Non-Molecular (extend arrangements) versus Molecular (discrete units)

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Non-Molecular (extend arrangements) versus
Molecular (discrete units) A. Non-Molecular
Substances Network Covalent versus Ionic Salt
versus Metallic B. Molecular Compounds Polar
versus Nonpolar
Know the physical properties of each type of
substance or compound A. physical state (solid,
liquid, gas) at room temperature 25C. B. high
boiling versus low boiling C. high melting versus
low melting D. hard versus brittle E. conductor
versus non-conductor F. solvent solubility
(soluble versus insoluble)
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The concept map on the next slide will be used as
a guide in understandingnon-molecular versus
molecularandhow physical structure influences
physical properties
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Supplemental packet p 99
A. be able to determine if a substance is
non-molecular or molecular
B. identify the attractive forces between each
substance represented. C. identify the physical
features of each substance represented.
D. state at least four physical properties for
each crystalline solid type. E. give examples
(name and formula) for each type of solid.
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Non-Molecular Substances extended arrangements
of repeating units every connecting atom is
closely associated with neighboring atoms
For example, C in diamond is covalently bond to
four other carbon atoms.
For example, titanium metal, M has four
electrons loosely surrounding it.
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Non-Molecular Substances extended arrangements
of repeating units every connecting atom is
closely associated with neighboring atoms

• Examples of each
• A. Network Covalent Substances
• (_ X _ X _ X _ X _ X _ X _ X _ X _)
  diamond, graphite, sand SiO2
• B. Ionic Salts
• ( M X- M X- M X- M X- )
  NaCl, MgSO4, BaSO4
• C. Metallic
• ( M e- M e- M e- M e- )
  Fe, Hg, alloys, steel

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Molecular Compounds individual molecules
behaving like independently of each other
A. Molecules are individual discrete units B.
Molecules are either polar or nonpolar C.
Between molecules, there are three types of
physical attractions
D. Physical attractions identified by
a hash mark not a covalent bond
____ chemical union
E. Learn the rules in order to identify when each
physical attraction.
F. hydrogen bonding (strongest) gt dipole-dipole
gt dispersion (weakest)
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An example of a hydrogen bonding interaction
force of attraction
Criteria for hydrogen bonding 1. Small
electronegative atom, X, in the structure of the
molecule. 2. H bonded to X where X N, O, F
HN, HO, HF 3. There is an available
electron pair attached to X
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An example of a dipole-dipole interaction force
of attraction
Criteria for dipole-dipole bonding 1. The
molecule is polar. 2. Molecule has a net dipole
2. Molecule does not contain a HN, HO, HF
bond.
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An example of a dispersion interaction force of
attraction
Criteria for dispersion bonding 1. The molecule
is nonpolar 2. No net dipole 3. No major
attractive force between molecules Until
molecules are pushed close together
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ATTRACTIVE force if molecules are pushed together
under pressure
Criteria for dispersion bonding 1. The molecule
is nonpolar 2. No net dipole 3. No attractive
force between molecules 4. Greater ATTRACTIVE
force if molecules are pushed together
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Temporary Dipole between nonpolar molecules
Permanent Dipole between polar molecules
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A. Melting point
Gauging the strength of chemical physical
attractiveness by considering the melting and
boiling point of a substance
Melting Point. The conversion of a solid to a
liquid at a given pressure. The stronger the
attractive forces between particles, the higher
the melting point of the solid.
B. Boiling point
Boiling Point In a very general sense, the
conversion of a liquid to a gaseous vapor at a
given pressure. Normal boiling point is the
conversion of a liquid to a gas at atmospheric
pressure. When a liquid boils, the pressure of
the gaseous vapor equals the external pressure
(atmospheric).
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Understanding how atoms and molecules stick
around chemical union versus physical
attractions thermal energy gained or lost
heating and cooling
Having high melting points And high boiling
points
Having low melting points and low boiling points
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Why is graphite (allotrope of pure carbon) used
as a lubricant? Every carbon atom in graphite is
trigonal planar in geometry.
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Why are diamonds (allotrope of pure carbon) a
girls best friend? No pressure, carbon atoms in
diamond are designed to stick around! Every
carbon atom in diamond is tetrahedral in geometry.
Not planar
Why is graphite (allotrope of pure carbon) used
as a lubricant? A trigonal planar in geometry
forms flat planes or sheets that slide
Planar
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Allotropes of Carbon
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Why are nonmolecular substances solids are room
temperature? Why is diamond the hardest substance
known? Why do metals conduct electricity and
heat? Why are ionic salts brittle?
Look closely at these generic structures. These
generic structures hold the answers to above
questions.
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Supplemental packet p 98, Know these physical
properties for each substance
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What happens when the pressure and stress on
butane is relieved? Molecules escape, separate
and disperse into a gas at 1 atmosphere
What can happen when tempers flare in a physical
relationship?
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molecular discrete units
In general, the stronger the physical
attraction The higher the melting boiling
point for the substance
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Why are molecules of water a solid at 0C but a
liquid at 25C? Why are molecules of carbon
dioxide a solid at -78C but gas at 25C? Why
are molecules like butane placed under high
pressure a liquid? Why are molecules like butane
under low pressure a gas?
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More on Evaluating Molecular Polarity
A. Structure determines a substances physical
property Lewis dot structure Molecular
Polarity (polar versus nonpolar)
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A. Be able to draw Lewis dot structure B.
molecules have ideal or non-ideal geometry
C.electronegativity differences determines
bond polarity
D. Overall Molecular Geometry determines
molecular polarity
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Symmetric versus Asymmetric
Symmetrical arrangement of polar bonds bond
polarities cancel
Asymmetrical arrangement of polar bonds bond
polarities dont cancel
NO Net Dipole Bond Dipoles Cancel
These Molecules Have a Net Dipole
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Molecular Substances (discrete units)

