Thermal Expansion - Ball And Hole
To illustrate thermal expansion in a paradoxical way.
Metal ball and hole on handles, burner with matches.
Before performing the experiment ask your students: When the plate is heated, will the hole get bigger, smaller, or stay the same size? Many people misinterpret the idea of expansion to believe that the plate will expand inward, making the hole smaller.
At room temperature the ball will not fit through the hole in the metal plate. When the plate is heated by a burner for about 30 seconds, the ball easily fits through the hole.
Lecture Demonstration Apparatus Diagram. Paul Hewitt, Expansion of Nothing.