Class 9 Science chapter is matter around us pure notes pdf

IS MATTER AROUND US PURE
2.1 INTRODUCTION
(i) The matter (which is made up of atoms) around us is of two
types: pure substances and mixture.
(ii) Pure substances are elements and compounds, as they contain
only one kind of particles.
(iii) Homogenous mixtures of two substances formsolution in which
particle size is minute.
(iv) If the size of particles is big enough to be seen with naked eyes,
than suspension is formed.
(v) If particle size is between solution and suspension, then colloid
formation takes place.
(vi) Separation of mixtures can be done by filteration centrifugation,
chromatography, distillation etc.
(vii)During changes , sometimes new substances are formed called
chemical changes.
(viii) If new substances are not formed then change is called physical
change.
2.2 CHEMICAL CLASSIFICATION OF MATTER
Matter
Pure substances
Elements Compounds
Mixtures
Homogeneous
mixture
Heterogeneous
mixture
Metals Non-metals Metalloids Noble gases
A kind of matter that cannot be separated into other kinds of matter
by any physical process is called a substance.
For example, iron, sucrose (canesugar), water, sodium chloride etc.,
2.1 Introduction
2.2 Chemical classification of
matter
2.3 Types of pure substances
2.4 Mixture
2.5 Solution
2.6 Suspension
2.7 Colloids
2.8 Separating the
components of a
mixture
2.9 Physical & Chemical
change
2.10 Types of Substances
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are substances. The composition of a substance is the same throughout even at the atomic or
molecular level.
Pure Substance : A homogeneous material which contains particles of only one kind and has a definite
set of properties is called a pure substance.
Examples : Iron, silver, oxygen, sulphur, etc., are pure substances, because each one of them has only
one kind of particles.
However, if a substance is composed of two or more different kinds of particles combined together in
fixed proportion by weight, then the substance is also regarded as pure substance.
2.2.1 Characteristics of Pure Substances
(i) A pure substance is homogeneous in nature.
(ii) A pure substance has a definite set of properties.
These properties are different from the properties of other substances.
(iii) The composition of a pure substance cannot be altered by any physical means.
2.3 TYPES OF PURE SUBSTANCES
Types of Pure Substances
Elements Compounds
2.3.1 Elements
The word element was introduced for the first time by Lavoisier, “an element is the simplest or
basic form of a pure substance which cannot be broken into anything simpler, by physical or
chemical methods.”
The common examples of elements are hydrogen, carbon, oxygen, nitrogen, sulphur, copper, silver, gold
etc.
(i) Although more than 115 elements are known, the universe is made mainly from the two. These are
hydrogen (92%) and helium (7%) and the rest of the elements have a contribution of only 1% by mass.
(ii) Out of the known elements, only about 92 have been found to be present in nature, the rest have
been synthesised by the scientists in the laboratory.
(iii) The man made elements are also known as synthetic elements.
Types of elements
Types of Elements
Metals Non-metals Metalloids
A) Metals
Out of 92 elements nearly 70 elements belong to a particular class known as metals. In the metals the
atoms are very closely packed together and have special types of bonds known as metallic bonds.

Because of very tight or close packing the metals are quite hard.
Important Characteristics of the Metals
1. Solids at room temperature. Exception : Mercury (liquid at room temperature).
2. Shining surfaces. Property as known as lustre.
3. Good conductors of heat and electricity. eg. Au, Ag Exception : Heat (Pb), Electricity (Hg).
4. Quite hard. Exception : Sodium & potassium are soft.
5. Malleable. Eg. Fine Al foils are used for wrapping different types of food.
Thin foils of silver are used for decorating sweets.
6. Ductile. All electric wires drawn from different metals are very fine.
7. Sonorous. The sound produced on bending a tin foil is known as ‘tin cry’.
8. Generally, have high melting and boiling points.
B) Non-Metals
Non-metals as the name suggests are opposite to metals which means that their properties are quite
different from the metals.
Important properties of Non-metals
1. Either gases or solids at room temperature. Exception : Bromine (liquid at room tempeature)
2. Non-metals vary in colour with generally dull surfaces. Exception : Diamond, Crystals of iodine have
bright lustre.
3. Mostly Poor conductors of heat and electricity. Exception : Graphite
4. Quite Soft. Exception : Diamond
5. Non-malleable and non-ductile.
6. Not Sonorous.
7. Very low melting and boiling point as compare to metals.Exception : Diamond, SiC.
C) Metalloids
There are a few elements which possess the characteristics of both the metals and non-metals. These are
actually border-line elements and are known as metalloids.Afew common examples of metalloids are:
Arsenic, Antimony, Bismuth, Boron, Telurium, polonium, silicon.
2.3.2 COMPOUNDS OR CHEMICAL COMPOUNDS
A pure substance containing two or more elements which are combined together in a fixed propertion by
mass. eg. water (H2
O) consist of two elements hydrogen and oxygen are present in the ratio of 2 : 16 or
1 : 8 by mass. Water may be obtained from a number of sources such as rain, river, sea, well, lake etc. But
in the pure form any sources the two elements are present in the same fixed ratio i.e., 1 : 8 by mass.

