Question

Melting of ice is reversible while curdling of milk is irreversible explain

Answer 1

As curdling of milk is a chemical change.
We know that chemical change can't be reversed.
Once the milk is converted into curd it can't be reversed into milk because, in the curd a bacteria known as "lactobacillus" is present which covert the milk into curd.
Once the bacteria start growing in the milk it can't be remove.

Answer 2

Melting of an ice cream changes the physical state of the ice cream. It can be brought back by freezing it and thus making it reversible. Curdling of the milk changes the chemical composition and we cannot get back the milk as it used to be hence being irreversible. Melting of an ice cream is a physical change while curdling of milk is a chemical change.