This equipment consists of a handle with a hoop and a handle with a ball. At room temperature, the ball should easily fit through the hoop. If the ball is then held in a Bunsen flame for a minute or two, it cannot pass through the hoop.
Through heating, the metal expands in the same way railway tracks can become longer and buckle during hot summer weather. If the ring is heated to the same temperature it too will expand until the ball will go through once again.
In solids thermal expansion varies in line with the material’s 'coefficient of thermal expansion.' Polymers expand much more than metals, ceramics much less. Each metal expands to differing degrees.
The bar and gauge equipment shares the same principle (see Fig 3). Other thermal expansion equipment includes the bar breaking equipment and bi-metallic strips
This equipment is popular because it clearly shows the effects of thermal expansion very quickly. The ball and hoop sets are fairly inexpensive and are available through most lab suppliers.