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

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.

Summary:

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.