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:
- Aqueous solution:
Solutions obtained by dissolving solids in water are called aqueous solution. - 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:
- Dispersed particles:
The small particles of size between 10-5cm and 10-7cm which are dissolved in a substance are called dispersed particles. - 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:
- Saturated solution:
A solution which cannot dissolve any more of solute at a given temperature and pressure is called saturated solution. - 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:
- Solid-Solid solution: (Brass)
- Solid-Liquid solution: (Brine)
- Liquid-Liquid solution: (alcohol in water)
- Gas-Solid solution: (Hydrogen in Palladium metal)
- Gas-Liquid solution: (aerated water, cold drinks)
- 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 |