Chapter 11: Liquids and Intermolecular Forces

Question 1

What does the state of a substance depend on?

Answer 1

the balance between the KE of particles and the attraction energies between particles

Question 2

Which one is weaker: intermolecular forces or intramolecular forces?

Answer 2

intermolecular forces

Question 3

What are the 4 types of intermolecular forces?

Answer 3

dispersion forces | dipole-dipole interactions | ion-dipole | hydrogen bonding

Question 4

What are van der Waals forces?

Answer 4

dispersion forces and dipole-dipole interactions

Question 5

Who discovered dispersion forces?

Answer 5

Fritz London

Question 6

What are (London) dispersion forces?

Answer 6

one atom’s movement of electrons influence that of its neighbor atoms SO = an INSTANTANEOUS dipole on one atom can induce an instantaneous dipole on an adjacent atom

Question 7

What does the strength of the dispersion force depend on?

Answer 7

the polarizability of a molecule

Question 8

What is the polarizability of a molecule?

Answer 8

how charge distribution is manipulated to induce the instantaneous dipole

Question 9

What does an increase in the polarizability of a molecule indicate?

Answer 9

easier the electron cloud could be manipulated to give an instantaneous dipole

Question 10

What is the relationship between dispersion forces and molecular weight and its affect on boiling point?

Answer 10

dispersion forces are stronger as MW increases = increases boiling point

Question 11

What are dipole-dipole interactions due to?

Answer 11

permanent dipole moments in polar molecules

Question 12

When are dipole-dipole and dispersion interactions effective?

Answer 12

when the molecules are very close to each other

Question 13

What is hydrogen bonding?

Answer 13

an attraction between the H (of an -OH, -NH, or -FH) and a nearby electronegative atom in another molecule/compound

Question 14

What are ion-dipole forces?

Answer 14

exists between an ion and a polar molecule (ie: NaCl in H2O)

Question 15

In what substances are dispersion forces found?

Answer 15

ALL substances

Question 16

Order the 4 intermolecular forces from strongest to weakest.

Answer 16

ion-dipole > H-bonding > dipole-dipole > dispersion

Question 17

What is viscosity?

Answer 17

resistance of a liquid to flow | how easily do molecules flow past each other

Question 18

What does an increase in viscosity indicate?

Answer 18

slow flow

Question 19

What does a decrease in viscosity indicate?

Answer 19

fast flow (like water)

Question 20

What does viscosity depend on?

Answer 20

attractive forces between the molecules

Question 21

What is the SI unit for viscosity?

Answer 21

kg/ms

Question 22

How does a increase in temperature affect viscosity?

Answer 22

decrease in viscosity

Question 23

What is surface tension?

Answer 23

molecules at the surface experience a net inward force that pulls them closer to the middle = decrease in surface area

Question 24

What is surface tension due to?

Answer 24

the imbalance of intermolecular forces at the surface of the liquid

Question 25

What is the unit for surface tension?

Answer 25

J/m^2

Question 26

What is capillary action?

Answer 26

crawl of liquids up a very narrow tube

Question 27

What is cohesive forces?

Answer 27

intermolecular forces that bind similar molecules to one another

Question 28

What is adhesive forces?

Answer 28

intermolecular forces that bind a substance to a surface

Question 29

What causes the convex meniscus of water? (cohesion adhesion relationship)

Answer 29

cohesion forces H2O < adhesion forces H2O

Question 30

What causes the concave meniscus of Hg? (cohesion adhesion relationship)

Answer 30

cohesion forces Hg > adhesion forces Hg

Question 31

What are phase changes?

Answer 31

state changes of a substance | transformations

Question 32

What is sublimation?

Answer 32

solid changes directly to gas

Question 33

What is fusion?

Answer 33

melting

Question 34

What is heat of fusion?

Answer 34

(∆Hfus) energy that allows increased freedom of motion particles

Question 35

What is vapor pressure?

Answer 35

pressure exerted by the vapor of a liquid when the liquid and vapor are in dynamic equilibrium

Question 36

How does an increase in temperature affect vapor pressure of a gas in solution?

Answer 36

increases vapor pressure until vapor pressure equals the external pressure above the liquid

Question 37

What is heat of vaporization?

Answer 37

(∆Hvap) energy needed for a quantity of liquid to change into vapor (gas)

Question 38

What is heat of sublimation?

Answer 38

(∆Hsub) energy needed for solid to directly change into gas

Question 39

What is the relationship between the heat of sublimation, heat of vaporization and heat of fusion?

Answer 39

∆Hsub = ∆Hvap + ∆Hfus

Question 40

What is the opposite of sublimation?

Answer 40

deposition

Question 41

What is the opposite of vaporization?

Answer 41

condensation

Question 42

What is the opposite of fusion?

Answer 42

freezing

Question 43

What is critical temperature?

Answer 43

highest temperature at which a distinct liquid phase can form and liquid can exist at

Question 44

What is critical pressure?

Answer 44

pressure needed to bring about the liquefaction at the critical temperature

Question 45

How does an increase in intermolecular forces strength affect critical temp/pressure?

Answer 45

increases critical temp/pressure

Question 46

What is supercritical fluid?

Answer 46

when temperature > critical temp and pressure > critical pressure BUT liquid and gas phases are indistinguishable from each other

Question 47

What state is supercritical fluid in?

Answer 47

gas/liquid = can expand to fill container but molecules are still close to each other

Question 48

What is dynamic equilibrium?

Answer 48

condition where 2 opposing processes occur at the same time at equal rates

Question 49

What is volatile?

Answer 49

describes liquids that readily evaporate

Question 50

How does intermolecular forces and vapor pressure affect how volatile a liquid can be?

Answer 50

liquid with weak intermolecular forces and high vapor pressure = highly volatile (compare with strong IMForces and low vapor pressure)

Question 51

What is a boiling point?

Answer 51

temperature at which its vapor pressure equals the external pressure acting on the liquid's surface

Question 52

What is a normal boiling point?

Answer 52

boiling point of a liquid at 1 atm

Question 53

What are the 3 curves on a phase diagram (temp vs pressure)?

Answer 53

vapor pressure curve | sublimation curve | melting curve

Question 54

What does the vapor pressure curve represent?

Answer 54

equilibrium between liquid and gas phases

Question 55

What is the critical point?

Answer 55

critical temperature and critical pressure

Question 56

What does the sublimation curve represent?

Answer 56

change in vapor pressure of the solid as it sublimes at different temperature | curve is the equilibrium between solid and gas phases

Question 57

What does the melting curve represent?

Answer 57

change in melting point of a solid as pressure changes | curve is the equilibrium between solid and liquid phases

Question 58

What is the normal melting point?

Answer 58

melting point at 1 atm

Question 59

What is the triple point?

Answer 59

where all 3 phases are in equilibrium as their curves all intersect at this point