UNIT 1
SOME BASIC CONCEPTS OF CHEMISTRY
Chemistry is the science of molecules and their
transformations. It is the science not so much of the one
hundred elements but of the infinite variety of molecules that
may be built from them.
Roald Hoffmann
Science can be viewed as a continuing human effort to
systematise knowledge for describing and understanding
nature. You have learnt in your previous classes that we come
across diverse substances present in nature and changes in
them in daily life. Curd formation from milk, formation of
vinegar from sugarcane juice on keeping for prolonged time
and rusting of iron are some of the examples of changes which
we come across many times. For the sake of convenience,
science is sub-divided into various disciplines: chemistry,
physics, biology, geology, etc. The branch of science that
studies the preparation, properties, structure and reactions
of material substances is called chemistry.
DEVELOPMENT OF CHEMISTRY
Chemistry, as we understand it today, is not a very old
discipline. Chemistry was not studied for its own sake, rather
it came up as a result of search for two interesting things:
i. Philosopher’s stone (Paras) which would convert
all baser metals e.g., iron and copper into gold.
ii.‘Elexir of life’ which would grant immortality.
People in ancient India, already had the knowledge of many
scientific phenomenon much before the advent of modern
science. They applied that knowledge in various walks of
life. Chemistry developed mainly in the form of Alchemy
and Iatrochemistry during 1300-1600 CE. Modern
chemistry took shape in the 18
th
century Europe, after a
few centuries of alchemical traditions which were
introduced in Europe by the Arabs.
After studying this unit, you will be
able to
appreciate the contribution of
India in the development of
chemistry understand the role of
chemistry in different spheres of
life;
explain the characteristics of
three states of matter;
classify different substances into
elements, compounds and
mixtures;
use scientific notations and
determine significant figures;
differentiate between precision and
accuracy;
define SI base units and convert
physical quantities from one
system of units to another;
explain various laws of chemical
combination;
appreciate significance of atomic
mass, average atomic mass,
molecular mass and formula
mass;
describe the terms – mole and
molar mass;
calculate the mass per cent of
component elements constituting
a compound;
determine empirical formula and
molecular formula for a compound
from the given experimental data;
and
perform the stoichiometric
calculations.
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2 CHEMISTRY
Other cultures – especially the Chinese and
the Indian – had their own alchemical traditions.
These included much knowledge of chemical
processes and techniques.
In ancient India, chemistry was called
Rasayan Shastra, Rastantra, Ras Kriya or
Rasvidya. It included metallurgy, medicine,
manufacture of cosmetics, glass, dyes, etc.
Systematic excavations at Mohenjodaro in
Sindh and Harappa in Punjab prove that the
story of development of chemistry in India is
very old. Archaeological findings show that
baked bricks were used in construction work.
It shows the mass production of pottery, which
can be regarded as the earliest chemical process,
in which materials were mixed, moulded and
subjected to heat by using fire to achieve
desirable qualities. Remains of glazed pottery
have been found in Mohenjodaro. Gypsum
cement has been used in the construction work.
It contains lime, sand and traces of CaCO
3.
Harappans made faience, a sort of glass which
was used in ornaments. They melted and forged
a variety of objects from metals, such as lead,
silver, gold and copper. They improved the
hardness of copper for making artefacts by
using tin and arsenic. A number of glass objects
were found in Maski in South India (1000–900
BCE), and Hastinapur and Taxila in North
India (1000–200 BCE). Glass and glazes were
coloured by addition of colouring agents like
metal oxides.
Copper metallurgy in India dates back to
the beginning of chalcolithic cultures in the
subcontinent. There are much archeological
evidences to support the view that technologies
for extraction of copper and iron were developed
indigenously.
According to Rigveda, tanning of leather
and dying of cotton were practised during
1000–400 BCE. The golden gloss of the black
polished ware of northen India could not be
replicated and is still a chemical mystery. These
wares indicate the mastery with which kiln
temperatures could be controlled. Kautilya’s
Arthashastra describes the production of salt
from sea.
A vast number of statements and material
described in the ancient Vedic literature can
be shown to agree with modern scientific
findings. Copper utensils, iron, gold, silver
ornaments and terracotta discs and painted
grey pottery have been found in many
archaeological sites in north India. Sushruta
Samhita explains the importance of Alkalies.
