SAT Chemistry Vocabulary Flashcards
The outer energy level electron configuration characteristic of the inert gases.
noble gas structure (two electrons for helium; eight electrons for all others)
The glowing mass of gas and luminous particles produced by the burning of a gaseous substance.
flame
The number of molecules in 1 gram-molecular volume of a substance, or the number of atoms in 1 gram-atomic mass of an element; equal to 6.022169 x 10^23.
Avogadro’s number
adsorption
The adhesion (in an extremely thin layer) of the molecules of gases, of dissolved substances, or of liquids to the surfaces of solid or liquid bodies with which they come into contact.
W = Fs
Work. The product of the force exerted on a body and the distance through which the force acts; where W = work, F = force, and s = distance.
reduction
A chemical reaction that removes oxygen from a substance; a gain of electrons.
cathode
The electrode in an electrolytic cell that is negatively charged and attracts positive ions.
A unit for expressing the kinetic energy of subatomic particles.
MeV (Equals 10^6 electron volts.)
basic anhydride
A metallic oxide that forms a base when placed in water.
An organic hydroxyl compound formed by replacing one or more hydrogen atoms of a hydrocarbon with an equal number of hydroxyl (OH) groups.
alcohol
element
One of more than 100 “building blocks” of which all matter is composed. An element consists of atoms of only one kind and cannot be decomposed further by ordinary chemical means.
nonmetal
(a) An element whose oxide reacts with water to form an acid; (b) an element that takes on electrons and acquires a negative valence.
µ
abbreviation for atomic mass unit or micron
control rod
In a nuclear reactor, a rod of a certain metal such as cadmium, which controls the speed of the chain reaction by absorbing neutrons.
When a gas is made up of a mixture of different gases, the pressure of the mixture is equal to the sum of the partial pressures of the components.
Dalton’s law
The specific temperature at which a given solid changes into a liquid.
melting point
A natural or synthesized silicate used to soften water.
zeolite
A horizontal row of elements in the Periodic Table.
period
Equal volumes of gases under identical conditions of temperature and pressure contain equal numbers of particles (atoms, molecules, ions, or electrons).
Avogadro’s law
The average mean value of the isotopic masses of the atoms of an element. It indicates the relative mass of the element as compared with that of carbon-12, which is assigned a mass of exactly 12 atomic mass units.
atomic mass or relative atomic mass or atomic weight
Two or more forms of an element that differ only in the number of neutrons in the nucleus and hence in their mass numbers.
isotopes
atom
The smallest particle of an element that retains the properties of that element and can enter into a chemical reaction.
weak electrolyte
A substance that, when dissolved in water, ionizes only slightly and hence is a poor conductor of electricity.
nuclear fuel
A substance that is consumed during nuclear fission or fusion.
flammable
Capable of being easily set of fire; combustible (same as inflammable).
electronegativity
The numerical expression of the relative strength with which the atoms of an element attract valence electrons to themselves; the higher the number, the greater the attraction.
A bond in which electrons are closer to one atom than to another.
polar covalent bond (See also polar molecule.)
Gay-Lussac’s law
(Also Combining Volumes law.) The ratio between the combining volumes of gases and the product, if gaseous, can be expressed in small whole numbers.
pitchblende
A massive variety of uraninite that contains a small amount of radium.
Any reaction involving a change in nuclear structure.
nuclear reaction
Hess’s law
If a series of reactions are added together, the enthalpy change for the total reaction is the sum of the enthalpy changes for the individual steps.
A phase of matter that has a definite volume but takes the shape of the container.
liquid
atmosphere
The layer of gases surrounding Earth; also, a unit of pressure (1 atm = approximately 760 mm of Hg or torr).
The intensity or degree of heat of a body, measured by a thermometer.
temperature
The SI unit of pressure, equal to 1 newton per square meter.
pascal
Aufbau Principle
The principle that states that an electron occupies the lowest energy orbital that can receive it.
empirical formula
A formula that shows only the simplest ratio of the numbers and kinds of atoms, such as CH4.
salt
A compound, such as NaCl, made up of a positive metallic ion and a negative nonmetallic ion or radical.
A positive or negative number representing the charge that an ion has or an atom appears to have when its electrons are counted according to arbitrarily accepted rules: (1) electrons shared by two unlike atoms are counted with the more electronegative atom; (2) electrons shared by two like atoms are divided equally between the atoms.
oxidation number (state)
The science that deals with the constituents and all the changes in the atomic nucleus.
nucleonics
A nonmetallic oxide that, when placed in water, reacts to form an acid solution.
acidic anhydride
The ratio between the number of calories needed to raise the temperature of a certain mass of a substance 1 degree on the Celsius scale and the number of calories needed to raise the temperature of the same mass of water 1 degree on the Celsius scale.
specific heat
atomic number
The number that indicates the order of an element in the periodic system; numerically equal to the number of protons in the nucleus of the atom, or the number of negative electrons located outside the nucleus of the atom.
pH
A numerical expression of the hydrogen or hydronium ion concentration in a solution; defined as -log[H+] where [H+] is the concentration of hydrogen ions, in moles per liter.
A group of chemically united atoms that react as a unit and have an electric charge.
polyatomic ion
strong acid (or base)
An acid (or a base) capable of a high degree of ionization in water solution. Example: sulfuric acid (sodium hydroxide).
molar mass
The mass arrived at by the addition of the atomic masses of the units that make up a molecule of an element or compound. Expressed in grams/mole, the molar mass of a gaseous substance at STP occupies a molar volume equal to 22.4 liters.
nuclide
A species of atom characterized by the constitution of its nucleus.
A substance that, when added to a solution, makes changing the pH of the solution more difficult.
buffer
carbonated water
Water containing dissolved carbon dioxide.
matter
A substance that occupies space, has mass, and cannot be created or destroyed easily.
diffusion
The process whereby gases or liquids intermingle freely of their own accord.
The mass arrived at by the addition of the atomic masses of the units that make up a molecule of an element or compound.
molar mass (Expressed in grams/mole, the molar mass of a gaseous substance at STP occupies a molar volume equal to 22.4 liters.)
hydronium ion
A hydrated ion, H2O.H+ or H3O+.
dehydrating agent
A substance able to withdraw water from another substance, thereby drying it.
nitrogen fixation
Any process by which atmospheric nitrogen is converted into a compound such as ammonia or nitric acid.
amorphous
Having no definite crystalline structure.
Conversion of one element into another, either by bombardment or by radioactive disintegration.
transmutation
heavy water
(Also deuterium oxide, D2O) Water in which the hydrogen atoms are replaced by the atoms of the isotope of hydrogen, deuterium.
An organic compound containing the -CO- group.
ketone
fluorescence
Emission by a substance of electromagnetic radiation, usually visible, as the immediate result of (and only during) absorption of energy from another source.
An inorganic substance of definite composition found in nature.
mineral
A chemical reaction between an alcohol and an acid, in which an ester is formed.
esterification
spinthariscope
A device for viewing through a microscope the flashes of light made by particles from radioactive materials against a sensitized screen.
ionization equation
An equation showing the ions set free from an electrolyte.
The bonding of ions due to their opposite charges.
ionic bonding
The reaction of two molecules by loss of a molecule of water.
condensation polymerization
An electrode potential associated with the oxidation half-reaction.
oxidation potential
A device used to accelerate charged particles to high energies for bombarding the nuclei of atoms.
cyclotron
Lewis dot symbol
The chemical symbol (kernel) for an atom, surrounded by dots to represent its outer level electrons. Examples: K., Sr:. (Also called electron dot symbol.)
Of carbohydrates: the action of water in the presence of a catalyst upon one carbohydrate to form simpler carbohydrates.
hydrolysis
Referring to an element in the atomic form as it has just been liberated in a chemical reaction.
nascent (atomic)
glass
An amorphous, usually translucent substance consisting of a mixture of silicates. Ordinary glass is made by fusing together silica and sodium carbonate and lime; the various forms of glass contain many other silicates.
An equation showing a reaction among ions.
ionic equation
The sum of the atomic mass units of all the atoms (or ions) contained in a formula.
formula mass
Systeme International d’Unites
The modernized metric system of measurements universally used by scientists. There are seven base units: kilogram, meter, second, ampere, kelvin, mole, and candela.
analysis
The breaking down of a compound into two or more simpler substances.
deuterium
An isotope of hydrogen, sometimes called heavy hydrogen, with an atomic weight of 2.
The combining power of an element; the number of electrons gained, lost, or borrowed in a chemical reaction.
valence
volatile
Easily changed to a gas or a vapor at relatively low pressure.
A shortened name for a reaction that involves reduction and oxidation.
redox
plasma
Very hot ionized gases.
nuclear reaction
Any reaction involving a change in nuclear structure.
A numerical expression of the hydrogen or hydronium ion concentration in a solution.
pH
The flow of a gas through a small aperture.
effusion
electrode
A terminal of an electrolytic cell.
double bond
A bond between atoms involving two electron pairs. In organic chemistry: unsaturated.
volt
A unit of electrical potential or voltage, equal to the difference of potential between two points in a conducting wire carrying a constant current of 1 ampere when the power dissipated between these two points is equal to 1 watt (abbreviation: V).
efflorescence
The loss by a substance of its water of hydration on exposure to air at ordinary temperatures.
The specific temperature at which a given liquid and its solid form are in equilibrium.
freezing point
A property that determines how a substance will behave in a chemical reaction.
chemical property
A measure of the amount of solute that will dissolve in a given quantity of solvent at a given temperature.
solubility
Any of the five nonmetallic elements (fluorine, chlorine, bromine, iodine, astatine) that form part of Group 17 of the Periodic Table.
halogen
dew point
The highest temperature at which water vapor condenses out of the air.
