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Chem > Ch 10 Section 4 > Flashcards

Ch 10 Section 4 Flashcards

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1
Q

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

A

overcome the attraction of neighboring molecules

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2
Q

a phase is any part of a system that has

A

uniform composition and properties

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3
Q

condensation is the process by which a

A

gas changes to a liquid

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4
Q

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

A

vapor

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5
Q

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

A

constant

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6
Q

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

A

gas phase, so the rate of condensation is very low

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7
Q

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

A

rate of condensation to increase

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8
Q

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

A

equilibrium is established

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9
Q

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

A

equal rates in a closed system

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10
Q

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

A

net change in the amount of substance in either phase

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11
Q

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

A

proportional to the concentration of molecules in the vapor phase

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12
Q

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

A

equilibrium with its corresponding liquid

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13
Q

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

A

kinetic-molecular theory for the liquid and gaseous states

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14
Q

increasing the temperature of a liquid increases the

A

average kinetic energy of the liquid’s molecules

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15
Q

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

A

escape from the liquid phase into the vapor phase

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16
Q

the resulting increased evaporation rate increases the number of

A

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

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17
Q

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

A

equilibrium vapor pressure at a given temperature

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18
Q

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

A

evaporate at any given temperature is

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19
Q

a low percentage of evaporation results in a low

A

equilibrium vapor pressure

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20
Q

volatile liquids are liquids that

A

evaporate readily

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21
Q

volatile liquids have relatively weak forces of

A

attraction between their particles

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22
Q

ether is a typical

A

volatile liquid

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23
Q

nonvolatile liquids do not

A

evaporate readily

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24
Q

nonvolatile liquids have relatively strong attractive

A

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

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25
Q

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

A

boiling

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26
Q

boiling is the conversion of a liquid to a

A

vapor within the liquid as well as at its surface

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27
Q

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

A

also increases

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28
Q

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

A

equals the atmospheric pressure

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29
Q

the lower the atmospheric pressure is, the lower the

A

boiling point is

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30
Q

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

A

constant as long as the pressure does not change

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31
Q

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

A

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

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32
Q

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

A

shorter cooking time

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33
Q

vacuum evaporator causes boiling at lower-than-normal

A

temperatures

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34
Q

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

A

avoid scorching milk or sugar

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35
Q

at normal atmospheric pressure, the boiling pt of water is

A

exactly 100 degrees celsius→normal boiling pt

36
Q

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

A

760 torr

37
Q

energy must be added continuously in order to keep a liquid

A

boiling

38
Q

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

A

same constant temperature

39
Q

the temperature at the boiling point remains constant despite the

A

continuous addition of energy

40
Q

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

A

stored in the vapor as potential energy

41
Q

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…

A

vaporize; boiling point at constant pressure

42
Q

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

A

attraction between particles of the liquid

43
Q

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

A

higher molar enthalpy of vaporization

44
Q

each liquid has a characteristic

A

molar enthalpy of vaporization

45
Q

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

A

hydrogen bonding in liquid water

46
Q

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

A

cooling agent

47
Q

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

A

escape from the liquid surface and become vapor

48
Q

the physical change of a liquid to a solid is called

A

freezing

49
Q

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

A

heat; liquid→solid + energy

50
Q

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

A

equilibrium at 1 atm pressure

51
Q

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

A

average kinetic energy

52
Q

energy loss during freezing is a loss of

A

potential energy that was present in the liquid

53
Q

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

A

ordered than the liquid state, even at the same temp

54
Q

melting, also occurs at

A

constant temperature

55
Q

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

A

solid + energy→liquid

56
Q

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

A

the same

57
Q

at equilibrium, melting and freezing proceed at

A

equal rates

58
Q

the following general equilibrium equation can represent these states:

A

solid + energy ⇄ liquid

59
Q

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

A

both ice and water are present

60
Q

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

A

surrounding temperature

61
Q

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

A

right

62
Q

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

A

ice

63
Q

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

A

temperature of the system

64
Q

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

A

melt; melting point

65
Q

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

A

attractive forces holding them together

66
Q

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

A

solid to liquid

67
Q

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

A

attraction between the solid particles

68
Q

at sufficiently low temperature and pressure conditions, a liquid

A

cannot exit

69
Q

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

A

vapor instead of its liquid

70
Q

equation for solid existing in equilibrium with vapor:

A

solid + energy ⇄vapor

71
Q

sublimation is the change of state from a solid

A

directly to a gas

72
Q

deposition is the change of state from a gas

A

directly to a solid

73
Q

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

A

phases of a substance exists

74
Q

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

A

changing temperature or pressure

75
Q

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

A

coexist at equilibrium

76
Q

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

A

coexist at equilibrium

77
Q

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

A

melting point

78
Q

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

A

coexist at equilibrium

79
Q

the critical point of a substance indicates the

A

critical temperature and critical pressure

80
Q

the critical temperature is the temperature above which the substance cannot

A

exist in the lqiuid state

81
Q

critical temperature of water is

A

373.99 degrees celsius

82
Q

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

A

pressure is applied

83
Q

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

A

liquid at the critical temperature

84
Q

the critical pressure of water is

A

217.75 atm

85
Q

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

A

decreasing pressure

86
Q

below the triple point, the temperature of sublimation decreases with

A

decreasing pressure

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