02_Is Matter Around Us Pure.pdf

CHAPTER
Is Matter Around Us Pure
2
SUB- TOPICS
• Introduction
• Pure and impure substances
• Mixture and its types
• Solutions, suspensions and colloids
• Depuration of mixture
• INTRODUCTION
Ø Matter is made of one or more components known as substances.
Ø In terms of science, a substance is a kind of matter which cannot be separated into
any other types of matter by some physical means.
Ø Such a substance which has only one component and nothing else in it is called a
pure substance.
Ø Substances are mostly mixed with one another and their combination is known as
mixture.

Is Matter Around Us Pure Chemistry, Class : IX
Turtle Tutorials Foundation Programme 26
Substances (matter)
Pure substance
(only one substances present)
Element
An element in the simplest or
basic form of a pure substance
which can not be broken into
anything simpler than it by
physical or chemical methods.
Compound
A pure substance containing two
or more elements which are
combined together in a fixed
proportion by mass.
Metals, Non-metals
& Metalloids
Organic Inorganic
Molecules
Atoms
Impure substances
(more than one substances
present)
Mixture
The combination of two or more substances
(elements or compounds) which are not
chemically combined with each other and may
also be present in any proportion
Homogeneous mixture
(solutions)
Heterogeneous mixtures
(suspensions and colloids)

• PURE AND IMPURE SUBSTANCES
• Pure substances: A pure substance is one which is made up of only one kind of
particles. These may be atoms or molecules and can’t be separated by any physical
method for example water, sulphur, hydrogen, carbon etc. are know as pure
substances because they are made up of only one kind of particles. A pure substance
has a fixed composition as well as a fixed melting point and boiling point.
• Impure Substances: An impure substances is that which made by two or more than
two different kinds of particle (atoms or molecules) and can be separated by physical
method. All the mixtures are impure substances. Some of the examples of the
mixtures are: salt solution, sugar solution, milk, sea-water, air, sugarcane juice, soft
drinks, sharbat, rocks, minerals, petroleum, LPG, biogas, tap water, tea, coffee, paint,
wood, soil and bricks. A mixture may be homogeneous or heterogeneous. A mixture
does not have a fixed composition or a fixed melting point and boiling point.
Ø Types of pure Substances: Pure substances have been classified into two types.
These are elements and compounds.
Ø An element is the simplest or basic form of a pure substance which cannot be
broken into anything simpler than it by physical or chemical methods.
The later studies by Dalton have shown that the simplest form of matter is atoms. It
may now be defined as
The pure substance which is made up of one kind of atom only. Examples
hydrogen, carbon, oxygen, etc.
Elements can be solids, liquids and gases. For example, sodium and carbon elements
are solids; mercury and bromine elements are liquids, whereas hydrogen and oxygen
elements are gases, at the room temperature. In fact, majority of the elements are
solids.
Elements further classified in to three forms:
• Metals
• Non-metals
• Metalloids
Ø Metals
A metal is an element that is malleable and ductile, and conducts electricity some of
the examples of metals are: Iron, Copper, Aluminium, zinc,, Silver, Gold, Platinum,
Chromium, Sodium, potassium, Magnesium,
Ø Non-Metals
Non-metals as the name suggests are opposite to metals, which means that their
properties are quite different from the metals. They are comparatively less in number
but they are very important for living organism. Only about fourteen to fifteen
elements are non-metals. Eg. Carbon, Sulphur, Phosphorous, Hydrogen and Oxygen.

COMPARISON AMONG THE PROPERTIES OF METALS AND NON-METALS
Metals Non-Metals
1. Metals are strong and tough. They
have high tensile strength.
2. Metals are sonorous. They make a
ringing sound when struck.
3. Metals are lustrous (shiny) and can be
polished
4. Metals are solids at room temperature
(except mercury which is a liquid
metal).
5. Metals are good conductors of heat and
electricity.
6. Metals are malleable and ductile. That
is, metals can be hammered into thin
sheets and drawn into thin wires.
1. Non-metals are not strong. They have
low tensile strength.
2. Non-metals are not sonorous.
3. Non-metals are non-lustrous (dull) and
cannot be polished (except iodine
which is a lustrous non-metals).
4. Non-metals may be solid, liquid or
gases at the room temperature.
5. Non-metals are bad conductors of heat
and electricity (except diamond which
is a good conductor of heat, and
graphite which is a good conductor of
electricity).
6. Non-metals are brittle. They are neither
malleable nor ductile.
Ø 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. A
few common examples of metalloids are: Boron (B), Silicon (Si), Germanium (Ge),
Arsenic (As), Antimony (Sb), Bismuth (Bi), Tellurium (Te) and Polonium (Po).
Illustration – 1: State two reasons for believing that copper is a metal and sulphur is a non-
metal.
Solution: The two properties which tell us that copper is a metal and sulphur is a non
metal are given below:-
a. Copper
1. Copper is malleable and ductile. It can be hammered into thin sheets
and drawn into wires.
2. Copper is a good conductor of heat and electricity.
b. Sulphur
1. Sulphur is neither malleable nor ductile. It is brittle. Sulphur breaks
into pieces when hammered or stretched.
2. Sulphur is a bad conductor of heat and electricity.
• MIXTURE AND ITS TYPES
Compounds:
It is also pure substance like elements. But it represents a combination of two or more
than two elements which are combined chemically.
“A pure substance containing two or more elements which are combined together in a
fixed proportion by mass”
Example: (water), CO2 (Carbon dioxide),NH3 (Ammonia) etc.
Types of Compounds:
The compounds have been classified into two types. These are:
2
H O

