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PURPOSE

Test for the presence of iron in breakfast cereal.
 

PERFORMING THE EXPERIMENT

1. Fill a small plastic cup approximately 2/3 full with cereal. 

 
2. Using the end of a wooden roller, carefully crush the cereal in the cup.  Because the results of the experiment are more obvious when the cereal is a fine powder, take time to crush the cereal as thoroughly as you can.  Your adult partner may need to help with powdering the cereal.

 
3. Add water to the cup, so that the cup is approximately 2/3 full of the cereal/water slurry.

 
4. Check to see that your white magnet is functioning properly by bringing it close to an iron nail and determining that the magnet can pull the iron nail along the table.

 
5. Holding the open end of the Tygon® tubing, slowly swirl the cereal-water slurry with the magnet for approximately 2 minutes.  (Add more water if the slurry gets too thick.)

 
6. Remove the stirrer from the cup.  Using the cup of water provided, gently rinse the cereal off the magnet.  What remains on the tip of the magnet?  (See "Explanation" below.)

 
7. When you finish the experiment, clean the magnet with a paper towel, pour the cereal/water slurry into the container provided, and throw the cup in the trash. 

 

1. Did you expect to obtain iron metal from breakfast cereal?  Why, or why not?

2. Are the cereal makers just kidding us by putting iron metal in our cereal?  Given that iron metal will not dissolve in water, how is it going to be absorbed in our body?  Wonít it just be excreted like most other small iron objects would if we swallowed one?  Why, or why not?  Hint:  Iron metal, at least in finely divided form, dissolves in medium strength acid solutions over a period of several days.  Is that of any help?
 

EXPLANATION

Data on the side of a box of one brand of cereal indicates that one ounce (3/4 cup) provides 100% of the United States recommended daily allowance (U.S. RDA) of iron for each person.  Apparently because ionic iron (e.g., FeSO4 used in iron pills) speeds up spoilage reactions, the iron in the cereal needs to be in the form of iron metal.  The tiny dark colored filings that you saw on the end of the white magnet were actually iron metal, which is attracted to a magnet just as an iron nail is attracted to a magnet.  Unfortunately, because of the short residence time in the stomach, little of this iron metal is dissolved in acids in the stomach, and most of it is probably excreted.
 

EQUIPMENT NEEDED

Cereal (NOTE:  cereals that contain 100% of the RDA of Iron in the form of "iron" or "reduced iron" provide the greatest quantity of iron filings, e.g., TOTAL cereal) ; 3-oz. plastic cups; 3/4" wooden dowels, 12-15 cm long; 2-liter soda bottle filled with water; iron nails;  white magnetic stirring bar held in 5" length of Tygon® tubing, or other type of white magnet ; 250-mL plastic beakers or cups;  1/2-gal. container for used cereal/water slurry; paper towels.
 

REFERENCES

Modified from Robert Becker, An Incredible Evening of Chemistry: 20 Demonstrations Guaranteed to Knock Your Socks Off, Flinn Scientific, Inc., 1993, pages 13-14 and Mickey Sarquis and Jerry Sarquis, Fun with Chemistry: A Guidebook of K-12 Activities, Volume 1, Institute for Chemical Education, University of Wisconsin - Madison, 1991, pages 49-52
 

Kids Involved Doing Science is at http://www.kids.union.edu.

Modified 10/01/02  by C. & P. Scaife