Final answer:
A change in 'state' signifies a physical change and is not evidence of a chemical change, which can be identified by color change, the appearance of a new odour, or the formation of a gas.
Step-by-step explanation:
When identifying whether a substance has undergone a chemical change, several pieces of evidence can be used, except for the 'state' of the substance. A change in 'state' is indicative of a physical change, such as the transition of water (H₂O) from liquid to gas without altering its molecular structure. On the other hand, chemical changes may include observable evidence such as a color change, the emergence of a new odour, or the formation of a gas that occurs at the temperature of the beginning materials, instead of a change to a liquid state.
Thus, for the question presented, all options—color (A), odour (B), and formation of a gas (D)—can be evidence of a chemical change, with the exception of 'state' (C), which typically represents a physical change. To summarize, the evidence used to identify a chemical change includes unexpected color changes, a new or different odour, the production of heat or light, bubbles forming when not boiling, or the formation of a precipitate.