“Water conducts electricity well”

It's a widely held belief that water is an excellent conductor of electricity, a notion often instilled in us from a young age due to safety warnings. However, the scientific truth is quite surprising: truly pure water, such as distilled or deionized water, is actually an excellent insulator. It has very few free ions to carry an electrical current, making it a poor conductor. The resistivity of deionized water can be as high as 18.2 megohm-centimeters.

The origin of this common misconception lies in the fact that the water we encounter in our daily lives—tap water, lake water, ocean water, or even rainwater—is far from pure. Water is an exceptional solvent, earning it the title of "universal solvent". As it moves through the environment, it readily dissolves various substances, including minerals, salts, and gases, which break down into electrically charged particles called ions. These dissolved impurities, such as sodium, chloride, calcium, and magnesium ions, are the actual conductors of electricity. The more dissolved ions present, the higher the water's conductivity. For instance, seawater, with its high salt content, is significantly more conductive than freshwater.

Therefore, the reason people commonly believe water conducts electricity well is due to practical experience. Since natural water sources always contain dissolved ions, our everyday interactions with water, whether in a shower or a swimming pool, involve water that *does* conduct electricity. This reinforces the myth and underscores the critical importance of electrical safety around any non-pure water. The danger isn't from the water molecules themselves, but from the invisible passengers they carry.