The separation of the components in a mixture of liquids having different boiling points by vaporization.
fractional distillation
A change from gaseous to liquid state.
condensation
The energy needed to break a chemical bond and form a neutral atom.
bond energy
A bond between atoms involving two electron pairs.
double bond (In organic chemistry: unsaturated.)
Uniform; having every portion exactly like every other portion.
homogeneous
thermosetting
Capable of being permanently hardened by heat and pressure; resistant to the further effects of heat.
The same of the oxidation potential and reduction potential for a particular reaction.
reaction potential
A compound is composed of two or more elements chemically combined in a definite ration by weight.
Definite Composition law
activation energy
The minimum energy necessary to start a reaction.
acid
A water solution that has an excess of hydrogen ions; an acid turns litmus paper pink or red, has a sour taste, and neutralizes bases to form salts.
The layer of gases surrounding Earth.
atmosphere
An organic indicator; it is colorless in acid solution and red in the presence of OH- ions.
phenolphthalein
An organic salt formed by the reaction of an alcohol with an organic (or inorganic) acid.
ester
symbol
A letter or letters representing an element of the periodic table. Examples: O, Mn.
bond energy
The energy needed to break a chemical bond and form a neutral atom.
Multiple Proportions law
When any two elements, A and B, combine to form more than one compound, the different masses of B that unite with a fixed mass of A bear a small whole-number ratio to each other.
Heat cannot, of itself, pass from a cold body to a hot body.
Second Law of Thermodynamics
Any chemical taking part in a reaction.
reagent
petroleum (meaning “oil from stone”)
A complex mixture of gaseous, liquid, and solid hydrocarbons obtained from Earth.
anion
An ion or particle that has a negative charge and thus is attracted to a positively charged anode.
Cooling a hot piece of metal rapidly, as in water or oil.
quenching
thermoplastic
Capable of being softened by heat; may be remolded.
nucleonics
The science that deals with the constituents and all the changes in the atomic nucleus.
Penetrating radiations, of extremely short wavelength, emitted when a stream of electrons strikes a solid target in a vacuum tube.
X-rays
The process in which slow oxidation produces enough heat to raise the temperature of a substance to its kindling temperature.
spontaneous combustion (ignition)
An isotope of hydrogen, sometimes called heavy hydrogen, with an atomic weight of 2.
deuterium
A change that alters the atomic structures of the substances involved and results in different properties.
chemical change
lepton
An elementary particle; the electron and neutrino are believed to consist of leptons.
law (in science)
A generalized statement about the uniform behavior in natural processes.
qualitative analysis
A term applied to methods and procedures used to determine any or all of the constituent parts of a substance.
electroplating
Depositing a thin layer of (usually) a metallic element on the surface of another metal by electrolysis.
ionization
The process in which ions are formed from neutral atoms.
One of the two parts, either the reduction part or the oxidation part, of a redox reaction.
half-reaction
A substance that is readily oxidized.
reducing agent
A device for viewing through a microscope the flashes of light made by particles from radioactive materials against a sensitized screen.
spinthariscope
breeder reactor
A nuclear reactor in which more fissionable material is produced than is used up during operation.
photosynthesis
The reaction taking place in all green plants that produces glucose from carbon dioxide and water under the catalytic action of chlorophyll in the presence of light.
A subatomic particle found in the nucleus of the atom.
neutron (It has no charge and has the same mass as the proton.)
An element who’s oxide combines with water to form a base.
metal
The process involved in obtaining a metal from its ores.
metallurgy
The process of separating the ions in a compound by means of electrically charged poles.
electrolysis
A compound in whose molecules the atoms are arranged symmetrically so that the electric charges are uniformly distributed.
nonpolar compound
A phase of matter that has neither definite shape nor definite volume.
gas
A nuclear reaction that releases energy because of the splitting of large nuclei into smaller ones.
fission
An element that readily loses electrons and acquires a positive valence.
metal
One twelfth of the mass of a carbon-12 atom.
atomic mass unit
radioactive
Referring to substances that have the ability to emit radiations (alpha or beta particles or gamma rays).
phenolphthalein
An organic indicator; it is colorless in acid solution and red in the presence of OH- ions.
A gain of electrons.
reduction
paraffin series
The methane series of hydrocarbons.
A positively charged particle of electricity with about the same weight as the electron.
positron
flame
The glowing mass of gas and luminous particles produced by the burning of a gaseous substance.
van der Waals forces
Weak attractive forces existing between molecules.
heat capacity
(Also specific heat.) The quantity of heat, in calories, needed to raise the temperature of 1 gram of a substance 1 degree on the Celsius scale.
A change by which an element takes the place of another element in a compound.
displacement
The smallest particle of a substance that retains the physical and chemical properties of that substance.
molecule (Examples: He, BR2, H2O)
metal
(a) An element who’s oxide combines with water to form a base; (b) an element that readily loses electrons and acquires a positive valence.
A substance such as graphite, paraffin, or heavy water used in a nuclear reactor to slow down neutrons.
moderator
synthesis
The chemical process of forming a substance from its individual parts.
dry ice
Solid carbon dioxide.
Le Chatelier’s Principle
If a stress is placed on a system in equilibrium, the system will react in the direction that relieves the stress.
equilibrium
The point in a reversible reaction at which the forward reaction is occurring at the same rate as the opposing reaction.
A solution containing 1 mole of solute in 1,000 grams of solvent (indicated by m).
molal solution
The process of first vaporizing a liquid and then condensing the vapor back into a liquid, leaving behind the nonvolatile impurities.
distillation
A very rare, unstable, “triple-weight” hydrogen isotope (H^3) that can be made synthetically.
tritium
A salt formed by replacing part of the hydrogen ions of a dibasic or tribasic acid with metallic ions.
acid salt (Examples NaHS04, NaH2PO4.)
The quantity of matter that a substance possesses; it can be measured by its resistance to a change in position or motion, and is not related to the force of gravity.
mass
ore
A natural mineral substance from which an element, usually a metal, may be obtained with profit.
The weight of 1 milliliter of water at 4ºC.
gram
The use of radioactive carbon-14 to estimate the ages of ancient materials, such as archeological or paleontological specimens.
carbon dating
condensation
(a) A change from gaseous to liquid state; (b) the union of like or unlike molecules with the elimination of water, hydrogen chloride, or alcohol.
radioisotope
An isotope that is radioactive, such as uranium-235.
Kelvin scale
A temperature scale based on water freezing at 273 and boiling at 373 Kelvin units; its origin is absolute zero. Synonymous with absolute scale.
Avogadro’s number
The number of molecules in 1 gram-molecular volume of a substance, or the number of atoms in 1 gram-atomic mass of an element; equal to 6.022169 x 10^23. See also mole.
mass number
The nearest whole number to the combined atomic mass of the individual atoms of an isotope when tat mass is expressed in atomic mass units.
litmus
An organic substance, obtained from the lichen plant and used as an indicator; it turns red in acidic solution and blue in basic solution.
refraction (of light)
The bending of light rays as they pass from one material into another.
The addition of unsaturated molecules to each other.
additional polymerization
quenching
Cooling a hot piece of metal rapidly, as in water or oil.
Any process for converting atmospheric nitrogen into compounds, such as ammonia and nitric acid.
fixation of nitrogen
proteins
Large, complex organic molecules, with nitrogen an essential part, found in plants and animals.
enthalpy
The heat content of a chemical system.
Chemicals certified as having a standard of purity that demonstrates their fitness for use in medicine.
U.S.P. (United States Pharmacopeia) chemicals
All the certain digits, that is, those recorded in a measurement, plus one uncertain digit.
significant figures
brass
An alloy of copper and zinc.
Water containing dissolved carbon dioxide.
carbonated water
A negatively charged particle found outside the nucleus of the atom.
electron (It has a mass of 9.109 x 10^-28 gram.)
Referring to a compound composed of two elements, such as H2O.
binary
kindling temperature
The temperature to which a given substance must be raised before it ignites.
A temperature scale divided into 100 equal divisions and based on water freezing at 0º and boiling at 100º.
Celsius scale (Synonymous with centigrade.)
A U-tube (containing mercury or some other liquid) used to measure the pressure of a confined gas.
manometer
The combination of two or more orbitals to form new orbitals.
hybridization
The numerical expression of the relative strength with which the atoms of an element attract valence electrons to themselves; the higher the number, the greater the attraction.
electronegativity
A compound whose basic structure contains the benzene ring; it usually has a odor.
aromatic compound
chemical change
A change that alters the atomic structures of the substances involved and results in different properties.
quantitative analysis
A term applied to the methods and procedures used to determine the definite quantity or percentage of any or all of the constituent parts of a substance.
Added to drinking water to help prevent tooth decay.
fluoride
The gaseous phase of a substance that normally exists as a solid or liquid at ordinary temperatures.
vapor
Periodic law
The chemical properties of elements vary periodically with their atomic numbers.
Each electron orbital of an atom can be filled by only two electrons, which have opposite spins.
Pauli Exclusion Principle
The nucleus and all the electron shells of an atom except the outer one; usually designated by the symbol for the atom.
kernel (atomic)
antichlor
A substance used to remove the excess of chlorine in the bleaching process.
The center of the atom, which contains protons and neutrons.
nucleus
isomers
Two or more compounds having the same percentage composition but different arrangements of atoms in their molecules and hence different properties.
