What is the primary characteristic of weak electrolytes?

Weak electrolytes are substances that partially dissociate into ions when dissolved in water. This means that in a solution of a weak electrolyte, only a fraction of the molecules will break apart into cations and anions, while the rest remain intact as neutral molecules. This partial dissociation is what leads to their characteristic properties, such as low electrical conductivity compared to strong electrolytes, which fully dissociate.

For instance, acetic acid is a common weak electrolyte. When added to water, some of the acetic acid molecules dissociate into acetate ions and hydrogen ions, but many others remain as undissociated acetic acid molecules in the solution. This results in a lower concentration of free ions compared to a strong electrolyte like sodium chloride, which completely dissociates into sodium and chloride ions.

The other options do not accurately describe the behavior of weak electrolytes: they can still conduct electricity, albeit poorly, they do not completely dissociate, and they are not restricted to existing only in solid form; they are soluble in water and can be found in a liquid state in solutions.