Articles

    Candy Clouds

    Kids, did you know that October 19-25 this year was National Chemistry Week?   The theme this year was "The Earth's Atmosphere and Beyond".   All kinds of fun activities were developed for that week to highlight the chemistry going on in the air that we breathe.   Here we are going to highlight one of them, which was made to help discuss wind.

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

    Wind can carry smoke, dust, and gases hundreds of miles in just a few days.   Satellite images of dust storms in the African Sahara Desert show that some of the dust actually travels all the way across the Atlantic Ocean and falls onto the southeastern U.S.   Because we can't see air, we can't tell where it is going without clues such as seeing a cloud drift by or feeling it on our skin.   This activity uses colored candy dropped into warm water to imitate the way that smoke, dust, and gases move in air.

    Ask an adult partner to help you pour warm (not hot) water into a square plastic dish, one that is about sandwich-size.   Pour the water about 1 inch deep.   Placing the dish on a white tabletop or white piece of paper will help you see the effects best.   Then get somes candies with hard shells in a variety of colors.   Select three pieces each of four different colors.   Put them into the water so that each corner of the dish has a different color.   Keep the water as still as possible (no stirring!).   Now watch carefully as the candies dissolve.   Draw a picture of what you observe.   You can try different types of candy for fun, but use the same kind of candy for each individual experiment.   (This way, if you want to test more advanced concepts, you can compare factors such as dissolving rates and the way that different dye colors mix).

    One of the early ways that scientists tracked how fast winds were blowing was by watching clouds.   In this activity, you made clouds of color in the water.   The clouds moved even though you did not mix the water.   While we know that, in water, diffusion causes the apparent movement, we use this as an analogy for seeing clouds move in the sky.   Just for fun, when you are done, go ahead and stir up the center using a spiral motion.   Watch your candy clouds really move now, almost like the hurricane eyes we see on weather news doppler radar.

    Here is an interesting sidebar to this experiment.   One of the candies we tried this with were Starburst® Jellybeans.   After the color clouds formed, we noticed that the tiny little Starburst® decals from each individual jellybean were floating on top of the water.   They were fragile and dissolved after a couple of minutes.   We speculate that these are made of a soluble, food-grade plastic such as gelatin or a cellulose derivative.   A call to the Mars, Inc. Consumer Affairs Office yielded the following response: "The edible ink changes the crystalline structure of the candy shell and it takes longer to dissolve".

    --------------

    Kathleen Carrado Gregar, PhD, Argonne National Labs 
    kcarrado@anl.gov
    November 2003

    ----------------

    Reference: This and many other NCW activities can be downloaded from the www.chemistry.org website. On the left, where it says "Quick Find", click "Natl Chem Week".   From there go to NCW Resources for Students and Educators and download the first publication.   It's called "Celebrating Chemistry" and it has many hands-on activities and articles for 4th-6th grade students.   Email kcarrado@anl.gov with any info about the Starburst® phenomenon.