Chapter 12: Liquids & Solids Flashcards
Intermolecular forces
attractive forces that hold particles together in the condensed phases
The magnitude (and type) of intermolecular forces is what determines…
Phase
Surface tension
the amount of energy required to stretch or increase the surface of a liquid by a unit area
The stronger the intermolecular forces, the ______ the surface tension.
higher
Capillary action
the movement of a liquid up a narrow tube
The two types of forces bring about capillary action
Cohesion & adhesion
Cohesion
the attraction between like molecules
Adhesion
the attraction between unlike molecules
Viscosity
a measure of a fluid’s resistance to flow
The higher the viscosity the more ____ a liquid flows
slowly
Liquids that have higher intermolecular forces have _____ viscosities.
higher
If a molecule at the surface of a liquid has enough kinetic energy, it can escape to the gas phase in a process called:
Vaporization
The vapor pressure increases until
the rate of evaporation equals the rate of condensation.
When the forward process and reverse process are occurring at the same rate, the system is in
dynamic equilibrium
The vapor pressure increases with
Temperature
The Clausius–Clapeyron equation relates
the natural log of vapor pressure and the reciprocal of absolute temperature
Boiling point
the temperature at which the vapor pressure equals the external atmospheric pressure
Boiling point varies with (2 things):
- external pressure
2. the magnitude of intermolecular forces
Melting Point
the temperature at which the energies of the individual particles enable them to break free of their fixed positions.
Amorphous solids
lack a regular three-dimensional arrangement of atoms.
example: glass
crystalline solid
possess rigid and long-range order; its atoms, molecules, or ions occupy specific positions.
the basic repeating structural unit of a crystalline solid
unit cell
coordination number
the number of atoms surrounding an atom in a crystal lattice; indicates how tightly the atoms are packed together
The basic repeating unit in the array of atoms is called a
simple cubic cell
body-centered cubic cell
the spheres in each layer rest in the depressions between spheres in the previous layer (CN=8)
face-centered cubic cell (f c c), the coordination number is
12
A simple cubic cell has the equivalent of
only one complete atom contained within the cell.
A body-centered cubic cell has
two equivalent atoms
A face-centered cubic cell contains
four complete atoms
Ionic crystals
composed of charged ions that are held together by Coulombic attraction.
The unit cell of an ionic compound can be defined by either:
the positions of the anions or the positions of the cations.
In covalent crystals, atoms are held together in
an extensive three-dimensional network entirely by covalent bonds.
In molecular crystals, the lattice points are occupied by ______; the attractive forces between them are __________ and/or __________.
molecules
van der Waals forces and/or hydrogen bonding
metallic crystals
every lattice point is occupied by an atom of the same metal
Large cohesive force resulting from _____ makes metals strong
Delocolization
Delocalized electrons make metals good _____
conductors
phase
a homogeneous part of a system that is separated from the rest of the system by a well defined boundary
phase change
When a substance goes from one phase to another phase
molar heat of vaporization (ΔHvap )
the amount of heat required to vaporize a mole of substance at its boiling point
critical temperature
the temperature above which its gas cannot be liquified
critical pressure
the minimum pressure that must be applied to liquefy a substance at its critical temperature
fusion
melting
melting point (freezing point) of a solid (or liquid)
the temperature at which the solid and liquid phases coexist in equilibrium.
molar heat of fusion (ΔHfus )
the energy required to melt 1 mol of a solid.
Sublimation
the process by which molecules go directly from the solid phase to the vapor phase.
Deposition
the reverse process of sublimation
molar enthalpy of sublimation (ΔHsub)
the energy required to sublime 1 mole of a solid.
phase diagram
summarizes the conditions at which a substance exists as a solid, liquid, or gas
triple point
the only combination of pressure and temperature where three phases of a substance exist in equilibrium.
