Selina Textbook Solutions: Elements, Compounds and Mixtures | Chemistry Class 9 ICSE PDF Download

 Page 1


Chapter 3. Elements, Compounds and Mixtures
Exercise 3(A)
Solution 1.
An element is a pure substance composed of only one kind of atom. Example: C, H, O, 
Na, Ca, N etc.
Characteristics of an element:
1. An element is made up of only one kind of atoms.
2. An element is pure and homogeneous substance.
3. An element has fixed melting and boiling points.
4. An atom is the smallest particle of an element which takes part in a chemical 
reaction.
5. An element may chemically react with another elements or compounds.
6. An element can occur in solid, liquid or gaseous state.
7. The molecules are made up of one or more atoms of the same or different 
elements.
Solution 2. 
Solution 3.
Two elements which show exception to the properties of:
Page 2


Chapter 3. Elements, Compounds and Mixtures
Exercise 3(A)
Solution 1.
An element is a pure substance composed of only one kind of atom. Example: C, H, O, 
Na, Ca, N etc.
Characteristics of an element:
1. An element is made up of only one kind of atoms.
2. An element is pure and homogeneous substance.
3. An element has fixed melting and boiling points.
4. An atom is the smallest particle of an element which takes part in a chemical 
reaction.
5. An element may chemically react with another elements or compounds.
6. An element can occur in solid, liquid or gaseous state.
7. The molecules are made up of one or more atoms of the same or different 
elements.
Solution 2. 
Solution 3.
Two elements which show exception to the properties of:
Metals :-
1. Mercury (Hg) is liquid at room temperature.
2. Tungsten (W) is a poor conductor of electricity.
Non-metals:-
1. Iodine is lustrous.
2. Carbon is ductile.
Solution 4.
(a) Molecule: A molecule is the smallest particle of a pure substance (element or 
compound), and it has all the properties of that substance. It is composed of atoms. It is 
capable of existing in a free state. 
Example: O
2
, H
2
, Cl
2
 are molecules.
(b) Atomicity: Atomicity is the number of atoms present in a molecule of an element.
(c) Compound: A compound is a pure substance composed of two or more elements 
combined chemically in a fixed proportion by mass. The properties of compounds are 
different from the properties of their constituent elements. Example: H
2
O, CO
2
 etc.
Solution 5.
(a) A diatomic element Nitrogen (N
2
)
(b) A tetratomic element Phosphorus (P)
(c) Monoatornic element Helium (He)
(d) Lustrous non-metal Iodine
(e) Liquid non-metal Bromine (Br
2
)
(f) A gas filled in electric bulbs Argon (Ar)
(g) A liquid metal Mercury (Hg)
(h) A non metal conductor of 
electricity
Graphite
(i) A metal non malleable and non 
ductile
Zinc (Zn)
(j) A lustrous non metal Graphite
Solution 6.
(i) Sodium chloride is obtained when sodium chemically combines with chlorine in ratio of 
23:355 by weight. 
(ii) When molten sodium chloride is subjected to electrolysis, the ratio by weight of 
sodium and chlorine librated at electrodes is 2:3.
Solution 7.
Page 3


Chapter 3. Elements, Compounds and Mixtures
Exercise 3(A)
Solution 1.
An element is a pure substance composed of only one kind of atom. Example: C, H, O, 
Na, Ca, N etc.
Characteristics of an element:
1. An element is made up of only one kind of atoms.
2. An element is pure and homogeneous substance.
3. An element has fixed melting and boiling points.
4. An atom is the smallest particle of an element which takes part in a chemical 
reaction.
5. An element may chemically react with another elements or compounds.
6. An element can occur in solid, liquid or gaseous state.
7. The molecules are made up of one or more atoms of the same or different 
elements.
Solution 2. 
Solution 3.
Two elements which show exception to the properties of:
Metals :-
1. Mercury (Hg) is liquid at room temperature.
2. Tungsten (W) is a poor conductor of electricity.
Non-metals:-
1. Iodine is lustrous.
2. Carbon is ductile.
Solution 4.
