Magic Eraser
Sometimes you’ve got to dig deep.

Concepts
Physical properties, porosity

Materials
1 Magic Eraser, 1 sponge, 1 crayon, bucket with water
Procedure
1. Write the number “11” on your desk with a crayon.
2. Moisten the Magic Eraser and the sponge with water and squeeze out the excess moisture.
3. Using the sponge wipe off one number “1.”
4. Using the Magic Eraser wipe off the other number “1.”
Results
Explain the results of your experiment below.
Make an inference explaining how the Magic Eraser works.


Explanation
A normal sponge is composed of loose fibers and a lot of empty space. This composition makes it effective at soaking up water and other liquids. The holes between the fibers soak up the water and cause the fibrous material to swell. This prevents the water from sloshing right back out of the sponge. Instead, the water is trapped inside until the sponge is forcibly squeezed. While good at absorbing and trapping water, a sponge is ineffective at removing a stain that is firmly adhered to a substance, such as crayon on a desk top.

Magic Erasers are made up of melamine foam, which is an organic polymer. Melamine foam is a hard material that is porous. These two physical properties, its hardness and porosity, make it a great cleaner. The rigidness of the foam allows it to scrape away parts of a stain while the open spaces inside of it trap material. Hence, the crayon on the desktop is effectively scraped off and then absorbed by the magic eraser.

figure37.jpg
Figure 37: A sponge (left) and a magic eraser (right) before the experiment.

figure38.jpg
Figure 38: Results of the experiment: after 10 swipes the sponge barely removes any crayon while the magic eraser wipes it clean.

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