We have been doing all sorts of fun stuff with balloons lately. I got out the Alka Seltzer and balloons and wanted to find out what would happen if we combined the two. I broke the tablets into pieces to help them fit into the balloons. We pushed the tablets in the balloons and then put in a little water from the hose. I quickly tied up the balloon and watched what happened. The balloon slowly filled up with CO2 and was fizzing like crazy. It was so great...the kids really liked hearing and feeling the bubbling action inside it! We did this over and over again.