Differentiate among the changes such as folding of paper, tearing of paper and burning of paper.
Paper is a material which are produced in the form of thin sheets from wood pulp or other fibrous materials, and is used for wrapping, printing or writing etc.
It can be folded into 6 to 7 times. On unfolding the paper, it regained its original shape and size. Thus, only change in physical property was noticed and no new substance is formed. Hence, these are physical changes.
The pieces of paper can be joined with the help of glue. However, one cannot get the paper in its original form. Thus, only change in physical property was noticed and no new substance is formed. Hence, these are physical changes.
They turned black, whereas original paper pieces were white in colour. Smoke was also observed during burning of the paper pieces. Thus, new substances are formed. Hence, it is a chemical change.
In Burning of paper ash is formed in the process which is new compound and oxides of carbon are also released during the process. By the definition of chemical change, we come to know that during chemical change a new substance must form. These changes are irreversible in nature.