Many ways for example they look up related things and study them or they can test it and see what happens
In a mixture, there will be a solute and solvent. The hydrogen and oxygen are still two different atoms that just mixed together. But in a compound, the hydrogen and oxygen have a bond, making a new and bigger molecule. A mixture can easily be separated by physical means but a compound isn't.
I don’t know sorry ;khbadkhb didhwbck( khwdicdwbihwd
It would be 2300000 grams.