The genie in the bottle

The catalytic decomposition of hydrogen peroxide provides teachers with a whole range of exciting demonstrations. While ‘elephant’s toothpaste’ may be the most popular, there are plenty of alternatives you can use to keep things fresh. For example, the changing colour of the cobalt chloride ‘traffic light’ demonstration highlights the temporary shift in oxidation state of a transition metal catalyst.

An often-overlooked demonstration with a sense of magic and wonder is the ‘genie in the bottle’, in which a puff of ‘smoke’ escapes from a bottle when the lid is removed.