1. Water’s Properties Hexagonal crystal shape Molecule is polar.
Hydrogen bonding
Ice floats.
Expands during freezing until -4.0 º C.
Solid form is less dense than liquid
Surface tension:
Water “beads” on smooth surfaces.
Insects walk on water surfaces.
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2. Solids Crystalline solids Amorphous solids: (Without shape)
Particles are arranged in an orderly, geometric, repeating pattern.
Examples: Emerald, diamond, calcite
Amorphous solids: (Without shape)
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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3. Bonding in Solids Molecular solids Covalent Network solids
Most are liquids or gases at room temp.
Ex. H2O, Ar
Covalent Network solids
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
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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4. Silicon Doping (N-type is more conductive when voltage is applied.)
O:O:O:O: O:O:O:O: O:O:O:O:
O:O:O:O: O:B.O:O: O:P:O:O:
Silicon (4 e-) P-type N-type
semiconductor hole created extra e- in lattice
p = positive n= negative
To customize
conductive properties, add a dopant such as B (p-type), As or P (n-type)
.. … .. ..
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5. Allotropes (different forms of same element)
Carbon (C)
Diamond
Graphite (pencil “lead”)
Charcoal
Sulfur (S)
Rhombic (puckered ring)= S8
Phosphorous (P)
White phosphorous, P4 is most reactive, tetrahedral
Red phosphorous is more stable.
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6. Isomers (Ex. C5H12) Same formula, different structure
Be careful with “linear” hydrocarbons. A straight chain may be shown as bent H
H H H H H H H H H H-C-H
H-C-C-C-C-C-H H-C-C-C-C-H H H
H H H H H H H H H-C-C-C-H
H-C-H H H
H H-C-H
butane
butane
2,2-dimethyl propane
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7. Isomers: cis- and trans-Cl H
cis-dichloroethene C H Cl
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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8. 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
0.009 mol
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9. Hydrocarbon Solubility
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.
An oxygen atom in these molecules is capable of forming hydrogen bonds between the oxygen of the hydrocarbon and the hydrogen of water.
Glucose has 5 O atoms and 6 C atoms: It is very soluble in water.
The number of carbon atoms determines the degree of polarity and therefore the solubility 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.
Compare vitamin A and C: A is a large molecule with many carbon atoms and an OH group.
C is smaller with 4 –OH groups and a C==O. Therefore A is not very soluble in water: It is fat-soluble. C is more polar and is very soluble in water.
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10. Functional Group Review
aldehyde H R
ketone C R O O R
ether O O
carboxylic acid C OH R R C
ester O
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11. Common Organic Reaction
carboxylic acid C OH R + HO R
alcohol O R C
ester
water +
H2O
This is a condensation reaction.
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