Chem 102 Ch 11
how is molecular size related to viscosity? explain
a longer molecule has a higher viscosity (resistance to flow) because longer molecules may become entangled
for a concave meniscus to occur in a glass tube, which force must be greater than the other?
adhesive > cohesive
for capillary action to occur which force must be stronger than the other?
adhesive > cohesive
solids may be _____, in which the the atoms or molecules that compose them have no long-range order (give examples)
amorphous plastics and glass
the temperature at which a liquid's vapor pressure equals the external pressure is known as the ____
boiling point
___ is the ability of a liquid to flow against gravity up a narrow tube
capillary action
for a convex meniscus to occur in a glass tube, which force must be greater than the other?
cohesive > adhesive
capillary action occurs as the result of a combination of two forces: the attraction between molecules in a liquid called ____ and the attraction between these molecules and the surface of the tube called ____
cohesive forces, adhesive forces
the transition from gas to liquid, the opposite of vaporization, is known as ____
condensation
condensation is what kind of process. explain and give an example
condensation is exothermic because it releases energy, steam burns your hand because as it condenses to liquid on your hand it releases heat
intermolecular forces are responsible for the ____ of matter, ie liquid and solid
condensed phases
the ____ in a phase diagram represents the temperature and pressure above which a supercritical fluid exists
critical point
the pressure at which the transition of a supercritical fluid occurs is known as the ____
critical pressure
a supercritical fluid is formed by heating a liquid in a sealed container to the _____ causing the liquid and gas states to commingle
critical temperature
solids may be ____, in which the atoms or molecules that compose them are arranged in a well-ordered three dimensional array (give examples)
crystalline salt and diamonds
surface tension ____ as intermolecular forces decrease
decreases
surface tension _____ as temperature increases
decreases
when high energy molecules are lost from the liquid in vaporization, the average kinetic energy is lowered and the liquids temperature ____
decreases
the transition from a gas to a solid is known as ____ and occur when gas molecules collide with the surface of another molecule and are captured by the intermolecular forces
deposition
which intermolecular force is present in all molecules and atoms and is the result of fluctuations in the electron distribution within molecules or atoms
dispersion forces
what are the four types of intermolecular forces?
dispersion forces, dipole-dipole forces, hydrogen bonding, and ion-dipole forces
____ is reached when the rate of vaporization equals the rate of condensation
dynamic equilibrium (evaporation and condensation are still occurring but at equal amounts)
heat of vaporization and heat of condensation are ___ in value but ____ in sign
equal, opposite
along the vaporization curve, the liquid and solid states of water are ____
equally stable
true or false: in a hydrogen bond, the hydrogen bond is between the hydrogen and the oxygen, fluorine, or nitrogen atom within the same molecule
false: hydrogen bonds occur between the atoms of neighboring molecules
hydrogen bonding occurs between molecules that contain hydrogen atoms directly bonded to small electronegative atoms such as ____, ____, ____
fluorine, oxygen, nitrogen
in this state of matter, particles have complete freedom of motion and are widely spaced, expand to fill the container, take the container's shape, has a larger molar volume, and are compressible
gas
the molecules in a _____ have a great deal of space between them and are easily forced into a smaller volume by an increase in external pressure
gas
viscosity is _____ in substances with stronger molecular forces because if molecules are more strongly attracted to one another they do not flow around as freely
greater
a larger electron cloud results in a _____ because the electrons are held less tightly by the nucleus and therefore polarize more easily (larger fluctuations)
greater dispersion force
the amount of heat energy required to melt one mole of a solid is known as the ____
heat (enthalpy) of fusion
the amount of heat energy required to vaporize one mole of liquid is the ____
heat (or enthalpy) of vaporization
the heat of sublimation is equal to the sum of ____ and ____
heat of fusion, heat of vaporization
when thermal energy is high relative to intermolecular forces, matter tends to be _____. when thermal energy is low relative to intermolecular forces, matter tends to be ____ or _____
high: gas, low: liquid, solid
weaker intermolecular forces results in a more volatile liquid with a _____ vapor pressure
higher `
which force is the strongest of the intermolecular forces to occur in pure substances
hydrogen bonding
boiling points ____ with increasing dipole moment in polar molecules
increase
the boiling point ____ with increasing molar mass and stronger dispersion forces
increases
higher temperature does what to vapor pressure? why?
increasing the temperature increases the number of molecules with high enough energy to escape the liquid, therefore increasing the vapor pressure
the attractive forces that exist among the particles that compose matter, forces that hold liquids and solids together
intermolecular forces
the _____ force occurs when an ionic compound is mixed with a polar compound
ion-dipole
which force is the strongest intermolecular force and is the reason why ionic substances can form solutions with water?
