Molecular Motion Demonstrator

1
Molecular Motion Demonstrator
2
General Observations

• Some molecules move faster than others, with
  constant random motion
• Molecules collide with each other and the walls
• Near elastic collisons
• Generally there is a large amount of space
  between the molecules

3
More observations

• The motion is random but molecules move in
  straight lines between collisons
• Pressure is exerted on whatever they hit

4
Diffusion

• Particles demonstrate diffusion movement of
  molecules from one area to another with a net
  change in concentration

5
Temperature

• You can observe different speeds of different
  size particles ? temperature relates to average
  K.E. of molecules
• Increase vibration rate average speed
  increases, frequency of collisions increases,
  mean free path distances decrease

6
Liquids and Solids

• Attractive forces between gas molecules are
  called van der Waal forces (positive charge of
  nucleus is not completely shielded by electron
  cloud so at short distances the nucleus may be
  attracted to electron cloud of anther atom)

7
Boyles Law

• As volume is decreased the pressure increases

8
Charles Law

• As the temperature increases the volume increases.

9
Similarities to real world

• Model and real gases have particles in continual,
  random motion
• Particles in gases move in straight lines between
  collisions where in the demonstrator particles
  can move in curving patterns
• Particles occupy a very small fraction of total
  volume

10
More similarities

• Changes in amount of movement are associated with
  idea of change in temp.
• Rebounding forces of particles produce pressure
  in model and real gases
• Both model and real crystalline solids have
  orderly arrangement of particles

11
Differences between model and real world

• Size model uses particles approximately ten
  million times the diameter of particles in a real
  gas
• Distance between collisions in real gases is much
  greater than distance traveled by plastic balls
  in relation to their size

12
More Differences

• Speed the speeds of the balls in the model are
  at most a few miles per hour while gas molecules
  travel at hundreds of miles/hour
• Friction real gas molecules collide elastically
  while model will run down without energy being
  continually applied

13
More Differences

• Dimensions model is 2-dimensional while gases
  are 3D
• Shape most gas molecules are not spherical like
  the model particles
• Space between particles in model taken up by air,
  while in gases empty space is found between the
  molecules