THE MODEL SCHOOL – ABU DHABI
SEPARATION METHODS
CLASS –VIII (F, G, H)
Lesson -4-TOPIC –SEPARATION METHOD.
Q.1
What is distillation?
Ans.
The process in which the component of substance or liquid mixture is separated by heating it to a certain
temperature and condensing the resulting vapors.
Q.2
Which type of mixture can be separated by the process of distillation? Give example.
Ans.
When one component of the mixture is volatile and others do not vaporize under the same condition, they can
be separated by distillation. There should also be large different in boiling point of the component of mixture.
For Example:
1. Salt and Water
1. Acetone and Water
Q.3
Define Volatility?
Ans.
The Speed with which a substance changes from solid to liquid, Liquid to vapors and so on.
Q.4
What is fractional distillation?
Ans.
Fractional distillation is a technique of separation of a liquid mixture into fractions differing in boiling point. (B.P.
of components have very small difference and hence composition) by means of distillation typically using a
fractionating column.
Q.5
Describe a method used to separate mixture of ethanol and Methanol.
Ans.
When vapors of mixture pass through the fractionating column, separated liquefaction and vaporization take
place subsequently, the vapors of low boiling methanol enter the condenser from the fractionating column, condense
to liquid and get collected in the round bottomed flask first. Similarly ethanol with higher boiling point can be collected
later in another round bottomed flask.
Q.6
What is separating funnel?
Ans.
Separating funnel is an apparatus used for separating immiscible liquid from their mixture.
Q.7
Define term sublimation.
Ans.
The process in which a solid, when heated, changes directly into gas without melting into liquid is called
sublimation.
For Example:
1. Camphor and glass powder.
Q.8
Which are the methods that can be used to separate common salt, ammonium chloride and sand? Write the
methods in the order in which they are applied.
Ans.
Ammonium chloride sublimes on heating whereas common salt and sand do not sublime. So,
ammonium
chloride is separated from common salt and sand by the process of sublimation. When the mixture containing
common salt, ammonium chloride and sand is heated, then ammonium chloride form vapors easily. These
vapors on cooling give pure ammonium chloride. Common salt and sand is left behind. After ammonium
chloride has been removed add water to the common salt and sand mixture and dissolve the salt .Sand can be
separated from common salt by filtration. Then the salt solution can be heated to evaporate the water and
obtain the common salt as solid. The sand can be dried to obtain the dry sand.
Q.9
What is centrifugation method?
Ans.
It is the method used for separating components from a mixture based on the difference in the mass of
particles.
Q.10
Describe the process of centrifugation?
Ans.
In order to separate insoluble particles in a liquid mixture on the basis of their mass difference, centrifuge is
used. In this method the liquid containing the sample is taken in a test tube and rotated about a central point in
the instrument. The particles with higher mass then get separated, away from the center and those with lower
mass remain closer to the Centre.
Q.11
What is chromatography?
Ans.
Chromatography is the method used to separate more than one solute dissolved in the same solvent. This
method was first employed for separating coloured substance and hence this process came to be known as
chromatography.
Q.12
A few mixtures are given below. Tabulate the method to separates their component and give the season for
selecting the method.
Ans.
Mixture
Common salt and ammonium
chloride
Sugar solution
Method
Sublimation
Petrol and kerosene
Fractional distillation
Camphor and glass powder
Sublimation
Iron powder and sand
Magnetic separation
Evaporation
Reason
Ammonium chloride sublimes
whereas common salt doesn’t
Difference in volatility of
particle
Difference in boiling point of
two liquids is less.
Camphor sublimes whereas
glass powder doesn’t.
Difference in magnetic
properties of particles
Q.13
Given below are certain changes taking place to the particles during changes of state from this find out and
tabulate the changes in the particles when water boils in form of steam and also when steam condense to form
water .
Distance increase
Attractive force decrease
Energy increase
Rate of movement increase
Distance decrease
Energy increase
Attractive force decrease
Rate of movement increase
Water boils to form stream
yes
yes
yes
yes
No
No
No
No
Stream condense to form water
No
Yes
No
No
Yes
Yes
Yes
Yes
Q.14
Many minerals are present in ordinary water.
a)
Which is the method that can be used to remove the minerals and obtains pure water?
Ans.
Distillation
b)
In which type of mixture is this method employed?
Ans.
When one component of the mixture is volatile and other do not vaporize under the some conditions, they can
be separated by distillation. Components of a mixture should also possess a large difference in their boiling
points.
c)
Water purified by this method is distilled water, while two instance of its use.
Ans.
1) The distilled water is used for injection.
2) It is used in storage battery.