Kinetic-Molecular Theory (KMT)

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Kinetic-Molecular Theory(KMT)
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Models

• Scientists use models because they are simpler
  than real life
• KMT (Kinetic-molecular theory) can be extended to
  all phases of matter

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Kinetic-Molecular Theory

• Gases consist of spherical molecules moving in
  constant, random, straight-line motion

Random, straight-line?
- move in straight lines until hit something,
then they can bounce off at any angle
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Kinetic-Molecular Theory

• 2) Gas particles undergo elastic collisions
  with each other and with walls of their
  container

• Elastic means total KE is conserved
• KE does not get converted to heat or sound or any
  other kind of energy
• KE can be transferred between particles

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Kinetic-Molecular Theory

• 3) Gas molecules are separated by such great
  distances that volume of molecule itself is
  negligible

• distance between molecules more important
• than actual molecule

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Kinetic-Molecular Theory

• 4) Gas molecules do not attract or repel each
  other
• Assume no interactions between gas molecules

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Real vs. ideal gas

• Ideal gas obeys all assumptions of KMT all the
  time
• Its a model
• It doesnt exist
• Real gases follow KMT most of the time,
• but not at
• high pressure low temperature
• KMT breaks down when molecules are close together

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Review of KMT

• What features of KMT model are close to real
  gases?
• What features of the KMT model break down?