Why is water a good solvent?

Water is called the "universal" solvent because it can dissolve both ionic substances as well as polar covalent substances.

Because water ##H_2O## has a large difference between the attraction for electrons. ( Oxygen has an of 3.5 and Hydrogen has an electronegativity of 2.2). There is a positive side of water (the Hydrogen) and a negative side (the Oxygen). This allows the water to break up and dissolve substances with character, such as salts.

Water is a molecule so it can dissolve other substances which are polar covalent such as sugars, alcohol, and most organic molecules.

Water can not dissolve non polar molecules such as gasoline. However non polar substances are not common, meaning water can dissolve most substances.

Water also has a large liquid range of ##100^@C##, which makes it an excellent solvent.