Describe a series of steps how table salt in water makes a solution that can conduct electricity?

Answer 1

The electrical conductivity of water, both pure water and water with dissolved salts, is simpler to measure than to explain. Conductivity of water does not work like conductivity in a metal. In a metal, the outer electrons of the metal atoms are not tightly bound to specific atoms but rather distributed widely and are pretty much free to move in response to an electric field. When you apply a voltage to a metal you get a large flow of electrons.

In water, the application of a voltage results in the movement of charge, but the charges are not nearly-free electrons but rather ions (charged atoms or molecules). In pure water, the ions that are moving are the protons in the form of H3O+ and hydroxide ions, OH-. In other ionic solutions it is the dissolved ions themselves, for instance in salt water, sodium chloride dissociated into the ions Na+ and Cl-.

In some way, the conductivity of an ionic solution is easy to explain. When a voltage is applied, there develops an electric field. Any atom or molecule that has a net charge, q, feel a force, F=qE. Positive ions move in the direction of the field and negative ions move in the opposite direction. Both sets of moving charges add to make a current flows that in the direction of the field.

Of course, one expects that dragging an atom or molecule through a liquid is a lot harder than moving an election through a metal and thus one is not surprised that the conductivity due to ion motion is small. Sea water conducts electric current about a million times better than pure water and drinking water varies depending on the source, but might be a hundred to a thousand time more conductive than pure water. A metal, like gold, copper, aluminum will be a million times better than seawater at conducting electricity while an insulator like glass or rubber is a million times worse than pure water.