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glossary of chemistry terms is a list of terms and definitions relevant to chemistry, including chemical laws, diagrams and formulae, laboratory tools, glassware, and equipment. Chemistry is a physical science concerned with the composition, structure, and properties of matter, as well as the changes it undergoes during chemical reactions; it has an extensive vocabulary and a significant amount of jargon.
Note: All periodic table references refer to the IUPAC Style of the Periodic Table.
absolute zero A
theoretical condition concerning a system at zero kelvin, where a system does not emit or absorb energy (all atoms are at rest).
accuracy How close a measured value is to the actual or true value. Compare
acid A compound that, when dissolved in
water, gives a pH of less than 7.0 or a compound that donates a hydrogen ion.
acid anhydride a compound with two
acyl groups bound to a single oxygen atom
acid dissociation constant A quantitative measure of the strength of an
acid in solution expressed as an equilibrium constant for a chemical dissociation reaction in the context of acid-base reactions. It is generally denoted by the symbol K. Also called a acid ionization constant or acidity constant.
periodic series of metallic elements with atomic numbers 89 to 103, from actinium through lawrencium. Also called actinoids.
activated complex A structure that forms because of a collision between molecules while new bonds are formed.
activation energy The minimum
energy which must be available to a chemical system with potential reactants in order to result in a chemical reaction.
acyclic Containing only linear structures of atoms (particularly in
addition reaction In organic chemistry, when two or more molecules combine to make a larger one.
adhesion The tendency of dissimilar particles or surfaces to cling to one another as a result of
intermolecular forces. Compare . cohesion
aeration The mixing of air into a
liquid or a solid.
organic compound consisting of a hydroxyl functional group attached to a saturated carbon atom.
aldehyde Any organic compound consisting of a
carbonyl group attached to a hydrogen atom and any other R-group.
alkali metal Any of the metallic
elements belonging to Group 1 of the periodic table: lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr).
alkaline earth metal Any of the metallic
elements belonging to Group 2 of the periodic table: beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).
alkane Any saturated acyclic
alkene An unsaturated hydrocarbon containing at least one pair of
alkyl group A functional group consisting of an
alkane missing a hydrogen atom.
alkyne An unsaturated hydrocarbon containing at least one pair of
allomer A substance that differs in chemical composition but has the same
crystalline structure as another substance.
allotrope Elements that can have different structures (and therefore different forms), such as
carbon ( diamonds, graphite, and fullerene).
mixture of metals or of a metal and another element which in combination exhibit a metallic bonding character. Common examples include bronze, brass, and pewter.
amplitude The maximum distance that the particles of the medium carrying the wave move away from their rest position.
anion A negatively charged
anode 1) An
electrode through which the conventional electric current (the flow of positive charges) enters into a polarized electrical circuit; 2) the wire or plate of an electrochemical cell having an excess positive charge. Negatively charged anions always move toward the anode. Compare . cathode
aqueous solution A
solution in which the solvent is water. It is denoted in chemical equations by appending (aq) to a chemical formula.
aromaticity A chemical property of conjugated rings of atoms, such as
benzene, which results in unusually high stability.
atom A chemical element in its smallest form, made up of
protons and neutrons within the nucleus and electrons circling the nucleus.
atomic mass The
mass of an atom, typically expressed in unified atomic mass units and nearly equivalent to the mass number.
atomic mass unit See
. unified atomic mass unit
atomic number The number of
protons found in the nucleus of an atom of a given chemical element. It is identical to the charge number of the nucleus and is used in the periodic table to uniquely identify each chemical element. Also called the proton number.
atomic orbital the region where the electron of the atom may be found
average atomic mass
Avogadro's number The number of particles in one
mole of a substance (6.02 ×10 ). 23
azeotrope A mixture of liquids whose composition is unchanged by
barometer A device used to measure atmospheric pressure.
base A substance that accepts a
proton and has a high pH; a common example is sodium hydroxide (NaOH).
base anhydride Oxides of group I and II metal elements.
biochemistry The study of the chemistry of biological systems and organisms.
boiling point The temperature at which a liquid substance starts to boil.
boiling-point elevation the process where the boiling point is elevated by adding a substance
bond The attraction and repulsion between atoms and molecules that is a cornerstone of chemistry.
