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    An Active Volcano

    Kids, how would you like to make your own version of an erupting volcano? These directions are for a rather large one, so you can scale it down if that is more convenient. You will need a large quantity of modeling clay, 1 tablespoon of baking soda (sodium bicarbonate), 1 cup of vinegar (acetic acid), and red food coloring. Make a mountain out of the modeling clay in a large pan, tray, tub or tank. The mountain should be about 1 foot in diameter at the bottom, about 3 or 4 inches in diameter at the top, and about 1 foot high. Then make a hole going down from the top into the mountain, about 2 inches in diameter at the top but wider inside the mountain. Be certain it is deep enough and wide enough to hold the whole cup of vinegar.

    Please note:  All chemicals and experiments can entail an element of risk, and no experiments should be performed without proper adult supervision.

    Mix about 5 drops of red food coloring in the vinegar to make the "lava" orange, and pour it into the volcano. Now drop in the 1 tbsp. of baking soda, sit back, and watch it foam and froth. What it happening chemically? The acetic acid (CH3COOH) is mixing with the sodium bicarbonate (NaHCO3 ) to make carbon dioxide gas (CO2 ), water (H2O), and sodium acetate (NaC2H3O2 ). For the older kids, this is a "double replacement" reaction. It's the CO2 that makes the solution foam.

    A variation on the volcano is to actually build it out of dirt, shaping moist dirt around an empty soda bottle and filling the bottle with the vinegar and baking soda. Or you can shape the clay around the bottle. Please read a bit about volcanos now to learn how real ones work. Look in an encyclopedia, ask a scientist, check out a book from your library, or cruise the internet!

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    Kathleen Carrado Gregar, PhD, Argonne National Labs 
    [email protected]
    January 1997

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    References: "Chemistry for Every Kid" by Janice VanCleave (p. 76) and the La Jolla Country Day School web page: www.ljcds.pvt.k12.ca.us/html/cyberchem.