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Ch. 13: Liquids & Solids. Meniscus: the curved surface of a liquid in a container (A could be water and B could be mercury) – see below. Adhesion vs. Cohesion. Adhesion – the attraction of a substance for other substances (the walls of its container, possibly) - PowerPoint PPT Presentation
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Ch. 13: Liquids & Solids
Meniscus: the curved surface of a liquid in a container (A could be water and B could be mercury) – see below
Adhesion vs. Cohesion
Adhesion – the attraction of a substance for other substances (the walls of its container, possibly)
Cohesion – the attraction of a substance for itself
Properties of liquids• Capillary action.Capillary action.
MercuryCohesive is largerthan adhesive.
WaterAdhesive is largerthan cohesive.
Capillary tube
meniscus
• ViscosityViscosity• Resistance to flow.
• This increases with increased intermolecular attractions.
• Also, liquids composed of long, flexible molecules can entwine, resulting in increased viscosity - motor oil.
Properties of liquids
CH3CH2CH2
OH
CH3CH CH2
OHOH
CH2CH CH2
OHOHOH
Increasing viscosity
Properties of liquids
• Surface TensionSurface Tension• Force in the surface of a liquid that makes the area
of the surface as small as possible.
Molecules at thesurface interactonly with neighborsinside the liquid.
Molecules at thesurface interactonly with neighborsinside the liquid.
Properties of liquids• VaporizationVaporization• The formation of a gas from a liquid.
• At any temperature, at least a few of the molecules in the liquid are moving fast enough to escape.
initially equilibrium
after sometime
molecules leave andRe-enter liquid at
the same rate
molecules leave andRe-enter liquid at
the same rate
Equilibrium• A state where the forward and reverse
conditions occur at the same rate.
DynamicEquilibrium
I’m in staticequilibrium.
Vapor Pressure and boiling point
• Equilibrium vapor pressureEquilibrium vapor pressure• The pressure of a vapor in equilibrium with
a liquid.• It depends on:It depends on:• the intermolecular forces in the liquid.• temperature.• It is independent of:It is independent of:• the volume of the liquid or vapor• the surface area of the liquid
Boiling Points
• Boiling pointBoiling point - temperature where the vapor pressure equals atmospheric pressure.
Boiling point of water at various elevations
City Elevation BP (oC) San Francisco Sea level 100.0 Salt Lake City 4,390 95.6 Denver 5,280 95.0 La Paz, Bolivia 12,795 91.4 Mount Everest 20,028 76.5
Boiling point of water at various elevations
City Elevation BP (oC) San Francisco Sea level 100.0 Salt Lake City 4,390 95.6 Denver 5,280 95.0 La Paz, Bolivia 12,795 91.4 Mount Everest 20,028 76.5
This is the reason that cake mixes includehigh altitude baking instructions.
Heating Curve
Phase Diagramssupercriticalfluid regionsupercriticalfluid region
TcTc
solidsolidliquidliquid
gasgas
PcPc
temperaturetemperature
pre
ssu
rep
ress
ure Critical
pointCriticalpoint
Phase Diagram of H2O
Phase Diagram of CO2
Boltzmann Curve
• As the temperature is increased, a higher fraction of molecules will have a kinetic energy that is greater than the energy needed for a phase change.
T1 < T2 < T3
T1 < T2 < T3
Kinetic energy
Fract
ion o
f m
ole
cule
sH
avin
g k
ineti
c energ
y
T3
T2
T1Ea
Allotropes of Carbons
• Allotrope: different forms of the same element
• Repeating units of covalently bonded carbon atoms.
GraphiteGraphite
Networks of Carbon
Diamond Buckminster Fullerene
www.answers.com
Carbon Nanotube