Concept
The apparatus provides a good model of a semi-permeable membrane, where after beginning with all the differently sized balls on one side of the holed-barrier, only the smaller sized balls migrate to the other side. This process is known as osmosis.
Procedure
- Place all balls on one side of the divider attachment in the demonstrator’s field and fully extend the adjustable feet to tilt the demonstrator as much as possible.
- Turn on the overhead projector and toggle the power switch on the side of the demonstrator to turn it on.
- Slowly rotate the black knob clockwise to adjust the speed of the agitator bars to full power.
- Wait about 10 seconds for the balls to reach equilibrium.
- Notice that many of the small balls have moved to the other side of the divider while the medium and large balls have not.
Equipment
- Small Magnet
- Box of 10 Small, 10 Medium, 3 Large Balls
- Divider Attachment
- Molecular Motion Demonstrator
- Overhead Projector (not pictured)