(May 10, 1998) For this week's experiment, we will examine something that has
caused
problems for Moms throughout the ages. While washing up, someone leaves
a towel hanging over the side of a sink full of water and mysteriously,
the water all winds up on the floor.
For this experiment, you will need:
two glasses
water
a paper towel
Fill one glass with water. Place the empty glass beside it. Tear a
strip of paper towel long enough to reach from the bottom of the full
glass to the bottom of the empty glass. Place this paper strip into the
glasses, so that it touches the bottom of each. Now let the entire
setup sit for a while. Check on it periodically to see what is
happening.
What happened? First, you should have noticed that the water soaked
into the paper towel and began to climb upwards. This is due to
capillary action. The surface tension of the water pulls it into the
space between the fibers of the paper. When the water climbs to the top
of the paper towel, it begins to flow downward, into the paper towel in
the empty glass. Gravity pulls the water down, leaving room for more
water to rise up from the full glass. This will continue as long as the
water level is higher in one glass than the other. Once the water level
in the two glasses is equal, then the water will stop flowing.
When you wash dishes for your Mom tonight (of course you will!), be
sure not to leave the dish cloth hanging over the side of the sink.
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these
experiments on my web site.
