(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.