Boyle's law for a given mass of gas at constant temperature, the volume varies inversely with the pressure
Brønsted–Lowry acid Any chemical species that readily donates a
Brønsted–Lowry acid–base reaction
Brønsted–Lowry base Any chemical species that readily accepts a
buffered solution An
aqueous solution consisting of a weak acid and its conjugate base or a weak base and its conjugate acid that resists changes in pH when strong acids or bases are added.
burette Glassware used to dispense specific amounts of
liquid when precision is necessary (e.g. titration and resource-dependent reactions). Also called a buret.
calorimeter A device used to measure
catalyst Any element or compound that facilitates an increase in the speed of a
chemical reaction but which is not consumed or destroyed during the reaction. It is considered both a reactant and a product of the reaction.
electrode from which the conventional electric current (the flow of positive charges) exits a polarized electrical circuit. Positively charged cations always move toward the cathode, though the cathode's polarity can be positive or negative depending on the type of electrical device and how it is being operated. Compare . anode
cation A positively charged
centrifuge equipment used to separate substances based on density by rotating the tubes around a centred axis
cell potential the force in a
galvanic cell that pulls electron through reducing agent to oxidizing agent
charge number A
quantized value of electric charge calculated as the electric charge in coulombs divided by the elementary-charge constant, or z = q/e. Charge numbers for ions are denoted in superscript (e.g. Na + indicates a sodium ion with a charge number of positive one). Atomic numbers are charge numbers of atomic nuclei.
Charles's law When the pressure on a sample of a dry gas is held constant, the Kelvin temperature is directly proportional to its volume.
chelation A type of bonding involving the formation of two separate
coordinate covalent bonds between a polydentate ligand and a single central metal ion. The ligand is usually an organic compound called a chelant or chelating agent.
chemical composition The identity and relative number of the
elements that make up a chemical compound, which can often be expressed with a chemical formula.
chemical formula Any of various means of concisely displaying information about the
chemical composition of a compound or molecule using letters, numbers, and/or typographical symbols. Chemical formulas, such as empirical and molecular formulas, can only indicate the identities and numerical proportions of the atoms in a compound and are therefore more limited in descriptive power than chemical names and structural formulas.
chemical law A
law of nature relevant to chemistry, such as the law of conservation of mass.
chemical reaction The change of one or more
substances into another or multiple substances.
chemical substance A form of
matter that has constant chemical composition and characteristic properties and which cannot be separated into simpler components by purely physical methods (i.e. without breaking chemical bonds). It is often called a pure substance to distinguish it from a mixture.
chemistry The scientific discipline that studies
chemical substances, compounds, and molecules composed of atoms of various chemical elements, as well as their composition, structure, properties, behavior, and the changes they undergo during reactions with other substances.
cohesion The tendency of similar particles or surfaces to cling to one another as a result of
intermolecular forces. Compare . adhesion
colligative property A property of
solutions that depends upon the ratio of the number of solute particles to the number of solvent particles in the solution, and not on the nature of the chemical species present.
colloid A mixture of evenly dispersed substances, such as many
exothermic reaction between an oxidant and a fuel that produces large amounts of heat and often light.
