Solubility is the measure of how much solute can dissolve in a given amount of solvent.  Factors that have an effect on solubility are the nature of the solute and solvent, temperature and pressure.  An increase in temperature, increases the solubility of a solid solute.  When the solution is a gas, the solubility decreases as the temperature rises.  Changes in pressure, usually have no effect for a solid and a liquid.  It does have an effect on gaseous solutes.  An increase in pressure increases solubility.

            A substance can dissolve if the particles  of the solute separate and occupy other spaces.  Polar solvent  molecules separate the molecules of other polar substances.  When a positive end of a molecule meets a negative end of a molecule, there is a force of attraction.  The solute molecule is pulled into the solution when the forces are overcome.  Polar solvents can also dissolve solutes that are ionic.  Water is a polar substance.  Hydrated ions are ions surrounded by water molecules.  A solubility curve shows how much solute solute will dissolve in a given amount of solvent over a range of temperatures. (Dorin 336, 339, 340-341)