DEFINITIONS
AD
1. TEMPERATURE
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.
CONVERSION
Centigrade & Kelvin
Tk = Tc + 273
Centigrade & Fahrenheit
C/5 = (F-32) /9
SI
R
SA
JJ
2. VOLUME
Volume is defined as
" The space occupied by a body is called its volume."
SYMBOL
Volume is denoted by "V
UNITS
a) m3
b) dm3
c) cm3
d) mm3
e) Litre
f) Milli litre
3. MASS
The quantity of matter contained in a body is called its "Mass".
SYMBOL
Mass is denoted by "m".
UNITS
a) Kilogram
b) Gram
c) Milligram
d) Microgram
4. DENSITY
Mass per unit volume of a substance is called its "Density".
FORMULA
UNIT
a) Kg / m3
b) gm / cm3
c) gm /litre
d) gm / dm3
5. MOLE
"Atomic mass or formula mass or molecular mass of a
substance expressed in grams is called MOLE".
1023
Or
atoms or molecules or ions is called "mole"
Mass of a substance contains 6.02 x
For example:
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
FORMULA
AD
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 NUMBER".
It is denoted by NA.
For Example.
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.
SI
R
SA
JJ
7. LAW OF DEFINITE PROPORTION
STATEMENT
According to the law of definite proportion
"Every sample of pure substance always contains same elements
in fixed proportion regardless of its method of preparation"
EXPLANATION
We can obtain or prepare water by a number of methods but water obtained from any source always
contain 11.11% hydrogen and 88.88% oxygen.
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 mass of
substance to the mass of an equal volume of water at a particular temperature.
FORMULA
Specific gravity = mass of substance / mass of an equal volume of water
UNIT
It has no unit.
9. GRAM ATOMIC MASS
"Atomic mass of an element expressed in gram is called gram atomic mass"
For example:
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 grams is called gram molecular mass."
For example:
Gram molecular mass of hydrogen gas=2 gm.
Gram molecular mass of oxygen gas =32gm.
Gram molecular mass of HCl = 36.5 gm
11. ELEMENT
"Element is defined as a pure substance in which all the atoms
have same chemical properties and have same atomic number"
For example:
Carbon, sodium, hydrogen, chlorine, copper, gold, iron etc.
TYPES OF ELEMENTS
Elements can be divided into two classes.
1. Metals.
2. Nonmetals.
METALS
VALENCY
1
2
1
3
SA
JJ
ELEMENT
Na, K
Ca, Mg
F, Cl
N
AD
They have shine on their surface.
They are good conductors of electricity and heat.
They reflect light.
Metals are ductile.
Metals are malleable.
EXAMPLE
Cu, Fe, Au, Na, Ca etc
NON-METALS
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.
EXAMPLE
H2, C, Cl2, O2, N2 etc
12. VALENCY
Valency is defined as
"the combining capacity or combining power of an element with the 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
is called valency.
EXAMPLES
SI
R
13. MOLECULE
The smallest unit of an element or compound, which can exist independently, is called "molecule".
14. EMPIRICAL FORMULA
"Empirical Formula is that formula which expresses the relative number
of each kind of atoms present in the molecule of a compound"
OR
"The formula of a compound which expresses the ratio in which atoms of
different elements are combined in a molecule"
Empirical 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.
EXAMPLE
Empirical Formula of Benzene = CH
Empirical Formula of Glucose = CH2O