I
• I
(i) p
(ii) owder the solids, if needed, by using a pestle and mortar.
(iii) As a suspe~sion i~ unstable in nature, stir the suspension thoroughly before each test.
If any foreign article, like a stone, is detected in the given sample, remove it before grinding.
EXPERIMENT l(C)
~ IM OF THE EXPERIMENT
To ~ak~ colloidal solutions of (i) starch and (ii) albumin (say egg albumin) in water and study their
properties like (a) transparency (b) filtration critertion and (c) stability.
HEORY
. To obtain a colloidal solution of starch in water, make a thin paste of ordinary starch (maida or c fl )
m cold water. Add this paste to boiling water, with constant stirring, to get colloidal solution of starcho~n ~ur
Egg albumin is the scientific name for white of an egg. Dissolve nearly a spoonful of egg white in 100-: ~e~f
cold water. Use only cold water to get a colloidal solution of egg albumin in water. This is because hot water will
coagulate the egg white.
A colloidal solution is generally translucent i.e. , it appears milky or cloudy.
When filtered through an ordinary filter paper, a colloidal solution passes through the filter paper unchanged
i.e. , no residue is obtained on the filter paper and the filtrate is translucent as the original solution. This is
because the size of the colloidal particles is between 1-1000 nm, which is less than the size of pores of an
ordinary filter paper.
A colloidal solution is stable i.e., colloidal particles do not settle down if a colloidal solution is left
undisturbed for sometime.
PPARATUS AND MATERIALS REQUIRED
Beakers, test tubes, test tube stand, glass rod, filter paper, funnel, funnel stand, burner, starch (maida) or
com flour, egg albumin (or egg white), distilled water etc.
ROCEDURE
1. Take nearly 2 g (or one teaspoon) of ordinary starch. Make a thin paste of this starch with nearly 10 mL
of cold water. Heat nearly 100 mL of water in a 250 mL beaker to boiling. Add the paste of starch in
water to boiling water, in a thin stream, with constant stirring. Boil this solution for 2-3 minutes and let
it cool. Label it as colloidal solution of starch in water.
2. Break an egg carefully so that the whites of the egg and egg yolk do not mix. Carefully separate the two.
Dissolve a spoonful of the egg whites in nearly 100 mL of water in a 250 mL beaker. Label it as a'
colloidal solution of egg albumin in water.
3. Put these two colloidal solutions in two clean test tubes and view through them. Note down your
observations in the note book.
4. Filter the two colloidal solutions through ordinary filter papers. Note if any residue is obtained on the
filter paper. Note the appearance of the filtrate. Note down your observations in the note book.
5. Again, take the two colloidal solutions in two clean test tubes. Put these test tubes in a test tube-stand
undisturbed for some time. Note down if any solid .settles down or if there is any change in the
appearance of the two solutions. Note down your observations in the note book.
BSERVATIONS
tJ S.No.
1.
Test
Test for
transparency
Translucent
Starch in water
Colloidal solution of
Translucent
Albumin in water
2. Filtration criterion Passes through an ordinary fi lter paper Passes through an ordinary filter paper
unchanged. unchanged .
3. Stability Stable as no solid settles down. Stable as no solid settles down.
. IX
~~-
y
LT AND DISC USSIO N
RESU . f
(I.) A suspension o stareI1 111
. .
water, when boiled .
tor some 11· 111 , 1· . .
. . . •
C 0 1lllS a Cll 11 llll1:I 1 SU1UIIIJII.
(ii} Egg albumm n~ cold water forms a colloid al solution. ·
(iii) Collo!dal solut~ons are translucent in n~ture. .
(iv) Collo~dal solut~ons pass through an or~mary filter paper
unchan ged.
(v) Col101dal solutions are stable as no sohds settle down with
time .
PRECAUTIONS .
(i) Use only cold water to get colloidal solution of egg album
in in water .
(ii) Starch with _c~ld water forms a suspensi?n. Boil it to get
a colloidal solution.
(iii) Use only d1slllled water to make col101dal solutions.
This is because presence or ions gene rally
destabilises colloidal solutions.
EXPERIMENT l(D)
AIM OF THE EXPE RIME NT
To distinguish between a true solution, a suspension and a colloid
al solution on the basis of
(i) transp arenc y
(ii) filtration criteri on
(iii) stability.
THEORY
A true solution, a suspension and a colloidal solution can be differe
ntiated on the basis of transparency ,
filterabi)ity and stability.
