Which of the following types of substances conduct electricity when dissolved in water?

• A. Nonpolar molecules such as O2
• B. Covalent compounds such as C6H12O6 (glucose)
• C. Ionic compounds such as NaCl
• D. Solid metals such as Cu when in solid state

Answer: (C)

Verified step by step guidance

1. Understand that electrical conductivity in aqueous solutions depends on the presence of charged particles (ions) that can move freely to carry electric current.
2. Recognize that nonpolar molecules like O\_2 do not dissociate into ions in water, so they do not conduct electricity when dissolved.
3. Know that covalent compounds such as C\_6H\_12O\_6 (glucose) dissolve as whole molecules without producing ions, so they also do not conduct electricity in solution.
4. Identify that ionic compounds like NaCl dissociate into their constituent ions (Na\^+ and Cl\^-) when dissolved in water, allowing the solution to conduct electricity.
5. Note that solid metals such as Cu conduct electricity in their solid state due to free electrons, but they do not conduct electricity when simply dissolved in water because they do not form ions in solution.