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Acid a substance that produces hydrogen
ions in solution; a proton donor.
Acid-base indicator a substance that
marks the end point of an acid-base titration by changing
color.
Acid rain rainwater with an acidic
pH, a result of air pollution by sulfur dioxide.
Acidic oxide a covalent oxide that
dissolves in water to give an acidic solution.
Actinide series a group of fourteen
elements following actinium in the periodic table, in which
the 5f orbitals are being filled.
Activation energy the threshold energy
that must be overcome to produce a chemical reaction.
Air pollution contamination of the
atmosphere, mainly by the gaseous products of transportation
and the production of electricity.
Alcohol an organic compound in which
the hydroxyl group is a substituent on a hydrocarbon.
Aldehyde an organic compound containing
the carbonyl group bonded to at least one hydrogen atom.
Alkali metal a Group I metal.
Alkaline earth metal a Group 2 metal.
Alkane a saturated hydrocarbon with
the general formula CnH2n.
Alkene an unsaturated hydrocarbon containing
a carbon- carbon double bond.
Alkyne an unsaturated hydrocarbon containing
a carbon- carbon triple bond.
Alloy a substance that contains a mixture
of elements and has metallic properties.
Alloy steel a form of steel containing
carbon plus metals such as chromium, cobalt, manganese, and
molybdenum.
Alpha particle a helium nucleus.
Alpha-particle production a common
mode of decay for radioactive nuclides in which the mass number
changes.
Amine an organic base derived from
ammonia in which one or more of the hydrogen atoms are replaced
by organic groups.
a-Amino acid an organic acid in which
an amino group and an R group are attached to the carbon atom
next to the carboxyl group.
Ampere the unit of measurement for
electric current; 1ampere is equal to 1coulomb of charge per
second.
Amphoteric substance a substance that
can behave either as an acid or as a base.
Anion a negative ion.
Anode in a galvanic cell, the electrode
at which oxidation occurs.
Aqueous solution a solution in which
water is the dissolving medium, or solvent.
Aromatic hydrocarbon one of a special
class of cyclic ung that acids produce hysaturated hydrocarbons,
the simplest of which is benzene.
Arrhenius concept a concept postulatindrogen
ions in aqueous solution, whereas bases produce hydroxide
ions.
Atmosphere the mixture of gases that
surrounds the earth's surface.
Atom the fundamental unit of which
elements are composed.
Atomic number the number of protons
in the nucleus of an atom; each element has a unique atomic
number.
Atomic radius half the distance between
the atomic nuclei in a molecule consisting of identical atoms.
Atomic solid a solid that contains
atoms at the lattice points.
Atomic weight the weighted average
mass of the atoms in a naturally occurring element.
Aufbau principle a principle staling
that as protons are added one by one to the nucleus to build
up the elements, electrons are similarly added to hydrogen-like
orbitals.
Autoionization the transfer of a proton
from one molecule to another of the same substance.
Avogadro's law equal volumes of gases
at the same temperature and pressure contain the same number
of particles (atoms or molecules).
Azimuthal quantum number the quantum
number relating to the shape of an atomic orbital; it can
assume any integral value from 0 to n - 1for each value of
n.
Ball-and-stick model a molecular model
that distorts the sizes of atoms but shows bond relationships
clearly.
Barometer a device for measuring atmospheric
pressure.
Base a substance that produces hydroxide
ions in aqueous solution; a proton acceptor.
Basic oxide an ionic oxide that dissolves
in water to produce a basic solution.
Battery a group of galvanic cells connected
in series.
Beta particle an electron produced
in radioactive decay.
Beta-particle production a decay process
for radioactive nuclides in which the mass number remains
constant and the atomic number increases. The net effect is
to change a neutron to a proton.
Binary compound a two-element compound.
Binding energy (nuclear) the energy
required to decompose a nucleus into its component nucleons.
Biochemistry the study of the chemistry
of living systems.
Biomolecule a molecule that functions
in maintaining and/or reproducing life.
Bond (chemical bond) the force that
holds two atoms together in a compound.