A true solution is always transparent . A suspension is opaque while
a colloidal solution is translucent. To
check transparency, take the three mixrures (i.e., true solution.
colloidal solution and suspension) in three
identical test tubes and view through them.
On filtration through an ordinary filter paper, a true solution and
a colloidal solution pass through the filter
paper unchanged . However. when a suspension is -filtered throug
h a filter paper, the suspended particles are
retained on the filter paper. This is because the size of these particl
es is more than the pore size of filter paper.
In terms of stabilit y, a true solut ion and a colloidal solution are stable
i.e., they do not settle down. On the
other hand , a suspension settles down. if left undistu rbed.
APPARATUS AND MATE RIALS REQU IRED
100 mL beakers (3 nos .), test tubes, test tube stand, glass rod,
funnel , funnel stand, burner , filter paper,
common salt (or sugar or alum), soil (or chalk powder or fi ne sand),
starch (or egg albumin). distilled water.
PROCEDURE
1. Take 100 mL beaker , half ful l of water. Add some powdered
common salt (or sugar) to it. Stir well with
a glass rod till whole of the salt dissolves. This is a true solutio n
of salt in water. Alternatively prepare
a true solutio n of alum in water but add a few drops of cone. H2SO.
i to make it clear.
2. Take another 100 mL beaker , half fu ll of water. Add to it some
fine sand (or chalk powder or soil). Stir
it well with a glass rod. A suspension of fine sand in water is obtain
ed .
3. Take anothe r JOO mL beaker half full of water. Heat the
water till it starts boiling. Now add a
SUSflension of starch in water 10 it with constant stirring. Boil it
fo r 2 - 3 minutes. This is a eolloidal
solution of starch in water. To obtain colloidal solution of egg album
in in water, sha ke some egg albumin
with cold water.
4. Test for transparency . Take the true solutio n in a test tube
and label it as A. Take the s11spc11sio1_1 in
another similar test tube. Shake it will and label it as B. In anothe
r similar test lube take 1hc collo1du l
solution and label it as c. Put the three test tubes in a test tube-s
tand and view through them. Record
your observations (transparent , opaqu e or translucent) in your note-b
ook .
5. Filtration criterion. Filter the true solution through a filter paper. Note if there is any residu
. . eon lhe
filter paper. Also check, If there IS any change in appearance of the filtrate . Note your observatio ,. .
• "} 11,, 11\
the note-book. In a s1m1 ar manner filter the suspension through a filter paper and note your observatiu
.m the note-book. s·Im1·1 arly filter the colloidal solution through a filter paper and record your observation,.
II~
in the note-book.
6. Stability. Take 10 mL of each of the three mixtures in three different test tubes. Leave them undisturhed
for a few minutes (5-10 minutes). Is the mixture stable or do the particles begin to settle down after
some time ? Record your observations in the note book.
~Filter ~Filter Filter
True
solution
Suspension Coloidal
solution
V paper '\.£
paper paper
Funnel Funnel ' Funnel
• True solution Suspension
Colloidal solution --
Fig. 1.4. Test for filtrabt 11ty
Fig. 1.3. Test for transparency
O BSERVATIONS
Suspension of fme sand Colloidal solution of
S.No. Test Solution of common salt starch in water
in water in water
(Test tube B) (Test tube C)
(fest tube A)
Transparent Opaque Translucent
1. Test for
transparency
Passes through a filter Fine sand particles. are Passes through a filter
2. Filtration criterion paper unchanged retained by th e f d t~r paper unchanged
paper while the filtrate 1s
clear water
Stable Uns ta bl e fine sand Stable
3. Stability particles settle down with
time .
R ESULT AND DISCUSSION · · ent
· (
(i) Common salt or sugar,
or alum) and water .forms a .true solution. A true solution 1s transpar •
asses through a filter paper unchanged and is stable m nature. . . assed
(ii)
p•
~::u;~n: i ~:e;~::~.r,
or soil) and water forms a suspension. A suspension 1s opaque, when P .
the sand particles are retained by the filter paper. A suspension is unstable 10
nature. . . • t slucent passes
(iii) Starch (or albumin) and water form a colloidal sol ution. A col101da 1 so1ut1o n 1s ran ·
through a filter paper unchanged and is stable in nature.
P RECAUTIONS
(i) Use only distilled water.
(ii) Use only cold water to prepare colloidal solution of albumin in water.
(iii) To obtain colloidal solution of starch in water, boil a suspension of starch in water.
(iv) Shake the suspension vigorously before checking it for transparency .