(a) Molecule: A molecule is the smallest particle of a pure substance (element or 
compound), and it has all the properties of that substance. It is composed of atoms. It is 
capable of existing in a free state. 
Example: O
2
, H
2
, Cl
2
 are molecules.
(b) Atomicity: Atomicity is the number of atoms present in a molecule of an element.
(c) Compound: A compound is a pure substance composed of two or more elements 
combined chemically in a fixed proportion by mass. The properties of compounds are 
different from the properties of their constituent elements. Example: H
2
O, CO
2
 etc.
Solution 5.
(a) A diatomic element Nitrogen (N
2
)
(b) A tetratomic element Phosphorus (P)
(c) Monoatornic element Helium (He)
(d) Lustrous non-metal Iodine
(e) Liquid non-metal Bromine (Br
2
)
(f) A gas filled in electric bulbs Argon (Ar)
(g) A liquid metal Mercury (Hg)
(h) A non metal conductor of 
electricity
Graphite
(i) A metal non malleable and non 
ductile
Zinc (Zn)
(j) A lustrous non metal Graphite
Solution 6.
(i) Sodium chloride is obtained when sodium chemically combines with chlorine in ratio of 
23:355 by weight. 
(ii) When molten sodium chloride is subjected to electrolysis, the ratio by weight of 
sodium and chlorine librated at electrodes is 2:3.
Solution 7.
Type Substances Reason
Element Chlorine, Sulphur
They cannot be split up 
into any simpler 
substance.
Compound Carbon dioxide
It can be produces by 
chemical analysis of two 
or more simpler 
substances with different 
properties.
Mixture
Honey, milk, sea water, 
gun powder, apple 
juice, brine, syrup and 
bronze
These are produced by 
mere mixing of two or 
more substances in any 
proportions by weight.
Solution 8.
(a) This is because molecules have all the properites of that substance and is capable of 
existing in a free state, molecules are composed of atoms.
(b)
Element Compund
1. It is a pure substance which 
cannot be converted into simpler 
substances by any physical or 
chemical means.
1. It is a pure substance made up 
two or more elements combined 
chemically in a fixed ratio.
2. It is made up of only one kind 
of atoms.
2. It is made up of two or more 
different kinds of atoms.
3. The molecules are made up of 
one or more atoms.
3. The molecules are made up of 
two or more atoms.
Solution 9.
It is true that the elements can form different compounds. 
Example: Hydrogen and oxygen combine to give two different compounds, water (H
2
O) 
and hydrogen peroxide (H
2
O
2
) under different conditions.
Solution 10.
Characteristics of a compound
1. A compound is made up of one or more atoms of the same or different elements.
2. It has a homogeneous composition.
3. In a compound the elements are present in a fixed ratio by mass.
4. The properties of a compound are different from those of its Constituent elements.
Page 4


Chapter 3. Elements, Compounds and Mixtures
Exercise 3(A)
Solution 1.
An element is a pure substance composed of only one kind of atom. Example: C, H, O, 
Na, Ca, N etc.
Characteristics of an element:
1. An element is made up of only one kind of atoms.
2. An element is pure and homogeneous substance.
3. An element has fixed melting and boiling points.
4. An atom is the smallest particle of an element which takes part in a chemical 
reaction.
5. An element may chemically react with another elements or compounds.
6. An element can occur in solid, liquid or gaseous state.
7. The molecules are made up of one or more atoms of the same or different 
elements.
Solution 2. 
Solution 3.
Two elements which show exception to the properties of:
Metals :-
1. Mercury (Hg) is liquid at room temperature.
2. Tungsten (W) is a poor conductor of electricity.
Non-metals:-
1. Iodine is lustrous.
2. Carbon is ductile.
Solution 4.
(a) Molecule: A molecule is the smallest particle of a pure substance (element or 
compound), and it has all the properties of that substance. It is composed of atoms. It is 
capable of existing in a free state. 
