Which process is defined as the chemical change that occurs when an electric current passes through a substance?

• A. Electrolysis
• B. Oxidation
• C. Reduction
• D. Ionization

Answer: (A)

When electric current flows through an electrolyte, it drives chemical reactions at the electrodes that transform the substances in the cell. This is electrolysis: electrical energy is used to force a chemical change, such as decomposing a compound into its elements or depositing a metal onto a surface. The process involves redox reactions at the electrodes—oxidation occurring at the anode and reduction at the cathode—prompted by the external current.

Oxidation and reduction describe electron transfer steps that can occur in many reactions, not necessarily caused by an outside current. Ionization is the formation of ions from atoms or molecules, which isn’t about driving a chemical change with an electric current in an electrolytic cell.