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SOME BASIC CONCEPTS OF CHEMISTRY

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UNIT 1

SOME BASIC CONCEPTS OF CHEMISTRY

After studying this unit, you will be
able to
• understand and appreciate 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;
• define SI base units and list some
commonly used prefixes;
• use scientific notations and
perform simple mathematical
operations on numbers;
• differentiate between precision and
accuracy;
• determine significant figures;
• 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
different elements constituting a
compound;
• determine empirical formula and
molecular formula for a compound
from the given experimental data;
• perform the stoichiometric
calculations.

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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

Chemistry deals with the composition, structure and
properties of matter. These aspects can be best described
and understood in terms of basic constituents of matter:
atoms and molecules. That is why chemistry is called
the science of atoms and molecules. Can we see, weigh
and perceive these entities? 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
number of these particles (atoms and molecules)? We will
like to answer some of these questions in this Unit. We
would further describe how physical properties of matter
can be quantitatively described using numerical values
with suitable units.
1.1 IMPORTANCE OF CHEMISTRY
Science can be viewed as a continuing human effort to
systematize knowledge for describing and understanding
nature. For the sake of convenience science is sub-divided
into various disciplines: chemistry, physics, biology,
geology etc. Chemistry is the branch of science that studies the composition, properties and interaction of matter.
Chemists are interested in knowing how chemical
transformations occur. Chemistry plays a central role in
science and is often intertwined with other branches of
science like physics, biology, geology etc. Chemistry also
plays an important role in daily life.
Chemical principles are important in diverse areas, such
as: weather patterns, functioning of brain and operation

C:\ChemistryXI\Unit-1\Unit-1(3)-Lay-3.pmd 6.1.2006 (Final), 13.1.6, 17.1.6, 24.1.6, 17.2.6

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CHEMISTRY

of a computer. Chemical industries
manufacturing fertilizers, alkalis, acids, salts,
dyes, polymers, drugs, soaps, detergents,
metals, alloys and other inorganic and organic
chemicals, including new materials, contribute
in a big way to the national economy.
Chemistry plays an important role in meeting
human needs for food, health care products
and other materials aimed at improving the
quality of life. This is exemplified by the large
scale production of a variety of fertilizers,
improved varieties of pesticides and
insecticides. Similarly many life saving drugs
such as cisplatin and taxol, are effective in
cancer therapy and AZT (Azidothymidine)
used for helping AIDS victims, have been
isolated from plant and animal sources or
prepared by synthetic methods.
With a better understanding of chemical
principles it has now become possible to
design and synthesize new materials having
specific magnetic, electric and optical
properties. This has lead to the production of
superconducting ceramics, conducting
polymers, optical fibres and large scale
miniaturization of solid state...
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