Class 9 Science: Is Matter Around Us Pure

Recap of Previous Topics

• Classification of matter
• Importance and types of mixtures
• Solutions
  • Components of solutions
  • Concentrated vs. dilute solutions
  • Calculation of concentration
  • Mass percentage

Today's Topics

Suspensions

• Definition: A suspension is a heterogeneous mixture where the solute does not mix with the solvent.
• Example: Sand in water.
• Properties:
  • Heterogeneous mixture
  • Solute particles visible with naked eye
  • Solute can be easily separated from the solvent
  • Large solute particles scatter light, making the light's path visible
  • Particles settle at the bottom if the solution is undisturbed

Colloidal Solutions

• Definition: A heterogeneous mixture where solute particles are dispersed throughout the solvent.
• Example: Milk (colloidal solution - emulsion)
• Difference Between Types of Solutions:
  • Solution: Very small solute particles
  • Colloidal solution: Larger solute particles than in a solution
  • Suspension: Very big solute particles
• Terminology:
  • Solute: Dispersion phase
  • Solvent: Dispersion medium
• Types:
  • Sol: Solid dispersed in liquid (e.g., Paints)
  • Emulsion: Liquid dispersed in liquid (e.g., Milk)
• Properties:
  • Solute particles scatter a beam of light (Tyndall effect)
  • Solute particles move randomly in the solvent
  • Cannot be seen with the naked eye, seen under a microscope

Separation Techniques of Mixtures

Evaporation

• Purpose: Separate a volatile solute from a solvent
• Example: Separate dye from blue ink
• Process:
  • Heat the solution indirectly to evaporate the solvent (water) and leave behind the solute (dye)

Centrifugation

• Purpose: Separate components based on density
• Example: Separate cream from milk, separate blood components
• Process:
  • Churning or spinning to separate lighter particles from denser particles

Separating Funnel

• Purpose: Separate immiscible liquids
• Example: Separate water and kerosene
• Process:
  • Let the mixture stand and separate based on density, then drain the denser liquid

Sublimation

• Purpose: Separate a sublimable solid from a mixture
• Example: Separate ammonium chloride from salt
• Process:
  • Heat the mixture, allowing the sublimable component to vaporize and then condense elsewhere

Next Steps

• Study remaining 4 separation techniques
• Discuss elements, compounds, and their changes

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