Mixtures Video Lecture - Class 9

mixtures
matter present in our surrounding can be
classified as pure substances and
mixtures a mixture is a combination of
two or more substances which are not
chemically the same and do not
chemically react together a mixture has
the same properties as that of its
component elements and can be separated
by physical means in a mixture of sugar
and sand even if we increase the volume
of sugar or sand the mixture remains the
same so it implies that in a mixture the
components can be present in any
proportions when we dissolve common salt
in a glass of water we will obtain salt
solution
similarly put some mud in a glass
containing water and stir it well we
will obtain a mixture with the solid
particles of mud dispersed in water by
carefully observing you will find that
in common salt solution
no salt particles settle down to the
bottom of the glass but in the glass
containing muddy water some solid
particles settle down to the bottom of
the glass this explains that mixtures
have different compositions accordingly
mixtures can be classified as
homogeneous and heterogeneous a
homogeneous mixture has the same uniform
appearance and composition throughout
many homogeneous mixtures are commonly
referred to as solutions a solution is a
mixture of two or more substances in a
single phase the substance in the
largest amount is called solvent and the
substance in the smallest amount is
called solute now consider the case of
the common salt solution we have
prepared here water is the solvent and
salt is the solute homogeneous solutions
are classified as different types based
on the solvent and the solute one liquid
in liquid solution to solid in liquid
solution three gas and liquid solution
in a solution of vinegar in water both
the solvent and solute are liquids hence
it is a liquid in liquid solution in the
case of common salt solution it is a
solid in liquid solution the best
example of gas and liquid solution is
soda water soda water contains carbon
dioxide gas let's understand
heterogeneous solutions suspensions and
colloids are heterogeneous mixtures a
suspension is a mixture of large
particles the size of the particles in a
suspension is of the order of 10 to the
power of minus 5 centimeters or larger
in a suspension the solute particles do
not dissolve but they are suspended
throughout the solvent the muddy water
which we prepared is a suspension
colloids are also heterogeneous mixtures
but they appear like a homogeneous
mixture milk is a good example of
colloids the particle size and colloid
is smaller than 10 to the power of minus
5 centimeters in colloids the particles
are uniformly distributed throughout the
solution colloidal particles cannot be
seen with the naked eye because of their
small size but their presence can be
observed with the help of an ultra
microscope or an electron microscope
what is the effect of light in
homogeneous and heterogeneous mixtures
let us understand how light affects a
colloidal solution when egg albumin is
taken in a glass beaker and some water
is added to it we get a colloidal
solution of egg albumin if we were to
shine a beam of light from a torch
through the beaker the light is
scattered by the colloidal particles and
the path of light can therefore be
observed the light scattering effect
shown by particles in a colloid was
first explained by the British physicist
John Tyndall
the effect is known as the Tyndall
effect in the case of a suspension light
does not pass through it in a true
solution of salt in water we will not
see the path of light as there is little
scattering of light things to remember
mixtures are composed of variable
proportions of different substances
without chemical bonding and have the
same properties as that of its component
elements homogeneous mixtures have the
same uniform composition in appearance
throughout whereas heterogeneous
mixtures consists of visibly different
substances or phases a solution is a
homogeneous mixture of two or more
substances and the substance present in
the largest amount is called solvent and
that present in the smallest amount is
called the solute suspensions are a
heterogeneous mixture of large particles
on the order of 10 to the power of minus
5 in which the solute particles are
suspended throughout the solvent
colloids are heterogeneous mixtures in
which the particles are uniformly
distributed throughout the solution and
the particle size is smaller than 10 to
the power of minus 5 centimeters the
light scattering effects shown by
particles in a colloid is known as
Tyndall effect
you