Characteristics of Compounds
1. A pure compound is composed of the same elements.
2. A pure compound is homogeneous in nature.
3. A chemical compound is formed as a result of chemical reaction between the constituent elements.
4. Properties of the compound are altogether different from the elements from which it is formed.
5. Constituents of a chemical compound cannot be separated mechanically.
6. Formation of compounds involves energy changes.
Illustration 1
Identify the constituent elements of the following compounds.
(i) Baking soda (ii) Ammonium chloride
(iii) Zinc sulphate (iv) Calcium nitrate
(v) Silver chloride (vi) Ammonia
Solution
S.
No.
Compound Formula Constituent elements
1. Baking soda NaHCO3 Sodium, hydrogen, carbon,
oxygen
2. Ammonium chloride NH4Cl Nitrogen, Hydrogen, Chlorine
3. Zinc sulphate ZnSO4 Zinc, Sulphur, Oxygen
4. Calcium nitrate Ca(NO3)2 Calcium, Nitrogen, Oxygen
5. Silver chloride AgCl Silver, Chloride
6. Ammonia NH3 Nitrogen, hydrogen
2.4 MIXTURE
A mixture is that form of matter in which two or more substances (elements or compounds) are present
in any proportion.
For example, air is a mixture of mainly oxygen, nitrogen, smaller amounts of CO2
, dust particles etc, are
also present in the air.
2.4.1 Characteristics of a Mixture
Mixture contain more than one substance, and show the following characteristics.
(i) In mixtures, the consititutents may be present in any proportion.
(ii) Mixture show the properties of all the constituents present there in. For example, a mixture containing
sugar and salt will be salty-sweet.
(iii) During the preparation of a mixture, no energy such as, heat, light and electricity is absorbed or
evolved.
(iv) Mixtures (except solutions) are heterogeneous.
(v) The components of a mixture can be separated by simple physical methods.
2.4.2 Homogeneous Mixture
—A mixture is said to be homogeneous if the different constituents or substances present in it exist in one
single phase without any visible boundaries of separation in them.
—In a homogeneous mixture, the constituents particles cannot be identified or seen without the help of
powerful microscope.
Examples : All solutions, such as solutions of common salt, copper sulphate, sugar, etc., are examples of

homogeneous mixture. Similarly, alloys such as brass, bronze, etc., are homogeneous solid solutions of
metals.
2.4.3 Hetergeneous Mixture
A mixture is said to be heterogeneous if it does not have a uniform composition and also has visible
boundaries of separation between the constituents. In a heterogeneous mixture, these can be easily seen.
sometimes with naked eye’s only.
Examples : A mixture of sand and salt, iron powder and sulphur powder, the soil, etc. are examples of
heterogeneous mixtures.
TYPES OF MIXTURE
Example
Type of mixture Homogeneous mixture Heterogeneous mixture
1. Gas in gas Air (mainly O2 + N2)
2. Gas in liquid Aerated water (CO2 + H2O)
3. Gas in solid Hydrogen in palladium
4. Liquid in liquid Ethyl alcohol + Water Water + Oil
5. Liquid in solid Mercury in amalgamated zinc
6. Solid in liquid Sugar in water Chalk in water, Dust (fine sand) in
water
7. Solid in solid Alloys, eg., brass Mixture such as, sand + iron filings;
sand + ammonium chloride etc.
Amixture containing potassium nitrate, sulphur and charcoal is called gun powder.
Difference between Compounds and Mixture
Compounds Mixture
1 In a compound, two or more elements are
combined chemically.
In the mixture, two or more elements or
compounds are simply mixed and not
combined chemically.
2 In a compound, the elements are present
in the fixed ratio by mass. This ratio
cannot change.
In a mixture, the constituents are not
present in fixed ratio. It can change.
3 Compounds are always homogeneous i.e.,
they have the same composition
throughout.
Mixtures may be either homogeneous or
heterogeneous in nature.
4 In a compound, the constituents lose their
identities i.e., a compound does not show
that characteristics of the constituting
elements.
In a mixture, the constituents do not lose
their identities i.e., a mixture shows the
characteristics of all the constituents.
5 In the formation of a compound, energy in
the form of heat, light or electricity is
either absorbed or evolved.
No energy change is noticed in the
formation of a mixture.
6 In a compound the constituents cannot be
separated by physical means.
The constituents from a mixture can be
easily separated by physical means.
Illustration 2
Explain why, air is considered a mixture and not a compound.
Solution
Air is considered a mixture because of the following reasons

(i) Air can be separated into its constituents like oxygen, nitrogen etc. by the physical process of fractional
distillation(of liquidair)
(ii) Air shows the properties of all the gases present in it for example, oxygen supports combustion and
air also support combustion, carbon dioxide turns lime water milky and air also turns lime water milky
though very very slowly.
(iii) Heat and light, etc are neither given out nor absorbed when air is prepared by mixing the required
proportion of oxygen, nitrogen, carbon dioxide, argon, water vapour etc.
(iv) Air has a variable composition because air at different places contains different amounts of the
various gases. It does not have a definite formula.
(v) Liquid air does not have a fixed boiling point.
Illustration 3
How can you say that water is a compound?
Solution
Water is a compound because
(i) It is represented by formula H2O
(ii) It has a fixed boiling point i.e. 100°C
(iii) Hydrogen and oxygen do not retain their properties
(iv) Heat is produced during preparation of water.
(v) Hydrogen and oxygen air in a fixed ratio i.e. 2 : 1.
2.5 SOLUTION
A homogeneous mixture of two or more substances is called a solution Example is sugar and water.
This means that if we take out 1 mL sample from different parts of this solution, it will have
* the same degree of sweetness, and
* the same concentration. It means all 1 mL sample of this solution will contain the same number of sugar
and water molecules.
Dust-free air is a homogeneous mixture of many gases. The main gases present in the air are nitrogen
(78.1%) and oxygen (20.9%).
2.5.1 Component of a Solution
A solution basically has two components, i.e., a solvent and a solute.
(a) Solvent : The component of a solution which dissolves the other component in itself is called solvent.
Usually, a solvent is the larger component of the solution. For example, in the solution of copper sulphate
in water, water is the solvent. Similarly, in paints, the turpentine oil is the solvent.
(b) Solute : The component of the solution which dissolves in the solvent is called solute. Usually, solute
is the smaller component of the solution. For example, in the solution of common salt in water, the
common salt is the solute. Similarly, in carbonated drinks (soda water), carbon dioxide gas is the solute.
* 2.5.2 Saturated and Unsaturated Solutions
(a) Saturated Solution : – A solution, which at a given temperature dissolves as much solute as it is
capable of dissolving, is said to be a saturated solution.
(b) Unsaturated Solution : – When the amount of solute contained in a solution is less than saturation
level, the solution is said to be an unsaturated solution.
(c) Super Saturated Solution : – A solution which contains more of the solute than required to make a
saturated solution, is called a super saturated solution.

