Hands-on Activity: Cereal Magnets

Contributed by: Engineering K-PhD Program, Pratt School of Engineering, Duke University

A photograph shows a woman at a table taking a bite of cereal from a bowl.
How much iron does fortified cereal contain?
Copyright © 2004 Microsoft Corporation, One Microsoft Way, Redmond, WA 98052-6399 USA. All rights reserved. http://office.microsoft.com/en-us/images/results.aspx?qu=cereal&ex=1#ai:MP900448567|mt:2|


Student groups compete to design a process that removes the most iron from fortified cereal. Students experiment with different materials using what they know about iron, magnets and forces to design the best process for removing iron from the cereal samples.

Engineering Connection

Students act as "reverse" food engineers by designing processes to remove the iron from fortified cereal. It is the job of chemical food engineers to add certain vitamins and minerals to processed food as part of the industrial food manufacturing process.

Pre-Req Knowledge

Conduct this activity after students have learned about the primary molecules in found food, such as fats, sugars, starches, proteins, etc. It is also helpful if students have a familiarity with magnets (that is, what they are attracted to) since this activity is not an introduction to magnets. However, enough knowledge about magnets can be acquired by students simply playing with magnets at home or by presenting the Two Sides of One Force lesson for an introduction to magnets.

Learning Objectives

After this activity, students should be able to:

  • Explain that minerals are an important part of the human diet.
  • Explain that different minerals have different roles in human health and state some of them.
  • Describe why iron is an important part of the human diet.
  • List several foods that contain iron.
  • Describe why food engineers add iron and other minerals to cereal.
  • State that the iron in our cereal is the same iron that is attracted to magnets.

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  • Define a simple design problem that can be solved by applying scientific ideas about magnets. (Grade 3) Details... View more aligned curriculum... Do you agree with this alignment?
  • Develop a model to describe that matter is made of particles too small to be seen. (Grade 5) Details... View more aligned curriculum... Do you agree with this alignment?
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  • Measure and estimate liquid volumes and masses of objects using standard units of grams (g), kilograms (kg), and liters (l). Add, subtract, multiply, or divide to solve one-step word problems involving masses or volumes that are given in the same units, e.g., by using drawings (such as a beaker with a measurement scale) to represent the problem. (Grade 3) Details... View more aligned curriculum... Do you agree with this alignment?
  • Draw a scaled picture graph and a scaled bar graph to represent a data set with several categories. Solve one- and two-step "how many more" and "how many less" problems using information presented in scaled bar graphs. (Grade 3) Details... View more aligned curriculum... Do you agree with this alignment?
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  • Design is a creative planning process that leads to useful products and systems. (Grades 6 - 8) Details... View more aligned curriculum... Do you agree with this alignment?
  • Explain how magnets interact with all things made of iron and with other magnets to produce motion without touching them. (Grade 4) Details... View more aligned curriculum... Do you agree with this alignment?
  • Explain how various forces affect the motion of an object. (Grade 4) Details... View more aligned curriculum... Do you agree with this alignment?
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Materials List

Each group needs:

  • 480 ml (1 cup) cereal with a high iron content, such as TotalĀ® or any cereal that contains 100% of the recommended daily allowance of iron

To share with the entire class:

  • magnets of varying strengths, such as magnets generally used in classrooms; refrigerator magnets have less strength and may not work, but provide students with an alternative with which to experiment
  • ZiplocĀ® bags
  • cups of water
  • blender
  • electronic balance that is sensitive enough to be able to detect small changes in weight (at least one tenth of a gram); if not available, see the Procedure section for alternative ways to quantify the amount of cereal removed


As we have just learned, iron is one of the many minerals that is essential to the human diet. Because of iron's importance, chemical food engineers often fortify foods with iron, meaning they add extra iron. One of the foods most commonly fortified with iron is dry breakfast cereal.

In this activity, we will remove the iron that has been added to cereal. In this way, we will be acting as reverse food engineers.


calcium: A mineral that is helpful in building strong bodies, especially bones and teeth.

fortify: To add one or more ingredients to a food to increase its nutritional content.

iron: A mineral that is necessary to transport oxygen around the body (part of hemoglobin).

magnet: An object or device that produces a magnetic field that attracts other magnets and certain metals.

mineral: Natural compounds that are important in helping the body perform many vital functions.

potassium: A mineral that helps to keep muscles and nervous system working well.

zinc: A mineral that helps the human immune system.



