Why is it so difficult to turn sea water in to drinkable water?
In: Chemistry
It isn’t technically difficult to turn salt water in to drinkable water, it just takes a lot of energy to do it. The reason for this is entropy, which in layman’s terms is a measure of disorder and randomness. The universe likes to be random, but it takes effort to make it orderly. Think about if you had a jar of salt, and a jar of sugar. If you pour them out into one pile, they will mix together with very little effort. But separating them back out into separate jars of sugar and salt again takes a lot of effort. When you put salt into water, the salt molecules spread out into the water molecules. Pulling them out again into separate containers takes a lot of energy.
Making salt water potable (drinkable) can be done in a number of different ways, including:
1. Distillation – Heat the water up until it boils into steam. The steam leaves the salt behind. Cool the steam back down and you have fresh water.
2. Reverse osmosis – With a lot of pressure, you can push water through a filter so fine that the salt molecules can’t go through it, and you get fresh water on the other side.
3. Chemical – You can make the salt molecules bond to chemicals added to the water, then remove those chemicals to get fresh water.
All of these methods require a lot of energy, in the form of heat, pressure, or manufacturing of special chemicals. All of these things have a high cost, and there aren’t many applications where it is cheaper to desalinate water than to just ship fresh water in from somewhere else.
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