• Molecular Geometry and Bond Polarity
• Ideal geometries show have variable polarity
• Non-ideal geometries are generally polar

NO Net Dipole Bond Dipoles Cancel
These Molecules Have a Net Dipole
variable polarity
polar
These Molecules Have a Net Dipole
BUT, these ideal geometries here are polar
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Molecular Polarity Solubility

• Determining the polar nature of molecular
  substances
• Evaluating Substance Structure
• Physical Observations - Common Sense Approach
• Solubility (solute/solvent interactions) to gauge
  molecular polarity
• Like will dissolve Like
• Polar solutes will have highest solubility in
  polar solvents
• Nonpolar solutes will have highest solubility in
  nonpolar solvents
• Polar solutes will have lowest solubility in
  nonpolar solvents
• Nonpolar solutes will have lowest solubility in
  polar solvents

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Substance solubility in water Like dissolves
Like can be used to gauge Molecular Polarity

• Sugar dissolves in water
• Thus sugar molecules must be polar
• Methanol CH3OH dissolves in water
• Thus methanol molecules must be polar
• Gasoline -(CH 2)- does not dissolve in water
• Thus gasoline molecules must be NONPOLAR

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A gasoline molecule is a hydrocarbon made of
repeating ( CH2 ) units is non-polar NO net
dipole
hydrocarbons are non-polar
All dipoles cancel
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Nonpolar does not dissolve Polar
gasoline does not dissolve in
water
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Nonpolar does not dissolve Polar
hydrogen, H2 does not dissolve in
water
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Polar physically dissolves in Polar
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The highlighted area is an example of hydrogen
bonding
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Like dissolves Like

• Polar dissolves Polar
• Vitamin B11 (folic acid)
• Vitamin C (ascorbic acid)

Where ever there are N and O atoms, there are
polar areas
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Like dissolves Like

• Non-Polar dissolves Non-Polar
• Vitamin A, retinol (fat soluble lipid soluble)
• triacylglycerine, a non-polar human body fat
  (lipid)

Vitamins D, E, and K are fat soluble as
well What would their overall polarity be?
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Predict whether the substance is Polar or Nonpolar
sugar C6H12O6 baby oil
C20H42 candle wax C40H82 ethanol
C2H5OH oxygen
O2 iodine I2
polar nonpolar nonpolar polar nonpolar nonpol
ar