The electrode in an electrolytic cell that is negatively charged and attracts positive ions.
cathode
spectrum
The image formed when radiant energy is dispersed by a prism or grating into its various wavelengths.
orbital
A subdivision of a nuclear shell; it may contain none, one, or two electrons.
aldehyde
An organic compound formed by dehydrating oxidized alcohol; contains the characteristic -CHO group.
A weak chemical linkage between the hydrogen of one polar molecule and the oppositely charged portion of a closely adjacent molecule.
hydrogen bond
half-reaction
One of the two parts, either the reduction part or the oxidation part, of a redox reaction.
The union of like or unlike molecules with the elimination of water, hydrogen chloride, or alcohol.
condensation
A nuclear reactor in which more fissionable material is produced than is used up during operation.
breeder reactor
The chemical process of forming a substance from its individual parts.
synthesis
structural (graphic) formula
A pictorial representation of the atomic arrangement of a molecule.
Matter can be neither created nor destroyed (or weight remains constant in an ordinary chemical change).
Conservation of Matter law
freezing point
The specific temperature at which a given liquid and its solid form are in equilibrium.
decomposition
The breaking down of a compound into simpler substances or into its constituent elements.
An ion that has a positive charge.
cation
ductile
Capable of being drawn into thin wire.
Streams of electrons given off by the cathode of a vacuum tube.
cathode rays
A graduated glass tube into which gases are placed and subjected to an electric spark; used to measure the individual volumes of combining gases.
eudiometer
Applying a coating of zinc to iron or steel to protect the latter from rusting.
galvanizing
Referring to substances that have the ability to emit radiations (alpha or beta particles or gamma rays).
radioactive
normal salt
A salt in which all the hydrogen of the acid has been displaced by a metal.
The pressure exerted by a vapor given off by a confined liquid or solid when the vapor is in equilibrium with its liquid or solid form.
vapor pressure
A metallic oxide that forms a base when placed in water.
basic anhydride
anhydride
A compound derived from another compound by the removal of water; it will combine with water to form an acid (acidic anhydride) or a base (basic anhydride).
An atom or a group of combined atoms that carries one or more electric charges.
ion (Examples: NH4-, OH-.)
The product formed when the flux reacts with the impurities of an ore in a metallurgical process.
slag
dissociation (ionic)
The separation of the ions of an ionic compound due to the action of a solvent.
Kinetic-Molecular Theory
The theory that all molecules are in motion; this motion is most rapid in gases, less rapid in liquids, and very slow in solids.
reactant
A substance involved in a reaction.
mole
A unit of quantity that consists of 6.02x10^23 particles.
The breaking down of a compound into simpler substances or into its constituent elements.
decomposition
The valence shell electron pair repulsion model. It expresses the non-90º variations in bond angles for p orbitals in the outer energy levels of atoms in molecules because of electron repulsions.
VSEPR
An allotropic and very active form of oxygen, having the formula O3.
ozone
A vertical column of elements in the periodic table that generally has similar properties.
group
organic chemistry
The branch of chemistry dealing with carbon compounds, usually those found in nature.
Any unstable, elementary nuclear particle having a mass between that of an electron and that of a proton.
meson
The adhesion (in an extremely thin layer) of the molecules of gases, of dissolved substances, or of liquids to the surfaces of solid or liquid bodies with which they come into contact.
adsorption
alcohol
An organic hydroxyl compound formed by replacing one or more hydrogen atoms of a hydrocarbon with an equal number of hydroxyl (OH) groups.
Solid carbon dioxide.
dry ice
The solubility of a gas (unless the gas is very soluble) is directly proportional to the pressure applied to the gas.
Henry’s law
barometer
An instrument, invented by Torricelli in 1643, used for measuring atmospheric pressure.
inertia
The property of matter whereby it remains at rest or, if in motion, remains in motion in a straight line unless acted upon by an outside force.
kilocalorie
A unit of heat; the amount of heat needed to raise the temperature of 1 kilogram of water 1 degree on the Celsius scale.
kernel (atomic)
The nucleus and all the electron shells of an atom except the outer one; usually designated by the symbol for the atom.
displacement
A change by which an element takes the place of another element in a compound.
A reaction in which two chemical substances exchange ions with the formation of two new compounds.
double displacement
effervescence
The rapid escape of excess gas that has been dissolved in a liquid.
A term applied to the methods and procedures used to determine the definite quantity or percentage of any or all of the constituent parts of a substance.
quantitative analysis
meson
Any unstable, elementary nuclear particle having a mass between that of an electron and that of a proton.
Capable of being hammered or pounded into thin sheets.
malleable
specific gravity (mass)
The ratio between the mass of a certain volume of a substance and the mass of an equal volume of water (or, in the case of gases, an equal volume of air); expressed as a single number.
Emitting a steady, suffused light.
luminous
The chemical symbol (kernel) for an atom, surrounded by dots to represent its outer level electrons.
Lewis dot symbol or electron dot symbol (Examples: K., Sr:.)
polyatomic ion
A group of chemically united atoms that react as a unit and have an electric charge.
Having no definite crystalline structure.
amorphous
London force
The weakest of the van der Waals forces between molecules. These weak, attractive forces become apparent only when the molecules approach one another closely (usually at low temperatures and high pressure). They are due to the way the positive charges of one molecule attract the negative charges of another molecule because of the charge distribution at any one instant.
The union of the hydrogen ion of an acid and the hydroxyl ion of a base to form water.
neutralization
An atmospheric pressure of 760 millimeters or torr or 1 atmosphere (mercury pressure) and a temperature of 0ºC (273 K) (abbreviation: STP).
standard conditions
A substance composed of two or more components, each of which retains its own properties.
mixture
IUPAC
International Union of Pure and Applied Chemistry, an organization that establishes standard rules for naming compounds.
To vaporize directly from the solid to the gaseous state, and then condense back to the solid.
sublime
emulsion
A suspension of fine particles or droplets of one liquid in another, the two liquids being immiscible in each other; the droplets are surrounded by a colloidal (emulsifying) agent.
Referring to a chemical reaction that results in an overall absorption of heat from its surroundings.
endothermic
The chemical process by which oxygen is attached to a substance.
oxidation
Fahrenheit scale
The temperature scale that has 32º as the freezing point of water and 212º as the boiling point.
Emission by a substance of electromagnetic radiation, usually visible, as the immediate result of (and only during) absorption of energy from another source.
fluorescence
volume
The amount of three-dimensional space occupied by a substance.
In metallurgy: a substance that helps to melt and remove the solid impurities as slag.
flux
tincture
An alcoholic solution of a substance, such as a tincture of iodine.
Definite Composition law
A compound is composed of two or more elements chemically combined in a definite ration by weight.
density
The mass per unit volume of a substance; the mathematical formula is D = m/V, where D = density, m = mass, and V = volume.
electron dot symbol
Lewis dot symbol. The chemical symbol (kernel) for an atom, surrounded by dots to represent its outer level electrons. Examples: K., Sr:.
The total energy of the universe is constant and cannot be created or destroyed.
First Law of Thermodynamics
Containing no water.
anhydrous
hypothesis
A possible explanation of the nature of an action or phenomenon; a hypothesis is not as completely developed as a theory.
A form of molecular energy; it passes from a warmer body to a cooler one.
heat
A shorthand method of showing the changes that take place in a chemical reaction.
equation
A phase of matter that has a definite size and shape.
solid
Usually, a strong base, such as sodium hydroxide or potassium hydroxide.
alkali
The energy released by spontaneously or artificially produced fission, fusion, or disintegration of the nuclei of atoms.
nuclear energy (sometimes called atomic energy)
beta particles
High-speed, negatively charged electrons emitted in radiation.
noble gas structure
The outer energy level electron configuration characteristic of the inert gases – two electrons for helium; eight electrons for all others.
Ideal Gas law
Any gas that obeys the gas laws perfectly. No such gas actually exists.
A type of radiation consisting of high-energy waves that can pass through most materials.
gamma rays
sublime
To vaporize directly from the solid to the gaseous state, and then condense back to the solid.
An explanation used to interpret the “mechanics” of nature’s actions.
theory (A theory is more fully developed than a hypothesis.)
The formula weight, in grams, of a substance.
gram-formula weight
reaction
A chemical transformation or change. The four basic types are combination (synthesis), decomposition (analysis), single replacement or single displacement, and double replacement or double displacement.
relative humidity
The ratio, expressed in percent, between the amount of water vapor in a given volume of air and the amount the same volume can hold when saturated at the same temperature.
slag
The product formed when the flux reacts with the impurities of an ore in a metallurgical process.
A device in which a controlled chain reaction of fissionable material can be produced.
nuclear reactor
A subdivision of a nuclear shell; it may contain none, one, or two electrons.
orbital
normal solution
A solution that contains 1 gram of H+ (or its equivalent: 17g of OH-, 23g of Na+, 20g of Ca2+, etc.) in 1 letter of solution (indicated by N).
electrolyte
A liquid that will conduct an electric current.
ionic bonding
The bonding of ions due to their opposite charges.
immiscible
Referring to the inability of two liquids to mix.
anhydrous
Containing no water.
An element that takes on electrons and acquires a negative valence.
nonmetal
A natural mineral substance from which an element, usually a metal, may be obtained with profit.
ore
A subatomic particle found in the nucleus that has a positive charge.
proton
destructive distillation
The process of heating an organic substance, such as coal, in the absence of air to break it down into solid and volatile products.
thermochemical equation
An equation that includes values for the calories absorbed or evolved.
critical mass
The smallest amount of fissionable material that will sustain a chain reaction.
crystalline
Having a definite molecular or ionic structure.