Bond energy the energy required to
break a given chemical bond.
Bond length the distance between the
nuclei of the two atoms that are connected by a bond.
Bonding pair an electron pair found
in the space between two atoms.
Boyle's law the volume of a given
sample of gas at constant temperature varies inversely with
the pressure.
Breeder reactor a nuclear reactor in
which fissionable fuel is produced while the reactor runs.
Bronsted-Lowry model a model proposing
that an acid is a proton donor and that a base is a proton
acceptor.
Buffer capacity the ability of a buffered
solution to absorb protons or hydroxide ions without a significant
change in pH.
Buffered solution a solution that resists
a change in its pH when either hydroxide ions or protons are
added.
Calorie a unit of measurement for energy;
1calorie is the quantity of energy required to heat I gram
of water by one Celsius degree.
Calorimetry the science of measuring
heat flow.
Carbohydrate a polyhydroxyl ketone
or polyhydroxyl aldehyde or a polymer composed of these.
Carbon steel an alloy of iron containing
up to about 1.5% carbon.
Carboxyl group the -COOH group in
an organic acid.
Carboxylic acid an organic compound
containing the carboxyl group.
Catalyst a substance that speeds up
a reaction without being consumed.
Cathode in a galvanic cell, the electrode
at which reduction occurs.
Cathode rays the "rays" emanating
from the negative electrode (cathode) in a partially evacuated
tube; a stream of electrons.
Cathodic protection the connection
of an active metal, such as magnesium, to steel in order to
protect the steel from corrosion.
Cation a positive ion.
Cell potential (electromotive force)
the driving force in a galvanic cell that pulls electrons
from the reducing agent in one compartment to the oxidizing
agent in the other.
Chain reaction (nuclear) a self-sustaining
fission process caused by the production of neutrons that
proceed to split other nuclei.
Charles's law the volume of a given
sample of gas at constant pressure is directly proportional
to the temperature in kelvins.
Chemical change the change of substances
into other substances through a reorganization of the atoms;
a chemical reaction.
Chemical equation a representation
of a chemical reaction showing the relative numbers of reactant
and product molecules.
Chemical equilibrium a dynamic reaction
system in which the concentrations of all reactants and products
remain constant as a function of time,
Chemical formula a representation of
a molecule in which the symbols for the elements are used
to indicate the types of atoms present and subscripts are
used to show the relative numbers of atoms.
Chemical kinetics the area of chemistry
that concerns reaction rates.
Chemical property the ability of a
substance to change to a different substance.
Chemical stoichiometry the quantities
of materials consumed and produced in a chemical reaction.
Collision model a model based on the
idea that molecules must collide in order to react; used to
account for the observed characteristics of reaction rates.
Combustion reaction the vigorous and
exothermic oxidation- reduction reaction that takes place
between certain substances (particularly organic compounds)
and oxygen.
Complete ionic equation an equation
that shows as ions all substances that are strong electrolytes.
Compound a substance with constant
composition that can be broken down into elements by chemical
processes.
Condensation the process by which vapor
molecules re-form a liquid.
Condensed states of matter liquids
and solids.
Conjugate acid the species formed when
a proton is added to a base.
Conjugate acid-base pair two species
related to each other by the donating and accepting of a single
proton.
Conjugate base what remains of an acid
molecule after a proton is lost.
Continuous spectrum a spectrum that
exhibits all the wavelengths of visible light.
Control rods in a nuclear reactor,
rods composed of substances that absorb neutrons. These rods
regulate the power level of the reactor.
Core electron an inner electron in
an atom; one that is not in the outermost (valence) principal
quantum level.
Corrosion the process by which metals
are oxidized in the atmosphere.
Covalent bonding a type of bonding
in which atoms share electrons.
Critical mass the mass of fissionable
material required to produce a self-sustaining chain reaction.
Critical reaction (nuclear) a reaction
in which exactly one neutron from each fission event causes
another fission event, thus sustaining the chain reaction.
Crystalline solid a solid characterized
by the regular arrangement of its components.
