Magnetic Slime

Take your slime to the next level and increase the science fun with magnets!

What you will need:

  • Liquid starch (found in grocery stores near spray starch, washing and ironing aids)
  • White school glue
  • Water
  • Iron filings, or iron oxide powder (which can be bought online or in some large stores), or black magnetite which you can get by using a magnet in some outdoor sand (not playground sand)
  • Mixing bowls (disposable recommended)
  • Mixing tools (disposable spoons or craft sticks recommended)
  • ¼ cup measuring cup
  • 1 Tbsp. measuring spoon
  • Strong magnets (like bar magnets or rare earth magnets, which can be bought online or in some large stores).
  • Disposable gloves

Safety note: Rare earth magnets can be very strong. Use caution when trying to pull them apart or when bringing them near each other as they may pinch fingers when attracting.
Also: Wearing gloves as you mix in your magnetic material can help avoid staining your fingers.

Here’s what to do:

  1. Pour ¼ cup of water into a bowl.
  2. Add ¼ cup of white school glue to the water and mix well.
  3. Pour ¼ cup of liquid starch into a second bowl.
  4. Stir 2 Tablespoons of your magnetic ingredient (iron filings, iron oxide, or magnetite) into the starch. Stir until well mixed.
  5. Add the glue solution to the starch solution and stir.
  6. Stir well until the slime comes together and most of the liquid and magnetic ingredients are incorporated. It will become hard to stir.
  7. Put on gloves (or the excess liquid with the magnetic ingredient may stain parts of your hands black). Then, take the slime out of the bowl and continue mixing with your gloved hands. If there is some liquid left in the bowl that is okay. You can throw it and the bowl in the trash.
  8. When the slime seems mostly solid and isn’t wet anymore, take off the gloves, wash your hands, and play with the slime.
  9. You can start experimenting with your slime now! But keep squeezing and stretching it for at least 15 minutes for the reactions to complete to get to optimal sliminess.
  10. Get your magnet. What happens if you hold your magnet close to, but not touching, the slime? Can you use the magnet to move your slime around?
  11. When you are done playing with your slime, store it in a bag or in a bowl covered with plastic wrap. Wash your hands!
  12. You can save your slime in a plastic sandwich bag for about a week, in the refrigerator is best. When you’re finished making discoveries, throw the bag of slime in the trash. Do not try to wash it down the drain.

Take it further:

  • How is magnetic slime different from non-magnetic slime? What interesting shapes can you make the slime into using your magnet?
  • What happens if you use more than one magnet stuck together? Does the slime react differently?
  • Can you make your slime flow like a liquid? Can you roll it into a solid ball?
  • If you’re able, try making the slime again with a different magnetic ingredient. For instance, how are the slimes different if you use iron filings versus black magnetite sand?
  • What happens if you change the slime recipe? Is the slime different if you don’t use any water? What happens if you double the amount of the magnetic ingredient?

What’s going on?

Slime is a great chemistry experiment! White school glue is a polymer, which is a type of molecule made of identical units repeated to form a long chain. The glue by itself is kind of like a bowl of spaghetti noodles, all the polymer chains are flexible and not aligned in a particular way, so the glue flows somewhat easily. If you were to dump that bowl of spaghetti on the floor and reach to pick up a noodle, you’d get just that: one noodle! When the starch is added, a chemical in the starch cross-links the glue polymers which attaches the polymer chains to each other, making bigger molecules; the glue polymers can no longer slide by each other and flow like before because the molecules are too big. The mixture has become more viscous or thicker and more resistant to flow. If you were to dump this bunch of polymers on the floor and go to pick up one, you’d get a bunch because they’re connected now. The glue and starch mixture is a non-Newtonian fluid known as slime! It can be squeezed, stretched, pulled, and sometimes bounced, and can act like a liquid and a solid due to the interesting properties of the polymer molecules.

This slime has another unique property because we added a magnetic ingredient! When you hold a strong magnet near the surface of the slime, eventually, the slime will reach up or out toward the magnet. When you take the magnet away, the slime should fall back down. If you use a really strong magnet, the slime may even jump to the magnet and engulf it completely! Why does this happen? The iron in the slime is attracted to the magnet, but is also trapped in the slime due to adhesion, a force that holds different types of molecules together, so the iron takes the slime with it to the magnet. The slime molecules are bonded together by the cross-linking and by cohesion, a force that holds identical molecules together. When playing with your magnetic slime, there’s a bunch of science happening! The magnetic force is attracting the iron, while the adhesion is holding the iron in the slime, and the cross-linking and cohesion forces are holding the slime to itself; these various forces cause the awesome stretchiness and interesting shapes you can make with your slime.

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