thermo and vap

vapor pressure

a liquid substance in equilibrium with its gaseous form

boiling point

temperature at which Pvap = atmospheric pressure

boiling point is lower at ? pressure?

lower

fusion

solid to liquid, positive

vaporization

liquid to gas, positive

sublimation

solid to gas, positive

way to remember positive phase changes

"FVS" = frogs visit swamps

freezing

liquid to solid, negative

condensation

gas to liquid, negative

deposition

gas to solid, negative

way to remember negative phase changes

"FCD" = freezing cold dance

clausius - clapyeron equation example off slides: ethanol has vapor pressure of P1 = 100.0 torr at T1 = 34.7 °C and ∆Hvap = 38.6 kJ/mol. What is its vapor pressure at T2 = 65.0 °C?

360 torr

clausius - clapeyron equation example off slides: water boils at T1 = 100.0 °C at atmospheric pressure (P1 = 760 torr). At the top of Pike's Peak in Colorado, where the air pressure is only P2 = 407 torr, what is the boiling point T2? Water has ∆Hvap = 40.7 kJ/mol.

83.0 C

ln Pvap vs. 1/T for a liquid is equal to ?

-Hvap/R

phase change signs for fusion, vaporization, and sublimation

H > 0, S > 0

phase change signs for freezing, condensation, deposition

H < 0, S < 0

ΔG

gibbs free energy

spontaneous process

ΔG > 0 (can only act spontaneous underground)

non spontaneous reaction

ΔG < 0

equilibrium process

ΔG = 0

phase transition calculation equation for S

"SEHDT"

phase transition calculation equation for H

"HETTS"

phase transition calculation equation for T

"TEHDS"

phase transition calculation equation example off slides: Water has Tvap = 100 °C = 373.15 K and ∆Hvap = 40.67 kJ/mol = 4.067 × 104 J/mol. What is ∆Svap?

109.0 J/(k x mol)

step 1 of heating curves

heating ice to its melting point

step 2 of heating curves

melting the ice

step 3 of heating curves

heating the liquid water to its boiling point

step 4 of heating curves

boiling the water

step 5 of heating curves

heating the steam

heat capacity of ice

36

heat capacity of liquid

75

heat capacity of steam

33

triple point

all three phases in equilibrium

critical point

a supercritical fluid with no liquid / gas distinction

negative slope on phase diagram

means melting point is decreasing function of pressure

crystalline solids

long range order of arrangement for atoms / molecules / ions "crystal-long"

amorphous solids

particles randomly arranged, no long range order

ionic solids

regular arrangement of alternating cations and anions, held together by ionic bonds

molecular solids

regular arrangement of individual molecules, held together by intermolecular forces

network covalent solids

atoms held together by covalent bonds throughout the crystal

x-ray crystallography

technique for determining the arrangement of atoms in a crystal by diffraction of x-rays

unit cell

smallest repeating unit of a cell

simple cubic

1 atom in 8 corners of a cube, so (8)(1/8)= 1, 50% of volume taken, coordination number = 6

body centered cubic

1 atom in 8 corners of a cube + 1 in the center, so 1 + (8)(1/8)= 2, 68% of volume taken, coordination number = 8

face centered cubic (aka cubic closest)

• 1 atom in 8 corners of a cube + 1 on each of the 6 faces, so (8)(1/8) + (6)(1/2) = 4, coordination number = 12, smaller volume

atom in the center

contributes one whole atom

atom in one of the faces

contributes 1/2 of an atom

atom on an edge

contributes 1/4 of an atom

atom on a corner

contributes 1/8 of an atom

graphite

one allotrope of carbon, sheets of repeating hexagons of sp2-hybridized C atoms

diamond

3D network of repeating tetrahedron

fullerene

molecular solid allotropes, and carbon "nanotubes" can be made

how does metallic bonding differ from covalent bonding?

metallic bonding doesn't satisfy the octet rule because there aren't enough electrons to go around. Instead of localized bonds, metals use a "sea of delocalized electrons" to glue the atoms together.

electron sea

metals are cations sharing a wholly delocalized "sea" of valence electrons, no electron belongs to any given metal atom (or pair of atoms)

electron-sea model accounts for

metals being malleable (able to be hammered) and ductile (able to be drawn into wires). electrons in the "sea" are highly mobile: move away from negative electrode, towards positive one, accounts for high electrical conductivity

semiconductor

a substance that can conduct electricity under some conditions, generally made from semimetals (metalloids)

diodes

allow electric current to flow readily in one direction, but not in another, accomplished by connecting p-type and n-type doped semiconductors at a "p-n junction"

electrical conductivity of a semiconductor increases with what?

increasing temperature, while the reverse is true of a metal

superconductor

materials with R = 0, so no resistance to current flow under applied potential. critical temperature Tc is the temperature below which a superconductor has zero electrical resistance

high temperature superconductors currently know still have what?

critical temperatures that are quite cold

3-5 semiconductors

one element has 3 valence electrons, the other has 5