Why do certain substance's water solution conduct electricity and other do not?

Question

For example tap water will conduct electricty but distilled water will not. Copper sulphate in water will conduct while vegetable oil will not. Thanks :)

Answer 1

Distilled water is not an aqueous solution. It is simply pure water.

Vegetable oil is also not an aqueous solution. It is a nonpolar organic compound.

Solutions of acids, bases, or salts in polar solvents are conductive. Others usually aren't.

Ionizing solvents include water, methanol, ethanol, formic acid, acetic acid, hydrofluoric acid, hydrocyanic acid, sulfuric acid, and others. Non-ionizing solvents include carbon tetrachloride, chloroform (weakly ionizing), methylene chloride (weakly ionizing), hexane, benzene, toluene, and diethyl ether.

Answer 2

Excellent question! Deionized water is not conductive. It is the presence of ions dissolved in it that makes water conductive. Electrons are easily able to transfer from atoms in water. This is not the case with vegetable oil. The reasons for this have to do with the fact that oil, unlike water, does not undergo auto-ionization. Also, oils are actually polymers which have filled electron orbitals, However this is not the case for all polymers. The electrical conductivity of polymers are responsible for your LCD screens.

Answer 3

Distilled water (and vegetable oil) do not have any dissolved ions that can conduct the electricity between the potentials.  In tap water and your copper sulphate solution, you have dissolved ions through which the electrons can move.