1. which of these is an indication that a chemical reaction has occurred? a. formation of a precipitate b. melting of a substance c. boiling of a substance d. freezing of a substance 2. if decreases in temperature accompanies a reaction, what occurred? a. energy was destroyed b. energy was created c. energy was absorbed d. energy was released 3. which of these accurately describes the products of a reaction? a. new substances that are present at the end of a reaction b. substances that were not used up in a reaction c. substances that are used in a reaction d. substances that do not participate in a reaction 4. which of these describes an exothermic reaction? a. energy is released by the reaction b. energy is created in the reaction c. energy is absorbed by the reaction d. no energy is transferred by the reaction 5. what occurs in a chemical reaction a. reactants are formed without chemical bonds being broken b. reactants are formed from products by the breaking and forming of bonds c. products are formed without chemical bonds being broken d. products are formed reactants by the breaking and forming of new bonds.