Commission on Isotopic Abundances and Atomic Weights (CIAAW)
compression An area in a longitudinal wave where the particles are closer and pushed in.
substance that is made up of two or more chemically bonded elements.
phase transition of a substance from a gas to a liquid.
condosity A comparative measurement of the
electrical conductivity of a solution, defined as the molar concentration of a sodium chloride (NaCl) solution that has the same specific electrical conductance as the solution under test and expressed in units of moles per unit volume.
conductor Any object or material that allows the flow of an
electric current in one or more directions. Compare . insulator
conformation The spatial arrangement of atoms affording distinction between
stereoisomers which can be interconverted by rotations about formally single bonds.
coordinate covalent bond
corrosion An irreversible interfacial
chemical reaction of a material with its environment which results in consumption of the material or dissolution into the material of an external component of the environment.
SI unit of electric charge (symbol: C), defined as the charge transported by a constant current of one ampere in one second.
covalent bond A
chemical bond that involves the sharing of electron pairs between atoms. The stable balance of attractive and repulsive forces that occurs between atoms when they share electrons is known as covalent bonding. A covalent bond is also called a molecular bond.
The diatomic hydrogen molecule, H
(right), is formed by a
when two single hydrogen atoms share two electrons
crest The highest point in a wave.
solid whose constituent particles (such as atoms, ions, or molecules) are arranged in an orderly periodic microscopic structure, forming a lattice that extends in all directions.
cuvette A type of glassware used in
spectroscopic experiments. It is usually made of plastic, glass or quartz and should be as clean and clear as possible.
Dalton's law of partial pressures
deionization The removal of ions, and in water's case, mineral ions such as sodium, iron and calcium.
deliquescence Substances that absorb water from the atmosphere to form liquid solutions.
intensive property of a substance defined as mass per unit volume or d = m/V.
denticity The number of donor groups in a single
ligand that bind to a central atom in a coordination complex.
deposition The settling of particles within a solution or mixture.
Dewar flask See
. vacuum flask
diatomic Composed of two atoms.
diatomic molecule Any
molecule composed of only two atoms, of the same or different elements.
dipole The electric or magnetic separation of charge.
dipole moment The polarity of a polar covalent bond.
dissolution The interaction of a
solvent with the molecules or ions of a solute, involving bond formation, hydrogen bonding, and van der Waals forces. Also called solvation.
A sodium ion (Na
) forms a solvation complex with water molecules when
in an aqueous solution
double bond A
chemical bond involving the covalent sharing of two pairs of electrons.
ductility A measure of a material's ability to undergo significant plastic deformation before rupturing, typically expressed as percent elongation or percent area reduction from a tensile test and popularly characterized by the material's ability to be stretched into a wire. Also called
earth metal See
. alkaline earth metal
solution that conducts a certain amount of electric current and can be split categorically into weak and strong electrolytes.
electrochemical cell Using a chemical reaction's current,
electromotive force is made.
electromagnetic radiation A type of wave that can go through vacuums as well as material and is classified as a self-propagating wave.
electromagnetism Fields with an electric charge and electrical properties that change the way that particles move and interact.
electromotive force A device that gains energy as
electric charges pass through it.
electron A subatomic particle with a net charge that is negative.
electron pair Two
electrons which occupy the same molecular orbital but have opposite spins. Electron pairs form chemical bonds or occur as lone pairs of valence electrons; it is also possible for electrons to occur as unpaired electrons.
electron shell An orbital around an atom's nucleus containing a fixed number of
electrons (usually two or eight).
electric charge A measured property (
coulombs) that determines electromagnetic interaction.
element A species of
atoms having the same number of protons in their atomic nuclei and hence the same atomic number. Chemical elements constitute all of the ordinary matter in the universe; 118 elements have been identified and are organized by their various chemical properties in the periodic table of the elements.
energy A system's ability to do
enthalpy A measure of the total energy of a thermodynamic system. Usually symbolized as
enthalpy of fusion
entropy The amount of energy not available for work in a closed thermodynamic system. Usually symbolized as
protein catalyst that speeds up a chemical reaction.
empirical formula Also called the simplest formula, gives the simplest whole-number ratio of atoms of each element present in a compound.
equilibrium Universally, it is the condition of a system in which all competing influences are balanced.
