It's a super easy experiment using what most kitchens likely have on hand: an empty plastic water bottle, baking soda, and vinegar.
If you're like me, you have some extra balloons leftover from some past party. Although by the end of this little activity, I've now exhausted my supply. The kids wanted to keep making more and more.
To blow up the balloons:
Step 1: Fill a water bottle about a 1/3 of the way with vinegar.
Step 2: Fill your balloon about half way with baking soda.
Note: If you have them, funnels would be useful for steps 1 & 2. We used my daughter's Mad Science beakers instead.
Step 3: Stretch balloon over the top of the bottle being careful not to spill any of the baking soda into the bottle.
Step 4: When you're ready, tip up the balloon so the baking soda falls into the bottle.
Step 5: Watch as your child is delighted by the acetic acid (vinegar) and sodium bicarbonate (baking soda) combine to form carbonic acid and release carbon dioxide into the balloon. More on the science here.
Note: We had a bit of a mess when we were finished. But the beauty of vinegar and baking soda on the counter and floor is that during cleanup, you end up with a sparkling clean result.