Glossary of Chemistry

A

achiral
Describes any molecule or object that is superimposable upon its mirror image.

acid
A compound that produces hydrogen ions in water solution.

acidification
The process of increasing the hydrogen ion concentration.

adsorption
The concentration of a substance on the surface of another substance, which is usually solid.

aerobic
Living or active only in the presence of oxygen.

aerogel
A porous solid formed by replacing the liquid in a gel with a gas; what remains when the liquid part of an alcogel is removed without damaging the solid part.

alcogel
A gel formed by the coagulation of a sol in which the liquid is alcohol; at the gel point, the mixture forms a rigid substance that can stand on its own. The liquid and solid parts of an alcogel occupy the same volume.

alcohol
A class of organic compounds which has an OH group covalently bonded to a carbon atom.

alkaline
Describes an alkali (basic) or a solution that has excess of hydroxide ions.

alkane
A saturated hydrocarbon with the general formula CnH2n+2.

alkylated
A molecule that has attached to it an alkyl group (derived from an alkane — CnH2n+2), which is a saturated hydrocarbon with a single bond available.

allotrope (allotropic form)
Different bonding arrangements allowing for different forms of matter to be made from a single type of atom. Different forms of matter made in this way are called allotropes. For example, ozone (O3) and dioxygen (O2) are allotropes of the element oxygen. Also, diamond, buckyball, and graphite are allotropes of carbon.

amalgam
An alloy of mercury with another metal, often used as a dental filling.

amide
an organic functional group that has the following structure:



amphetamines
Any of the compounds which are substituted or slightly modified amphetamine molecules.

amphoteric
A compound that can act as a base and an acid.

anabolism
Metabolic synthesis of proteins, fats and other constituents of living organisms from molecules or simple precursors, which usually requires an input of energy.

anesthetic
A substance that produces loss of sensation, sometimes with loss of consciousness as well.

angstrom
A unit of length equal to 1 x 10-8 cm or .1 nanometer. It was named after A. J. Angstrom (1814-1874), a Swedish spectroscopist.

anion
A negative ion.

anode
A positive electrode; the electrode toward which electrons flow; the electrode at which oxidation occurs.

anthropogenic
Resulting from the actions and influence of human beings.

antiaromaticity
The unusual instability that results from a continuous cyclic system of 4n pi electrons (where n is any integer).

antimatter
Any subatomic particle identical in mass to a proton, neutron, or electron, but with the opposite charge.For example, a positron is a positive electron.A collision between a particle and its respective antiparticle results in both being annihilated, with their masses converted to photons of equivalent energy.

antisense
Having a sequence complementary to a segment of genetic material and serving to inhibit gene function.

aquifer
Water bearer. Earth materials that contain ground water and through which ground water may flow freely. Some examples of these include sand, porous sandstone, and gravel. Aquifers vary widely in their ability to hold water and the speed at which water flows through them.

aromaticity
The unusual stability that results from a continuous cyclic system of 4n + 2 (where n is any integer) pi-electrons in a cyclic compound. This stability results from complete filling of bonding pi molecular orbitals.

asteroid
Any of the thousands of small bodies that revolve about the sun in orbits lying mostly between those of Mars and Jupiter. Also known as a minor planet.

atherosclerosis
A disease of the arterial walls characterized by fatty deposits and abnormal tissue growth.

atmosphere
Unit of pressure equal to 101325 pascals or 760mmHg. Its symbol is atm.

atom
The smallest unit of an element which has all the properties of the element. It is composed of protons, neutrons and electrons.

autoclave
An airtight chamber use for processes requiring dry temperatures above 212 degrees F.

Avogadro's number
The number of particles present in 1 mole of a substance, experimentally determined to be 6.02 x 1023.

B

balance
n. Any piece of apparatus used to determine the mass of a sample of matter.v. as in balance an equation: to have equal numbers of atoms of each element on the opposite sides of an equation.


base
A compound that produces hydroxide ions in water solution.


battery
An electrochemical cell that can be used as a source of direct current at a constant voltage.



binge drinking
The consumption of five or more drinks in a row on at least one occasion.

biochemistry
The science that makes use of chemistry to learn about and explain biologically important systems.

biomethylation
Becoming methylated through biological action; for example, bacteria can generate methylated mercury in aquatic sediments.


blood alcohol level
blood alcohol content
The amount of alcohol in a person's bloodstream measured in percentages. Abbreviated BAL or BAC.


bond
A force which holds together two atoms, two ions, two molecules, or a combination of these.

brine
Water saturated with salt; a strongly saline solution.

Bunsen burner
Common laboratory burner that uses natural gas or propane, developed by German chemist Robert Wilhelm Bunsen during the 19th century.