Chemical equilibrium is the state in which the concentrations of the reactants and products have stopped changing in time.
Eppendorf tube A generalized and trademarked name used for a
phase transition of a substance from a liquid to a solid.
Faraday constant A unit of
electric charge widely used in electrochemistry and equal to ~ 96,500 coulombs. It represents 1 mol of electrons, or the Avogadro number of electrons: 6.022 × 10 23 electrons. F = 96 485.339 9(24) C/mol.
Faraday's laws of electrolysis A two-part law that
Michael Faraday published about electrolysis. The mass of a substance altered at an electrode during electrolysis is directly proportional to the quantity of electricity transferred at that electrode; the mass of an elemental material altered at an electrode is directly proportional to the element's equivalent weight.
Fick's laws of diffusion
frequency A measurement of the number of cycles of a given process per unit of time. The SI unit for measuring frequency is the
hertz (Hz), with 1 Hz = 1 cycle per second.
galvanic cell A type of
battery made up of electrochemicals with two different metals connected by a salt bridge.
gas One of the four fundamental
states of matter, characterized by high-energy particles which fill their container but have no definite shape or volume.
Gay-Lussac's law A chemical law used for each of the two relationships derived by French chemist
Joseph Louis Gay-Lussac and which concern the properties of gases, though the name is more usually applied to his law of combining volumes.
geochemistry The study of the chemistry and chemical composition of the Earth and
Gibbs energy A value that indicates the spontaneity of a reaction. Usually symbolized as
gram-atom One gram-atom of an element is defined as a collection of 6.023X10^23 atoms.
ground glass joint An apparatus designed to quickly and easily fit two pieces of leak-tight
glassware together, featuring ground glass surfaces and typically a custom-made conical taper.
group A column of the
periodic table of the elements and the elements that share it. Also called a family. Compare . period
halogen Any of the five
non-metallic elements of Group 17 of the periodic table: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At).
hadron A subatomic particle of a type including the
baryons and mesons that can take part in the strong interaction.
heat Energy transferred from one system to another by thermal interaction.
heat of fusion See
. enthalpy of fusion
hydrogen bond A form of electrostatic interaction between an
electronegative atom and a hydrogen atom bound to a second electronegative atom. Hydrogen bonding is unique because the small size of the hydrogen atoms permits proximity of the interacting electrical charges, and may occur as an intermolecular or intramolecular force.
hydrolysis The cleavage of a
chemical bond by the addition of water.
ideal gas constant The proportionality constant in the
ideal gas law, defined as 0.08206 L·atm/(K·mol). Also called the universal gas constant.
ideal gas law the volume of a gas is proportional to the amount of gas and its Kelvin temperature and inversely proportional to its pressure
indicator A special compound added to a
solution that changes color depending on the acidity of the solution; different indicators have different colors and effective pH ranges.
induced radioactivity radioactivity caused by bombarding a stable isotope with elemental particles, forming a radioactive isotope
inorganic compound Any chemical compound that does not contain
carbon, though there are exceptions.
inorganic chemistry A branch of chemistry concerning the chemical properties and reactions of inorganic compounds.
insulator Any material that resists the flow of electric current. Compare
(SI) International System of Units
(IUPAC) International Union of Pure and Applied Chemistry An international federation of chemists that is recognized as the world authority in developing standards for
chemical nomenclature and other methodologies in chemistry.
molecule that has gained or lost one or more electrons from its neutral state and therefore possesses a negative or positive electric charge.
ionic bond An electrostatic attraction between oppositely charged
atom (Na) and a
atom (F). The sodium atom loses its sole
(leaving the atom with a positive electrical charge), and the fluorine atom gains this same electron via an
(giving the atom a negative electrical charge). The oppositely charged
are then attracted to each other to form a new compound called
ionization The breaking up of a chemical
compound into separate ions.
isotope A variant of a particular
chemical element which differs in the number of neutrons present in the nucleus. All isotopes of a given element have the same number of protons in each atom.
