Which of the following liquid is a poor conductor of electricity?

Analysis

The question asks us to identify which of the listed liquids is a poor conductor of electricity. To solve this, we must understand what makes a liquid conduct electricity.

Concept Explanation

For a liquid to conduct electricity, it must contain free ions (charged particles) that can move through the solution to carry an electric current. This process is known as electrolytic conduction.

• Pure water (distilled water) consists of $H_2O$ molecules. It is a covalent compound and does not dissociate into ions to any significant extent. Therefore, it is an insulator.
• Tap water, sea water, and drinking water contain dissolved mineral salts (like sodium chloride, magnesium, and calcium salts). These salts dissociate into ions ($Na^+$, $Cl^-$, etc.) when dissolved in water, making these liquids good conductors of electricity.

Step-by-Step Solution

1. Evaluate Sea water: Contains a high concentration of dissolved salts (sodium chloride). It is an excellent conductor.
2. Evaluate Tap water: Contains dissolved minerals and chlorine from water treatment plants. It is a moderate conductor.
3. Evaluate Drinking water: Similar to tap water, it contains dissolved minerals necessary for health, which allow it to conduct electricity.
4. Evaluate Distilled water: This is water that has been purified through distillation, removing all dissolved salts and minerals. Because it lacks free ions, it cannot conduct electricity effectively.

Conclusion

Since distilled water lacks the dissolved ions necessary to facilitate the flow of electric current, it is classified as a poor conductor (or an insulator) compared to the other options provided.

Exam Tip: Always remember that "pure" water is a poor conductor. If you see a question about water conductivity, look for terms like "distilled," "deionized," or "pure." If the water has "impurities" (minerals/salts), it will conduct electricity!