Kids, you probably already know that iron is magnetic. In this column, we will demonstrate a way to prove that there is iron metal in two places that you have probably not ever realized: a one dollar bill and a bowl of cereal! You will need a bar magnet (chemists can use long thin stir bars), a dollar bill (or $5, $10, $20 - they all work), and a box of cereal that claims to be high in "reduced" iron (like Total®).
Please note: All chemicals and experiments can entail an element of risk, and no experiments should be performed without proper adult supervision.
First we will do the money experiment. Hold your bill straight down by the very edge of a short end - a newer bill works best because it will hang straight. With the other hand, slowly move the bar magnet lengthwise along the back of the dollar bill as close as possible without actually touching it. What happens? There should be at least one portion of the bill where it actually moves toward the magnet, or is "attracted". Why is this? Some, but not all, of the ink used in printing paper money is deliberately magnetic. This method is used to try to foil possible counterfeiters, and it also helps aid in the detection of counterfeit money!
In the second experiment, soak a few cups of the cereal in a large bowl of water until it is mushy. Vigorously stir the mixture with a wooden spoon for five minutes. Then add your bar magnet and continue stirring, more slowly, for several minutes. Carefully nudge the magnet around the bottom of the bowl a few times, then let the mixture stand for about ten minutes. Slowly pour off the "mush" and examine your bar magnet. Is it covered with small black needles and specks? This is the "reduced" iron (iron metal) that is actually added to the cereal because it is healthy for us to have iron in our diets. Chemists will find this easy to do using a magnetic stir plate, and a large beaker and stir bar. The more cereal you start with and the more time you give, the more iron you will collect!
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Kathleen Carrado Gregar, PhD, Argonne National Labs
[email protected]
March 1993
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Reference: From a "Weird Science" demonstration given by Lee Marek and Bob Lewis at Nalco on 12/4/90.
