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 (d)Digestion of food (e)Freezing of water (f)Burning of a candle

By BYJU'S Exam Prep

Updated on: September 25th, 2023

The chemical changes are (a) the Growth of a plant, (b) Rusting of iron, (d) the Cooking of food, (e) the Digestion of food, and (g) the Burning of a candle. When a substance undergoes a chemical transformation, a brand-new product is created while the substance’s molecular makeup is completely transformed. A physical change is one that affects a substance’s physical characteristics. It doesn’t produce a brand-new item. This kind of transformation is temporary and reversible.

Chemical Changes

(a) Growth of a plant

  • As new cells are created, a plant grows, which causes a chemical shift.
  • After growing, a plant can never revert to its original state.
  • So, a plant’s growth is a chemical alteration.

(b) Rusting of iron

  • Iron rusting is a chemical transformation.
  • Rust develops when the iron is exposed to oxygen and water.
  • Iron cannot be made from rust because it is a new product.
  • Iron rusting is a chemical change as a result.

(c) Mixing of iron fillings and sand

  • A physical change occurs when sand and iron fillings are combined.
  • A magnet can be used to remove iron fillings from the sand.
  • In this method, neither the iron’s nor the sand’s chemical composition is altered.
  • So, blending sand and iron fillings involves a physical change.

(d) Cooking food

  • Chemical changes occur during cooking.
  • The chemical makeup of the reactants changes during cooking.
  • After cooking, fresh items are created.
  • Food undergoes a chemical shift when it is cooked.

(e) Digestion of food

  • Food digestion is a chemical transformation.
  • Food is broken down into simpler compounds during digestion by the activity of enzymes.
  • Afterward, new items are created.
  • Consequently, food digestion involves a chemical change.

(f) Freezing of water

  • Water freezing is a physical transformation.
  • Water’s physical state transitions from liquid to solid during freezing.
  • Water’s chemical makeup does not alter when it freezes.
  • Water freezing is a physical change as a result.

(g) Burning of candle

  • A candle’s burning causes a chemical shift.
  • A candle burns by burning the wax, which emits carbon dioxide as it does so.
  • In the process, the candle’s molecular makeup is altered, and a new product is created.
  • As a result, burning a candle involves a chemical change.


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 (d)Digestion of food (e)Freezing of water (f)Burning of a candle

The chemical changes are (a) plant growth, (b) iron rusting, (d) cooking food, (e) food digestion, and (g) candle burning. The alteration is both permanent and irrevocable. A substance is said to undergo a chemical change when the chemical properties of a substance alter.

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