SI unit of energy (symbol: J); 1 joule = 1 Newton- meter.
SI base unit of temperature (symbol: K). The Kelvin scale is an absolute thermodynamic temperature scale that uses absolute zero as its null point.
ketone An organic compound with a
carbonyl group between two carbon atoms.
kinetics A subfield of chemistry specializing in
kinetic energy The
energy of an object due to its motion.
periodic series of metallic elements with atomic numbers 57 through 71, from lanthanum through lutetium. Also called lanthanoids.
lattice The unique arrangement of atoms or molecules in a
crystalline liquid or solid.
law of conservation of energy
law of conservation of mass
law of multiple proportions
laws of thermodynamics
light The portion of the
electromagnetic spectrum which is visible to the unaided human eye. Also referred to as visible light.
liquid One of the four fundamental
states of matter, characterized by nearly incompressible fluid particles that retain a definite volume but no fixed shape.
London dispersion forces A type of weak
Newton's laws of motion An object in motion stays in motion; an object at rest stays at rest unless an unbalanced force acts upon it.
magnetic quantum number
manometer An instrument used to measure
pressure invented by Evangelista Torricelli in 1643.
property of physical matter that is a measure of its resistance to acceleration when a net force is applied. The SI base unit for mass is the kilogram (kg).
matter Any substance that has
mass and takes up space by having volume.
metal Any chemical element which is a good
conductor of both electricity and heat and which readily forms cations and ionic bonds with non-metals.
phase transition of a substance from a solid to a liquid.
metalloid A chemical element or substance possessing properties of both
metals and non-metals.
methylene blue A
heterocyclic aromatic compound with the molecular formula C 16 H 18 N 3 S Cl.
microcentrifuge tube A small plastic container that is used to store small amounts of liquid.
mixture A material made up of two or more different substances which are mixed physically but are not combined chemically (i.e. a chemical reaction has not taken place which has changed the molecules of the substances into new substances).
molar attenuation coefficient
mole A measurement of an amount of substance in terms of the absolute number of units or entities composing the substance; a single mole contains approximately 6.022×10
23 units or entities. Abbreviated mol.
molecular orbital The region where an electron can be found in a
molecule (as opposed to an atom).
molecular orbital diagram
molecule A number of atoms that are chemically bonded together and collectively electrically neutral.
neat conditions with a liquid reagent or gas performed with no added solvent or cosolvent
neutron A neutral unit or
subatomic particle that has no net charge.
neutrino a particle that can travel at speeds close to the speed of light and are created as a result of
nucleus The centre of an
atom, made up of neutrons and protons and possessing a net positive electric charge.
noble gas Any of the six
non-metallic elements of Group 18 of the periodic table: helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). All of the noble gases have outer electron shells that are completely filled in their naturally occurring states, giving them very low chemical reactivity.
non-metal Any element which is not a
nuclear Of or pertaining to the
nuclear chemistry The branch of chemistry that studies the various processes and properties relevant to
atomic nuclei, including radioactivity.
nuclear magnetic resonance spectroscopy A technique that exploits the magnetic properties of certain nuclei, useful for identifying unknown compounds. Nuclear magnetic resonance is often abbreviated
nuclide A species of
atom characterized by its mass number, atomic number, and nuclear energy state, provided that the mean life in that state is long enough to be observable.
number density A measure of the
concentration of countable objects (atoms, molecules, etc.) in space, expressed as the number per unit volume.
octet rule A classical rule for describing the
electron configuration of atoms in certain molecules: the maximum number of electron pairs that can be accommodated in the valence shell of an element in the first row of the periodic table is four (or eight total electrons). For elements in the second and subsequent rows, there are many exceptions to this rule. Also called the Lewis octet rule.
