Question

what is chemical change

Answer 1

A chemical change that occurs when two or more substances combine to form a new substance.

For example: rusting of iron rod. when iron react with oxygen of air it forms iron oxide that it formed new compound.

When iron is exposed to water or air over a period of time, the iron reacts with oxygen in the presence of moisture to form a reddish-brown chemical compound, iron oxide. This is referred to as rust. So chemically, rust is hydrated iron(III) oxide or Fe2O3.nH2O.