* Copper oxide is a solid. While some solids dissolve in water, many do not.
* Copper oxide is insoluble in water. This means it doesn't readily dissolve to form ions in solution.
* Copper oxide is amphoteric. This means it can act as both an acid and a base. In very acidic or very basic conditions, it might react to form soluble copper compounds.
In summary: While copper oxide doesn't form a visible precipitate in water, it also doesn't readily dissolve. It will likely remain as a solid in the water.