orbital may refer to either an
atomic orbital or a molecular orbital
order of reaction
organic compound Any
chemical compound that contains carbon. Compare . inorganic compound
organic chemistry A branch of chemistry concerned with the chemical properties and reactions of
organic compounds. Compare . inorganic chemistry
organic redox reaction
other metal metallic elements in the
p-block, characterized by having a combination of relatively low melting points (all less than 950 K) and relatively high electronegativity values (all more than 1.6, revised Pauling).
oxidation state 1) The degree of
oxidation (loss of electrons) of an individual atom in a chemical compound; 2) the hypothetical electric charge (positive, negative, or zero) that the atom would have if all bonds to atoms of different elements were 100% ionic, with no covalent component. Also called oxidation number.
oxoacid 1) Any
acid having oxygen in the acidic group; 2) any compound which contains oxygen, at least one other element, and at least one hydrogen atom bound to oxygen, and which produces a conjugate base by loss of positive hydrogen ions. Also called an oxyacid or oxacid.
pH A measure of
acidity or basicity of a solution.
phase transition 1) A transformation between
solid, liquid, and gaseous states of matter and, in rare cases, plasma; 2) the measurable values of the external conditions at which such a transformation occurs.
plasma One of the four fundamental
states of matter, in which very high-energy particles are partially or fully ionized to the point that they display unique properties and behaviors unlike those of the other three states. Plasma does not exist freely on the Earth's surface under natural conditions.
period One of the horizontal rows of the
periodic table and the elements it contains.
periodic table of the elements A tabular arrangement of the
chemical elements organized by their atomic number, electron configuration, and other chemical properties, whose adopted structure shows periodic trends and is used by chemists to derive relationships between various elements as well as predict the properties and behaviors of undiscovered or newly synthesized elements. The first periodic table of the elements was published by Russian chemist Dmitri Mendeleev in 1869. Also simply called the periodic table.
potential energy The stored energy in a body or in a system due to its position in a force field or due to its configuration.
precipitate The formation of a
solid in a solution or inside another solid during a chemical reaction or by diffusion in a solid.
precision How close the results of multiple experimental trials are. Compare
photon A carrier of
electromagnetic radiation of all wavelengths (such as gamma rays and radio waves).
polyatomic ion A molecule composed of two or more
covalently bonded atoms which collectively bear a net electric charge and therefore act as an ion.
subatomic particle with a positive electric charge that is found in the nucleus of an atom. Often denoted with the symbol H. +
protonation The addition of a
proton (H +) to an atom, molecule, or ion.
thermal decomposition of materials at elevated temperatures in an inert atmosphere such as a vacuum gas.
quantum mechanics The study of how atoms, molecules, subatomic particles, etc. behave and are structured.
quark An elementary particle and a fundamental constituent of matter.
quantum The minimum amount of bundle of energy. Plural
racemate An equimolar
mixture of a pair of enantiomers which does not exhibit optical activity. The chemical name or formula of a racemate is distinguished from those of the enantiomers by the prefix (±)- or by the symbols RS and SR.
radiation Energy released in the form of waves or
subatomic particles when there is a change from high-energy to low-energy states.
radioactive decay The process of an unstable atomic nucleus losing energy by emitting radiation.
reactant A substance that is consumed in the course of a
chemical reaction. Also called a . reagent
reaction rate The speed at which
reactants are converted into products in a chemical reaction.
reaction rate constant
reagent A test substance that is added to a system in order to bring about a
chemical reaction or to see whether a reaction occurs. Also another name for a . reactant
s-block The collective name for the elements in Groups 1 and 2 of the
periodic table (the alkali and alkaline metals), as well as hydrogen and helium.
ionic compound composed of one or more anions and one or more cations.
salt bridge A device used to connect reduction with oxidation half-cells in an
saline solution A common term for a
solution of sodium chloride (NaCl) dissolved in water (H 2O).
