Chapter 11: Liquids and Solids Flashcards by Gail I

liquids and solids are …, in which matter occupies a large fraction of the …, causing the characteristic high … and low …

condensed states; sample volume; densities; compressibilities

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solids and liquids are held together by

intermolecular forces

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intramolecular forces are chemical bonds that hold

atoms and ions together in compounds

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intermolecular forces affect the behavior of substances only when the molecules are

quite close together

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the physical state of any sample of matter depends on the …. and the average … of the molecules

strengths of the intermolecular attractions; kinetic energy

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the strengths of intermolecular attractions do not change much with

temperature

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at any instant, some molecules have kinetic energies greater than the … and others have kinetic energies ..

average; less than the average

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for gases energy of attraction is … kinetic energy of molecules

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for liquids, energy of attraction is …. kinetic energy of molecules

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for solids, energy of attraction is …. kinetic energy of molecules

> >

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at a given temp, a solid has … intermolecular attractions than a liquid, whereas a liquid has … intermoleular attractions than a gas

stronger; stronger

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the concept of distribution of energies also applies to molecules in the liquid state and is an important factor in evaporation, the conversion of molecules from the

liquid to the gas phase

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to escape from a liquid, a molecule must have a kinetic energy that is sufficient to …

overcome the forces of attraction from the other molecules

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for any temperature at which the liquid state is stable, only a small fraction of the moleules possess enough energy to evaporate, or vaporize– that is, have enough energy to

escape from the surface of the liquid

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rate of evaporation depends on the

temperature of the liquid

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the greater the temp, the greater the fraction of molecules that have …, and the faster the …

enough en ergy to evaorate; evaporation

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condensation: conversion of a

gas to a liquid

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the greater the number of gaseous molecules, the greater the rate of

condensation

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when the rate of condensation equals the rate of evaporation, the pressure in the vessel …, the constant pressure that is achieved is called the … of the liquid

no longer changes; vapor pressure

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a state of dynamic equilibrium is one in which two opposing changes occur

at equal rates (no net change is apparent)

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at equilibrium, both … continue to occur

opposing processes

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vapor pressure changes as the … changes

temperature

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rate of evaporation and the equilibrium vapor presure … with increasing temperature

increase

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

equal to the surrounding pressure

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vapor pressure is the pressure at which the rate of

evaporation equals the rate of condensation

the boiling point is a function of the surrounding pressure-- at lower surrounding pressures, a lower temperature is needed for the vapor pressure to

equal that pressure

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

equals one atmosphere

the stronger the intermolecular forces of attraction, the ... the boiling point

greater

vaporization is an ... process

endothermic

enthalpy of vaporization is the enthalpy change that accompanies the conversion of one mole of a substance from the

liquid state to the gaseous state at constant temp.

the higher the vapor pressure at a given temperature, the ... the intermolecular forces

weaker

enthalpy of vaporization is

endothermic

the larger the enthalpy of vaporization, the ... the intermolecular forces

greater

the enthalpy of vaporization of a liquid is the energy needed to separate the molecules by

overcoming the intermolecular attractions

the vapor pressure and rate of evaporation are low and the boiling point is high for a liquid with ... intermolecular forces

strong

critical temperature is the maximum temperature at which a substance can

exist in the liquid state

above its critical temp., no matter how high the applied pressure, a substance has only

one phase that completely occupies the volume of the vessel.

critical pressure is the minimum pressure needed to ... at the critical temperature

liquefy the substance

the single phase that exists above the critical temp and pressure is sometimes called a

supercritical fluid

the melting point of a substance is the temperature at which the

solid and liquid phases are in equilibrium

normal melting point is the temperature at which the solid and liquid phases are in equilibrium when the pressure is

1 atm

enhalpy of fusion is the enthalpy change that occurs when one mole of solid is converted to

liquid at a constant temperature

fusion is

endothermic

for any substance, the enthalpy of fusion is considerably ... than the enthalpy of vaporization

smaller

the energy required for melting overcomes some of the intermolecular attractions, giving the molecules greater freedom of motion but much less freedom than they

would have in the vapor phase

solidification (freezing) is reverse of fusion, so it has the same ... but different ..

magnitude; sign

supercooling is the cooling of liquid below its

melting pt without forming solid

a supercooled liquid is an ... state, and stirring or adding a small crystal of the substance causes the rapid ...

unstable; formation of the solid

solid too has

vapor pressure

sublimation is the direct conversion of a substance from

the solid state to the gaseous state

the reverse of sublimation, deposition, is the conversion of the gas

directly to the solid state

the opposing hanges of sublimation and deposiition lead to a state of dynamic equilibrium at an applied pressure equal to the

vapor pressure of the solid

enthalpy of sublimation is the enthalpy change for conversion of one mole of a solid to the

gaseous state

sublimation is

endothermic

enthalpy of sublimation=

enthalpy of fusion + enthalpy of vaporization

a phase diagram is a graph of ... versus ... that shows the region of stability for each of the ...

