Which is more dense, humid air or dry air?

Answer 1

(m)

To see why humid air is less dense than dry air, we need to turn to one of the laws of nature the Italian physicist Amadeo Avogadro discovered in the early 1800s. In simple terms, he found that a fixed volume of gas, say one cubic meter, at the same temperature and pressure, would always have the same number of molecules no matter what gas is in the container. Most beginning chemistry books explain how this works.

Imagine a cubic foot of perfectly dry air. It contains about 78% nitrogen molecules, which each have a molecular weight of 28 (2 atoms with atomic weight 14) . Another 21% of the air is oxygen, with each molecule having a molecular weight of 32 (2 stoms with atomic weight 16). The final one percent is a mixture of other gases, which we won't worry about.

Molecules are free to move in and out of our cubic foot of air. What Avogadro discovered leads us to conclude that if we added water vapor molecules to our cubic foot of air, some of the nitrogen and oxygen molecules would leave — remember, the total number of molecules in our cubic foot of air stays the same.

The water molecules, which replace nitrogen or oxygen, have a molecular weight of 18. (One oxygen atom with atomic weight of 16, and two hudrogen atoms each with atomic weight of 1). This is lighter than both nitrogen and oxygen. In other words, replacing nitrogen and oxygen with water vapor decreases the weight of the air in the cubic foot; that is, it's density decreases.

Answer 2

Humid air is lighter than the dry air and the explanation why (which at first seems contrary to common sense) is provided by another friend here, who deserves congrats.

Answer 3

Easy :) Humid air because it consists of water vapor! Water as we all know is more dense than air (because we can keep it in swimming pools =P) and so, adding the whole water factor to the air naturally makes it more dense than air without any additives.

Answer 4

humid air, water vapor makes it denser. and thats why when u go 2 mexico its harder to breathe because the air is so thick and humid

Answer 5

humid air, because it contains water vapours in it.