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Chapter 11 – Intermolecular Forces, Liquids, and Solids. Which factor(s) affect the physical properties of a substance? Why does water boil at 100°C and freeze at 0°C? Why does high pressure and low temperature solidify most gasses? Why can’t hydrogen be solidified? In this unit we - PowerPoint PPT Presentation
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Chapter 11 – Intermolecular Forces, Liquids, and Solids
Which factor(s) affect the physical properties of a substance? Why does water boil at 100°C and freeze at 0°C? Why does high pressure and low temperature solidify most gasses? Why can’t hydrogen be solidified? In this unit we will look at the factors that affect the physical properties of liquids and solids.
Intermolecular Forces, Liquids, and Solids
• Intermolecular Forces– Forces of attraction between 2 or more other
molecules in a substance.
Intermolecular Forces, Liquids, and Solids
• Intermolecular Forces– 3 types: London Dispersion Forces (weakest),
Dipole-Dipole, and Hydrogen Bonding (strongest).
Intermolecular Forces, Liquids, and Solids
• Intermolecular Forces– London Dispersion Forces: Weak forces of
attractions caused by the attraction between the protons in one molecules and the electrons in another molecule.
Intermolecular Forces, Liquids, and Solids
• Intermolecular ForcesoLondon Dispersion Forces: • Generally, substances that only have
LDF’s have low melting and vaporization points. • But substances with higher molecular
weights can have so many LDF’s that they will have high melting and vaporization points.
Intermolecular Forces, Liquids, and Solids
• Intermolecular Forceso London Dispersion Forces:
Halogen Molecular Weight
(amu)Boiling Point (K)
F2 38.0 85.1
Cl2 71.0 238.6
Br2 159.8 332.0
I2 253.8 457.6
Intermolecular Forces, Liquids, and Solids
• Intermolecular Forceso London Dispersion Forces:
Noble Gas Molecular Weight
(amu)Boiling Point (K)
He 4.0 4.6
Ne 20.2 27.3
Ar 39.9 87.5
Kr 83.8 120.9
Intermolecular Forces, Liquids, and Solids
• Intermolecular Forceso Dipole - Dipole Forces: Weak forces of attractions
caused by the attraction between the oppositely charged poles of two or more molecules.
Intermolecular Forces, Liquids, and Solids
• Intermolecular Forceso Dipole - Dipole Forces: Therefore, dipole-dipole
interactions only develop within polar substances.
Intermolecular Forces, Liquids, and Solids
• Intermolecular Forceso Hydrogen Bonding: Forces of attractions between a
hydrogen atom of one molecule and a fluorine, oxygen, or nitrogen, of another molecule.
Intermolecular Forces, Liquids, and Solids
• Intermolecular Forceso Hydrogen Bonding: Ammonia’s trigonal pyramidal
shape allows the hydrogen atoms of one molecule to be attracted to the nitrogen on another.
Intermolecular Forces, Liquids, and Solids
• Intermolecular Forceso Hydrogen Bonding:
Intermolecular Forces, Liquids, and Solids
• Intermolecular Forceso Hydrogen Bonding:
o Ice is less dense than liquid water due to hydrogen bonding.
oWhen H-Bonding is maximized in the formation of ice, large open spaces are created.
Intermolecular Forces, Liquids, and Solids
• Intermolecular Forces
Interacting Molecules or ion
Polar Molecules? Ions Present? Polar Molecules and Ions Present?
LDF’s Diplole H-Bonding Ion-Dipole Ionic Bonding Dipole
Weakest IMF’s -------------------------------> Strongest IMF’s
Intermolecular Forces, Liquids, and Solids
• Properties of Liquidso Viscosity – The measure of the resistance of a liquid to
flow.
Intermolecular Forces, Liquids, and Solids
• Properties of Liquidso Viscosity – Affect by temperature and molecular weight.
Temperature – IMF’s are overcome with higher temperature.Molecular Weight – The larger the molecule, the more
‘tangled’ it becomes, thus resisting flow.
Intermolecular Forces, Liquids, and Solids
• Properties of Liquidso Surface Tension – A measure of the inward forces that
must be exerted to overcome to expand the surface of a liquid.
Intermolecular Forces, Liquids, and Solids
• Properties of Liquidso Surface Tension – Cohesive vs Adhesive Forces
Cohesive Forces – Forces among molecules in a liquid due to IMF’s.
Adhesive Forces – Forces between the molecules of a substance and the surface of a material.
Intermolecular Forces, Liquids, and Solids
• Phase Changes
Intermolecular Forces, Liquids, and Solids
• Phase Changeso Heat of Fusion (ΔHfus): The amount of energy to melt 1 mole of a
substance. o What patter do you see in the heat of fusion of these substances?
ΔHfus H2O = 6.01 kJ / mol
ΔHfus C4H10 = 5.00 kJ / mol
ΔHfus Hg = 23.0 kJ / mol
Intermolecular Forces, Liquids, and Solids
• Phase Changeso Heat of Vaporization (ΔHvap): The amount of energy to vaporize 1
mole of a substance.oWhat pattern do you see in the heat of vaporization of these
substances?
