Hands-on Activity Design a Process to Remove Iron:
Cereal Magnets

Quick Look

Grade Level: 4 (3-5)

Time Required: 45 minutes

Expendable Cost/Group: US $2.00

Group Size: 3

Activity Dependency:

Subject Areas: Biology, Science and Technology

NGSS Performance Expectations:

NGSS Three Dimensional Triangle

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.
This engineering curriculum aligns to Next Generation Science Standards (NGSS).

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.

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.
  • Explain how magnetic fields work. 
  • State that the iron in our cereal is the same iron that is attracted to magnets.
  • Describe the engineering design process. 

Educational Standards

Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards.

All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN), a project of D2L (www.achievementstandards.org).

In the ASN, standards are hierarchically structured: first by source; e.g., by state; within source by type; e.g., science or mathematics; within type by subtype, then by grade, etc.

NGSS Performance Expectation

3-PS2-4. Define a simple design problem that can be solved by applying scientific ideas about magnets. (Grade 3)

Do you agree with this alignment?

Click to view other curriculum aligned to this Performance Expectation
This activity focuses on the following Three Dimensional Learning aspects of NGSS:
Science & Engineering Practices Disciplinary Core Ideas Crosscutting Concepts
Define a simple problem that can be solved through the development of a new or improved object or tool.

Alignment agreement:

Electric, and magnetic forces between a pair of objects do not require that the objects be in contact. The sizes of the forces in each situation depend on the properties of the objects and their distances apart and, for forces between two magnets, on their orientation relative to each other.

Alignment agreement:

Scientific discoveries about the natural world can often lead to new and improved technologies, which are developed through the engineering design process.

Alignment agreement:

  • 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) More Details

    View aligned curriculum

    Do you agree with this alignment?

  • Fluently add and subtract multi-digit whole numbers using the standard algorithm. (Grade 4) More Details

    View aligned curriculum

    Do you agree with this alignment?

  • Students will develop an understanding of the attributes of design. (Grades K - 12) More Details

    View aligned curriculum

    Do you agree with this alignment?

  • The process of experimentation, which is common in science, can also be used to solve technological problems. (Grades 3 - 5) More Details

    View aligned curriculum

    Do you agree with this alignment?

  • Compare how things found in nature differ from things that are human-made, noting differences and similarities in how they are produced and used. (Grades 3 - 5) More Details

    View aligned curriculum

    Do you agree with this alignment?

  • Describe the properties of different materials. (Grades 3 - 5) More Details

    View aligned curriculum

    Do you agree with this alignment?

  • 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) More Details

    View aligned curriculum

    Do you agree with this alignment?

  • Fluently add and subtract multi-digit whole numbers using the standard algorithm. (Grade 4) More Details

    View 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) More Details

    View aligned curriculum

    Do you agree with this alignment?

Suggest an alignment not listed above

Materials List

Each group needs:

  • 480 ml (1 cup) cereal with a high iron content, such as Total® 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
  • Ziploc® 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

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.


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.

Ask students, “How do you think engineers design ways to measure how much iron goes into food?”

Ask a few students to share their ideas, and then briefly introduce the engineering design process.

Explain that engineers ask critical questions about what they want to create or what specific problem they are trying to solve. These questions include: What are the project requirements (criteria)? What are the limitations (constraints)? This also requires conducting research on the problem. For example, chemical engineers work together with scientists and dietitians, as well as engineers from different backgrounds, to better understand the problem of how measure the correct amount of iron to fortify different foods.

The engineering team then imagines possible solutions to the problem. This takes a lot of creative brainstorming! After making a list of solutions and some sketches of their ideas, the team of engineers plan and select their best idea.

Once the team decides on the details of the final design, they create the prototype and test it out! Prototypes are smaller models that are used by engineers to test a design. In the testing phase, the team pays attention to what needs to be changed to the model to make the product work better. The last step of the engineering design process is to improve (iterate) their design.

In this activity, we will use some of the steps of the engineering design process to remove the iron that has been added to cereal. In this way, we will be acting as reverse food engineers.



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 fumarate. 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. Make sure they are using several different strength magnets to test. 
  • 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. Ask students how the different strength magnets worked at separating the iron from the cereal. 
  3. If time allows, give students more time to revise their processes and trade in their previous materials for new materials.


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.


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.

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?

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).

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).


Get the inside scoop on all things TeachEngineering such as new site features, curriculum updates, video releases, and more by signing up for our newsletter!
PS: We do not share personal information or emails with anyone.

More Curriculum Like This

Upper Elementary Lesson
The Minerals We Eat: Iron-Fortified Breakfast

Students learn how minerals are an important part of our diets and that different minerals have different functions in the body. They discover that iron is necessary to carry oxygen throughout our bodies. The lesson prepares students to conduct the associated activity during which they design a proc...

High School Lesson
The Heart of Our Cardiovascular System

Students learn about the heart and its role at the center of the human cardiovascular system. In the associated activity, students play out a scenario in which they are biomedical engineers asked to design artificial hearts.

High School Lesson
Doing the Math: Analysis of Forces in a Truss Bridge

Learn the basics of the analysis of forces engineers perform at the truss joints to calculate the strength of a truss bridge known as the “method of joints.” Find the tensions and compressions to solve systems of linear equations where the size depends on the number of elements and nodes in the trus...


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


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


Liz Harper

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.

Last modified: November 1, 2021

Free K-12 standards-aligned STEM curriculum for educators everywhere.
Find more at TeachEngineering.org