Sunday, October 24, 2010

Science Sunday: Why do water striders walk on water?


We read about how water striders walk on water.  Well, obviously you can’t just walk on water, so how do they do that?

 

Answer: they bend the rules.

 

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Supplies needed: small bowl of water, a piece of toilet paper, small needle

 

 

 

 

Procedure:  rip a piece of toilet paper into fourths.  Place the toilet paper on top of the water, and gently place the needle on top (like in the photo above).

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Now, if you’ve done this right, the toilet paper will be saturated by the water and the needle will float on the surface of the water.  It’s very cool.

 

 

 

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Why does this work?

 

Because water molecules have a very strong molecular bond they want to stick together.  So, the surface tension of the water holds the needle up, if you do it correctly.

 

That is why the water strider is able to walk on water.  Great wow factor to your kids.

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Then we of course had to see if it would work with a normal piece of paper, and it did. 

 

So, now we know how and why water striders can walk.

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