According to the U.S. Geological Survey Water Science School, water is considered the universal solvent because it dissolves more substances that any other liquid. Because of water’s chemical properties, where one side (hydrogen) is a positive pole and the other (oxygen) is a negative pole, water molecules attract other molecules. Very strong attraction, as with salt (NaCl), breaks the chemical bonds between the components, sodium and chloride, dissolving the salt.
Wherever water goes, it carries with it vital minerals, nutrients and chemicals. Water is vital to life because it transports nutrition and minerals throughout living bodies. Because the human body is 70 percent water, for example, human biology relies on water’s solvent properties to function. As chemical bonds in minerals and chemicals weaken in the presence of water, they become surrounded by polar water molecules. This process is called hydration.
Water is also essential in maintaining proper salinity in the oceans. Cycles of evaporation and precipitation redistribute water so that its polarizing effect hydrates the salt molecules in the water and spreads them apart to achieve chemical balance, so that sea water remains isotonic, about 1 percent salt.
Because water is such a strong solvent, it is almost never pure, that is, just water.