Not sure how this can get, but how is that two atoms of hydrogen and one atom of oxygen combine into something (water) that’s heavier than air even though they’re lighter than air separately?
In: Chemistry
The key here is being careful with the words “lighter” and “heavier”. Obviously, 1 pound of water weighs the same as 1 pound of air: they both weigh 1 pound.
The difference is that, in normal circumstances on earth, 1 pound of air takes up a lot more space. It takes about 12 cubic feet of air to weigh one pound, according to Google, while it only takes about 0.016 cubic feet of water.
And this is what we usually mean when we say air is lighter than water: the *same volume* of water weighs more than the same volume of air, under normal conditions.
A follow up question could be “why is it that the same volume of water weighs more?” The answer is that water molecules are funny shaped with a positively charged side and a negatively charged side, so that one side will attract the other side of another molecule. This means they tend to pull together and you get more molecules in the same volume. H_2 and O_2 molecules do not have that property, and tend to repell each other more, causing the molecules to spread out.
Of course, you could then ask why water is funny shaped, and that’s because of a balance of electric forces that really would be better described with pictures, and should probably involve words like “valence”.
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