The effect of temperature on solubility depends on the type of reaction that occurs during the process of dissolving the solute in the solvent. In endothermic reactions, increasing the temperature increases the solubility of the solute in a solution. In exothermic reactions, increasing the temperature decreases the solubility of the solute.
During the dissolving process, heat is absorbed to break the bonds between the solute molecules, and heat is given off during the formation of new bonds between the solute and solvent molecules. If the heat absorbed is greater than the heat given off during the formation of new bonds, the process of dissolving the solute is endothermic. If the heat given off is greater than the heat absorbed, the reaction is exothermic.
In an endothermic reaction, adding heat to the reaction drives the reaction towards the product side. This means that increasing the temperature increases the solubility of the solute to drive the reaction towards forming the solution.
In an exothermic reaction, the heat given off is greater than the heat that is absorbed to break the bonds. Increasing the temperature by adding heat drives the reaction to the reactant side and decreases solubility. This means that decreasing the temperature increases the solubility of the solute.
