BASIC CONCEPTS OF CHEMISTRY {CHAPTER 1} {specially for polytechnic 1 year students }1sem
BASIC CONCEPTS OF CHEMISTRY
Define chemistry -----
ANS---chemistry is a branch of science which deals with the composition,
structure and properties of matter and the changes which it undergoes under
different conditions.
chemistry can be sub divided in two important branches
1 Inorganic chemistry
2 organic chemistry
inorganic chemistry --The branch of chemistry which deals with the study of
elements and compounds other than those of carbon is called inorganic chemistry.
organic chemistry- the branch of chemistry which deals with the study of
carbon compounds is called organic chemistry.
si unit -- in different times, different types of measurements have been
popular in different
parts of world in other way with is
use to different type of measurements
pressure --- F/A
f- force
A - Area
si unit of volume ------length *breath*Height {*-- multiply}
length - Metre
mass -kg
time -second
electric --current ampere
temperature - kelvin
amount of substance - mole
luminous - candela
si unit of density - m/v
si unit of specific gravity - density if material/density of water in 4*C
si unit of surface tension - force /length
si unit of viscosity - force
/Area multiply by velocity gradient
MATTER---------------
MATTER is defined as anything that occupies space and has mass and cn be
felt by any of our five senses
for example wood , air , table etc
matter can be classified in three classes
element
compounds mixture
element=an element may be a pure substance which cannot be split into to or
more sustance by any chemical or physical methods
ex carbon ,gold ,oxygen etc
compounds -it is defined as a substance made of two or more elements
combined in a fixed ratio by weight and
which can be decompose into its constituents by suitable chemical method
mixture - a mixture may be defined as the combination of two or more
elements or compounds in any ratio so
that the constituents do not lose there idendity.
MAIN QUESTION IN 3OR 5 Number
difference between compound and mixture
compounds
mixture
they are always homogenious -they can be
homogenious and heterogenious
they have sharp m.pt and b.pts - their m.pt and
and b.pts not sharp
they show a range
they are formed as a result of chemical change - they are formed as a resut of physical
change
their formation leads to energy change -No energy changes occours during their formation
Atoms ----------
it may be defined as the smallest particles of an elements which may or may
not be capable of independents existence
Molecules ----------
the ultimate particle of a compound is called a molecules . molecules and
made up of same or different elements and these are always capable of
independents existance
these are mainly two types
homo atomic molecules - the molecules which are made up of atoms of same
elements are known as homo atomic molecules.
Hetero atomic molecules = the molecules which are made up of atoms and
different elements
are known as hetero atomic molecules .
SYmbol - the short nation used for the full name of elements is called
symbol.
for ex oxygen O
chemical equation -------------
a chemical equation may be defined as a brief representation of chemical
changes in terms of
symbols and formula of substance involve in it
characteristics of chemical equation ----------------
it should obey law of conservation of mass
it should obey law of conservation of
energy
it should be balanced
LIMITATIONS OF CHEMICAL EQUATION -------------
IT Does't give information regarding physical physical state of matter
reversibility of a reaction cannot be known in simple reaction like
mechanism of a chemical reaction is not known by simple reaction like
simple chemical reaction doesn't show precautions and preventive measures
during explosive chemical reaction
BALANCING OF CHEMICAL EQUATION ------------
a complete and accurate chemical reaction in which number of atoms of each
elements should be equal in both sides
THERMO CHEMICAL EQUATION---------
A chemical equation which includes heat changes occouring during a chemical
reaction is known
as thermo chemical equations
these reaction mainly two types
1 endothermic reaction
2 exothermic reaction
endothermic reaction - these reaction are take place with the absorption of
heat are known as endothermic reaction
exothermic reaction - the reaction which take place with the evoluation of
heat are known as exothermic reaction
Types of formula
1 empirical formula
2 molecular formula
two methods of balancing equation
1 hit and trial methods
2 partial equation methods
disadvantages of hit and trial methods
1 it takes a long time
2 it does not give any information regarding the mechanism of the reaction
3 this method is rather difficult
for balancing such equation which contain the same elements being repeated in a
number of compound .
a.m.u - 1/12 th of the mass of an
atoms carbon
NOBEL GASES ----------
in nobel gases all the energy levels which are occupied are completely
filled and this stable arrangement of electrons cannot be easily altered either
by addition or removal of electrons . as a result these elements are highly
stable and hence are chemically inert . that is why these element are also
called inert gases
VALENCE ELECTRONS-----
THE electrons present in the outermost shell of an atoms are called valence
electrons
GRAM atomic mass -----
the atomic mass of an elements
expressed in gram is called gram atomic gram
skeleton equations -----
A chemical equation which indicates only the various reactions and products
of a chemical changes is known as a skeleton equation
CHEMICAL FORMULA
showing how to write chamical formula of calcium chloride
chemical formula of zinc phosphate
CHEMICAL FORMULA
showing how to write chamical formula of calcium chloride
chemical formula of zinc phosphate
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