(a) Inorganic compounds: These compounds have been mostly obtained from non-
living sources such as rocks and minerals. A few examples of inorganic compounds
are: common salt, marble, washing soda, baking soda, carbon dioxide, ammonia,
sulphuric acid ect.
(b) Organic compounds: The word ‘organ’ relates to different organs of living beings.
Therefore, organic compounds are the compounds which are obtained from living
beings i.e., plants and animals. It has been found that all the organic compounds
contain carbon as their essential constituent. Therefore, the organic compounds are
quite often known as ‘carbon compounds’. A few common examples of organic
compounds are: methane, ethane, propane (all constituents of cooking gas), alcohol,
acetic acid, sugar, proteins, oils, fats etc.
• Characteristic of compounds
• The important characteristics of the compounds are:
• A pure compounds is-composed of the same elements
• A pure compounds is homogeneous in nature
• Properties of the compound are altogether different from the element “from which
it is formed.
• Since a compound is formed as a result of chemical reaction, its properties quite
different from the elements from which it is formed. For example, hydrogen gas is
combustible while oxygen is a supporter of combustion. Water is formed as result
of the chemical reaction between the two gases. It is neither combustible nor a
supporter of combustion. It extinguishes or stops combustion. We often add water
to extinguish fire.
• Constituents of a chemical compounds cannot be separated mechanically.
• Formation of compounds involves energy change.
• What is considered to be a compound due to the following reasons:
• Water cannot be separated into its constituent’s hydrogen and oxygen by-physical
methods.
• Properties of water are entirely different from its constituents’ hydrogen and
oxygen. Hydrogen is combustible while oxygen supports combustion. Water is
quite different from the two and it extinguishes fire.
• Heat and light are given out when water is formed by burning hydrogen and
oxygen.
• The composition of water is fixed. Its constituents hydrogen and oxygen are
present in the ratio of 1: 8 by mass.
• Water has a fixed boiling point of 100°C (or 373 K) under atmospheric-pressure
of 1 atmosphere (or 760 mm).
Mixture
“The combination of two or more substance (element of compounds) which are not
chemically combined with each other and may also be present is any proportion is known
as mixture”. There are two type of mixture:
• Homogeneous mixture
• Heterogeneous mixture
Elements and compounds are pure substance. Mixtures are not pure substances in terms
of science.

(1) Homogeneous Mixtures
“A mixture is said to be homogeneous the different constituents or substances present
in it exist in one single phase without any visible boundaries of separation in them. A
homogeneous mixture has a uniform composition throughout”. A few examples of
homogeneous mixture are as follows:
When we dissolve a salt like sodium chloride of sugar present in the solid phase
water (liquid phase), the mixture formed as a result of mixing is in single phase only.
It is the liquid phase known as solution. In the solution, the particles of sodium
chloride or sugar lose their physical state but not their identity. A solution of sodium
chloride has a bitter taste while sugar solution is sweet in taste.
• Air is also a homogenous mixture of a number of gases like nitrogen, oxygen,
carbon dioxide, water vapours, inert gases etc. All the gases present in air
constitute one single phase i.e., gaseous phase. Air is also regarded as solution.
All homogeneous mixtures are regarded as solutions.
(2) Heterogeneous Mixtures
“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.”
A few examples of heterogeneous mixtures are:
• A mixture of sand and common salt is regarded as a heterogeneous mixture. No
doubt, these are present in the same phase i.e., solid phase but have clear
boundaries of separation. The particles of sand and common salt can be easily
seen in the mixture.
• Similarly, oil and water form a heterogeneous mixture. Here also both the
constituents are liquids but have different boundaries of separation. Both oil and
water are present in different layers.
Distinction between compounds and a mixture:
Compounds Mixtures
1. In a compound, two or more
elements are combined chemically.
2. In a compound, the elements are
present in the fixed ratio by mass.
This ratio cannot change.
3. Compounds are always homogeneous
i.e., they have the same composition
throughout.
4. In a compound, the constituents lose
their identities i.e., a compound does
not show that characteristics of the
constituting element.
5. In the formation of a compound,
energy in the form of heat, light or
electricity is either absorbed or
evolved.
6. In a compounds, the constituents
cannot be separated by physical
means.
In the mixture, two or more elements or
compounds are simply mixed not
combined chemically
In a mixture, the constituents are present in
fixed ratio. It can very.
Mixtures may be either homogeneous or
heterogeneous in nature.
In a mixture, the constituents do lose their
identities i.e., a mixture shows the
characteristics of all the constituents.
No energy change is noticed in the
formation of a mixture.
The constituents from a mixture can be
easily separated by physical mean.

Illustration – 2: (i) Explain why, air is considered a mixture and not a compound.
Solution Air is considered a mixture because of the following reasons:
a. Air can be separated into its constituents like oxygen, nitrogen,
etc., by the physical process or fractional distillation (or liquid air).
b. Air shows the properties of al the gases present in it. For example,
oxygen supports combustion and air also supports combustion;
carbon dioxide turns lime- water milky and air also turns lime-
water milky, though very, very slowly.
c. Heat and light, etc., are neither given out nor absorbed when air is
prepared by mixing the required proportions of oxygen, nitrogen,
carbon dioxide, argon, water vapour, etc.
d. Air has a variable composition because air at different places
contains different amounts of the various gases. It does not have a
definite formula.
e. Liquid air does not have a fixed boiling point.
(ii) Classify the following into element, compounds and mixture: Sodium,
Soil, Sugar solution, Silver, Calcium carbonate, tin Silicon, Coal, Air,
Soap, Methane, Carbon Dioxide, Blood.
Solution: We can classify the given materials into elements, compound and
mixtures as follows:
a. Elements: Sodium, Silver, Tin, Silicon
b. Compounds: Calcium carbonate, Soap, Methane, Carbon dioxide.
c. Mixtures: Soil, Sugar Solution, Coal, Air, Blood.
(iii) Give the names of the elements present in the following compounds:
(a) Quicklime (b) Hydrogen bromide, (c) Baking soda (d) Potassium
sulphate
Solution: a. Quicklime is calcium oxide, CaO. The elements present in it are:
Calcium (Ca) and Oxygen (O).
b. Hydrogen bromide is HBr. The elements presen tin it are:
Hydrogen (H) and Bromine (Br).
c. Baking soda is sodium hydrogencarbonate, NaHCO3. The elements
present in it are: Sodium (Na), Hydrogen (H), Carbon (C) and
Oxygen (O).
d. Potassium sulphate is K2SO4. The elements present in it are:
Potassium (K), Sulphur (S) and oxygen (O).
• SOLUTION, SUSPENSIONS AND COLLOIDS
The case of Solution
Solute: The substance which is dissolved to make solution known as solute like: salt,
sugar etc.,
Solubility of a solute: “The maximum amount of solute which can be dissolved is 100
gm of the solvent of form a saturated solution at a given temperature is known as a
solubility of a solute.”
It is directly proportional to temperature.

