chemistry case study and need a reference to help me learn.
Some basic concepts of chemistry
OBJECTIVES
The thorough study of this Unit would enable the reader to
. have a brief idea of history and importance of Chemistry:
• understand the measurement and the units used to express various physical and chemical quantities;
• learn Dalton’s atomic theory, Avogadro’s hypothesis, and the laws of chemical combination;
.
Have an idea of atoms, molecules, atomic masses, molecular masses and chemical equivalents;
. learn mole concept;
• carry out calculations involving mole concept, empirical and molecular formulae;
.
Balance the chemical equations and carry out calculations involving stoichiometry of chemical reactions.
Ymbolically, Chemistry may be defined as the
Sydne
Science of Rasas and colours. It colours our
Life with the discovery of different hidden colours
Of nature and all the Rasas necessary for making
Our life happier. The food we eat, the medicines we
Use for the prevention and cure of diseases, the natural
And synthetic fibres used for making fabrics, the various
Types of polymers used in all walks of day-to-day life, the
Cosmetics, the essences, the dye stuffs, all kinds of fuels
Used from kitchen stoves to rockets, all metals, non-metals
And many more things add colours to our life. All these
Things, whether of necessity or of luxury, are either given
By chemistry or related to it in some way or the other. The
Contributions and promises of chemistry for the welfare of
Human beings and for the advancement of society, both
In terms of necessities and luxuries, are many fold. Now-
a-days, the existence of an advanced civilization cannot
be thought of without chemistry. Therefore, the study of
chemistry is a must for the advancement of society and
for making mankind happier, healthier and wealthier.
The present form of chemistry that we study today
Has emerged mainly from the works of western chemists.
Perhaps, the first meaningful approach to chemistry was
Preparations, their properties, their accurate super-
Chemistry deals with the study of materials, their
Microscopic structures, their mutual interactions and
Their uses in all possible walks of life. It is concerned
With rocks, minerals, metals, non-metals, air, water,
Plants, animals, other materials of organic origin, earth
Atmosphere, interstellar atmosphere, etc. In brief, chemistry
Deals with everything which is essential for the betterment
Of human life and for adding colours to it.
1.1 A BRIEF HISTORY AND IMPORTANCE
1.1.1 A Brief History of Chemistry
In India, the study of chemistry is as old as the
Vedas are. Our ancient Rishis & Munis made significant
Contributions to chemistry. The ancient Vedic literature
Consists of valuable informations regarding the Rasa
Tantra, metals, metallurgy, combustion of matter and many
More things which may prove of immense importance to our
Modern practising chemists. In Vedic literature, the universe
Is supposed to be composed of Panchbhut, the five basic
Tatvas (elements)-Prithvi (the earth), Jala (the water),
Vayu (the air), Agni (the fire) and Akash (the sky). In Yajur
Veda, at one place the metals like iron, gold, copper, lead,
Tin have been mentioned along with stones, clay and sand.
OF CHEMISTRY
Made by Alchemists during the period 350-1500 A.D.
Alchemists were interested in discovering two things :
Nectar-a hypothetical syrup which could make man
Young and immortal and (ii) a philosopher’s stone-
A stone which could convert metals into gold. Alchemists
Were practically mad for acquiring these two things..
Unluckily they could not get either of these two things but
Their efforts made a valuable contribution to chemistry.
They devised various types of apparatus and discovered
Many processes such as extraction of gold by amalgamation
Process and preparation of caustic alkalis. We owe a lot to
These alchemists for their contributions to chemistry.
The period of 1500-1600 A.D. in chemistry is termed
As Iatro Chemistry Period. During this period a substantial
Study of gases was made. Robert Boyle is an important
Chemist of this period who extensively studied the
Behaviour of gases and gave an important law known asBoyle’s Law. During this period some chemical compounds of these elements-their preparation and properties
of medicinal value were also discovered.
studied in this branch.
Ernst Stahl (1660-1734) proposed a controversial
theory known as Phlogiston Theory. This theory survived for
about 100 years and the period of its survival in chemistry
is known as Phlogiston Period (1650-1774 A.D.). During
this period an extensive study of gases was carried out.
Several new gases were discovered and their behaviour
was studied.
