Polar substances are likely to dissolve in polar solvents. For example, ionic compounds, which are very polar, are often soluble in the polar solvent water. Nonpolar substances are likely to dissolve in nonpolar solvents.or example, the solution of sodium hydroxide is exothermic, and the solution of sodium chloride is somewhat endothermic. Even if the solution is slightly endothermic, the tendency to shift to the higher entropy solution often makes ionic compounds soluble in water.