CHEMISTRY
HOLIDAY
HOMEWORK
5 Types of Colloids
1. Aerosol
Dispersing medium Dispersed phase
Gas
Liquid
Name
Aerosol
Gas
Solid
Aerosol
A liquid or solid that is finely dispersed in a
gas, usually air, and is in a stable state is an
aerosol. A cloud is a natural aerosol of water
droplets in air. Smoke, which contains solid
particles of carbon and ash, combined with fog
and certain other chemicals is the harmful
aerosol called smog.
Fog is an aerosol.
Aerosol spray can.
Examples of aerosols include haze, dust,
particulate air pollutants and smoke.
2. Sol
Dispersing medium Dispersed phase Name
Liquid
Solid
Sol
A sol is a colloidal suspension of very
small solid particles in a continuous liquid medium.
Sols are quite stable and show the Tyndall effect.
Examples include blood, pigmented ink, cell fluids
and paint. Artificial sols may be prepared by
dispersion or condensation. Dispersion techniques
include grinding solids to colloidal dimensions
by ball milling and Bredig's arc method. The stability
of sols may be maintained by using dispersing
agents. Sols are commonly used in preparing solgels.
Mud is a sol.
Paint is a sol.
.
3. Foam
Dispersing medium Dispersed phase Name
Liquid
Gas
Foam
Foam is a colloid in which dispersed phase is
gas and dispersion medium is liquid. Common
.name is foam. Examples are soap lather,
whipped cream etc. Smaller bubbles in a mass
form the more usual foam. The colloidal
dimension in a foam is the thickness of the film,
not the size of the bubble.
When dispersed phase is gas and dispersion
medium is solid it is called solid foam.
E.g. foam rubber
When dispersed phase is gas and dispersion
medium is liquid it is called liquid foam.
E.g. whipped cream
Foam rubber is a solid
whipped cream is
Foam
liquid foam
4. Gel
Dispersing medium Dispersed phase Name
Solid
Liquid
Gel
A gel is a type of colloid in liquid is the
dispersed phase and solid is the dispersed
medium. Examples include jelly, cheese etc. It
forms a semi solid material. Gels are used as
culture media for microorganisms. Gels have
some curious properties. As they
age, syneresis may occur, which is the loss of
liquid. This is a result of the closer
agglomeration of the colloid. The reduced
active area requires less water, so the excess
water is eliminated. It does not mean that the
gel is deteriorating.
.
Jelly is a Gel
Cheese is a Gel
5. Emulsion
Dispersing medium Dispersed phase
Liquid
Liquid
Name
Emulsion
Emulsion is a type of colloid in which both
dispersion phase and dispersion medium are in
liquid state. Milk, face cream etc. are examples
of emulsions. If the liquids were miscible, they
would form a solution. The granules of an
emulsion may be large, even microscopic. An
emulsifying agent is usually required to form a
stable emulsion.

There are two types −

Oil dispersed in water (O/W type)

Water dispersed in oil (W/O type)
To find out whether an emulsion is oil-in-water or water-in-oil,
the effect of adding a small amount of either oil or water to a
sample of the emulsion on a microscope slide is observed.
Milk is an Emulsion.
Face cream is an Emulsion.