The difference in potential between an electrode and the solution in which it is immersed.
electrode potential
The numerical expression of the relative strength with which the atoms of an element attract valence electrons to themselves.
electronegativity (The higher the number, the greater the attraction.)
Easily changed to a gas or a vapor at relatively low pressure.
volatile
A substance that, when dissolved in water, ionizes only slightly and hence is a poor conductor of electricity.
weak electrolyte
oxidation potential
An electrode potential associated with the oxidation half-reaction.
endothermic
Referring to a chemical reaction that results in an overall absorption of heat from its surroundings.
indicator
A dye that shows one color in the presence of the hydrogen ion (acid) and a different color in the presence of the hydroxyl ion (base).
spectroscope
An instrument used to analyze light by separating it into its component wavelengths.
physical change
A change that doe not involve any alteration in chemical composition.
The atomic mass, in grams, of an element.
gram-atomic mass
malleable
Capable of being hammered or pounded into thin sheets.
Heating an ore (usually a sulfide) in an excess of air to convert the ore to an oxide, which can then be reduced.
roasting
A hydrated ion.
hydronium ion (H2O.H+ or H3O+)
Conservation of Energy law
Energy can be neither created nor destroyed, so that the energy of the universe is constant.
MeV
A unit for expressing the kinetic energy of subatomic particles; equals 10^6 electron volts.
The union of atoms to form compounds or molecules by filling their outer shells of electrons. This can be done through giving and taking electrons (ionic) or by sharing electrons (covalent).
bonding
Having a definite molecular or ionic structure.
crystalline
D=m/V
Density. The mass per unit volume of a substance; the mathematical formula is D = m/V, where D = density, m = mass, and V = volume.
ion
An atom or a group of combined atoms that carries one or more electric charges. Examples: NH4-, OH-.
A device for determining the masses of electrically charged particles by separating them into distinct streams by means of magnetic deflection.
mass spectograph
Energy can be neither created nor destroyed, so that the energy of the universe is constant.
Conservation of Energy law
The process in which molecules of a liquid (or a solid) leave the surface in the form of vapor.
evaporation
Einstein equation
E = mc^2, which relates mass to energy; E = energy in ergs, m = mass in grams, and c = velocity of light, 3x10^10 centimeters/second.
electron volt
A unit for expressing the kinetic energy of subatomic particles; the energy acquired by an electron when it is accelerated by a potential difference of 1 volt; equals 1.6 x 10^-12 erg or 23.1 kilocalories/mole (abbreviation: eV).
Useful in indicating the conditions under which a chemical reaction will occur.
Changes in Gibbs free energy, ∆G. (The equation is ∆G = ∆H -T∆S, where ∆H = change in enthalpy and ∆S = change in entropy. If ∆G is negative, the reaction will proceed spontaneously to equilibrium. Also called free energy.)
solubility
A measure of the amount of solute that will dissolve in a given quantity of solvent at a given temperature.
Referring to the -OH radical.
hydroxyl
Referring to the ability of a substance to draw water vapor from the atmosphere to itself and become wet.
hygroscopic
valence electrons
The electrons in the outermost level or levels of an atom that determine its chemical properties.
radiation
The emission of particles and rays from a radioactive source; usually alpha and beta particles and gamma rays.
miscible
Referring to the ability of two liquids to mix with one another.
The rate of diffusion (or effusion) of a gas is inversely proportional to the square root of its molecular mass.
Graham’s law
base
A water solution that contains an excess of hydroxide ions; a proton acceptor; a base turns litmus paper blue and neutralizes acids to form salts.
The change in phase of a substance from solid to liquid.
melting
A species of atom characterized by the constitution of its nucleus.
nuclide
Growing plants without the use of soil, as in nutrient solution or in sand irrigated with nutrient solution.
hydroponics
An accumulation of lead sulfate on the plates and at the bottom of a (lead) storage cell.
sulfation
The loss by a substance of its water of hydration on exposure to air at ordinary temperatures.
efflorescence
covalent bonding
Bonding accomplished through the sharing of electrons so that atoms can fill their outer shells.
period
A horizontal row of elements in the Periodic Table.
alloy
A substance composed of two or more metals, which are intimately mixed; usually made by melting the metals together.
name the noble gases
helium, neon, argon, krypton, xenon, and radon
An amorphous, usually translucent substance consisting of a mixture of silicates.
glass (Ordinary glass is made by fusing together silica and sodium carbonate and lime; the various forms of glass contain many other silicates.)
Capable of being drawn into thin wire.
ductile
The point in a reversible reaction at which the forward reaction is occurring at the same rate as the opposing reaction.
equilibrium
The process by which suspended matter is removed from a liquid by passing the liquid through a porous material.
filtration
Very hot ionized gases.
plasma
hybridization
The combination of two or more orbitals to form new orbitals.
Water in which the hydrogen atoms are replaced by the atoms of the isotope of hydrogen, deuterium.
heavy water or deuterium oxide or D2O
The portion of the spectrum that lies just beyond the violet; therefore of short wavelength.
ultraviolet light
Air that has been cooled and compressed until it liquifies.
liquid air
oxidizing agent
A substance that (a) gives up its oxygen readily, (b) removes hydrogen from a compound, (c) takes electrons from an element.
The amount of moisture in the air.
humidity
Temperature measured on the absolute scale, which has its origin at absolute zero.
absolute temperature (See also Kelvin scale.)
equation
A shorthand method of showing the changes that take place in a chemical reaction.
tribasic acid
An acid that contains three replaceable hydrogen atoms in its molecule, such as H3PO4.
sulfation
An accumulation of lead sulfate on the plates and at the bottom of a (lead) storage cell.
One-half the distance between adjacent nuclei in the crystalline or solid phase of an element; the distance from the atomic nucleus to the valence electrons.
atomic radius
Pauli Exclusion Principle
Each electron orbital of an atom can be filled by only two electrons, which have opposite spins.
nuclear reactor
A device in which a controlled chain reaction of fissionable material can be produced.
A liquid that will conduct an electric current.
electrolyte
suspension
A mixture of finely divided solid material in a liquid, from which the solid settles on standing.
chemical property
A property that determines how a substance will behave in a chemical reaction.
liquid
A phase of matter that has a definite volume but takes the shape of the container.
A compound such as CH3NH2, derived from ammonia by substituting one or more hydrocarbon radicals for hydrogen atoms.
amine
The heat content of a chemical system.
enthalpy
saturated solution
A solution that contains the maximum amount of solute under the existing temperature and pressure.
A generalized statement about the uniform behavior in natural processes.
law (in science)
An expression that uses the symbols for elements and subscripts to show the basic makeup of a substance.
formula
A substance that occupies space, has mass, and cannot be created or destroyed easily.
matter
reversible reaction
Any reaction that reaches an equilibrium, or that can be made to proceed from right to left as well as from left to right.
A minute quantity of radioactive isotope used in medicine and biology to study chemical changes within living tissues.
tracer
Dalton’s law
When a gas is made up of a mixture of different gases, the pressure of the mixture is equal to the sum of the partial pressures of the components.
An equation showing the ions set free from an electrolyte.
ionization equation
binary
Referring to a compound composed of two elements, such as H2O.
VSEPR
The valence shell electron pair repulsion model. It expresses the non-90º variations in bond angles for p orbitals in the outer energy levels of atoms in molecules because of electron repulsions.
mass
The quantity of matter that a substance possesses; it can be measured by its resistance to a change in position or motion, and is not related to the force of gravity.
ultraviolet light
The portion of the spectrum that lies just beyond the violet; therefore of short wavelength.
energy
The capacity to do work. In every chemical change energy is either given off or taken in. Forms of energy are heat, light, motion, sound, and electrical, chemical, and nuclear energy.
vapor pressure
The pressure exerted by a vapor given off by a confined liquid or solid when the vapor is in equilibrium with its liquid or solid form.
The temperature above which no gas can be liquefied, regardless of the pressure applied.
critical temperature
Energy due to the position of a body or to the configuration of its particles.
potential energy
chain reaction
A reaction produced during nuclear fission when at least one neutron from each fission produces another fission, so that the process becomes self-sustaining without additional external energy.
The residual radioactivity from an atmospheric nuclear test, which eventually settles on the surface of Earth.
fallout
ester
An organic salt formed by the reaction of an alcohol with an organic (or inorganic) acid.
tritium
A very rare, unstable, “triple-weight” hydrogen isotope (H^3) that can be made synthetically.
A unit of energy or work done by a force of 1 dyne (1/980 g of force) acting through a distance of 1 centimeter; equals 2.4 x 10^-11 kilocalorie.
erg
A nuclear reaction in which a neutron attaches itself to a nucleus.
neutron capture (A gamma ray is usually emitted simultaneously.)
The process whereby gases or liquids intermingle freely of their own accord.
diffusion
weak acid (or base)
An acid (or base) capable of being only slightly ionized in an aqueous solution. Example: acetic acid (ammonium hydroxide).
The phenomenon in a molecular structure that exhibits properties between those of a single bond and those of a double bond and thus possesses two or more alternative structures.
resonance
Boyle’s law
The volume of a confined gas is inversely proportional to the pressure to which it is subjected, provided that the temperature remains the same.
A terminal of an electrolytic cell.
electrode
potential energy
Energy due to the position of a body or to the configuration of its particles.