Solubility =
Solution can be further divided in to two types on the basic of solubility of solute
SATURATED AND UNSATURATED SOLUTIONS
Saturated solution: A solution is said to be saturated if it has maximum amount of the
solute dissolved in it at a given temperature and no solute can be dissolve further.
Unsaturated solution: A solution is said to be unsaturated if the more amount of solute
can be dissolved in it at a given temperature.
Suspensions
The substances which are insoluble in water form suspension. “ It is a heterogeneous
mixture in which the small particles of a solid are spread throughout a liquid without
dissolving in it’. Example: Chalk water mixture, muddy water milk of magnesia, fluorine
water etc.
Characteristic of Suspension
• A suspension is of heterogeneous nature- There are two phase. The solid particles
represent one phase while the liquid in which these are suspended or distributed
forms the other phase
• The particle size in a suspension is more than 100 mn (or 10-7
m).
• The particles in a suspension can be seen with naked eyes and also under a
microscope.
• The solid particles present in the suspension can be easily separated by ordinary filter
papers. No special filter papers are needed for the purpose.
• The particles in a suspension are unstable. They settle down after sometime when the
suspension is kept undisturbed. This is known as precipitate.
• It should be noted that suspension-and precipitate are actually the same. The
particles of the solid in the suspended form represent suspension. When they settle, a
precipitate result.
COLLOIDS
• Colloid is a kind of solution in which the size of solute partials is intermediate
between those the true solutions and those are in suspension. Colloidal solutions are
also heterogeneous in nature like suspensions, but they have smaller size of the
particles, which are distributed. It ranges between 1 nm to 100 nm i.e., in between the
particles size in true solution and suspension. Since the particles sizes are close two
what we notice in solutions most of the colloidal solutions appear to be homogeneous
like true solutions. But actually these are not.
• We come across a large variety of the colloidal solutions in daily life. Smoke coining
out of the chimneys of factories, tooth paste, ink, blood, soap solutions, jellies, starch
solution in water are a few common examples.
• We have stated earlier that the colloidal solutions are the heterogeneous mixtures.
This means that, the constituents are not present in a single phase. Actually there are
two phases in a colloidal solution. These are known as dispersed phase and
dispersion medium.
•
massof solute
100
massof solvent
´

CHARACTERISTIC OF COLLOIDAL SOLUTIONS
• Colloidal solutions appear to be homogeneous but are actually heterogeneous in
nature.
This happens because of particle size (1 nm to 100 nm), which is quite close to
particle in a colloidal solution as we do in case of suspension. But these can be seen
under a microscope.
• Colloidal solutions are a two phase system
We have discussed above that the colloidal solutions represent a two-phase system.
These are dispersed phase and dispersion medium. That is why, the colloidal
solutions are of heterogeneous nature.
• Colloidal particles pass through ordinary filter papers
In most of the cases, the colloidal solutions pass through ordinary filter papers like
true solutions. This is because of the fine size of the dispersed phase or colloidal
particles. Special filter papers known as ultra filter papers have to be used to separate
these particles from the dispersion medium.
• Colloidal particles carry charge
We have learnt that the dispersed phase particles in a colloidal solution remain
dispersed or suspended. They do not come close to one another as in case of
suspension. This happens due to the presence of some charge (positive or negative)
on these particles. Please remember that all the particles belonging to a particular
colloidal solution carry the same charge. That is why, these similarly charged
particles repel each other and remain dispersed or suspended. For example,
Hemoglobin, starch, gelatin, metal like copper, silver, gold, metal sulphides have
negative charge on their particles.
The hydroxides of metals like iron, aluminium, calcium etc. Have positive charge on
their particles.
• Particles in a colloidal solution follow zigzag path
It is normally not possible to see the colloidal particles because of their very small
size. However, their path can be seen under a microscope. These particles follow a
zig-zag path. You can observe this motion while watching a film in a theater. The
beam of light which falls on the screen from behind has dust particles present in it.
They follow zig-zag path. Such type of movement of the colloidal particles was
noticed for the first by Robert particles was noticed for the first by Robert Brown,
English scientist in 1828. This is known as Brownian motion.

