Why is water denser than air?

The reason that all liquids (and solids) are denser than all gases (at “normal” temperature and pressure) is that the molecules of gasses are much farther apart. A liter of air contains about 2.7x[math]10^{22}[/math] molecules. read more

This is what actually occurs in the gas phase, water vapor is less dense than air. Water is mostly in the liquid phase, with molecules much closer to each other, at room temperature and atmospheric pressure due to intermolecular forces. read more

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. read more