Dalton's law of partial pressures for
a mixture of gases in a container, the total pressure exerted
is the sum of the pressures that each gas would exert if it
were alone.
Denaturation the breaking down of the
three-dimensional structure of a protein, resulting in the
loss of its function.
Density a property of matter representing
the mass per unit volume.
Deoxyribonucleic acid (DNA) a huge
nucleotide polymer having a double-helical structure with
complementary bases on the two strands. Its major functions
are protein synthesis and the storage and transport of genetic
information.
Diatomic molecule a molecule composed
of two atoms.
Dilution the process of adding solvent
to lower the concentration of solute in a solution.
Dipole-dipole attraction the attractive
force resulting when polar molecules line up such that the
positive and negative ends are close to each other.
Dipole moment a property of a molecule
where the charge distribution can be represented by a center
of positive charge and a center of negative charge.
Disaccharide a sugar formed from two
monosaccharides joined by a glycoside linkage.
Distillation a method for separating
the components of a liquid mixture that depends on differences
in the ease of vaporization of the components.
Double bond a bond in which two atoms
share two pairs of electrons.
Dry cell battery a common battery
used in calculators, watches, radios, and tape players.
Electrical conductivity the ability
to conduct an electric current.
Electrochemistry the study of the
interchange of chemical and electrical energy.
Electrolysis a process that involves
forcing a current through a cell to cause a nonspontaneous
chemical reaction to occur.
Electrolyte a material that dissolves
in water to give a solution that conducts an electric current.
Electrolytic cell a cell that uses
electrical energy to produce a chemical change that would
not otherwise occur.
Electromagnetic radiation radiant energy
that exhibits wave- like behavior and travels through space
at the speed of light in a vacuum.
Electron a negatively charged particle
that occupies the space around the nucleus of an atom.
Electronegativity the tendency of an
atom in a molecule to attract shared electrons to itself.
Element a substance that cannot be
decomposed into simpler substances by chemical or physical
means. It consists of atoms that all have the same atomic
number.
Empirical formula the simplest whole-number
ratio of atoms in a compound.
End point the point in a titration
at which the indicator changes color.
Endothermic refers to a reaction where
energy (as heat) flows into the system.
Energy the capacity to do work or to
cause the flow of heat.
Enthalpy at constant pressure, the
change in enthalpy equals the energy flow as heat.
Enzyme a large molecule, usually a
protein, that catalyzes biological reactions.
Equilibrium constant the value obtained
when equilibrium concentrations of the chemical species are
substituted into the equilibrium expression.
Equilibrium expression the expression
(from the law of mass action) is equal to the product of the
product concentrations divided by the product of the reactant
concentrations, each concentration having first been raised
to a power represented by the coefficient in the balanced
equation.
Equilibrium position a particular set
of equilibrium concentrations.
Equivalence point (stoichiometric point)
the point in a titration when enough titrant has been added
to react exactly with the substance in solution that is being
titrated.
Essential elements the elements known
to be essential to human life.
Ester an organic compound produced
by the reaction between a carboxylic acid and an alcohol.
Exothermic refers to a reaction where
energy (as heat) flows out of the system.
Exponential notation expresses a number
in the form N x 10M; a convenient method for representing
a very large or very small number and for easily indicating
the number of significant figures.
Fat (glyceride) an ester composed
of glycerol and fatty acids. Fatty acid a long-chain carboxylic
acid.
Filtration a method for separating
the components of a mixture containing a solid and a liquid.
Fission the process of using a neutron
to split a heavy nucleus into two nuclei with smaller mass
numbers.
Fossil fuel a fuel that consists of
carbon-based molecules derived from decomposition of once-living
organisms; coal, petroleum, or natural gas.
Frequency the number of waves (cycles)
per second that pass a given point in space.
Fuel cell a galvanic cell for which
the reactants are continuously supplied.
Functional group an atom or group of
atoms in hydrocarbon derivatives that contains elements in
addition to carbon and hydrogen.
Fusion the process of combining two
light nuclei to form a heavier, more stable nucleus.
