Solubility of Solids

The effect of temperature on the solubility of solids differ depending on whether the reaction is endothermic or exothermic. Using Le Chatelier's Principle, we can determine the effects of temperature in both scenarios.

First, imagine an endothermic reaction (heat is on the reactants side where the solid is). Increasing the temperature would result in stress on the reactants side from the additional heat. Le Chatelier's Principle predicts that the system would shift towards the product's side in order to alleviate this stress. By shifting towards the product's side, more of the solid is dissociated when equilibrium is again established - Which equates to increased solubility.

Second, imagine an exothermic reaction (heat on the product's side where the dissociated ions from the solid are). Increasing the temperature would result in stress on the products side from the additional heat. Le Chatelier's Principle predicts that the system would shift towards the reactants side in order to alleviate this stress. By shifting towards the reactants side, less of the solid is dissociated when equilibrium is again established - which equates to decreased solubility.

http://chemwiki.ucdavis.edu/Physical_Chemistry/Physical_Properties_of_Matter/Solutions/Solubility_and_Temperature#Solids_.26_Liquids