Humidity affect Density?

  • Thread starter khaichou
  • Start date
  • #1
2
0

Main Question or Discussion Point

Hi, as the topic stated, i would like to find out, does the humidity in the air affect the density??
thanks
 

Answers and Replies

  • #2
minger
Science Advisor
1,495
2
I wouldn't see how it couldn't. I would think you would need to do a partial pressures analysis to see the water content (prolly involving a psychometric chart). Then using a ratio of densities of water/air at that temperature to get the overall density.

But this is definately just a guess.
 
  • #3
BobG
Science Advisor
Homework Helper
185
80
The molar mass of air is almost 29. The molar mass of water is 18. The more 'less dense' gas you have intermixed into the air, the less dense the air. So, yes, humid air is less dense than dry air.
 
  • #4
DaveC426913
Gold Member
18,718
2,204
My gut tells me that humid air is more dense than dry air.
(edit)
My gut, apparently lies:

http://www.usatoday.com/weather/wdensity.htm
"Most people who haven't studied physics or chemistry find it hard to believe that humid air is lighter, or less dense, than dry air."

BobG seems to be right on the money.
 
  • #5
Astronuc
Staff Emeritus
Science Advisor
18,797
1,944
BobG said:
The molar mass of air is almost 29. The molar mass of water is 18. The more 'less dense' gas you have intermixed into the air, the less dense the air. So, yes, humid air is less dense than dry air.
That's exactly it - diatomic molecules N2 and O2 have approximate molecular masses of 28 and 32 (and air is 78+% N and 21+% O with traces of other gases), which in humid air are displaced by H2O, which has a molecular mass of 18.
 

Related Threads on Humidity affect Density?

  • Last Post
Replies
6
Views
3K
  • Last Post
Replies
7
Views
11K
Replies
1
Views
1K
Replies
1
Views
2K
Replies
3
Views
4K
Replies
8
Views
9K
Replies
2
Views
595
Replies
3
Views
3K
Top