Example: O
2
, H
2
, Cl
2
 are molecules.
(b) Atomicity: Atomicity is the number of atoms present in a molecule of an element.
(c) Compound: A compound is a pure substance composed of two or more elements 
combined chemically in a fixed proportion by mass. The properties of compounds are 
different from the properties of their constituent elements. Example: H
2
O, CO
2
 etc.
Solution 5.
(a) A diatomic element Nitrogen (N
2
)
(b) A tetratomic element Phosphorus (P)
(c) Monoatornic element Helium (He)
(d) Lustrous non-metal Iodine
(e) Liquid non-metal Bromine (Br
2
)
(f) A gas filled in electric bulbs Argon (Ar)
(g) A liquid metal Mercury (Hg)
(h) A non metal conductor of 
electricity
Graphite
(i) A metal non malleable and non 
ductile
Zinc (Zn)
(j) A lustrous non metal Graphite
Solution 6.
(i) Sodium chloride is obtained when sodium chemically combines with chlorine in ratio of 
23:355 by weight. 
(ii) When molten sodium chloride is subjected to electrolysis, the ratio by weight of 
sodium and chlorine librated at electrodes is 2:3.
Solution 7.
Type Substances Reason
Element Chlorine, Sulphur
They cannot be split up 
into any simpler 
substance.
Compound Carbon dioxide
It can be produces by 
chemical analysis of two 
or more simpler 
substances with different 
properties.
Mixture
Honey, milk, sea water, 
gun powder, apple 
juice, brine, syrup and 
bronze
These are produced by 
mere mixing of two or 
more substances in any 
proportions by weight.
Solution 8.
(a) This is because molecules have all the properites of that substance and is capable of 
existing in a free state, molecules are composed of atoms.
(b)
Element Compund
1. It is a pure substance which 
cannot be converted into simpler 
substances by any physical or 
chemical means.
1. It is a pure substance made up 
two or more elements combined 
chemically in a fixed ratio.
2. It is made up of only one kind 
of atoms.
2. It is made up of two or more 
different kinds of atoms.
3. The molecules are made up of 
one or more atoms.
3. The molecules are made up of 
two or more atoms.
Solution 9.
It is true that the elements can form different compounds. 
Example: Hydrogen and oxygen combine to give two different compounds, water (H
2
O) 
and hydrogen peroxide (H
2
O
2
) under different conditions.
Solution 10.
Characteristics of a compound
1. A compound is made up of one or more atoms of the same or different elements.
2. It has a homogeneous composition.
3. In a compound the elements are present in a fixed ratio by mass.
4. The properties of a compound are different from those of its Constituent elements.
Solution 11.
The properties of compounds are different from the properties of their constituent 
elements. Example: H
2
O, FeS, C
12
H
22
O
11
1. H
2
O: Water is a liquid, while constituent elements, Hydrogen and Oxygen are 
gases.
2. FeS: Iron sulphide is a black substance, not attracted by a magnet and insoluble in 
carbon disulphide. While constituent elements, Iron is grey colored, attracted by a 
magnet. Sulphur is a yellow colored, soluble in carbon disulphide.
3. C
12
H
22
O
11
: Sugar is a crystalline solid, sweet to taste and soluble in water. But, its 
constituent elements, Carbon, is black insoluble solid. Hydrogen and Oxygen are 
invisible and odorless gases.
Solution 12.
A compound is a pure substance composed of two or more elements combined chemically 
in fixed proportions by mass. The properties of a compound are different 
from the properties of their constituent elements.
1. H
2
O: Water is a liquid, while constituent elements, Hydrogen and Oxygen are 
gases.
2. FeS: Iron sulphide is a black substance, not attracted by a magnet and insoluble in 
carbon disulphide. While constituent elements, Iron is grey colored, attracted by a 
magnet. Sulphur is a yellow colored, soluble in carbon disulphide.
