Why does salt dissolve in water?
Salt dissolves in water. We all know from our chemistry classes that ionic compounds dissolve easily in water. Salt is also an ionic compound. If the existing water molecules do not accommodate salt any more, then no more salt continues to dissolve. This solution is called a saturated solution.
Water has two hydrogen atoms and one oxygen atom. Water acts as a dipole due to covalent bonding between charged hydrogen and oxygen atoms. It possesses partial positive charges on hydrogen atoms and partial negative charges on oxygen atoms. This distribution of charges makes water attract oppositely charged ions towards its polar atoms. When no other solute is present in the water, each water molecule forms hydrogen bonding with that of another, with the help of these charges. When there is any solute like salt added to water, the weak hydrogen bonding is overcome with the strong attractive forces between the water and salt. So, water forms ionic bonds with salt.
Salt has sodium ion that is positively charged, and a chloride ion that is negatively charged. The oppositely charged ions reach their opposite attractive poles of water. The positive charge on hydrogens attract negatively charged chloride ions, while the negatively charged oxygen attracts positively charged sodium ions towards them. This occurs due to the breakage of weak attractive forces that existed between intra molecular hydrogen bonding. The ionic bond is so strong that it can destroy the hydrogen bond. Even covalent molecules that have dipole can dissolve in water with the same physical phenomenon, but a non polar molecule, like oil, cannot be attracted towards the charges of water molecules, and hence, do not dissolve in it.
Salt dissolves in water as it carries a net electric charge that can make its charged ions be attracted by the oppositely charged ions of the water. These attractive forces between salt and water are stronger than the forces that exist between the sodium and chloride in salt.