We have been playing with a base, baking soda (sodium bicarbonate), and an acid, vinegar. We started out with these supplies.
We poured half a cup of vinegar and a quarter of a cup of warm water into the plastic bags.
Next we cut small squares of paper napkin, put 2 tablespoons of baking soda in the middle, and tied them up with a twist tie to make a little bundle.
We then dropped the little bundle of baking soda into the water/vinegar mixture. Twist the top and HOLD ON! Enjoy the show!
What we learned?
The bag swells because the acid and the base react with each other to form bubbles of carbon dioxide gas. The gas fills the bag. This is what happens when we make a cake. The baking soda reacts with the chemicals in the batter to form gas bubbles and the cake rises.
This was a really great experiment with Elijah, my little baker. ;)