The Charaka Samhita mentions ancient
indians who knew how to prepare sulphuric
acid, nitric acid and oxides of copper, tin and
zinc; the sulphates of copper, zinc and iron and
the carbonates of lead and iron.
Rasopanishada describes the preparation
of gunpowder mixture. Tamil texts also
describe the preparation of fireworks using
sulphur, charcoal, saltpetre (i.e., potassium
nitrate), mercury, camphor, etc.
Nagarjuna was a great Indian scientist. He
was a reputed chemist, an alchemist and a
metallurgist. His work Rasratnakar deals with
the formulation of mercury compounds. He has
also discussed methods for the extraction of
metals, like gold, silver, tin and copper. A book,
Rsarnavam, appeared around 800 CE. It
discusses the uses of various furnaces, ovens
and crucibles for different purposes. It
describes methods by which metals could be
identified by flame colour.
Chakrapani discovered mercury sulphide.
The credit for inventing soap also goes to him.
He used mustard oil and some alkalies as
ingredients for making soap. Indians began
making soaps in the 18
th
century CE. Oil of
Eranda and seeds of Mahua plant and calcium
carbonate were used for making soap.
The paintings found on the walls of Ajanta
and Ellora, which look fresh even after ages,
testify to a high level of science achieved in
ancient India. Varähmihir’s Brihat Samhita is
a sort of encyclopaedia, which was composed
in the sixth century CE. It informs about the
preparation of glutinous material to be applied
on walls and roofs of houses and temples. It
was prepared entirely from extracts of various
plants, fruits, seeds and barks, which were
concentrated by boiling, and then, treated with
various resins. It will be interesting to test such
materials scientifically and assess them for use.
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3SOME BASIC CONCEPTS OF CHEMISTRY
A number of classical texts, like
Atharvaveda (1000 BCE) mention some dye
stuff, the material used were turmeric, madder,
sunflower, orpiment, cochineal and lac. Some
other substances having tinting property were
kamplcica, pattanga and jatuka.
Varähmihir’s Brihat Samhita gives
references to perfumes and cosmetics. Recipes
for hair dying were made from plants, like
indigo and minerals like iron power, black iron
or steel and acidic extracts of sour rice gruel.
Gandhayukli describes recipes for making
scents, mouth perfumes, bath powders,
incense and talcum power.
Paper was known to India in the
17
th
century as account of Chinese traveller
I-tsing describes. Excavations at Taxila indicate
that ink was used in India from the fourth
century. Colours of ink were made from chalk,
red lead and minimum.
It seems that the process of fermentation
was well-known to Indians. Vedas and
Kautilya’s Arthashastra mention about many
types of liquors. Charaka Samhita also
mentions ingredients, such as barks of plants,
stem, flowers, leaves, woods, cereals, fruits and
sugarcane for making Asavas.
The concept that matter is ultimately made
of indivisible building blocks, appeared in
India a few centuries BCE as a part of
philosophical speculations. Acharya Kanda,
born in 600 BCE, originally known by the
name Kashyap, was the first proponent of the
‘atomic theory’. He formulated the theory of
very small indivisible particles, which he
named ‘Paramãnu’ (comparable to atoms). He
authored the text Vaiseshika Sutras.
According to him, all substances are
aggregated form of smaller units called atoms
(Paramãnu), which are eternal, indestructible,
spherical, suprasensible and in motion in the
original state. He explained that this individual
entity cannot be sensed through any human
organ. Kanda added that there are varieties of
atoms that are as different as the different
classes of substances. He said these
(Paramãnu) could form pairs or triplets, among
other combinations and unseen forces cause
interaction between them. He conceptualised
this theory around 2500 years before John
Dalton (1766-1844).
Charaka Samhita is the oldest Ayurvedic
epic of India. It describes the treatment of
diseases. The concept of reduction of particle
size of metals is clearly discussed in Charaka
Samhita. Extreme reduction of particle size is
termed as nanotechnology.
Charaka Samhita
describes the use of bhasma of metals in the
treatment of ailments. Now-a-days, it has been
proved that bhasmas have nanoparticles of
metals.