The period beginning from the end of eighteenth
century is termed as Modern Period. In 1774, Joseph
Priestley discovered oxygen. Lavoisier, who is regarded
as father of modern chemistry, confirmed the discovery
made by Priestley and showed that oxygen is essential
for combustion. This explanation of combustion gave
an end to the Phlogiston Theory and to the Phlogiston
Period. In the beginning of nineteenth century, Laws of
chemical combination were formulated. In 1803, John
Dalton proposed his Atomic Theory. In 1869, Mendeleev,
a Russian scientist, made a significant contribution to
chemistry by introducing periodic law and by arranging the
elements in the form of a Periodic table. In 1833, Faraday
studied the passage of current through solutions and in
1881, Arrhenius proposed theory of ionisation.
The direction of research in chemistry took a new
turn when J.J. Thomson in 1896 succeeded in passing
electric discharge through gases at very low pressure.
and discovered electron. Almost at the same time
(1886) Goldstein discovered proton. In 1932, Sir James
Chadwick discovered neutron. With the advent of these
fundamental particles, the atom was no longer indivisible
as proposed by John Dalton. These researches gave new
dimensions to chemistry. With the advent of atomic number
by Henry Mosley in 1913, new concepts were conceived
and Mendeleev’s Periodic table was revised. The pioneer
work of Rutherford, Curies, etc., opened new vistas in the
field of nuclear chemistry.
The twentieth century may be said to be the
golden period of chemistry. During the last five decades
our knowledge of chemistry has increased manyfold.
Non-stop research work in chemistry is going on in almost
all the parts of the world. Highly sophisticated, both
manual as well as automatic instruments of very high
precision have been devised and are being used to gather
more and more information from nature. At present,
perhaps no other branch of science is as rich in information
as chemistry is and this is not the end. Chemistry will go
on flourishing more and more till the man exists on earth.
1.1.2 Branches of Chemistry
In order to facilitate the study of the subject and for
better understanding, chemistry has been divided into
several branches. The main branches of chemistry are as
follows.
(1) Inorganic chemistry: This branch of chemistry
studies all the elements and their compounds except
those of organic nature. Thus all metals, non-metals and
metalloids; their extraction, their properties; compounds
are
(ii) Organic chemistry: Carbon has an unique
property of forming exceptionally a very large number of
compounds. These compounds are aliphatic hydrocarbons
and their derivatives, benzene and its derivatives,
carbohydrates, proteins, fats, polymers, vitamins, etc. All
these compounds are studied in a separate branch known
as Organic chemistry.
(iii) Physical chemistry: This branch of chemistry offers
a logical explanation to the various chemical phenomena
with the help of various rules, hypothesis, theories, rules
and laws. All physico-chemical aspects of various energy
changes involved in chemical reactions are covered by
this branch. Nuclear processes and spectroscopy are also
studied in this branch of chemistry.
(iv) Analytical chemistry: This branch of chemistry
deals with the qualitative and quantitative analysis of
solid, liquid and gaseous mixtures. The branch, besides the
conventional techniques, makes use of very sophisticated
modern techniques for the purpose.
The branches mentioned above are the main branches
of chemistry. Besides these, several other branches also
came into existence during last few decades to meet the
specific requirements of various industries and research.
Among these, a few important branches are as follows.
(i) Bio-chemistry: This branch deals with the application
of chemistry to biological systems.
(ii) Chemical physics: This branch takes into account
the study of the chemistry of physical systems such as
plasma.
(iii) Industrial chemistry: This branch deals with the
industrial aspects of the manufacture of metals, non-metals
and their compounds.
(iv) Agricultural chemistry: It deals with the chemical
aspects of agriculture, e.g., development of seeds, fertilisers,
insecticides, pesticides, etc.
(v) Pharmaceutical chemistry: This branch is related to
drugs used for the prevention and cure of various diseases
1.1.3 The Importance and Scope of
Studying Chemistry
The scope of chemistry is practically unlimited.
It finds applications in all walks of life. Since its origin,
chemistry is serving the mankind. Perhaps, no other branch
of science has done so much to make a man’s life happier
as chemistry did. Whatever we see around us and whatever
we use in our day-to-day life is related to chemistry in
some way or the other. Chemistry has penetrated in our
life to such an extent that we cannot think of a smooth
running life without it. As mentioned earlier, food stuffs,
drugs, dyestuffs, polymers, metals, non-metals, fuels, glass,
ceramics and many more things are the boons of chemistry.