Galvanic cell a device in which chemical
energy from a spontaneous redox reaction is changed to electrical
energy that can be used to do work.
Galvanizing a process in which steel
is coated with zinc to prevent corrosion.
Gamma (y) ray a high-energy photon.
Gas one of the three states of matter;
has neither fixed shape nor fixed volume.
Geiger-Miiller counter (Geiger counter)
an instrument that measures the rate of radioactive decay
by registering the ions and electrons produced as a radioactive
particle passes through a gas-filled chamber,
Gene a given segment of the DNA molecule
that contains the code for a specific protein.
Greenhouse effect a warming effect
exerted by certain molecules in the earth's atmosphere (particularly
carbon dioxide and water).
Ground state the lowest possible energy
state of an atom or molecule.
Group (of the periodic table) a vertical
column of elements having the same valance electron configuration
and similar chemical properties.
Haber process the manufacture of ammonia
from nitrogen and hydrogen, carried out at high pressure and
high temperature with the aid of a catalyst.
Half-life (of a radioactive sample)
the time required for the number of nuclides in a radioactive
sample to reach half the original number of nuclides.
Half-reactions the two parts of an
oxidation-reduction reaction, one representing oxidation,
the other reduction.
Halogen a Group 7 element.
Hard water water from natural sources
that contains relatively large concentrations of calcium and
magnesium ions.
Heat energy transferred between two
objects because of a temperature difference between them.
Heating curve a plot of temperature
versus time for a substance, where energy is added at a constant
rate.
Heisenberg uncertainty principle a
principle stating that there is a fundamental limitation to
how precisely we can know both the position and the momentum
of a particle at a given time.
Herbicide a pesticide applied to kill
weeds.
Heterogeneous equilibrium an equilibrium
involving reactants and/or products in more than one state.
Heterogeneous mixture a mixture that
has different properties in different regions of the mixture.
Homogeneous equilibrium an equilibrium
system where all reactants and products are in the same state.
Homogeneous mixture a mixture that
is the same throughout; a solution.
Hydration the interaction between
solute particles and water molecules.
Hydride a binary compound containing
hydrogen.
Hydrocarbon a compound composed of
carbon and hydrogen.
Hydrocarbon derivative an organic molecule
that contains one or more elements in addition to carbon and
hydrogen.
Hydrogen bonding unusually strong dipole-dipole
attractions that occur among molecules in which hydrogen is
bonded to a highly electronegative atom.
Hydrohalic acid an aqueous solution
of a hydrogen halide.
Hypothesis one or more assumptions
put forth to explain observed phenomena.
Ideal gas a hypothetical gas that
exactly obeys the ideal gas law. A real gas approaches ideal
behavior at high temperature and/or low pressure.
Ideal gas law an equation relating
the properties of an ideal gas, expressed as PV= nRT, where
P= pressure, V= volume, n = moles of the gas, /? = the universal
gas constant, and T= temperature on the Kelvin scale. This
equation expresses behavior closely approached by real gases
at high temperature and/or low pressure.
Indicator a chemical that changes color
and is used to mark the end point of a titration.
Intermolecular forces relatively weak
interactions that occur between molecules.
Intramolecular forces interactions
that occur within a given molecule.
Ion an atom or a group of atoms that
has a net positive or negative charge.
Ionic bonding the attraction between
oppositely charged ions.
Ionic compound a compound that results
when a metal reacts with a nonmetal to form cations and anions.
Ionic solid a solid containing cations
and anions that dissolves in water to give a solution containing
the separated ions, which are mobile and thus free to conduct
an electric current.
lonization energy the quantity of
energy required to remove an electron from a gaseous atom
or ion.
Isomers species that have the same
chemical formula but different properties.
Isotopes atoms of the same element
(the same number of protons) but different numbers of neutrons.
They have identical atomic numbers but different mass numbers.
Joule a unit of measurement for energy;
I calorie = 4.184 joules.
Ketone an organic compound containing
the carbonyl group bonded to two carbon atoms.
Kinetic energy energy due to the motion
of an object; dependent on the mass of the object and the
square of its velocity.
