INTERMOLECULAR FORCES OF ATTRACTION

Outside and weak

attraction

Physical properties

Physicalstates

Boiling point

compounds

Partial charges

Fartherdistance

solubility

are

between

explains

KIND OF IMFA COMPOUNDS THAT FORMED THEM

electrostatic Ionic & ionic

Ion dipole Ionic & polar

H bondPolar H terminal & lone pair of smallElectronegative atom

Dipole dipole Polar & polar

Ion induced dipole Ionic & non polar

Dipole induced diipole Polar & non polar

dispersion Non polar & non polar

Decreasingstrenght

electrostaticIonic with ionic

NaCl NaCl

electrostatic

Ion dipole Ion with polar

Na+ H2O

ion dipole

H bondPolar H terminal with lone pairs of small electronegative atoms

H2O H2O

H- bond

Dipole-dipole Polar with polar

CH3 C = OCH3

CH3

CH3 C=O dipole-dipole

Ion-induced dipole Ion with non polar

O = O Na+

ion induced dipole

O = O Cl-

e' movement

e' movement

Dipole induced diploe Dipole with non polar O = O H2O

dipole induced dipole

Dispersion Non polar with non polar

O = O O = O

dispersion

IMFA and Solubility1. Dissolved substance

(solute) must separate (IMFA breaking- endothermic heat)

2. Dissolving substance (solvent) must separate (IMFA breaking-endothermic heat)

3. Solute and solvent must mix (IMFA forming-exothermic heat)

For dissolving to happen, 3 processes must occur

IMFA between solute and solvent > IMFA among solute and or IMFA among solvent

_

• Summarized as : LIKE DISSOLVES LIKE ;

• polar solvent dissolves polar solute• Non polar solvent dissolves non polar solute

IMFA and Physical State

PHYSICAL STATE

IMFA KINETIC ENERGY

MOLECULES TOGETHER MOLECULES APART

Interplay between

drawsseparates

KindsSolid

IMFA>>>

KE

Gas IMFA<<<

KE

liquid IMFA is continuously being formed and continuously being broken

PHYSICAL STATES

Solid

Gas

Liquid

IMFA >>> KE

KE >>> IMFA

IMFA is continously being formedAnd continously being broken

Phase Changes are

MELTING FREEZINGEVAPORATION CONDENSATION

S to L L to SG to LL to G

Temp > IMFA Temp >>> IMFA Temp < IMFA Temp <<<IMFA

ENDO EXO

Sorrounding cold

Sorrounding Warm

IS IS IS IS

WHENWHEN WHEN WHEN

makes makes

is is

ENERGY CURVE DURING PHASE CHANGE (OF WATER)

TEMP

ENERGY

-4

0

s

l

l - g

s - l

g

80 cal/g

540 cal/g

100

25

Heat of Fusion- amount of energy needed to melt 1 gram of a substance at its melting point

H fusion water = 80 cal/g

Q= mass X H fusion

Heat of Vaporization – amount of energy needed to evaporate 1 gram of a substance at its boiling point

H vap water = 540 cal/g

Q = mass X H vap

Heat of Freezing = energy released to change 1 gram of liquid to solid

Heat of Condensation= energy released to convert 1 gram of gas to liquid

SPECIFIC HEATS

Energy involved to change the temperature of 1 gram of a substance, 10Celsius

LATENT HEATS

• Heat of Fusion- amount of energy needed to melt 1 gram of a substance at its melting point

• H fusion water = 80 cal/g

• Q= mass X H fusion

LATENT HEATS

• Heat of Freezing = energy released to change 1 gram of liquid to solid

•• Heat of Fusion (endo) = Heat of Freezing (exo)

LATENT HEATS

• Heat of Vaporization – amount of energy needed to evaporate 1 gram of a substance at its boiling point

• H vap water = 540 cal/g

• Q = mass X H vap

LATENT HEATS

• Heat of Condensation= energy released to convert 1 gram of gas to liquid

• • Heat of Vaporization (endo) = Heat of

Condensation(exo)

SPECIFIC HEATS

• Energy involved to change the temperature of 1 gram of a substance, 10Celsius

• For water: Sp. Heat = 1 cal/g-0C

UNIQUE PROPERTIES OF LIQUIDS

1. Surface Tension2. Capillarity3. Viscosity•

IMFA & Boiling PointBecause of the KE energy of evaporating liquids, they break their IMFA and result in some of them going into the gaseous state

and exert a pressure called vapor pressure.

Under a given temperature each liquid has its own vapor pressure.

When the vapor pressure of escaping liquid molecules become equal to the pressure of the air above it. The temperature at that point is called the boiling point of the liquid.

The stronger the IMFA, the harder to break, the longer time the liquid to evaporate the higher the boiling point

Vapor pressure

Air pressure

• Vapor pressure = air pressure : Boiling point

IMFA & Boiling Point

• IMFA increases, boiling point increases

• MWt increases, IMFA increases, boiling point increases

• Branching increases, IMFA decreases, boiling point decreases