Use electricity to break water into its elemental components.
Build a simple electrolysis device using a 9-volt battery wrapped in oil-based modeling clay, trap the two gases produced, and end with a bang as you test their composition.
Full instructions for this activity are available at https://www.exploratorium.edu/snacks/having-gas-with-water
Science Snacks are hands-on activities, projects, and experiments that are designed for the classroom and the curious. They're cheap, simple, safe, scientifically accurate, and teacher tested. Want to see more? Check out http://exploratorium.edu/snacks.