Almost all other branches of science lean heavily upon
chemistry for their basic requirements. Chemistry has an
excellent coordination with other branches of science and
goes along very well with them.
Both at the level of necessities and at the level of
Luxuries, chemistry has proved itself to be the best friend
Of mankind. It has improved the quality of our food stuffs
By adding new flavours to it. It has provided preservatives
Which can keep food fresh for years. The contribution of
Chemistry to agriculture is very significant. It developed
New varieties of seeds. The chemical fertilisers, insecticides,
Pesticides, etc., and improved quality of seeds have brought
A green revolution all over the world. The promises
Of chemistry in this field are so encouraging that it will
Completely eradicate starvation from the world in near
Future. Chemistry has provided synthetic fibres to make
Cheaper and better looking clothes. Chemistry has been
Successful in providing a wide range of medicines to fight
Against all kinds of diseases. Many life saving drugs such
As cisplatin, taxol, Azidothymidine (AZT), etc., are playing a
Vital role in combating against serious diseases like cancer,
AIDS, etc. Polymers are being used for a variety of purposes
In all walks of life. The electronics and electrical industries
Lean heavily upon chemistry for the basic materials used
Therein. It has provided various types of fuels for various
Purposes. Chemistry is also conscious about the increasing
Pollution on this planet. It is trying hard to check pollution
And to make environment healthier.
The history of elucidation of the particulate nature of
Matter dates back as early as 800 years before Buddha when
Kanada, an Indian saint and philosopher, postulated that
The matter is made up of simple unalterable particles called
Paramanus (atoms). According to Kanada, the universe
Is made of four eternal substances-earth water, fire and
Air and they consist of four different types of paramanus.
This atomic theory of Kanada was further strengthened
And developed by the Buddhist and Jain philosophers who
Believed that the matter consists of discrete particles called
Paramanus.
Today whatever we have from chemistry is by and
Large an outcome of the efforts of chemists during the last
Few decades and it is the beginning of an era of chemistry.
The researches are going on and the chemists, all over the
World, are toiling hard for squeezing more and more from
This branch of science for making man’s life happier and for
The advancement of the society. Although till now, chemistry
Could not fulfil the dream of alchemists to procure nectar.
A brief treatment of these classifications is given elements and compounds. Thus, matter can be classified
Into following three categories:
[A] Physical Classification of Matter
In this classification, matter is classified on the basis of
Its physical state. On the basis of physical state, the matter
Can be classified into following three states.
Solid state: Matter is said to be in solid state when it
Has a definite shape and possesses a definite volume. In this
State, the molecules are closely packed in a definite fashion
They have no freedom to move and can simply vibrate along
Their axes. Due to close packing of molecules, solids are
Hard and rigid. Common salt, ice, metals (except mercury),
Wood, etc., are some examples of solids.
Liquid state: The state in which the matter has
Definite volume but not a definite shape is called the liquid
State. In this state, the intermolecular distances are more
As compared to those in solids and molecules can freely
Move within the boundary of the liquid. Due to movement
Of molecules, liquids acquire the shape of the containing
Vessel. Water, milk, oils, mercury, etc., are some examples
Of liquids.
Gaseous state: When the matter posseses neither a
Definite volume nor a definite shape, it is said to be in the
Gaseous state. In this state, the molecules are perfectly
Free to move anywhere. Since in a gas, intermolecular
Distances are quite large, it can easily be compressed by
Applying pressure on it. Hence, a large quantity of gas can
Be packed into a desired small volume. This is why gases.
Possess neither a definite volume nor a definite shape. Air,
Oxygen, nitrogen, carbon dioxide, cooking gas, etc., are
Some common examples of gases.
A rough idea of these states and the intermolecular
Distances involved can be had from Fig 1.1.
Solid state
O
A
0
0
0
1
Liquid state
Gaseous state
Fig. 1.1 The three states of matter.
[B] Chemical Classification of Matter
In this classification, the matter is classified on
The basis of its chemical composition. On the basis of
Chemical composition, the matter can be classified into
Pure substances and mixtures. Pure substances include
Sare
Pure
Elements: Elements are the constituents of all pure
Contains only one type of substance. All pure substances
Substances. A pure substance is that substance which
Made of elements. An element may be defined as a
Substance which can neither be decomposed into, no
Can be synthesised from simpler substances by ordinary
Physical or chemical methods.
