Molecular Motion Demonstrator

This demonstration tool allows us to model a variety of atomic behavior.   The following are notes (these will save the student having to make them during the demonstration and will allow them to study the modeling better.

            General observations

1)     some molecules move faster than others, with constant random motion

2)     molecules collide with each other and the walls

3)     near elastic collisions

4)     rarity of 3 body collisions

5)     generally there is a large amount of space between the molecules

6)     random motion in straight lines between collisions

7)     pressure exerted on whatever they hit

             Diffusion   -  as the particles move across the barrier they demonstrate diffusion:        (movement of molecules from one area to another with a net change in concentration)

             Temperature

1)     related to average speed of molecules

2)     would 2 different gases at same temperature have same average speeds?

3)     observe different speeds of different gas particles -> temperature relates to average K.E. of molecules

4)     increase vibration rate:  average speed increases, frequency of collisions increases, mean free path decreases

             Similarities with real world

1)     model and real gases involve particles in continual, random motion, with straight line paths between collisions

2)     particles in model occupy only a small fraction of total volume

3)     changes in amount of movement is associated with change in temperature

4)     rebounding forces of particles produce pressure in both model and real gases

             Dissimilarities with real world

1)     model uses particles approximately ten million times the diameter of the particles in real gases

2)     distance between collisions in real gases much greater than the distance traveled by plastic balls in relation to size

3)     the speeds of the balls in the model are at most a few miles per hour while gas molecules travel at speeds of hundreds of miles per hour

4)     real gas molecules collide elastically while our model will run down due to friction is energy is not applied

5)     real gases are three dimensional, model is two dimensional

6)     most gas molecules are not spherical

7)     spaces between particles in model taken up by air, in gases empty spaces occupies the space between molecules

             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 another atom - these gas molecules may come together, slow down, and allow attractive forces to form

             Boyle’s Law

             Charles’ Law