2.5.3 True solution and its characteristics
(a) True solution : A solution in which the particles of the solute are broken down to such a fine state,
that they cannot be seen under powerful microscope is called a true solution.
In a true solution, the particles of the solute are broken down to a diameter of the order of 10–8
cm or less.
(b) Characteristics of True Solution
1. A true solution is always clear and transparent, i.e., light can easily pass through it without scaltering.
2. The particles of solute break down to almost molecular size and their diameter is of the order of 1 nm
(10–9
m) or less.
3.Atrue solution can completely pass through filter paper as particle size of solute is far smaller than the
size of pores of filter paper.
4. Atrue solution is homogeneous in nature.
5. In a true solution, the particles of solute do not settle down, provided temperature is constant.
6. From a true solution, the solute can easily be recovered by evaporation or crystallisation.
7. A solution in which water acts as the solvent is regarded as the aqueous solution while the one in
which any other liquid is the solvent is known as non-aqueous solution. For example,
Solution of salt in water is aqueous solution. Solution of bromine in carbon tetrachloride is non-aqueous
solution.
SOLUBILITY
The maximum amount of a solute which can be dissolved in 100 g of a solvent at a specified temperature
is known as the solubility of that solute in that solvent (at that temperature). While expressing the solubility
of a substance, we have to specify the temperature also.
A) Solubility of solids in liquids
Solubility of solids in liquids is effected by two factor.
(a) Effect of temperature:As the temperature goes on increasing, the solubility of solids in liquids goes
on increasing because as the temperature increases, the kinetic energyof the molecules goes on increasing
which increase the space between them and more solids can be dissolved.
(b) Effect of pressure: There is no effect of pressure on the solubility of solids in liquid.
B) Solubility of Gases in liquids
Solubility of gases in liquids is also effect by temperature and pressure.
(a) Effect of temperature:As the temperature goes on increasing, the solubility of gases in liquids goes
on decreasing because as the temperature increases, the kinetic energy of the molecules goes on increasing
and gas comes out so the molecules come closer. Hence the solubility decreases.
(b) Effect of pressure: As the pressure increases the solubility of gases in liquids goes on increasing
Illustration 4
4 g of solute is dissolved in 40 g of water to form saturated solution at 25°C. Calculate the solubility
of solute.
Solution
Solubility (in saturated solution)
Mass of solute
×100
Massof solvent
Mass of solute = 4 g; Mass of solvent = 40 g

Solubility (in saturated solution) =
4
100 10
40
g
g
g
 
Illustration 5
75 g of sugar is dissolved in water to make 300 g of the solution. Find the solubility.
Solution
Here we have given
Amount of solute = 75 g
Amount of solution = 300 g
Amount of solvent = 300 – 75 = 225 g
Now, since solubility =
Amount of solute
×100
Amountof solvent
75 100
100 33.3
225 3
g
   
Concentration of a Solution
Thequantityof solutedissolvedin agiven massor volumeofthesolution orthesolventis called concentration
of the solution.
Measuring the concentration of a solution
The concentration of a solution is measured as the amount of the solute present in a given amount of the
solvent or solution. It is normally expressed as mass percent or as volume percent.
A) Mass Percent
Mass percent of a solution may be defined as :
the number of parts by mass of one component (solute or solvent) per 100 parts by mass of the solution.
If A and B are the two components of a binary solution,
Mass percent of A =
W
W W
A
A B

100
Mass percent of B =
W
W W
B
A B

100
Both, the mass of solute and that of the solution must be expressed in the same mass units, viz, both in gm
or both in kilograms.
Illustration 6
A solution has been prepared by dissolving 5 g of urea in 95 g of water. What is the mass percent
of urea in the solution?
Solution
Mass percent (Mass %) =
Mass of solute
×100
Mass of solution

Mass of urea = 5 g; Mass of water = 95 g
Mass percent of urea =
5
100
(95 5)


5
100 5%
100
 
B) Volume Percent
The number of parts by volume of one component (solute or solvent) per 100 parts by volume of t he
solution.
Mathematically, Volume percent of A =
V
V V
A
A B

100
Volume percent of B =
V
V V
B
A B

100
Illustration 7
A solution contains 5 ml of alcohol mixed with 75 ml of water. Calculate the concentration of the
solution in terms of volume percent.
Solution
Concentration of solution =
Volume of solute
×100
Volume of solution
Volume of alcohol = 5 ml
Volume of solution= (5 + 75) = 80 ml
Concentration of solution =
5
100 6.25%
80
 
2.6 SUSPENSION
“Aheterogeneous mixture of insoluble particles of solute, spread throughout a solvent, is called suspension.
1. Muddy water, in which particles of sand and clay are suspended in water.
2. Slaked lime suspension used for white-washing has particles of slaked lime suspended in water.
3. Paints in which the particles of dyes are suspended in turpentine oil.
2.6.1 Characteristics of Suspensions
1. The size of particles is more than 10–5
cm in diameter.
2. The particles of suspension can be separated from solvent by the process of filteration.
3. The particles of suspension settle down, when the suspension is kept undisturbed. The process of
settling of suspended particles under the action of gravity is called sedimentation.
4. A suspension is heterogeneous in nature.
5. An excessive amount of scattering takes place in suspensions, because of bigger size of particles.
2.6.2 Properties of Suspensions
Following are the characteristic properties of suspensions :

