Which of the following is the correct reason to justify that rusting of iron is a chemical change?

All of the above options are correct reasons to justify that rusting of iron is a chemical change.

In a chemical change, a new substance is formed, and rust is totally different from iron. Iron is an element while rust is the hydrated oxide of iron (Fe

2

O

3

. xH

2

O). Thus, the formation of rust is a chemical change.