Exam I

condensed
Solid and liquid states are known as the __ states
more
Solid and liquid states are __ similar to each other than they are to the gas state
gas
In the __ state, constituent particles – atoms or molecules – are separated by large distances and do not interact with each other very much
condensed
In the _ states, constituent particles are close together and exert moderate to strong attractive forces on one another
Intermolecular forces
__ – attractive forces that exist between all molecules and atoms
condensed
Intermolecular forces are responsible for the very existence of __ states
magnitude
The state sample of matter – solid, liquid, or gas – depends on __ of intermolecular forces between constituent particles, relative to the amount of thermal energy in the sample
thermal energy
The molecules and atoms composing matter are in constant random motion that increases with increasing temperature. The energy associated with this motion is called __
gaseous
When thermal energy is high relative to intermolecular forces, matter tends to be __
liquid or solid
When thermal energy is low relative to intermolecular forces, matter tends to be _
greater
Densities of the solid and liquid states are much __ than the densities of the gas state
more
Solid and liquid states are _ similar in density and molar volume to one another than they are to the gas state
less
For water, the solid is slightly __dense than the liquid. This is atypical behavior
denser
Most solids are slightly __ than their corresponding liquids because the molecules move closer together upon freezing
movement
Major difference between liquids and solids is the freedom of __ of the constituent molecules or atoms
thermal
Even though the atoms or molecules in a liquid are in close contact, __ energy partially overcomes the attractions between them, allowing them to move around one another
solid
The atoms or molecules in a __ are virtually locked in their positions, only vibrating back and forth about a fixed point
free
Liquids assume the shape of their containers because the atoms or molecules that compose liquids are __ to flow (or move around one another)
Liquids
__ are not easily compressed because the molecules or atoms that compose them are already in close contact – they cannot be pushed much closer together
gas
The molecules in a __ have a great deal of space between them and are easily compressed
Solids
__ have a definite shape because the molecules or atoms that compose solids are fixed in place – each molecule or atom merely vibrates about a fixed point
cannot
Solids have a definite volume and generally __ be compressed because the molecules or atoms composing them are already in close contact
crystalline
Solids may be __, in which case the atoms or molecules that compose them are arranged in a well-ordered 3-D array
amorphous
Solids may be __, in which case the atoms or molecules that compose them have no long-range order
temperature, pressure, or both
We can transform one state of matter to another by changing the __
denser
Increases in pressure favor the __ state, so increasing the pressure of a gas sample results in a transition to the liquid state
does not
When something changes states its chemical composition __ change
state – solid, liquid, or gas –
The strength of the intermolecular forces between the molecules or atoms that compose a substance determine its __ at a given temperature
liquids and solids
gases
At room temperature, moderate to strong intermolecular forces tend to result in __ (high melting and boiling points) and weak intermolecular forces tend to result in __ (low melting and boiling points)
charges, partial charges, and temporary charges
Intermolecular forces originate from the interactions between __ on molecules (or atoms and ions), much as bonding forces originate from interactions between charged particles in atoms
Coulomb’s law
According to __, the potential energy (E) of two oppositely charged particles (with charges q¬¬1 and q2) decreases (becomes more negative) with increasing magnitude of charge and with decreasing separation (r)
decreases
Protons and electrons are attracted to each other because their potential energy __ as they get closer together
potential energy
Molecules with partial or temporary charges are attracted to each other because their __ decreases as they get closer together
bonding
Intermolecular forces, even the strongest ones, are generally much weaker than __ forces
large charges
Bonding forces are the result of __ (the charges on protons and electrons) interacting at very close distances
smaller charges
Intermolecular forces are the result of __ interacting at greater distances
dispersion forces, dipole-dipole forces, hydrogen bonding, and ion-dipole forces
what are the different types of intermolecular forces
Dispersion
__ forces can potentially occur in all substances
Ion-dipole
__ forces occurs only in mixtures
London force
The one intermolecular force present in all molecules and atoms is the dispersion force (also called the __)
electron distribution
