At this point there is no further macroscopic change in the concentration of solvated partciles. We say the solution is saturated . Often the concentration of solute at higher temperature is greater than the concentration at lower temperature. If a hot nearly saturated solution with no solid present is carefully cooled, it is possible that no crystallization will occur, in spite of the fact that more solute is dissolved than should be dissolved at this concentration. We say the solution is supersaturated .
Most ionic solids are endothermic upon dissolution.
Gases almost invariably have an exothermic dissolution. Thus nearly all gases are more soluble at low temperatures than at higher temperatures. B. Pressure Effects Pressure has virtually no effect whatsoever on the solubility of a solid. However, the solubility of a gas is nearly proportional to the partial pressure of the gas above the solvent. Thus, the greater the partial pressure of a gas over a solvent, the greater the amount of gas dissolved in the solvent.