independent of the
  motion of other particles

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Kinetic Molecular Theory Part 3

• No kinetic energy is lost when gas particles
  collide with each other or with the walls of the
  container (elastic collision)
• Undergoes elastic collision no kinetic energy
  is lost when particles collide.
• The total amount of kinetic energy remains
  constant.

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Kinetic Molecular Theory Part 4

• All gases have the same average kinetic energy at
  a given temperature
• Temperature is a measure of average kinetic
  energy of particle in a sample of matter.
• Kinetic energy and temperature are directly
  related
• The higher the temperature, the greater the
  kinetic energy
• The Kelvin temperature of a substance is directly
  proportional to the average kinetic energy of the
  particles of the substance. 273 _____oC
  _______Kelvin
• There is no temperature lower than 0 Kelvin
  (Absolute Zero).
• Kinetic Energy ½ mv2 where m mass and v
  velocity

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Absolute Zero

• The greater the atomic and molecular motion, the
  greater the temperature is of a substance.
• If all atomic and molecular motion would stop,
  the temperature would be at absolute zero (0
  Kelvin or -273 oC)

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Diffusion and Effusion

• Diffusion describes the movement of one
  material through another
• Particles diffuse from an area of high
  concentration to low concentration
• Effusion gas escapes through a tiny opening.
• The heavier the molecule, the slower it will
  effuse or diffuse

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Diffusion and Effusion
Effusion
Diffusion
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Pressure

• Pressure is the force per unit area
• Gas pressure is the force exerted by a gas per
  unit surface area of an object.
• Gas pressure is the result of billions of
  collisions of billions of gas molecules with an
  object
• Atmospheric pressure (air pressure) results from
  the collisions of air molecules with objects.
• The air pressure at higher altitudes is slightly
  lower than at sea level because the density of
  the Earths atmosphere decreases as elevation
  increases.
• Vacuum - Empty space with no particles and no
  pressure

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Measuring Pressure

• Barometer an instrument used to measure
  atmospheric pressure

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Measuring Pressure

• Manometer an instrument used to measure gas
  pressure in a closed container

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Units of Pressure and STP

• Average atmospheric pressure is 1 atm
• 1atm 760 torr 760 mmHg 101.3 kPa
• STP (Standard Temperature and Pressure)
• 1 atm and 0oC or 1 atm and 273 K

S T P
e r f e c t
e n
1 0
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Daltons Partial Pressure

• Daltons law of partial pressures states that the
  total pressure of a mixture of gases is equal to
  the sum of the pressures of all the gases in the
  mixture.
• Ptotal P1 P2 P3 . . . Pn

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Conversion Factors for Pressure
1 atm 760 torr 760 mmHg 101.3 kPa
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Example 1
Convert 2.5 atm into torr, mmHg, kPa
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Example 2
Convert 215 kPa into torr, mmHg, atm
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Daltons Law of Partial Pressures
Ptotal P1 P2 P3 Pn
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Example 1
Ptotal PO2 PCO2 PN2
0.97 atm PO2 0.70 atm 0.12 atm
PO2 0.15 atm
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Example 2
You first have to put everything in the same
units!
Ptotal PO2 PCO2 PCO
Ptotal 0.563 atm 2.32 atm 0.599 atm
Ptotal 3.48 atm
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COCl2
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C2H2AsCl3
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Cl3CNO2
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C4H8Cl2S