Minerals help your body grow and stay healthy. The body uses minerals to perform several functions. For example, they help build strong bones and teeth, transmit nerve impulses, make hormones and maintain normal heartbeats.

One important mineral is iron. Your entire body needs oxygen to stay healthy and alive. This is because the body needs iron to transport oxygen from your lungs to the rest of your body. Iron helps this process because it is important in the formation of hemoglobin. Hemoglobin is the part of your red blood cells that carries oxygen throughout the body. Several natural foods are iron rich including meat (especially red meat), tuna, salmon, eggs, beans, potato skins and leafy green vegetables.

People who do not get enough iron in their diets tend to become anemic. Anemia is a condition in which not enough red blood cells are present in the blood. The low number of red blood cells results in a lack of hemoglobin, which carries oxygen. If the blood cannot carry enough oxygen to the rest of the body, problems occur. The main symptom of anemia is fatigue. Also, chest pains and shortness of breath can occur. Moreover, people with anemia tend to have pale, pallid skin. Other effects of not getting enough iron include a decreased immunity to disease and sickness. Also, children who lack enough iron in their diets do not develop normally.

While several foods are rich in iron, many people have trouble getting enough in their diets. Thus, chemical food engineers sometimes add iron to processed foods such as cereal. The process used to fortify the cereal is quite simple. The engineers mix powdered iron with the other cereal ingredients. Several types of powdered iron can be used, but the most common types are ferrous sulfate and ferrous fumerate. When ingested, it is converted into iron that can be used by the body in the stomach. The iron mixes with the hydrochloric acid in the stomach to make iron chloride and oxygen gas. The iron chloride is absorbed by the small intestines. The amount of iron added to food is dependent on several factors. For example, the prevalence of iron deficiency in the group of the people who eat the food and the dietary trends of their culture contributes to how much iron is decided to be added to the cereal. Food engineers also add other types of minerals and vitamins to different foods. For example, processed beverages such as orange juice are often fortified with calcium.

Because not everyone eats cereal, food engineers think of ways to deliver essential nutrients to people and kids in some of the world's poorest places. For example, some researchers have developed rice and salts that are fortified with different vitamins and minerals, including iron. This enables children all over the world to receive more nutrients in their diets because rice and salt are consumed in many different cultures.

In this activity, we show that the iron found in processed food is the same type of iron that is attracted to magnets. Students discover this by engineering a process to remove the iron in cereal.

Before the Activity

  • Gather materials.
  • Divide the materials so that each group of two or three students has a set.

With the Students

  1. Ask students if they have ever read the nutrition labels on their foods. Also, ask them if they ever noticed things such as iron or calcium on the labels.
  2. Define what a mineral is and discuss some of the important minerals. Have students write down the functions of the minerals defined above and brainstorm as a class what might happen if people do not get enough of the minerals.
  3. Tell students that iron is often added to cereal products. Tell the students that they are going to design a process to remove the iron from cereal. Inform them that food engineers often do the opposite.
  4. Divide the class into groups of two or three students each. Vary the groups size depending on class size and material availability.
  5. Pass out cups of cereal to each group and let them examine it. Have them notice that they cannot see the iron at this point.
  6. Give the groups 5-10 minutes to discuss their plan to extract the iron from the cereal. Walk around to see if their plans make sense. Do not tell them that their plans are wrong or will not work (yet).
  7. Have groups gather the materials that they chose.
  8. Give students about 15-20 minutes to try to extract the iron from their cereal samples. During this time, walk around the room and talk to the groups about what they are doing. Make suggestions for changes if their processes are not working.
  • First, give small hints such as, "think about what you could do with the water."
  • Second, explain what the different materials will do and how it may help them. For example, tell them that the water helps separate the iron from the cereal and allows it to move.
  • If none of these work, begin giving more direct guidance.
  1. Ask students to weigh how much iron they can remove from their cereal. In order to be able to weigh the iron, first weigh a clean tissue. Then, wipe the iron off of the magnet. Keep the tissue as dry as possible. If the tissue does get wet, allow it to dry and then weigh it again. The weight of the tissue with the iron minus the weight of the clean tissue is the weight of the iron. Note: If a sensitive scale is not available, have students count how many specks of iron they can remove from the cereal. This process is not as accurate, however, it gives students an idea of how much iron is removed from the cereal, which is most important.
  2. If time allows, give students more time to revise their processes and trade in their previous materials for new materials.

