Tuesday
September 16, 2014

Homework Help: chem

Posted by Natalie on Wednesday, April 18, 2007 at 8:58pm.

plz help

If you carefully place a steel razor blade flat on the surface of water, the razor blade can be made to float. Explain this result, given that the density of steel is much greater than that of water.

I'm not really sure what the answer is. I think it has something to do with either the way water responds to silicon oxide as with capillary action resulting in a meniscus or maybe it has to do with hydrogen bonds. Am I anywhere near the answer?

Read about surface tension, and how it is caused in water by hydrogen bonds.

http://hyperphysics.phy-astr.gsu.edu/hbase/surten.html

Is it like the:

Floating a needle
If carefully placed on the surface, a small needle can be made to float on the surface of water even though it is several times as dense as water. If the surface is agitated to break up the surface tension, the needle will quickly sink.

I still don't quite understand, though, what it is that the needle and steel particularly have that makes them float.

You miss the point. The surface tension of the water presents a surface that is not easily broken and it's that surface on which the needle floats. In a sense, the surface is like a board, but of course not nearly as strong as a board. If the water is stirred, the "board" is broken up and the needle has nothing to keep it afloat so it sinks.

So surface tension makes the surface strong, in a way?

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