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Magic Comb

based on 20 ratings
Author: Danielle Abadam

A lot of things can act like magnets—they just need an electric charge. If we give a comb an electric charge, can it separate pepper from salt? Let’s find out!

Problem:

Can a comb separate salt and pepper?

Materials:

  • Plastic Comb
  • Pepper
  • Salt
  • Tissue
  • Notebook
  • Pen

Procedure:

  1. Lay the tissue flat.
  2. Pour some salt onto the tissue.
  3. Pour an equal amount of pepper onto the tissue.
  4. Mix the salt and pepper together until you achieve an even consistency.
  5. Do you think the comb can separate the salt and pepper? If so, how do you think it does this? Use this time to write down your guess, also called a hypothesis, in your notebook.
  6. Give the comb an electric charge by rubbing it through your hair a few times.
  7. Hold the comb about an inch above the salt and pepper.
  8. Slowly move the comb over the mixture.

Results:

The pepper particles will attach to the comb, leaving the salt in the tissue.

Why?

Salt and pepper both have neutral charges. However, the static electricity in the comb can change these charges. Because pepper is less dense than salt, it has more surface area that can be charged by the comb’s static electricity. This allows the pepper to be attracted to the comb, leaving the salt behind on the tissue. The salt may have been charged slightly, but not nearly as much as the pepper was.

What if you repeated this experiment using different substances? Keep experimenting. There’s a whole world of questions to answer!

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