Cleansing Action of Soaps and Detergents Video Lecture - Class 10

cleansing action of soaps and detergents
have you ever tried mixing oil and water
oil and water are immiscible liquids if
oil and water are mixed together oil
separates and forms a layer of its own
oil floats on water as it is less dense
than water why don't all and water mix
water molecules are by polar molecules
they form strong electrostatic bonds
with each other oil molecules on the
other hand are nonpolar and do not make
bonds with a polar water molecules the
bonds that hold oil molecules together
are weak van der Waals forces observe
that oil molecules are large as compared
to water molecules for the mixing of any
two liquids their molecules must have
similar natures since their molecules
are not similar water and oil do not mix
molecules that carry charge are
attracted to water and are called
hydrophilic or water-loving
while molecules without charge lack
affinity for water they are known as
hydrophobic oil is a hydrophobic liquid
if a mixture of oil and water is
agitated vigorously for a sufficient
period of time and emulsion is obtained
the emulsion consists of minut droplets
of oil dispersed in water what happens
if this emulsion is allowed to settle
down the oil droplets slowly coalesce
and form a separate layer as before we
can infer that the oil and water
emulsion is not a stable system let's
add some soap or detergent to the
mixture and see the magic addition of a
little soap of detergent before
agitating the mixture
helps in the formation of a stable
emulsion the soap or detergent acts as a
surfactant or emulsifier the surfactant
molecules surround the oil droplets and
prevent them from coalescing the
cleansing action of soaps and detergents
is due to their power to emulsify oil
and dirt come let's learn about the
cleansing action of soaps and detergents
in this module
at the end of this module you will be
able to describe the cleansing action of
soaps and detergents
soaps and detergents are surfactants
which help to dislodge dirt and grease
by emulsifying them and thus help clean
articles let's take a look at the
molecular structures of soaps and
detergents observe that they have
similar structures each molecule is
composed of a long nonpolar hydrocarbon
chain which is hydrophobic in nature and
a short polar head which is hydrophilic
in nature the hydrophilic end is
attracted by water molecules whereas the
hydrophobic end of the molecule is
repelled by water but is attracted by
nonpolar substances like oil the
cleaning action of detergents and soaps
is attributed to this special feature
have you ever wondered how soaps and
detergents work to get rid of dirt and
grime here's how dirt or grime generally
has an oily component water cannot
dissolve oil and hence water by itself
cannot take away dirt this is where soap
or detergent comes of use dirty clothes
are soaked in water containing soap of
detergent when detergent or soap
molecules come in contact with the oil
or dirt on the fabric the nonpolar
portion of such molecules attaches
itself to that bit of grime or oil over
time more and more detergent molecules
gather around it and a micelle is formed
with the oil or dirt inside it a micelle
is a ball-shaped collection of detergent
or soap molecules with the hydrocarbon
ends clumped together on the inside and
the polar heads on the outside
eventually through either agitation or
stirring of water or rubbing these
micelles are lifted off from the fabric
surface and get into the wash motor
remember that because of the charge on
the heads of the detergent molecules the
outer surface of the micelle is charged
since these missiles all have similar
charges they repel each other and remain
suspended in the water these get removed
when the water is drained off repeated
rinsing and wringing remove all such
missiles and make laundry crispy clean