15. Explore Solubility Rules (here is more practice if you want to master the topic). Understanding these rules will help you to predict the physical state (solid, if the product is insoluble in water; or aqueous, if the product is soluble in water. Read "aqueous" as the ionic compound that is fully dissociated, separated, into its ions and surrounded by water molecules. In a precipitation reaction, these ions are the spectator ions located in the supernatant, the solution on top of the precipitate)