Answer:
See explanation
Step-by-step explanation:
What has happened to the nail is a typical example of a chemical change. In a chemical change, a new substance is formed, heat is released and it is not easily reversible.
The nail has undergone chemical change because it no longer conducts heat as it used to. This shows that the chemical composition of the nail has changed.
Also, the change in the physical appearance of the nail from a shinning metal to reddish brown indicates that a chemical change has occurred.