Dispersion forces are the result of fluctuations in the __ within molecules or atoms
instantaneous dipole or a temporary dipole
The electrons in an atom or molecule may, at any one instant, be unevenly distributed. Having the electrons be unevenly distributed around the nucleus will give the different sides of an atom or molecule slightly negative or positive charges. This fleeting change separation is called an __
neighboring
An instantaneous dipole on one atom induces an instantaneous dipole on its __ atoms because the positive end of the instantaneous dipole attracts electrons in the neighboring atoms
dispersion force
The neighboring atoms then attract one another – the positive end of one instantaneous dipole attracting the negative end of another. This attraction is the __
polarize
The magnitude of the dispersion force depends on how easily the electrons in the atom or molecule can more or __ in response to an instantaneous dipole, which in turn depends on the size (or volume) of the electron cloud
greater dispersion force
A larger electron cloud results in a __ because the electrons are held less tightly by the nucleus and therefore polarize more easily
increases
The dispersion force __ with increasing molar mass because molecules or atoms of higher molar mass generally have more electrons dispersed over a greater volume
increasing
As the molar masses and electron cloud volume increases, the greater the dispersion force which results in __ boiling points
molecular shape
molar mass alone does not determine the magnitude of the dispersion force. __ can also determine magnitude of the dispersion force
polar
The dipole-dipole force exists in all molecules that are __
dipole-dipole
Polar molecules have permanent dipoles that interact with the permanent dipoles of neighboring molecules. The positive end of one permanent dipole attracts the negative end of another; this attraction is the __ force
higher
Polar molecules, therefore have __ melting and boiling points than nonpolar molecules of similar molar mass
nonpolar
All molecules (including polar ones) have dispersion forces, but polar molecules have, in addition, dipole-dipole forces. Polar molecules have a raised melting and boiling points relative to __ molecules because of the additional attractive force (dipole-dipole forces)
increase
Boiling points __ with increasing dipole moment
miscibility
The polarity of molecules composing liquids is also important in determining the __ of liquids
Miscibility
_ – the ability to mix without separating into two states
are
are not
Polar liquids __ miscible with other polar liquids but __ miscible with nonpolar liquids
hydrogen bonding
Polar molecules containing hydrogen atoms bonded directly to small electronegative atoms – most importantly fluorine, oxygen, or nitrogen – exhibit an intermolecular force called __
F, O, or N
The large electronegativity difference between hydrogen and any of these electronegative elements causes the hydrogen atom to have a fairly large partial positive charge (g+) within the bond, while the __ atom has a fairly large partial negative charge (g-)
hydrogen bonding
Since these atoms are quite small, the H atom on one molecule can approach the F, O, or N atom on an adjacent molecule very closely. This results in a strong attraction between the H atom on one molecule and the F, O, or N on its neighbor, an attraction called __
WITHIN
BETWEEN
Chemical bonds occur between individual atoms __ a molecule, whereas hydrogen bonds are intermolecular forces that occur __ molecules
stronger
Hydrogen bonds are __ than dipole-dipole forces and dispersion forces
higher
Substances composed of molecules that form hydrogen bonds have __ melting and boiling points than substances composed of molecules that do not form hydrogen bonds
ionic
Ion-dipole force occurs when an __ compound is mixed with a polar compound; it is especially important in aqueous solutions of ionic compounds
Ion-dipole
__ forces are the strongest of the types of intermolecular forces
Surface tension
__ – the tendency of liquids to minimize their surface area
less
The molecule at the surface has relatively fewer neighbors with which to interact and is therefore inherently __ stable – has higher potential energy – than those in the interior
lower
Attractive interactions with other molecules __ potential energy
requires
In order to increase the surface area of the liquid, molecules from the interior have to be moved to the surface, and, since molecules at the surface have a higher potential energy than those in the interior, this movement __ energy
minimize
liquids tend to __ their surface area
surface tension
The __ of a liquid is the energy required to increase the surface area by a unit amount
decreases
Surface tension __ as intermolecular forces decrease
viscosity,
the resistance of a liquid to flow
poise (P)
Viscosity is measure in a unit called the __, defined as 1 g/cm x s
stronger
Viscosity is greater in substances with _ intermolecular forces because if molecules are more strongly attracted to each other, they do not flow around each other as freely
