How Sweet It Is!

    Kids, did you ever notice at your summer family picnics that all the cans of diet soda float on top in a cooler of ice water, while regular sodas have to be fished from the bottom of the freezing cold water? It is obvious that the densities of the two are quite different. Density is a property used by chemists to help identify substances. It is the amount of mass in a particular volume of a substance.

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

    Place one unopened can of diet cola and one unopened can of regular cola (do not use bottles) in a large container of water, such as a 5 gallon aquarium or a regular pail. Make sure no air is trapped under the cans. Using the glass container makes a nice visual demonstration for a large group such as your classroom. Both cans occupy the same volume (they are the same size), but they weigh different amounts because of the extra 18 grams or so (about 2/3 ounce) of sugar in the regular soda.

    Fill a clear plastic cup 2/3 full of water and place a straw on an angle all the way in. Use an eyedropper to carefully drip some regular cola through the straw and into the bottom of the water cup. Do not stir the liquids, and notice where the cola stays. Now repeat the procedure using the diet cola, a new cup and straw, and a rinsed eyedropper. Does this one behave differently from the regular soda, and do you think it has anything to do with what the cans of soda did earlier? Now let's drink to density with what soda is left in the cans!


    Kathleen Carrado Gregar, PhD, Argonne National Labs 
    [email protected]
    April 1994


    References: J. Chem. Ed. 1986, 63, 515 and WonderScience 1993, 7(6).