(a) Heterogeneous nature. A suspension is a heterogeneous system.
(b) Visibility. The particles in a suspension can be seen with naked eyes or under a simple microscope.
(c) Particle size. In a suspension, the size of the particles is of the order of 10–7
m or larger.
(d) Sedimentation. The particles in a suspension have a tendency to settle down. Very fine particles,
however, remain suspended in the medium.
(e) Separation by filtration. Larger particles in a suspension can be separated from the liquid or air by
filtration.
2.7 COLLOIDAL SOLUTION OR COLLOIDS
(i) A heterogeneous solution in which the particle size is in between 10–7
cm to 10–9
cm, such that the
solute particles neither dissolve nor settle down in a solvent is called colloidal solution.
(ii) The component present in smaller proportion is the dispersed phase while the one present in greater
proportion is the dispersion medium.
Types of colloidal dispersions
Dispersed
phase
Dispersion
medium
Common name /
Type
Examples
Liquid Gas Liquid aerosol Fog, Liquid sprays etc.
Solid Gas Solid aerosol Smoke, Dust etc.
Gas Liquid Foam Soap lather, Fire extinguisher foam
Liquid Liquid Emulsion Milk, Water-in-oil or oil-in-water
emulsion
Solid Liquid Sol Metallic dispersions, Toothpaste,
Milk of magnesia, Mud
Gas Solid Foam Expanded polystyrene
Liquid Solid Gel Opal, pearls
Solid Solid Solid sol Pigmented plastics, Coloured glasses
2.7.1 Properties of a Colloid
Some characteristic properties of a colloid are described below :
(a) Heterogeneous nature. A colloid (or sol) is heterogeneous in nature. The particles in a colloid can
be seen only with a powerful microscope.
(b) Particle size. The size of particles in a colloid lies between 10–9
m and 10–7
m .
(c) Separation of colloidal particles by centrifigation. Therefore, colloidal particles cannot be separated
by ordinary filteration.
(d) Stability. Colloids are unstable unless stabilized by adding suitable stabilizer. The colloidal particles
tend to come together and settle down.
(e) Brownian movement of colloidal particles. When seen under a microscope, the colloidal particles
in a colloid are seen to be moving in a random (zig-zag) fashion. This zig-zag motion of particles in a
colloid is called Brownian motion.
(f) Light scattering by colloidal particles – Tyndall effect. The scattering of light by the particles in
a colloid is called Tyndall effect.

(g) Electrophoresis. The movement of colloidal particles under the influence of electric field is called
electrophoresis.
2.7.2 Application of Colloids
(a) Most of the applications of the colloidal solutions are because of the removal of charge or neutralisation
of charge on the colloidal particles. The process of neutralization of charge on the colloidal particles by the
addition of certain oppositely charged species is known as coagulation.
(i) Bleeding from a cut can be immediately stopped by applying alum or ferric chloride.
(ii) Delta is formed when river water comes in contact with sea water for a long period.
(iii) Sky appears to be blue in colour
(b) In our food. Many items in our food contain colloidal materials. For example, milk, starch, proteins,
fruit-jellies are colloidal in nature.
(c) In medicines.Alarge number of medicines and pharmaceutical preparations are colloidal in nature.
Such colloidal medicines are easily absorbed by the body tissues and, therefore, are more effective. For
example, colloidal gold, calcium, silver are used in medicines or as ointments.
Differences between a true solution, a colloid and a suspension
True solution Colloid Suspension
1. A true solution is a
homogeneous mixture of two, or
more than two substances.
A colloid is a homogeneous
looking but heterogeneous
mixture.
A suspension is a heterogeneous
mixture of a solid dispersed in a
liquid, or a gas.
2. In a true solution, solute
cannot be seen even with a
microscope.
In a colloid, the dispersed
particles can be seen only with a
powerful microscope.
In a suspension, the particles can
be seen with the naked eyes.
3. In a true solution, the size of
particle is about 10–10 m.
In a colloid, the size of particles
is between 10–7 and 10–9 m.
In a suspension, the size of
particles is greater than 10–7 m.
4. The constituents of a true
solution cannot be separated by
ordinary filtration.
The constituents of a colloid can
not be separated by filtration
they are separated by
centrifugation.
can be separated by ordinary
filtration.
2.8 SEPARATING THE COMPONENTS OF A MIXTURE
Some most commonly used methods for separating the constituents of a mixture are
* Handpicking * Sieving * Winnowing
* Sedimentation * Evaporation * Crystallisation
* Filtration * Sublimation * Chromatography
* Gravity method * Distillation * Fractionaldistillation
* Magnetic separation method * Centrifugation or Churning
Separating the Coloured components of a Mixture
The coloured components of a mixture can be separated by a technique called as chromatography.
(a) To separate the coloured components (called dyes) present in black ink.
Technique: Chromatography
Principle : Distribution.
Materials required : Strip of filter paper, a large size glass jar, jar cover, clips, cotton thread.
Procedure : Take a strip of filter paper (20 cm × 3 cm).

* Draw a line with a pencil about 2-3 cm from its lower end.
* Place this paper strip on a smooth surface (may be table top) and put a small drop of black ink with
the help of a fountain pen or a capillary tube. Let it dry up. Place another drop of ink at the same spot and
let it dry up.
* Now suspend the filter paper strip in a jar containing little water, so that the ink spot is slightly above
the level of water. Cover the jar and leave it undisturbed for some time. Record your observation.
Observations : Two or more coloured spots are seen at different distances from the reference line. The
coloured component which is more soluble in water rises faster than the others.
Conclusion : The black ink is a mixture of ....... dyes.
Application:
(i) To separate colours in a dye
(ii) To separate pigments from natural colour
(iii) To separate drugs from blood
Use of chromatography in the separation of constituents from a mixture :
(i) word chromatography implies writing in colour.
(ii) Technique was initially used to separate coloured components from pigments and dyes.
(iii)Wide rang of applications.
(iv) Chromatography is of a number of types such as absorption, thin layer.
(v) The paper chromatography is very simple and is commonly used in the laboratory.
(b) To separate cream from milk
Technique: Centrifugation
Principle: The denser particles a force to the bottom and the lighter particles at the top when spun
rapidly.
Materials required : Full-cream milk, churner, jug
Procedure : Take freash cold milk (unboiled) in a jug. Churn the milk with a churner. What do you
observe after some time? The separated cream floats over the milk, and can be removed.
Application of this method (Centrifugation)
* Used in washing machines to squeeze out water from the wet clothes.
* Used for separating cream from milk and butter from curd in dairies or at home.
* Used in diagnostic laboratories for testing blood/urine.

