PURE SUBSTANCES

PURE SUBSTANCES

1. PURE SUBSTANCE
A 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.
.

2. 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.

3. Types of Mixtures
Homogeneous 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.

4. Mixed salad

5. Homogeneous mixture:- milk , Soft drink

8. SOLUTION
A 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.

9. 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.
•

10. 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.

12. 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
-9
m 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.

13. 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)

14. 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.
•

15. 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.

16. Colloid
A 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.

18. CHARACTERISTICS OF
COLLOIDS
Colloidal solutions are translucent in nature.
The particle size is between 10
-7
cm and 10
-5
cm 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.

19. Passage of light through
solution,suspension and colloid.

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

22. Tyndall effect

23. JOHN TYNDALL
•HE WAS A BRITISH
PHYSICIST WHO
WAS AN AVID
PROMOTER OF
SCIENCE IN THE
VICTORIAN ERA.
•BORN IN 1920 IN
IRELAND.

26. 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.

27. Type of
colloid
Dispersion
medium
Dispersed
phase
Example
AEROSOL Gas LiquidFog , 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 SOLSolid Solid Coloured gems stone , Milky
glass
EMULSIONLiquid LiquidMilk , Face cream
GEL solid LiquidJelly , Cheese , Butter

28. AEROSOL Gas LiquidFog , Clouds ,Mist
clouds
mist
fog

29. AEROSOL Gas Solid Smoke , automobile exhaust
smoke
Car exhaust

30. FOAM Liquid Gas Shaving cream
Shaving cream
foam

31. FOAM solidGas Foam rubber, sponge
Foam rubber
sponge

32. SOLliquidSolidMilk of magnesia
Milk of
magnesia

33. SOLID
SOL
SolidSolidColoured gems stone ,
Milky glass
Gem
stones
Milky glass

34. EMULSIONLiquid LiquidMilk , Face cream
milk
Face cream
Emulsion paints

35. GEL solidLiquidJelly , Cheese , Butter
Jelly
Butter
Cheese

36. 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 rest
c) suspensions are clear
d) suspensions cannot be filtered

37. 2. An example of an emulsifying
agent would be__
a) oil
b) soap
c) water
d) salt

38. 3. An example of a homogeneous
mixture is___
a) sand and water
b) flour and water
c) salt dissolved in water
d) oil and water

39. 4. Which statement is not true.
a) particles in a colloid will reflect light
b) the particles of a solution are
molecular in size
c) a suspension can be filtered
d) a solution can be filtered

40. •5. An emulsion is always between___
a) Two solids
b) A solid and liquid
c) Two gases
d) Two liquids