Which of the following are chemical changes?
(a) Growth of a plant
(b) Rusting of iron
(c) Mixing of iron filings and sand
(d) Cooking of food
(e) Digestion of food
(f) Freezing of water
(g) Burning of a candle.

Growth of a plant, rusting of iron, cooking of food, digestion of food, burning of a candle are all chemical changes in which plant forms a newer version of itself as it grows in which it cannot return back to that same position, after rusting iron forms iron oxide which cannot be reversed back to iron, food is supplied with heat in which raw vegetables and spices get mixed and cannot be reversed back to their previous state, food after digestion cannot be formed and reversed back to that previous state, burning of candle is also irreversible as the wax of candle cannot be formed from the leftover as it got consumed during burning.

EXPLANATION

The change in which a new substance is formed is as called chemical change. In a chemical change, the substances that are involved change their identity and chemical composition to get converted into an entirely new substance.