can u define chemical change and rusting

A chemical change is the change in which:

new substances are formed.

the properties of new substances are different from the reactants.

heat and light may or may not be involved.

the change is irreversible.

Rusting is the chemical change in which iron reacts with the moisture and oxygen in the atmosphere to make iron oxide which is known as rust. The process of rusting requires both oxygen and water.It makes the iron weak. The ships have a lot of threats of rust. So a part of ship's iron is replaced every year.