|COMPARING THE DENSITY OF AIR TO WATER
METEOROLOGIST JEFF HABY
To the human eye, air is nearly invisible while water is clearly visible. Without dust, smog, and particulates
in the air, air would be invisible. It is amazing to many people that this "invisible" air moves substances like
tree branches around. Of course, we now know that the air does have mass even though it can not be seen with the
eye. If the air does have mass, why is it so hard to see? It is difficult to see because the air has molecular
properties that make it transparent. We will now determine how "much less" the density of air is to water. Water
has a density
of 1000 kg/m^3. If you had a meter cubed of water it would weight about 1000 kg.
Air that is near sea level has a density that averages 1.275 kg/m^3. If you have a balloon containing a meter cubed of sea level air, the air itself
would weight only 1.275 kg. Therefore, to find how much more dense water is than air all we need to do is find a
ratio of water to air. 1000 kg/m^3 divided by 1.275 kg/m^3 yields 784. Therefore, at sea level, air is 784 times
less dense than water. Expressed in another way, a volume of air at sea level has 0.1275% of the density of the
same volume of water. Dirt is about 2.5 times the density of water.