Ch 10 Section 4

Question 1

some liquid chemical substances have odors that are easily detected because some molecules at the upper surface of the liquid have enough energy to

Answer 1

overcome the attraction of neighboring molecules

Question 2

a phase is any part of a system that has

Answer 2

uniform composition and properties

Question 3

condensation is the process by which a

Answer 3

gas changes to a liquid

Question 4

a gas in contact with its liquid or solid phase is often called a

Answer 4

vapor

Question 5

if the temperature of the liquid remains constant and the cap remains closed, the rate at which molecules move from the liquid phase to the vapor phase remains

Answer 5

constant

Question 6

near the beginning of the evaporation process, very few molecules are in the

Answer 6

gas phase, so the rate of condensation is very low

Question 7

but as more liquid evaporates, the increasing number of gas molecules causes the

Answer 7

rate of condensation to increase

Question 8

eventually, the rate of condensation equals the rate of evaporation, and a state of

Answer 8

equilibrium is established

Question 9

equilibrium is a dynamic condition in which two opposing changes occur at

Answer 9

equal rates in a closed system

Question 10

even though molecules are constantly moving between liquid and gas phases, there is no

Answer 10

net change in the amount of substance in either phase

Question 11

vapor molecules in equilibrium with a liquid in a closed system exert a pressure

Answer 11

proportional to the concentration of molecules in the vapor phase

Question 12

the equilibrium vapor pressure of the liquid is the pressure exerted by a vapor in

Answer 12

equilibrium with its corresponding liquid

Question 13

the increase in equilibrium vapor pressure with increasing temperature can be explained in terms of the

Answer 13

kinetic-molecular theory for the liquid and gaseous states

Question 14

increasing the temperature of a liquid increases the

Answer 14

average kinetic energy of the liquid’s molecules

Question 15

this energy change increases the number of molecules that have enough energy to

Answer 15

escape from the liquid phase into the vapor phase

Question 16

the resulting increased evaporation rate increases the number of

Answer 16

molecules in the vapor phase, which in turn increases the equilibrium vapor pressure

Question 17

because all liquids have characteristic forces of attraction between their particles, every liquid has a specific

Answer 17

equilibrium vapor pressure at a given temperature

Question 18

the stronger these attractive forces are, the smaller the percentage of liquid particles that can

Answer 18

evaporate at any given temperature is

Question 19

a low percentage of evaporation results in a low

Answer 19

equilibrium vapor pressure

Question 20

volatile liquids are liquids that

Answer 20

evaporate readily

Question 21

volatile liquids have relatively weak forces of

Answer 21

attraction between their particles

Question 22

ether is a typical

Answer 22

volatile liquid

Question 23

nonvolatile liquids do not

Answer 23

evaporate readily

Question 24

nonvolatile liquids have relatively strong attractive

Answer 24

forces between their particles (e.g. molten ionic compounds)

Question 25

equilibrium vapor pressures can be used to explain and defined the concept of

Answer 25

boiling

Question 26

boiling is the conversion of a liquid to a

Answer 26

vapor within the liquid as well as at its surface

Question 27

if the temperature of the liquid is increased, the equilibrium vapor pressure

Answer 27

also increases

Question 28

the boiling point of a liquid is the temperature at which the equilibrium vapor pressure of the liquid

Answer 28

equals the atmospheric pressure

Question 29

the lower the atmospheric pressure is, the lower the

Answer 29

boiling point is

Question 30

at the boiling point, all of the energy absorbed is used to evaporate the liquid, and the temperature remains

Answer 30

constant as long as the pressure does not change

Question 31

if the pressure above the liquid being heated is increased, the temperature of the liquid will rise until the vapor pressure equals the

Answer 31

new pressure and the liquid boils once again→principle behind pressure cooker

Question 32

the pressure cooker is sealed so that the steam pressure builds up over the surface of the boiling water, the pressure increases the boiling temp of h20, resulting in

Answer 32

shorter cooking time

Question 33

vacuum evaporator causes boiling at lower-than-normal

Answer 33

temperatures

Question 34

vacuum evaporators remove water from milk & sugar solutions. under reduced pressure, the water boils away at a temperature low enough to

Answer 34

avoid scorching milk or sugar

Question 35

at normal atmospheric pressure, the boiling pt of water is

Answer 35

exactly 100 degrees celsius→normal boiling pt

Question 36

the normal boiling pt of each liquid is the temperature at which the liquid's equilibrium vapor pressure equals

Answer 36

760 torr

Question 37

energy must be added continuously in order to keep a liquid

Answer 37

boiling

Question 38

if you were to carefully measure the temperature of a boiling liquid and its vapor you would find that they are at the

Answer 38

same constant temperature

Question 39

the temperature at the boiling point remains constant despite the

Answer 39

continuous addition of energy

Question 40

the added energy is used to overcome the attractive forces between molecules of the liquid during the liquid-to-gas change and is

Answer 40

stored in the vapor as potential energy

Question 41

a liquid's molar enthalpy of vaporization is the amount of energy as heat that is needed to... one mole of liquid at the liquid's...

