Sean's bike begins to rust in the winter. what tells Sean that a chemical change is happening?

The metal is beginning to rust

Explanation:

Because when it is out side a small layer of condensation begins to form which the turns to rust as it is outside colliding with the cold air

the cellphone, they would then know if the killer would have contacted them or always hated them. or if it was a breakup. but if that is not the case, then it would be the clothing. to put in a bullet, it would have to be put in by hands. hands have finger prints which, would have giving you the answer of who done it.

explanation:

this is a good question! i'll do some research and come back when i have the answer!