C

calorie
The amount of energy needed to raise the temperature of 1 gram of water by 1 degree Celsius.

calorimeter
Any one of a number of devices used for measuring the heat content.




carbocyclic
Being or having an organic ring of carbon atoms.

carbohydrate
An organic compound with the general formula Cx(H2O)y.

carcinogen
A cancer-causing agent.

catalysis
A process in which a catalyst increases the speed of a chemical reaction.

catalyst
A substance which increases the rate of a chemical reaction, but itself remains unchanged at the end of the reaction.

cathode
A negative electrode.It is the electrode from which current leaves an electrolytic cell.




cation
A positively charged ion.

caustic
Corrosive; able to eat away or destroy by chemical action.

chelated
Combined with a metal to form a chelate ring, in which a metal ion is held by coordinate bonds.

chiral
Relating to a molecule that cannot be superimposed on its mirror image.

chlorofluorocarbons
Synthetic compounds containing carbon, chlorine, fluorine, and sometimes hydrogen that are used in refrigerants, propellants, the manufacture of foams, and cleaning solvents.

chlorophyll
The catalytic substance in photosynthesis that contains a Mg2+ ion inthe center of a specialized ring structure known as a porphyrin.Porphyrins have a central portion containing nitrogen atoms that canattach to a metal ion.


chromatography
Any process for separating materials using two phases, one stationary, and one moving.One example: gas chromatography (gas as moving phase, solid as stationary phase).

colloid
A substance consisting of particles dispersed throughout another substance.

combustion
Rapid oxidation (burning) accompanied by the release of heat.

composting
The controlled biological decomposition of organic solid wastes under aerobic (in the presence of oxygen) conditions.Organic materials are transformed into soil enhancers such as humus and mulch.

condensation
The process of vapor molecules forming a liquid.




couples
A half-reaction which explicitly shows electron transfer

covalent bond
Bonds that hold atoms together by the sharing of electrons.

covalent radius
Value assigned to an atom such that the sum of the covalent radii of atoms A and B is (approximately) the A-B bond length.

critical pressure
The lowest pressure required to transform a gas into a liquid at the critical temperature.

critical temperature
One of three parameters (critical pressure and critical molar volume being the other two) defining the point at which random thermal molecular motion become so violent that attractive forces are unable to bring about condensation even when the molecules are squeezed together; a temperature above which a vapor cannot be turned into a liquid no matter how much pressure is applied.

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D

dehydration
A reaction in which the elements that make up water (twice as many hydrogen as oxygen atoms) are removed from an organic compound.

density
The ratio of mass to volume.

deprotonation
Losing a proton (H+).

detergent
A substance used for removing dirt. Detergents differ from soaps in that detergents are compounds that are derived from sulfur-containing organic acids.

deuterium
The isotope of hydrogen that has one neutron.

dextrorotatory
Able to rotate plane-polarized light in a clockwise fashion.

diffusion
The gradual mixing of the molecules of 2 or more substances by random molecular motion.

dilute
A solution that contains a relatively small amount of solute dissolved in a fixed amount of solvent.

dimer
A molecule or compound formed by the combination of two identical simple molecules.

dipole
Produced from an unequal sharing of electrons in a molecule in which there will be a region of partial positive charge and a separate region of partial negative charge.

dissociation
In an aqueous solution, the separation of a compound into ions.

distillation
The process used to separate two or more liquids that have different boiling points.

dopamine
One of many neurotransmitters that is essential in the functioning of the central nervous system and is often considered to be the primary reward neurotransmitter in the brain. It is the precursor to norepinephrine.

doping
Using banned or illegal natural or synthetic chemicals to enhance athletic performance.

dose
The measured quantity of a substance, such as a drug, taken at one time.

drawdown
The the act, process, or result of depleting, as in the drawdown of oil reserves.

ductile
The ability of a substance to be drawn out to form a thin wire.

dye
A substance used to give color to cloth, plastics, paper, or other materials.Dye may be made from plants or by synthetic chemical reactions.

dynamic equilibrium
The condition in which the rate of a forward process is exactly the same as the rate of a reverse process.

