Chemistry Chapter 12

Front 1

phase

Back 1

a physically distinct portion of a system.

Front 2

intermolecular forces

Back 2

the attractive and repulsive forces among the particles-molecules, atoms, or ions-in a sample of matter.

Front 3

phase changes

Back 3

a physical change from one phase to another, usually refering to a change in physical state

Front 4

condensation

Back 4

the process of a gas changing into a liquid

Front 5

vaporization

Back 5

the process of changing from a liquid to a gas.

Front 6

melting (fusion)

Back 6

the change of a substance from a solid to a liquid.

Front 7

freezing

Back 7

the process of cooling a liquid until it solidifies.

Front 8

heat of vaporization

Back 8

the enthalpy change occurring when 1 mol of a liquid substance vaporizes.

Front 9

heat of fusion

Back 9

the enthalpy change occurring when 1 mol of a solid substance melts

Front 10

sublimation

Back 10

the process by which a solid changes directly into a gas.

Front 11

deposition

Back 11

the process of changing directly from gas to solid

Front 12

heat of sublimation

Back 12

the enthalpy change occurring when 1 mol of a solid substance changes directly to a gas. the sum of the heats of fusion and vaporization

Front 13

heating-cooling curve

Back 13

a plot of temperature vs. time for a substance when heat is absorbed or released by the system at a constant rate.

Front 14

vapor pressure

Back 14

the pressure exerted by a vapor at equilibriumwith its liquid in a closed system.

Front 15

clausius-clapeyron equation

Back 15

an equation that expresses the relationship between vapor pressure of a liquid and temperature

Front 16

boiling point

Back 16

the temperature at which the vapor pressure of a gas equals the external (atmospheric) pressure.

Front 17

melting point

Back 17

the temperature at which the solid and liquid forms of a substance are at equilibrium.

Front 18

critical point

Back 18

the point on a phase diagram above which teh vapor cannot be condensed to a liquid; the end of the liquid-gas curve.

Front 19

phase diagram

Back 19

a diagram used to describe the stable phases and phase changes of a substance as a function of temperature and pressure.

Front 20

van der waals radius

Back 20

one-half of the closest distance between teh nuclei of identical nonbonded atoms

Front 21

dipole-dipole forces

Back 21

the intermolecular between oppositely charged poles of nearby polar molecules.

Front 22

hydrogen bond (H bond)

Back 22

a type of dipole-dipole force that arises between molecules that have an H atom bonded to a small, highly electronegative atom with lone pairs, usually N, O, or F

Front 23

polarizability

Back 23

the ease with which a particle's electron cloud can be distorted.

Front 24

dipersion force (London force)

Back 24

the intermolecular attraction between oppositely charged poles of nearby polar molecules.

Front 25

surface tension

Back 25

the energy required to increase the surface area of a liquid by a given amount.

Front 26

capillarity

Back 26

a property that results in a liquid rising through a narrow space against the pull of gravity

Front 27

unit cell

Back 27

the smallest portion of a crystal that, if repeated in all three directions, gives the crystal.

Front 28

coordination number

Back 28

in a crystal, the number of nearest neighbors surrounding a particle.

Front 29

simple cubic unit cell

Back 29

a unit cell in which a particle occurs at each corner of a cube

Front 30

body-centered cuic unit cell

Back 30

a unit cell in which a particule lies at each corner and in the center of a cube.

Front 31

face-centered cubic unit cell

Back 31

a unit cell in which a particle occurs at each corner and in the center of each face of a cube.

Front 32

packing efficiency

Back 32

the percentage of the available voume occupied by atoms, ions, or molecules in a unit cell.

Front 33

hexagonal closest packing

Back 33

a crystal structure based on the hexagonal unit cell in which teh layers have an abab... pattern.

Front 34

cubic closest packing

Back 34

a crystal structure based on the face-centered cubic unit cell in which the layers have an abcabc... pattern.

Front 35

atomic solid

Back 35

a solid consisting of individual atom sheld together by dispersion foces; the frozen noble gases are the only example.

Front 36

molecular solid

Back 36

a solid held together by intermolecular forces between individual molecules.

Front 37

ionic solid

Back 37

a solid whose unit cell contains cations and anions.

Front 38

metallic solid

Back 38

a solid whose individual atoms are held together by metallic bonding

Front 39

network covalent solid

Back 39

a solid in which all the atoms are bonded covalently.

Front 40

band theory

Back 40

an extension of molecular orbital theory that explains many properties of metals, in particular, the differences in electrical conductivity of conductors, semiconductors, and insulators.

Front 41

valence band

Back 41

in band theory, the lowerenergy portion of the band of molecular orbitals, which is filled with valence electrons.

Front 42

conduction band

Back 42

In band theory, the empty, higher energy portion of the band of molecular orbitals into which electrons move when condcuting heat and electricity.

Front 43

conductor

Back 43

a substance (usually a metal) that conducts an electric current well.

Front 44

semiconductor

Back 44

a substance whose electrical conductivity is poor at room temperature but increases significantly with rising temperature.

Front 45

insulator

Back 45

a substance (usually a nonmetal) that does not conduct an electric current

Front 46

superconductivity

Back 46

the ability to conduct a current with no loss of energy to resistive heating.

Front 47

crystal defects

Back 47

any of a variety of disruptions in teh regularity of a crystal structure.

Front 48

doping

Back 48

adding small amounts of other elements into the crystal structure of a semiconductor to enhance a specific property, usually conductivity.

Front 49

liquid crystals

Back 49

a substance taht flows like a liquid but packs like a crystalline solid at the molecular level.

Front 50

ceramic

Back 50

a nonmetallic, nonpolymeric solid that is hardened by heating it to high temperatures and, in most cases, consists of silicatemicrocrystals suspended in a glassy cementing medium.

Front 51

degree of polymerization

Back 51

the number of monomer repeat units in a polymer chain.

Front 52

random coil

Back 52

teh shape adopted by most polymer chains adn causec by random rotation about the bodns joining the repeat units.

Front 53

radius of gyration

Back 53

a measure of the size of a coiled polymer chain as teh averae distance from the cnter of mass of the chain to its outside edge.

Front 54

branch

Back 54

a side chain appended to a polymer backbone.

Front 55

crosslinks

Back 55

a branch that covalently joins one polymer chain to another

Front 56

elastomers

Back 56

a polymeric material that can be stretched and springs back to its original shape when released.

Front 57

nanotechnology

Back 57

the science and engineering of nanoscale (1-100 nm)systems.