Let's take a different mixture. Sodium Chloride (NaCl) - salt - and water.

Fun thing about NaCl is that they're like a nuclear couple, but they like to flirt with other NaCl. They create intramolecular attraction, but don't really BOND to other NaCl molecules. So a salt crystal doesn't become Na2000Cl2000 - it's just NaCl - just stacked like legos, or magnets.

In swoops in water, and it readily dissolves those intramolecular bonds. But may or may not actually break down that Na Cl.

So we can boil back out the water and we just end up with crystalline bar magnets stuck together again.

Except... water CAN break down the Na and Cl with sufficient energy levels, so you end up with an ocean of H2O, Na, Cl, and NaCl, but the Na and Cl don't break down the H2O.

Boil H2O out, though, and it's reversed back to NaCl, and you wouldn't necessarily be any wiser.

Except you can send in more chemicals that will fetch either Na, or Cl, but not H2O and not NaCl. Usually when that happens, it creates a film that floats to the surface, turns to a gas, or settles to the bottom.

But there are any other number of properties you might test. E.G. how does it react to UV light? What color is it? Lasers? What's the density? Etc.