This model illustrates the process of NaCL dissolution in water. |
Water is known as the most universal of all solvents. This property of water is due to the fact that water molecules are electric dipoles. The molecules of substances that are electrolytes dissolve in water with amazing ease.
Consider an example. In the process of dissolving, NaCl crystal dissipates into ions. Water molecules in the solution closely surround each individual ion. Such a surrounded ion is called a hydrated ion. Note that the size of a hydrated ion (including the surrounding water molecules) is much larger than that of a free ion (or an ion that is a part of the crystalline structure.) This is the reason why the osmotic effects exist in electrolyte solutions.
Also, note that the molecules of water turn in a different direction as they approach the positive the ions of sodium and the negative ions of chlorine. Observe how the ions detach from the crystal under a sufficiently strong attraction of the water molecules.