* Solubility and Temperature: The solubility of most solids in liquids (like NaCl in water) decreases as the temperature decreases. This means that less of the solid can dissolve in the liquid at lower temperatures.
* Saturated Solution: A saturated solution holds the maximum amount of solute (NaCl) that can dissolve at a given temperature.
* Cooling Effect: When you cool a saturated solution, the solubility limit decreases. Since the solution was already holding the maximum amount of dissolved NaCl at the higher temperature, it now holds *more* NaCl than it can at the lower temperature.
* Precipitation: To reach a new equilibrium, the excess NaCl that can no longer stay dissolved will crystallize out of the solution. This is called precipitation.
In summary: Cooling a saturated NaCl solution causes some of the NaCl to precipitate out because the solution can no longer hold as much dissolved salt at the lower temperature.