• Tyndall effect:
In a colloidal solution, the particles are big enough to scatter light. This can be shown
as follows. If a beam of light is put on a colloidal solution (say, soap solution), kept
in a beaker in a dark room, the path of light beam is illuminated and becomes visible
when seen from the side. The path of light beam becomes visible because the
colloidal particles are big enough to scatter light falling on them in all the direction.
This scattered light enters our eyes and we are able to see the path of light beam.
• The particles in a colloidal solution scatter light
“The scattering of light by colloidal particles is known as Tyndall effect.”
• Difference between suspension, colloidal and true solution
Property Suspension Colloidal solution True solution
1. Particle size > 100 nm 1 to 100 nm < 1 nm
2. separation by ordinary
filtration
Possible Not possible Not possible
3. settling of particles Settle of their
own
Settle only on
centrifugation
Do not settle
4. appearance Opaque Generally
transparent
Transparent
5. Tyndall effect Shows Shows Does not show
6. diffusion of particles Do not diffuse Diffuse slowly Diffuse rapidly
7. Brownian movement May show Show May or may not
shown
8. Nature heterogeneous Heterogeneous Homogeneous
• To distinguish a colloid from a solution. We can distinguish between colloids (or
colloidal solutions0 and true solutions by using tyndall effect. For example, a soap
solution scatters a beam of light passing through it and render its path visible,
therefore, soap solution is a colloid (or colloidal solution). On the other hand, salt
solution does not scatter a beam of light passing through it and does not render, its
path visible, therefore, salt solution is a true solution.
• Classification of Colloids
Colloids are classified according to the physical state of dispersed phase (solute) and
the dispersion medium (solvent). These are
(i) Sol.
(ii) Solid sol.
(iii) Aerosol
(iv) Emulsion
(v) Foam
(vi) Solid foam
(vii) Gel

Technical name
of colloid
Dispersed
phase
Dispersion
medium
Examples
1. sol. Solid Liquid Ink, soap solution, starch
solution, most paints
2. solid sol. Solid Solid Coloured gemstone (kike ruby
glass)
3. aerosol (i) solid
(ii) liquid
Gas
Gas
Smoke, automobile exhausts
hairspray, fog, mist, clouds
4. emulsion Liquid Liquid Milk, butter, face cream
5. foam Gas Liquid Fire-extinguisher foam, soap
bubbles, shaving cream, beer
foam
6. solid
foam
Gas Solid Insulating foam, foam rubber,
sponge
7. gel Solid Liquid Jellies, gelatin
Illustration – 3: (i) A solution contains 30 g of sugar dissolved in 370 g of water.
Calculate the concentration of this solution.
Solution: We know that concentration of solution
Here, Mass of solute (sugar) = 30 g and , Mass of Solvent (water) =
370 g
So, Mass of solution = Mass of solute + Mass of solvent = 30 + 370 =
400g Now, putting the values of ‘mass of solute’ and ‘mass of
solution’ in the above formula, we get:
Concentration of solution = = 7.5 percent (or 75%)
(ii) If 110 g of salt is present in 550 g of solution, calculate the
concentration of solution.
Solution: Here, Mass of solute (salt) = 110 g and, Mass of solution = 550 g
Now, we know that; concentration of solution
percent (or 20%)
(iii) If 2 mL of acetone is present in 45 mL of its aqueous solution
calculate the concentration of this solution.
Solution: Here, volume of solute (acetone) = 2 mL and, volume of solution =
45 mL Now, we know that: concentration of solution
= 4.4 percent (by volume)
(iv) 12 grams of potassium sulphate dissolves in 75 grams of water 60°C.
What is its solubility in water at that temperature?
Solution: Here we have been given that 75 grams of water dissolves 12 grams of
potassium sulphate. We have to find how much potassium sulphate
Massof Solute
100
Massof solution
= ´
30 30
100
400 4
´ =
Massof Solute
100
Massof solution
= ´
110 100
100 20
550 5
= ´ = =
Massof Solute 2 200
100 100
Massof solution 45 45
= ´ = ´ =

will dissolve in 100 grams of water. Now, 75 g of water dissolves =
12 g of potassium sulphate So, 100 g of water will dissolve =
of potassium sulphate = 16 g of potassium sulphate. Thus,
the solubility of potassium sulphate in water is 16 g at 60°C.
• SEPARATION OF MIXTURE
These mixtures have two or more than two substance or constituents mixed. We may
require only one or two separate constituents of a mixture for one use. So tey need to be
separated the process which is used for it is based on the various physical properties of
the constituents like boling point, melting point, volatility density etc.
Commonly used process which are used to separate the constituents of mixture are
• Sublimation
• Filtration
• Centrifugation
• Evaporation
• Crystallization
• Chromatography
• Distillation
• Fractional Distillation
• Separating funnel
In order to learn the separation of mixtures, we will consider the following three cases:
1. Mixture of two solids
2. Mixture of a solid and a liquid
3. Mixture of two liquids.
• Separation of mixture of two solids
Mixture of two solids are separated by the following method
a. By using a suitable solvent (sugar and sand mixture)
b. By the process of sublimation (Ammonium chloride and common salt)
c. By using a magnet (mixture of iron filling and sulphur power)
Separation of mixture of solid and a liquid
• By filtration
• By centrifugation
• By evaporation
• By crystallization
• By chromatography
• By distillation
• To Separate Cream From Milk
• By centrifugation
It is a method for separating the suspended particle of a substance from a liquid in
which the mixture is rotated (or sperm) at a high speed in centrifuge and force to
denser particles to bottom and lighter on above layer.
• By the process of chromatography
The ink that we use has water as the solvent and the dye is soluble in it. As the water
rises on the filter paper it takes along with it the dye particles. Usually, a dye is a
mixture of two or more colours. The coloured component that is more soluble in
water rises faster and in this way the colours get separated.
This process of separation of components of a mixture is known as chromatography.
Kroma in Greek means colour. This technique was first used for separation of
colours, so this name was given, chromatography is the technique used for separation
of those solutes that dissolve in the same solvent.
12
100g
75
´

