Physics at the Breakfast Table: Getting your Fill of Iron

What you Need

• Cereal such as Total® (must be high in iron)
• Strong magnet
• Water
• Blender
• Plastic cup
• Plastic spoon (or other plastic utensil)
• White paper towels or napkins

What to Do

1. Pour equal amounts of cereal and water into the blender (1 cup of each is fine). Blend the mixture until it looks like a smooth, soupy mess.
2. Tape your magnet to the handle end of a plastic spoon so that part of the magnet hangs off the end of the spoon.
3. Pour some of the mixture into a plastic cup and gently stir with the magnet-end of the spoon for about 5 minutes.
4. Take out the magnet and let the excess mixture drip off or rinse it off lightly with water. Then wipe the magnet on a white paper towel - you should see small shavings of iron! If you don't see the iron you may need to blend the mixture more or try a stronger magnet.

What’s Going On?

The top question on your mind is probably, "Why are there iron shavings in my cereal?" Your body needs iron to survive. This is because red blood cells need iron to carry oxygen from the lungs to the rest of the body - and our bodies need oxygen to function! Red blood cells are constantly being replaced, so we need to intake iron often. A deficiency of iron, called anemia, can cause people to be weak, tired, have trouble concentrating, and be more likely to get infections.

Iron can be sprayed onto the flakes or added as a powder to the mixture.

Magnets apply forces on other magnetic objects, like iron nails and the iron shavings in your cereal.

Because some people don't get enough natural iron in their diets (commonly found in red meat and green, leafy vegetables), iron is often added to foods like cereal and infant formula. These foods are usually marked "iron fortified." Small pieces of iron are added to fortified cereal along with the rest of the ingredients, and the iron added to your cereal is the same iron that is used to make nails!

Just as you can use a magnet to pick up a nail, you can use a magnet to pick up the small pieces of iron in your cereal. Iron is usually not a magnet (you can't pick up one nail with another), but it becomes magnetized when you put it close to a magnet. This is why you can pick up a nail with a magnet.

Have you ever brought two magnets close to one another and felt them attract each other? Magnets apply forces - pushes or pulls - to other magnets that can make them move. When you stir the magnet through the mixture, the force from the magnet on the iron shavings is so strong that the iron shavings stick to the magnet!

Try This!

• Put the mixture in a clear, plastic cup. Hold the magnet on the outside of the cup and stir the mixture with a plastic spoon. Can you see a dark spot (made by the iron shavings) forming on the inside of the container behind the magnet? Try dragging the magnet and see if you can get the dark spot to follow. What happens when you take the magnet away from the cup?
• Repeat the experiment with two or more kinds of cereal. Is there a big difference between them? Check the side of the box and compare the percentage of "recommended daily allowance" (RDA) of iron that is in each cereal.
• The RDA of iron is about 14 milligrams. The average 2-inch nail weighs about 2.51 grams (2,510 milligrams). If you got your RDA of iron each day by eating iron fortified cereal, how many nails worth of iron would you eat in one year?

More Information

• Magnet Man: How Magnets Work
• Dietary Supplement Fact Sheet: Iron
• All About Anemia
• Iron in Cereal - Separation (includes videos)