Given mercury, diamond, hexanes, a solution of sodium chloride, water, plastic, and solid potassium chloride, WHICH substances are electrical conductors?
Conductivity depends on free electrons or charged particles that are free to move.
An electrolyte is a material that produces an electrically conductive solution when dissolved in an aqueous solution.
Clearly, hexanes, plastic, and diamond are also non-electrolytes. Water is very weakly electrolytic due to the autoprotolysis reaction: