Salt dissolves in water and disappears completely

Why

Tanya's reasoning follows the same 'looks different, so it must be different' logic that trips up the wax and rust questions too — the salt truly has vanished from view, which does feel dramatic enough to be chemical. Vanishing from sight is not the test, though; the test is whether the salt is still chemically salt. Dissolved salt hasn't turned into anything new — it has simply broken into particles far too small to see, scattered evenly through the water. It is still exactly the same substance, which is provable in the most direct way: boil the salty water away and the salt reappears, fully itself, with the same taste and the same crystal chemistry it had before. Test: taste a pinch of the boiled-dry residue — it is unmistakably salty, because it never stopped being salt. Her friend is right: dissolving spreads salt out until it's invisible, but doesn't change what it chemically is, which is exactly why it comes back unchanged when the water is removed.