Which statement about distilled water's conductivity is true?

• A. Distilled water conducts electricity when salt is added.
• B. Distilled water conducts electricity only when exposed to sunlight.
• C. Distilled water conducts electricity regardless of dissolved substances.
• D. Distilled water never conducts electricity.

Answer: (A)

Electrical conductivity comes from free ions moving in a solution. Pure distilled water has very few ions, so its conductivity is extremely low. When salt is added, it dissociates into positive and negative ions (such as Na+ and Cl−) that freely move in the solution, providing charge carriers and making the water conduct electricity. That’s why distilled water by itself is a poor conductor, but it conducts electricity when dissolved substances like salt are present.

The other statements don’t fit because sunlight doesn’t turn distilled water into a conductor in any meaningful way, conductivity isn’t guaranteed regardless of what’s dissolved (it depends on ion content), and distilled water can conduct a small amount even without added salts due to trace ions and self-ionization.