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E

efficiency
The ratio of work done or energy developed by a machine or engine, to the energy supplied to it.

electrochemical
Describes any effect concerned with the electrical properties of solutions and the ions in solutions.




electrode
A metal plate or wire for conducting electrons into or out of solutions.

electrolysis
The use of electrical energy to carry out a chemical reaction.

electrolyte
A substance that, when dissolved in water produces a solution that conducts electricity.

electron
A negatively charged subatomic particle, of extremely low mass found in the space outside the nucleus of an atom.


electronegative
Referring to the property of electronegativity.The most electronegative element isfluorine, having an electronegativity of 4.0 on the Pauling scale.Non-metals are more electronegative than metals.

electronegativity
The ability of an atom in a molecule to attract electrons toward itself.

electrophoresis
A method of separating large molecules (such as DNA fragments or proteins) from a mixture of similar molecules. An electric current is passed through a medium containing the mixture, and each kind of molecule travels through the medium at a different rate, depending on its electrical charge and size. Separation is based on these differences.

electrostatic
Having to do with the positive and negative charges on species such as electrons or ions.The important principle is that like charges repel and opposite charges attract.




element
A basic building block of matter that cannot be broken down into a simpler substance by ordinary means.


emollient
A substance that softens or smoothes.


emulsifier
A substance that promotes the dispersion of small globules of one liquid in another liquid when the two liquids will not mix.


enantiomer
One of a pair of non-superimposable, mirror-image stereoisomers.

energy
The ability to do work and transfer heat.

entropy
A measure of the disorder of a system.

enzymatic
Relating to the activity of enzymes, which are biological catalysts that play crucial roles in most biological processes, including metabolism and gene expression.

enzyme
A biological catalyst that will increase the rate of a chemical reaction, but is not consumed in the course of a reaction.These catalysts are at least hundreds of times more efficient than any man-made catalyst used in industrial processes.

epimer
One of two steroisomers with more than one chiral center that differ in stereochemical configuration at only one.

equilibrium
A system in which the rates of the forward and the reverse reaction are equal.

excretion
The process of ridding the body of metabolic waste products.

exergonic process
A process that liberates energy.

exothermic process
A thermodynamic process in which heat flows from a system to the surroundings.

extensive property
A property that depends on the amount of matter present.

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F

family (of elements)
Elements found in the same column of the periodic table, also known as a group of elements.These elements will have similar properties.


fat
A solid ester of a long-chain carboxylic acid with glycerol.

fenfluramine
Amphetamine-like component of fen-phen that suppresses appetite by increasing seratonin levels in the brain.

filter
To separate an insoluble solid from a liquid by pour it through a solid (usually paper) to trap the solid particles and separate them from the liquid.


fission
The process in which heavy nuclei split to form lighter nuclei.


fluorescence
forensic Relating to the application of scientific knowledge to legal problems.

formula
A shorthand way of showing the composition of a substance with the use of symbols and numerical subscripts.

freezing
The change of phase from a liquid into a solid.

frequency
The number of complete waves passing a point in space in a given amount of time.

fuel
A material that can be burned to provide a source of energy.

fumigant
A gaseous substance used to disinfect an object or to destroy pests.

fungicides
A chemical that kills fungi or prevents them from growing.

fusion
The joining of two small nuclei to form a larger nucleus.

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G

galvanize
The process of covering iron with a coat of zinc to make it less reactive to air and water.

galvanometer
A device that is very sensitive and able to detect even small flows of electrons through a wire.




gas
The least dense state of matter.

gas chromatography
An analytical chemistry technique in which a sample is vaporized and passed through a column whose walls are covered with a sticky organic solvent; different chemicals in the sample have different affinities for the solvent and separate as they pass through the column.




gasohol
A mixture of 90% gasoline and 10% ethyl alcohol that is used as an automotive fuel.


gasoline
A volatile, flammable, liquid mixture of hydrocarbons, obtained from petroleum, and used as fuel for internal-combustion engines.


gel
A colloid in which the dispersed phase has combined with the continuous phase to produce a semisolid material as a jelly; a colloid formed by coagulation of a sol.


gene
The fundamental physical and functional unit of heredity. A gene is an ordered sequence of nucleotides located in a particular position on a particular chromosome that encodes a specific functional product (i.e., a protein or RNA molecule).


glucose
A 6-carbon sugar that plays a major role in cell metabolism.

glycogen
A polysaccharide the body uses for energy storage; it is made up of chains of glucose molecules. When the body has depleted the free glucose in the blood, the liver breaks down glycogen into more glucose.




glycolipid
A lipid covalently linked to a sugar or polysaccharide. These biomolecules are important parts of animal cell membranes.


glycolysis
A complex biochemical process in which one molecule of glucose is anaerobically converted into two molecules of pyruvate and energy in the form of ATP.


gram
The basic unit of mass in the metric system.

graphite
The most stable allotrope, or form of carbon, having a hexagonal type linking of atoms with relatively strong bonds to 3 neighboring carbon atoms, and a much weaker bond to a fourth carbon atom.


group
A vertical column in the periodic table.

