The change in which the shape , size, appearance or state of a subtance may alter but its chemical composition remains the same is called a physical change . In a physical change, no new substance is formed. Any change that involves the formation of a new substance and leads to a transformation of chemical identity is called a chemical change.
Chemical changes are usually accompanied with heat exchanges. Chemical changes are permanent changes which are usually irreversible.
Chemical changes are

Options

A. temporar, reversible and a new substance is produced
B. always accompanied by exchange of light
C. permanent, irreversible and a new substance is produced
D. never accompanied by exchange of light and heat energy.

Answer

c