Growing Balloons/ expanding air

Some time ago Drs Noot, Justice and Hudson showed that air expands when heated. We never posted pics. of this but here it is! The fact that air expands and rises when it is heated may be important for explaining some of our work on building energy efficient houses.

A balloon was placed over the opening of a 2L pop bottle. There was just air in the pop bottle. The pop bottle was then placed in a beaker of water. The hot plate was turned on and the water was heated until it boiled. As the water heated the balloon expanded.