Exploring Mixtures and Their Separations Class 9 Chemistry

 

📘 Chapter 1: Exploring Mixtures and Their Separations

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🔹 1.0 Introduction

• Everything around us is made of matter.
• Matter can be classified into:
  • Pure substances
  • Mixtures

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🔹 1.1 Mixtures

• A mixture is formed by combining two or more substances physically.

🔸 1.1.1 Characteristics of Mixture

• No fixed composition
• Components retain their properties
• Can be separated by physical methods
• No new substance formed

🔸 1.1.2 Classification of Mixtures

1. Homogeneous Mixture (Uniform)
   • Example: Salt solution
2. Heterogeneous Mixture (Non-uniform)
   • Example: Sand + water

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🔹 1.2 Solutions

• A solution is a homogeneous mixture.

Components:

• Solute → Substance dissolved
• Solvent → Substance that dissolves solute

🔸 1.2.1 Types of Solutions

• Solid in liquid (Salt in water)
• Liquid in liquid (Alcohol in water)
• Gas in liquid (CO₂ in water)

🔸 1.2.2 Properties of Solutions

• Transparent
• Do not scatter light
• Stable (no settling)
• Cannot be filtered

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🔹 1.3 Concentration of Solutions

• Amount of solute in a solution.

Ways to express concentration:

• Mass by mass %
• Volume by volume %
• Mass by volume %

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🔸 1.3.1 Saturated & Unsaturated Solutions

• Saturated → No more solute can dissolve
• Unsaturated → More solute can dissolve

🔸 1.3.2 Supersaturated Solution

• Contains more solute than saturated solution
• Unstable

🔸 1.3.3 Solubility

• Maximum amount of solute that dissolves in solvent at a given temperature

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🔹 1.4 Suspension

• A heterogeneous mixture with visible particles.

🔸 Properties:

• Particles settle down
• Can be filtered
• Scatter light

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🔹 1.5 Colloids

• Intermediate between solution and suspension.

🔸 1.5.1 Terms

• Dispersed phase → particles
• Dispersion medium → medium

🔸 1.5.2 Properties

• Show Tyndall effect (scatter light)
• Stable
• Cannot be filtered
  
  
  
  
  
  

🔹 1.6 Separation of Mixtures

Common Methods:

• Filtration → Separate solid from liquid
• Evaporation → Remove solvent
• Distillation → Separate liquids
• Decantation → Pour off liquid
• Chromatography → Separate colours
• Magnetic separation → Magnetic substances

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📝 MCQ QUESTIONS (Topic-wise)

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🔸 Mixtures

1. A mixture is:
   a) Chemically combined
   b) Physically combined
   c) Pure substance
   d) Element
2. Which is homogeneous?
   a) Sand + water
   b) Oil + water
   c) Salt solution
   d) Soil

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🔸 Solutions

3. The solvent is:
   a) Dissolved substance
   b) Dissolving medium
   c) Gas
   d) Solid
4. Which is a true solution?
   a) Milk
   b) Muddy water
   c) Sugar in water
   d) Chalk in water

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🔸 Concentration

5. Saturated solution means:
   a) Less solute
   b) No solute
   c) Maximum solute dissolved
   d) More solvent
6. Supersaturated solution is:
   a) Stable
   b) Unstable
   c) Gas
   d) Solid

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🔸 Suspension

7. Suspension is:
   a) Homogeneous
   b) Pure
   c) Heterogeneous
   d) Element
8. Suspension particles:
   a) Do not settle
   b) Settle down
   c) Invisible
   d) Dissolve

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🔸 Colloids

9. Colloids show:
   a) Reflection
   b) Refraction
   c) Tyndall effect
   d) Gravity
10. Example of colloid:
    a) Salt solution
    b) Milk
    c) Sugar solution
    d) Air

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🔸 Separation Techniques

11. Filtration is used for:
    a) Liquid-liquid
    b) Solid-liquid
    c) Gas-liquid
    d) Gas-solid
12. Evaporation is used to:
    a) Remove solute
    b) Remove solvent
    c) Add water
    d) Cool solution
    
     ✅ ANSWER KEY
    
    

    1  -  b  
    2  -  c  
    3  -  b  
    4  -  c  
    5  -  c  
    6  -  b  
    7  -  c  
    8  -  b  
    9  -  c  
    10 -  b  
    11 -  b  
    12 -  b