Question

Why curdling of milk is an irreversible change?

Answer 1

Formation of curd from milk is an irreversible change because the product so obtained can't be changed to it's original form . Once changed into curd , we can't change it back to milk. Thus, it's an irreversible change.

Answer 2

Due to the lactobacillus bacteria  the curd formation takes place . Its formaion is irreversable & a chemical change because once the curd is formed , we cannot seperate the substances from it .