Liquids and SolidsLiquids and Solids

KMT of Liquids and Solids, KMT of Liquids and Solids, Phase Diagram, Phase Diagram,

Vapor Pressure Curve, Vapor Pressure Curve, Heating/Cooling CurveHeating/Cooling Curve

Intermolecular Forces: Liquids, Solids, and Phase

Changes

1.Types of Intermolecular Forces

2.Properties of liquids and solids

3.Phase change diagrams

4.Heating/cooling curve

5.Vapor pressure curve

Brainteaser!!!! Brainteaser!!!!

If substances at the same If substances at the same temperature have the same temperature have the same

kinetic energy, why are they all kinetic energy, why are they all not liquids, solids, or gases?not liquids, solids, or gases?

Intermolecular ForcesIntermolecular Forces InterIntermolecular Forces are attractive forces molecular Forces are attractive forces betweenbetween

molecules. Think interstate!molecules. Think interstate! IntraIntramolecular Forces are attractive forces that hold molecular Forces are attractive forces that hold

molecules togethermolecules together

Inter vs. IntraInter vs. Intra 41 kJ to vaporize 1 mole of H41 kJ to vaporize 1 mole of H22OO

930 kJ to break all O-H bonds in one H930 kJ to break all O-H bonds in one H22O moleculeO molecule

Which one is stronger?????

Intramolecular forces are stronger than intermolecular forces!!!!

Dipole – Dipole ForcesDipole – Dipole Forces

Between polar molecules

What bond is the strongest? Where is the intermolecular bond?

Dipole – molecule with a completely separate positively and negatively charged end

Ion – Dipole ForcesIon – Dipole Forces Between polar molecules and ionsBetween polar molecules and ions

Give me an example of an everyday solution between polar molecules and ions!!!!!!

Why are dipoles attracted to ions?

London-Dispersion ForcesLondon-Dispersion Forces Intermolecular forces are formed by Intermolecular forces are formed by temporarilytemporarily

induced dipole momentsinduced dipole moments

How do dipoles become induced?

Electron clouds constantly move and when one

molecule collides with another molecule the

electrons are temporarily shifted to one side

This creates a momentary negative end and a positive

end

Usually occurs between identical molecules (Example

H2 (g)

Hydrogen bondsHydrogen bonds Force formed between molecules Force formed between molecules

containing N–H, O–H, or F–H groups, containing N–H, O–H, or F–H groups, and an electronegative O, N, or F atom.and an electronegative O, N, or F atom.

10% of the energy in a covalent bond!!!!!!

Hydrogen BondingHydrogen Bonding

H2O CH3OH NH3

Phases of matterPhases of matter Gases – molecules are widely separated and the Gases – molecules are widely separated and the

“fluid” is compressible“fluid” is compressible Liquids – molecules are more tightly packed and Liquids – molecules are more tightly packed and

liquids are relatively incompressibleliquids are relatively incompressible Solids – molecules are tightly packed and solids Solids – molecules are tightly packed and solids

are incompressible and rigidare incompressible and rigid

LiquidsLiquids IMF’s limit the range of motion of particles IMF’s limit the range of motion of particles

in a liquidin a liquid

Density – Liquids have a higher density at 25 °C than gases

Fluidity – Ability to flow

Viscosity – Measure of the resistance of a liquid to flow

Surface tension – The energy required to increase the surface area of a liquid by a given amount

ViscosityViscosity Measure of a liquids Measure of a liquids

resistance to flowresistance to flow Inversely related to the size Inversely related to the size

of the molecule and the type of the molecule and the type and strength of and strength of intermolecular forcesintermolecular forces

The higher the temperature The higher the temperature the lower the viscositythe lower the viscosity

If temperature then viscosity

Here’s the tricky part:

If temperature then the liquid starts to flow

Surface TensionSurface Tension

The energy required to increase the The energy required to increase the surface area of a liquid by a given amountsurface area of a liquid by a given amount

Molecules in the center of a liquid are exposed to IMF from all sides Molecules on the surface of a liquid are not exposed to IMF from all sides In order to increase the surface area of a liquid the molecules in the interior of the liquid must move to the surface and the IMF’s must be broken

Capillary ActionCapillary Action Water molecules “cling” to the Water molecules “cling” to the

surface of the graduated cylinder by surface of the graduated cylinder by adhesionadhesion

Adhesion is the force of attraction Adhesion is the force of attraction between different types of moleculesbetween different types of molecules

Cohesion is the force of attraction Cohesion is the force of attraction between the same type of moleculesbetween the same type of molecules

What force must be strongest for What force must be strongest for water to cling to the glass tube?water to cling to the glass tube?

