surface TENSION
Water and other liquids behave as though they were
covered by a thin "skin." This is because their surface molecules have
no similar molecules above them as the deeper molecules have. Therefore,
they pull sideways on each other more strongly. You can experiment with
surface tension in many ways.
MATERIALS: Small (clear) plastic cups; water;
paper clips, buttons, etc.; needles or razor blades; toothpicks; soap
HOW TO DO IT:
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fill a cup to the brim with water. then start
dropping in buttons or paper clips one at the time. You may be
surprised at how many you can get in before the water spills
over.
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In a fairly full cup of water, float a needle or a
razor blade. If it is lowered gently to the water (use a fork) it will
float. What happens if a tiny amount of soap is added to the water?
Soap destroys surface tension. The floating objects will sink.
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Fill a cup to the brim. Put a small amount of soap
in the water and it will run over.
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Fill a cup of water less than full. Break up a
couple of toothpicks into small pieces and put them into the water.
They will migrate to the sides of the cup. Now carefully fill the
glass with water. The pieces suddenly all come to the center.
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