What Is Water Made of?
Every kind of substance in the world is made up of tiny portions, each of which is distinctly just what the whole mass is, but which are so small you cannot see them. A pile of sand, or a cupful of sugar or salt consists of a great many small grains. A cup of water too is made up of what we would call small grains of water, or what we would call grains of water if we could think of them in the same way as we do sugar or salt or sand. These particles are so small that they could not be seen separately, even if the particles did not have the ability to stick so close together that we could not distinguish them even if they were large enough to be seen.
The word used in describing these tiny particles in any substance, water, sugar, sand, salt or anything else is molecule.