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Class 9, Science, Chapter-2, Lecture-2, Solution (Notes)

SOLUTION:

A homogeneous mixture (molecular dispersion) of two or more substances is termed as solution.
Solute: The substance which dissolves in another substance is called solute.
Solvent: The substance in which another substance dissolves is called solvent.

TYPES OF SOLUTIONS:

A. On the basis of solvent:

  1. Aqueous solution:
    Solutions obtained by dissolving solids in water are called aqueous solution.
  2. Non-aqueous solution:
    Solutions obtained by dissolving solids in liquids other than water such as alcohol, acetone etc are called non-aqueous solution.

B. On the basis of size of solute particles:

  • True solution:
    A homogeneous solution which contains soluble particles of size smaller than 10-7 cm is called a true solution.
    Example: solution of salt in water.
  • Colloidal solution:
    A heterogeneous solution which contains soluble particles of size between 10-7cm and
    10-5 cm is called a colloidal solution or COLLOID
    Example: Milk, Blood, Milk cream, Ink, Toothpaste, Gum solution, Soap solution.

Two phases of colloids:

  1. Dispersed particles:
    The small particles of size between 10-5cm and 10-7cm which are dissolved in a substance are called dispersed particles.
  2. Dispersion Medium:
    The substance in which the small particles of size between 10-5cm and 10-7cm are dissolved is called dispersion medium.
  • Suspensions:
    A heterogeneous solution which contains insoluble particles of size greater than 10-5cm is called a suspension. Example: Muddy water, Chalk powder in water, paints, Smoke in air.

C. On the basis of amount of solute particle:

  1. Saturated solution:
    A solution which cannot dissolve any more of solute at a given temperature and pressure is called saturated solution.
  2. Unsaturated solution:
    A solution which can dissolve more solute at a given temperature and pressure is called unsaturated solution.

D. On the basis of physical state of components:

  1. Solid-Solid solution: (Brass)
  2. Solid-Liquid solution: (Brine)
  3. Liquid-Liquid solution: (alcohol in water)
  4. Gas-Solid solution: (Hydrogen in Palladium metal)
  5. Gas-Liquid solution: (aerated water, cold drinks)
  6. Gas-Gas solution: (Air)

DIFFERENCES BETWEEN:

Property

True solution

Colloid

Suspension

1. Size of particles

Less than 10-7cm

Between 10-7cm and 10-5cm

Greater than 10-5cm

2. Nature

Homogeneous

Heterogeneous

Heterogeneous

3. Appearance

Transparent

Translucent

Opaque

4. Visibility

Invisible to naked eye Invisible under microscope

Invisible to naked eye

Visible under microscope

Visible to naked eye

5. Stability

Do not settle

Do not settle under gravity Settle by centrifugation

Settle under gravity

6. Filterability

Pass through filter paper Pass through parchment membrane

Pass through filter paper

Cannot pass through parchment membrane

Cannot pass through filter paper

7. Tyndall effect

Does not show Tyndall effect

Shows Tyndall effect

Does not show Tyndall effect

8. Brownian Movement

Shows no Brownian movement

Shows Brownian movement

Shows no Brownian movement.

9. Electrophoresis

Does not show electrophoresis

May Show electrophoresis

Does not show electrophoresis

Classification of Colloids:

Dispersed Phase

Dispersing Medium

Type

Examples

Solid

Solid

Solid Sol

Milky glass, Coloured gemstone

Liquid

Solid

Gel

Jelly, Cheese, Butter

Gas

Solid

Foam

Rubber, Sponge, Pumice

Solid

Liquid

Sol

Milk of magnesia, mud

Liquid

Liquid

Emulsion

Milk, face cream

Gas

Liquid

Foam

Shaving Cream

Solid

Gas

Aerosol

Smoke

Liquid

Gas

Aerosol

Fog, Clouds, Mist