What are Reversible change and Irreversible change?

Reversible Changes are those changes that can be reversed easily to form the 'original substance'.

Example- Ice is a solid substance. When we heat ice, it melts to form liquid water. When we freeze water it again forms ice.

Irreversible changes are those changes where materials cannot be changed back to their original form.

Example- burning of paper.

Once a piece of paper is burned, we cannot get back in the original form.