To observe the chemical activity of mixing baking soda with vinegar.
Empty soda bottle
Place two teaspoons of baking soda into the empty soda pop bottle and add an inch of water. Next, place a tablespoon of vinegar into the balloon and cover the top of the bottle with the mouth of the balloon. When the balloon is on correctly, lift the end of the balloon releasing the vinegar into the bottle where the baking soda and water waits. What happens? Does the balloon expand? Does the balloon shrink?
When the vinegar reaches the baking soda, a chemical reaction takes place. During this reaction carbon dioxide is formed. This gas is released from its liquid/solid state which makes the balloon expand. See how large you can make the balloon by adding more baking soda, vinegar, and water.