Chemical transformation or change; the interaction of chemical entities.

• A. Chemical Indicator
• B. Dehydration Synthesis
• C. Covalent Bond
• D. Chemical Reaction

Answer: (D)

A chemical reaction is the process where chemical entities interact and undergo a transformation, meaning the original substances (reactants) are converted into new substances (products) through breaking and forming chemical bonds. This encompasses changes in the arrangement of atoms and often energy exchange, reflecting a true transformation of matter rather than just a static connection. A covalent bond, by contrast, is simply a type of bond that holds atoms together, not the overall process of change. Dehydration synthesis is a specific kind of chemical reaction that forms a new covalent bond with water removed, but the concept here is broader—the idea of substances reacting to become different substances. A chemical indicator shows that a change has occurred, not the change itself.