A box of glass balls can be used to to demonstrate many aspects of amorphous and crystalline structures. To create such a demonstration one starts with a small square or rectangular clear plastic container. (Boxes from magnet toys, fishing tackle etc are perfect.) One then obtains a small amount of glass beads of the type used in chemical filters. (The size similar to small ball bearings is good, and also useful in combination with the ball bearings for a percolation demonstration.) The beads are spread in a single layer that covers about half the base of the box. The box is held at a some 20-30 degrees to the horizontal and lowered towards the horizontal. Slow lowering with occasional slight shakeups mimics the annealing process and gives a perfect crystal (see frame (a) of the figure). Rapid lowering corresponds to a quench and an amorphous structure is obtained (see frame(b) of the figure). Defects such as vacancies and grain boundaries can be induced with a little practice (a vacancy is shown in frame(c) of the figure).
These pictures were taken by opening the box and placing it on a xerox machine. Multiple boxes can be passed around the lecture room (closed boxes are recommended) or the demonstration can be made over an overhead projector. If using an overhead or xerox machine, a coin can be placed to hold the box at a degree or two from horizontal. For overhead use clear glass beads are essential.
To the previous page: Lecture 1.