3. C
12
H
22
O
11
: Sugar is a crystalline solid, sweet to taste and soluble in water. But, its 
constituent elements, Carbon, is black insoluble solid. Hydrogen and Oxygen are 
invisible and odorless gases.
Solution 13.
A mixture cannot be represented by a chemical formula because constituents present in a 
mixture are in any ratio and they are not chemically united.
Solution 14.
(a) Air 
(b) Concrete 
(c) Milk
Solution 15.
Elements Compounds Mixtures
Mercury
Sugar, Distilled water, 
Alcohol, Nitre, Washing 
soda, Rust, Marble
Air, Milk, Wax, Sea-
water, Paint, Brass, 
Bread, Soap, Tap 
water
Solution 16.
Page 5


Chapter 3. Elements, Compounds and Mixtures
Exercise 3(A)
Solution 1.
An element is a pure substance composed of only one kind of atom. Example: C, H, O, 
Na, Ca, N etc.
Characteristics of an element:
1. An element is made up of only one kind of atoms.
2. An element is pure and homogeneous substance.
3. An element has fixed melting and boiling points.
4. An atom is the smallest particle of an element which takes part in a chemical 
reaction.
5. An element may chemically react with another elements or compounds.
6. An element can occur in solid, liquid or gaseous state.
7. The molecules are made up of one or more atoms of the same or different 
elements.
Solution 2. 
Solution 3.
Two elements which show exception to the properties of:
Metals :-
1. Mercury (Hg) is liquid at room temperature.
2. Tungsten (W) is a poor conductor of electricity.
Non-metals:-
1. Iodine is lustrous.
2. Carbon is ductile.
Solution 4.
(a) Molecule: A molecule is the smallest particle of a pure substance (element or 
compound), and it has all the properties of that substance. It is composed of atoms. It is 
capable of existing in a free state. 
Example: O
2
, H
2
, Cl
2
 are molecules.
(b) Atomicity: Atomicity is the number of atoms present in a molecule of an element.
(c) Compound: A compound is a pure substance composed of two or more elements 
combined chemically in a fixed proportion by mass. The properties of compounds are 
different from the properties of their constituent elements. Example: H
2
O, CO
2
 etc.
Solution 5.
(a) A diatomic element Nitrogen (N
2
)
(b) A tetratomic element Phosphorus (P)
(c) Monoatornic element Helium (He)
(d) Lustrous non-metal Iodine
(e) Liquid non-metal Bromine (Br
2
)
(f) A gas filled in electric bulbs Argon (Ar)
(g) A liquid metal Mercury (Hg)
(h) A non metal conductor of 
electricity
Graphite
(i) A metal non malleable and non 
ductile
Zinc (Zn)
(j) A lustrous non metal Graphite
Solution 6.
(i) Sodium chloride is obtained when sodium chemically combines with chlorine in ratio of 
23:355 by weight. 
(ii) When molten sodium chloride is subjected to electrolysis, the ratio by weight of 
sodium and chlorine librated at electrodes is 2:3.
Solution 7.
Type Substances Reason
Element Chlorine, Sulphur
They cannot be split up 
into any simpler 
substance.
Compound Carbon dioxide
It can be produces by 
chemical analysis of two 
or more simpler 
substances with different 
properties.
Mixture
Honey, milk, sea water, 
gun powder, apple 
juice, brine, syrup and 
bronze
These are produced by 
mere mixing of two or 
more substances in any 
proportions by weight.
Solution 8.
(a) This is because molecules have all the properites of that substance and is capable of 
existing in a free state, molecules are composed of atoms.
(b)
Element Compund
1. It is a pure substance which 
cannot be converted into simpler 
substances by any physical or 
chemical means.
1. It is a pure substance made up 
two or more elements combined 
chemically in a fixed ratio.
2. It is made up of only one kind 
of atoms.
2. It is made up of two or more 
different kinds of atoms.
3. The molecules are made up of 
one or more atoms.
3. The molecules are made up of 
two or more atoms.
Solution 9.
It is true that the elements can form different compounds. 
