IntroductionMost of the substances around us undergo changes. Some of these changes can be temporary, with no new substances being formed. They are called physical changes. In certain other changes, new substances are formed and the parent substance loses its identity. In such changes, we cannot get back the original substances from the new substance by simple means. They are called permanent changes.
Example : Burning of paper to yield carbon. When paper is burnt, black particles of carbon (ash) is formed. It is not possible to get back paper from it. This is a permanent chemical change.