H

half-cell
An oxidation or reduction reaction that occurs at an electrode.Two half-cells must be combined to form an electrochemical cell.


half-life
The time required for concentration of one substance to reach half of its initial value.The time it takes for one half of a substance to be metabolized and/or excreted from the body.


half-reaction
A reaction that shows the electrons involved in an oxidation or reduction step of a reaction.




halide
A negatively charged ion of the group VIIA elements.

halogen
The group VIIa elements in the periodic table.

heat
The transfer of (thermal) energy between two objects that are at different temperatures.

Henry's Law
The amount of gas dissolved in a solution is directly proportional to the pressure of the gas above the solution.

heterocycle
A compound containing at least one ring that consists of both carbon and non-carbon atoms .


heterogeneous
Describes a material or substance or chemical reaction which is not the same throughout in its properties, composition, or state of matter.


homeopathy
A system of disease treatment involving application of minute doses of a remedy that, in a healthy person, would produce symptoms of the disease.

homogeneous
Describes a material or substance or chemical reaction which is the same throughout in its properties, composition, or state of matter.

hybridization
A mixing process, often applied to description of atomic orbitals, producing orbitals that have characteristics intermediate between the various types of orbitals involved.

hydrate
A crystalline solid with molecules of water trapped in the solid state structure, which can often be removed partly or completely by relatively gentle heating.

hydration
Having solvent molecules of water surrounding and becoming attached to ions or molecules of the solute.

hydrocarbon
An organic compound containing only the elements hydrogen and carbon.

hydrolysis
Cleavage of a covalent bond brought about by water; the H- and -OH of water typically become attached to the respective cleavage fragments.For example:






hydrolyze
To add hydrogen or hydroxyl to a substance.


hypothesis
A scientific "hunch," a tentative explanation of or prediction derived from experimentation.

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I

immiscible
Two liquids that do not dissolve in each other.




incineration
Burning of wastes under controlled high temperatures and oxygen levels that results in their complete combustion; not the same as burning leaves in the back yard or wood in the fireplace.


indicator
A substance used to indicate the end point of a titration by a change in color.


inhibitor
A substance that retards the rate of a chemical reaction.


intercalation
The binding of a molecule between adjacent base pairs in DNA.



intermolecular
Between molecules.Intermolecular forces are those forces between molecules.

intramolecular
Refers to a characteristic within one molecule or ion, referring only to the atoms in the molecular or ion.

inverse relationship or proportion
When one quantity decreases as a result of the other increasing or vice versa. For example, density is inversely related to volume for constant mass.

ion
An electrically charged particle formed by the gain or loss of electrons.

ion-exchanger
A resin capable of removing unwanted ions and replacing them with more desirable ones.For example, Ca2+ or Mg2+, which interfere with the action of soap or detergent can be replaced by Na+, which does not.

isomers
Compounds with the same molecular formulas but different arrangements of atoms.

isotopes
Atoms of the same element with differing numbers of neutrons.

J

joule
Unit of energy.

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K

Kelvin
The temperature scale that begins with absolute zero as 0 K.



ketone
An organic compound containing a carbonyl group bonded to two carbon atoms.

ketose
A simple sugar that has the reactions of a ketone.



kilo-
Prefix meaning 1000.

kilogram
Base unit for mass in metric system.

kinetic energy
The energy something possesses due to its motion, depending on mass and velocity.




kinetic-molecular theory
A theory of the behavior of matter.

L

Lanthanides
The series of f-block elements between lanthanum and hafnium.

laser
Acronym for light amplification by stimulated emission of radiation.A laser is an intense source of light with a very narrow range of wavelengths. The intense light is given off when many ions are stimulated and simultaneously emit a photon at the same wavelength.

lattice
A regular arrangement of points in space in 3 dimensions.

law
Mathematical statement of a relationship that is always the same.

leachate
The solution produced by passing a liquid through a solid, often containing chemicals that have dissolved from the solid to the liquid. As rainwater passes through landfills and associated sediments, various chemical substances may dissolve in the water and penetrate the aquifer and contaminate ground water.




levorotatory
Able to rotate plane-polarized light in a counterclockwise fashion.

ligand
A molecule or ion bonded to a central metal atom or ion in a coordination compound.



limewater
Common name for a solution of calcium hydroxide.

lipid
A fatty, waxy or oily non-polar organic compound that is characteristically insoluble in water but readily soluble in organic solvents.

liquid
The phase of matter in which a substance has a definite volume but no definite shape.

liter
Unit of volume in the metric system, slightly larger than 1 quart, since 1 liter is 33.2 ounces, or 1 quart is 0.946 liters, to three significant figures.

litmus
Plant pigment commonly used as an acid base indicator.Litmus is red (or pink) in an acid, and blue in a base.



lye
Common name for solution of sodium hydroxide.

