why the cutting of paper is not a chemical change ???
Please note cutting of paper is a physical change. This physical change is irreversible in nature as we cannot join the two pieces of papers. It is not a chemical change as no new product is formed. The chemical composition of paper is same it before and after the event. Hence it cannot be termed as chemical change. I would advise you not to judge any reaction on the basis of reversibility of a process. If a process is irreversible it does not mean it is a chemical change. A large number of chemical changes are known which are reversible in nature and a large number of physical changes are known which are irreversible in nature. Therefore reversibility is not an appropriate criteria for judging a chemical and physical change.