ΔHvap H2O = 40.7 kJ / mol
ΔHvap C4H10 = 24.0 kJ / mol
ΔHvap Hg = 58.0 kJ / mol
Intermolecular Forces, Liquids, and Solids
• Heating curves and Cooling Curves
Intermolecular Forces, Liquids, and Solids
• Heating curves and Cooling Curves
Intermolecular Forces, Liquids, and Solids
• Heating curves and Cooling Curves
Intermolecular Forces, Liquids, and Solids
• Cooling Curve for Solutions
Intermolecular Forces, Liquids, and Solids
• Phase Diagrams
Phase Diagrams for Carbon Dioxide
Intermolecular Forces, Liquids, and Solids
• Phase Diagrams
Intermolecular Forces, Liquids, and Solids
• Phase Diagrams• Triple Point – The combination of temperature
and pressure that a substance exists as a solid, liquid, and a gas at the same time.
• Critical point – The maximum temperature by which a substance can not longer be liquified
Intermolecular Forces, Liquids, and Solids
• Vapor Pressure• The pressure exerted by the gas above a liquid once
dynamic equilibrium has been established between the liquid molecules and gas molecules.
Intermolecular Forces, Liquids, and Solids
• Vapor Pressure• Dynamic Equilibrium – The rate of evaporation equals
the rate of condensation.
Intermolecular Forces, Liquids, and Solids
• Vapor Pressure vs Intermolecular Forces• The stronger the IMF’s, the more difficult it is for a
molecule to escape to the gas phase. Therefore its vapor pressure will be lower.
• The weaker the IMF’s, the higher the vapor pressure.
Intermolecular Forces, Liquids, and Solids
• Vapor Pressure
Intermolecular Forces, Liquids, and Solids
• Solids• Amorphous Solids: Solids that lack any molecular
organization.
Intermolecular Forces, Liquids, and Solids• Solids• Crystalline Solids:
– Solids that have a high degree of molecular organization.– Crystals are three-dimensional shapes that have flat surfaces and
angled corners.
Intermolecular Forces, Liquids, and Solids• Solids• Crystalline Solids: Geodes
Intermolecular Forces, Liquids, and Solids• Solids• Crystalline Solids: – Unit Cells: The repeating three-dimensional shape of a
crystalline solid.– Crystal Lattice: Many unit cells making an overall crystal.
Intermolecular Forces, Liquids, and Solids
• Solids• Crystalline Solids: –All ionic compounds can be explained with 7 different
types of unit cells.
–We will take a close look at 3 common types; primitive cubic, body-centered cubic, and face-centered cubic.
Intermolecular Forces, Liquids, and Solids
• Crystalline Solids• Primitive Cubic
Intermolecular Forces, Liquids, and Solids
• Crystalline Solids• Body-Centered Cubic
Intermolecular Forces, Liquids, and Solids
• Crystalline Solids
Intermolecular Forces, Liquids, and Solids
• Crystalline SolidsClose Packing Spheres
Intermolecular Forces, Liquids, and Solids
• Crystalline SolidsCoordination Number – The number of
particles that surround one specific particle in solid.
Intermolecular Forces, Liquids, and Solids
• Crystalline SolidsCoordination Number – What is the
coordination numbers for the following examples?
Intermolecular Forces, Liquids, and Solids
• Crystalline SolidsHollow Spheres
Rice University (1985): A 60-Carbon hollow ball of carbon is discovered.
Intermolecular Forces, Liquids, and Solids
• Crystalline SolidsHollow Spheres
These structures were called buckminsterfullerenes or ‘buckyballs’.
Buckminster Fuller: Architect who created geodome shapes.
Intermolecular Forces, Liquids, and Solids
• Crystalline SolidsHollow Spheres
These structures were called ‘buckyballs’.Buckminster Fuller: Architect who created
geodome shapes.
Intermolecular Forces, Liquids, and Solids
• Crystalline SolidsHollow Spheres
Buckyballs are found in nature and even been identified in deep outer space in clouds surrounding stars.
Intermolecular Forces, Liquids, and Solids
• Crystalline SolidsHollow Spheres
Buckyballs have potential uses in medicine, lubricants, and computers.
Intermolecular Forces, Liquids, and Solids
• Crystalline SolidsBuckminsterfullerenes
Nanotubes
Intermolecular Forces, Liquids, and Solids
• Covalent Network SolidsMolecular substances in which all of the atoms
are connected by a network of covalent bonds.
Intermolecular Forces, Liquids, and Solids
• Covalent Network SolidsDiamonds versus graphite
Intermolecular Forces, Liquids, and Solids
• Summary of Crystalline solids
Type of Solid Particles Forces Properties Examples
Molecular Atoms or Molecules
LDF, dipole-dipole, H-Bonding
Soft, low melting points
Ar, CH4, CO2, ice
Covalent Network
Atoms connected by
covalent bonds
Covalent Bonds Very hard, very high metltng
points
Diamonds, quartz, graphite,
glass (SiO2)
Ionic Cations and anions
Electrostatic Interactions
Hard, brittle, high melting
points
NaCl, Ca(NO3)2
Metallic atoms Metallic Bonds Soft or hard, low or high melting
points
Cu, Fe, Al