• Separation of dyes in black ink using chromatography
Separation of mixture of two liquids the miscible liquid (which mix together) in all
proportion and form single layer) and immiscible liquid (which do not mix with each
other and form a separate layers) are separated by the two method).
• By the fractional distillation (for miscible liquid)
To separate a mixture of two or more miscible liquids for which the difference in
boiling points is less than 25 K, fractional distillation process is used, for example,
for the separation of different gases from air, different factions from petroleum
product etc. The apparatus is similar to that for simple distillation, except that a
fractionating column is fitted in between the distillation flask and the condenser.
A simple fractionating column is a tube packed with glass beads. The beads provide
surface for the vapor to cool and condense repeatedly.
• Separation of the Gases of the Air
Air is a mixture of gases like nitrogen, oxygen, argon, carbon dioxide, helium, neon,
krypton, and xenon, etc. The various gases of air are separated from one another by
the fractional distillation of liquid air. This separation is based on the fact that the
different gases of air have different boiling points (when in liquid form). A flow
diagram showing the main processes involved in obtaining different gases from air is
given below:
Illustration – 4: 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.
(a) 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.
(b) 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 fun out first by
opening the stop-cock of the separating funnel. Mustard oil remains
behind in the separating funnel and can be removed separately.
v
vv
vv
v

K
KE
EY
Y P
PO
OI
IN
NT
TS
S
Ø Gold, silver, copper, iron, tin, lead, zinc, aluminium and mercury are some common
metals.
Ø Oxygen, nitrogen, graphite, chlorine, iodine, helium and argon are common non-meta.
Ø Alloy: A homogeneous mixture of two or more metal (or a non-metal) is called an alloy.
Ø Why are alloys made: Pure metals generally do not have all the properties of a good meta,
such as malleability, ductility, tensile strength, hardness, resistance to corrosion, etc.,
However, one or more of the above properties can be improved by melting two or more
metals (or a non-metal) in some fixed proportion and allowing the molten product to cool
at room temperature. Such a product is called an alloy.
Ø Characteristics of a mixture
The components of a mixture may be present in it in any proportion.
Ø For example, a sugar solution may contain one spoonful per cup and another may contain
two spoonful per cup, through both of them are sugar-water mixtures.
The components of a mixture coexist without chemically reacting with one another.
Ø For example, hydrogen mixture with oxygen without reacting with it. (A chemical
reaction will take place only when a mixture of the two gases is kindled or when an
electric spark is passed through it.)
The components of a mixture retain their properties.
Ø For example, a sugar solution will be sweet and watery. And a solution of salt will be
salty and watery.
The components of a mixture can be separated by physical means.
Ø For example, soil and water can be separated from muddy water by filtration.
Separating the components of mixtures
Ø Mixture are impure substances, Hence, in order to obtain a pure of a desirable substance
or to remove an undesirable substance from a mixture, we often need to separate the
components of a mixture.
Ø It is only by doing so that we obtain common salt from sea water; petrol, diesel and
kerosene from crude oil; and drinking water from ordinary water.
Ø For separating the components of a mixture, we take advantage of their characteristic
properties like colour, size, shape, solubility, melting point, boiling point etc.
Some useful compounds:
Ø Common salt–Common salt is chemically sodium chloride. It is mostly obtained by the
evaporation of sea water. The common salt so obtained, is called crude salt, as it contains
clay and sand particles. Crude salt is generally purified by dissolving it in water and by
recrystallisation. It is then mixed with sodium or potassium iodide and marketed for
human consumption.
Ø Hydrochloric Acid–Hydrochloric acid is chemically hydrogen chloride solution. It is
very corrosive in nature. It is produced in the stomach walls of most of the animals and
helps in killing the germs and bacteria present in the food. Hydrochloric acid is prepared
industrially heating common salt and concentrated sulphuric acid.
Ø Fertilisers – the materials added to the soil, so as to make up for the deficiency of
essential nutrients are called fertilizers.

Ø Silicon compounds – Silicon compounds are the compounds of non-metal silicon.
Ø Blue Vitriol – Blue vitriol is hydrated copper sulphate (CuSO4. 5H2O). It is prepared by
dissolving copper oxide or copper carbonate or copper sulphide in dilute sulphuric acid.
Ø Marble or Limestone – Limestone or marble is chemically calcium carbonate. It is a
metamorphic rock formed from the sea shells.
Ø Zincite or Zinc oxide – It is prepared by strongly heating naturally occurring zinc
carbonate. It is extensively used in the manufacture of paints. It is also used as a raw
material in the extraction of zinc metal.
Ø Gypsum – Gypsum is a naturally occurring mineral. It is chemically calcium sulphate-
dihydrate (CaSO4. 2H2O).
Ø Plaster of pairs – It is chemically calcium sulphate hemihydrates
It is obtained by heating gypsum at controlled temperature.
( )
4 2
2
1
CaSO . H O .
2
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1. What are pure substances? Give two examples.
2. What are the types of pure substances? Give one example of each type.
3. Which of the following are “pure substances”?
Ice, Milk, Iron, Hydrochloric acid, Calcium oxide, Mercury, Brick wood, Air etc.
4. What is the other name of impure substances? Give two examples.
5. Explain why hydrogen and oxygen are considered as elements whereas water is not
considered as an element.
6. The substance which is not compound
(A) marble (B) limestone
(C) diamond (D) chalk
7*. The substance that is not pure
(A) brass (B) copper wire
(C) aluminium sheet (D) wrought iron
8*. The substance that has only one kind of atom is
(A) Marsh gas (B) dry ice
(C) well water (D) ozone
9*. Air is
(A) an element (B) a compound
(C) mixture (D) alloy
10. The substance that breaks into simpler substances on simple heating
(A) Carbon (B) Sulphur
(C) Phosphorous (D) zinc Carbonate

