Question

Is color change evidence that a chemical or physical change may have occurred?

Answer 1

Definitely, but it is not a good indicator of telling you which might have occured

Explanation:

Color change is a good way to tell that a change has occurred, and there's really nothing more to say about that. However, I would warn you against using color change as a firm identifier of either physical or chemical changes.

This is since there are examples of color change being an indicator for both of them. For instance, when you heat the blue copper(II) hydroxide solution, you'll eventually end up with a black copper oxide (`CuO`) solution. This is a verified chemical change. On the other hand, if you add red ink to water, it will turn red. However, we would classify that as a physical change.

To conclude, color change is a great indicator that change has occurred. However, it does not tell you which type of change might have occurred. You will want to use better indicators - like release of heat - to guide you with that.

Hope that helped :)