Water’s Properties

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Hexagonal crystal shape
Molecule is polar.
Hydrogen bonding
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Ice floats.
Expands during freezing until -4.0 º C.
Solid form is less dense than liquid
Surface tension:

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Water “beads” on smooth surfaces.
Insects walk on water surfaces.
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Solids

Crystalline solids
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Amorphous solids: (Without shape)
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Particles are arranged in an orderly, geometric, repeating
pattern.
Examples: Emerald, diamond, calcite
Particles are arranged randomly.
Examples: Glass, plastic
Network solids


Covalent bonds, usually single element arranged in orderly
pattern
Examples: Diamond, graphite
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Bonding in Solids

Molecular solids


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Covalent Network solids


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Covalent bonds are stronger than IM forces, so substances
have relatively high melting points and are harder than
molecular ones.
Ex: quartz, diamond, graphite, SiO2
Ionic solids



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Most are liquids or gases at room temp.
Ex. H2O, Ar
Ionic bonds are the strongest of all
Strength of bond depends on charge: Higher charges =
higher melting point.
Crystal structures: Examples
 Face-centered cubic, body-centered cubic, hexagonal
close-packed structures.
Metallic Solids (metallic bonds)
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Silicon Doping
(N-type is more conductive when voltage is applied.)
O:O:O:O:
O:O:O:O:
Silicon (4 e-)
semiconductor
P-type
hole created
p = positive
.. .. .. ..
O:O:O:O:
.. .. .. ..
.. .. .. ..
O:B.O:O:
.. .. .. ..
O:O:O:O:
.. … .. ..
O:P:O:O:
.. .. .. ..
N-type
extra e- in lattice
n= negative
To customize
conductive properties, add a dopant such as B (p-type),
As or P (n-type)
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Allotropes
(different forms of same element)

Carbon (C)

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Sulfur (S)


Diamond
Graphite (pencil “lead”)
Charcoal
Rhombic (puckered ring)= S8
Phosphorous (P)


White phosphorous, P4 is most reactive,
tetrahedral
Red phosphorous is more stable.
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Isomers
(Ex. C5H12)
Same formula, different structure
 Be careful with “linear” hydrocarbons. A
straight chain may be shown as bent
H
HHHHH
HHHH
H-C-H
H-C-C-C-C-C-H H-C-C-C-C-H
H H
HHHHH
HHH
H-C-C-C-H
H-C-H
H H
butane
H
H-C-H
butane
H

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2,2-dimethyl propane
6
Isomers: cis- and transCl
Cl
C
H
H
C
C
H
Cl
cis-dichloroethene



Cl
C
H
trans-dichloroethene
Stereoisomer: Atoms are connected the same
but have different arrangement in space
Enantiomer: Stereoisomers are mirror images of
each other
A racemic mixture contains equal amounts of
enantiomers
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Boiling Points
Some general observations for hydrocarbons with 1-8 C atoms:
 The more soluble a substance is in water, the higher its boiling
point.
 The more “order” (ie, straight chain = order), the higher the b.p.
 The more carbons, the more bonds there are to break, so the
higher the b.p.
Substance
Boiling Point
Solubility in 100 g H2O
1-propanol (C5H11OH)
138ºC
0.030 mol
propane (C5H12)
36ºC
0.001 mol
2-methyl butane (C5H12)
28ºC
0.005 mol
2,2-dimethyl propane (C5H12) 9ºC
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0.009 mol
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Hydrocarbon Solubility

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O atom within a substance can form hydrogen-bond
with water
Glucose, C6H12O6, is very soluble in water.
More carbons = Less polar= Less soluble in water
The more carbon atoms, the polar group
(C==O or –OH) is increasingly smaller part of the
molecule, so more carbons results in more nonpolar
behavior
To increase solubility in water, increase the number
of polar groups so that there are more chances of
hydrogen-bonding (or ionic bonding) with water.
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Functional Group Review
O
R
O
C H
R O
R
ether
aldehyde
C OH
C R
ketone
O
R
R
O
R
carboxylic acid
C O
R
ester
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Common Organic Reaction
O
R
C OH + HO
carboxylic acid
R
alcohol
O
R
C O
ester
R
+ H2O
water
This is a condensation reaction.
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