Degree of hotness or coldness of a body is called "TEMPERATURE".
"Temperature is a measure of the intensity of heat".
Temperature is defined as :
"the average kinetic energy of the molecules of a body is called temperature"
|SCALES OF TEMPERATURE:|
There are three scales of temperature.
1. Celsius or centigrade scale C.
2. Fahrenheit scale F.
3. Kelvin or Absolute scale K.
|Centigrade & kelvin|
|Tk = Tc + 273|
|Centigrade & Fahrenheit|
|C/5 = (F-32) /9|
Volume is defined as
" The space occupied by An object is called its volume."
|Volume is denoted by "V|
a) Cubic meter
|The quantity of matter contained in a body is called its "Mass".|
|Mass is denoted by "m".|
per unit volume of a substance is called its "Density".
Mass of one dm3 or one m3 or one cm3 of a substance is called its density.
a) Kg / m3
b) gm / cm3
c) gm /litre
d) gm / dm3
mass or formula mass or molecular mass of a substance expressed in
grams is called MOLE".
Mass of substance contains 6.02 x 1023 atoms or molecules or ions is called "mole"
1. Atomic mass of carbon = 12 a.m.u.
therefore 12 gram of carbon = one mole of carbon.
2. Formula mass of Nacl = 58.5 a.m.u.
therefore 58.5 gm of Nacl = 1 mole of Nacl.
3. Molecular mass of CO = 28 a.m.u.
therefore 28 gm of CO = I mole of CO
|Number of moles = mass of substance(in grams) / molecular or atomic or formula mass of substance|
|6. AVOGADRO'S NUMBER|
One mole of any substance contains 6.02 x 1023 atoms, molecules
or ions. This particular number is called "AVOGADRO'S
It is denoted by NA.
1 mole carbon = 6.02 x 1023 carbon atoms.
1 mole Na+ = 6.02 x 1023 Na+ ions.
1 mole H2O = 6.02 x 1023 H2O molecules.
|7. LAW OF DEFINITE PROPOTION|
|According to the law of definite propotion|
sample of pure substance always contains same elements
in fixed propotion regardless of its method of preperation"
We can obtain or prepare water by a number of methods but water obtained
from any source always contain 11.11% hydrogen and
Similarly CO2 can be prepared by different methods but each sample of CO2 contains C=27.27% and O=72.72%.
|8. SPECIFIC GRAVITY|
Specific gravity of a substance is defined as the ratio of the
substance to the mass of an equal volume of water at a particular temperature.
|Specific gravity = mass of substance / mass of an equal volume of water|
|It has no unit.|
|9. GRAM ATOMIC MASS|
|"Atomic mass of an element expressed in gram is called gram atomic mass"|
Gram atomic mass of C=12gm.
Gram atomic mass of H=1 gm.
Gram atomic mass of O=16 gm.
|10. GRAM MOLECULAR MASS|
|"Molecular mass of a molecule expressed in gms is called gram molecular mass."|
Gram molecular mass of hydrogen gas=2 gm.
Gram molecular mass of oxygen gas =32gm.
Gram molecular mass of HCl = 36.5 gm
|"Element is defined as a pure substance in which all the atoms have same chemical properties and have same atomic number"|
Carbon, sodium, hydrogen, chlorine, copper, gold, iron e.t.c.
|TYPES OF ELEMENTS|
Elements can be divided into two classes.
They have shine on their surface.
They are good conductors of electricity and heat.
They reflect light.
Metals are ductile.
Metals are malleable.
|Cu, Fe, Au, Na, Ca e.t.c.|
They have dull surface.
They are bad conductors of electricity and heat.
Non-metals are non ductile.
They cannot be drawn into sheets.
They are brittle.
H2, C, Cl2, O2, N2 e.t.c.
|Valency is defined as|
|"the combining capacity or combining power of an element with other element"|
In other words Valency may be defined as:
the number of H-atoms which combine with or displace one atom of an element or a radical.
|The smallest unit of an element or compound, which can exist independently, is called "molecule".|
|14. EMPIRICAL FORMULA|
Formula is that formula which expresses the relative number
of each kind of atoms present in the molecule of a compound"
"The formula of a compound which expresses the ratio in which atoms of
different elements are combined in a molecule"
formula only indicates atomic ratios but it does not indicate actual
number of atoms of different kinds present in the molecule of a compound.
Two or more compound may have same empirical formula.
Empirical formula is determined by experiment.
Empirical Formula of Benzene = CH.
Empirical Formula of Glucose = CH2O
molecular formula of a compound is defined as:
"The formula of a compound which not only expresses the relative nummer of atoms of each kind but also expresses the actual number of atoms of each element present in one molecule".
formula and empirical formula of a compound are related as:
MOLECULAR FORMULA = (EMPIRICAL FORMULA)n
|Where "n" is an integer and is given by:|
|n = molecular mass of compound / Empirical formula mass of compound|
Molecular formula of propane = C3H8.
Molecular formula of sugar = C12H22O11.
|A symbol is an abbreviation for the chemical name of an element|
|A symbol represents only one atom of an element.|
Carbon = C, Hydrogen= H, Chlorine = Cl, Gold = Au, Silver = Ag, Sodium = Na, bismuth = Bi etc.
representation of molecule of a substance or compound in
the form of symbols is called "formula".
With the help of formula we can find.
(1) Name of elements present in the molecule.
(2) Number of atoms of each element.
(3) Composition of compound.
NH3, CO2, CaCO3, H2O, H2SO4 etc.
are pure substances, which consist of two or more elements
combined chemically in a fixed ratio."
|Compounds always have a definite composition.|
H2SO4, CaCl2, H2O, CO2 etc.
mixture is a substance, which consists of two or more pure substances
not chemically combined with each other in a definite composition ."
|Mixtures do not have definite composition.|
Air, soil, brass ( cu + zinc) etc.
|DIFFERENCE BETWEEN COMPOUND AND MIXTURE|
|TYPES OF MIXTURE:|
There are two types of mixture:
(1) Homogenous mixture.
(2) Heterogeneous mixture.
|A homogeneous mixture is defined as "the mixture, which has uniform composition throughout its mass".|
Air, sugar solution, salt solution, alloys, soft drinks (Pepsi, coca-cola etc.)
mixture that do not have uniform composition throughout its
mass is known as heterogeneous mixture".
Soil, rocks etc.
|Any substance which possesses mass and occupies space is called "MATTER".|
is the stuff of which our whole universe is made.
All matter on the earth is composed of either pure substance or a mixture of substances.
|Many elements exhibit more than one valency which is known as variable valency.|
Iron = Ferrous(+2), ferric (+3)
Copper = Cuprous (+1),cupric (+2)
Mercury = Mercurous (+1), mercuric (+2)
molecular mass of an element when it exists in the form of molecular
or a compound in defined as the average mass of the molecule as compared to one atom of 6C12.
The sum of atomic masses of all the atoms present in
one molecules of a substance is called "molecular mass".
Chemistry is the branch of science which deals with the properties,
composition and structure of matter. Study
of chemistry also includes the laws and principles related to the
structure and inter-relations of elements
Chemistry has the task of investigating the materials of which our universe is made.Chemistry investigates chemical changes, conditions under which chemical changes occur.Chemistry also deals with the way in which similar changes can be brought about in laboratory and on a large scale in industries.
Chemistry is a very vast field.Chemistry is divided into a number of branches such as Organic chemistry, Inorganic chemistry, Physical chemistry, biochemistry, Applied chemistry, Nuclear chemistry etc.