1) in a chemical reaction, if a color change is detected, if an odor change is detected, or if a precipitate is formed, then: a. a chemical reaction has definitely occurred b. only physical reactions have occurred c. a chemical reaction may have occurred d. both physical and chemical reactions have definitely occurred 2) if different products are not created during a process, then a chemical reaction has not occurred. a. true b. false

1) C. a chemical reaction may have occurred

2) True

Explanation:

C. a chemical reaction may have occurred

In a chemical reaction new products are formed from the reactant molecules and these changes are accompanied by a precipitation formation or presence of odor and color change. For example, when H₂S gas is formed it smells f rotten eggs, chlorine gas formed is detected by its greenish yellow color, and different insoluble white or colored precipitates are clearly seen with the naked eyes.

True. In a chemical change there is rearrangement of atoms such that new products are formed from reactants.  

because natural gas is colorless, odorless, and tasteless, distributors add mercaptan (a chemical that smells like sulfur) to give natural gas a distinct unpleasant odor (it smells like rotten eggs). they locate the types of rock that are likely to contain natural gas deposits.