Hydrogen BondingHydrogen Bonding

• Interaction btwn eInteraction btwn e---rich atom -rich atom connected to H entity & another H connected to H entity & another H attached to eattached to e——rich atomrich atom

• ee---rich atom = O, F, N-rich atom = O, F, N

• Gives water > density than Gives water > density than iceice– Ice floatsIce floats

• Higher heat capacityHigher heat capacity

Hydrogen BondingHydrogen Bonding

• Unique propertiesUnique properties

• B.p. of HB.p. of H22O, HF, and NHO, HF, and NH33 muchmuch higherhigher

Boiling PointBoiling Point

• Bp Bp temp. at which vapor pressure temp. at which vapor pressure = external (atmospheric pressure)= external (atmospheric pressure)

• At higher elevations atmospheric At higher elevations atmospheric pressure is lower pressure is lower water boils less water boils less than 100 than 100 °C°C

Surface TensionSurface Tension

• Outer molecules interact with surface, Outer molecules interact with surface, while inner interact with other moleculeswhile inner interact with other molecules

• It has a “skin”It has a “skin”• Skin toughness = Skin toughness = surface tensionsurface tension• E required to break through surfaceE required to break through surface• Smaller surface area reason that water Smaller surface area reason that water

drops sphericaldrops spherical• http://http://

www.ilpi.com/genchem/demo/tension/#dewww.ilpi.com/genchem/demo/tension/#demomo

Capillary ActionCapillary Action

• When water goes up a small glass tubeWhen water goes up a small glass tube

• Due to polarity of Si-O bonding with waterDue to polarity of Si-O bonding with water

• Adhesive forces Adhesive forces > cohesive forces of water> cohesive forces of water

• Creates a chain or bridgeCreates a chain or bridge

• Pulls water up tubePulls water up tube

• Limited by balancing gravity with Limited by balancing gravity with adhesive/cohesive forcesadhesive/cohesive forces

• Thus, water has a concave Thus, water has a concave meniscusmeniscus

MercuryMercury

• Forms a convex meniscusForms a convex meniscus

• Doesn’t “climb” a glass tubeDoesn’t “climb” a glass tube

• Due to cohesive forces Due to cohesive forces > adhesive > adhesive forcesforces

ViscosityViscosity

• Hydrogen-bonding increases viscosityHydrogen-bonding increases viscosity

• But large non-polar liquids like oil But large non-polar liquids like oil have:have:

• 1) large unwieldy molecules w/greater 1) large unwieldy molecules w/greater intermolecular forcesintermolecular forces

• 2) greater ability to be entangled 2) greater ability to be entangled w/one anotherw/one another

SublimationSublimation

• Going from solid to gas Going from solid to gas without going through without going through the liquid statethe liquid state

• Enthalpy of sublimation Enthalpy of sublimation = = HHsublimationsublimation

• Iodine, dry ice (solid Iodine, dry ice (solid COCO22) & ice sublimate) & ice sublimate

• Frost on grass on a cold Frost on grass on a cold morning sublimatesmorning sublimates

PolymersPolymers

• Huge molecules with repeating Huge molecules with repeating monomers (subunits)monomers (subunits)

• Thermoplastics (polyethylene): Thermoplastics (polyethylene): respond to heatingrespond to heating

• Soften and flow when heated, harden Soften and flow when heated, harden when cooledwhen cooled

• Thermosetting plastics (Formica): Thermosetting plastics (Formica): initially soft, but solid when heated; initially soft, but solid when heated; irreversibleirreversible

Disturbing chemical Disturbing chemical equilibriaequilibria

• Le Chatelier’s PrincipleLe Chatelier’s Principle

• Change one component of the rxn,Change one component of the rxn,

• The rxn will attempt to rectify itThe rxn will attempt to rectify it

• (rectify is not a bad word)(rectify is not a bad word)

• Think of it this way:Think of it this way:

• If something is changed, how can it If something is changed, how can it be undone or controlled?be undone or controlled?

Temperature variation on Temperature variation on equilibriumequilibrium

• 2NO2NO2(g)2(g) N N22OO4(g) 4(g) + heat+ heat

• Exothermic Exothermic heat out heat out

• Raise the temp to 298 K Raise the temp to 298 K will want to will want to get rid of excess heat get rid of excess heat will swing to will swing to left left producing more NO producing more NO2 2

(endothermic)(endothermic)

• Sooner or later, equilibrium re-Sooner or later, equilibrium re-establishedestablished

Pressure & volume change on Pressure & volume change on equilibriumequilibrium

• If volume decreased (pressure increased) If volume decreased (pressure increased) favors smaller # of molecules favors smaller # of molecules

• If volume increased (pressure decreased) If volume increased (pressure decreased) favors larger # of molecules favors larger # of molecules

• If reversible rxn has = # of molecules on If reversible rxn has = # of molecules on each side, a volume/pressure change will each side, a volume/pressure change will do nothingdo nothing