Clean It Up!

Cotton balls
Fingernail file


1) Rub the side of the sharpened end of a pencil across the end of your finger to collect a layer of graphite (pencil lead) on your fingertip.
2) Gently rub a fingernail file back and forth across the graphite layer on your finger.
3) Observe your fingertip and the file.
4) Rub the fingernail file back and forth across a cotton ball.
5) Observe the surface of the cotton ball and the file. What happens?

This experiment might remind you of how one of your pets keeps itself clean.  Which animal uses its tongue to clean its fur?

Explanation: This experiment demonstrates how a rough surface can be used to clean another surface. The animal this experiment might remind you of is a cat! Cats lick their fur to clean it. A catís tongue feels like coarse sandpaper because of the tough pieces of skin, called papillae, sticking up in the center of the tongue. These bristles of flesh act just like the ridges on the fingernail file.  When the cat rubs its coat with its tongue, the papillae remove dust, dirt, and loose hair.

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