These 92 are found in the earth’s crust. Gold, silver, copper
Till now, more than 110 elements are known. Among
Iron, hydrogen, oxygen, nitrogen, etc., are some familiar
Elements of this type. Some of the elements are man made
And are prepared artificially by artificial radioactivity
Of this type. The distribution of elements in the earth’s
Kurtchovium, hahnium, neptunium, etc., are the elements
Crust is not uniform. Some elements, e.g., oxygen, silicon.
Aluminium, calcium, sodium, iron, etc., are quite abundant
But the elements like platinum, tungsten, thallium, gold,
Etc., are much less abundant. Only five elements namely
Oxygen, silicon, aluminium, iron and calcium constitute
About 90% of the earth’s crust. Remaining 10% of the
Earth’s crust is made of the remaining 87 elements. In
Atmospheric air also, the distribution of gaseous elements
Is not uniform. Nitrogen is the most abundant gas in air
And constitutes about 80% of it. Other gaseous elements,
e.g., oxygen, argon, helium, etc., are less abundant.
Elements can further be classified into following
Categories:
Metals: Metals are those solid (except
Mercury) elements which possess a
Characteristic lusture (shining), moderate
Hardness, malleability (can be pressed
Into sheets), ductility (can be drawn into
Wires) and are good conductors of heat and
Electricity. Iron, copper, silver, gold, zinc,
Aluminium, etc., are some commonly used
Metals.
Non-metals: These elements usually do not
Possess shine and are generally brittle (on
Beating break into pieces). These are either
Poor conductors or non-conductors of heat
And electricity. All gases like oxygen, nitrogen,
Etc., and solids like carbon, phosphorus, etc.,
Are non-metals.
© Metalloids: The elements which possess:
Properties characteristic to both metals and.
Non-metals are called metalloids. Germanium,
Arsenic, selenium, etc., are some examples of
Metalloids.
Compounds: Compounds are also regarded as pure-
Substances. These are made of two or more elements in
A definite ratio by mass. A compound may be defined as
The substance obtained by the chemical combination of
Two or more elements in a definite proportion by mass
And can be decomposed by chemical means into its
Constituent elements.
OBJECTIVES
The thorough study of this Unit would enable the reader to
. have a brief idea of history and importance of Chemistry:
• understand the measurement and the units used to express various physical and chemical quantities;
• learn Dalton’s atomic theory, Avogadro’s hypothesis, and the laws of chemical combination;
.
Have an idea of atoms, molecules, atomic masses, molecular masses and chemical equivalents;
. learn mole concept;
• carry out calculations involving mole concept, empirical and molecular formulae;
.
Balance the chemical equations and carry out calculations involving stoichiometry of chemical reactions.
Ymbolically, Chemistry may be defined as the
Sydne
Science of Rasas and colours. It colours our
Life with the discovery of different hidden colours
Of nature and all the Rasas necessary for making
Our life happier. The food we eat, the medicines we
Use for the prevention and cure of diseases, the natural
And synthetic fibres used for making fabrics, the various
Types of polymers used in all walks of day-to-day life, the
Cosmetics, the essences, the dye stuffs, all kinds of fuels
Used from kitchen stoves to rockets, all metals, non-metals
And many more things add colours to our life. All these
Things, whether of necessity or of luxury, are either given
By chemistry or related to it in some way or the other. The
Contributions and promises of chemistry for the welfare of
Human beings and for the advancement of society, both
In terms of necessities and luxuries, are many fold. Now-
a-days, the existence of an advanced civilization cannot
be thought of without chemistry. Therefore, the study of
chemistry is a must for the advancement of society and
for making mankind happier, healthier and wealthier.
The present form of chemistry that we study today
Has emerged mainly from the works of western chemists.
Perhaps, the first meaningful approach to chemistry was
Preparations, their properties, their accurate super-
Chemistry deals with the study of materials, their
Microscopic structures, their mutual interactions and
Their uses in all possible walks of life. It is concerned
With rocks, minerals, metals, non-metals, air, water,
Plants, animals, other materials of organic origin, earth
Atmosphere, interstellar atmosphere, etc. In brief, chemistry
Deals with everything which is essential for the betterment
Of human life and for adding colours to it.
