In science, the term "insoluble" is used to describe substances with a low solubility. Solubility is the ability for a substance to dissolve when mixed with another substance to form a new compound.
Substances considered insoluble in science include most carbonates, sulfites, hydroxides, phosphates and sulfates. Some substances may be insoluble in some cases; for example, water is insoluble in alcohol, but it is soluble in acid.
The term "insoluble" can refer to gases, solids and liquids. The constant K_sp is used in chemistry to describe the solubility of certain types of compounds in water. In solubility, the solute is the substance that dissolves in another substance, known as the solvent.