A centrifuge is used to separate suspended solid particles from a liquid, quickly. When the centrifuge is
switched on, the test-tubes (containing suspension) held in it swing out and spin (or rotate) at high speed.
The centrifugal force acts on suspended particles which forces them to go to the bottom of test tubes and
clear liquid remains on top (This sketch shows four test-tubes spinning at the same time)
(c) To separate the mixture of two immiscible liquids
Principle: Immiscible liquids separate out in layers depending on their densities.
The liquids which do not dissolve in each other are called immiscible liquids.
Materials required : Separating funnel, iron stand, beaker, oil and water.
Procedure : The mixture containing oil and water is taken in a separating funnel. The separating funnel
is clamped on an iron stand and allowed to stand for some time. After a while oil and water separate to
form two layers. Oil being lighter than water forms the upper layer. Water forms the lower layer. Open
the stopcock and collect the water in a beaker. Oil is left behind in the separating flask.

Separation of two immiscible liquids by using a separating funnel
Application:
(i) Separate mixture of oil and water
(ii) Extraction of Iron from its ore.
(d) To separate a mixture of two miscible liquids
Principle: Separation of two miscible liquids that boil without decomposition and have sufficient difference
in theirboiling points(Distillation)
To separate alcohol and water from their mixture. Take the mixture in a distillation flask. Fit it with a
thermometer. Heat the mixture slowly keeping a close watch at the thermometer. The alcohol vaporises,
condenses in the condenser and can be collected from the condenser outlet. Water is left behind in the
distillationflask.

(e) To separate a mixture of salt and ammonium chloride
Technique: Sublimation
Principle:To separate mixture that contain asublimable volatile component fromanon sublimable impurity.
Materials required : China dish, funnel, asbestos sheet, tripod stand
Procedure : Take the mixture of common salt and ammonium chloride in a china dish. Place this china
dish on a tripod stand and cover it with a perforated asbestos sheet. Place an inverted funnel on the
perforated sheet. Plug the opening of the funnel with a cotton plug. Heat the china dish on a low flame.
Observe the white fumes coming out of the mixture. What do you see? These white fumes start depositing
as white solid on the inner wall of the funnel.After a few minutes, stop heating and allow it to cool. Now,
remove the funnel. Scrape the white deposit of ammonium chloride with the help of a spatula. Common
salt is left behind in the china dish.
Separation of a mixture by sublimation. Here a mixture of common salt and ammonium chloride
is being separated by sublimation.
(f) Separation of the constitutents of the air
Principle: Separation of two miscible liquid for which the difference in boiling points is less than 25 K
(fractionaldistillation)
Air is a homogenous mixture of oxygen (O2
), nitrogen (N2
), carbon dioxide (CO2
) and noble gases (He,
Ne, Ar and Kr). These gases have different freezing and boiling points.
These gases, therefore, can be separated by liquefying and fractional distillation of the liquid air as shown
below :

Application: Separation of difference products of petroleum.
(g) To obtain pure copper sulphate from an impure sample.
Technique: Crystallization
Impure copper sulphate can be purified by the method of crystallization to obtain pure copper sulphate.
This is done as follows
(i) Take about 10 grams of impure copper sulphate and dissolve it in minimum amount of water in a
china dish to make copper sulphate solution.
(ii) Filter and copper sulphate solution to remove insoluble impurities.
(iii) Heat the copper sulphate solution gently on a water bath to evaporate water and obtain a saturted
solution (This can be tested by dipping a glass rod in hot solution from time to time. When small crystals
form on the glass rod, the solution is saturated). Then stop heating.
(iv) Allow the hot, saturated solution of copper sulphate to cooled slowly.
(v) Crystals of pure copper sulphate are formed. Impurities remain behind in the solution.
(vi) Separate the copper sulphate crystals from solution by filgration and dry.
The process of crystallization is used to purify a large number of water soluble solids.
For example, the common salt obtained from sea-water is an impure substance having many impurities in
it. So, common salt is purified by the process of crystallization.
An impure sample of alum is also purified by crystallization.
Crystallization is a better technique than ‘evaporation to dryness’ because of the following reasons
(i) Some solids (like sugar) decompose or get charred on heating to dryness during evaporation. There
is no such problem in crystallization.
(ii) The soluble impurities do not get removed in the process of evaporation. But such impurities get
removed in crystallization.

(h) Separation of coloured components from a blue/ black ink by paper chromatography :
With the help of this technique we can identify the blue as well black components in a drop of the ink
which is water soluble. In order to perform the experiment, take a strip of very fine filter paper (25 x 5
cm). Draw a fine line on the paper from one end approximately at a distance of 3cm. With the help of a
fine capillary tube, put a small drop of blue / black ink mixture in the centre of the line by a pencil as shown
in the Fig. Allow the strip to dry for sometime.
Now Suspend the strip in a jar containing a small amount of water so that the end of strip which has been
marked dips in water to length of about 0.5 to 1 cm.Allow the strip to stand undisturbed in the jar for about
20 to 30 minutes. Due to capillary action, water will rise upwards. Blue / black ink is actually a mixture of
blue and black dyes. Both the components present in the mixture will rise upwards. The more soluble will
move faster. In this way, the blue and black colours will get separated.
(i) To seperate the mixture of Common salt and water : Since common slat (sodium chloride) is
soluble in water, it can be separated by crystallisation. The process of distillation can also be used because
sodiumchloride is non-volatile in nature.
(j) To seperate the mixture of Iodine and sand : Sublimation process can be used. Iodine will
sublime on heating while sand will remain unaffected.
(k) To seperate the mixture of Kerosene and water : The liquids are not miscible with each other.
Separation can be done by using a separating funnel
(l) To seperate the mixture of Sugar and sulphar : The mixture is dissolved in carbon disulphide in
a beaker by stirring with a glass rod. Sulphur dissolves while sugar remains as such. On filtering, sugar
separates as the residue. The filtrate upon concentration and cooling gives crystals of sulphur.
(m) To purify impure sample of sugar containing impurity of some chalk.
The impure sample of sugar containing some chalk impurity represents a heterogeneous mixture. In order
to purify the sample or to recover sugar from it, dissolve about 5g of the sample in minimum volume of
water in a beaker. Stir occasionally with a glass rod. Filter the solution formed through funnel as discussed
filtrate will be a sugar solution in water. Transfer the solution in a china dish. Concentrate by heating so
that the volume of the solution becomes nearly half. The solution will be saturated. Place the china dish
over a beaker full of water and allow to remain undisturbed for sometime. Pure crystals of sugar will
appear in the dish.
Illustration 8
You are given a mixture of sand, water and mustard oil. How will you separate the components of
this mixture?
Solution
This mixture contains three components: sand, water and mustard oil. Now, sand is a solid which is
insoluble in water as well as mustard oil. Water and mustard oil are immiscible liquids.
(i) The mixture of sand, water and mustard oil is filtered. Sand is left on the filter paper as residue.

