P

peptide
A small polymer of amino acids, formed by the condensation copolymerization of several amino acids.

period
The horizontal rows in the periodic table.

pH
A measure of the amount of hydrogen ions in a solution, equal to the negative of the base-10 logarithm of the hydrogen ion concentration.

pharmacology
The science of drugs; the properties of drugs related to their therapeutic effects.

phentermine
Amphetamine-like component of fen-phen that increases metabolism by raising the body's levels of dopamine and norepinephrine.

photon
A particle of electromagnetic radiation having zero mass.



photosynthesis
Process in which water and carbon dioxide are combined in the presence of sunlight to produce glucose and oxygen.This is the process used by green plants to create their food.

phytoplankton
Algae, microscopic single-celled plants that float in the surface waters of the sea, lakes and rivers. In the ocean they constitute the bottom of the marine food chain. They have been called 'the pasture of the sea.' Like plants on land, they use sunlight to convert carbondioxide and water into sugars and oxygen in the process of photosynthesis.




phytoremediation
Using plants to clear toxic metals from the environment by chelation.

plasma
A gas-like phase of matter that contains charged particles.

polarizability
Indication of the ease of distortion of an electron cloud around at atom.Large atoms (like iodine) have many electrons, and their location may easily shift, producing regions of partial positive and negative charge.The larger the atom, the greater the polarizability, or the more easily an electron cloud may be distorted.

pollutant
A substance that contaminates an environment.

polycarbonate
A polymer in which the repeating unit is an organic carbonate [—R—O—C(O)—O—]n.

polymer
Molecules which are composed of linked repeating units (called monomers) are referred to as polymers. Polymers are the basis for many plastics and synthetic fibers such as Teflon and polyester.



porosity
The ratio of the size of a material's pores to the volume of the material's mass.

precipitate
A solid formed in a chemical reaction.

precision
The agreement of repeated measurements with each other.

precursor
In metabolism, a chemical substance from which another chemical substance is formed
pressure
The force per unit area.
protein
A biological polymer formed by condensation reactions among a set of 20 different amino acids.
proton
A positively charged subatomic particle found in the nucleus.
protonated
Having acquired an additional proton (H+).

Q

quanta
Plural of quantum.

quantum
The minimum energy change of an atom emitting or absorbing energy.

quartz
An abundant mineral consisting of silicon dioxide(SiO2) with a hardness of 7 on the Mohs' scale.

quench
Stopping a reaction quickly, first used to refer to harden steel by quickly putting red-hot steel into cold water.

quicklime
A common name for calcium oxide.

R

radiation
Energy emitted from some object.



radical
A species with an odd number of electrons; formerly called free radical.

radioactivity
The spontaneous emission of particles and/or energy from atomic nuclei.

radioisotope
Contraction for words "radioactive isotope" of an element.



reactant
A starting material in a chemical reaction.

reactivity
The degree to which a substance will respond to a stimulus or interact with another substance.

receptor
Protein molecules on the surface of cell membranes used for communication between cells.

recycling
To treat or process waste materials so as to make them suitable for reuse. The key to successful recycling of materials contained in refuse lies in the separation of recyclable components from the main bulk of the waste.

reducing
The gain of electrons by an atom, ion, or molecule.

reduction
A gain of electrons; a decrease in oxidation state.

refrigerant
A chemical used in refrigeration, to keep substances cool.



resistance
The opposition of a substance to the passage through it of a steady electric current.From Ohm's Law, R = E/I, the resistance equals the voltage of the cell divided by the current flow.

resonance structure
Possible structures of a molecule for which more than one electron-dot structure can be written, which differ in the bond pairs between atoms.

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S

saccharin
A compound, C7H5NO3S, that is several hundred times sweeter than can sugar and is used as a calorie-free sweetener.




salt
An ionic compound with a positive ion that comes from a base and a negative ion that comes from an acid.

silica
Silica is the common name for silicon dioxide, SiO2.It exists in nature as crystalline quartz.

smog
A fog containing fumes, or a photochemical haze caused by the action of ultraviolet radiation on hydrocarbons and NOx from automobile exhaust.


sol
A liquid colloidal dispersion; a fluid colloidal system in which solid particles are dispersed in a liquid colloidal solution.

solubility
The maximum amount of a substance that will dissolve in a given amount of solvent at a given temperature.

solute
The substance dissolved in a solution; substance present in a lesser amount in a solution.



