Paheli mixed flour and water and (i) made a dough, (ii) rolled the dough to make a chapatti, (iii) baked the chapatti on a pan, (iv) dried the chapatti and ground it in a grinder to make powder. Identify the changes (i) to (iv) as the changes that can be reversed or that cannot be reversed.

The changes that can be reversed are

(I) Making a dough

(II) Rolling the dough to make a chapatti

In both these steps, there is change only in the physical state or form of the dough, which can be reversed.

The changes that cannot be reversed are:

(iii) baking the chapatti

(iv) drying and grinding the chapatti to make powder

As these steps involve a change in the chemical properties of dough, they cannot be reversed.