Kinetic Molecular Theory

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Kinetic Molecular Theory

• KMT

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KMT

• Newtonian Cradle
• What happens as two balls are pulled back and
  then released?
• Why does this happen?

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KMT

• Where the collisions between the balls elastic?
• Initially Yes, because kinetic energy was
  transferred with each collision
• Why did the balls eventually stop swinging?
• The collisions were not perfectly elastic, some
  kinetic energy was lost as heat during each
  collision.

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KMT - Assumptions

• Gas consists of large number of particles (atoms
  or molecules)
• Small, hard spheres
• Particles make elastic collisions with each other
  and with walls of container
• There exist no external forces (density constant)
• Particles, on average, are separated by distances
  large compared to their diameters
• Insignificant volume relatively far apart from
  each other

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KMT - Assumptions

• No forces between particles except when they
  collide
• No attraction or repulsion between particles
• Particles in a gas move rapidly in constant
  random motion
• Move in straight paths, changing direction only
  when colliding with one another or other objects
• Average speed of O2 in air at 20 oC is an amazing
  1660 km/h! (1.6km1mile)