solution
A homogeneous mixture of two or more substances.


solvent
The substance present in the largest amount in a solution; often the liquid component.

spectrometer
An instrument for measuring the emission or absorption of light of a particular wavelength.



spectroscopy
The science that deals with the use of the spectroscope and with spectrum analysis.A spectroscope is an optical device for producing and observing a spectrum of light or radiation from any source.


spin
The spin of an electron is designated by ms, the electron spin quantum number, which can have values of +1/2 and -1/2.In the presence of an external magnetic field an electron in an orbital can have one of two possible energy states, which depend on whether the magnetic field associated with the electron is aligned with or against the external magnetic field.

stereochemistry
The spatial arrangement of atoms in molecules or compounds and the relation of spatial arrangement to the substanceis properties.

stereoisomers
Two or more compounds with the same molecular formula and the same atom-to-atom arrangement, but with different arrangement of atoms in space. stereoisomeric (adjective)


steroids
Compounds containing a 17-carbon, four-ring system.


stoichiometry
The study of the quantitative relationships between reactants and products.


stratosphere
The layer of the earth's atmosphere that extends from roughly 7 miles (11 km) above the surface to 31 miles (50 km) above the surface.




sublimation
The direct conversion of a solid to a gas.

substituent
An atom or group that replaces another atom or group in a molecule.

superconductivity
A state in which the electrical resistance of a material is so low that it cannot be measured and appears to be zero.The superconducting state is also characterized by unusual magnetic properties.

supercritical
Above the critical point; above critical temperature or pressure.

supersaturated solution
A solution that temporarily contains more solute than the saturated amount at some temperature.



surface tension
The energy required to disrupt the surface of a liquid.

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T

taxol
A naturally occurring compound (extracted from the bark of the Pacific yew tree) that has been approved by the U.S. Food and Drug Administration (FDA) for treating advanced breast or ovarian cancers.




temperature
A measure of the average kinetic energy of a substance. Determines the direction of heat transfer.

teratogen
A substance that causes fetal abnormalities.

theory
A principle that explains a body of facts and the laws based on them.

thermodynamics
The study of energy and its transformation.



titration
A procedure for quantitative analysis by carrying out a reaction in solution by measurement of volumes using a reactant of known concentration.



torr
A unit of pressure equal to 1 mmHg or 1/760 of an atmosphere.

toxicity
The degree to which a substance is poisonous.

triad
A group of three elements whose chemical and physical properties aresomewhat related.

tritium
A rare isotope of hydrogen with one proton and two neutrons.

troposphere
The lowest part of the earth's atmosphere, extending from the surface of the planet to the bottom of the stratosphere.

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U

unit
A set magnitude of measurements used to express a certain type of physical quantity such as length, mass, and time. The SI units replaced previous used system of units for scientific purposes.


unsaturated
An organic compound with one or more double or triple covalent bonds between carbon atoms in each molecule.


unsaturated solution
A solution in which more solute can be dissolved at a given temperature.

V

vapor
Another name for a gas.

venting
Providing an opening for the discharge of gases or the relief of pressure.





viscosity
Resistance of a substance to flow.


volatile
A substance which is easily vaporized.

volatize
To make volatile; to cause to pass off in vapor.

volt
A unit of electrical potential.

volume
The space occupied by a mass.

vulcanization
The process for changing rubber from a weak material into a hard, strong material, usually by heating with sulfur.

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W

wavelength
The distance between any two identical points in consecutive cycles of a wave.Often measured from peak to peak or crest to crest. Symbolized by the Greek letter lambda.




weight
The measures of the earth's gravitational pull on a object.

X

X ray
Electromagnetic radiation of high frequency and short wavelength (ranging from 10-11 to 10-9 meters).




X-ray crystallography
A technique of determining a molecule's three-dimensional structure by analyzing the X-ray diffraction patterns of crystals made up of the molecule in question.

Y

yellow
A color.

yoctomole (ymol)
10-24 moles; A single molecule corresponds to 1/Avogadro's number, or 1.66 X 10-24 moles, or 1.66 ymol.

Z

zeolite
A natural or synthetic hydrated aluminosilicate with an open three-dimensional crystal structure which water molecules are held in cavities in the lattice. They are used to soften water.

zwitterion
An ion that has a positive and negative charge on the same group of atoms. It is also called dipolar ion.



zymogen
An inactive biomolecule that is a precursor to an enzyme.

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