The brass experimnt

In this experiment we were using a ball and ring that are made out of brass. The ring fitted through the ball.

We heated the ball first over a flame and tried to put it through the ring. The ball had expanded so it did not fit through the ring. We then cooled the ball in cold water.

Then we heated the ring - it expanded, so then the ball fitted through. We cooled the ring in cold water. 

Then we heated the cold ball and the cold ring together. They expanded equally so the result was that the ball still fitted through the ring.