Section 10.1 Section 10.1 Intermolecular ForcesIntermolecular Forces

Based on the enthalpy values and what you Based on the enthalpy values and what you know of solids, liquids, and gases, which know of solids, liquids, and gases, which two states of matter are most similar? two states of matter are most similar? Which is most unique?Which is most unique?

Hfus = 6.02 kJ/molHvap = 40.7 kJ/mol

Answer Now

Liquids and Liquids and SolidsSolids Chapter 10Chapter 10

Types of Intermolecular Types of Intermolecular ForcesForces

Dipole-DipoleDipole-Dipole Molecules must have dipoleMolecules must have dipole Opposites attractOpposites attract Attractions weaken as distance between Attractions weaken as distance between

dipoles increase.dipoles increase. Hydrogen BondingHydrogen Bonding

Type of Dipole-DipoleType of Dipole-Dipole Between H and any highly EN atom. (ie: Between H and any highly EN atom. (ie:

F, Cl, O)F, Cl, O) Extremely strong attractionExtremely strong attraction

Types of Intermolecular Types of Intermolecular Forces, 2Forces, 2

London Dispersion ForcesLondon Dispersion Forces Noble Gases and Non-Polar MoleculesNoble Gases and Non-Polar Molecules Temporary Dipoles formTemporary Dipoles form Sometimes called Induced Dipole Sometimes called Induced Dipole

ForcesForces Weaker than Dipole-DipoleWeaker than Dipole-Dipole In molecules with large atoms, In molecules with large atoms,

dispersion forces are often more dispersion forces are often more important than dipole forces.important than dipole forces.

Properties and Properties and Intermolecular ForcesIntermolecular Forces

What properties do intermolecular What properties do intermolecular forces affect?forces affect? Boiling PointBoiling Point Freezing PointFreezing Point Vapor PressureVapor Pressure Surface TensionSurface Tension Capillary ActionCapillary Action ViscosityViscosity

Practice ProblemsPractice Problems

Identify the most Identify the most important types of important types of intermolecular forces intermolecular forces present in each of the present in each of the following substances:following substances:

In each of the In each of the following group of following group of substances, pick the substances, pick the one what has the one what has the given property and given property and justify your answer:justify your answer:

Highest boiling point: Highest boiling point:

HCl, Ar, or FHCl, Ar, or F22

Highest freezing point: Highest freezing point:

HH22O, NaCl, or HFO, NaCl, or HFLowest Boiling Point: Lowest Boiling Point:

CHCH44, CH, CH33CHCH33, or , or CHCH33CHCH22CHCH33

ArArHClHClCHCH44

COCONaNONaNO33

Vapor PressureVapor Pressure

Vapor Pressure of a liquid occurs when Vapor Pressure of a liquid occurs when some particles are vaporized just above the some particles are vaporized just above the surface of the liquid.surface of the liquid.

Volatile liquids have higher vapor pressuresVolatile liquids have higher vapor pressures REMEMBER: REMEMBER:

PPatmosphereatmosphere = P = Pvaporizationvaporization + P + PHgColumnHgColumn

The heat of vaporization (The heat of vaporization (HHvapvap) is the ) is the amount of heat required to change 1 mole amount of heat required to change 1 mole of liquid to gas.of liquid to gas.

Endothermic values Endothermic values

Vapor Pressure Vapor Pressure RelationshipsRelationships

Vapor Pressure Vapor Pressure CalculationsCalculations

lnPlnPvapvap = -( = -(HHvapvap/R)(1/T)/R)(1/T)

Use 8.314 J/Kmol for R.Use 8.314 J/Kmol for R.

lnPlnPvapvap = -( = -(HHvapvap/R)(1/T)/R)(1/T)

Use 8.314 J/Kmol for R.Use 8.314 J/Kmol for R.

The vapor pressure of water at 25oC is 23.8 torr and the Hvap of water is

always 43.9 kJ/mol. Calculate the vapor

pressure of water at 50oC.

Try Me Try Me ProblemProblem

Heating CurveHeating Curve

When a solid is heated, it will absorb When a solid is heated, it will absorb energy (increase temp) until it begins to energy (increase temp) until it begins to melt.melt.

