Budding chemists aren't the only ones who will get a kick out of this enjoyable experiment that teaches something about how the natural world works. When baking soda and vinegar come into contact, they form carbon dioxide. This gas fills the bottle and can't escape, so it rushes into the balloon, causing it to inflate.
260-, 350-, and 646-size balloons: The first digit represents the diameter of the balloon when fully inflated; the second two digits represent the length. Example: 260 is 2 inches in diameter, 60 inches long.
Foam core with Glue Dots -- affix 11 160-size balloons to an 11-by-17-inch piece of foam core with Glue Dots.