1.1 A BRIEF HISTORY AND IMPORTANCE
1.1.1 A Brief History of Chemistry
In India, the study of chemistry is as old as the
Vedas are. Our ancient Rishis & Munis made significant
Contributions to chemistry. The ancient Vedic literature
Consists of valuable informations regarding the Rasa
Tantra, metals, metallurgy, combustion of matter and many
More things which may prove of immense importance to our
Modern practising chemists. In Vedic literature, the universe
Is supposed to be composed of Panchbhut, the five basic
Tatvas (elements)-Prithvi (the earth), Jala (the water),
Vayu (the air), Agni (the fire) and Akash (the sky). In Yajur
Veda, at one place the metals like iron, gold, copper, lead,
Tin have been mentioned along with stones, clay and sand.
OF CHEMISTRY
Made by Alchemists during the period 350-1500 A.D.
Alchemists were interested in discovering two things :
Nectar-a hypothetical syrup which could make man
Young and immortal and (ii) a philosopher’s stone-
A stone which could convert metals into gold. Alchemists
Were practically mad for acquiring these two things..
Unluckily they could not get either of these two things but
Their efforts made a valuable contribution to chemistry.
They devised various types of apparatus and discovered
Many processes such as extraction of gold by amalgamation
Process and preparation of caustic alkalis. We owe a lot to
These alchemists for their contributions to chemistry.
The period of 1500-1600 A.D. in chemistry is termed
As Iatro Chemistry Period. During this period a substantial
Study of gases was made. Robert Boyle is an important
Chemist of this period who extensively studied the
Behaviour of gases and gave an important law known asBoyle’s Law. During this period some chemical compounds of these elements-their preparation and properties
of medicinal value were also discovered.
studied in this branch.
Ernst Stahl (1660-1734) proposed a controversial
theory known as Phlogiston Theory. This theory survived for
about 100 years and the period of its survival in chemistry
is known as Phlogiston Period (1650-1774 A.D.). During
this period an extensive study of gases was carried out.
Several new gases were discovered and their behaviour
was studied.
The period beginning from the end of eighteenth
century is termed as Modern Period. In 1774, Joseph
Priestley discovered oxygen. Lavoisier, who is regarded
as father of modern chemistry, confirmed the discovery
made by Priestley and showed that oxygen is essential
for combustion. This explanation of combustion gave
an end to the Phlogiston Theory and to the Phlogiston
Period. In the beginning of nineteenth century, Laws of
chemical combination were formulated. In 1803, John
Dalton proposed his Atomic Theory. In 1869, Mendeleev,
a Russian scientist, made a significant contribution to
chemistry by introducing periodic law and by arranging the
elements in the form of a Periodic table. In 1833, Faraday
studied the passage of current through solutions and in
1881, Arrhenius proposed theory of ionisation.
The direction of research in chemistry took a new
turn when J.J. Thomson in 1896 succeeded in passing
electric discharge through gases at very low pressure.
and discovered electron. Almost at the same time
(1886) Goldstein discovered proton. In 1932, Sir James
Chadwick discovered neutron. With the advent of these
fundamental particles, the atom was no longer indivisible
as proposed by John Dalton. These researches gave new
dimensions to chemistry. With the advent of atomic number
by Henry Mosley in 1913, new concepts were conceived
and Mendeleev’s Periodic table was revised. The pioneer
work of Rutherford, Curies, etc., opened new vistas in the
field of nuclear chemistry.
The twentieth century may be said to be the
golden period of chemistry. During the last five decades
our knowledge of chemistry has increased manyfold.
Non-stop research work in chemistry is going on in almost
all the parts of the world. Highly sophisticated, both
manual as well as automatic instruments of very high
precision have been devised and are being used to gather
more and more information from nature. At present,
perhaps no other branch of science is as rich in information
as chemistry is and this is not the end. Chemistry will go
on flourishing more and more till the man exists on earth.
1.1.2 Branches of Chemistry
In order to facilitate the study of the subject and for
better understanding, chemistry has been divided into
several branches. The main branches of chemistry are as
follows.
(1) Inorganic chemistry: This branch of chemistry
studies all the elements and their compounds except
those of organic nature. Thus all metals, non-metals and
metalloids; their extraction, their properties; compounds
are
(ii) Organic chemistry: Carbon has an unique
property of forming exceptionally a very large number of
compounds. These compounds are aliphatic hydrocarbons
and their derivatives, benzene and its derivatives,
carbohydrates, proteins, fats, polymers, vitamins, etc. All
these compounds are studied in a separate branch known
as Organic chemistry.