Kinetic molecular theory a model that
assumes that an ideal gas is composed of tiny particles (molecules)
in constant motion.
Lanthanide series a group of fourteen
elements following lanthanum in the periodic table, in which
the 4/orbitals are being filled.
Lattice a three-dimensional system
of points designating the positions of the centers of the
components of a solid (atoms, ions, or molecules).
Law of chemical equilibrium a general
description of the equilibrium condition; it defines the equilibrium
expression.
Law of conservation of energy energy
can be converted from one form to another but can be neither
created nor destroyed.
Law of conservation of mass mass is
neither created nor destroyed.
Law of constant composition a given
compound always contains elements in exactly the same proportion
by mass.
Law of mass action (also called the
law of chemical equilibrium) a general description of the
equilibrium condition; it defines the equilibrium expression.
Law of multiple proportions a law staling
that when two elements form a series of compounds, the ratios
of the masses of the second element that combine with one
gram of the first element can always be reduced to small whole
numbers.
Lead storage battery a battery (used
in cars) in which the anode is lead, the cathode is lead coated
with lead dioxide, and the electrolyte is a sulfuric acid
solution.
Le Chatelier's principle if a change
is imposed on a system at equilibrium, the position of the
equilibrium will shift in a direction that tends to reduce
the effect of that change.
Lewis structure a diagram of a molecule
showing how the valence electrons are arranged among the atoms
in the molecule.
Limiting reactant (limiting reagent)
the reactant that is completely consumed when a reaction is
run to completion.
Line spectrum a spectrum showing only
certain discrete wavelengths.
Linear accelerator a type of particle
accelerator in which a changing electrical field is used to
accelerate a positive ion along a linear path.
Lipids water-insoluble substances that
can be extracted from cells by nonpolar organic solvents.
Liquid one of the three states of matter;
has a fixed volume but takes the shape of its container.
London dispersion forces the relatively
weak forces, which exist among noble gas atoms and nonpolar
molecules, that involve an accidental dipole that induces
a momentary dipole in a neighbor.
Lone pair an electron pair that is
localized on a given atom; an electron pair not involved in
bonding.
Magnetic quantum number the quantum
number reflecting the orientation of an orbital in space relative
to the other orbitals with the same / quantum number. It can
have integral values between / and - /, including zero.
Main-group (representative) elements
elements in the groups labeled 1,2,3,4,5,6,7, and 8 in the
periodic table. The group number gives the sum of the valence
s and p electrons.
Mass the quantity of matter in an object.
Mass number the total number of protons
and neutrons in the atomic nucleus of an atom.
Mass percent the percent by mass of
a component of a mixture or of a given element in a compound.
Matter the material of the universe.
Metal an element that gives up electrons
relatively easily and is typically lustrous, malleable, and
a good conductor of heat and electricity.
Metalloid an element that has both
metallic and nonmetallic properties.
Metallurgy the process of separating
a metal from its ore and preparing it for use.
Millimeters of mercury (mm Hg) a unit
of measurement for pressure, also called a torr; 760 mm Hg
- 760 torr = 101,325 Pa = I standard atmosphere.
Mixture a material of variable composition
that contains two or more substances.
Model (theory) a set of assumptions
put forth to explain the observed behavior of matter. The
models of chemistry usually involve assumptions about the
behavior of individual atoms or molecules.
Moderator a substance used in a nuclear
reactor to slow down the neutrons.
Molar heat of fusion the energy required
to melt I mol of a solid.
Molar heat of vaporization the energy
required to vaporize I mol of a liquid.
Molar mass the mass in grams of one
mole of a compound.
Molar volume the volume of one mole
of an ideal gas; equal to 22.42 liters at standard temperature
and pressure.
Molarity moles of solute per volume
of solution in liters.
Mole (mol) the number equal to the
number of carbon atoms in exactly 12 grams of pure 12C: Avogadro's
number. One mole represents 6.022 x 1023 units.
Mole ratio (stoichiometry) the ratio
of moles of one substance to moles of another substance in
a balanced chemical equation.