A molecule that has differently charged areas because of unequal sharing of electrons.
polar molecule
The chemical properties of elements vary periodically with their atomic numbers.
Periodic law
supersaturated solution
A solution that contains a greater quantity of solute than is normally possible at a given temperature.
Continuous zigzagging movement of colloidal particles in a dispersing medium, as viewed through an ultramicroscope.
Brownian movement
The volume of a confined gas is directly proportional to the absolute temperature, provided that the pressure remains the same.
Charles’s law
An instrument used to measure the amount of heat liberated or absorbed during a change.
calorimeter
oxidation number (state)
A positive or negative number representing the charge that an ion has or an atom appears to have when its electrons are counted according to arbitrarily accepted rules: (1) electrons shared by two unlike atoms are counted with the more electronegative atom; (2) electrons shared by two like atoms are divided equally between the atoms.
An acid having only one hydrogen atom that can be replaced by a metal or a positive radical.
monobasic acid
A pictorial representation of the atomic arrangement of a molecule.
structural (graphic) formula
polar molecule
A molecule that has differently charged areas because of unequal sharing of electrons.
A unit of weight in the metric system.
gram
boiling point
The temperature at which the vapor pressure of a liquid equals the atmospheric pressure.
fluoridation
Addition of small amounts of fluoride (usually NaF) to drinking water to help prevent tooth decay.
isotopes
Two or more forms of an element that differ only in the number of neutrons in the nucleus and hence in their mass numbers.
A chemical reaction that removes oxygen from a substance.
reduction
nascent (atomic)
Referring to an element in the atomic form as it has just been liberated in a chemical reaction.
One thousandth of a millimeter.
micron (abbreviation: µ)
hydroponics
Growing plants without the use of soil, as in nutrient solution or in sand irrigated with nutrient solution.
gram
A unit of weight in the metric system; the weight of 1 milliliter of water at 4ºC (abbreviation: g).
significant figures
All the certain digits, that is, those recorded in a measurement, plus one uncertain digit.
A chemical, such as aluminum sulfate, used for fixing colors on textiles.
mordant
fuel cell
A device for converting an ordinary fuel such as hydrogen or methane directly into electricity.
double displacement
A reaction in which two chemical substances exchange ions with the formation of two new compounds.
calorimeter
An instrument used to measure the amount of heat liberated or absorbed during a change.
The capacity to do work.
energy (In every chemical change energy is either given off or taken in. Forms of energy are heat, light, motion, sound, and electrical, chemical, and nuclear energy.)
proton
A subatomic particle found in the nucleus that has a positive charge.
stable
Referring to a substance not easily decomposed or dissociated.
A process in which ammonia or a cyanide is used to produce case-hardened steel; a nitride is formed instead of a carbide.
nitriding
A property of a solution that depends primarily on the concentration, not the type, of particles present.
colligative property
Avogadro’s law
Equal volumes of gases under identical conditions of temperature and pressure contain equal numbers of particles (atoms, molecules, ions, or electrons).
An acid (or a base) capable of a high degree of ionization in water solution.
strong acid (or base) Example: sulfuric acid (sodium hydroxide).
manometer
A U-tube (containing mercury or some other liquid) used to measure the pressure of a confined gas.
A nuclear reaction that releases energy because of the union of smaller nuclei to form larger ones.
fusion
A dye that shows one color in the presence of the hydrogen ion (acid) and a different color in the presence of the hydroxyl ion (base).
indicator
A substitutent obtained from a saturated hydrocarbon by removing one hydrogen atom.
alkyl
metallurgy
The process involved in obtaining a metal from its ores.
Referring to any substance that has basic properties.
alkaline
alkyl
A substitutent obtained from a saturated hydrocarbon by removing one hydrogen atom. Examples methyl (CH3-), ethyl (C2H5-)
Any gas that obeys the gas laws perfectly.
Ideal Gas law (No such gas actually exists.)
A term applied to methods and procedures used to determine any or all of the constituent parts of a substance.
qualitative analysis
solution
A uniform mixture of a solute in a solvent.
recrystallization
A series of crystallizations, repeated for the purpose of greater purification.
heat of fusion
The amount of heat, in calories, required to melt 1 gram of a solid; for water, 80 calories.
Any substance used to furnish heat by combustion.
fuel
hydroxyl
Referring to the -OH radical.
mordant
A chemical, such as aluminum sulfate, used for fixing colors on textiles.
deliquescence
The absorption by a substance of water from the air, so that the substance becomes wet.
gamma rays
A type of radiation consisting of high-energy waves that can pass through most materials.
transmutation
Conversion of one element into another, either by bombardment or by radioactive disintegration.
ether
An organic compound containing the -O- group.
From an electron standpoint, a substance that loses its valence electrons to another element.
reducing agent
Weak attractive forces existing between molecules.
van der Waals forces
A formula that shows only the simplest ratio of the numbers and kinds of atoms, such as CH4.
empirical formula
meter
The basic unit of length in the metric system; defined as 1,650,763.73 times the wavelength of krypton-86 when excited to give off an orange-red spectral line.
An electrode potential associated with a reduction half-reaction.
reduction potential
cathode rays
Streams of electrons given off by the cathode of a vacuum tube.
positron
A positively charged particle of electricity with about the same weight as the electron.
During electrolysis, the weight of any element liberated is proportional (1) to the quantity of electricity passing through the cell, and (2) to the equivalent weight of the element.
Faraday’s law
coordinate covalence
Covalence in which both electrons in a pair come from the same atom.
evaporation
The process in which molecules of a liquid (or a solid) leave the surface in the form of vapor.
nonpolar compound
A compound in whose molecules the atoms are arranged symmetrically so that the electric charges are uniformly distributed.
half-life
The time required for half of the mass of a radioactive substance to disintegrate.
Large, complex organic molecules, with nitrogen an essential part, found in plants and animals.
proteins
The minimum energy necessary to start a reaction.
activation energy
One of the “building blocks” of proteins; contains one or more NH2- groups that have replaced the same number of hydrogen atoms in an organic acid.
amino acid
theory
An explanation used to interpret the “mechanics” of nature’s actions; a theory is more fully developed than a hypothesis.
cation
An ion that has a positive charge.
spontaneous combustion (ignition)
The process in which slow oxidation produces enough heat to raise the temperature of a substance to its kindling temperature.
The process of combining several molecules to form one large molecule (polymer)
polymerization
In nucleonics: the concentration of nuclear particles or rays.
flux
Capable of being softened by heat; may be remolded.
thermoplastic
A unit of pressure defined as 1 millimeter of mercury.
torr (1 torr equals 133.32 pascals)
A possible explanation of the nature of an action or phenomenon.
hypothesis (A hypothesis is not as completely developed as a theory.)
molecular mass
The sum of the masses of all the atoms in a molecule a substance.
Defined as -log[H+] where [H+] is the concentration of hydrogen ions, in moles per liter.
pH
esterification
A chemical reaction between an alcohol and an acid, in which an ester is formed.
chemistry
The science concerned with the compositions of substances and the changes they undergo.
hydrolysis
Of carbohydrates: the action of water in the presence of a catalyst upon one carbohydrate to form simpler carbohydrates. Of salts: a reaction involving the splitting of water into it ions by the formation of a weak acid, a weak base, or both.
The breaking down of a compound into two or more simpler substances.
analysis
The ratio between the mass of a certain volume of a substance and the mass of an equal volume of water (or, in the case of gases, an equal volume of air); expressed as a single number.
specific gravity (mass)
A substance composed of elements chemically united in definite proportions by weight.
compound
melting
The change in phase of a substance from solid to liquid.
emulsifying agent
A colloidal substance that forms a film about the particles of two immiscible liquids, so that one liquid remains suspended in the other.
The temperature at which the vapor pressure of a liquid equals the atmospheric pressure.
boiling point
aromatic compound
A compound whose basic structure contains the benzene ring; it usually has a odor.
absolute temperature
Temperature measured on the absolute scale, which has its origin at absolute zero. (See also Kelvin scale.)
liquid air
Air that has been cooled and compressed until it liquifies.
The electrons in the outermost level or levels of an atom that determine its chemical properties.
valence electrons
The process of forming definitely shaped crystals when water is evaporated from a solution of the substance.
crystallization
High-speed, negatively charged electrons emitted in radiation.
beta particles
The image formed when radiant energy is dispersed by a prism or grating into its various wavelengths.
spectrum
A compound derived from another compound by the removal of water; it will combine with water to form an acid (acidic anhydride) or a base (basic anhydride).
anhydride
polar dot structure
Representation of the arrangements of electrons around the atoms of a molecule in which the polar characteristics are shown by placing the electrons closer to the more electronegative atom.
amino acid
One of the “building blocks” of proteins; contains one or more NH2- groups that have replaced the same number of hydrogen atoms in an organic acid.
acid salt
A salt formed by replacing part of the hydrogen ions of a dibasic or tribasic acid with metallic ions. Examples NaHS04, NaH2PO4.
Any process by which atmospheric nitrogen is converted into a compound such as ammonia or nitric acid.
nitrogen fixation
The process of heating an organic substance, such as coal, in the absence of air to break it down into solid and volatile products.
destructive distillation
The bending of light rays as they pass from one material into another.
refraction (of light)
hydrogen bond
A weak chemical linkage between the hydrogen of one polar molecule and the oppositely charged portion of a closely adjacent molecule.
Covalence in which both electrons in a pair come from the same atom.
coordinate covalence
entropy
The measure of the randomness or disorder that exists in a system.
absorption
The process of taking up by capillary, osmotic, chemical, or solvent action, as a sponge absorbs water.