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1. Classify the following materials as homogeneous mixtures and heterogeneous mixtures.
Soda water, Wood, Air, Soil, Vinegar, Alcohol and water mixture, Petrol and water
mixture, Chalk and water mixture, sugar and water mixture, copper sulphate solution.
2. Why is a solution called True solution?
3. How can a saturated solution be made unsaturated?
4. You are given two liquids, one a solution and the other a compound. How will you
distinguish the solution from the compound?
5. Name the technique to separate
(i) Butter from curd
(ii) Salt from seawater
(iii) Camphor from salt
(iv) Pure copper sulphate from impure copper sulphate.
6. The mixture that is not homogeneous
(A) Sugar solution (B) Brine
(C) Soil (D) Mountain air
7*. The method that can be used to separate a homogeneous mixture of two liquids
(A) Decantation (B) Filtration
(C) Fractional crystallization (D) Fractional distillation
8*. A true solution can be separated into its components by
(A) evaporation (B) Boiling
(C) sedimentation (D)fractional distillation
9*. Soda water is an example of a solution of
(A) gas in solid (B) gas in liquid
(C) liquid in gas (D) liquid in liquid
10. Cloud is an example of a solution of
(A) liquid in liquid (B) gas in gas
(C) liquid in gas (D) gas in liquid
11*. Dry air is an example of a solution of
(A) gas in gas (B) gas in liquid
(C) liquid in gas (D) solid in liquid
12*. Which is correct about solution?
(A) solutions are homogeneous mixtures
(B) solution formation is a physical process
(C) the constituent in larger proportion is called solvent
(D) all of these
13. Which is incorrect about solutions?
(A) solutions are heterogeneous mixtures (B) solution have definite MP and BP
(C) the constituent can not be separated easily (D) all of these

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1. What is difference between colloids and suspensions?
2. Explain what happens when a beam of light is passed through a colloidal solution?
3. Comment on “Smoke and fog are aerosols”
4. How much water should be mixed with 12 ml of alcohol so as to obtain 12% alcohol
solution?
5. Can physical and chemical change occur together? Illustrate your answer.
6*. Fractional crystallization uses the difference in _______ of the components of a mixture.
(A) Rates of diffusion (B) Density
(C) Melting point (D) Solubility
7. Filtration can be used if solute particle size is
(A) greater than 10-7
cm (B) equal to 10 Å
(C) smaller than 10 Å (D) smaller than 10-8
cm
8*. A mixture of rice and sand particles can be separated by:
(A) crystallization (B) hand pricking
(C) centrifugation (D) All
9. We can remove salts from a solution by using the process of
(A) crystallization (B) evaporation
(C) centrifugation (D) All
10. When a substance change its state from solid to liquid, it is called
(A) Melting (B) Evaporation
(C) Sublimation (D) none of these

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1. Gunpowder is a mixture of nitre, sulphur and carbon. How will you separate its
constituents.
2. Classify the following as physical or chemical changes.
(i) Condensation of steam
(ii) Rusting of iron
(iii) Growth of a plant
(iv) Breaking of a glass tumbler
(v) Digestion of food
3. How will you bring about the following separations?
(i) Fine mud particles floating in water
(ii) Carbon particles present in smoke
4. What is chromatography? Sate its two applications.
5. Water purification methods are used in a large scale at water works? Name the substance
which is added to kill germs in the drinking water supply.
6*. The change in which a new substance is formed may be a
(i) physical change (ii) Chemical change (iii) nuclear reaction
(A) (i) only (B) (i) or (ii)
(C) (ii) only (D) (ii) or (iii)
7. A change in which there is no change in chemical properties is:
(A) physical change (B) nuclear change
(C) chemical change (D) none of these
8*. The principle of chromatography is:
(A) liquids with lower boiling points boil off first
(B) salts with lower solubilities crystallize out from saturated solution when cooled
(C) the rate of diffusion of liquids varies
(D) all liquids are not miscible in water
9. Air is a solution of
(A) nitrogen in oxygen (B) oxygen in nitrogen
(C) in oxygen (D) inert gases in oxygen
10*. Compounds can be broken into simpler substances by
(A) heating (B) nuclear fission
(C) dissolution (D) All of three
11. The element, compound and mixture in the given list is: cobalt, ink, milk, marble, ozone
(A) cobalt is an element, ink and milk are mixtures, ozone and marble are compounds
(B) cobalt is an element, marble and milk are mixtures, ink and ozone are compounds
(C) cobalt and ozone are elements, ink is a mixture, marble and milk are compounds
(D) cobalt is an element, milk is a mixture, ink, marble and ozone are compounds
12*. A mixture of sulphur dioxide (BP is 10°C) and oxygen (BP is –183°C) can be separated
economically by
(A) cooling to BP of oxygen (B) absorbing the gases
(C) cooling to BP of SO2 (D) reacting one of the gases
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Straight Objective Type
This section contains multiple choice questions. Each question has 4 choices (A), (B), (C), (D), out of which ONLY
ONE is correct. Choose the correct option.
1. ‘Ion’ is a three-letter word. It means [NSO – 2007]
(A)A mixture of iodine, oxygen and nitrogen
(B) An alloy of iron
(C) A charged particle
(D)A form of light
2. A saturated solution can be converted to unsaturated by
(A) increasing solvent quantity (B) always by increasing temperature
(C) increasing solute quantity (D) all of these
3. Fractional distillation makes use of the difference in _____.
(A) rates of dissolution (B) purity
(C) solubilities (D) boiling point
4. To separate a mixture of kerosene and petrol the method that can be used as:
(A) distillation (B) fractional distillation
(C) boiling (D) filtration
5.
[NSO – 2007]
Identify p, q, r, s, t and u
p q r s t u
(A)Sublimation Solidification Condensation Vaporisation Fusion Sublimation
(B) Sublimation Sublimation Vaporisation Condensation Fusion Solidification
(C) Fusion Solidification Vaporisation Condensation Vaporisation Sublimation
(D)Fusion Sublimation Solidification Condensation Vaporisation Sublimation
6. When a mixture is boiled for separating into its constituents, the constituent that is
separated last has
(A) lower boiling point (B) higher boiling point
(C) can have lower or higher boiling point (D) None of these
7. A mixture of iodine and Sodium iodide can be separated by
(A) fractional distillation (B) sublimation
(C) chromatography (D) fractional crystallization
Liquid
Solid Gas
p
q s
r
t
u

