Introduction to Mixtures

📚 Key Concepts

🔹 What is a Mixture?

A mixture is formed when two or more substances are mixed together, where each substance retains its individual properties without undergoing any chemical change.

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Key Characteristics:

  • Components retain their original properties
  • No chemical reaction occurs between components
  • Components can be separated by physical methods
  • Composition may vary from sample to sample

🔹 Types of Mixtures

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1. Uniform Mixtures (Homogeneous)

  • Components are evenly distributed
  • Cannot distinguish individual components even with a microscope
  • Same composition throughout
  • Examples: Sugar water, air, salt water, alloys

2. Non-uniform Mixtures (Heterogeneous)

  • Components are not evenly distributed
  • Different components can be seen with naked eye or magnifying device
  • Composition varies from one part to another
  • Examples: Sand and water, oil and water, fruit salad, soil

🔹 Air as a Mixture

Air is a uniform mixture containing:

  • Nitrogen (78%) – Does not support combustion
  • Oxygen (21%) – Required for breathing and combustion
  • Argon (0.93%) – Noble gas
  • Carbon dioxide (0.04%) – Produced by respiration
  • Water vapour – Variable amount
  • Other gases – Trace amounts

🧪 Important Formulas and Tests

🔸 Lime Water Test for CO₂: Calcium hydroxide + Carbon dioxide → Calcium carbonate + Water Ca(OH)₂ + CO₂ → CaCO₃ + H₂O

🔸 Components can be identified by their properties