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AllChemicals.info - Chemical glossary Category: Sciences > Chemical Date & country: 10/12/2007, UK Words: 611

Chain Termination Step
The combination of two radicals, which removes the reactive species that propagate the change reaction.

Charle's Law
At constant pressure the volume occupied by a definite mass of gas is directly proportional to its absolute temperature.

Chemical Bonds
The attractive forces that hold atoms together in elements or compounds.

Chemical Change
A change in which one or more new substances are formed

Chemical Equation
Description of a chemical reaction by placing the formulas of the reactants on the left and the formulas of products on the right of an arrow.

Chemical Equilibrium
A state of dynamic balance in which the rates of forward and reverse reactions are equal, there is no net change in concentrations of reactants or products while a system is at equilibrium.

Chemical Hygiene Officer (CHO)
A person or employee who is qualified by training or experience to provide technical guidance in the development and implementations of the provisions of a Chemical Hygiene Plan (CHP)

Chemical Hygiene Plan (CHP)
A written program developed and implemented by an employer designating proceedures, equipment, personal protective equipment, and work practices that are capable of protecting employees from the health hazards presented by hazardous chemicals usid in that particular workplace.

Chemical Kinetics
The study of rates and mechanisms of chemical reactions and of the factors on which they depend.

Chemical Periodicity
The variations in properties of elements with their position in the periodic table.

Cis-
The prefix used to indicate that groups are located on the same side of a bon about which rotation is restricted.

Cis-Trans Isomerism
A type of geometrical isomerism related to the angles between like ligands.

Clay
A class of silicate and aluminosilicate minerals with sheet-like structures that have enormous surface areas that can absorb large amounts of water.

Cloud Chamber
A device for observing the paths of speeding particiles as vapor molecules condense on them to form foglike tracks.

Coefficient of expansion
The ratio of the change in length or volumen of a body to the original lengthor volume for a unit change in temperature.

Cohesive Forces
All the forces of attraction among particles of a liquid.

Coke
An impure form of carbon obtained by destructive distillation of coal or petroleum.

Colligative Properties
Physical properties of solutions that depend upon the number but not the kind of solute particles present.

Collision Theory
Theory of reaction rates that states that effective collisions between reactant molecules must occur in order for the reaction to occur.

Colloid
A heterogeneous mixture in which solute-like particles do not settle out.

Combination Reaction
Reaction in which two substances ( elements or compounds ) combine to form one compound.

Combustible
Classification of liquid substances that will burn on the basis of flash points. A combustible liquid means any liquid having a flash point at or above 37.8°C (100°F) but below 93.3°C (200°F), except any mixture having components with flash points of 93.3°C (200°F) or higher, the total of which makes up 99 percent or more of the total volume of the…

Common Ion Effect
Suppression of ionization of a weak electrolyte by the presence in the same solution of a strong electrolyte containing one of the same ions as the weak electrolyte.

Complex Ions
Ions resulting from the formation of coordinate covalent bonds between simple ions and other ions or molecules.

Composition Stoichiometry
Descibes the quantitative (mass) relationships among elements in compounds.

Compound
A substance of two or more elements in fixed proportions. Compounds can be decomposed into their constituent elements.

Compressed Gas
A gas or mixture of gases having, in a container an absolute pressure exceeding 40 psi at 21.1°C (70°F) A gass or mixture having in a container, an absolute pressure exceeding 104 psi at 54.4°C (130°F) regardless of the pressure at (21.1°C (70°F) A liquid having a vapour pressure exceeding 40 psi at 37.8°C (70°F) as determined by ASTM D-323-72.

Concentration
Amount of solute per unit volume or mass of solvent or of solution.

Condensation
Liquefaction of vapor.

Condensed Phases
The liquid and solid phases, phases in which particles interact strongly.

Condensed States
The solid and liquid states.

Conduction Band
A partially filled band or a band of vacant energy levels just higher in energy than a filled band, a band within which, or into which, electrons must be promoted to allow electrical conduction to occur in a solid.

