Air expands when heated
To show that air expands when heated, fit an electric light bulb flask or a bottle with a single- whole stopper or cork which has a 30-cm length of glass tubing or a soda straw by it. Place the end of the tube in a small bottle of water. Heat the flask and view what happens. Heat the flask until a considerable amount of air has been separated and then cool the flask by pouring cold water over it or by rubbing with a piece of ice.