The solubility of a substance is used to describe how much solute can be dissolved in the solvent.
Solutions can be either saturated or unsaturated (and even supersaturated which we will see in lab).
A saturated
solution contains all of the dissolved solute particles that it can hold.
If you added any more solute particles to a saturated solution, they would
not dissolve and you would observe solid particles in the solution.
An unsaturated
solution contains some solute particles but the solvent can still dissolve
more solute (until it reaches its saturation point).
Temperature Effect on Solubility
If you have ever brewed a pitcher of tea at home, you have probably discovered that it is easier to get the sugar to dissolve if you add it while the tea is still hot. If you order a glass of iced tea at a restaurant, it is very difficult to get the sugar to dissolve. This is because the solubility of sugar, as well as most solids, increases with increasing temperature.
In contrast, the solubility of most gases decreases with increasing temperature. Think about what happens if you open a cola bottle that is at room temperature. Does it "fizz" (release the carbon dioxide) more or less than a cola bottle that has been refrigerated for a few hours?
Insoluble salts
Earlier, we learned that in general, salts are soluble (and strong electrolytes). However, some salts are not good electrolytes because they are insoluble in water. Salts that are always soluble in water must contain at least one of the following ions: Li+, Na+, K+, NH4+, or NO3-. Most salts containing Cl- are soluble, except AgCl, PbCl, and Hg2Cl2 are insoluble. Look over Table 8.6 and 8.7 in your text to see how these solubility rules can be used to determine if a salt will be soluble or insoluble in water.
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