Referring to the inability of two liquids to mix.
immiscible
neutralization
The union of the hydrogen ion of an acid and the hydroxyl ion of a base to form water.
Changing a solid to the liquid state by heating.
fusion melting
stratosphere
The upper portion of the atmosphere, in which the temperature changes but little with altitude, and clouds of water never form.
hygroscopic
Referring to the ability of a substance to draw water vapor from the atmosphere to itself and become wet.
The rearrangement of atoms in a molecule to form isomers.
isomerization
The process in which ions are formed from neutral atoms.
ionization
galvanizing
Applying a coating of zinc to iron or steel to protect the latter from rusting.
effusion
The flow of a gas through a small aperture.
A change that doe not involve any alteration in chemical composition.
physical change
A complex mixture of gaseous, liquid, and solid hydrocarbons obtained from Earth.
petroleum (meaning “oil from stone”)
The smallest particle of an element that retains the properties of that element and can enter into a chemical reaction.
atom
Any reaction that reaches an equilibrium, or that can be made to proceed from right to left as well as from left to right.
reversible reaction
nucleus
The center of the atom, which contains protons and neutrons.
Celsius scale
A temperature scale divided into 100 equal divisions and based on water freezing at 0º and boiling at 100º. Synonymous with centigrade.
compound
A substance composed of elements chemically united in definite proportions by weight.
E = mc^2
Einstein equation. Which relates mass to energy; E = energy in ergs, m = mass in grams, and c = velocity of light, 3x10^10 centimeters/second.
A suspension of fine particles or droplets of one liquid in another, the two liquids being immiscible in each other.
emulsion
cyclotron
A device used to accelerate charged particles to high energies for bombarding the nuclei of atoms.
specific heat
The ratio between the number of calories needed to raise the temperature of a certain mass of a substance 1 degree on the Celsius scale and the number of calories needed to raise the temperature of the same mass of water 1 degree on the Celsius scale.
gram-formula weight
The formula weight, in grams, of a substance.
reduction potential
An electrode potential associated with a reduction half-reaction.
The rapid escape of excess gas that has been dissolved in a liquid.
effervescence
A colloidal substance that forms a film about the particles of two immiscible liquids, so that one liquid remains suspended in the other.
emulsifying agent
The science concerned with the compositions of substances and the changes they undergo.
chemistry
ozone
An allotropic and very active form of oxygen, having the formula O3.
The quantity of heat, in calories, needed to raise the temperature of 1 gram of a substance 1 degree on the Celsius scale.
heat capacity or specific heat
critical temperature
The temperature above which no gas can be liquefied, regardless of the pressure applied.
solid
A phase of matter that has a definite size and shape.
halogen
Any of the five nonmetallic elements (fluorine, chlorine, bromine, iodine, astatine) that form part of Group 17 of the Periodic Table.
A unit of quantity that consists of 6.02x10^23 particles.
mole
alpha particles
Positively charged helium nuclei.
An organic compound that contains the -COOH group.
organic acid
Alike in structure.
homologous
fission
A nuclear reaction that releases energy because of the splitting of large nuclei into smaller ones.
relative atomic mass
(Also atomic mass or atomic weight.) The average mean value of the isotopic masses of the atoms of an element. It indicates the relative mass of the element as compared with that of carbon-12, which is assigned a mass of exactly 12 atomic mass units.
An ion or particle that has a negative charge and thus is attracted to a positively charged anode.
anion
An alcoholic solution of a substance.
tincture (Such as a tincture of iodine.)
amine
A compound such as CH3NH2, derived from ammonia by substituting one or more hydrocarbon radicals for hydrogen atoms.
A salt in which all the hydrogen of the acid has been displaced by a metal.
normal salt
Graham’s law
The rate of diffusion (or effusion) of a gas is inversely proportional to the square root of its molecular mass.
A reaction produced during nuclear fission when at least one neutron from each fission produces another fission, so that the process becomes self-sustaining without additional external energy.
chain reaction
pile
A general term for a nuclear reactor; specifically, a graphite-moderated reactor in which uranium fuel is distributed through a “pile” of graphite blocks.
The amount of heat needed to raise the temperature of 1 kilogram of water 1 degree on the Celsius scale.
kilocalorie
heat
A form of molecular energy; it passes from a warmer body to a cooler one.
zeolite
A natural or synthesized silicate used to soften water.
The process of losing electrons.
oxidation
A single kind of matter, element, or compound.
substance
gas
A phase of matter that has neither definite shape nor definite volume.
A unit of electrical potential or voltage, equal to the difference of potential between two points in a conducting wire carrying a constant current of 1 ampere when the power dissipated between these two points is equal to 1 watt (abbreviation: V).
volt
An instrument, invented by Torricelli in 1643, used for measuring atmospheric pressure.
barometer
Tyndall effect
The scattering of a beam of light as it passes through a colloidal material.
An organic substance, obtained from the lichen plant and used as an indicator; it turns red in acidic solution and blue in basic solution.
litmus
A substance able to withdraw water from another substance, thereby drying it.
dehydrating agent
Brownian movement
Continuous zigzagging movement of colloidal particles in a dispersing medium, as viewed through an ultramicroscope.
fixation of nitrogen
Any process for converting atmospheric nitrogen into compounds, such as ammonia and nitric acid.
exothermic
Referring to a chemical reaction that results in the giving off of heat to its surroundings.
Any of a group of rare gases (helium, neon, argon, krypton, xenon, and radon) that exhibit great stability and very low reaction rates.
noble gas
The nearest whole number to the combined atomic mass of the individual atoms of an isotope when tat mass is expressed in atomic mass units.
mass number
bonding
The union of atoms to form compounds or molecules by filling their outer shells of electrons. This can be done through giving and taking electrons (ionic) or by sharing electrons (covalent).
The absorption by a substance of water from the air, so that the substance becomes wet.
deliquescence
The sum of the masses of all the atoms in a molecule a substance.
molecular mass
In soldering: a substance that cleans the surface of the metal to be soldered.
flux
atomic energy
(More accurately: nuclear energy.) The energy released by spontaneously or artificially produced fission, fusion, or disintegration of the nuclei of atoms.
U.S.P. (United States Pharmacopeia) chemicals
Chemicals certified as having a standard of purity that demonstrates their fitness for use in medicine.
An acid that contains three replaceable hydrogen atoms in its molecule, such as H3PO4.
tribasic acid
The process of taking up by capillary, osmotic, chemical, or solvent action, as a sponge absorbs water.
absorption
The principle that states that an electron occupies the lowest energy orbital that can receive it.
Aufbau Principle
A unit for expressing the kinetic energy of subatomic particles.
electron volt
The ratio between the combining volumes of gases and the product, if gaseous, can be expressed in small whole numbers.
Gay-Lussac’s law or Combining Volumes law
A device for converting an ordinary fuel such as hydrogen or methane directly into electricity.
fuel cell
noble gas
A gaseous element that has a complete outer level of electrons; any of a group of rare gases (helium, neon, argon, krypton, xenon, and radon) that exhibit great stability and very low reaction rates.
If a stress is placed on a system in equilibrium, the system will react in the direction that relieves the stress.
Le Chatelier’s Principle
roasting
Heating an ore (usually a sulfide) in an excess of air to convert the ore to an oxide, which can then be reduced.
Ethyl alcohol that has been “poisoned” in order to produce (by avoiding federal tax) a cheaper alcohol for industrial purposes.
denatured alcohol
erg
A unit of energy or work done by a force of 1 dyne (1/980 g of force) acting through a distance of 1 centimeter; equals 2.4 x 10^-11 kilocalorie.
pascal
The SI unit of pressure, equal to 1 newton per square meter.
The branch of chemistry dealing with carbon compounds, usually those found in nature.
organic chemistry
nonelectrolyte
A substance whose solution does not conduct a current of electricity.
electron
A negatively charged particle found outside the nucleus of the atom; it has a mass of 9.109 x 10^-28 gram.
temperature
The intensity or degree of heat of a body, measured by a thermometer.
torr
A unit of pressure defined as 1 millimeter of mercury; 1 torr equals 133.32 pascals.
ketone
An organic compound containing the -CO- group.
Partial sterilization of a substance, such as milk, by heating to approximately 65ºC for 1/2 hour.
pasteurization
hydride
Any binary compound containing hydrogen, such as HCl.
A letter or letters representing an element of the periodic table.
symbol (Examples: O, Mn.)
fuel
Any substance used to furnish heat by combustion. (See also nuclear fuel.)
calorie
A unit of heat; the amount of heat needed to raise the temperature of 1 gram of water 1 degree on the Celsius scale.
anode
The electrode in an electrolytic cell that has a positive charge and attracts negative ions.
The separation of the components in a mixture of dissolved solids by evaporation according to individual solubilities.
fractional crystallization
physical property
A property of substance arrived at through observation of its smell, taste, color, density, and so on, which does not relate to chemical activity.
A compound that has water molecules included in its crystalline makeup.
hydrate
flux
In metallurgy: a substance that helps to melt and remove the solid impurities as slag. In soldering: a substance that cleans the surface of the metal to be soldered. In nucleonics: the concentration of nuclear particles or rays.
X-rays
Penetrating radiations, of extremely short wavelength, emitted when a stream of electrons strikes a solid target in a vacuum tube.
The material that is dissolved to make a solution.
solute
The quantity of heat needed to vaporize 1 gram of a liquid at constant temperature and pressure; for water at 100ºC, 540 calories.
heat of vaporization
amphoteric
Referring to a hydroxide that may have either acidic or basic properties, depending on the substance with which it reacts.
