PURE SUBSTANCEA homogeneous material which contains particles (atoms or molecules ) of only one

kind and has a definite set of properties( melting point , boiling point) and which cannot be separated into other kinds

of matter by any physical process.

eg:-Elements : Metals and Non-metals , Compounds : Salts.

.

MIXTURE

When two or more substances (elements ,compounds or both) are mixed together in any proportion, such that they do not undergo any chemical change but retain their individual characteristics , the resulting product is a mixture.

Types of MixturesHomogeneous mixture:- A mixture in which different constituents are mixed uniformly and there are no specific boundaries seen between the particles of the mixture is called a Homogeneous mixture.Eg: Solutions such as common salt in water , sugar in water etc are homogeneous mixtures .Similarly alloys such as brass, bronze, etc. are homogeneous solid -solid solutions of metals.

Heterogeneous mixture:- A mixture in which different constituents are not mixed uniformly and there are specific boundaries seen between the particles of the mixture is called a heterogeneous mixture .Eg: Mixture of sand and salt, iron and sulphur powder, soil etc are egs. of such mixtures.

Mixed salad

Homogeneous mixture:- milk , Soft drink

SOLUTIONA homogeneous mixture of two or more substances is called a solution . A true solution is one which the particles of the solute are broken down to such a fine state( molecular level) that they

cannot be seen under a powerful microscope.

SOLUTIONS• When the 2 substances totally mix it is called a solution.• E.g. Solute + Solvent = Solution • (sugar) + (water) = Solution • • • We then say sugar is soluble in water, it has dissolved. •

Components of a solution

Solvent:-the component which dissolves the other component in itself. Usually it is the larger component.

Examples :-water in a solution of water and copper suphate, turpentine oil in paints.

Solute:-Component which dissolves in the solvent. Usually it is the smaller component.

Examples:-Salt in a solution of salt and water, Carbon dioxide gas in carbonated drinks.

CHARACTERISTICS OF SOLUTIONS

A true solution is always clear and transparent.It is homogeneous in nature.The solute particles break down to almost

molecular size (Diameter=10-9m or 1nm).It is stable and solute particles do not separate

or settle down on standing.It cannot be separated by filtration.Solute can be recovered by evaporation or

crystallization methods.

SUSPENSIONS

• A heterogeneous mixture of in solution particles of solute , spread throughout a solvent is called a suspension.

• Eg: Muddy water, slaked-lime suspension (used for white washing), white paints (particles of dye suspended in turpentine oil)

SUSPENSIONS• Suspensions• Sometimes when we mix substances they stay in clusters. We

therefore say it is insoluble in water.• E.g. Chalk + Water = Suspension• • Eventually the particles sink to the bottom to form sediment. •

Characteristics of suspensions

It is opaque and does not allow light to pass through it.

Particle size is more than 10-5 cm in diameter. It is heterogeneous in nature. It is unstable and the suspension particles settle

down when allowed to stand undisturbed. Particles can be separated by filtration method

from the solvent.

ColloidA heterogeneous solution in which particle size is between 10-7 cm to 10 5 ‑ in diameter, such that the solute particles neither dissolve nor settle down in a solvent is called a colloidal solution.eg. jelly, mist, soap solution, blood.

CHARACTERISTICS OF COLLOIDS

Colloidal solutions are translucent in nature.The particle size is between 10-7cm and 10-5cm in

diameter.They are heterogeneous in nature (but appear to

be homogeneous).They are stable and solute particles do not

separate on standing.The particles cannot be separated by filtration

method.Particles can be separated by centrifugation

method.

Passage of light through solution,suspension and colloid.

TYNDALL EFFECT

The phenomenon due to which the path of light becomes visible, due to scattering of light by the colloidal particles.

Tyndall e

ffect

JOHN TYNDALL

• HE WAS A BRITISH PHYSICIST WHO WAS AN AVID PROMOTER OF SCIENCE IN THE VICTORIAN ERA.

• BORN IN 1920 IN IRELAND.

Dispersing medium (external phase) - the constituent found in the greater extent in the colloid. Dispersed phase (internal phase) - the constituent found in the lesser extent. If water is the dispersing medium, it is often known as a hydrosol.

Type of colloid

Dispersion medium

Dispersed phase

Example

AEROSOL Gas Liquid Fog , Clouds ,Mist

AEROSOL Gas Solid Smoke , automobile exhaust

FOAM Liquid Gas Shaving cream

FOAM solid Gas Foam rubber, sponge

SOL liquid Solid Milk of magnesia

SOLID SOL Solid Solid Coloured gems stone , Milky glass

EMULSION Liquid Liquid Milk , Face cream

GEL solid Liquid Jelly , Cheese , Butter

AEROSOL Gas Liquid Fog , Clouds ,Mist

clouds mist

fog

AEROSOL Gas Solid Smoke , automobile exhaust

smoke Car exhaust

FOAM Liquid Gas Shaving cream

Shaving cream

foam

FOAM solid Gas Foam rubber, sponge

Foam rubber

sponge

SOL liquid Solid Milk of magnesia

Milk of magnesia

SOLID SOL

Solid Solid Coloured gems stone , Milky glass

Gem stones

Milky glass

EMULSION Liquid Liquid Milk , Face cream

milk

Face cream

Emulsion paints

GEL solid Liquid Jelly , Cheese , Butter

Jelly

Butter

Cheese

Assessment Questions:

• Multiple Choice Questions• 1. What factor distinguishes a

suspension from a colloid?a) light reflects off the particles of a suspension b) the particles of a suspension will sink out if left over time to restc) suspensions are cleard) suspensions cannot be filtered

2. An example of an emulsifying agent would be__a) oilb) soapc) waterd) salt

3. An example of a homogeneous mixture is___a) sand and waterb) flour and waterc) salt dissolved in waterd) oil and water

4. Which statement is not true.a) particles in a colloid will reflect lightb) the particles of a solution are molecular in sizec) a suspension can be filteredd) a solution can be filtered

• 5. An emulsion is always between___a) Two solids b) A solid and liquidc) Two gasesd) Two liquids