Chapter 11 Flashcards by Abby Kreisler

intermolecular forces

hold any 2 molecules together; weaker than intramolecular forces

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intramolecular forces

hold 2 same atoms together
- covalent, ionic, metallic

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↑ boiling/melting point = ___IMF

↑ IMF

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↑ surface tension = ___IMF

↑ IMF

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↑ viscosity = ___ IMF

↑ IMF

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↑ capillary action = ___ IMF

↑ IMF

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↑ volatility = ___ IMF

↓ IMF

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↑ vapor pressure (ideal gas law) = ___ IMF

↓ IMF

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Viscosity

resistance of a liquid to flow

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Surface tension

surface of water behaves like elastic

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Cohesive forces

forces bind similar molecules
- ex: hydrogen bonding in water

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Adhesive forces

forces bind substance to surface

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Capillary action

rise of liquids up very narrow tubes

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Thermodynamically favored phase

least costly phase for 1 material

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metastable phase

less costly phase, but less stable

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Phase change

change of state of pure substance by heating or cooling

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solid –> liquid

melting (fusion)

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liquid –> gas

vaporization

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gas –> solid

deposition

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solid –> gas

sublimination

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Heat (Enthalpy) of fusion

↑ freedom of motion of particles requires energy
- ex: boiling water

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Maxwell Distribution

velocities of molecules in vapor phase @ given temp are diff
- relates temp to particles and velocity
- bell curve

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Phase Diagram

summarizes conditions under equilibria b/w diff states of matter

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Critical point

at/above only 1 gas-like phase exists
- no surface tension

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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/mol*K = 8.34 x 10^-3 KJ/mol*K

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