What evidence of a chemical reaction might you see in the following cases?
* bleaching a stain
* burning a match.
*rusting of an iron nail

In bleaching a stain, you see that the stain fades, and doesn't come back, which indicates that it has undergone a change. 

Buring a match, you would see the ashes, and that it cannot be it's original substance again. 

In rusting of an iron nail, the nail cannot be unrusted easily, which indicates that it has been through a chemical reaction.