Humboldt H-9340 Ball & Ring Demonstration - Manual (Page 3)

Operation
Begin by heating the ball. After about thirty seconds to one minute of
applying heat (this depends on your heat source) try gently, but quickly
sliding the ball through the ring. What happens? You should find that
the ball would not pass through the ring.
Now, give the ring time to cool and once again try passing the ball
through the ring. As the ball cools you will find that it reduces in size
enough to allow the ball to pass through once again.
Before you perform the next experiment, try predicting what will hap-
pen when the ring is heated. Then perform the experiment as before,
only this time heat the ring. What happened? Why?
Make sure that both the ring and ball are cooled to room temperature
before putting the set away.