Cohesion and Surface Tension Activity

 After learning what cohesion and surface tension was - we started to see it in action.  Here's some pics on how it went.

Remember Cohesion is waters attraction to other water molecules.  It wants to bind with FOUR other water molecules.  At the SURFACE of the water there is no other water molecules ABOVE, so it holds tight to the what it can below!

First I had you fill the jar up to the VERY top
with water.

So that it was actually slightly
OVER the top of the Jar

Then you slowly added pennies
into the already full jar

They you saw how many would fit
before it overflowed.

You were able to really "see" how attracted water is to itself as you were able to put a lot of pennies into the jar.  Again, the key thing to remember is that this property of water is all due to the HYDROGEN BONDS holding them together.  Until the pressure from the pennies below is greater than the attraction to each other, they will remain bonded to each other.

Until then - a "film" forms on the top of water that can hold a bit of weight.  I then had you guys try and float a pin on top of the water to show the strength of these hydrogen bonds.