Electrolytes conduct electricity while in their molten state or when dissolved in water, but nonelectrolytes do not conduct electricity in these states. This is due to the type of bonding holding the molecules together. Ionically bonded substances act as strong electrolytes; covalently bonded substances typically form nonelectrolytes, but they can also form weak electrolytes.
The strength of the electrolyte is characterized by how strongly the substance dissociates into cations and anions in water, which then allows for the transfer of electrons in water. This can be observed by placing the electrodes of a circuit containing a light bulb in water and seeing if the bulb lights. If the electrodes were placed in pure water, nothing would happen since pure water is a nonconductor. Ionically bonded substances, such as table salt and strong acids and bases, dissociate completely, while nonelectrolytes, such as sugar, simply dissolve. Polar covalent substances, such as weak acids and bases, partially dissociate and make little ions. Substances dissociate in water because water molecules are polarized, which causes it to attract the cations and anions in the substance's molecules and pull them into the solution and distribute them. Scientists use the information about whether a substance is a strong or weak electrolyte or a nonelectrolyte as clues to the type of bonding in a compound.