Water and mustard oil collect as filtrate.
(ii) The filtrate containing water and mustard oil is put in a separating funnel. Water forms the lower
layer and mustard oil forms the upper layer in separating funnel. The lower layer of water is run out first
by opening the stop-cock of the separating funnel. Mustard oil remains behind in the separating funnel can
be removed separately.
Illustration 9
Describe a method of separating common salt from a mixture of common salt and chalk powder.
Solution
This mixture contains two constituents: common salt and chalk powder.
Now, common salt is soluble in water whereas chalk powder is insoluble in water. So, this difference on
their solubility will be used to separate them. This is done as follows:
(i) Some water is added to the mixture of common salt and chalk powder, and stirred. Common salt
dissolves in water to form salt solution whereas chalk powder remains undissolved.
(ii) On filtering, chalk powder is obtained as a residue on the filter paper and salt solution is obtained as
filtrate.
(iii) The salt solutin (filtrate) is evaporated by dryness when common salt is left behind.
2.9 PHYSICAL AND CHEMICAL CHANGES
Physical change Chemical change
1 In a physical change, only physical
properties such as colour, physical state,
volume, etc., change. Chemical properties
remain unchanged.
In a chemical change, the chemical
composition and chemical properties of
the reactants undergo a change
2 No new substance is formed. A new substance is formed. It has
properties different from those of the
reacting substances.
3 No energy in the form of heat, light or
sound energy is absorbed or evolved in a
physical change
A chemical change is always
accompanied by the absorption or
evolution of energy in the form of heat,
light, or sound energy.
4 The original form of the substance can be
obtained easily by simple physical
methods.
The original substance cannot obtained by
simple physical methods.
5 Physical change is generally temporary, in
the sense that it can be easily reversed by
reversing the conditions.
Chemical change is a permanent change
in the sense that it cannot be reversed by
just reversing the conditions.

2.10 TYPES OF SUBSTANCES
Solved Examples
Example 1
Calculate the amount of water required to prepare 500 g of 2.5% solution of sugar?
Solution
Mass of solute
% of solute 100
Mass of solution
 
Mass of solute
2.5 100
500
 
2.5 100
Mass of solute 12.5 g
100

 
Mass of water = Mass of solution – Mass of solute
Mass of water = 500 – 12.5 = 487.5 g
Example 2
5 g of sugar is dissolved in 250 ml of solution. Calculate its mass percentage by volume.
Solution
Mass of solute (sugar) = 5 g
Volume of solution = 250 ml
Mass percentage by volume =
Massof solute
100
Volume of solution

5
100 2%
250
  
Example 3
How would you obtain sodium chloride from a mixture of sodium chloride and sulphur without
using water?
Solution
Sodiumchloride is soluble in water where as sulphur is insoluble in water. Take mixture of sodiumchloride
and sulphur in a beaker and add water to it. Now stir the mixture to dissolve the sodium chloride. Now the
sodium chloride solution containing sulphur is filtered by using filter paper and funnel. Sulphur remain as

residue on the filter paper. The sodiumchloride solution obtained after filteration is evaporated carefully to
get the crystals of sodium chloride.
Example 4
What happens when a hot saturated solution is cooled?
Solution
When a hot saturated solution is cooled, crystallization occurs.
Example 5
Classify the following into elements, compounds and mixtures
(i) Sodium (ii) Soil (iii) Sugar solution
(iv) Silver (v) Calcium carbonate (vi) Tin
(vii) Silicon (viii) Coal (ix) Air
(x) Soap (xi) Methane (xi) Carbon dioxide
Solution
Elements: Sodium, silver, tin, silicon
Mixture: Soil, sugar solution, coal, air, soap
Compound: Calcium carbonate, methane, carbon dioxide
Example 6
How colloids and solution can be distinguished from each other?
Solution
Colloids and solution can be distinguishing by usingTyndall effect.
The solution which scatter a beam of light passing through it and renders its path visible is a colloid
The solution which does not scatter a beam of light passing through it and does not render its path visible
is a solution.
Example 7
What is meant by saying that metals are malleable and ductile?
Solution
By statement metals are malleable and ductile we mean that metals can be beaten into thin sheet with a
hammer without breaking and can be drawn into the wires.
******

