The reverse of an exothermic reaction is endothermic and has a heat of reaction value of the same magnitude, but opposite sign. If a solid dissolves in water, its entropy increases. Entropy refers to motion inside molecules too. The chart shows the influence of temperature on spontaneity.
Higher temperatures enhance the importance of entropy over enthalpy.
Thus, a positive entropy will offset the effects of a positive D H at high temperatures making an endothermic process, such as melting an ice cube, spontaneous.