(iii) Physical chemistry: This branch of chemistry offers
a logical explanation to the various chemical phenomena
with the help of various rules, hypothesis, theories, rules
and laws. All physico-chemical aspects of various energy
changes involved in chemical reactions are covered by
this branch. Nuclear processes and spectroscopy are also
studied in this branch of chemistry.
(iv) Analytical chemistry: This branch of chemistry
deals with the qualitative and quantitative analysis of
solid, liquid and gaseous mixtures. The branch, besides the
conventional techniques, makes use of very sophisticated
modern techniques for the purpose.
The branches mentioned above are the main branches
of chemistry. Besides these, several other branches also
came into existence during last few decades to meet the
specific requirements of various industries and research.
Among these, a few important branches are as follows.
(i) Bio-chemistry: This branch deals with the application
of chemistry to biological systems.
(ii) Chemical physics: This branch takes into account
the study of the chemistry of physical systems such as
plasma.
(iii) Industrial chemistry: This branch deals with the
industrial aspects of the manufacture of metals, non-metals
and their compounds.
(iv) Agricultural chemistry: It deals with the chemical
aspects of agriculture, e.g., development of seeds, fertilisers,
insecticides, pesticides, etc.
(v) Pharmaceutical chemistry: This branch is related to
drugs used for the prevention and cure of various diseases
1.1.3 The Importance and Scope of
Studying Chemistry
The scope of chemistry is practically unlimited.
It finds applications in all walks of life. Since its origin,
chemistry is serving the mankind. Perhaps, no other branch
of science has done so much to make a man’s life happier
as chemistry did. Whatever we see around us and whatever
we use in our day-to-day life is related to chemistry in
some way or the other. Chemistry has penetrated in our
life to such an extent that we cannot think of a smooth
running life without it. As mentioned earlier, food stuffs,
drugs, dyestuffs, polymers, metals, non-metals, fuels, glass,
ceramics and many more things are the boons of chemistry.
Almost all other branches of science lean heavily upon
chemistry for their basic requirements. Chemistry has an
excellent coordination with other branches of science and
goes along very well with them.
Both at the level of necessities and at the level of
Luxuries, chemistry has proved itself to be the best friend
Of mankind. It has improved the quality of our food stuffs
By adding new flavours to it. It has provided preservatives
Which can keep food fresh for years. The contribution of
Chemistry to agriculture is very significant. It developed
New varieties of seeds. The chemical fertilisers, insecticides,
Pesticides, etc., and improved quality of seeds have brought
A green revolution all over the world. The promises
Of chemistry in this field are so encouraging that it will
Completely eradicate starvation from the world in near
Future. Chemistry has provided synthetic fibres to make
Cheaper and better looking clothes. Chemistry has been
Successful in providing a wide range of medicines to fight
Against all kinds of diseases. Many life saving drugs such
As cisplatin, taxol, Azidothymidine (AZT), etc., are playing a
Vital role in combating against serious diseases like cancer,
AIDS, etc. Polymers are being used for a variety of purposes
In all walks of life. The electronics and electrical industries
Lean heavily upon chemistry for the basic materials used
Therein. It has provided various types of fuels for various
Purposes. Chemistry is also conscious about the increasing
Pollution on this planet. It is trying hard to check pollution
And to make environment healthier.
The history of elucidation of the particulate nature of
Matter dates back as early as 800 years before Buddha when
Kanada, an Indian saint and philosopher, postulated that
The matter is made up of simple unalterable particles called
Paramanus (atoms). According to Kanada, the universe
Is made of four eternal substances-earth water, fire and
Air and they consist of four different types of paramanus.
This atomic theory of Kanada was further strengthened
And developed by the Buddhist and Jain philosophers who
Believed that the matter consists of discrete particles called
Paramanus.
Today whatever we have from chemistry is by and
Large an outcome of the efforts of chemists during the last
Few decades and it is the beginning of an era of chemistry.
The researches are going on and the chemists, all over the
World, are toiling hard for squeezing more and more from
This branch of science for making man’s life happier and for
The advancement of the society. Although till now, chemistry
Could not fulfil the dream of alchemists to procure nectar.
