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6. -Ice has hexagonal 3D crystal structure formed due to to
intermolecular H-Bonding which leave almost half the space
vacant.
-Both ice and water structure almost same.
-On melting of ice some H-bond are broken and vacant spaces
are occupied by water molecules, and they are joint more
closely.
-In solid ice, vacant space is
more then liquid water.
-Therefore the
density of ice is less then
water.
10. Characteristics of solid
1. Solid fixed composition- has fixed mass, volume,
shape and Density. Order of density: Solid >Liquid
>Gas. Exception: Dice < Dwater
2. in solids- Intermolecular distance is shortest. hence
solid are incomopressible.
3. Solid are HARD and .
4. Solid have strongest intermolecular force of
attraction.
-Solid with weak IMF - Low M.P.
-Solid with strong IMF - high M.P.
5. Soilid fixed position and posses Oscillatory motion.
becouse of low thermal energy- means Temperature.
Soild with weak IMF - Thermal energy high.
Soild with strong IMF- Thermal energy low.
38. Why is glass considered a supercooled liquid?
Ans: Glass is an amorphous solid. Like liquids, it has a tendency to
flow, though very slowly. This can be seen from the glass panes of
windows or doors of very old buildings which are thickerat the bottom
than at the top. Therefore, glass is considered as a supercooled liquid.
Glass are the transparant
medium obtain by fuseing
together SiO2, Na2O, B2O3.
Amorphouse
solid.
800 varities of
glass.
39. Composition
of Glass
Quartz
Glass/Silica gel
Green Glass
Blue GlassYellow GlassRed Glass
Sodalime
Glass
Pyrex Glass
60-80% SiO2+10-
25% B2O3+ Al2O3.
75% SiO2+15% Na2O
+ 10% CaO.
SiO2+trace amount
Cu & Au
SiO2 + UO2. SiO2 + CuO/CoO.
SiO2 +
CuO/Fe2O3.
SiO2
44. Bonding in Ice and Water
-Structure of liquid water and solid ice are almost identical.
-ice has hexagonal 3D crystal structure formed due to H-bonding.
-Each O-H bond is polar, hence H2O is polar molecule. contain dipole
dipole interaction.
-in ice, H2O molecules are linked forming a tetrahedral arrangement.
-in this arrangement, 2 covalently bonded H-atom and 2 H-atoms
bonded by H-bonding are at 4 corners of the tetrahedral.
O
H
H
HH
142. Relation for the density of unit cell
In a cubic crystal, let
a = Edge length of the unit cell.
d = Density of the solid substance.
M = Molar mass of the substance.
Then, volume of the unit cell = a3
Again, let
z = Number of atoms present in
one unit cell
m = Mass of each atom
mass of the unit cell = Number of atoms
in the unit cell × Mass of each atom
= z × m
But, mass of an atom, m
Therefore, density of the unit
cell,
212. Example- Fe3O3, Fe3O4 (magnetite), ferrites such as MgFe2O4 and
ZnFe2O4.
Substance which are expected to posses large magnetism on the
basis of the unpaired electrons but actually have small net magnetic
moments are called Ferrimagnetic substances.
Ferrimagnetic substances are weakly attracted by a magnetic
field as compared to ferromagnetic substances.
On heating, these substances become paramagnetic.
213. Anti-ferromagnetism
Substances which are expected to possess paramagnetism
or Ferromagnetism on the basis of unpaired electron but
actually they posses zero net magnetic moment are called
anti Ferromagnetic substances.
e.g. MnO, Mn2O3, MnO2.
221. High electric resistivities but good supporter of electric field.
This is due to the reason that electrons in a dielectric substances are
tightly pack to each other.
Can store energy /charges.
Polarization takes place because nuclei are attracted to one side and
the electron cloud to the other side.
There may also be permanent dipoles in the crystal called Dipole
Dipole interaction.
Dielectric properties
Since the molecule is linear, these two bond dipoles cancel each other
out then overall dipole moment ( μ=0).
223. Piezoelectricity (or pressure electricity)
Conversely, if electric field is applied to such crystals, atomic
displacement takes place resulting into mechanical strain. This is
sometimes called Inverse piezoelectric effect.
224. ammonium dihydrogen phosphate (NH4H2PO4) and quartz.
The crystals are used as pick – ups in record
players where they produce electrical signals
by application of pressure.
titanates of barium and lead, lead zirconate
(PbZrO3) - It is used in capacitors,
electromechanical transducers(converts an
electrical signal into sound waves (as in a
loudspeaker) or converts a sound wave into
an electrical signal (as in the
microphone,ultrasonic generators and sonar
detectors). and nonlinear optics.
225. It is a Greek word derived, means electricity generated by heat.
Some piezoelectric crystals when heated or cooled produce a small
electric current. The electricity thus produced is called
pyroelectricity.
Pyroelectricity:
TV switch Temporary
voltage stored karte hai.
226. e.g. Barium titanate (BaTiO3) sodium potassium tartarate (Rochelle
salt) and potassium dihydrogen phosphate (KH2PO4).
In some of the piezoelectric crystals, the dipoles are permanently
polarized even in the absence of the electric field. However on
applying electric field, the direction of polarization changes
Ferroelectricity:
Ferromagnetic
All ferroelectric solids are
piezoelectric but the reverse is
not true.
227. e.g. Lead zirconate (PbZrO3)
In some crystals, the dipoles align themselves in such a way, that
alternately, they point up and down so that the crystal does not
posses any net dipole moment. Such crystal are said to be anti
Ferroelectric
Anti Ferroelectricity:
All ferroelectric solids are
piezoelectric but the reverse is
not true.
229. Electrical resistance decreases with decreases in temperature and
becomes almost zero near the absolute zero.
A substance is said to be superconducting when it offers no
resistance to the flow of electricity.
Super Conductivity
The phenomenon was first discovered by Kammerlingh Onnesin 1913
when he found that mercury becomes superconducting at 4 K.
The temperature at which a substance starts
behaving as super conductor is called
transition temperature.
230. Most metals have transition temperatures between 2K -5K. Certain
organic compounds also becomes superconducting below 5K. Such
low temperature can be attained only with liquid helium which is
very expensive.
Super Conductivity
Super conductivity materials have great technical potentials.
power transmission
levitation transportation (trains which
move in air without rails).magnetic train.
Uses
231. Certain alloys of niobium have been found to be superconducting at
temperature as high as 23 K.
Super Conductivity
Since 1987, many complex metal oxides have been found to possess
super conductivity at some what higher temperature.
Hinweis der Redaktion
intermolecular force wo hai jo 2 particle ko ek dusre ke karib rakhti hai.