Chapter 11: Liquids and Solids Flashcards
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
solids and liquids are held together by
intermolecular forces
intramolecular forces are chemical bonds that hold
atoms and ions together in compounds
intermolecular forces affect the behavior of substances only when the molecules are
quite close together
the physical state of any sample of matter depends on the …. and the average … of the molecules
strengths of the intermolecular attractions; kinetic energy
the strengths of intermolecular attractions do not change much with
temperature
at any instant, some molecules have kinetic energies greater than the … and others have kinetic energies ..
average; less than the average
for gases energy of attraction is … kinetic energy of molecules
for liquids, energy of attraction is …. kinetic energy of molecules
=
for solids, energy of attraction is …. kinetic energy of molecules
> >
at a given temp, a solid has … intermolecular attractions than a liquid, whereas a liquid has … intermoleular attractions than a gas
stronger; stronger
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
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
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
rate of evaporation depends on the
temperature of the liquid
the greater the temp, the greater the fraction of molecules that have …, and the faster the …
enough en ergy to evaorate; evaporation
condensation: conversion of a
gas to a liquid
the greater the number of gaseous molecules, the greater the rate of
condensation
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
a state of dynamic equilibrium is one in which two opposing changes occur
at equal rates (no net change is apparent)
at equilibrium, both … continue to occur
opposing processes
vapor pressure changes as the … changes
temperature
rate of evaporation and the equilibrium vapor presure … with increasing temperature
increase
boiling point of a liquid is the temperature at which the vapor pressure is
equal to the surrounding pressure
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
