Hi-Q Chemistry

amorphous solid

a solid that has a disordered structure; it lacks the well-defined arrangement of basic units (atoms, molecules, or ions) found in a crystal

buffer

a solution characterized by the ability to resist changes in pH when limited amounts of acid or base are added to it

amphiprotic species

a species that can act as either an acid or a base (that is, it can lose or gain a proton)

chemical bond

a strong attractive force that exists between certain atoms in a substance

catalyst

a substance that increases the rate of reaction without being consumed in the overall reaction

acid

a substance that produces hydrogen ions, H-, (hydronium ion, H3O+) when it dissolves in water; the species (molecule or ion) that donates a proton to another species in a proton-transfer reaction

basic oxide

an oxide that reacts with acids

actinides

elements in the last of the two rows at the bottom of the periodic table; the 14 elements following actinium in the periodic table, in which the 5f subshell is filling

cell reaction

the net reaction that occurs in a voltaic cell

chemical vapor deposition

a process in which a chemical reaction in a gas or vapor produces a product that can be deposited onto a solid material or substrate

addition reaction

a reaction in which parts of a reactant are added to each carbon atom of a carbon-carbon double bond, which becomes a C-C single bond

combination reaction

a reaction in which two substances combine to form a third substance

combustion reaction

a reaction of a substance with oxygen, usually with the rapid release of heat to produce a flame

acid salt

a salt that has an acidic hydrogen atom and can undergo neutralization with basics

chain reaction, nuclear

a self-sustaining series of nuclear fissions caused by the absorption of neutrons released from previous nuclear fisisions

codon

a sequence of three bases in a messenger RNA molecule that serves as the code for a particular amino acid

base

a substance that produces hydroxide ions, OH-, when it dissolves in water; the species (molecule or ion) that accepts proton in a proton-transfer reaction

absolute temperature scale

a temperature scale in which the lowest temperature that can be attainted theoretically is zero

atmosphere (atm)

a unit of pressure equal to exactly 760 mmHg; 1 atm = 101.325 kPa (exact)

alkaline dry cell

a voltaic cell that is similar to the Lechanche dry cell but uses potassium hydroxide in place of ammonium chloride

atomic orbital

a wave function for an electron in an atom; pictured qualitatively by describing the region of space where there is a high probability of finding the electron

angular momentum quantum number (l)

also known as the azimuthal quantum number; the quantum number that distinguishes orbitals of given n having different shapes; it can have any integer value from 0 to n-1

bonding pair

an electron pair shared between two atoms

bimolecular reaction

an elementary reaction that involves two reactant molecules

atomic theory

an explanation of the structure of matter in terms of different combinations of very small particles (atoms)

atom

an extremely small particle of matter that retains its identity during chemical reactions

complex ion

an ion formed from a metal ion with a Lewis base attached to it by a coordinate covalent bond

amphoteric oxide

an oxide that has both acidic and basic properties

acidic oxide

an oxide that reacts with bases

activated complex (transition state)

an unstable grouping of atoms that can break up to form products

activity of a radioactive source

the number of nuclear disintegrations per unit time occurring in a radioactive material

atomic number (Z)

the number of protons in the nucleus of an atom

coagulation

the process by which the dispersed phase of a colloid is made to aggregate and thereby separate from the continuous phase

cathode rays

the rays emitted by the cathode (negative electrode) in a gas discharge tube (tube of low-pressure gas through which an electric current is discharged)

band of stability

the region in which stable nuclides lie in a plot of number of protons against number of neutrons

common-ion effect

the shift in an ionic equilibrium caused by the addition of a solute that provides an ion that takes part in the equilibrium

chemical equilibrium

the state reached by a reaction mixture when the rates of forward and reverse reactions have become equal

chemical kinetics

the study of how reaction rates change under varying conditions and of what molecular events occur during the overall reaction

chemical equation

the symbolic representation of a chemical reaction in terms of chemical formulas

chemical nomenclature

the systematic naming of chemical compounds

boiling point

the temperature at which the vapor pressure of a liquid equals the pressure exerted on the liquid (atmospheric pressure, unless the vessel containing the liquid is closed)

celsius scale

the temperature scale in general scientific use; there are exactly 100 units between the freezing point and the normal boiling point of water

change of state

a change of a substance from one state to another

catalysis

the increase in rate of a reaction as the result of the addition of a catalyst

Avogadro's number

the number of atoms in a 12-g sample of carbon-12, equal to 6.02 x 10^23 to three significant figures

acid-base indicator

a dye used to distinguish between acidic and basic solutions by means of the color changes it undergoes in these solutions

activity series

a listing of the elements in order of their ease of losing electrons during reactions in aqueous solutions

atomic mass unit (amu)