EXERCISE-I
1. Is colloidal solution homogeneous in nature? [1]
2. What do we name the zig-zag motion of particles in a colloidal solution? [1]
3. Suggest two ways to separate a mixture of iron filings and sulphur. [1]
4. Which of the following will shows Tyndall effect. [1]
(i) Sodium chloride solution
(ii) Starch solution
(iii) Brass
5. What happens when electric current is passed through a colloidal solution? [1]
6. Does freezing of ice represent a physical change? [1]
7. Compare the particle sizes in true solution, colloidal solution and suspensions. [1]
8. What will happen if the beam of light is passed through a colloidal solution? [1]
9. Is water free from suspended impurities a pure substance? [1]
10. Give one example of a non-aqueous solution.
11. Name the metal which is liquid at room temperature. [1]
12. A substance can be beatan into sheets and drawn into wires. What will you call it? [1]
13. Can a single substance act as a mixture. [1]
14. 5 g of sodium chloride is dissolved in 100 g of water to form a solution. Is this solution saturated in nature?
[2]
15. 4 g of a solute is dissolved in 36 g of water. What is the mass percent of the solution? [2]
16. What is solubility of a salt? Discuss the effect of temperature on the solubility of sodium chloride in water?
[2]
17. Name the elements which has the characateristics of both metals and non-metals, what we call them?
[2]
18. A combination of common salt and iron filings is a mixture and not a compound. Justify? [2]
19. A mixture contains sand and naphthalene. Both are solids. Suggest a method for their separation [2]
20. A compound is regarded as a pure substance while the mixture not. Assign reason. [2]
21. Give main points of distinction in true solution, colloidal solution and suspension. [3]
22. Bleeding from a fresh cut can be stopped by applying alum. Explain. [3]
23. What do you mean by physical and chemical changes? How will you distinguish them? [3]
24. A mixture of alcohol and water is called a true solution while that of mustard oil and water is known as
emulsion. how will you account for it? [3]
25. Asolution contains 40 g of a salt in 320 g of water. Calculate the concentration in terms of mass percentage
of the solution. [3]
26. To make a saturated solution, 36 g of solution chloride is dissolved in 100 g of water at 293 K. Find its
concentration at this temperature. [3]
27. How will you separate a mixture of common salt, sulphur powder and sand? [5]
28. Describe the steps involved in the separation of iodine, iron filings and salt from a mixture. [5]
29. (a) 9.72 g of potassium chloride dissolved in 30 g of water at 70°C. Calculate the solubility of potassium
chloride at that temperature.
(B) What do you understand by the statement “the solubility of copper sulphate in water at 20°C is 20.7 g”

EXERCISE-II
1. What are pure substances? Give two examples of pure substances. [1]
2. What is a mixture? Give two examples of mixtures. [1]
3. State whether the following statements is true or false: [1]
“Sugar is a pure substance”
4. What is an element? Give examples of two elements. [1]
5. Define a solute and a solvent. [2]
6. Which of the following will show Tyndall and effect, why? [2]
(a) Saltsolution (B) Milk
(C) Copper sulphate (D) Starch solution
7. Classify each of the following as homogenous or heterogenous mixture?
Soda water, wood, air, soil, vinegar, filtered tea.
8. How would you confirm that colourless liquid given to you is pure water? [3]
9. Which of the following materials fall in the category of a “pure substance” and why? [4]
(a) Ice (B) Milk
(C) Iron (D) Hydrochloric acid
(e) Calciumoxide (f) Mercury
(g) Brick (h) Wood
(i) Air
10. Which of the following are chemical changes, why? [4]
(a) Growth of a plant (B) Rusting of iron
(C) Mixing of iron fillings and sand (D) Looking of food
(e) Digestion of food (f) Freezing of water
(g) Burning of candle
11. Classify the following into elements, compounds and mixtures. [4]
(a) Sodium (B) Soil
(C) Sugar solution (D) Silver
(e) Calcium carbonate (f) Tin
(g) Silicon (h) Coal
(i) Air (j) Soap
(k) Methane (l) Carbon dioxide
12. Which separation techniques will you apply for the separation of the following [5]
(a) Sodium chloride from its solution in water
(B) Ammonium chloride from a mixture containing sodium chloride and ammonium chloride
(C) Small pieces of metals in the engine oil of a car
(D) Different pigments from an extract of flower petals
(e) Butter from curd
13. Write the steps you would use for making tea use the word solution, solvent, solute, dissolve soluble,
insoluble, filterate and residue. [5]
14. Explain the process involved in the separation of oil from water, with diagram [5]
15. Make the diagram involved in the separation of following mixtures (labell the diagram) [5]

(a) Tea leaves from tea (B) Iron pins from sand
(C) Wheat grains from husk (D) Fine mud particles suspended in water.
16. Pragya tested the solubility of three different substances at different temperatures and collected the data
as given below (results are given in the followin table, as grams of substance dissolved in 100 g of water to
form a saturated solution).
Substance Dissolved Temperature in K
283 293 313 333 353
Potassium nitrate 21 32 62 106 167
Sodium chloride 36 36 37 37
Potassium chloride 35 35 40 46 54
Ammonium chloride 24 37 41 55 66
(a) What mass of potassium nitrate would be needed to produce a saturated solution of potassium nitrate
in 50 g of water at 313 K?
(B) Pragya makes a saturated solution of potassium chloride in water at 353 K and leaves the solution to
cool at room temperature. What would she observer as the solution cools? Explain
(C) Find the solubility of each salt at 293 K and leaves the solution to cool at room temperature. What
would she observer as the solution cools? Explain
(D) What is the effect of change of temperature on the solubility of a salt?
EXERCISE-III
SECTION-A
• Fill in the blanks
1. An element made up of only one kind of _____________.
2. Milk is a ____________ solution byt vinegar is a ________ solution.
3. If a mixture contains iron filings as one of the constituents, it can be separated by using a _________
4. A heterogeneous mixture of liquid and solid is conveniently separated by ___________
5. Miscible liquids are separated by ___________.
6. Immiscible liquids are separated by using a __________.
7. A mixture of kerosene and petrol can be separated by __________.
8. The separation of liquids by fractional distillation is based on the difference in their _________.
9. Chemical changes in a ____________ change.
10. Distilled water is made from tap water by the process _________.
SECTION -B
• Multiple choice question with one correct answers
1. The major constituents of universe are:
(A) hydrogen and helium (B) hydrogen and oxygen
(C) nitrogen and oxygen (D) helium and neon
2. The most abundant element in earth’s crust is
(A) Carbon (B) Silicon (C) Nitrogen (D) Oxygen
3. Which of the following is a metalloid?