The separation of the ions of an ionic compound due to the action of a solvent.
dissociation
Bonding accomplished through the sharing of electrons so that atoms can fill their outer shells.
covalent bonding
nuclear energy
The energy released by spontaneously or artificially produced fission, fusion, or disintegration of the nuclei of atoms.
hydrate
A compound that has water molecules included in its crystalline makeup.
pi bond
A bond between p orbitals.
precipitate
An insoluble compound formed in the chemical reaction between two or more substances in solution.
oxidation
The chemical process by which oxygen is attached to a substance; the process of losing electrons.
The ratio, expressed in percent, between the amount of water vapor in a given volume of air and the amount the same volume can hold when saturated at the same temperature.
relative humidity
gram-atomic mass
The atomic mass, in grams, of an element.
A substance that speeds up or slows down a reaction without being permanently changed itself.
catalyst
dipole-dipole attraction
A relatively weak force of attraction between polar molecules; a component of van der Waals forces.
work
The product of the force exerted on a body and the distance through which the force acts; expressed mathematically by the equation W = Fs, where W = work, F = force, and s = distance.
heat of formation
The quantity of heat either given off or absorbed in the formation of 1 mole of a substance from its elements.
An alloy of copper and zinc.
brass
The weakest of the van der Waals forces between molecules. These weak, attractive forces become apparent only when the molecules approach one another closely (usually at low temperatures and high pressure). They are due to the way the positive charges of one molecule attract the negative charges of another molecule because of the charge distribution at any one instant.
London force
humidity
The amount of moisture in the air.
neutron capture
A nuclear reaction in which a neutron attaches itself to a nucleus; a gamma ray is usually emitted simultaneously.
An elementary particle.
lepton (The electron and neutrino are believed to consist of leptons.)
ionic equation
An equation showing a reaction among ions.
denatured alcohol
Ethyl alcohol that has been “poisoned” in order to produce (by avoiding federal tax) a cheaper alcohol for industrial purposes.
electrolysis
The process of separating the ions in a compound by means of electrically charged poles.
redox
A shortened name for a reaction that involves reduction and oxidation.
The amount of heat, in calories, required to melt 1 gram of a solid; for water, 80 calories.
heat of fusion
colligative property
A property of a solution that depends primarily on the concentration, not the type, of particles present.
Depositing a thin layer of (usually) a metallic element on the surface of another metal by electrolysis.
electroplating
molecule
The smallest particle of a substance that retains the physical and chemical properties of that substance. Examples: He, BR2, H2O
A solution that contains 1 gram of H+ (or its equivalent: 17g of OH-, 23g of Na+, 20g of Ca2+, etc.) in 1 letter of solution (indicated by N).
normal solution
atomic mass
(Also relative atomic mass or atomic weight.) The average mean value of the isotopic masses of the atoms of an element. It indicates the relative mass of the element as compared with that of carbon-12, which is assigned a mass of exactly 12 atomic mass units.
molal solution
A solution containing 1 mole of solute in 1,000 grams of solvent (indicated by m).
micron
One thousandth of a millimeter (abbreviation: µ).
An organic compound formed by dehydrating oxidized alcohol; contains the characteristic -CHO group.
aldehyde
reagent
Any chemical taking part in a reaction.
An organic compound containing the -O- group.
ether
reducing agent
From an electron standpoint, a substance that loses its valence electrons to another element; a substance that is readily oxidized.
joule
The SI unit of work or of energy equal to work done; 1 joule = 0.2388 calorie; 1 calorie = 4.18 joule.
monobasic acid
An acid having only one hydrogen atom that can be replaced by a metal or a positive radical.
Faraday’s law
During electrolysis, the weight of any element liberated is proportional (1) to the quantity of electricity passing through the cell, and (2) to the equivalent weight of the element.
formula
An expression that uses the symbols for elements and subscripts to show the basic makeup of a substance.
To take water from a substance.
dehydrate
allotropic forms
Forms of the same element that differ in their crystalline structures.
A process in which hydrogen is made to combine with another substance, usually organic, in the presence of a catalyst.
hydrogenation
A solution containing 1 mole of solute in 1,000 milliliters of solution (indicated by M).
molar solution
One of more than 100 “building blocks” of which all matter is composed. An element consists of atoms of only one kind and cannot be decomposed further by ordinary chemical means.
element
The measure of the randomness or disorder that exists in a system.
entropy
acidic anhydride
A nonmetallic oxide that, when placed in water, reacts to form an acid solution.
Conservation of Matter law
Matter can be neither created nor destroyed (or weight remains constant in an ordinary chemical change).
An isotope that is radioactive, such as uranium-235.
radioisotope
heat of vaporization
The quantity of heat needed to vaporize 1 gram of a liquid at constant temperature and pressure; for water at 100ºC, 540 calories.
lanthanide series
The “rare earth” series of elements starting with lanthanum, No. 57, and ending with lutetium, No. 71.
The temperature scale that has 32º as the freezing point of water and 212º as the boiling point.
Fahrenheit scale
A substance involved in a reaction.
reactant
D20
(Also deuterium oxide, heavy water) Water in which the hydrogen atoms are replaced by the atoms of the isotope of hydrogen, deuterium.
A substance composed of two or more metals, which are intimately mixed; usually made by melting the metals together.
alloy
reaction potential
The same of the oxidation potential and reduction potential for a particular reaction.
A substance that is consumed during nuclear fission or fusion.
nuclear fuel
The emission of particles and rays from a radioactive source; usually alpha and beta particles and gamma rays.
radiation
dehydrate
To take water from a substance.
Referring to the ability of two liquids to mix with one another.
miscible
homogeneous
Uniform; having every portion exactly like every other portion.
A mixture of finely divided solid material in a liquid, from which the solid settles on standing.
suspension
mass spectograph
A device for determining the masses of electrically charged particles by separating them into distinct streams by means of magnetic deflection.
A substance whose solution does not conduct a current of electricity.
nonelectrolyte
Referring to a hydroxide that may have either acidic or basic properties, depending on the substance with which it reacts.
amphoteric
Referring to series of organic compounds, such as hydrocarbons, in which each member differs from the next by the addition of the same group.
homologous
fractional crystallization
The separation of the components in a mixture of dissolved solids by evaporation according to individual solubilities.
The amount of heat needed to raise the temperature of 1 gram of water 1 degree on the Celsius scale.
calorie
The reaction taking place in all green plants that produces glucose from carbon dioxide and water under the catalytic action of chlorophyll in the presence of light.
photosynthesis
formula mass
The sum of the atomic mass units of all the atoms (or ions) contained in a formula.
The time required for half of the mass of a radioactive substance to disintegrate.
half-life
solute
The material that is dissolved to make a solution.
A group of atoms that characterizes certain types of organic compounds, such as -OH for alcohols, and that reacts more or less independently.
functional group
functional group
A group of atoms that characterizes certain types of organic compounds, such as -OH for alcohols, and that reacts more or less independently.
Capable of being permanently hardened by heat and pressure; resistant to the further effects of heat.
thermosetting
A compound made up of a positive metallic ion and a negative nonmetallic ion or radical.
salt (such as NaCl)
The temperature to which a given substance must be raised before it ignites.
kindling temperature
An equation that includes values for the calories absorbed or evolved.
thermochemical equation
value of the electron volt
1.6 x 10^-12 erg or 23.1 kilocalories/mole (abbreviation: eV).
hydrogenation
A process in which hydrogen is made to combine with another substance, usually organic, in the presence of a catalyst.
The methane series of hydrocarbons.
paraffin series
atomic weight
(Also relative atomic mass or atomic mass.) The average mean value of the isotopic masses of the atoms of an element. It indicates the relative mass of the element as compared with that of carbon-12, which is assigned a mass of exactly 12 atomic mass units.
In a nuclear reactor, a rod of a certain metal such as cadmium, which controls the speed of the chain reaction by absorbing neutrons.
control rod
The amount of three-dimensional space occupied by a substance.
volume
Representation of the arrangements of electrons around the atoms of a molecule in which the polar characteristics are shown by placing the electrons closer to the more electronegative atom.
polar dot structure
A water solution that contains an excess of hydroxide ions; a proton acceptor; a base turns litmus paper blue and neutralizes acids to form salts.
base
An element whose oxide reacts with water to form an acid.
nonmetal
polymerization
The process of combining several molecules to form one large molecule (polymer). (a) Additional polymerization: The addition of unsaturated molecules to each other. (b) Condensation polymerization: The reaction of two molecules by loss of a molecule of water.
isomerization
The rearrangement of atoms in a molecule to form isomers.
distillation
The process of first vaporizing a liquid and then condensing the vapor back into a liquid, leaving behind the nonvolatile impurities.
A product formed by the substitution of other elements or radicals for hydrogen atoms in hydrocarbons.
substitution product
Of salts: a reaction involving the splitting of water into it ions by the formation of a weak acid, a weak base, or both.
hydrolysis
mixture
A substance composed of two or more components, each of which retains its own properties.
filtration
The process by which suspended matter is removed from a liquid by passing the liquid through a porous material.
A property of substance arrived at through observation of its smell, taste, color, density, and so on, which does not relate to chemical activity.
physical property
sigma bond
A bond between s orbitals or between an s orbital and another kind of orbital.
group
A vertical column of elements in the periodic table that generally has similar properties.
colloids
Particles larger than those found in a solution but smaller than those in a suspension.