Example: Hydrogen and oxygen combine to give two different compounds, water (H
2
O) 
and hydrogen peroxide (H
2
O
2
) under different conditions.
Solution 10.
Characteristics of a compound
1. A compound is made up of one or more atoms of the same or different elements.
2. It has a homogeneous composition.
3. In a compound the elements are present in a fixed ratio by mass.
4. The properties of a compound are different from those of its Constituent elements.
Solution 11.
The properties of compounds are different from the properties of their constituent 
elements. Example: H
2
O, FeS, C
12
H
22
O
11
1. H
2
O: Water is a liquid, while constituent elements, Hydrogen and Oxygen are 
gases.
2. FeS: Iron sulphide is a black substance, not attracted by a magnet and insoluble in 
carbon disulphide. While constituent elements, Iron is grey colored, attracted by a 
magnet. Sulphur is a yellow colored, soluble in carbon disulphide.
3. C
12
H
22
O
11
: Sugar is a crystalline solid, sweet to taste and soluble in water. But, its 
constituent elements, Carbon, is black insoluble solid. Hydrogen and Oxygen are 
invisible and odorless gases.
Solution 12.
A compound is a pure substance composed of two or more elements combined chemically 
in fixed proportions by mass. The properties of a compound are different 
from the properties of their constituent elements.
1. H
2
O: Water is a liquid, while constituent elements, Hydrogen and Oxygen are 
gases.
2. FeS: Iron sulphide is a black substance, not attracted by a magnet and insoluble in 
carbon disulphide. While constituent elements, Iron is grey colored, attracted by a 
magnet. Sulphur is a yellow colored, soluble in carbon disulphide.
3. C
12
H
22
O
11
: Sugar is a crystalline solid, sweet to taste and soluble in water. But, its 
constituent elements, Carbon, is black insoluble solid. Hydrogen and Oxygen are 
invisible and odorless gases.
Solution 13.
A mixture cannot be represented by a chemical formula because constituents present in a 
mixture are in any ratio and they are not chemically united.
Solution 14.
(a) Air 
(b) Concrete 
(c) Milk
Solution 15.
Elements Compounds Mixtures
Mercury
Sugar, Distilled water, 
Alcohol, Nitre, Washing 
soda, Rust, Marble
Air, Milk, Wax, Sea-
water, Paint, Brass, 
Bread, Soap, Tap 
water
Solution 16.
On adding sulphuric acid to water we will get a Homogeneous Mixture (true solution).
This mixture will have different densities and boiling points depending upon the amounts 
of acid and water. The properties of acid and water will remain same even after mixing.
Solution 17.
Iron and sulphur when mixed, forms a mixture. It can be identified as follows:
A grayish yellow mixture will be produced.
All the individual properties of iron andsulphur will be shown separately in a 
mixture. Iron particles will be attracted by magnet. Sulphur will dissolve in carbon 
disulphide. Iron and sulphur when heated forms a compound.
It can be identified as follows:
A grey dark solid will be produced.
The compound formed is homogeneous.
It is neither attracted by a magnet nor it is soluble in carbon disulphide.
Solution 18.
Mixture Compound
1. It is obtained by the physical 
combination of either elements, or 
compounds, or both.
1. It is obtained by the chemical 
combination of more than one 
element.
2. The composition of elements 
present in a mixture is not fixed.
2. The composition of elements 
present in a compound is fixed.
3. It shows the properties of all its 
constituent elements.
3. The properties of a compound 
are different from those of its 
elements.
4. Its constituents can be 
separated using physical methods.
4. Its constituents can be 
separated by using only chemical 
and electrochemical methods.
5. The mixtures can be 
homogeneous or heterogeneous.
5. A compound is always 
homogeneous in nature.
Solution 19.
No.
Types of 
mixture
Example Nature
1. Two solids Bronze (Zn, Cu, Sn) Homogeneous
2. A solid in liquid Sugar in water, Salt 
in water, Iodine in 
alcohol
  
Homogeneous
  
Heterogeneous