(A) Phosphorus (B) Nitrogen (C) Bismuth (D) Lead
4. Presence of impurities
(A) lowers the melting point of solid (B) increases the melting point of solid
(C) increases the boiling point of liquid (D) lowers the boiling point of liquid
5. The element which is a liquid below 30°C is
(A) Cesium (B) Lithium (C) Magnesium (D) Sodium
6 Gold of which purity is normally used in making ornaments?
(A) 20 carat (B) 22 carat (C) 24 carat (D) 18 carat
7 Which out of the following is a heterogeneous mixture?
(A) Air (B) Brass (C) Iodized table salt (D) Steel
8. Which of the following is not a compound?
(A) Marble (B) Washing soda (C) Quicklime (D) Brass
9. Carbon burns in oxygen to form carbon dioxide. The properties of carbon dioxide are
(A) Similar to carbon (B) Similar to oxygen
(C) Totally different from both carbon and oxygen
(D) Much similar to both carbon and oxygen
10. Size of colloidal particles in a solution is
(A) more than 100 nm (B) less than 1 nm
(C) between 100 to 1000 nm (D) between 1 to 100 nm
11. When a beam of light is passed through a colloidal solution, it gets
(A) reflected (B) absorbed (C) scattered (D) refracted
12. Cloud is an example
(A) solid dispersed in a gas (B) liquid dispersed in a gas
(C) liquid dispersed in a solid (D) solid dispersed in a liquid
13. The cause of Brownian movement is
(A) heat changes in liquid state (B) convection currents
(C) impact of molecules of dispersion medium on colloidal particles
(D) attractive forces between the particles of dispersed phase and dispersion medium
14. A mixture of ammonium chloride and sodium chloride can be separated by
(A) crystallisation (B) hand pricking (C) bysublimation (D) centrifugatio
15. ‘Malleable and ductile’ is best described by
(A) a metal (B) a non metal (C) a compound (D) a solution
16. A 5 percent sugar solution means that
(A) 5 g of sugar is dissolved in 95 g of water (B) 5 g of sugar is dissolved in 100 g of water
(C) 5 g of sugar is dissolved in 105 g of water (D) None of these
EXERCISE-IV
SECTION-A
 Multiple choice question with one correct answers

1. The process used in milk diviles to separate cream from milk.
(A) Distillation (B) Centrifugation (C) Chromatography (D) None
2. Example of Gel is
(A) Gelatine (B) Sponge (C) Mist (D) Ink
3. The size of solute particles in suspension is
(A) Smaller than colloidal particles (B) Bigger than colloidal particles
(C) Same of true solutions (D) None of these
4. The non-metal which is liquid at room temperature?
(A) Mercury (B) Helium (C) Gallium (D) Bromine
5. Which of the following is the property of non-metals?
(A) Brittleness (B) Pustrous (C) Hardness (D) Sonorous
SECTION-B
 Multiple choice question with one or more than one correct answers
1. Metals which have low densites
(A) Sodium (B) Potassium (C) Iron (D) Cobalt
2. Which of the following are metalloid?
(A) Mercury (B) Boron (C) Silicon (D) Germanium
3. Which of the following elements are present in K2
SO4
?
(A) Potassium (B) Sulphur (C) Oxygen (D) Hydrogen
4. Which of the following are examples of Aerosols?
(A) Paints (B) Sponge (C) Fog (D) Hairspray
5. Concentration of a solution can be represented by
(A) Parts per million (B) Mass percentage (C) Volume percentage (D) None of these
EXERCISE-V
Try yourself
1 25 g of NaCl is dissolved in 200 g of water to make a solution. Find the solubility.
2. 12 g of potassium sulphate is dissolved in 75 g of water at 60°C. What is the solubility of potassium
sulphate in water at that temperature?
3. What do you understand by the statement “The solubility of copper sulphate in water at 20° is 20.7 g”
4. If 110 g of salt is present in 550 g of solution, calculate the concentration of solution.
5. If 2 ml of acetone is present in 45 ml of its aqueous solution. Calculate the concentration of this solution.
6. A 15% alcohol solution means
(A) 15 ml alcohol and 85 ml water (B) 15 ml alcohol and 100 ml water
(C) 15 ml alcohol and 115 ml water (D) None of these
7. Classify the following into solutions, suspensions and colloids.
Soda water, milk blood, Ink, Smoke in air, Chalk water mixture, Milk of magnesia, Shaving cream, Muddy
river water.

8. What are two phases of colloids?
9. Which of the following will show “Tyndall Effect”
(A) Saltsolution (B) Milk (C) Copper sulphate solution (D) Water
Exercise-III
Section-A
1. Atoms 2. Colloidal,true
3. Bar magnet 4. Filteration
5. Fractionaldistillation 6. Separating funnel
7. Fractionaldistillation 8. Boilingpoints
9. Permanent 10. Distillation
Section-B
1. (A) 2. (D) 3. (C) 4. (C) 5. (A)
6. (B) 7. (C) 8. (D) 9. (C) 10. (D)
11. (C) 12. (B) 13. (C) 14. (C) 15. (A)
16. (A)
Exercise-IV
Section-A
1. (B) 2. (A) 3. (B) 4. (D) 5. (A)
Section-B
1. (A,B) 2. (B,C) 3. (A,B,C) 4. (C,D) 5. (A,B,C)
Exercise - V
Try Yourself
1. 12.5 2. 16 g at 60°C
3. It means that a maximum of 20.7 g of copper sulphate can be dissolved in 100 g of water at a
temperature of 20°C.
4. 20% 5. 4.4% 6. (A)
7. Solution Suspension Colloids
1. Soda water 1. Chalk water mixture 1. Milk
2. Milk of Magnesia 2. Muddy river water 2. Ink
3. Smoke in air
4. Shaving cream
5. Blood
8. 1. Dispersed phase (solute) 2. Dispersion medium (solvent) 9. (B)

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