Conformations
Structures of a compound that differ by the extent of rotation about a single bond.

Conjugate Acid-base Pair
In Bronsted-Lowry terminology, a reactant and product that differ by a proton, H+.

Conjugated Double Bonds
Double bonds that are separated from each other by one single bond -C=C-C=C-.

Contact Process
Industrial process by which sulfur trioxide and sulfuric acid are produced from sulfur dioxide.

Continuous Spectrum
Spectrum that contains all wave-lengths in a specified region of the electromagnetic spectrum.

Control Rods
Rods of materials such as cadmium or boron steel that act as neutron obsorbers (not merely moderaters) used in nuclear reactors to control neutron fluxes and therfore rates of fission.

Coordinate Covalent Bond
A covalent bond in which both shared electrons are donated by the same atom, a bond between a Lewis base and a Lewis acid.

Coordinate Covalent Bond
Covalent bond in which both shared electrons are furnished by the same species, bond between a Lewis acid and Lewis base.

Coordination Compound or Complex
A compound containing coordinate covalent bonds.

Coordination Isomers
Isomers involving exchanges of ligands between complex cation and complex anion of the same compound.

Coordination Number
In describing crystals, the number of nearest neighbours of an atom or ion.The number of donor atoms coordinated to a metal.

Coordination Sphere
The metal ion and its coordinating ligands but not any uncoordinated counter-ions.

Copper
Discovered : known to ancient civilisationsOrigin : The name is derived from 'Cuprum', the Latin name for Cyprus.Description :A reddish-gold metal that is easily worked and drawn into wire. It has great ability to conduct both heat and electricity. Traditionally it has been one of the coinage metals along with silver and gold, but it is the most co…

Corrosion
Oxidation of metals in the presence of air and moisture.

Coulomb
Unit of electrical charge.

Coulometry
The quantitative application of Faraday's Law to the analysis of materials. The current and time are the usual variables measured.

Covalent Bond
Chemical bond formed by the sharing of one or more electron pairs between two atoms.

Covalent Compounds
Compounds containing predominantly covalent bonds.

Critical Mass
The minimum mass of a particular fissionable nuclide in a given volume required to sustain a nuclear chain reaction.

Critical Point
The combination of critical temperature and critical pressure of a substance.

Critical Pressure
The pressure required to liquefy a gas (vapor) at its critical temperature.

Critical Temperature
The temperature above which a gas cannot be liquefied, the temperature above which a substance cannot exhibit distinct gas and liquid phases.

Crystal Field Stabilization Energy
A measure of the net energy of stabilization gained by a metal ion's nonbonding d electrons as a result of complex formation.

Crystal Field Theory
Theory of bonding in transition metal complexes in which ligands and metal ions are treated as point charges, a purely ionic model, ligand point charges represent the crystal (electrical) field perturbing the metal?s d orbitals containing nonbonding electrons.

Crystal Lattice
A pattern of arrangement of particles in a crystal.

Crystal Lattice Energy
Amount of energy that holds a crystal together, the energy change when a mole of solid is formed from its constituent molecules or ions (for ionic compounds) in their gaseous state.The energy charge when one mole of formula units of a crystalline solid is formed from its ions, atoms, or molecules in the gas phase, always negative.

Crystalline Solid
A solid characterized by a regular, ordered arrangement of particles.

Curie (Ci)
The basic unit used to describe the intensity of radioactivity in a sample of material. One curie equals 37 billion disintegrations per second or approximately the amount of radioactivty given off by 1 gram of radium.

Cyclotron
A device for accelerating charged particles along a spiral path.

D -Transition elements (metals)
B Group elements except IIB in the periodic table, sometimes called simply transition elements EX. Fe, Ni, Cu, Ti .For further information see Metals

D-Orbitals
Beginning in the third energy level, aset of five degenerate orbitals per energy level, higher in energy than s and p orbitals of the same energy level.

Debye
The unit used to express dipole moments.