8. Mixture of NaNO3 from its aqueous solution can be separated by
(A) boiling (B) fractional crystallization
(C) chromatography (D) decantation of filtration
9. A salt solution is obtained by dissolving 20 g of salt in 80 g of water. What must be done
to make this salt solution 60% ? [NSO – 2008]
(A)Add 100 g of water to the solution
(B) Add 100 g of the salt to the solution
(C) Add 50 g of water and 50 g of salt to the solution
(D)Both (A) and (B)
10. Identify X and Y in the given figure [NSO – 2008]
X Y
(A)Mixture of naphthalene and anthracene Solid naphthalene
(B) Mixture of NaCl and water Solid NaCl
(C) Mixture of NaCl and anthracene Solid anthracene
(D)Mixture of sugar and NaCl Solid sugar
11. Statement – I : Evaporation causes cooling. [NSO – 2009]
Statement – II : Particles of liquid absorb energy from the surrounding to regain the
energy lost during evaporation.
(A)Both statement – I and Statement – II is the correct explanation for statement – I
(B) Both statement – I and statement – II are true but statement – II is not the correct
explanation for statement – I
(C) Statement – I is true and statement – II is false
(D)Statement – I is false and statement – II is true.
12. Column II gives method to separate phases mentioned in column I. Match them and select
the correct answer from the codes given below : [NSO – 2009]
Column I Column II
(a) Miscible liquids (p) Distillation
(b) Immiscible liquids (q) Crystallization
(c) Pure copper sulphate from an impure sample (r) Sublimation
(d) Salt and ammonium chloride (s) Separating funnel
(A)(a) – (q), (b) – (s), (c) – (p), (d) – (r)
(B) (a) – (p), (b) – (s), (c) – (q), (d) – (r)
(C) (a) – (r), (b) – (s), (c) – (p), (d) – (q)
(D)(a) – (r), (b) – (s), (c) – (q), (d) – (p)
Multiple Correct Answer Type
This section contains multiple choice questions. Each question has 4 choices (A), (B), (C), (D), out of which ONE or
MORE is correct. Choose the correct options.

13. Which of the following is true for colloidal solutions.
(A) they are in two phase system (B) they can pass through filter paper
(C) they show tyndal effect (D) they show Brownian motion
14. Which of the following statement is correct.
(A) mixture can be homogenous (B) compounds are always homogenous
(C) compounds of mixture can be separated by physical methods
(D) in a compound only one elements is present
15. Which is correct for common salt ?
(A) it is chemically sodium chloride
(B) it is obtained by evaporation of sea water
(C) it may contain KI
(D) it may contain NaI
16. Which is correct for zincite.
(A) it is ZnO (B)it is used in manufacture of paints
(C) it is prepared by ZnSO4 (D) None
17. Brass is
(A) compound (B) mixture
(C) element (D) an alloy
Linked Comprehension Type
This section contains paragraphs. Based upon each paragraph multiple choice questions have to be answered. Each
question has 4 choices (A), (B), (C) and (D), out of which ONLY ONE is correct. Choose the correct option.
A homogeneous mixture is true solution in which the solute particle size is very small –
10Å. Due to this, solute particles cannot be seen with naked eye and they cannot be
separated by filtration,. Homogeneous mixture are clear and transparent. Heterogeneous
mixtures can be classified into either colloids or suspensions depending on the particle
size. Colloids are solutions in which the solute particle size is between 10 Å and 1000 Å.
Suspensions are solutions in which the particle size is greater then 1000 Å. Human beings
can see the particles whose particle size is greater than 10 Å.
18. The order of solute particle size is
(A) true solution <suspension<colloid (B) true solution> suspension > colloid
(C) true-solution > colloid > suspension (D) true solution < colloid < suspension
19. Filtration can be used if solute particle size is ……………..
(A) greater than 10-7
(B) equal to Å
(C) smaller than 1.0 Å cm (D) smaller than 10-8
cm
20. A true solution can be separated into its components by
(A) evaporation (B) boiling
(C) sedimentation (D) fractional distillation
Assertion – Reason Type questions
This section contains certain number of questions. Each question contains Statement – 1 (Assertion) and Statement –
2 (Reason). Each question has 4 choices (A), (B), (C) and (D) out of which ONLY ONE is correct Choose the
correct option.
(A) Statement–1 is True, Statement–2 is True; Statement–2 is a correct explanation for Statement–1.

