system
Given the following post, respond as if you're commenting on Reddit:
human
Why is it so hard to desalinate ocean water?

I understand that our current method of desalination (evaporating the water and then collecting it again) consumes a ton of energy, but why do we need to do that method in the first place? What is it about salt in water that makes it so difficult to remove the salt?
gpt
Well, it's that the salt is...*dissolved*.  It's not like there are little chunks of salt floating around in the water.  The water has chemically broken the Na-Cl bond and all of the salt is floating around as Na+ and Cl- ions in the water.  That means you can't just filter it out with a normal gravity-fed mechanical filter.  You need to either boil off the water and condense it, or push the water *really hard* through a special filter that lets only H*_2_*O through.  Both of those require a lot of energy.