Which of the following come under the category of chemical change? 

A. Growth of plant

B. Rusting of iron

C. Mixing of iron fillings and sand

D. Freezing of water

E. None of the above

Choose the most appropriate answer from the options given below:

The correct answer is B only.

Key Points

• Rusting of iron is a chemical change as it involves the formation of a new substance, iron oxide, which is different from the original material.
• Chemical changes result in the production of one or more new substances with different properties from the original substances.
• During rusting, iron reacts with oxygen and moisture in the environment, leading to corrosion.
• This process is irreversible under normal conditions, further confirming it as a chemical change.

Additional Information

• Physical vs Chemical Change
  • Physical changes affect the form of a chemical substance but not its chemical composition (e.g., melting ice).
  • Chemical changes involve making or breaking of bonds between atoms, resulting in new substances (e.g., burning wood).
• Indicators of Chemical Changes
  • Change in color, temperature, formation of a precipitate, and evolution of gas are common indicators.
  • Production of light or sound can also indicate a chemical change.
• Examples of Chemical Changes
  • Burning of paper, digestion of food, and baking a cake are classic examples.
  • These processes produce new substances with different properties from the reactants.
• Importance of Understanding Chemical Changes
  • Helps in various industries such as pharmaceuticals, agriculture, and manufacturing.
  • Understanding these changes is crucial in environmental science to address issues like pollution and recycling.