Molecular equation an equation representing
a reaction in solution and showing the reactants and products
in undissociated form, whether they are strong or weak electrolytes.
Molecular formula the exact formula
of a molecule, giving the types of atoms and the number of
each type.
Molecular solid a solid composed of
neutral molecules.
Molecular structure the three-dimensional
arrangement of atoms in a molecule.
Molecular weight (molar mass) the mass
in grams of one mole of a substance.
Molecule a bonded collection of two
or more atoms of the same element or different elements.
Monoprotic acid an acid with one acidic
proton.
Natural law a statement that expresses
generally observed behavior.
Net ionic equation an equation for
a reaction in solution, representing strong electrolytes as
ions and showing only those components that are directly involved
in the chemical change.
Network solid an atomic solid containing
strong directional covalent bonds. ]
Neutralization reaction an acid-base
reaction.
Neutron a particle in the atomic nucleus
with a mass approximately equal to that of the proton but
with no charge.
Noble gas a Group 8 element.
Nonelectrolyte a substance that, when
dissolved in water, gives a nonconducting solution.
Nonmetal an element that does not exhibit
metallic characteristics. Chemically, a typical nonmetal accepts
electrons from a metal.
Normal boiling point the temperature
at which the vapor pressure of a liquid is exactly one atmosphere;
the boiling temperature under one atmosphere of pressure.
Normal melting/freezing point the melting/freezing
point of a solid at a total pressure of one atmosphere.
Normality the number of equivalents
of a substance dissolved in a liter of solution.
Nuclear atom the modern concept of
the atom as having a dense center of positive charge (the
nucleus) and electrons moving around the outside.
Nuclear transformation the change of
one element into another.
Nucleon a particle in an atomic nucleus,
either a neutron or a proton.
Nucleus the small, dense center of
positive charge in an atom.
Octet rule the observation that atoms
of nonmetals form the most stable molecules when they are
surrounded by eight electrons (to fill their valence orbitals).
Orbital a representation of the space
occupied by an electron in an atom; the probability distribution
for the electron.
Organic acid
an acid with a carbon-atom backbone and a carboxyl group.
Organic chemistry the study of carbon-containing
compounds (typically containing chains of carbon atoms) and
their properties.
Oxidation an increase in oxidation
state (a loss of electrons).
Oxidation-reduction (redox) reaction
a reaction in which one or more electrons are transferred.
Oxidation states a concept that provides
a way to keep track of electrons in oxidation-reduction reactions
according to certain rules.
Oxidizing agent (electron acceptor)
a reactant that accepts electrons from another reactant.
Oxyacid an acid in which the acidic
proton is attached to an oxygen atom.
Ozone 03, a
form of elemental oxygen much less common than 02
in the atmosphere near the earth.
Partial pressures the independent pressures
exerted by different gases in a mixture.
Particle accelerator a device used
to accelerate nuclear particles to very high speeds.
Pascal the SI unit of measurement for
pressure; equal to newtons per square meter.
Percent yield the actual yield of a
product as a percentage of the theoretical yield.
Periodic table a chart showing all
the elements arranged in columns in such a way that all the
elements in a given column exhibit similar chemical properties.
pH scale a log scale based on 10 and
equal to -log[H@]; a convenient way to represent solution
acidity.
Phenyl group the benzene molecule minus
one hydrogen atom.
Photochemical smog air pollution produced
by the action of light on oxygen, nitrogen oxides, and unburned
fuel from auto exhaust to form ozone and other pollutants.
Photon a "particle" of electromagnetic
radiation.
Physical change a change in the form
of a substance, but not in its chemical nature; chemical bonds
are not broken in a physical change.
Physical property a characteristic
of a substance that can change without the substance becoming
a different substance.
Polar covalent bond a covalent bond
in which the electrons are not shared equally because one
atom attracts them more strongly than the other.
Polar molecule a molecule that has
a permanent dipole moment.
Polyatomic ion an ion containing a
number of atoms.
Polyelectronic atom an atom with more
than one electron.
Polymer a large, usually chain-like
molecule built from many small molecules (monomers).
