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How many grains of sand does it take to make a pile?

The question is nonsensical, because a phase of matter is an emergent property of a collection of atoms or molecules, just like being a pile is an emergent property of a bunch of sand.

Add to that the notion that "molecule" is kind of vague in any case, and you've got a world-class mess on your hands.

Sure, it's quite clear what the unit of C<sub>2</sub>H<sub>5</sub>OH is, and that it is a molecule, but for NaCl, what constitutes the unit? What constitutes the "molecule"? Is there one?

What about polymers, or diamonds? Is a diamond with its multitudes of covalent bonds a single molecule? Is it many? Is (C<sub>3</sub>H<sub>6</sub>)<sub>n</sub> n molecules, or one?

I'm afraid the question leads you down a philosophical rabbit hole that goes far beyond the science of chemistry.