Kaplan Nursing Entrance Practice Exam

What does passing an electric current through water demonstrate about water?

1. It is an element

2. It is a compound

3. It has high conductivity

4. It is a nonpolar substance

The correct answer is: It is a compound

Passing an electric current through water demonstrates that water is a compound. Water is composed of two hydrogen atoms bonded to one oxygen atom, which classifies it as a chemical compound with unique properties different from those of the individual elements. The passage of electric current through water suggests the presence of ions, which can only occur in a compound that dissociates into its constituent ions (H⁺ and OH⁻) when dissolved, particularly in the case of pure water with some impurities or electrolytes. While water does have certain degrees of conductivity, that specific aspect does not alone define its nature as a compound. High conductivity typically relates more to the presence of dissolved ions or impurities, rather than the fundamental identity of water itself. Similarly, although water is classified as a polar molecule due to the electronegativity difference between hydrogen and oxygen, that characteristic does not define its status as an element or compound. The definition of water being a compound is the most accurate answer given what occurs when an electric current is introduced.