The classic demonstration of volume thermal expansion - great for drawing and keeping the attention of your student(s).

• Put the ball through the ring;
• Heat the ball until it is very hot;
• Try to bring the ball back through the ring. The ball cannot pass back through the ring until it has cooled!

Once you have their attention, try some other variations:

• Heat the ring instead of the ball. Does the ball go through the ring now?
• Heat the ring and the ball. Can it go through now?

Historically, the ball and ring experimental apparatus has been referred to as 'sGravesande Apparatus. Willem Jakob van 'sGravesande (1688-1742) wrote one of the first Newtonian physics textbooks in 1720-1721.

The original 'sGravesande ring is currently at the Universidade de Coimbra museum in Portugal. Look at a photograph of the 'sGravesande ring.

Materials: brass ring and ball, wooden handles.

Dimensions: 10-11" (25.4-28.0 cm) long, 1" (2.5 cm) ball diameter.