Final answer:
Among the substances tested, table salt (NaCl) is the one that caused the lightbulb to burn the brightest because it is a strong electrolyte that dissociates completely into ions in an aqueous solution, enabling efficient electrical conductivity.
Step-by-step explanation:
In Professor Popsnorkle's demonstration of electrical conductivity in solutions, the substances tested included ethanol (CH3CH2OH), methanol (CH3OH), table salt (NaCl), table sugar (C12H22O11), and acetic acid (CH3COOH). To identify which substance caused the lightbulb to burn the brightest, we must understand that only solutions containing freely mobile, charged species—ions—can conduct electricity. Among the choices, table salt, or NaCl, when dissolved in water, dissociates into sodium ions (Na+) and chloride ions (Cl-), making it a strong electrolyte and allowing the solution to conduct electricity very well.
The other substances listed are either weak electrolytes or nonelectrolytes. Ethanol and table sugar are nonelectrolytes and do not contain dissolved ions, and thus they would not make the lightbulb shine brightly. Methanol is also a nonelectrolyte like ethanol. Acetic acid is a weak electrolyte because it only partially dissociates in solution. Therefore, table salt (NaCl) is the one that caused the bulb to burn the brightest due to its ability to completely dissociate into ions, which conducted the electrical current efficiently in the aqueous solution.