Question

What are irreversible changes? Which of the two - the melting of ice and growth of a plant - is an irreversible change?

Answer 1

If a substance cannot be brought back to its original state after a change, it is said to be an irreversible change. Examples of irreversible changes are grinding wheat or corn into flour, cooking of food, rusting of iron, souring of milk, burning of candles or wood, ripening of fruits, and growing living organisms.
(1) Melting ice into water is a reversible change as water can be brought back to ice on cooling. That is why the melting of ice is not an irreversible change.
(2) On the other hand, the growth of a plant is an irreversible change as it cannot change itself.

Therefore, growth of a plant is an irreversible change.