At melting point At melting point and at boiling point, and at boiling point, the two states of the two states of matter are present. matter are present.

No change in No change in temperature occurs temperature occurs until all particles are until all particles are converted.converted.

Phase DiagramsPhase Diagrams

Relate the temperature, pressure, Relate the temperature, pressure, and state of matter for a substance. and state of matter for a substance.

Triple Point is the point at which all Triple Point is the point at which all three states of matter are present.three states of matter are present.

Critical Point is the last temperature Critical Point is the last temperature and pressure combination at which and pressure combination at which it is possible to condense particles to it is possible to condense particles to a liquid.a liquid.

Phase Diagram of WaterPhase Diagram of Water

Evaporation

Sublimat

ion

Melting

What IS Boiling Point?What IS Boiling Point?

MythMyth FactFact

Special CasesSpecial Cases Superheated liquid: A liquid that is Superheated liquid: A liquid that is

heated so rapidly that it is actually at a heated so rapidly that it is actually at a temperature that is above the boiling temperature that is above the boiling point, but has not evaporated.point, but has not evaporated.

Supercooled liquid: A liquid that is cooled Supercooled liquid: A liquid that is cooled so rapidly that it is actually at a so rapidly that it is actually at a temperature that is below the freezing temperature that is below the freezing point, but has not solidified.point, but has not solidified.

UNSTABLE !

Section 10.3 Structures and Section 10.3 Structures and Types of SolidsTypes of Solids

Ionic solidsIonic solids Molecular solidsMolecular solids Atomic solidsAtomic solids

All types of solids form crystal All types of solids form crystal lattices. lattices.

The smallest repeatable unit inside a The smallest repeatable unit inside a crystal lattice is a unit cell. crystal lattice is a unit cell.

Unit CellsUnit Cells

Simple cubic: one atom at each Simple cubic: one atom at each vertex. Polonium metalvertex. Polonium metal

Basic format Binary Compound

Unit Cells, 2Unit Cells, 2

Body centered cubic: at each vertex Body centered cubic: at each vertex and in the center. Uranium metaland in the center. Uranium metal

Binary CompoundBasic Format

Unit Cells, 3Unit Cells, 3

Face centered cubic: at each vertex Face centered cubic: at each vertex and in the center of each face. Also and in the center of each face. Also called Cubic Closest Packing called Cubic Closest Packing structure because each new layer of structure because each new layer of atoms nests into the holes from the atoms nests into the holes from the layer below.layer below.

Basic Format Binary Compound

Unit Cells, 4Unit Cells, 4

Hexagonal Close Packed: each Hexagonal Close Packed: each atom in the second layer lays in a atom in the second layer lays in a dimple between the atoms in the dimple between the atoms in the sandwiching layers.sandwiching layers.

Binary CompoundBasic Format

Section 10.5 Atomic Section 10.5 Atomic SolidsSolids

Carbon as diamondCarbon as diamond Physical PropertiesPhysical Properties

StructureStructure

BondingBonding

Carbon as graphiteCarbon as graphite Physical PropertiesPhysical Properties

StructureStructure

BondingBonding

Section 10.6 Molecular Section 10.6 Molecular SolidsSolids

Covalent bond length within molecule Covalent bond length within molecule is shorter than the distance between is shorter than the distance between attracted molecules.attracted molecules.

Low melting points, relatively weak Low melting points, relatively weak IMF’sIMF’s

Examples of molecules that form Examples of molecules that form Molecular Solids:Molecular Solids:

WaterWater Carbon DioxideCarbon Dioxide Any other covalently bonded moleculeAny other covalently bonded molecule

Section 10.7 Ionic SolidsSection 10.7 Ionic Solids

The large ions define the shape of the The large ions define the shape of the crystal lattice. Smaller ions fit in the holes crystal lattice. Smaller ions fit in the holes between the larger ions.between the larger ions.

StableStable High Melting PointHigh Melting Point Strong Intermolecular Forces (because ions Strong Intermolecular Forces (because ions

have good dipole moments!)have good dipole moments!) Examples of things that form ionic solids:Examples of things that form ionic solids:

NaClNaCl CsClCsCl Any other ionic compoudAny other ionic compoud