Chapter 11: Liquids, Solids, and Intermolecular Forces Flashcards Preview

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Flashcards in Chapter 11: Liquids, Solids, and Intermolecular Forces Deck (31):
1

Coulomb's law

Potential energy (E) and distance (r) are inversely related

E decreases (becomes more negative) as r decreases

Potential energy and product of charges are directly related

E decreases as q1q2 decreases (becomes more negative)

*q1 and q2 are of opposite signs (charges)

2

Effect of intermolecular forces on boiling and melting points

High intermolecular forces = high boiling/melting point

3

Dispersion force

Result of fluctuations in the electron distribution within molecules or atoms

Depends on fleeting charge separation called instantaneous or temporary dipole

Stronger dispersion force:
Higher molar mass (polarizability)
More surface area (longer chains)

4

Instantaneous/temporary dipole

Associated with dispersion force

When an atom or molecule displays polarity temporarily (as electrons are constantly moving and bond to be dense on one end)

5

Permanent dipole

Characteristic of a polar molecule where positive and negative ends can interact with opposite ends of other like molecules

Associated with dipole-dipole force

6

Miscibility

Ability to mix without separting into two states

"Like dissolves like"

*Oil and water are immiscible

7

Hydrogen bond

Occurs when N, O, or F are bonded directly to a hydrogen

Special kind of dipole-dipole force where H has the partial positive charge and F, O, or N has the partial negative charge

8

Ion-dipole forces

Present only in mixtures of substances (ionic + polar)

9

Strengths of intermolecular forces

Dispersion < Dipole-dipole < H-bonding < Ion-dipole

10

Surface tension

Energy required to increase the surface area of a liquid by a unit amount

Molecules on surface are strongly attracted by interior molecules

Higher surface tension = greater intermolecular forces

Temperature increases --> surface tension decreases

11

Viscosity

Liquid's resistance to flow

Higher viscosity = stronger intermolecular forces

More spherical molecules = less viscous
(Chains are more viscous)

Temperature increases --> viscosity decreases

12

Capillary action

The ability of a liquid to flow ("climb" up a thin tube against influence of gravity

Depends on two forces:
Cohesion
Adhesion

The stronger the cohesion (intermolecular forces), the smaller the capillary action

13

Cohesive forces

Forces that hold liquid molecules together

14

Adhesive forces

Forces that attract the outer liquid molecules to tube's surface

15

Vaporization

AKA evaporation

Escape of molecules from liquid to gas phase - endothermic

Kinetic energies vary within liquid body

Molecules on surface have higher kinetic energies and more easily overcome intermolecular forces

Affected by:
Temperature
Surface area
Intermolecular forces (volatility)

16

Condensation

Molecules transition from gas to liquid phase - exothermic

Some molecules lose energy through collisions and liquid [re]captures them

17

Dynamic equilibrium

Occurs when two opposite processes reach the same rate so that there is no net gain or loss of material

Rate of evaporation = constant
Rate of condensation = increases until met with rate of evap

18

Vapor pressure

Pressure exerted by a vapor when it is in dynamic equilibrium with its liquid

Quantity & surface area = negligible

Vapor pressure increases with temperature and with decreasing strength of intermolecular forces

19

Heat (enthalpy of vaporation)

ΔHvap = -ΔHcondensation

The amount of heat energy required to vaporize one mole of a liquid

kJ/mol

Somewhat temperature dependent

20

Boiling point

Temperature at which vapor pressure of liquid is = to external pressure above liquid

21

Normal boiling point

Temperature at which the vapor pressure of a liquid equals 1 atm

22

The Clausius-Clapeyron Equation

ln P2/P1 = (-ΔHvap/R) (1/T2-T1)

R = 8.314 J/mol K

T = in Kelvin

23

Supercritical fluid

Properties are intermediate between a liquid and gas

Occurs at critical temperature and pressure

24

Sublimation

Phase transition solid to gas - endothermic

25

Deposition

Phase transition from gas to solid - exothermic

26

Fusion

AKA melting

Phase transition from solid to liquid - endothermic

27

Freezing

Phase transition from liquid to solid - exothermic

28

Heat (enthalpy) of fusion

ΔHfus = -ΔHcrystallization

Somewhat temperature dependent

The amount of heat energy required to melt one mole of a solid (kJ/mol)

29

Uniqueness of water

Liquid at room temperature (despite low molar mass)
(Because of strong hydrogen bonds)

Excellent solvent for polar & ionic compounds

Very high specific heat capacity

Expands when it freezes (unusual)
(Solid less dense than liquid -- also unusual)

30

Equation for heat involved in completion of a phase change

q = nΔHtransition

heat = # of mols * heat of [transition]

31

Equation for heat involved in temperature change 

q = (m) (Cs) (ΔT)