Colloid Properties: Brownian movement (Part - 24) - Surface Chemistry, Chemistry, Class 12 Video Lecture

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next property is called color see now
the color of this colloidal solution
will depend on the wavelength of the
light color depends on lambda ladies see
as I told sky is a good example of
colloidal solution when because sky has
dust particles sky has water vapors
right
sky has the whole hydrogen gas nitrogen
gas carbon dioxide all this gas this chi
is a good example of colloidal solution
now if you see its color the sky is it
same Holt Road in the morning it is
different the nitrous in the evening it
is different early morning it is
different why because the color of the
light color of the whole colloidal
solution depends on the wavelength of
the light scattered by the dispersed
particle so now if you see the light is
coming in this direction expose Sun this
dispersed particle this particles will
actually disperse the light so the
wavelength of this line which is
dispersed by these particles will
actually besides a color always right
see in any color if you see here if I
see this particular mountain is little
great fine because sunlight is falling
on this and it is the wavelength of the
light that is reflected from this is
what that color right because this is
absorbing all the current of the Sun
except that grey color and is reflected
back and I can see that same thing since
in the case of collide what is happening
these quads are also small particles
right it is not absolute reflection
correct scattering actually no light
gets scattered because some get
reflected some get refracted is called
scattering of light so the color of the
choroidal solution depends on the
wavelength of the light scattered
whether the light scattered by the
dispersed particles
- first this is my particle this is this
first particle because this is particle
in the dispersed medium correct it is
not dependent on the incident light see
if you see the wavelength of the Sun is
always same right but if you see the sky
color is different in the morning
early morning sky color is different in
the peak afternoon sky color is
different in the night in the evening
it's all different because the
wavelength the color depends not only
not only incident light but on the
dispersed light correct the scattered
light actually and also the color of
this colloidal solution also changes in
the way it is observed by the viewer
example the observe the viewer is also
having it from this direction in the
view where is observing is from this
direction for a given object the viewer
may feel is a different color example if
I take the mixture of milk and water my
glass it has some milk and what will
plus water is nothing but my colloidal
solution so it appears blue from some
side it appears red from some side so
when you are viewing it from the
transmitted light right when you viewed
by the angle of transmitted light you
will see it as a red color when you view
it by the reflected light you see it as
a blue color so this sometimes says a
color depends also on the angle from
which your vania correct a good one more
example is see the gold solid you see
Gold's on gold so the finest gold solid
would be a very really fine world's on
where the colloidal size is less see
we're at the site also has a range like
1 to 1000 email so if you have in this
range a lower ring maybe 10 nanometer 20
meter and nanometer of gradle particle
in this volts all it is
red in color that's why the tone that
can be the class it's made of gold it is
stirred in curved gold liz has a gold
color right so the finest will have the
red color if you increase the size of
this all again you are still in the same
range one 200 mm 8 right it'll appear
purple you increase it further talking
only what the Gold's all here it will
appear blue and finally if you play make
it very very wave right very very vain
it will be golden so the same words all
mean is a huge range here 8 1 to 1000 in
the initial maybe a 50 or 60 nanometer
that kind of range it appears red we
need the size of the gold so if you like
the particle of the gold song because
purple then blue in the gold mine it was
smaller the size again the refracted
light the scattered light is different
wavelength because because the
wavelength of this reflected light or
scattered light depends on the size of
the particles also right so in that the
world so it's a very good example Gold's
on depending initially the size of the
particles the color is changing all
worlds also all worlds one next is a
Brownian movement see what is Bonnie
moment Jesus all particles this is only
for the collides please known willing to
the collides the soil particles I have
drawn when this is my collide colloidal
solution and I have taken only one
particle here just to explain you this
all particles actually they they move at
a random zigzag path you take nice all
particles moving in a random zig sector
hey and this type of motion is called
Brownian movement steam out of named
after the discoverer roller Brownian
first discovered this zigzag movement of
pollen grains in water
entra microscope under the microscope
only can help of this and this was as I
told discovered by Brownian and he
observed the movement of polar ingrains
in water and why it happens is it
happened because of collision between
the molecule
of dispersion medium and sole particles
so I am this medium the water there is a
molecules here also because the mod
water of emceeing has what I have
imagined 817 molecules right so the
molecules are the dispersion medium in
this case cotton and my small particles
they're also big they both are big and
they are the same container so they may
fight because of the collision between
these water molecules here it is my
dispersion medium and the soil particles
they move in a zigzag duration please
note this happens only for collide
because the other tweaks team is they
told either is a suspension or solution
in case of suspension the particle size
is very big since the particle size is
very big the prong in movement observed
it is very small because the particle is
very big and it is not able to move
right because the particle is big it
carries mass so it is very difficult to
move a fat guy and because of the mass
is very easy to group us light guy same
thing
it is very fat is very huge in size very
difficult to move so it is not observed
in suspension because the particle size
is very big in case of solution pure
solution the particles it is very small
in case of as I told this is very small
the brand moving is very fast opponent
movement is there but it is very very
fast since it is very fast you can't
observe this under microscope you can
absorb this under a very high powerful
instrument but under a microscope will
not be able to observe the Brownian
movement for pure solution because the
particle size is very small and they
move at a very very high speed thus and
the microscope you can observe Brownian
meant only for collides correct and this
drawing woman actually had a steering
effect and this is the reason why
colloids are stable they don't separate
they don't correlate and settle down
because this Brahmi movement is nothing
but if you dream and something but make
colloidal particles micro particle is
moving around always it will not settle
down like it's happening because the
cool is in Vilna colloidal particle and
the molecules of the dispersion medium
right so this Ronon movement is the
reason for the stability of this correct
thank you
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