molecular shape
Viscosity also depends on _, increasing in longer molecules that can interact over a greater area and possibly become entangled
molar mass
length
Notice the increase in viscosity with increasing __ (and therefore increasing magnitude of dispersion forces) and with increasing __ (and therefore increasing potential for molecular entanglement)
temperature
Viscosity also depends on __because thermal energy partially overcomes the intermolecular forces, allowing molecules to flow past each other more easily
less
Nearly all liquids become __ viscous as temperature increases
cohesive
adhesive
the attraction between molecules in a liquid, called __ forces, and the attraction between these molecules and the surface of the tube, called __ forces
spread out
stay together
The adhesive forces cause the liquid to __ over the surface of the tube, while the cohesive forces cause the liquid to __
greater
If the adhesive forces are greater than the cohesive forces, the attraction to the surface draws the liquid up the tube and the cohesive forces pull along those molecules not in direct contact with the tube walls
smaller
If the adhesive forces are __ than the cohesive forces, the liquid does not rise up the tube at all (and in fact will drop to a level below the level of the surrounding liquid)
Meniscus
__ = curved shape of a liquid surface within a tube
Vaporization
__ – the process by which thermal energy can overcome intermolecular forces and produce a state change from liquid to gas
energy
The higher the temperature, the greater the average __ of the collection of molecules
thermal
At any one time, some molecules would have more __ energy than the average and some would have less
vaporization
transition from liquid to gas to called __
condensation
transition from gas to liquid is called
vaporization
if we increase the temperature of the water within the beaker, the shift in the energy distribution to higher energies will make it to where more molecules now have enough energy to break free and evaporate, so __ occurs more quickly
more
if we spill the water on the table/floor, the same amount of water is now spread over a wider area, resulting in more molecules at the surface of the liquid. Since molecules at the surface have the greatest tendency to evaporate – because they are held less tightly – vaporization also occurs __ quickly
temperature
substances with weaker intermolecular forces allow more molecules to evaporate at a given __, again increasing the rate of vaporization
volatile
liquids that vaporize easily = __
nonvolatile
liquids that do not vaporize easily = __
increases
The rate of vaporization __ with increasing temperature
increases
The rate of vaporization __ with increasing surface area
decreasing
The rate of vaporization increases with __ strength of intermolecular forces
endothermic
Vaporization is an _ process; it takes energy to vaporize the molecules in a liquid
exothermic
condensation is __ – heat is released when a gas condenses to a liquid
heat of vaporization (?Hvap)
The amount of heat required to vaporize one mole of a liquid to a gas is its __
positive
The heat of vaporization is always __ because the process is endothermic – energy must be absorbed to vaporize a substance
somewhat
The heat of vaporization is __ temperature dependent
same amount
When a substance condenses from a gas to a liquid, the __ of heat is involved, but the heat is emitted rather than absorbed
exothermic
The sign of ?H when a gas condenses from a gas to a liquid is negative because the process is __
Dynamic equilibrium
__: rate of evaporation = rate of condensation
condensation
As the rate of concentration (or partial pressure) of gaseous water molecules increases, the rate of __ also increases
constant
As long as water remains at a __ temperature, the rate of evaporation remains constant
vapor pressure
The pressure of a gas in dynamic equilibrium with its liquid is called its __
temperature
The vapor pressure of a particular liquid depends on the intermolecular forces present in the liquid and the __
volatile
Weaker intermolecular forces result in __ substances with high vapor pressures because the intermolecular forces are easily overcome by thermal energy
low
Strong intermolecular forces result in nonvolatile substances with __ vapor pressures
return
A liquid in dynamic equilibrium with its vapor is a balanced system that tends to __ to equilibrium if disturbed
Le Chatelier’s principle
If the pressure above a liquid-vapor system in equilibrium is decreased, some of the liquid evaporates, restoring the equilibrium pressure. If the pressure is increased, some of the vapor condenses, bringing the pressure back down to the equilibrium pressure
falls
When a system in dynamic equilibrium has an increase in volume, the vapor pressure __. More gas vaporizes so that pressure is restored, and dynamic equilibrium is restored
rises
When a system in dynamic equilibrium has a decrease in volume, the vapor pressure __. More gas condenses so that pressure is restored, and dynamic equilibrium is restored