Chapter 11 Flashcards
intermolecular forces
hold any 2 molecules together; weaker than intramolecular forces
intramolecular forces
hold 2 same atoms together
- covalent, ionic, metallic
↑ boiling/melting point = ___IMF
↑ IMF
↑ surface tension = ___IMF
↑ IMF
↑ viscosity = ___ IMF
↑ IMF
↑ capillary action = ___ IMF
↑ IMF
↑ volatility = ___ IMF
↓ IMF
↑ vapor pressure (ideal gas law) = ___ IMF
↓ IMF
Viscosity
resistance of a liquid to flow
Surface tension
surface of water behaves like elastic
Cohesive forces
forces bind similar molecules
- ex: hydrogen bonding in water
Adhesive forces
forces bind substance to surface
Capillary action
rise of liquids up very narrow tubes
Thermodynamically favored phase
least costly phase for 1 material
metastable phase
less costly phase, but less stable
Phase change
change of state of pure substance by heating or cooling
solid –> liquid
melting (fusion)
liquid –> gas
vaporization
gas –> solid
deposition
solid –> gas
sublimination
Heat (Enthalpy) of fusion
↑ freedom of motion of particles requires energy
- ex: boiling water
Maxwell Distribution
velocities of molecules in vapor phase @ given temp are diff
- relates temp to particles and velocity
- bell curve
Phase Diagram
summarizes conditions under equilibria b/w diff states of matter
Critical point
at/above only 1 gas-like phase exists
- no surface tension
Triple point
all 3 phases coexist in equilibrium:
- all 3 curves intersect
- doesn’t matter what phase
Permanent gases
substance w/ critical point ↓ than room temp
- Helium, hydrogen, nitrogen, argon, oxygen
Clausius Clapeyron Equation (constraint of coexistence): R =
8.314 J/molK = 8.34 x 10^-3 KJ/molK
Clausius Clapeyron Equation (constraint of coexistence): pressure =
1 atom = 101 kPa
Clausius Clapeyron Equation (constraint of coexistence): T =
temp in Kelvin
4 main classes of materials (compounds):
ionic compounds, metals, network covalent, molecular
ionic compounds
Electrostatic attraction b/w cation and anion:
- ability to form crystals
- ↑ enthalpies of fusion/vaporization
- ↑ melting/boiling points
- hard
- conduct electricity
- stronger than covalent bonds
metals
Collectively share valence e-:
- ↑ melting/boiling points
- shiny
- hard
- good heat conductors
network covalent
- Compound w/ atoms bonded by covalent bonds in a continuous network
- weak interactions
- covalent bonds extend throughout large region; many repeating units
- crystals; often oxides or sulfides
- = rate A common: Si, SiC, SiO2 (quartz), C (diamond), C (graphite), BN, Ge
molecular
- Doesn’t conduct electricity
- insoluble in water (soluble in nonpolar solvents)
- smelly (volatile)
- ↓ melting/boiling points
Dispersion force
instantaneous dipole on one atom causes atoms to be attracted
- all interactions b/w dipole forces
- ALL molecules have dispersion forces
↑ molar mass =
↑ dispersion force = ↑ boiling point
dispersion force: D(t) =
q(t) *R
- R = distance/length of molecule
-larger molecule = stronger force
Dipole force
polar molecules with +/- ends
Dipole-dipole interactions
presence of permanent dipole moment in a polar molecule
Ion-dipole force
b/w ion and polar molecule
- cation (+) attracted to (-) end of dipole
- anion (-) attracted to (+) end of dipole
critical temp
highest temp a liquid phase can form
critical pressure
pressure required to liquify at critical temp
- ↑ intermolecular forces = ↑ critical temp of substance
Vapor pressure
pressure of vapor attains constant value
most ionic (most polar)
atoms in molecule further apart on PT = more ionic
Hydrogen bonds…
increase boiling point
Hydrogen bonds…
increase boiling point
↑ heat of fusion (enthalpy to melt) = ___ IMF
↑ IMF
boiling point: polar molecule ___ nonpolar molecule
> > >
hydrogen bonding:
bond b/w X-H:
- X = N, O, F
- R-X-H:———:X-H
hydrogen bonding attractive forces
all 3: dispersion, dipolar (dipole-dipole), hydrogen bonding
H bond affects boiling point how?
↑ attraction (bc of all 3 forces) = ↑ boiling point
if an atom has at least 1 hydrogen bond it must…
have all 3 attractive forces (dispersion, dipolar, hydrogen bonding)
forces by molecule: nonpolar molecules
dispersion forces
forces by molecule: polar molecules
dispersion forces + dipole/dipole = ↑ boiling p.
forces by molecule: hydrogen bonding in molecule
dispersion forces + dipole/dipole + hydrogen bonding
What elements form a hydrogen bond w/ H?
N, O, F
how does a hydrogen bond impact boiling point?
increases
nonpolar solvents…
will NOT dissolve in water
solvents with 5+ C’s…
will NOT dissolve in water
polar solvents…
WILL dissolve in water
hydrophilic molecules
- cation + anion
- charged ions
polar molecules
hydrophobic molecules
hydrocarbons and nonpolar molecules
Molecules w/ hydrophobic and hydrophilic parts:
- Still soluble; increased C = less soluble
- 5+ C = not soluble
↑ in carbon chains = ↓ in
in solubility in water