Question

A small quantity of curd is added to warm milk. The milk is stirred and is set aside for few hours at a warm place. In a few hours, the curd is formed. This is an irreversible change because

• A. Sometimes curd can be reverted back to milk and sometimes not.
• B. Curd cannot be converted back to milk.
• C. Curd can be converted back to milk.
• D. No change is happening.

Answer 1

The correct option is B

Curd cannot be converted back to milk.

Irreversible changes are permanent changes that cannot be undone. The conversion of milk to curd involves a change from one material to another (i.e. from milk to curd) and this change cannot be undone. Hence, curdling of milk is an irreversible change.