Solubility
When salt dissolves in water, a clear solution is formed. This is because the solute, salt, breaks down into particles so small that they are invisible to the naked eye and mixes evenly with the solvent, water.
What happens if you continue to dissolve salt in water? If you add salt to a fixed amount of water, it dissolves up to a certain point; beyond that, no more will dissolve and the excess settles at the bottom. Thus, there is a limit to the amount of solute that can dissolve in a given amount of solvent. The maximum mass of solute that can dissolve in 100 g of solvent is called the solubility of that substance.
Even for the same substance, the amount that dissolves varies with the temperature of the water. Since the solubility of most solids increases as temperature rises, the solubility curve slopes upward to the right.