ion-dipole force
nearly all liquids become ____ as temperature increases
less viscous
in this state of matter, particles are closely packed and can move around, they are incompressible, take the shape of their container, flow, and have a definite volume
liquid
increasing the pressure of a gas results in an immediate transition to a ____ state
liquid
at the ____ of a substance, the molecules have enough thermal energy to overcome the intermolecular forces that hold the molecules in their stationary parts and the solid turns to liquid
melting point
is curving of the liquid surface in a thin tube is called the ____ and it is due to competition between adhesive and cohesive forces
meniscus
why will liquid mercury only form a convex meniscus?
metallic bonds (cohesive force) are stronger than intermolecular attractions
when equilibrium is disturbed, the system responds to ____ the disturbance and return to equilibrium
minimize
in liquids, the ability to mix without separating into two states is known as ____
miscibility
at room temperature, what level of intermolecular forces tend to result in liquids and solids (with a high melting and boiling point)?
moderate to strong
maple syrup is _____ than water
more viscous
in the clausius clapeyron equation, which two variables are linearly related?
natural log of vapor pressure and inverse temperature
which elements on the periodic table are nonpolar atoms and therefore only have dispersion forces
noble gases
liquids that do not evaporate easily are referred to as _____ and have strong attractive forces between molecules therefore requiring ____ energy to evaporate. give an example of a substance
nonvolatile, more, motor oil
the _____ of a liquid is the temperature at which the vapor pressure equals one atm
normal boiling point
heat of solidification and heat of fusion are equal in value but ___ in sign
opposite
polar molecules have some areas that are electron poor and some areas that are electron rich. this results in an molecule with a _____
permanent dipole
____ is a map of the state or phase of a substance as a function of pressure and temperature
phase diagram
dipole-dipole forces exists in all molecules that are _____
polar
in terms of intermolecular forces, why do polar molecules have greater melting and boiling points than nonpolar molecules?
polar molecules have dispersion forces as well as dipole-dipole forces acting on them whereas nonpolar molecules only have dispersion forces
in terms of miscibility, polar substances will generally mix with ___ substances and nonpolar substances will mix with _____ substances
polar, nonpolar
the heat of vaporization is always ___ in sign because the process is _____
positive, endothermic (energy must be absorbed to vaporize a substance)
the heat of fusion is always ___ in sign because it is an ____ process
positive, exothermic
in this state of matter, particles are closely packed and have limited restricted motion, are incompressible, retain shape and volume when placed in a new container, and do not flow
solid
in a phase diagram, the regions represent ___ and the lines represent ____
states, state changes
larger charges in a molecule results in a _____ attraction whereas a longer distance between molecules results in a ___ attraction
stronger, weaker
the _____ of the particles that compose a substance determines the strength of the intermolecular forces that hold the substance together, which in turn determines whether the substance is a solid, liquid, or gas
structure
____ occurs when a solid transitions to a gas
sublimation
the ____ separates the solid and gas and the ____ separates the solid and liquid
sublimation curve, fusion curve
a _____ has unique properties of both liquids and solids and can act as a good solvent (ie removing caffeine from coffee beans)
supercritical fluid
the ___ of a liquid is the energy required to increase the surface area by a unit amount
surface tension
___ is the tendency of a liquids to minimize their surface area - because interactions lower potential energy, the greater number of interactions, the ____ the potential energy
surface tension, lower
states of matter can be transformed from one to the other by changing the ____, ____ or both
temperature, pressure
rate of vaporization increases with increasing _____, _____. rate of vaporization increases with decreasing _____
temperature, surface area strength of intermolecular forces
when electrons are not symmetrically arranged around the nucleus, a slight positive and a slight negative charge will ensue on opposite sides of the molecule. this fleeting charge separation is called a ____
temporary dipole (instantaneous)
in which isomer (element with the same number of electrons ie same molecular weight) will the dispersion forces be higher: a straight chain isomer or a branched chain isomer? why?
the straight chain isomer will have higher dispersion forces (and therefore a higher boiling point) because the straight shape allows the electrons in the isomer to interact with each other along the entire length of the molecule
the state of a sample of matter (solid, liquid, gas) depends on the magnitude of intermolecular forces among the constituent particles relative to the amount of ____ in the sample
thermal energy
the ____ in a phase diagram represents the unique set of conditions at which the three states are equally stable and in equilibrium
triple point
pressure exerted by a gas in dynamic equilibrium with its liquid is known as ____
vapor pressure
the process by which thermal energy can overcome intermolecular forces and produce a state change from liquid to gas
vaporization
vaporization is what kind of process. explain and give an example
vaporization is endothermic because it takes energy to overcome the intermolecular forces, sweat
____ is the resistance of a liquid to flow ie unflowability
viscosity
liquids that vaporize easily are referred to as ____ and have weaker attractive forces between molecules therefore requiring ___ energy to evaporate. give an example of a substance
volatile, less, acetone
at room temperature, what level of intermolecular forces results in gases (with a low melting and boiling point)?
weak
even the strongest intermolecular forces are generally much ___ than bonding forces
weaker