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M

macromolecule
Name given to a very large, and in most cases biologically important molecule.Molar mass certain to be in the thousands of grams, at least.

manometer
Device used for measuring small pressures.



matter
Anything that has mass and takes up space.

meniscus
Curved surface of a liquid in a container.

metabolite
A chemical product of metabolism.

metal
An element that tends to lose electrons, forming positive ions, and is a good electrical conductor.

metalloid
An element with properties intermediate between metals and non-metals.

meteorite
A mass of stone or metal that has reached the earth from outer space.

meter
Unit of length in the metric system, slightly longer than 1 yard or 36 inches.

methanogenic
"Methane (CH4) producing"; methanogenic bacteria use hydrogen and carbon dioxide as energy sources and produce methane and water as a result.



methylated
Having a methyl group (CH3).

micromolar
Approximately 1x10-6 moles/liter.

microscopic
Seeing the situation at the particle level: atoms, molecules, or ions.

mitochondrion
A membrane-bound organelle that carries out oxidative phosphorylation and produces most of the ATP in eucaryotic cells.

mixture
A grouping together of two or more substances in which each retains its original properties.

molality
The molal concentration, moles of solute per kilogram of solvent, usually given the symbol m.

molarity
The number of moles of solute per liter of aqueous solution.

mole
The amount of substance that contains the same number of elementary particles as are found in exactly 12 g of carbon-12.

molecule
The smallest unit of a compound that has all the properties of the compound.



monomer
A molecule or substance which can be polymerized, usually of low molar mass.

monooxygenase
An enzyme catalyzing the incorporation of one atom from molecular oxygen into a compound and the reduction of the other atom of oxygen to water.

monosaccharide
A simple sugar most commonly having 5 or 6 carbon atoms present which cannot be hydrolyzed to simpler sugars.

N

nano-
Prefix meaning one billionth or 10-9.

neurotransmitter
A substance that transmits nerve impulses across a synapse.

neutralization
A process where an acid and a base react with each other to form a salt and water.



neutron
Electrically neutral subatomic particle found in the nucleus.

NIMBY
Acronym for Not In My Back Yard.An expression describing the response from members of a community who disapprove of proposed sites for solid waste disposal. A milder form of NOPE (Not On Planet Earth).

nitrogenase
An enzyme system that catalyzes the reaction of molecular nitrogen (N2) to ammonia (NH3).

nitrosamines
A group of organic compounds with the basic structure NNO, some of which are powerful cancer-causing chemicals.

nomenclature
The systematic naming of chemical compounds.

non-electrolyte
A substance that dissolves in water to form a solution that is non-conducting.

nonpolar
Having no poles.Used to refer to a bond or molecule that overall has no separation of electrical charge.

norepinephrine
A neurotransmitter that increases heart rate, blood pressure, and is related to increased motor activity. It is the precursor to epinephrine.



normality
A concentration unit relating equivalents of solute to one liter of aqueous solution.

nuclear
Of or pertaining to nucleus.

nucleon
A particle found in the nucleus, that is, a proton or a neutron.

nucleoside
A biologically important molecule consisting of an amine-containing purine or pyrimidine base joined to ribose, a 5-carbon sugar.

nucleus
The central part of an atom containing protons and neutrons.

nutrient
A source of nourishment, expecially a nourishing ingredient in food.

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O

octet
A stable group of eight electrons in the outer shell of an atom.

ohm
The unit of electrical resistance.A current of 1 amp at a potential difference of 1 volt experiences 1 ohm of resistance.

oligomer
A molecule that consists of repeating molecular subunits--essentially a polymer but not as long. By analogy, if a yellow brick is a single subunit, the yellow brick road is a polymer, and the yellow brick driveway is an oligomer.

orbital
A region of space where there is a high probability of finding an electron in an atom or ion.




osmosis
The movement of solvent molecules through a membrane from region of lower solute concentration to a region of higher solute concentration.

oxidation
A process in which an electron is lost by an atom, molecule or ion.

oxygenates
Liquid organic compounds that can be blended into gasoline to increase its oxygen content; during combustion, this additional oxygen reduces the output of CO and may reduce emissions of ozone-forming materials. The two major oxygenates in use today are ethanol and MTBE.

ozone
The allotrope of oxygen that contains 3 atoms in one molecule, the formula for ozone being O3.



ozone layer
An atmosphere layer at about 20 to 30 miles high (32 to 48 km), normally characterized by high ozone content, which blocks most solar UV radiation from entering the lower atmosphere.

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