The document describes various methods for separating mixtures including filtration, evaporation, crystallization, distillation and chromatography. It provides details on using filtration to separate mixtures where one component is soluble in a solvent and the other is not. The document also explains that crystallization is the best method for obtaining pure samples when evaporation could result in decomposition.

1. 1.2 Methods of
a Describe methods of separations analysis
purification and and purification for the
) components of the following types of mixtures:
(i) solid-solid
(ii) solid-liquid
(iii) liquid-liquid (miscible and immiscible)
Done by: Chew Yun Jin (3)
3H/2011

2. Techniques to be covered for separations and purification include:
(i) Use of suitable solvent, filtration and crystallization
or evaporation
(ii) Sublimation
(iii) Distillation and fractional distillation
(iv) Use of a separating funnel
(v) Paper chromatography

3. Separating a Solid
from Solid. . .
Filtration
I t i s u s e d t o
s e p a r a t e o n e
s o l u b l e s o l i d a n d
a n o t h e r s o l i d .
Ho w d o we u s e f i l t r a t i o n t o
s e p a r a t e t wo s o l i d s ?
A mi x t u r e o f t w o s o l i d s c a n a l s o
b e s e p a r a t e d b y f i l t r a t i o n i f o n e
o f t h e m a r e s o l u b l e i n a s o l v e n t
b u t t h e o t h e r i s n o t . Fo r
e x a mp l e , a mi x t u r e o f s a l t a n d
s a n d c a n b e s e p a r a t e d b y
f i l t r a t i o n u s i n g wa t e r a s t h e

4. E x p e r i me n t 3
T o s e p a r a t e a mi x t u r e o f c o mmo n t a b l e s a l t
a n d s a n d
Pr o c e d u r e :
1) P o u r s o m e d i s t i l l e d w a t e r i n t o t h e
mi x t u r e o f c o mmo n t a b l e s a l t a n d s a n d .
S t i r a n d w a r m t h e mi x t u r e .
2) P o u r t h e w a r m m i x t u r e i n t o a f i l t e r
f u n n e l l i n e d wi t h f i l t e r p a p e r . Co l l e c t
t h e f i l t r a t e i n a c o n i c a l f l a s k (F i g . 3.14).
3) Wa s h t h e r e s i d u e w i t h a l i t t l e d i s t i l l e d
w a t e r t o r e mo v e a l l t h e s a l t s o l u t i o n
f r o m i t . Th e r e s i d u e i s s a n d .
4) P o u r t h e f i l t r a t e i n t o a n e v a p o r a t i n g
d i s h a n d e v a p o r a t e t h e f i l t r a t e t o
d r y n e s s (F i g . 3.15). T h e w h i t e s o l i d l e f t i n
t h e e v a p o r a t i n g d i s h i s s a l t .

5. A n o t h e r E x a mp l e :
To s e p a r a t e s a l t a n d
c h a l k p o wd e r
-D i s s o l v e t h e mi x t u r e u s i n g
d i s t i l l e d wa t e r .
-T h e s a l t w i l l d i s s o l v e i n
wa t e r wh i l e
t h e s a n d wi l l r e ma i n i n t h e
b e a k e r .
-T h e f i l t e r p a p e r o n l y a l l o ws
t h e
s o l u t i o n t o p a s s t h r o u g h .

6. Cr y s t a
l l i z a t
-C o l l e c t t h e
i t o an e a n d p l
f i l r t a c e
i t
i n t o a n
e v a p o r a t i n g d i s h .
-E v a p o r a t e t h e
wa t e r / s o l v e n t
u n t i l
t h e s o l u t i o n i s
s a t u r a t e d . (D o n o t
h e a t t o d r y n e s s )
-C o o l t h e s o l u t i o n
a n d c r y s t a l s wi l l

7. Separating a Solid
from a Liquid. . .
Decanting
The simplest way to separate the water from the
pebbles is to just pour the water away. This
method is called decanting (Fig 3.10) We use
decanting to separate a dense, insoluble solid
from a liquid. Decanting is carried out everyday
during many activities. For example during
cooking, water is poured off various cooked foods
by decanting.

8. Filtration
To separate sand from water, we use a
method known as filtration. In general,
we use filtration to separate small solid
particles from liquid. Examples of small
solid particles include sand, clay, dust
particles and precipitates (small solid
particles produced in a liquid by chemical
reactions)
How can we remove a precipitate from
a reaction mixture by filtration?
A white precipitate of lead (II) sulfate is
produced when we add sodium sulfate

10. A s o l i d c a n b e s e p a r a t e d f r o m a l i q u i d b y
f i l t r a t i o n b e c a u s e t h e f i l t e r p a p e r a c t s
a s a s i e v e . A l i q u i d c a n p a s s t h r o u g h t h e
p o r e s (s ma l l h o l e s ) o f t h e f i l t e r p a p e r b u t
a s o l i d c a n n o t d o s o .
Up o n f i l t r a t i o n , t h e s o l i d t h a t r e ma i n s o n
t h e f i l t e r p a p e r i s c a l l e d t h e r e s i due . Th e
l i q u i d o r s o l u t i o n t h a t p a s s e s t h r o u g h t h e
f i l t e r p a p e r i s c a l l e d t h e f i l t r a t e .

11. Evaporation to Dryness
and Crystallization
When a solid is insoluble in water, the easiest way to separate it from a liquid is by filtration.
However, many substances, like common salt, dissolve in water to form solutions. To
separate such substances, we evaporate water from the solution. This separation technique
is called evaporation to dryness. Fro example, when we evaporate salt solution to
dryness, we recover solid salt. This method can be used to recover salt from seawater.
However, many substances decompose when they are heated strongly. For example, sugar
will decompose to give water and carbon when it is heated strongly. Most crystals, such as
copper (II) sulfate crystals, give off water to become powders when heated. For such
substances, evaporation to dryness is nota good method of purification. Also, when all the
water is removed during evaporation, any soluble impurities present will be left on the
crystals.

12. The best method of obtaining a pure solid sample solution is called crystallization.
How do we purify by crystallization?
In crystallization, water is removed by heating the solution. Heating is stopped at the stage
when a hot saturated solution is formed. If the resulting solution is allowed to cool to room
temperature, the dissolved solid will be formed as pure crystals.
How do we test for a saturated solution?
A clean glass rod can be used to test whether a solution is saturated. It is dipped into the
solution and removed. There will be a small amount of solution on the rod. If small crystals
form on the rod as the solution cools, the solution is saturated. The solution is at its
saturation point or crystallization point.
Example: Obtaining copper (II) sulfate crystals from copper (II) sulfate solution
Flowchart below shows the steps involved.
Heat until the solution
Copper (II) sulfate is saturated Saturated copper (II)
solution sulfate solution
Allow solution to cool
Copper (II) sulfate
Copper (II) sulfate Filter the mixture crystals + solution
solution (contains soluble
impurities)

13. Websites for extra
information : & http://www.youtube.com/watch?v=aFONmzLQJSY

14. Done by:
Chew Yun Jin (3)
3H/2011
1)Chemistry Matters
(Marshall Cavendish)
textbook
2) www.chemcompass.pbwo
rks.com
3) www.google.com