Question

How can you say that curding of milk is chemical change and melting of ice is physical change

Answer 1

cutting of milk is irreversible change as the curdled milk cannot be changed back again to milk whereas melted ice can be changed back into ice again it is a reversible change
one of the property states that chemical changes are Irreversible changes and physical changes are reversible changes

Answer 2

Curd can't change again into milk. And ice can be freeze again