The question is incomplete, the complete question is;
Theresa creates an experiment where she mixes two red-colored substances together in a container and observes the solution slowly changing from red to blue for the next eight minutes. The solution becomes completely blue after eight minutes. What does this represent about the type of change happening in the container? A chemical change started immediately and finished at eight minutes. A non-chemical change started immediately and finished at eight minutes. A chemical change occurred at four minutes. A non-chemical change occurred at four minutes.
Answer:
A chemical change started immediately and finished at eight minutes.
Step-by-step explanation:
A chemical change is one in which a new substance is formed. One of the indicators that a chemical change has occurred is the change in the color of the system from red to blue.
The question clearly stated that the change occurred gradually. This means that the reaction must have started immediately the substances were mixed and went on to conclusion after eight minutes when the complete blue color appears.