Kinetic Molecular Gas Model

1
Kinetic Molecular Gas Model

• Ch 13

2
Gas Particles

• Gas consists of small particles that have mass.
• Many gas particles are molecules.
• Noble gas particles are single atoms.
• Gas particles are separated by relatively large
  distances (which is why they can be compressed).
• Gas particles are moving rapidly and randomly.

3
Gas particle collisions

• Gas particles collide with each other and
  container walls without slowing down or losing
  energy.
• This means the collisions are elastic.
• Most things you encounter colliding have
  inelastic collisions...like cars.

4
Collisions and pressure

• Gas collisions are what causes pressure.
• The more collisions per area over a period of
  time, the more pressure.
• In a closed system, for a given amount of gas,
  pressure can be increased by
• Increasing temperature (kinetic energy)
• Decreasing volume

5
Volume and Pressure
6
Volume and kinetic energy

• If gas is in a container that can expand (like a
  balloon), increasing kinetic energy will cause
  the collisions with the walls of the container to
  be stronger, pushing them out (expanding the
  volume).
• This is why hot gases expand and cold gases
  contract.
• The molecules are always filling the container,
  but they are hitting the walls with different
  amounts of force depending on kinetic energy.

7
Measuring Pressure

• Gas pressure results from gas molecules colliding
  with other objects.
• Pressure is measured in
• Atmospheres
• Pascals
• mmHg
• Psi
• torr

8
Pressure conversions

• 1 atm 101.3 kPascals (kPa)
• 760 mmHg
• 760 torr
• 14.7 psi

9
Practice conversion

• 1 atm 101.3 kPascals (kPa)
• Convert 120 kPa to atmospheres
• 1.18 atm

120 kPa 1 atm
101.3 kPa