Magnets, Math, and Measurement… Oh MY!

Density (the mass of a substance per unit of volume) is an important physical property of matter in the fields of engineering, chemistry, and math. If you measure both the mass and the volume of a given amount of iron filings, you can calculate the density (D) of iron filings by dividing mass (m) by volume (v). The equation is D = m/v. You can explore and compare the densities of the three different types of iron filings with the activity below.

But first, a quick safety warning! The Iron Filings 3-Pack is safety tested for ages 6+, but adult supervision is required. Do not inhale or consume iron filings. Keep iron filings away from eyes. Magnets are not included in this set, but make sure the magnets you use to interact with the iron filings are age-appropriate. Keep all small, powerful magnets away from children under age 8.

Okay, now…

  1. Gather the following materials:
  • Coarse, medium, and fine iron filings*
  • Digital scale
  • Water
  • Measuring cup, beaker, or graduated cylinder
  • Calculator
  • Pencil and paper
  • Paper towels
  1. Place a small pile of coarse iron filings on the scale and record its mass.

iron filings on gram scale









3. Add enough water to the cup/beaker/cylinder, so the water would cover the filings (but do not add the filings yet). Record this initial volume.











4. Add the pile of weighed, coarse filings to the container of water. Record the new volume.

mass measurement










  1. Subtract the new volume from the initial volume to obtain the volume of the coarse filings. 5. Divide the mass by the volume. Your answer is the density of the filings!
  1. Repeat steps 1–5 with the medium filings and then with the fine filings. Analyze and compare your results. What can you conclude about the density of the different iron filings? Why is the field of mathematics important to magnets and their properties?

*Discard iron filings after they have been in water. (They will rust.)

Put the rest of your Iron Filings to use with our other free downloadable activities, including The Art of Science, Mix It Up!, Let It Snow, and All Shook Up, on our blog!

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