Answer 41

vaporize; boiling point at constant pressure

Question 42

the magnitude of the molar enthalpy of vaporization is a measure of the

Answer 42

attraction between particles of the liquid

Question 43

the stronger this attraction (between particles of a liquid) is, the more energy that is required to overcome it, which results in a

Answer 43

higher molar enthalpy of vaporization

Question 44

each liquid has a characteristic

Answer 44

molar enthalpy of vaporization

Question 45

water has an unusually high molar enthalpy of vaporization due to the extensive

Answer 45

hydrogen bonding in liquid water

Question 46

the high molar enthalpy of vaporization of water makes water a very effective

Answer 46

cooling agent

Question 47

at the higher temperature (distribution of kinetic energies of molecules in a liquid at 2 different temps), a greater portion of the molecules have the kinetic energy required to

Answer 47

escape from the liquid surface and become vapor

Question 48

the physical change of a liquid to a solid is called

Answer 48

freezing

Question 49

freezing involves a loss of energy in the form of ...by the liquid and can be represented by the following reaction:

Answer 49

heat; liquid→solid + energy

Question 50

the normal freezing point is the temperature at which the solid and liquid are in

Answer 50

equilibrium at 1 atm pressure

Question 51

at the freezing point, particles of the liquid and the solid have the same

Answer 51

average kinetic energy

Question 52

energy loss during freezing is a loss of

Answer 52

potential energy that was present in the liquid

Question 53

at the same time energy decreases, there is a significant increase in particle order because the solid state of a substance is much more

Answer 53

ordered than the liquid state, even at the same temp

Question 54

melting, also occurs at

Answer 54

constant temperature

Question 55

as a solid melts, it continuously absorbs energy as heat, represented by following equation:

Answer 55

solid + energy→liquid

Question 56

for pure crystalline solids, the melting point and freezing point are

Answer 56

the same

Question 57

at equilibrium, melting and freezing proceed at

Answer 57

equal rates

Question 58

the following general equilibrium equation can represent these states:

Answer 58

solid + energy ⇄ liquid

Question 59

the temperature of a system containing ice and liquid water will remain at 0 degrees celsius as long as

Answer 59

both ice and water are present

Question 60

the temperature of a system containing ice and liquid water will persist no matter what the

Answer 60

surrounding temperature

Question 61

adding energy in the form of heat to such a system (liquid water and ice) shifts the equilibrium to the

Answer 61

right

Question 62

that shift increases the proportion of liquid water and decreases that of

Answer 62

ice

Question 63

only after all the ice has melted will the addition of energy increase the

Answer 63

temperature of the system

Question 64

a solid's molar enthalpy of fusion is the amount of energy as heat required to ...one mole of solid at the solid's

Answer 64

melt; melting point

Question 65

the energy absorbed increases the solid's potential energy as its particles are pulled apart, overcoming the

Answer 65

attractive forces holding them together

Question 66

there is a significant decrease in particle order as the substance transforms from

Answer 66

solid to liquid

Question 67

similar to molar enthalpy of vaporization, the magnitude of the molar enthalpy of fusion depends on the

Answer 67

attraction between the solid particles

Question 68

at sufficiently low temperature and pressure conditions, a liquid

Answer 68

cannot exit

Question 69

under such conditions ( sufficiently low temperature and pressure conditions) a solid substance exists in equilibrium with its

Answer 69

vapor instead of its liquid

Question 70

equation for solid existing in equilibrium with vapor:

Answer 70

solid + energy ⇄vapor

Question 71

sublimation is the change of state from a solid

Answer 71

directly to a gas

Question 72

deposition is the change of state from a gas

Answer 72

directly to a solid

Question 73

a phrase diagram is a graph of pressure versus temperature that shows the conditions under which the

Answer 73

phases of a substance exists

Question 74

a phase diagram reveals how the states of a system change with

Answer 74

changing temperature or pressure

Question 75

in water phase diagram, curve ac indicates the temperature and pressure conditions at which ice and water vapor can

Answer 75

coexist at equilibrium

Question 76

in water phase diagram, curve AD indicates the temperature and pressure conditions at which ice and liquid water

Answer 76

coexist at equilibrium

Question 77

because ice is less dense than liquid water, an increase in pressure lowers the

Answer 77

melting point

Question 78

the triple point of a substance indicates the temperature and pressure conditions at which the solid, liquid, and vapor of the substance can

Answer 78

coexist at equilibrium

Question 79

the critical point of a substance indicates the

Answer 79

critical temperature and critical pressure

Question 80

the critical temperature is the temperature above which the substance cannot

Answer 80

exist in the lqiuid state

Question 81

critical temperature of water is

Answer 81

373.99 degrees celsius

Question 82

above water's critical temperature, water cannot be liquefied, no matter how much

Answer 82

pressure is applied

Question 83

the critical pressure is the lowest pressure at which the substance can exist as a

Answer 83

liquid at the critical temperature

Question 84

the critical pressure of water is

Answer 84

217.75 atm

Question 85

in phase diagram of water , slope of line ad shows that ice melts at a higher temperature with

Answer 85

decreasing pressure

Question 86

below the triple point, the temperature of sublimation decreases with

Answer 86

decreasing pressure