After the decline of alchemy, Iatrochemistry
reached a steady state, but it too declined due
to the introduction and practise of western
medicinal system in the 20
th
century. During
this period of stagnation, pharmaceutical
industry based on Ayurveda continued to
exist, but it too declined gradually. It took
about 100-150 years for Indians to learn and
adopt new techniques. During this time, foreign
products poured in. As a result, indigenous
traditional techniques gradually declined.
Modern science appeared in Indian scene in
the later part of the nineteenth century. By the
mid-nineteenth century, European scientists
started coming to India and modern chemistry
started growing.
From the above discussion, you have learnt
that chemistry deals with the composition,
structure, properties and interection of matter
and is of much use to human beings in daily
life. These aspects can be best described and
understood in terms of basic constituents of
matter that are atoms and molecules. That
is why, chemistry is also called the science of
atoms and molecules. Can we see, weigh and
perceive these entities (atoms and molecules)?
Is it possible to count the number of atoms
and molecules in a given mass of matter and
have a quantitative relationship between the
mass and the number of these particles? We
will get the answer of some of these questions
in this Unit. We will further describe how
physical properties of matter can be
quantitatively described using numerical
values with suitable units.
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1.1 IMPORTANCE OF CHEMISTRY
Chemistry plays a central role in science and
is often intertwined with other branches of
science.
Principles of chemistry are applicable in
diverse areas, such as weather patterns,
functioning of brain and operation of a
computer, production in chemical industries,
manufacturing fertilisers, alkalis, acids, salts,
dyes, polymers, drugs, soaps, detergents,
metals, alloys, etc., including new material.
Chemistry contributes in a big way to the
national economy. It also plays an important
role in meeting human needs for food,
healthcare products and other material
aimed at improving the quality of life. This
is exemplified by the large-scale production
of a variety of fertilisers, improved variety of
pesticides and insecticides. Chemistry
provides methods for the isolation of life-
saving drugs from natural sources and
makes possible synthesis of such drugs.
Some of these drugs are cisplatin and taxol,
which are effective in cancer therapy. The
drug AZT (Azidothymidine) is used for
helping AIDS patients.
Chemistry contributes to a large extent
in the development and growth of a nation.
With a better understanding of chemical
principles it has now become possible to
design and synthesise new material having
specific magnetic, electric and optical
properties. This has lead to the production
of superconducting ceramics, conducting
polymers, optical fibres, etc. Chemistry has
helped in establishing industries which
manufacture utility goods, like acids,
alkalies, dyes, polymesr metals, etc. These
industries contribute in a big way to the
economy of a nation and generate
employment.
In recent years, chemistry has helped
in dealing with some of the pressing aspects
of environmental degradation with a fair
degree of success. Safer alternatives to
environmentally hazardous refrigerants, like
CFCs (chlorofluorocarbons), responsible for
ozone depletion in the stratosphere, have
been successfully synthesised. However,
many big environmental problems continue
to be matters of grave concern to the
chemists. One such problem is the
management of the Green House gases, like
methane, carbon dioxide, etc. Understanding
of biochemical processes, use of enzymes for
large-scale production of chemicals and
synthesis of new exotic material are some of
the intellectual challenges for the future
generation of chemists. A developing country,
like India, needs talented and creative
chemists for accepting such challenges. To
be a good chemist and to accept such
challanges, one needs to understand the
basic concepts of chemistry, which begin with
the concept of matter. Let us start with the
nature of matter.
1.2 NATURE OF MATTER
You are already familiar with the term matter
from your earlier classes. Anything which has
mass and occupies space is called matter
.
Everything around us, for example, book, pen,
pencil, water, air, all living beings, etc., are
composed of matter. You know that they have
mass and they occupy space. Let us recall the
characteristics of the states of matter, which
you learnt in your previous classes.
1.2.1 States of Matter
You are aware that matter can exist in three
physical states viz. solid, liquid and gas. The
constituent particles of matter in these three
states can be represented as shown in Fig. 1.1.
Particles are held very close to each other
in solids in an orderly fashion and there is not
much freedom of movement. In liquids, the
particles are close to each other but they can
move around. However, in gases, the particles
are far apart as compared to those present in
solid or liquid states and their movement is
easy and fast. Because of such arrangement
of particles, different states of matter exhibit
the following characteristics:
(i) Solids have definite volume and definite
shape.
(ii) Liquids have definite volume but do not
have definite shape. They take the shape
of the container in which they are placed.
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