What Substances Dissolve in Water?
Any ionic compound in which the force of attraction between the oppositely charged ions is weaker than the force of attraction that water molecules exert on each ion, dissolves in water. Water is known as the universal solvent because it dissolves more compounds than any other chemical known.
A general outline and list of exceptions, known as the Solubility Rules, can help determine if a particular ionic compound dissolves in water or not. Some of the rules include all salts formed by group I elements as water-soluble and all carbonate salts as insoluble, except when bonded with ammonium or a group I element. Water's ability to dissolve and dissociate substances comes from its polarity.
In every water molecule, the bonds between the hydrogens and oxygen exhibit a dipole shift, which means that, although they are sharing electrons, they are not sharing them evenly. As a result, the oxygen side of the bond is slightly negatively charged. The positive side of the bond is slightly positively charged. These partial charges attract any opposite-charged ions or repel any similar-charged ions when an ionic compound in submerged in water.
If these forces are stronger than the ionic bond keeping the compound together, it dissolves. Because water solubility depends on polarity, nonpolar molecules do not readily dissolve in water.