What is Dew?

We've all seen dew develop on grass, glasses of water, soda cans, windows, etc.  But what is dew?  That's the important question.  Once we see something, we want to be able to adequately explain it.  So what is dew?

Dew occurs when water vapor in the air condenses to a liquid on a surface.  How does that happen?  Take a glass of ice water for example.  Unless you have a well insulated container, drops of water (dew) will form on the side of the glass.  It's not water seeping through the glass.  I used to think this as a kid, but I was completely wrong. :-) Instead, it has to do with changing air temperatures.  The air immediately surrounding the glass cools as energy transfers from the air to the glass.  As the air cools, water vapor in the air drops temperature and changes phase from a gas to a liquid on the glass. 

The same occurs for pop cans, windows, plants, etc.  If the object causes the air around it enough to change the phase of the water vapor in the air, dew forms.  

There you go.  Knowledge is power!