Which term describes the chemical process of combining substances to form new compounds?

The correct term that describes the chemical process of combining substances to form new compounds is synthesis. In chemistry, synthesis refers to the process where two or more reactants come together to create one or more products. This is fundamental in various chemical reactions, particularly in organic chemistry, where simpler molecules can form more complex structures.

Understanding synthesis is crucial in esthetics, especially when considering formulations for skincare products. Many active ingredients in cosmetics are synthesized to achieve specific benefits for the skin. In contrast, decomposition involves breaking down compounds into simpler substances, ionization pertains to the process of forming ions, and oxidation refers to the loss of electrons from a molecule, which can often occur in various chemical reactions but does not specifically pertain to the formation of new compounds through combination.