Chapter 11 - Liquids and Intermolecular Forces Flashcards
Define condensed phases.
solid and liquid states of matter
What is the fundamental difference between states of matter?
the strength of the intermolecular forces of attraction
List five characteristics of gas.
- assumes both volume and shape of its container
- expands to fill its container
- is compressible
- flows readily
- diffusion within a gas occurs rapidly
List five characteristics of liquid.
- assumes shape of portion of container it occupies
- does not expand to fill its container
- is virtually incompressible
- flows readily
- diffusion within a liquid occurs slowly
List five characteristics of solids.
- retains own shape and volume
- does not expand to fill its container
- is virtually incompressable
- does not flow
- diffusion within a solid occurs extremly slowly
How does kinetic energy compare to the energy of attraction for gas?
kinetic energies»_space; energies of attraction
How does kinetic energy compare to the energy of attraction for liquids?
comparable kinetic energies and energy of attraction
How does kinetic energy compare to the energy of attraction for solids?
energies of attraction»_space; kinetic energies
List five physical properties that reflect intermolecular forces.
boiling point, melting point, viscosity, surface tension, capillary action
The attractions between molecules are (stronger/weaker) then the intermolecular attractions that hold compounds together.
weaker
List the four types of molecular forces from strongest to weakest.
- dispersion forces
- dipole-dipole forces
- hydrogen bonding
- ion-dipole forces
What two types of intermolecular forces are referred to collectively as van der Waals forces?
dispersion forces, dipole-dipole forces
Which type of intermolecular force is a special type of dipole-dipole force?
hydrogen bonding
Define polarizability.
the tendency of an electron cloud to distort
What three factors affect the amount of dispersion force in a molecule?
- the number of electrons in an atom
- the size of the atom or molecule (molecular weight)
- shape of molecules with similar masses
How does the number of electrons in an atom affect the amount of dispersion force in a molecule?
more electrons = more dispersion force
How does the shape of molecules with similar masses affect the amount of dispersion force in a molecule?
more compact = less dispersion force
What is the relationship between polarizability and boiling point?
If something is easier to polarize, it has a lower boiling point. This means less intermolecular force.
Explain dipole-dipole interactions.
Polar molecules have a more positively charged end and a more negatively charged end, collectively referred to as a dipole. The oppositely charged ends attract each other.
On what molecules do dipole-dipole interactions have a greater effect then dispersion forces?
molecules of comparable side and shape
On what molecules do dispersion forces have a greater effect then dipole-dipole interactions?
molecules with significant differences in size
Define hydrogen bonds.
an attraction between a hydrogen atom attached to a highly electronegative atom and a nearby small electronegative atom in another molecule or chemical group
What is unusual about the dipole-dipole interactions when H is bonded to N, O, or F?
they are unusually stong
What forms hydrogen bonds?
Hydrogen bonding arises in part from the high electronegativity of nitrogen, oxygen, and flourine. These atoms interact with a nearly bare nucleus (which contains one proton).
Where are ion-dipole interactions found?
in solutions of ions
What makes it possible for ionic substances to dissolve in polar solvents?
the strength of ion-dipole interactions
Define viscosity.
the resistance of a liquid to flow
How is viscosity affected by intermolecular forces?
Viscosity increases with stronger intermolecular forces and decreases with higher temperature.
Define surface tension.
extra inward forces on the surface of a liquid
Define cohesive forces.
intermolecular forces that bind similar molecules to one another
Define adhesive forces.
intermolecular forces that bind a substance to a surface
Define capillary action.
the rise of liquids up narrow tubes due to adhesive and cohesive forces
Define phase change.
conversion from one state of matter to another
List three phase changes.
- melting/freezing
- vaporizing/condensing
- subliming/depositing
Define heat of fusion.
the energy required to change a solid at its melting point to a liquid
Define heat of vaporization.
the energy required to change a liquid at its boiling point to a gas
Define heat of sublimation.
the energy required to change a solid directly to a gas
Define heating curve.
a plot of temperature verses heat added
Define heat within a phase.
the produt of specific heat, sample mass and temperature change
The temperature of the substance (does/does not) rise during a phase change.
does not
Define heat during phase changes.
the product of mass and the heat of fusion of vaporization
Define critical temperature.
the temperature beyond which a gas cannot be compressed
Define critical pressure.
the pressure needed to compress the liquid at critical temperature
Define supercritical fluid.
the state beyond critical temperature
What does gas do when pressure is applied?
it liquefies
Define boiling point.
the temperature at which a liquid’s vapor pressure equals its atmospheric pressure
Define normal boiling point.
the temperature at which a liquid’s vapor pressure is 760 torr
Define vapor pressure.
the pressure of a vapor in contact with its liquid or solid form
What relationship does the Clausius-Clapeyron equation quantify?
the natural log of the vapor pressure of a liquid is inversely proportional to its temperature
Define phase diagram.
a graph of pressure verses temperature for a substance
What information does a phase diagram convey?
melting, boiling, and sublimation points at different pressures, the triple point and the critical point
Define liquid crystals.
the intermediate state that some substances experience between solid and liquid state that has some traits of solids and some of liquids
Define nematic liquid crystals.
liquid crystal in which the molecules are only ordered in one dimension along the long axis
Define smetic liquid crystals.
liquid crystal in which molecules are ordered in two dimensions, along the long axis and in layers
Define cholesteryic liquid crystals.
liquid crystals in which nematic-like crystals are layered at angles to each other
