The Gas Laws

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The Gas Laws

• Section 3.2

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• What happens to your lungs when you take a deep
  breath?

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Pressure

• Pressure The result of a force distributed over
  an area
• A. SI Unit Pascal (Pa)
• 1 Pascal Newton/meter2
• 1. A Newton is a measure of force
• 2. (Meter)2 is a measure of area
• 3. 1000 Pa 1 kPa

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Pressure

• The pressure in a closed container of gas is
  caused by collisions between the particles of a
  gas and the walls of the container
• 1. The speed and frequency of collision have a
  direct affect on pressure
• 2. As speed increases the pressure increases,
  as speed decreases the pressure decreases
• 3. The mass of the particles also affects the
  pressure

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Factors that Affect Gas Pressure

• Temperature
• 1. Raising the temperature of a gas will
  increase the pressure if the volume of the gas
  and number of particles are constant
• 2. As the temperature rises, the average
  kinetic energy of the particles in the air
  increases
• 3. With increased kinetic energy, the
  particles move faster and collide more often
  with the walls of the container

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• B. Volume
• 1. Reducing the volume of a gas increases its
  pressure if the temperature of the gas and the
  number of particles are constant
• 2. As the volume is decreased, particles of
  trapped air collide more often with the walls of
  the container

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• Number of Particles
• 1. Increasing the number of particles will
  increase the pressure of a gas if the temperature
  and the volume are constant
• 2. The more particles there are in the same
  volume, the greater the number of collisions and
  the greater the pressure

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Charless Law

• States that the volume of a gas is directly
  proportional to its temperature in Kelvin if the
  pressure and the number of particles are constant
• Absolute zero the temperature of 0 K or -273C

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• The formula equals
• 1. Temperature must be
• written in Kelvin (add 273 to
  temperature in
• Celsius to get Kelvin)
• D. As a gas cools to temperatures near 0K, the
  gas changes to a solid, liquid, or sometimes a
  Bose-Einstein condensate

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Charless Law
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Boyles Law

1. The volume of a gas is inversely proportional to
   its pressure if the temperature and the number of
   particles are constant.
2. The formula equals P1V1 P2V2

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Boyles Law
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The Combined Gas Law

• Describes the relationship among the temperature,
  volume, and pressure of a gas when the number of
  particles is constant
• The formula equals
• C. Scientists need laws
• to deal with situations in
• which multiple variables
• are changing

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• D. What will happen to the volume of a weather
  balloon as it rises through the atmosphere?
• 1. A decrease in pressure should cause the
  balloon to expand to a larger volume
• 2. A decrease in temperature should cause the
  balloon to contract to a smaller volume
• 3. Whether the balloon expands or contracts
  depends on the size of the changes in pressure
  and temperature

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Plot Boyles Law
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Plot Charless Law