Physical and Chemical Changes

Physical and Chemical Changes

• A change in which one or more new substances are formed is called a chemical change or chemical reaction.
• Chemical changes are very important in our daily lives, forming new substances as a result.
• Examples of chemical changes include:
  • Digestion of food in our body
  • Ripening of fruits
  • Fermentation of grapes
  • Production of medicines through a chain of chemical reactions
  • Formation of new materials like plastics and detergents through chemical reactions

Rusting of Iron

• Rusting is a chemical change that affects iron articles, slowly destroying them.
• Iron is used in making bridges, ships, cars, truck bodies, and many other articles, resulting in huge monetary losses due to rusting.

Anaerobic Bacteria and Biogas

• Anaerobic bacteria digest animal waste and produce biogas through a chemical change (Change – A).
• The biogas is then burnt as fuel, which is also a chemical change (Change – B).

Cooking Fuels and Chemical Changes

• Burning fuels for cooking is always accompanied by the production of heat.
• Explosion of a firework is a chemical change, producing heat, light, sound, and unpleasant gases that pollute the atmosphere.

Other Examples of Chemical Changes

• Neutralisation of an acid with a base is a chemical change.
• When food gets spoiled, it produces a foul smell, which is a chemical change.
• A slice of apple acquires a brown colour when not consumed immediately, which is due to the formation of new substances through a chemical change.

Learn about chemical changes and reactions, including examples of digestion, ripening, fermentation, and production of medicines and new materials.