Degenerate
Of the same energy.

Delocalization
Of electrons, refers to bonding electrons that are distributed among more than two atoms that are bonded together, occurs in species that exhibit resonance.The formation of a set of molecular orbitals that extend over more than two atoms, important in species that valence bond theory describes in terms of resonance.

Denaturation
A process pertaining to a change in structure of a protein form regular to irregular arrangement of the polypeptide chains.

Denatured
A commercial term used to describe ethanol that has been rendered unfit for human consumption because of the addition of harmful ingredients to make it sales tax-expempt.

Density
Density is the ratio b/w Mass and Volume: D=M/V

Deposition
The direct solidification of a vapor by cooling, the reverse of sublimation.

Derivative
A compound that can be imagined to arise from a partent compound by replacement of one atom with another atom or group of atoms. Used extensively in orgainic chemistry to assist in identifying compounds.

Dermal toxicity
Adverse health effects resulting from skin exposure ot a substance.

Designated area
An area that may be used for work with carcinogens, reproductive toxins, or substances that have a high degree of acute toxicity. A designated area may be the entire laboratory, an area of a laboratory, or a device such as a loboratory hood.

Detergent
A soap-like emulsifer that contains a sulfate, SO₃ or a phosphate group instead of a carboxylate group.

Deuterium
An isotope of hydrogen whose atoms are twice as massive as ordinary hydrogen,deuterion atoms contain both a proton and a neutron in the nucleus.

Dextrorotatory
Refers to an optically active substance that rotates the plane of plane polarized light clockwise, also called dextro.

Diagonal Similarities
Refers to chemical similarities in the Periodic Table of elements of Period 2 to elements of Period 3 one group to the right, especially evident toward the left of the periodic table.

Diamagnetism
Weak repulsion by a magnetic field.

Differential Thermal Analysis (DTA)
A technique for observing the temperature, direction, and magnitude of thermally induced transitions in a material by heating/cooling a sample and comparing its temperature with that of an inert reference material under similar conditions.

Differential Thermometer
A thermometer used for accurate measurement of very small changes in temperature.

Dilution
Process of reducing the concentration of a solute in solution, usually simply by mixing with more solvent.

Dimer
Molecule formed by combination of two smaller (identical) molecules.

Dipole
Refers to the separation of charge between two covalently bonded atoms

Dipole Moment
The product of the distance separating opposite charges of equal magnitude of the charge, a measure of the polarity of a bond or molecule, a measured dipole moment refers to the dipole moment of an entire molecule.

Dipole-dipole Interactions
Attractive interactions between polar molecules, that is, between molecules with permanent dipoles.

Dispersed Phase
The solute-like species in a colloid.

Dispersing Medium
The solvent-like phase in a colloid.

Displacement Reactions
Reactions in which one element displaces another from a compound.

Disproportionation Reactions
Redox reactions in which the oxidizing agent and the reducing agent are the same species.

Dissociation
In aqueous solution, the process in which a solid ionic compound separates into its ions.

Dissociation Constant
Equilibrium constant that applies to the dissociation of a comples ion into a simple ion and coordinating species (ligands).

Distilland
The material in a distillation apparatus that is to be distilled.

Distillate
The material in a distillation apparatus that is collected in the receiver.

Distillation
The separation of a liquid mixture into its components on the basis of differences in boiling points.The process in which components of a mixture are separated by boiling away the more volitile liquid.

Domain
A cluster of atoms in a ferromagnetic substance, all of which align in the same direction in the presence of an external magnetic field.

Donor Atom
A ligand atom whose electrons are shared with a Lewis acid.

Dosimeter
A small, calibrated electroscope worn by laboratory personnel and designated to detect and measure incident ionizing radiation or chemical exposure.

Double Bond
Covalent bond resulting from the sharing of four electrons (two pairs) between two atoms.

Double Salt
Solid consisting of two co-crystallized salts.

Doublet
Two peaks or bands of about equal intensity appearing close together on a spectrogram.