Give a detailed note on solution, suspension and colloid, mentioning all properties and types.
What are 3 important solutions, suspensions and colloids what are the basic criterias you follow to distinguish among them. Make a detailed note on each with examples and diagrammatic representation.

Dear student,

True solutions: A true solution is a homogeneous solution in which the solute particles have diameters between 0.1 nm to 1 nm i.e., the solute particles are of molecular dimensions. Such dispersed particles dissolve in solution to form a homogenous system. These do not settle down when the solution is left standing. The particles are invisible even under powerful microscopes and cannot be separated through filter paper, parchment paper, or animal membranes. For example, sodium chloride in water is a true solution. Most ionic compounds form true solutions in water. Organic compounds like sugar and urea also form true solutions in water.
 

Suspension: A suspension is a heterogeneous system in which the size of the solute particle is large (more than1000 nm). As a result, the solute particle does not dissolve in the solvent and settle down at the bottom in the solvent. Therefore the solute particles in a suspension can be easily seen with a naked eye. For example, a mixture of sand in water is a suspension. 

Colloid: A colloidal solution is a heterogeneous system in which one substance is dispersed (dispersed phase) as very fine particles in another substance called dispersion medium. It is the intermediate system between a solution and a suspension. The size of colloidal particles is between 1 nm and 1000 nm. The colloidal particles remain suspended in the medium. Example milk, ink, etc.

 

Property	True solution	Suspension	Colloids
1. Nature	Homogenous	Heterogeneous	Heterogeneous
2. Size	Less than 1nm	More than 1000nm	b/w 1-1000nm
3. Sedimentation	Don’t settle down	Settle down	Don’t settle down
4. Filtration	Can’t be filtered	Can be filtered	Can’t be filtered by normal filter paper, require special filter papers like the parchment paper
5. Tyndall effect	Don’t show	show	show
6. Seen with naked eyes	Can’t be seen	Can be seen	Can’t be seen
7. Examples	Brine, sugar + water	Clay + water, Sand + water	Milk, paint

There are 9 types of solutions, based on the solute and the solvent. Please find below the types of solutions listed along with examples.
 

solute	Solvent	Examples
Gas	Gas	Air
Gas	Liquid	Soda water
Gas	Solid	Hydrogen in Pt
Liquid	Gas	Water vapour in air
Liquid	Liquid	Alcohol in water
Liquid	Liquid	Silver amalgam
Solid	Gas	Sulfur vapour in air
Solid	Liquid	Sugar in water
Solid	Solid	Brass

 
Suspensions are not further classified.
 

Colloids are classified depending upon the following three criteria:

• The physical state of the dispersed phase and the dispersion medium
• Nature of interaction between the dispersed phase and the dispersion medium
• Type of particles of the dispersed phase

Depending Upon the   physical state of Dispersed Phase and Dispersion Medium

Dispersed phase	Dispersion medium	Type of colloid	Example
Solid	Solid	Solid sol	Gem stones, some coloured glasses
Solid	Liquid	Sol	Paints, cell fluids
Solid	Gas	Aerosol	Smoke, dust
Liquid	Solid	Gel	Cheese, butter, jellies
Liquid	Liquid	Emulsion	Milk, hair cream
Liquid	Gas	Aerosol	Fog, mist, cloud
Gas	Solid	Solid sol	Pumice stone, foam, rubber
Gas	Liquid	Foam	Froth, soap lather

II Depending Upon the Nature of Interaction between Dispersed Phase and Dispersion Medium

• Lyophilic colloids   (solvent attracting)

  • Also called reversible sols

  • Quite stable and cannot be easily coagulated

• Lyophobic colloids   (solvent repelling)

  • Also called irreversible sols

  • Unstable and can be easily coagulated

III Depending Upon the Type of Particles of the Dispersed Phase

• Multi-molecular colloids   − Species having a size in the colloidal range(diameter   < 1 nm)

• Macromolecular colloids   − Macromolecules (such as starch, cellulose, proteins, enzymes, etc.) in suitable solvents form solutions in which the size of the macromolecules may be in the colloidal range.

• Associated colloids (Micelles)   − Some substances at low concentration behave as normal electrolytes, but at higher concentrations exhibit colloidal behaviour due to the formation of aggregates. The aggregated particles are called micelles and are also known as associated colloids.

  • The temperature above which the formation of micelles takes place is called Kraft temperature ( T _k ).

  • The concentration above which the formation of micelles takes place is called critical micelle concentration (CMC).

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