Transcript Photo chapter opener 16 Red Beryl, Be3Al2Si6O18-

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16a–1
Bubble Pressure
The net upward force on the top
hemisphere of the bubble is just the
pressure difference times the area of the
equatorial circle:
The surface tension force downward
around circle is twice the surface tension
times the circumference, since two
surfaces contribute to the force:
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16a–2
毛細現象
The height h to which capillary
action will lift water depends upon
the weight of water which the
surface tension will lift:
The height to which the liquid can
be lifted is given by
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High T
Low T
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16a–4
Low T
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High T
16a–5
Classifying Intermolecular Forces
1.Strong ionic attraction
Recall lattice energy and its relations to properties of solid. The more ionic, the
higher the lattice energy.
2.Intermediate dipole-dipole forces
Substances whose molecules have dipole moment have higher melting point or
boiling point than those of similar molecular mass, but their molecules have no
dipole moment.
3.Weak London dispersion forces or van der Waal's force These forces alway
operate in any substance. The force arisen from induced dipole and the interaction
is weaker than the dipole-dipole interaction. In general, the heavier the molecule,
the stronger the van der Waal's force of interaction.
4.Hydrogen bond
Certain substances such as H2O, HF, NH3 form hydrogen bonds,.
5.Metallic bonding
Forces between atom in metallic solids belong to another category. Valence
electrons in metals are rampant. They are not restricted to certain atoms or bonds.
Rather they run freely in the entire solid, providing good conductivity for heat and
electric energy.
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Strength of Intermolecular Forces
Covalent
bonds >
400 kcal >
Hydrogen
bonding >
12-16 kcal
>
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Dipole-dipole
interactions >
London
forces
5-0.5 kcal >
less than
1 kcal
16a–7
Dipole-dipole interactions
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Hydrogen Bonds
A covalent bond between -O-H ---- :OA covalent bond between -N-H----- :OA covalent bond between F-H ------ :OA covalent bond between -O-H ---- :NA covalent bond between -N-H---- :NA covalent bond between F-H ----- :NA covalent bond between -O-H ----- :FA covalent bond between -N-H ---- :F-
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The phase diagram of water is complex
If water behaved
more typically as a
low molecular
weight material, its
phase diagram may
have looked rather
like this:
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16a–13
What Kinds of Materials Form Liquids at
Room Temperature
(1)the strength of the bonds between the particles that
form the substance
(2) the atomic or molecular weight of these particles
(3) the shape of these particles
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Molecular Shape
Compound
Melting Point (oC)
Boiling Point (oC)
-130
36.1
-159.9
27.8
-16.5
9.5
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The Shape of the molecule also matters
n-pentane
bp= 309.4 k
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Categories of Solids Based on the Solid Pack
•Crystalline solids are three-dimensional analogs
of a brick wall. They have a regular structure, in
which the particles pack in a repeating pattern from
one edge of the solid to the other.
•Amorphous solids have a random structure, with
little if any long-range order.
•Polycrystalline solids are an aggregate of a large
number of small crystals or grains in which the
structure is regular, but the crystals or grains are
arranged in a random fashion.
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Categories of Solids Based on Bonds
ionic ........ polar ........ covalent
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Crystal Structure
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Other structures
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Structure of NaCl: an ionic crystal
Sodium chloride crystals are
brittle
Why 6-coordinated ?
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Grains of nanophase palladium magnified
200,000 times by an electron microscope.
Source: Nanophase Technologies Corporation
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Electrical Properties
•Metallic Conductors, e.g. Cu, Ag...
•Semiconductors, e.g. Si, GaAs
•Superconductors, e.g. Nb3Sn, YBa2Cu3O7
•Electrolytes, e.g. LiI in pacemaker batteries
•Piezoelectrics, e.g. a Quartz (SiO2) in watches
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