a mass unit equal to exactly one-twelfth the mass of a carbon-12 atom

alloy

a material with metallic properties that is either a compound or a mixture

amphoteric hydroxide

a metal hydroxide that reacts with both acids and bases

Claus process

a method of obtaining free sulfur by the partial burning of hydrogen sulfide

chemical formula

a notation that uses atomic symbols with numerical subscripts to convey the relative proportions of atoms of the different elements in a substance

atomic symbol

a one- or two-letter notation used to represent an atom corresponding to a particular element

acid-base titration curve

a plot of the pH of a solution of acid (or base) against the volume of added base (or acid)

chromatography

a name given to a group of similar separation techniques that depend on how fast a substance moves, in a stream of gas or liquid, past a stationary phase to which the substance may be slightly attracted

anion

a negatively charged ion

addition polymer

a polymer formed by linking together many molecules by addition reactions

cation

a positively charged ion

base pairing

the hydrogen bonding of complementary bases

calorie (cal)

a non-SI unit of energy commonly used by chemists, originally defined as the amount of energy needed to raise the temperature of 1 g of water by 1 degree Celsius; equal to 4.184 J

angstrom

a non-SI unit of length; 1 A = 10^-10 m

calorimeter

a device used to measure the heat absorbed or evolved during a physical or chemical change

colloid

a dispersion of particles of one substance (the dispersed phase) throughout another substance or solution (the continuous phase)

chlor-alkali mercury cell

a cell for the electrolysis of aqueous sodium chloride in which mercury metal is used as the cathode

chlor-alkali membrane cell

a cell for the electrolysis of aqueous sodium chloride in which the anode and cathode compartments are separated by a special plastic membrane that allows only cations to pass through it

chemical reaction

a change in which one or more kinds of matter are transformed into a new kind of matter or several new kinds of matter; the rearrangement of the atoms present in the reacting substances to give new chemical combinations present in the substances formed by the reaction

chemical property

a characteristic of a material involving its chemical change

complete ionic equation

a chemical equation in which strong electrolytes (such as soluble ionic compounds) are written as separate ions in the solution

boiling-point elevation

a colligative property of a solution equal to the boiling point of the solution minus the boiling point of the pure solvent

binary compound

a compound composed of only two elements

complex (coordination compound)

a compound consisting either of complex ions and other ions of opposite charge or of a neutral complex species

alcohol

a compound obtained by substituting a hydroxyl group (-OH) for an -H atom on a tetrahedral (sp3 hybridized) carbon atom of a hydrocarbon group

body-centered cubic unit cell

a cubic unit cell in which there is a lattice point at the center of the unit cel as well as at the corners

barometer

a device for measuring the pressure of he atmosphere

alpha emission

emission of a 4,2He nucleus, or alpha particle, from an unstable nucleus

beta emission

emission of a high-speed electron from an unstable nucleus

bond order

in a Lewis formula, the number of pairs of electrons in a bond. In molecular orbital theory, one-half the difference between the number of bonding electrons and the number of anti bonding electrons

antibonding orbitals

molecular orbitals having zero values in the region between two nuclei and therefore concentrated in other regions

bonding orbitals

molecular orbitals that are concentrated in regions between nuclei

bent geometry

nonlinear molecular geometry, in the case of a molecule of three atoms

ceramics

nonmetallic, inorganic solids that are hard and brittle and usually produced at elevated temperature

complementary bases

nucleotide bases that form strong hydrogen bonds with one another

axial direction

one of two directions pointing from the center of a trigonal bipyramid along its axis

allotrope

one of two or more distinct forms of an element in the same physical state

chiral

possessing the quality of handedness; has a mirror image that is not identical to the object

colligative properties

properties that depend on the concentration of solute molecules or ions in a solution but not on the chemical identity of the solute

acid rain

rain having a pH lower than that of natural rain, which has a pH of 5.6

atomic weight

the average atomic mass for the naturally occurring element, expressed in atomic mass units

bond energy

the average enthalpy change for the breaking of a bond in a molecule in the gas phase

ampere (A)

the base unit of current in the International system (SI)

chemisorption

the binding of a species to a surface by chemical bonding forces

adsorption

the binding or attraction of molecules to a surface

catenation

the covalent bonding of two or more atoms of the same element to one another

bond length (bond distance)

the distance between the nuclei in a bond

anode

the electrode at which oxidation occurs

binding energy

the energy needed to break a nucleus into its individual protons and neutrons

acid-ionization constant (Ka)

the equilibrium constant for the ionization of a weak acid

base-ionization constant

the equilibrium constant for the ionization of a weak base

alkali metals

the group IA elements; they are reactive metals

alkaline earth metals

the group IIA elements; they are reactive metals, though less reactive than the alkali metals