(B) Statement–1 is True, Statement–2 is True; Statement–2 is not a correct explanation for Statement–1.
(C) Statement–1 is True, Statement–2 is False.
(D) Statement–1 is False, Statement–2 is True.
21. Statement-1: A mixture is not a pure substance.
Statement-2: The simple components of a mixture taken separately are impure.
22. Statement -1: A compound will have the properties of the elements present in it
Statement -2: The elements in a compound are combined chemically.
Matrix Match Type
This section contains Matrix-Match Type questions. Each question contains statements given in
two columns which have to be matched. Statements (A, B, C, D) in Column–I have to be matched
with statements (p, q, r, s) in Column–II. The answers to these questions have to be appropriately
bubbled as illustrated in the following example.
If the correct matches are A-p, A-s, B-q, B-r, C-p, C-q and D-s, then the correctly bubbled 4 ´ 4
matrix should be as follows:
23. Column –I Column –II
(A) gas to solid (p) Chemical change
(B) molecules ® Helium atoms (q) Nuclear fission
(C) (r) Nuclear fusion
(D) Uranium ® Lead (s) Physical change
24. Column –I Column –II
(A) Salt in water (p) Solid in solid
(B) Soda water (q) Gas in gas
(C) Air (r) Solid in liquid
(D) Bronze (s) Gas in liquid
Integer Answer Type
25. How many molecules of water is present in blue vitriol.
26. How many elements are present in brass.
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KEY & HINTS
Is Matter Around Us Pure
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1. A pure substance is one which is
made up of only one kind of particle
(atoms or molecules).
For example sulphur element is made
up of only one kind of particles (i..e
sulphur atoms). Similarly, water is
made up of only one kind of particles
(i.e. water molecules).
2. The two types of pure substances are
“Elements” (e.g. hydrogen) and
“compounds” (e.g. water)
3. Ice, Iron, Hydrochloric acid, calcium
oxide, Mercury.
4. “Mixture” is the other name of
impure substances. A mixture
contains two or more pure substances
mixed together. For example, salt
solution is a mixture of two pure
substances “salt” and “water”, Milk
is the mixture of water, fat and
proteins.
5. Hydrogen and oxygen are considered
as elements because they are made
up of only one kind of atoms. While
water is made up of two types (i.e.
hydrogen and oxygen) of elements.
Therefore water is not considered as
an element.
6. (C)
7. (A)
8. (D)
9. (C)
10. (D)
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1. Homogeneous mixture: Alcohol and
water, sugar and water, copper
sulphate solution, soda water, air,
vinegar.
Heterogeneous mixture: Wood, soil,
petrol and water, chalk and water.
2. A true solution is a homogeneous
mixture. The substances like salt,
sugar etc which dissolve in water
completely are said to be soluble in
water. Thus only soluble substances
form true solutions.
3. A saturated solution can be made
unsaturated by the following two
ways:
(i) By increasing the temperature of
the solution. When a saturated
solution is heated, solubility of the
solute increases and hence the
solution becomes unsaturated.
(ii) By adding more of the solvent or
by diluting.
4. In order to distinguish between the
two, we should evaporate them
separately. The liquid which
evaporates completely, leaving no
residue, is a pure compound. On the
other hand, the liquid which leaves
behind a residue on evaporation, is a
solution or mixture.
5. (i) Centrifugation
(ii) Evaporation
(iii) Sublimation
(iv) Crystallization
6. (C)
7. (D)
8. (B)
9. (B)
10. (C)
11. (A)
12. (D)
13. (D)

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1. Colloid: A colloid is a kind of
solution in which the size of solute
particles is intermediate between
those intrue solutions and those in
suspensions. e.g. soap solution,
starch solution, Ink, Blood, Jelly and
solutions of synthetic detergents.
Suspensions: A suspension is a
heterogeneous mixture in which the
small particles of a solid are spread
throughout in a liquid without
dissolving in it. e.g. chalk-water
mixture, muddy water, milk of
magnesia, sand particles suspended
in water, flour in water.
2. When a beam of light is passed
through colloidal solution, the
particles scatter light. This is known
as Tyndall effect.
3. A colloidal sol in which air is the
dispersion medium is called the
aerosol. Smoke is a colloidal sol of
solid carbon particles in air while fog
is a colloidal sol of moisture (water
droplets) in air. Therefore both are
aerosols.
4. 12% alcohol solution means 12 ml of
alcohol is present in 100 ml of
solution.
Volume of alcohol = 12 ml (given)
Volume of water
= 100 – 12 = 88 ml
5. In some cases, physical and chemical
changes occurs together. One such
example is burning of candle. The
solid wax present in the candle first
changes into liquid state and then
into the vapour state. Both changes
are physical changes. The wax
vapours then combine with oxygen
of the air to form a mixture of carbon
dioxide and water. This involves a
chemical change. Thus, burning of
candle involves both physical and
chemical change.
6. (D)
7. (A)
8. (B)
9. (B)
10. (A)
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1. Nitre (KNO3) is soluble in water,
sulphur is soluble in
carbondisulphide while carbon is
soluble in neither of the two. Thus,
the given mixture is first stirred with
water and then filtered. Nitre
dissolves while sulphur and carbon
remain on the filter paper as residue.
Evaporation of water from the filtrate
gives nitre.
The residue consisting of sulphur and
carbon is shaken with
carbondisulphide and filtered.
Sulphur dissolves while carbon
remains on the filter paper as residue.
Evaporation of carbondisulphide
from the filtrate gives sulphur.
2. (i) Physical
(ii) Chemical
(iii) Chemical
(iv) Chemical
(v) Chemical
3. (i) By coagulation using alum and
then filtering.
(ii) By passing smoke through
electric plates maintained at a high
potential difference .The colloidal
particles of carbon get neutralized
and fall down while air escapes out.
4. Chromatography is a technique of
separating two or more dissolved
solids which are present in a solution
in very small quantities.
Paper chromatography is the simplest
form of chromatography through
which blank ink (mixture of several
coloured substances) can be
separated.
Applications: (i) It is used to separate
solutions of coloured substances

(dyes and pigments). (ii) It is used in
forensic science to detect and
identify trace amounts of substances
(like poisons) in the contents of
bladder or stomach.
5. The methods like sedimentation,
decantation, loading, filtration and
chlorination etc are used to remove
undesirable materials from water in
water works. Chlorine is added to
water to kill the germs present in it.
6. (D)
7. (A)
8. (C)
9. (B)
10. (D)
11. (A)
12. (C)
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1. (C)
2. (A)
3. (D)
4. (B)
5. (C)
6. (B)
7. (B)
8. (A)
9. (B)
10. (C)
11. (A)
12. (B)
13. (A, B, C, D)
14. (A, B)
15. (A, B, C, D)
16. (A, B)
17. (B, D)
18. (D)
19. (A)
20. (B)
21. (C)
22. (D)
23. (A® s), (B® r) (C® p), (D® q)
24. (A® r), (B® s) (C® q), (D® p)
25. 5
CuSO4.5H2O
26. 2
Cu and Zn

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