Chapter 13: States of Matter

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Chapter 13 States of Matter

• Kinetic-Molecular Theory Explains the motions
  and behavior of a gas. The theory has three
  components
• 1. Particle Size Gas particles are small
  relative to the space around the particles. This
  means that there is no significant attraction or
  repulsion between gas particles. NO transfer of
  energy or elastic.

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Kinetic Theory

• 2. Particle Motion Gas particles are in constant
  and random motion.
• a. Mean Straight Path Gas particles move in a
  straight path until a collision.
• b. Elastic collisions collision between gas
  particles does NOT transfer energy. The total
  amount of kinetic energy of the two particles
  does not change.

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Kinetic Theory

• 3. Particle Energy defined by the mass and
  velocity of the gas particle.
• a. Equation KE ½ mv2
• KE Kinetic energy
• m mass
• v velocity (both speed and direction)
• For a sample of the same gas, the masses will be
  the same but the velocity will differ.
• NOT all gas particles will have the same kinetic
  energy.

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Kinetics Theory

• b. Temperature the average kinetic energy of a
  given sample of matter. OR ALL GASES HAVE THE
  SAME AVERAGE KINETIC ENERGY AT THE SAME
  TEMPERATURE.

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Behavior of Gases

• Using the kinetic-molecular theory
• 1. Low Density D m/v, a large volume like
  in a gas yields a small density for equal mass.
  Compare a solid with a gas, the solid has more
  particles in a given volume and therefore a
  greater density.

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Behavior of Gases

• 2. Compression and Expansion. Gases fill the
  volume of the container, therefore the volume of
  the container defines the density of the gas.
  Distance between particles are large, therefore
  gases are very compressible.

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Behavior of Gases

• 3. Diffusion The flow of a gas into a space
  (already containing a gas).
• Rate of diffusion depends on the mass of the
  gas. Lighter particles diffuse at a faster rate.
• At the same temperature, heavy and lighter gases
  must have the same average kinetic energy
  therefore lighter gases MUST be moving at a
  greater velocity.

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Behavior of Gases

• 4. Effusion the escape of gas through a tiny
  opening.
• 5. Diffusion rate at which a molecules spreads
  out
• Grahams Law of Effusion the rate of effusion
  for a gas is inversely proportional to the square
  root of the molar mass.
• Equation

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Example of Grahams Law

• The molar mass of helium is 4.0 g/mol. The molar
  mass of air is 29 g/mol. What is the ratio of
  diffusion rate? Which gas diffuses faster?

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Samplers

• 1. Calculate the ratio of diffusion rates for
  neon and helium. Which gas diffuses faster? How
  much faster?
• 2. Calculate the ratio of diffusion for ammonia
  (NH3) and carbon dioxide (CO2). Which gas
  diffuses faster?
• 3. What is the ratio of diffusion rates for argon
  and radon? Which gas diffuses faster?

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Gas Pressure

• Pressure the force exerted per unit area.
• 1. atmospheric pressure 1Kg/ cm2
• pressure decreases with an increase in
  altitude.
• 2. measured with a barometer (measures
  atmospheric pressure) or a manometer (measures
  gas pressure in a closed container).

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Gas Pressure

• 3. SI unit is pascal 1 N/m2
• 4. conversions
• 760 mm Hg 760 torrs 101.3 kPa 1 atm at
  sea level.

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Daltons Law of Partial Pressure

• The total pressure exerted by gases within a
  container is the sum of pressure of all the gases
  in the container.
• Ptotal P1 P2 P3 .

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Example of Daltons Law

• Air is made up of N2, O2, Ar, and CO2. Air
  pressure at sea level is 760 mm Hg. What is the
  pressure exerted by oxygen at sea level if N2 594
  mm Hg, Ar 7.10 mm Hg and CO2 0.27 mm Hg?

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Samplers

• 1. What is the partial pressure of oxygen gas in
  a mixture of nitrogen gas and oxygen gas if the
  total pressure is 0.48 atm and the particle
  pressure of nitrogen is 0.24 atm?
• 2. Find the total pressure of a mixture of gases
  with the following particle pressures 6.6 kPa,
  24 mm Hg and 1.2 kPa?
• 3. What is the total pressure of a mixture of
  gases with the following particle pressures 58.6
  torrs, 13.2 kPa, 2.43 kPa, 12.5 kPa, and 2500 Pa?

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NOTE

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Phase Changes

• Solid, liquid and gas are the states or phases of
  matter.
• 1. The phase depends on the temperature
  (kinetic energy) and/or the pressure.
• 2. Note figure 12-29, page 429.
• 3. Energy required to bring about phase change.

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Energy Relationship in Phase Change

• freezing point temperature at which matter
  changes to a solid phase. Energy out.
• a. normal freezing point at STP (standard
  temperature and pressure, 1 atm _at_0oC).
• 2. melting point temperature at which matter
  changes to a liquid.
• Energy in.

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Energy Related to Phase Change

1. vapor pressure pressure at the surface of a
   liquid caused by the vaporization of the liquid.
   Energy in.
2. sublimation solid changes to a gas with no
   liquid phase. Dry ice. Energy in.
3. deposition gas changes to a solid with no liquid
   phase. Energy out.
4. vaporization liquid changes to a gas or vapor
   usually with the in-put of energy. Boiling water.
   Energy in

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Energy Related to Phase Change

• evaporation liquid changes to a gas only at the
  surface where the energy is high among to allow
  for the molecules to escape. The Sun heating and
  evaporating the surface of a lake. Energy in.

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Phase Diagrams

• Chart that shows the relationship between
  pressure and temperature as it pertains to
  changes in phase.
• Be able to read and interrupt. Page 429.
• Note triple point a temperature/pressure
  relationship in which matter exist in three
  phases.