Troubleshooting Tips

If students have trouble figuring out how to remove iron from their cereal samples, give them more direction. For example, suggest that the iron may be removed more easily if it is crushed.

One procedure that works well is the following. Begin, by crushing the cereal into small pieces (the smaller the better). Then, put the cereal into a cup of water and stir. Use enough water for the cereal to move freely. Next, place a strong magnet on the outside of the cup and drag it towards the top. Expect to see tiny black specks come up with the magnet, which is the iron that you were looking for.

Alternatively, instead of crushing the cereal and then putting it in water, blend both together. The blender approach works better, however, crushing and stirring into water works as long as the cereal has a high iron content.

If you are not able to get any iron out of the cereal try the following tips. First, try a stronger magnet. The stronger the magnet, the better it will be at removing the iron from the cereal. You can also try crushing the cereal into finer pieces. Also, make sure that the cereal has enough iron in it; use about 100% of the daily recommended serving per cup (note that serving sizes vary).

Investigating Questions

  • What procedures worked best when you tried to remove the iron from the cereal?
  • Why do you think the blender helped get iron out of the cereal?
  • How do you think the extra iron was added to cereals?
  • Why do you think certain cereals are fortified with extra iron?


Pre-Activity Assessment

What Does Iron Make You Think Of? Ask students to brainstorm what iron makes them think of. See if they can make the connection between magnets and iron in food.

Changed Foods: Ask students to brainstorm some foods that they have eaten or seen in stores that have extra nutrition added or other components removed, such as fat or gluten).

Activity Embedded Assessment

Iron Removal Plan: After the activity is introduced, ask students to write quick plans to get the iron out of the cereal samples. Ask them to explain why they chose their methods. Examine and approve their plans before they begin work.

Post-Activity Assessment

Guide to Iron Removal: Ask students to write or draw the steps of the process they used to remove the iron from the cereal. Tell students to imagine they are food engineers making a laboratory manual for other researchers to follow.

Removing Other Minerals: Ask students to think about other foods from which they could remove iron or other minerals. Ask them to make another plan for this process.

Activity Extensions

Have students test the iron content of a variety of different cereals. To do this, they repeat the activity procedure with different samples. After students have measured the iron content in the different cereals, they can create a bar graph of the amount of iron in each cereal.

Discuss how engineers add specific components to food such as other minerals and vitamins. Assign students to make a search at the grocery store, looking at the packages of processed food, and report their findings back to the class.

Activity Scaling

  • For lower grades, give students more direction on the iron removal. For example, give them the specific materials that they need to use, that is, a magnet, water, cup, plastic bag for crushing.
  • For upper grades, give students less direction or permit them to choose different foods from which to remove iron. For example, simply ask students to remove the iron from a food. Then, give them time on their own to think about what would work and request certain materials (or bring them in).


Dietary Supplement Fact Sheet: Iron. Updated July 26, 2005. Office of Dietary Supplements. National Institute of Health. Accessed April 26, 2007. http://ods.od.nih.gov/factsheets/Iron-HealthProfessional/
Minerals. Reviewed August 2004. Kids Health. Nemours Foundation. Accessed April 26, 2007. http://www.kidshealth.org/kid/stay_healthy/food/minerals.html
Matsui MD, William. MedlinePlus Medical Encyclopedia: Anemia. 2005. A.D.A.M., Inc. Accessed April 26, 2007. http://www.nlm.nih.gov/medlineplus/ency/article/000560.htm
Guidelines for Iron Fortification of Cereal Food Staples. May 2001. Sustain: Sharing U.S. Technology to Aid in the Improvement of Nutrition. Accessed April 26, 2007. http://www.sustaintech.org/technology/iron.htm


Liz Harper


© 2013 by Regents of the University of Colorado; original © 2007 Duke University

Supporting Program

Engineering K-PhD Program, Pratt School of Engineering, Duke University


This content was developed by the MUSIC (Math Understanding through Science Integrated with Curriculum) Program in the Pratt School of Engineering at Duke University under National Science Foundation GK-12 grant no. DGE 0338262. However, these contents do not necessarily represent the policies of the NSF, and you should not assume endorsement by the federal government.