pressure; temperature; physical states

three line segments show the combination of temp and pressure at which any two phases exist in

equilibrium

the line that separates the liquid from the gas is the

vapor pressure curve

the triple point is a unique combination of temperature and pressure at which

all three phases are in a dynamic equilibrium

the liquid-gas equilibrium line ends at the ..., which indicates the ... and ...

critical point; critical temp; critical pressure

if two phases are in equilibrium and the pressure increases, a decrease in volume results by formation of the

denser phase

all intermolecular attractions depend on ..., the attraction between charges of ...

electrostatic interactions; opposite sign

dipole-dipole attractions are the intermolecular forces that arise from the electrostatic attractions between the

molecular dipoles

in general, the larger the dipole moment of a molecule, the

stronger the dipole-dipole attraction

dipoles exist due to the partial positive and negative charges on atoms produced by

unequal sharing of electrons

electrical charges or polar molecules close to a non-polar molecule can distort the nonpolar molecule's electron cloud and produce an

induced dipole moment

the intermolelcular force that exists between a permanent and induced dipole is called

dipole-induced dipole attraction

an instantaneous dipole is the result of an unequal ... within a molecule, caused by the ... of the electrons

charge distribution; motion

the very small charges of an instantaeous dipole in one nonpolar molecule can induce a dipole in a

nearby nonpolar molecule

london dispersion forces arise from the attractions between .. and ...

instantaneous and induced dipoles

polarizabilityrefers to the ease with which the electron cloud of a molecule can be

distorted by a nearby charge

the greater the polarizability, the greater the ... and the magnitude of the ...

induced dipole; electrostatic attraction

because molar mass increases with the size of the electron cloud, the strengths of intermolecular attractios usually increase with

increasing molar masses in related series of substances

london dispersion forces contribute to the attractions between

all molecules

een in molecules with dipole moments, most of the energy of intermolecular attractio arises from the

dispersion forces

van der Waals forces: collective term used to describe

dipole-dipole dipole-induced dipole instantaneous diple- induced dipole internations

london forces increase with the ... of the molecules

size

for related series of molecules, london forces increase going

down any group in the periodic table

hydrogen bonding occurs between a hydrogen atom that is bonded to a .... and a second ..., ..., or ... on a neighboring atom

small, highly electronegative atom; nitrogen, oxygen, fluorine

relative strength of forces (strongest on top)

covalent bonds hydrogen bonding dipole-dipole interactions london forces

small drops of liquids adopt a ... due to intermolecular forces

spherical shape

increasing the surface area of a liquid requires an expenditure of energy, because the number of surface molecules ..., ad each molecule on the surface hs fewer ... that attract it

increases; neighboring molecules

surface tension is the energy required to increse the

surface area of a liquid

surface tension is expressed in units of

J/m^2

the greater the intermolcular forces, the greater the

surface tension

a molecule in the interiro of a liquid is attrated by surrounding molecules

equally in all directions

a molecule at the surface of a liquid has unbalanced forces of attraction toward the ..., resulting in ...

interior of the liquid; surface tension

capillary action is the rising of water in a small diameter column against the forces of ... de to intermolecular forces

gravity

cohesion: is the attraction of molecules for

other molecules of the same substance

adhesion: the attraction that molecules of one substance exert on

those of different substance

the direction of curvature for the meniscus depends on the relative strengths of the

adhesive and cohesive forces

viscosity is the resistance of a fluid to

flow

the stronger the intermolecular forces between the molecules in a liquid, the more

viscous the liquid becomes

viscosity is also infleunced by

structure, size, and shape of molecules

solids can be ... or ...

crystalline; amorphous

crystalline solids have units that are arraned in a very

regular repeating pattern

crystalline solids are classified according to the types of ... that hold the units together

intermolecular forces

an amorphous solid lacks the order of

crystalline solids

many amorphous solids consist of large molecules that cause the liquid state to become

viscous as temperature is reduced

molecular solids are held together by

van der waals forces and/or hydrogen bonds

physical properties of molecular solids vary considerably depedning on the strength of

intermolecular interactions

covalent bonds hold the atoms together in the

molecules of molecular solids

molecular solids are usually ... substances with melting points <

soft; 300 C

in a covalent network solid, all of the satoms are hld in place by

covalent bonds

allotropes of carbon:

diamond (sp3), graphite (sp2)

alltotropes: term refers to two or more molecules/crystalline forms of an element in the same physical state that exhibit

different physical and chemical properties

many ... are also covalent network solids

minerals

ionic solids consist of oppositely charged ... held together by ... that are very strong

ions; electrostatic attractions

ionic compounds generally have high ... and are relatively ... and ...

melting points; hard; brittle

metallic solids are solids formed by

metal atoms

the metallic elements form crystalline solids that exhibit many unique properties such as

high thermal conductivity, good electrical conductivity, metallic luster

a special kind of bonding called ... accounts for properties of metallic soldids

metallic bonding

strength of attraction in metallic solids varies greatly so there are a wide range of ... for metallic substances

melting and boiling points

"electron sea" model used to describe metallic bonding: a sea of electrons with

metal ions embedded in it