Question

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

Answer 1

Hint: In a chemical change, there is a change in the composition of the substances in question; in a physical change are limited to a change in their texture, color, temperature or shape. Color change is also an indicator of a chemical change.

Complete answer:
Chemical changes occur when the substance’s composition is changed. When bonds are broken and new ones are formed a chemical change occurs. When two or more reactants are mixed and a change in temperature, color, etc. is noticed, a chemical change is probably occurring. A change in color is not always a chemical change. If one were to change the color of a substance in a non-chemical reaction scenario, such as painting a car is a physical change not a chemical change.
Color change is a characteristic of a chemical reaction taking place. For example, if one were to observe the rusting of iron over time, one would realize that the metal has changed color and turned orange. This change in color is evidence of a chemical reaction. However, sometimes a change in color is simply a mixing of two colors, but no real change in the composition of the substance in question.
For example: when we heat the blue copper (II) hydroxide solution, you will eventually end up with a black copper oxide solution \[CuO\]. 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.

Note:
Color change is a great indicator that change has occurred. However, it does not tell us which type of change might have occurred. We will need a better indicator to differentiate between physical change and chemical change. For example: for a physical change we can use the indicator of change in state, and in chemical change we can use the change in temperature as an indicator.