Final answer:
The observation that does not indicate a chemical reaction is 'Change in total mass of substances' as mass is conserved in according to the Law of Conservation of Mass in chemical reactions.
Step-by-step explanation:
The observation that does NOT indicate that a chemical reaction has occurred is d. Change in total mass of substances. During a chemical reaction, according to the Law of Conservation of Mass, the total mass of the reactants equals the total mass of the products, which means that mass should not change during a chemical reaction.
Other observations that usually indicate a chemical reaction include a. Formation of a precipitate, b. Production of a gas, and c. Evolution of energy. These changes provide evidence that new substances have been formed, which is characteristic of a chemical change.