Chapter 10: Liquids and Solids Flashcards
Condensed states
Liquids and solids
Intermolecular forces
Forces that occur between molecules
Dipole-dipole attraction
Molecules with dipole moments can attract each other electrostatically by lining up so that the positive and negative ends are close to each other
Hydrogen bonding
Particularly strong dipole-dipole forces where hydrogen is bound to a highly electronegative atom, such as N, O, or F
London dispersion forces
The forces, existing among noble gas atoms and nonpolar molecules, that involve an accidental dipole that induces a momentary dipole in a neighbor
Surface tension
The resistance of a liquid to an increase in its surface area
Capillary action
The spontaneous rising of a liquid in a narrow tube
Cohesive forces
The intermolecular forces among the molecules of the liquid
Adhesive forces
The forces between the liquid molecules and their container
Viscosity
A measure of a liquid’s resistance to flow
Crystalline solids
Solids with a highly regular arrangement of their components
Amorphous solids
Solids with considerable disorder in their structures
Lattice
A three-dimensional system of points designating the positions of the components (atoms, ions, or molecules) that make up the substance
Unit cell
The smallest repeating unit of the lattice
Bragg equation
nλ = 2d sin θ
n = integer λ = wavelength of the x rays d = distance between the atoms θ = angle of incidence and reflection
Ionic solid
A solid containing cations and anions that dissolves in water to give a solution containing the separated ions, which are mobile and thus free to conduct an electric current
Molecular solid
A solid composed of neutral molecules at the lattice points
Bonding: Dipole-dipole and/or London dispersion forces
Atomic solid
A solid that contains atoms at the lattice points
Three types of atomic solids
- Metallic - metal, delocalized covalent bonding
- Network - nonmetal, directional covalent
- Group 8A - group 8A, London dispersion forces
Closest packing
Packing uniform, hard spheres in a manner that most efficiently uses the available space
aba Arrangement
The third layer occupies positions so that each sphere in the third layer lies directly over a sphere in the first layer (Hexagonal unit cell, hexagonal closest packed structure)
abc Arrangement
The third layer occupies positions so that no sphere in the third layer lies over one in the first layer (face-centered cubic unit cell, cubic closest packed structure)
In both hcp and ccp structures, each sphere has __ equivalent nearest neighbors.
12
- 6 in the same layer
- 3 in the layer above
- 3 in the layer below (that form the dimples)
How many atoms are in a face-centered cubic unit cell?
(8 x 1/8) + (6 x 1/2) = 4
How many atoms are in a simple cubic unit cell?
(8 x 1/8) = 1
How many atoms are in a body-centered cubic unit cell?
(8 x 1/8) + 1 = 2
Alloy
A substance that contains a mixture of elements and has metallic properties
Substitutional alloy
Some of the host metal atoms are REPLACED by other metal atoms of similar size.
Interstitial alloy
When some of the interstices (holes) in the closest packed metal structure are occupied by small atoms
Network solids
Atomic solids that contain strong directional covalent bonds to form a solid viewed as a “giant molecule”
(e.g.: Two most common forms of carbon: graphite and diamond)
Silica
The fundamental silicon-oxygen compound, which has the empirical formula SiO2, and forms the basis of quartz and certain types of sand.
Diamond
Each carbon atom is surrounded by a tetrahedral arrangement, stabilized by covalent bonds.
Graphite
Layers of carbon atoms arranged in fused six-membered rings. Each carbon atom in a particular layer of graphite is surrounded by the three other carbon atoms in a trigonal planar arrangement.
Silicates
Salts that contain metal cations and polyatomic silicon-oxygen anions that are usually polymeric.
Glass
An amorphous solid obtained when silica is mixed with other compounds, heated above its melting point, and then cooled rapidly (HOMOGENEOUS)
Quartz
Based on interconnected SiO4 tetrahedra with shared oxygen atoms, composed of silica
Ceramics
Made from clays (which contain silicates) and hardened by firing at high temperatures. Nonmetallic materials that are strong, brittle, and resistant to heat and attack by chemicals (HETEROGENEOUS: minutes crystals of silicates that are suspended in a glassy cement)
Semiconductor
A substance conducting only a slight electric current at room temperature, but showing increased conductivity at higher temperatures
n-type semiconductor
A substance whose conductivity is increased by doping it with atoms having more valence electrons than the atoms in the host crystal
p-type semiconductor
A substance whose conductivity is increased by doping it with atoms having fewer valence electrons than the atoms of the host crystal
Size of the the three holes in closest packed structures from smallest to largest
Trigonal
In the closest packed structure, there are _____ as many tetrahedral holes as packed anions
Twice
Vaporization/evaporation
The change in state that occurs when a liquid evaporates to form a gas (ENDOTHERMIC)
Heat/enthalpy of vaporization
The energy required to vaporize 1 mole of a liquid at a pressure of 1 atm
Condensation
The process by which vapor molecules re-form a liquid
Equilibrium
When enough vapor molecules are present above the liquid so that the rate of condensation equals the rate of evaporation, thus the two opposite processes exactly balance each other
Vapor pressure
The pressure of the vapor present at equilibrium
Volatile
Describes liquids with high vapor pressures and evaporate rapidly from an open dish
Vapor pressure decreases with…
Larger intermolecular forces and molar masses
Vapor pressure increases with…
Higher temperatures
Vapor pressure and heat of vaporization equation
ln(Pvap) = -(∆Hvap/R)(1/T) + C
T = Kelvin temperature R = universal gas constant = 8.3145 J/K • mol C = constant characteristic of a given liquid
Change in Vapor Pressures and Temperatures equation
ln(Pvap,T1/Pvap,T2) = (∆Hvap/R)(1/T2 - 1/T1)
Heating curve
A plot of temperature versus time for a process where energy is added at a constant rate
Heat/enthalpy of fusion
The enthalpy change that occurs at the melting point when a solid melts
Normal melting point
The temperature at which the solid and liquid states have the same vapor pressure under conditions where the total pressure is 1 atmosphere
Normal boiling point
The temperature at which the vapor pressure of the liquid is exactly 1 atmosphere
Supercooling
The process of cooling a liquid below its freezing point without its changing to a solid
Superheating
The process of heating a liquid above its boiling point without its boiling
Triple point
The point on a phase diagram at which all three states of a substance are present
Critical temperature
The temperature above which the vapor cannot be liquefied no matter what pressure is applied
Critical pressure
The pressure to produce liquefaction at the critical temperature
Critical point
The point on a phase diagram at which the temperature and pressure have their critical values; the endpoint of the liquid-vapor line
