On a trip to the salt pans near Thoothukudi, Pallavi explains that salt is made by leaving…
On a trip to the salt pans near Thoothukudi, Pallavi explains that salt is made by leaving seawater in shallow beds under the sun until the water evaporates. Joseph says that's far too slow — it would be quicker to pour the seawater through a fine cloth and collect the salt left on the cloth. Whose method will actually give salt?
Who do you think is right? Pick one.
The answer: Pallavi is right, dissolved salt is separated by evaporation
Why
Joseph is thinking of filtration, which is a real and useful method — a cloth does hold back sand, leaves or used tea leaves. But filtering only catches things present as solid bits bigger than the gaps in the cloth. The salt in seawater isn't floating around as grains; it is dissolved, broken up into pieces far smaller than any gap in any cloth, so it flows straight through with the water. What comes out the other side is just as salty. To get dissolved salt back, the water itself has to be removed — and evaporation does exactly that: the sun turns the water into vapour, and the salt, which doesn't evaporate, is left behind as crystals. Slow, yes, but it is the method that works. Test: pour a glass of salty water through a clean handkerchief and taste the water that comes through — still salty, and nothing is left on the cloth. Pallavi is right: dissolved salt can't be caught by a cloth, so salt is made by evaporating the water away.
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