As a demonstration or as a hands-on activity, your class watches as the combination of vinegar and baking soda produce carbon dioxide gas. The intent of the instructional activity is to help youngsters understand that gases occupy space. It is included as part of a unit on air, but can stand alone as an introduction to gases while teaching a unit on matter. For the unit, a related literature piece is provided, along with math worksheets, a student magazine, and helpful projections slides.