states of matter. liquid gas solid what causes the differences in solids, liquids, and gases?
TRANSCRIPT
States of Matter
States of MatterStates of Matter
LiquidGas
Solid
What causes the differences in solids, liquids, and gases?
What causes the differences in solids, liquids, and gases?
Kinetic Molecular TheoryKinetic Molecular Theory
Describes behavior of matter in terms of particles in motion.
Makes assumptions of gas particles:• separated by empty space
• particles are not attracted to each other• are in constant, random motion• collisions are elastic• kinetic energy determined by mass & velocity
KE = ½ mv2
C. Johannesson
Liquids & SolidsLiquids & SolidsLiquids & SolidsLiquids & Solids
I. Intermolecular Forces(between molecules)
(Ch. 6, p.189-193)
C. Johannesson
A. Definition of Intermolecular Forces
A. Definition of Intermolecular Forces
Attractive forces between molecules.
Much weaker than chemical bonds within molecules.
a.k.a. van der Waals forces
Intermolecular ForcesIntermolecular Forces
Attraction between
molecules
C. Johannesson
B. Types of IMFB. Types of IMF
C. Johannesson
B. Types of IMFB. Types of IMF
London Dispersion Forces
View animation online.
DispersionDispersion
Weak forces caused from temporary shifts in e- density
Polarity (Differing Electronegativities)
Polarity (Differing Electronegativities)
Eletronegativity Difference Bond Character
> 1.7 ionic
0.4 – 1.7 polar covalent
< 0.4 Nonpolar covalent
C. Johannesson
B. Types of IMFB. Types of IMF
Dipole-Dipole Forces
+ -
View animation online.
Dipole-DipoleDipole-Dipole
Between partial positive area of one molecule with the partial negative area of another
Occurs in polar molecules
C. Johannesson
B. Types of IMFB. Types of IMF
Hydrogen Bonding
Hydrogen BondingHydrogen Bonding
Special dipole-dipole Between H and a highly
electronegative atom (O, N, F) SPECIAL NOTE – THE H atom has to be
directly chemically bonded to an O, N, or F
Your DNAYour DNA
C. Johannesson
C. Determining IMFC. Determining IMF
CH2Cl2• polar = dispersion, dipole-dipole
CH4
• nonpolar = dispersionHF
• H-F bond = dispersion, dipole-dipole, hydrogen bonding
C. Johannesson
II. Physical PropertiesA. Liquids vs. Solids
II. Physical PropertiesA. Liquids vs. Solids
LIQUIDS
Stronger than in gases
Y
high
N
slower than in gases
SOLIDS
Very strong
N
high
N
extremely slow
IMF Strength
Fluid
Density
Compressible
Diffusion
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B. Liquid PropertiesB. Liquid Properties
Surface Tension• attractive force between particles in a
liquid that minimizes surface area
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B. Liquid PropertiesB. Liquid Properties
Capillary Action• attractive force between the surface of
a liquid and the surface of a solid
water mercury
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C. Types of SolidsC. Types of Solids
Crystalline - repeating geometric pattern• covalent network• metallic• ionic• covalent molecular
Amorphous - no geometric pattern
decreasingm.p.
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C. Types of SolidsC. Types of Solids
Ionic(NaCl)
Metallic
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C. Types of SolidsC. Types of Solids
CovalentMolecular
(H2O)
CovalentNetwork
(SiO2 - quartz)
Amorphous(SiO2 - glass)
C. Johannesson
III. Changes of StateA. Phase Changes
III. Changes of StateA. Phase Changes
C. Johannesson
A. Phase ChangesA. Phase Changes
EvaporationEvaporation• molecules at the surface gain enough
energy to overcome IMF
VolatilityVolatility• measure of evaporation rate• depends on temp & IMF
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A. Phase ChangesA. Phase Changes
Kinetic Energy
# o
f P
art
icle
s
p. 477
Boltzmann Distribution
temp
volatility
IMF
volatility
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A. Phase ChangesA. Phase Changes
EquilibriumEquilibrium• trapped molecules reach a balance
between evaporation & condensation
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A. Phase ChangesA. Phase Changes
Vapor PressureVapor Pressure• pressure of vapor above
a liquid at equilibrium
IMF v.p.temp v.p.
• depends on temp & IMF• directly related to volatility
p.478
temp
v.p
.
C. Johannesson
A. Phase ChangesA. Phase Changes
Boiling Point• temp at which v.p. of liquid
equals external pressure
IMF b.p.Patm b.p.
• depends on Patm & IMF
• Normal B.P. - b.p. at 1 atm
C. Johannesson
Which has a higher m.p.?• polar or nonpolar?• covalent or ionic?
A. Phase ChangesA. Phase Changes
Melting Point• equal to freezing point
polar
ionic
IMF m.p.
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A. Phase ChangesA. Phase Changes
Sublimation
• solid gas
• v.p. of solid equals external pressure
EX: dry ice, mothballs, solid air fresheners
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B. Heating CurvesB. Heating Curves
Melting - PE
Solid - KE
Liquid - KE
Boiling - PE
Gas - KE
C. Johannesson
B. Heating CurvesB. Heating Curves
Temperature Change• change in KE (molecular motion) • depends on heat capacity
Heat Capacity• energy required to raise the temp of 1
gram of a substance by 1°C• “Volcano” clip - water has a very high
heat capacity
C. Johannesson
B. Heating CurvesB. Heating Curves
Phase Change• change in PE (molecular arrangement)• temp remains constant
Heat of Fusion (Hfus)
• energy required to melt 1 gram of a substance at its m.p.
C. Johannesson
B. Heating CurvesB. Heating Curves
Heat of Vaporization (Hvap)
• energy required to boil 1 gram of a substance at its b.p.
• usually larger than Hfus…why?
EX: sweating, steam burns, the drinking bird
C. Johannesson
C. Phase DiagramsC. Phase Diagrams
Show the phases of a substance at different temps and pressures.
Phase DiagramsPhase Diagrams
Triple point - The temperature and pressure at which the solid, liquid, and vapor phases of a pure substance can coexist in equilibrium.
*Be able to know what phase change occurs when pressure and/or temperature changes when looking a phase diagram.
C. Johannesson