Out of the options, the best indicator is a color change since it is the only one that can't really be blamed on a physical change. you will eventually notice that during qualitative labs and some quantitative labs, usually the thing that you are looking for is either color change or the production of a precipitate to indicate the presence of a chemical reaction
The correct answer is 2) change of color
Explanation:
A chemical change occurs when a new substance is formed or the original substance changes its identity and composition due to a chemical reaction. This is the opposite of a physical change that modifies only physical properties such as state or shape. Moreover, a chemical reaction can be identified because if often leads to a change in color, odor, the formation of bubbles or temperature change. This implies the only one that suggests a chemical change is a change of color because this occurs if the composition of a substance or substances change.
