Calorie

(cal) - A unit of energy defined as exactly 4.184 joules; originally defined as the heat needed to raise the temperature of 1 gallon of water 1°C.

Calorimetry

The measurement of heat changes.

Carbides

Ionic compounds containing the C²²² or C⁴² ion.

Carboxylic Acids

Acids that contain the carboxyl group OCOOH.

Catalyst

A substance that increases the rate of a chemical reaction without itself being consumed.

Catenation

The ability of the atoms of an element to form bonds with one another.

Cathode

The electrode at which reduction occurs.

Cation

An ion with a net positive charge.

Cell Voltage

Difference in electrical potential between the anode and the cathode of an electrochemical cell.

Charles and Gay-Lussac’s Law

See Charles’ law.

Charles’ Law

The volume of a fixed amount of gas maintained at constant pressure is directly proportional to the absolute temperature of the gas.

Chelating Agent

A substance that forms complex ions with metal ions in solution.

Chemical Change

A change in which a substance is converted into a substance with different composition and properties.

Chemical Energy

Energy stored within the structural units of chemical substances.

Chemical Equation

An equation that uses chemical symbols to show what happens during a chemical reaction.

Chemical Equilibrium

At state in which the rates of the forward and reverse reactions are equal.

Chemical Formula

An expression showing the chemical composition of a compound in terms of the symbols for the atoms of the elements involved.

Chemical Kinetics

The area of chemistry concerned with the speeds, or rates, at which chemical reactions occur.

Chemical Property

Any property of a substance that cannot be studied without converting the substance into some other substance.

Chemical Reaction

A process in which a substance (or substances) is changed into one or more new substances.

Chemistry

The study of matter and the changes it undergoes.

Chiral

Compounds or ions that are not superimposable with their mirror images.

Chlo-Alkali Process

The production of chlorine gas by the electrolysis of aqueous NaCl solution.

Closed System

A system that allows the exchange of energy (usually in the form of heat) but not mass with its surroundings.

Closest Packing

The most efficient arrangements for packing atoms, molecules, or ions in a crystal.

Cohesion

The intermolecular attraction between like molecules.

Colligative Properties

Properties of solutions that depend on the number of solute particles in solution and not on the nature of the solute particles.

Colloid

A dispersion of particles of one substance (the dispersed phase) throughout a dispersing medium made of another substance.

Combination Reaction

A reaction in which two or more substances combine to form a single product.

Combustion Reaction

A reaction with oxygen and air, often with release of heat and light.

Common Ion Effect

The shift in equilibrium caused by the addition of a compound having an ion in common with the dissolved substances.

Common Names

Names given to chemical compounds that give no clues to their chemical composition such as water, salt, sugar, etc.

Complex Ion

An ion containing a central metal cation bonded to one or more molecules or ions.

Compound

A substance composed of atoms of two or more elements chemically united in fixed proportions.

Concentration

The amount of solute present in a given quantity of solvent or solution.

Condensation

The phenomenon of going from the gaseous state to the liquid state.

Condensation Polymer

A polymer formed by monomers with two functional groups that are linked together in a dehydration-condensation reaction.

Condensation Reaction

A reaction in which two smaller molecules combine to form a larger molecule. Water is invariably one of the products of such a reaction.

Conductor

Substance capable of conducting electric current.

Conformational Isomers

Isormers that arise from rotations around a single bond.

Conjugate Acid-Base Pair

An acid and its conjugate base or a base and its conjugate acid.

Coordinate Covalent Bond

A bond in which the pair of electrons is supplied by one of the two bonded atoms; also called a dative bond.

Coordination Compound

A neutral species containing one or more complex ions.

Coordination Number

In a crystal lattice it is defined as the number of atoms (or ions) surrounding an atom (or ion). In coordination compounds it is defined as the number of donor atoms surrounding the central metal atom in a complex.

Copolymerization

The formation of a polymer that contains two or more different monomers.

Corrosion

The deterioration of metals by an electrochemical process.

Coulomb’s Law

The potential energy between two ions is directly proportional to the product of their charges and inversely proportional to the distance of separation between them.

Covalent Bond

A bond in which two electrons are shared by two atoms.

Covalent Compounds

Compounds containing only covalent bonds.

Critical Mass

The minimum mass of fissionable material required to generate a self-sustaining nuclear chain reaction.

Critical Pressure

The minimum pressure necessary to bring about liquefaction at the critical temperature.

Critical Temperature

The temperature above which a gas will not liquefy.

Crystal Field Splitting

The energy difference between two sets of d orbitals in a metal atom when ligands are present.

Crystalline Solid

A solid that possesses rigid and long-range order; its atoms, molecules, or ions occupy specific positions.

Crystallization

The process in which dissolved solute comes out of solution and forms crystals.

Cyanides

Compounds containing the CN² ion.

Cycloalkanes

Alkanes whose carbon atoms are joined in rings.