Polymerization a process in which many small
molecules (monomers) are joined together to form a large molecule.
Polyprotic acid an acid with more than
one acidic proton. It dissociates in a stepwise manner, one
proton at a time.
Porous disk a disk in a tube connecting
two different solutions in a galvanic cell; it allows ion
flow without extensive mixing of the solutions.
Positron production a mode of nuclear
decay in which a particle is formed that has the same mass
as an electron but opposite charge. The net effect is to change
a proton to a neutron.
Potential energy energy due to position
or composition.
Precipitation reaction a reaction in
which an insoluble substance forms and separates from the
solution as a solid.
Precision the degree of agreement among
several measurements of the same quantity; the reproducibility
of a measurement.
Primary structure (of a protein) the
order (sequence) of amino acids in the protein chain.
Principal quantum number the quantum
number reflecting the size and energy of an orbital; it can
have any positive integer value.
Probability distribution (orbital) a
representation indicating the probabilities of finding an
electron at various points in space.
Product a substance resulting from
a chemical reaction. It is shown to the right of the arrow
in a chemical equation.
Protein a natural polymer formed by
condensation reactions between amino acids.
Proton a positively charged particle
in an atomic nucleus.
Pure substance a substance with constant
composition.
Radioactive decay (radioactivity) the
spontaneous decomposition of a nucleus to form a different
nucleus.
Radiocarbon dating (carbon-14 dating)
a method for dating ancient wood or cloth on the basis of
the radioactive decay of the nuclide C.
Radiotracer a radioactive nuclide,
introduced into an organism for diagnostic purposes, whose
pathway can be traced by monitoring its radioactivity.
Random error an error that has an equal
probability of being high or low.
Rate of decay the change per unit time
in the number of radioactive nuclides in a sample.
Reactant a starting substance in a
chemical reaction. It appears to the left of the arrow in
a chemical equation.
Reactor core the part of a nuclear
reactor where the fission reaction takes place.
Reducing agent (electron donor) a
reactant that donates electrons to another substance, reducing
the oxidation state of one of its atoms.
Reduction a decrease in oxidation state
(a gain of electrons).
Rem a unit of radiation dosage that
accounts for both the energy of the dose and its effectiveness
in causing biological damage (from roentgen equivalent for
man).
Resonance a condition occurring when
more than one valid Lewis structure can be written for a particular
molecule. The actual electronic structure is represented not
by any one of the Lewis structures but by the average of all
of them.
Salt an ionic compound.
Salt bridge a U-tube containing an
electrolyte that connects the two compartments of a galvanic
cell, allowing ion flow without extensive mixing of the different
solutions.
Saturated solution a solution that
contains as much solute as can be dissolved in that solution.
Scientific method a process of studying
natural phenomena that involves making observations, forming
laws and theories, and testing theories by experimentation.
Scientific notation see Exponential
notation.
Scintillation counter an instrument
that measures radioactive decay by sensing the flashes of
light that the radiation produces in a substance.
Secondary structure (of a protein)
the three-dimensional structure of the protein chain (for
example, i@-helix, random coil, or pleated sheet).
SI units International System of units
based on the metric system and on units derived from the metric
system.
Sigma bond a covalent bond in which
the electron pair is shared in an area centered on a line
running between the atoms.
Significant figures the certain digits
and the first uncertain digit of a measurement.
Silica the fundamental silicon-oxygen
compound, which has the empirical formula SiO2
and forms the basis of quartz and certain types of sand.
Silicates salts that contain metal
cations and polyatomic silicon-oxygen anions that are usually
polymeric.
Single bond a bond in which two atoms
share one pair of electrons.
Solid one of the three states of matter;
has a fix.ed shape and volume.
Solubility the amount of a substance
that dissolves in a given volume of solvent or solution at
a given temperature.
Solubility product the constant for
the equilibrium expression representing the dissolving of
an ionic solid in water.
Solute a substance dissolved in a solvent
to form a solution.
Solution a homogeneous mixture.
Solvent the dissolving medium in a
solution.