A brief treatment of these classifications is given elements and compounds. Thus, matter can be classified
Into following three categories:
[A] Physical Classification of Matter
In this classification, matter is classified on the basis of
Its physical state. On the basis of physical state, the matter
Can be classified into following three states.
Solid state: Matter is said to be in solid state when it
Has a definite shape and possesses a definite volume. In this
State, the molecules are closely packed in a definite fashion
They have no freedom to move and can simply vibrate along
Their axes. Due to close packing of molecules, solids are
Hard and rigid. Common salt, ice, metals (except mercury),
Wood, etc., are some examples of solids.
Liquid state: The state in which the matter has
Definite volume but not a definite shape is called the liquid
State. In this state, the intermolecular distances are more
As compared to those in solids and molecules can freely
Move within the boundary of the liquid. Due to movement
Of molecules, liquids acquire the shape of the containing
Vessel. Water, milk, oils, mercury, etc., are some examples
Of liquids.
Gaseous state: When the matter posseses neither a
Definite volume nor a definite shape, it is said to be in the
Gaseous state. In this state, the molecules are perfectly
Free to move anywhere. Since in a gas, intermolecular
Distances are quite large, it can easily be compressed by
Applying pressure on it. Hence, a large quantity of gas can
Be packed into a desired small volume. This is why gases.
Possess neither a definite volume nor a definite shape. Air,
Oxygen, nitrogen, carbon dioxide, cooking gas, etc., are
Some common examples of gases.
A rough idea of these states and the intermolecular
Distances involved can be had from Fig 1.1.
Solid state
O
A
0
0
0
1
Liquid state
Gaseous state
Fig. 1.1 The three states of matter.
[B] Chemical Classification of Matter
In this classification, the matter is classified on
The basis of its chemical composition. On the basis of
Chemical composition, the matter can be classified into
Pure substances and mixtures. Pure substances include
Sare
Pure
Elements: Elements are the constituents of all pure
Contains only one type of substance. All pure substances
Substances. A pure substance is that substance which
Made of elements. An element may be defined as a
Substance which can neither be decomposed into, no
Can be synthesised from simpler substances by ordinary
Physical or chemical methods.
These 92 are found in the earth’s crust. Gold, silver, copper
Till now, more than 110 elements are known. Among
Iron, hydrogen, oxygen, nitrogen, etc., are some familiar
Elements of this type. Some of the elements are man made
And are prepared artificially by artificial radioactivity
Of this type. The distribution of elements in the earth’s
Kurtchovium, hahnium, neptunium, etc., are the elements
Crust is not uniform. Some elements, e.g., oxygen, silicon.
Aluminium, calcium, sodium, iron, etc., are quite abundant
But the elements like platinum, tungsten, thallium, gold,
Etc., are much less abundant. Only five elements namely
Oxygen, silicon, aluminium, iron and calcium constitute
About 90% of the earth’s crust. Remaining 10% of the
Earth’s crust is made of the remaining 87 elements. In
Atmospheric air also, the distribution of gaseous elements
Is not uniform. Nitrogen is the most abundant gas in air
And constitutes about 80% of it. Other gaseous elements,
e.g., oxygen, argon, helium, etc., are less abundant.
Elements can further be classified into following
Categories:
Metals: Metals are those solid (except
Mercury) elements which possess a
Characteristic lusture (shining), moderate
Hardness, malleability (can be pressed
Into sheets), ductility (can be drawn into
Wires) and are good conductors of heat and
Electricity. Iron, copper, silver, gold, zinc,
Aluminium, etc., are some commonly used
Metals.
Non-metals: These elements usually do not
Possess shine and are generally brittle (on
Beating break into pieces). These are either
Poor conductors or non-conductors of heat
And electricity. All gases like oxygen, nitrogen,
Etc., and solids like carbon, phosphorus, etc.,
Are non-metals.
© Metalloids: The elements which possess:
Properties characteristic to both metals and.
Non-metals are called metalloids. Germanium,
Arsenic, selenium, etc., are some examples of
Metalloids.
Compounds: Compounds are also regarded as pure-
Substances. These are made of two or more elements in
A definite ratio by mass. A compound may be defined as
The substance obtained by the chemical combination of
Two or more elements in a definite proportion by mass
And can be decomposed by chemical means into its
Constituent elements.