Oxidation is defined as which of the following?

• A. A process of mixing oil and water
• B. When oxygen combines with an element, changing its appearance
• C. The loss of electrons
• D. The breaking of chemical bonds by heat

Answer: (B)

Oxidation is described here as the process where oxygen combines with another element, often producing a visible change in appearance. This plain, observable way of talking about oxidation explains why you might see rust on metal or a color change when substances react with oxygen. In many basic science contexts, oxidation is taught as oxygen joining with a substance and altering its look or state, which is why this option is considered correct.

The other ideas point to different chemical phenomena: mixing oil and water is simply a physical separation with no chemical change; the loss of electrons is a more precise, modern definition of oxidation but isn’t how this question is framed; and breaking chemical bonds by heat describes thermal decomposition, not oxidation.