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PURPOSE: To illustrate thermal expansion in a paradoxical way.
DESCRIPTION: At room temperature the ball will not fit through the hole in the metal plate (Click here for video.). When the plate is heated by a burner for about 30 seconds, the ball easily fits through the hole (Click here for video.).
SUGGESTIONS: 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.
See Question of the Week #57 for information on using this demonstration to enhance class involvement.
REFERENCES: Available. (PIRA 4A30.22)
EQUIPMENT: Metal ball and hole on handles, burner with matches.
SETUP TIME: 10 minutes.
