Water is lighter than air

April 27, 2003 on 3:06 am | In Ad Rem | Comments Off

What is lighter than air? Most would assume not much. There is a newly discovered sponge-like material that fits this category, but I may discuss that at another time. Water is actually lighter than air. This can be directly observed by viewing clouds. Separated molecules of water float on a layer of relatively dense air.

To explain why, when water is so light, does it sit below the atmosphere in the oceans you have to understand the extreme density of water. Water has a much stronger attractive force than do most gaseous molecules. The volume of 1 kilogram of water is much smaller than is 1 kilogram of, say, Nitrogen. However once separated you will find the lighter molecules begin to evaporate and are forced upwards by the greater weight of the surrounding air.

In clouds you have water molecules loosely moving through the atmosphere. As the area which makes up the cloud becomes denser with water it begins to coalesce into rain. Again, as dense water weighs more, it begins its downward fall.

There is a very fascinating story on the rain and heat cycles of the earth I will discuss soon.