Originally Posted by
andr0id
Let's suppose we have a bucket of a given size into which you can place molecules.
Suppose for our experiment H20 weighs 18. O2 weighs 32, and N2 weighs 28.
It starts out full of only O2 and N2. Now take some of those out and put in some H2Os. The bucket is lighter and therefore less dense. I guess spread out may be imprecise, but a water molecule is less dense for its 3 atoms than 2 atoms of either of the other gases.
In other words, by your own example, the distance between molecules is exactly the same. It's good to know you believe in the ideal gas law.