Somatic damage radioactive damage to
an organism resulting in its sickness or death.
Specific heat another name for specific
heat capacity.
Specific heat capacity the amount of
energy required to raise the temperature of one gram of a
substance by one Celsius degree.
Spectator ions ions present in solution
that do not participate directly in a reaction.
Standard atmosphere a unit of measurement
for pressure equal to 760 mm Hg.
Standard solution a solution the concentration
of which is accurately known.
Standard temperature and pressure (STP)
the condition 0 @C and I atmosphere of pressure.
States of matter the three different
forms in which matter can exist: solid, liquid, and gas.
Stoichiometric quantities quantities
of reactants mixed in exactly the amounts that result in their
all being used up at the same time.
Stoichiometry of a reaction the relative
quantities of reactants and products involved in the reaction.
Strong acid an acid that completely
dissociates to produce an H" ion and the conjugate base.
Strong base a metal hydroxide salt
that completely dissociates into its ions in water.
Strong electrolyte a material that,
when dissolved in water, gives a solution that conducts an
electric current very efficiently.
Structural formula the representation
of a molecule in which the relative positions of the atoms
are shown and the bonds are indicated by lines.
Subcritical reaction (nuclear) a reaction
in which fewer than one of the neutrons from each fission
event causes another fission event and the process dies out.
Sublimation the process by which a
substance goes directly from the solid state to the gaseous
state without passing through the liquid state.
Substitution reaction (hydrocarbons)
a reaction in which an atom, usually a halogen, replaces a
hydrogen atom in a hydrocarbon.
Supercooling the process of cooling
a liquid below its freezing point without its changing to
a solid.
Supercritical reaction (nuclear) a
reaction in which more than one of the neutrons from each
fission event causes another fission event. The process rapidly
escalates to a violent explosion.
Superheating the process of heating
a liquid above its boiling point without its boiling.
Systematic error an error that always
occurs in the same direction.
Tertiary structure (of a protein) the
overall shape of a protein, long and narrow or globular, maintained
by different types of intramolecular interactions.
Theoretical yield the maximum amount
of a given product that can be formed when the limiting reactant
is completely consumed.
Theory (model) a set of assumptions
put forth to explain some aspect of the observed behavior
of matter.
Titration a technique in which one
solution is used to analyze another.
Torr another name for millimeter of
mercury (mm Hg).
Trace elements metals present only
in trace amounts in the human body.
Transition metals several series of
elements in which inner orbitals (dor/orbitals) are being
filled.
Transuranium elements the elements
beyond uranium that are made artificially by particle bombardment.
Triple bond a bond in which two atoms
share three pairs of electrons.
Uncertainty (in measurement) the characteristic
reflecting the fact that any measurement involves estimates
and cannot be exactly reproduced.
Unit factor an equivalance statement
between units that is used for converting from one set of
units to another.
Universal gas constant the combined
proportionality constant in the ideal gas law; 0.08206 L atm/K
mol, or 8.314 J/K mol.
Unsaturated solution a solution in
which more solute can be dissolved than is dissolved already.
Valence electrons the electrons in
the outermost occupied principal quantum level of an atom.
Valence shell electron pair repulsion (VSEPR)
model a model the main postulate of which is that the
structure around a given atom in a molecule is determined
principally by the tendency to minimize electron-pair repulsions.
Vapor pressure the pressure of the
vapor over a liquid at equilibrium in a closed container.
Vaporization (evaporation) the change
in state that occurs when a liquid evaporates to form a gas.
]
Viscosity the resistance of a liquid
to flow.Volt the unit of measurement for electrical
potential; it is defined as one joule of work per coulomb
of charge transferred.
Wavelength the distance between two
consecutive peaks or troughs in a wave.
Weak acid an acid that dissociates
only to a slight extent in aqueous solution.
Weak base a base that reacts with water
to produce hydroxide ions to only a slight extent in aqueous
solution.
Weak electrolyte a material that, when
dissolved in water, gives a solution that conducts only a
small electric current.
Weight the force exerted on an object
by gravity.
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