Kinetic-Molecular Theory

1
Kinetic-Molecular Theory

• Chapter 14

2
Models

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

3
Kinetic-Molecular Theory (KMT)

• 1) Gases consist of spherical molecules moving
  in constant, random, straight-line motion
• Random, straight-line?
• - move in straight lines until hit
  something, then can bounce off at any angle

4
Kinetic-Molecular Theory

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

5
Kinetic-Molecular Theory

• 3) Gas molecules separated by great distances
  that volume of molecule is negligible
• distance between molecules is more important than
  actual size of molecule

6
Kinetic-Molecular Theory

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

7
Real vs. ideal gas

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

8
Review of KMT

• What features of the Kinetic-Molecular model are
  close to real gases?
• What features of the Kinetic-Molecular model
  break down?