If adhesion forces are stronger than If adhesion forces are stronger than cohesion forces water will be drawn cohesion forces water will be drawn up the sides of the cylinderup the sides of the cylinder

SolidsSolids Tightly packed molecules that Tightly packed molecules that

are rigid and cannot be are rigid and cannot be compressedcompressed

Density is highest in solids Density is highest in solids (except in water!!!)(except in water!!!)

Crystalline solid – solid Crystalline solid – solid whose atoms, ions, or whose atoms, ions, or molecules are arranged in an molecules are arranged in an orderly, geometric, 3-D orderly, geometric, 3-D structurestructure

Amorphous – atoms are Amorphous – atoms are randomly arranged because randomly arranged because they typically cool too quickly. they typically cool too quickly.

No order exists in the solid. No order exists in the solid.

Types of SolidsTypes of Solids

Crystalline – a well defined arrangement of Crystalline – a well defined arrangement of atoms; this arrangement is often seen on a atoms; this arrangement is often seen on a macroscopic level. (p.402)macroscopic level. (p.402)• Atomic solids Atomic solids • Ionic solidsIonic solids • Molecular solidMolecular solid • Covalent networkCovalent network • MetallicMetallic

Units points that can be repeated in three Units points that can be repeated in three dimensions to form a latticedimensions to form a lattice

Phase ChangesPhase Changes

Melting – the change from a Melting – the change from a solid to a liquidsolid to a liquid

Melting Point – T at which Melting Point – T at which forces holding lattice together forces holding lattice together are brokenare broken

Vaporization- the change from Vaporization- the change from a liquid to a gas a liquid to a gas

Sublimation – the change from Sublimation – the change from a solid to a gasa solid to a gas

Condensation – the change Condensation – the change from a gas to a liquidfrom a gas to a liquid

Deposition – the change from Deposition – the change from a gas to a solida gas to a solid

Freezing – the change from a Freezing – the change from a liquid to a solidliquid to a solid

GAS

SOLID LIQUID

MELTING

FREEZING

CO

ND

EN

SA

TION

VA

PO

RIZA

TION

SU

BLI

MA

TIO

ND

EP

OS

ITIO

N

Phase Change DiagramsPhase Change Diagrams

Relationship between T and PRelationship between T and P Triple point – P and T at which substance can coexists as a gas, Triple point – P and T at which substance can coexists as a gas,

liquid, and solidliquid, and solid Critical point – T at which a substance can no longer remain a liquid Critical point – T at which a substance can no longer remain a liquid

regardless of the pressureregardless of the pressure

Look at the liquid solid line and its

slope!!!!!

Phase Diagram for HPhase Diagram for H22OO

What is the difference between this diagram What is the difference between this diagram and the first?and the first?

The liquid solid line leans backwards! The liquid solid line leans backwards!

Normal Melting and

boiling points

Vapor pressure

curve

Vapor PressureVapor Pressure In a sealed container some water (In a sealed container some water (ll) changes ) changes

phase to become water vapor and exerts a phase to become water vapor and exerts a pressure over the surface of the liquid (if the pressure over the surface of the liquid (if the container were open it would be considered container were open it would be considered partial pressure)partial pressure)

Heating Cooling CurveHeating Cooling Curve

120 °C120 °C

steamsteam 100 °C 100 °C water water steam steam

50°C50°C liquid water liquid water

0 °C ice0 °C ice liquid liquid -10 °C ice-10 °C ice Heat added Heat added

Why does temperature “stand still”?

Heating and cooling curve for HHeating and cooling curve for H22OOWhat bonds are broken?