Those solutions that do not undergo ionization have the solute molecules solvated within the solution and are called non-electrolytes. Such solutions will not conduct electrical current because of the absence of ions within the solution. Those solutions whose molecules undergo ionization during the solution process are called electrolytes and those solutions will conduct electrical current because of the presence of ions. When solutions form the solvent molecules form solvent cages around the solute molecules. This solvation process involves a certain amount of thermal energy to be exchanged between the solution system and its immediate surrounding environment.
Some solutions absorb energy as they are formed.
The solution is said to have an endothermic Heat of Solution. Most aqueous solutions involving liquid or solid solutes will have endothermic Heats of Solution. However, a few are exceptions to this statement. Other solutions involving gaseous solutes in water will release thermal energy during the solution formation process. These solutions are said to have an exothermic Heat of Solution.