Referring to a chemical reaction that results in the giving off of heat to its surroundings.
exothermic
tracer
A minute quantity of radioactive isotope used in medicine and biology to study chemical changes within living tissues.
Charles’s law
The volume of a confined gas is directly proportional to the absolute temperature, provided that the pressure remains the same.
organic acid
An organic compound that contains the -COOH group.
tempering
The heating and then rapid cooling of a metal to increase its hardness.
Gibbs free energy
Changes in Gibbs free energy, ∆G, are useful in indicating the conditions under which a chemical reaction will occur. The equation is ∆G = ∆H -T∆S, where ∆H = change in enthalpy and ∆S = change in entropy. If ∆G is negative, the reaction will proceed spontaneously to equilibrium. (Also called free energy.)
A chemical action in which both heat and light are given off.
combustion
A series of crystallizations, repeated for the purpose of greater purification.
recrystallization
substance
A single kind of matter, element, or compound.
When any two elements, A and B, combine to form more than one compound, the different masses of B that unite with a fixed mass of A bear a small whole-number ratio to each other.
Multiple Proportions law
resonance
The phenomenon in a molecular structure that exhibits properties between those of a single bond and those of a double bond and thus possesses two or more alternative structures.
Any binary compound containing hydrogen, such as HCl.
hydride
activated charcoal
A specially treated and finely divided form of carbon, which possesses a high degree of adsorption.
fractional distillation
The separation of the components in a mixture of liquids having different boiling points by vaporization.
nitriding
A process in which ammonia or a cyanide is used to produce case-hardened steel; a nitride is formed instead of a carbide.
A uniform mixture of a solute in a solvent.
solution
deuterium oxide
(Also heavy water, D2O) Water in which the hydrogen atoms are replaced by the atoms of the isotope of hydrogen, deuterium.
Capable of being easily set of fire.
flammable or combustible or inflammable
The upper portion of the atmosphere, in which the temperature changes but little with altitude, and clouds of water never form.
stratosphere
alkaline
Referring to any substance that has basic properties.
Positively charged helium nuclei.
alpha particles
Referring to a substance not easily decomposed or dissociated.
stable
catalyst
A substance that speeds up or slows down a reaction without being permanently changed itself.
atomic mass unit
One twelfth of the mass of a carbon-12 atom; equivalent to 1.660531 x 10^-27 kilogram (abbreviation: amu or µ).
vapor
The gaseous phase of a substance that normally exists as a solid or liquid at ordinary temperatures.
eudiometer
A graduated glass tube into which gases are placed and subjected to an electric spark; used to measure the individual volumes of combining gases.
The theory that all molecules are in motion; this motion is most rapid in gases, less rapid in liquids, and very slow in solids.
Kinetic-Molecular Theory
polar covalent bond
A bond in which electrons are closer to one atom than to another. See also polar molecule.
A substance that (a) gives up its oxygen readily, (b) removes hydrogen from a compound, (c) takes electrons from an element.
oxidizing agent
An acid (or base) capable of being only slightly ionized in an aqueous solution.
weak acid (or base) Example: acetic acid (ammonium hydroxide).
The SI unit of work or of energy equal to work done,
joule (1 joule = 0.2388 calorie; 1 calorie = 4.18 joule.)
Referring to a compound composed of three different elements, such as H2SO4.
ternary
combustion
A chemical action in which both heat and light are given off.
The highest temperature at which water vapor condenses out of the air.
dew point
substitution product
A product formed by the substitution of other elements or radicals for hydrogen atoms in hydrocarbons.
Two or more compounds having the same percentage composition but different arrangements of atoms in their molecules and hence different properties.
isomers
If a series of reactions are added together, the enthalpy change for the total reaction is the sum of the enthalpy changes for the individual steps.
Hess’s law
mineral
An inorganic substance of definite composition found in nature.
atomic radius
One-half the distance between adjacent nuclei in the crystalline or solid phase of an element; the distance from the atomic nucleus to the valence electrons.
molar solution
A solution containing 1 mole of solute in 1,000 milliliters of solution (indicated by M).
homologous
Alike in structure; referring to series of organic compounds, such as hydrocarbons, in which each member differs from the next by the addition of the same group.
fusion melting
Changing a solid to the liquid state by heating.
An instrument used to analyze light by separating it into its component wavelengths.
spectroscope
specific heat
(Also heat capacity.) The quantity of heat, in calories, needed to raise the temperature of 1 gram of a substance 1 degree on the Celsius scale.
Particles larger than those found in a solution but smaller than those in a suspension.
colloids
The energy released by spontaneously or artificially produced fission, fusion, or disintegration of the nuclei of atoms.
nuclear energy
carbon dating
The use of radioactive carbon-14 to estimate the ages of ancient materials, such as archeological or paleontological specimens.
water of hydration
Water that is held in chemical combination in a hydrate and can be removed without essentially altering the composition of the substance. See also hydrate.
A bond between p orbitals.
pi bond
The measure of the force with which a body is attracted toward Earth by gravity.
weight
A water solution that has an excess of hydrogen ions; an acid turns litmus paper pink or red, has a sour taste, and neutralizes bases to form salts.
acid
The series of radioactive elements starting with actinium, No. 89, and ending with lawrencium, No. 103.
actinide series
The smallest amount of fissionable material that will sustain a chain reaction.
critical mass
First Law of Thermodynamics
The total energy of the universe is constant and cannot be created or destroyed.
standard conditions
An atmospheric pressure of 760 millimeters or torr or 1 atmosphere (mercury pressure) and a temperature of 0ºC (273 K) (abbreviation: STP).
valence
The combining power of an element; the number of electrons gained, lost, or borrowed in a chemical reaction.
The volume of a confined gas is inversely proportional to the pressure to which it is subjected, provided that the temperature remains the same.
Boyle’s law
Defined as 1,650,763.73 times the wavelength of krypton-86 when excited to give off an orange-red spectral line.
meter
Henry’s law
The solubility of a gas (unless the gas is very soluble) is directly proportional to the pressure applied to the gas.
actinide series
The series of radioactive elements starting with actinium, No. 89, and ending with lawrencium, No. 103.
A cell in which electrolysis is carried out.
electrolytic cell
The energy acquired by an electron when it is accelerated by a potential difference of 1 volt.
electron volt
The process of separation of a solution by diffusion through a semipermeable membrane.
dialysis
A gaseous element that has a complete outer level of electrons.
noble gas
alkali
Usually, a strong base, such as sodium hydroxide or potassium hydroxide.
The product of the force exerted on a body and the distance through which the force acts.
work
The scattering of a beam of light as it passes through a colloidal material.
Tyndall effect
A general term for a nuclear reactor; specifically, a graphite-moderated reactor in which uranium fuel is distributed through a “pile” of graphite blocks.
pile
pasteurization
Partial sterilization of a substance, such as milk, by heating to approximately 65ºC for 1/2 hour.
crystallization
The process of forming definitely shaped crystals when water is evaporated from a solution of the substance.
A bond between s orbitals or between an s orbital and another kind of orbital.
sigma bond
A massive variety of uraninite that contains a small amount of radium.
pitchblende
electrode potential
The difference in potential between an electrode and the solution in which it is immersed.
weight
The measure of the force with which a body is attracted toward Earth by gravity.
Second Law of Thermodynamics
Heat cannot, of itself, pass from a cold body to a hot body.
neutron
A subatomic particle found in the nucleus of the atom; it has no charge and has the same mass as the proton.
ternary
Referring to a compound composed of three different elements, such as H2SO4.
The number that indicates the order of an element in the periodic system; numerically equal to the number of protons in the nucleus of the atom, or the number of negative electrons located outside the nucleus of the atom.
atomic number
Forms of the same element that differ in their crystalline structures.
allotropic forms
A specially treated and finely divided form of carbon, which possesses a high degree of adsorption.
activated charcoal
dialysis
The process of separation of a solution by diffusion through a semipermeable membrane.
A chemical transformation or change. The four basic types are combination (synthesis), decomposition (analysis), single replacement or single displacement, and double replacement or double displacement.
reaction
electrolytic cell
A cell in which electrolysis is carried out.
A solution that contains a greater quantity of solute than is normally possible at a given temperature.
supersaturated solution
A relatively weak force of attraction between polar molecules; a component of van der Waals forces.
dipole-dipole attraction
The modernized metric system of measurements universally used by scientists.
Systeme International d’Unites (There are seven base units: kilogram, meter, second, ampere, kelvin, mole, and candela.)
The quantity of heat either given off or absorbed in the formation of 1 mole of a substance from its elements.
heat of formation
luminous
Emitting a steady, suffused light.
melting point
The specific temperature at which a given solid changes into a liquid.
An insoluble compound formed in the chemical reaction between two or more substances in solution.
precipitate
The property of matter whereby it remains at rest or, if in motion, remains in motion in a straight line unless acted upon by an outside force.
inertia
fusion
A nuclear reaction that releases energy because of the union of smaller nuclei to form larger ones.
fallout
The residual radioactivity from an atmospheric nuclear test, which eventually settles on the surface of Earth.
Water that is held in chemical combination in a hydrate and can be removed without essentially altering the composition of the substance.
water of hydration
moderator
A substance such as graphite, paraffin, or heavy water used in a nuclear reactor to slow down neutrons.
buffer
A substance that, when added to a solution, makes changing the pH of the solution more difficult.
A solution that contains the maximum amount of solute under the existing temperature and pressure.
saturated solution
The heating and then rapid cooling of a metal to increase its hardness.
tempering
