After this lesson, you should be able to...
Conductivity is the ability to conduct electricity. For a substance, mixture, or solution to conduct electricity, it must contain charged particles that are free to move or migrate. In a conductive solution dissolved ions are the mobile charged particles. When an electrical potential is applied to a solution with a small AA battery (as shown in the diagram) negatively charged ions migrate towards the positive electrode and positively charged ions migrate towards the negative electrode (indicated by the yellow arrows). In other words, opposites attract, a concept we are familiar with. This movement of charged particles is an electrical current.
Electrolytes are substances that dissolve in water and dissociate into ions. Substances can be classified into three categories: strong electrolytes, weak electrolytes, and nonelectrolytes. Strong electrolytes dissociate completely into ions when dissolved in water. Solutions containing strong electrolytes are good conductors because the ions produced when these substances dissociate allow the solution to conduct electricity. Weak electrolytes are substances, when dissolved in water, where only a fraction of the molecules dissociate into ions. Since very few ions are produced, solutions of weak acids are poor conductors. Nonelectrolytes are substances that do not dissociate into ions when dissolved in water. Since no ions are produced, solutions of nonelectrolytes are nonconductive.
In the simulation below, you can see how molecular compounds like sugar compare to salts like NaCl when dissolved in solution. On the "macro" level, we can see this with respect to conductivity. Notice how with more salt, the solution is more conductive. In the "micro" view, you can see how these atoms/molecules behave when dissolved. In the "water" view you get a glimpse of the solution process.
Simulation: https://phet.colorado.edu/sims/html/concentration/latest/concentration_en.html