Schrödinger equation A quantum state equation which represents the behaviour of an election around an atom.
semiconductor An electrically conductive solid whose degree of
conductivity lies somewhere between that of a conductor and that of an insulator.
single bond A
chemical bond that involves the sharing of one pair of electrons.
sol A suspension of solid particles in liquid. Artificial examples include
solid One of the four fundamental
states of matter, characterized by relatively low-energy particles packed closely together in rigid structures with definite shape and volume. See . Young's modulus
solubility The property of a
solid, liquid, or gaseous solute to dissolve in a solid, liquid, or gaseous solvent. It is typically expressed as the proportion of solute dissolved in the solvent in a saturated solution.
solute The part of a
solution that is dissolved into the solvent (for example, sodium chloride (NaCl) is the solute in a solution of saline water).
solution A homogeneous
mixture made up of multiple substances generally referred to as solutes and solvents.
solvent The part of a
solution that dissolves the solute (for example, H 2O is the solvent in a solution of saline water).
spectroscopy The study of
radiation and matter, such as X-ray absorption and emission spectroscopy.
speed of light A physical constant defined as the speed of anything that has zero rest mass (Energy
rest = mc², where m is the mass and c is the speed of light).
standard conditions of temperature and pressure A standardisation of ambient
temperature and pressure used in order to easily compare experimental results. Standard temperature is 25 degrees Celsius (°C) and standard pressure is 100.000 kilopascals (kPa). Standard conditions are often denoted with the abbreviation STP or STAP.
state of matter
matter having a homogeneous, macroscopic phase; gas, plasma, liquid, and solid are the most well-known (in increasing concentration).
isomer which possesses an identical chemical composition but which differs in the spatial arrangement of its atoms.
phase transition of a substance from a solid to a limewater fuel or gas without an apparent transition to a liquid in the process.
subatomic particle Any particle that is smaller than an
atom. Examples include protons, neutrons and electrons.
substance A material with a definite chemical composition.
talc A mineral representing the
one on the Mohs Scale and composed of hydrated magnesium silicate with the chemical formula H 2Mg 3(SiO 3) 4 or Mg 3Si 4O 10(OH) 2.
temperature A proportional measure of the average
kinetic energy of the random motions of the constituent microscopic particles of a system. The SI base unit for temperature is the kelvin.
theoretical yield See
theory An experimentally testable model describing the nature of a phenomenon.
thermal conductivity The property of a material that allows it to conduct thermal energy or
heat (a quantity often denoted by ).
thermochemistry The study of the absorption or release of
heat during a chemical reaction.
thermodynamics The study of the effects of changing temperature, volume or pressure (or work, heat, and energy) on a macroscopic scale.
thermodynamic stability The condition of a system being in its lowest energy state with its environment (equilibrium).
thermometer An instrument used to measure
titration The process of titrating one solution with another. Also called
torr A unit for measuring
pressure (1 torr is equivalent to 133.322 Pa or 1.3158×10 −3 atm).
transition metal An element whose atoms naturally occur with incompletely filled "d" sub-shells. These elements are grouped as the
in the d-block elements periodic table.
transuranic element Any element with an
atomic number greater than 92. None of the transuranic elements are stable in natural conditions.
triple bond A
chemical bond that involves the covalent sharing of three pairs of electrons (for example, the diatomic nitrogen molecule, N 2, is composed of two nitrogen atoms linked by a triple bond).
triple point The place where
temperature and pressure of three phases are the same ( water has a special phase diagram).
Tyndall effect The effect of light scattering by colloidal (mixture where one substance is dispersed evenly through another) or suspended particles.
UN number A four-digit code used to note hazardous and flammable substances.
uncertainty The notion that any measurement that involves estimation of any amount cannot be exactly reproducible.
uncertainty principle knowing the location of a particle makes the momentum uncertain, while knowing the momentum of a particle makes the location uncertain.
unified atomic mass unit A unit of
mass approximately equal to the mass of one proton or neutron and denoted with the symbol u; also called a Dalton and denoted with the symbol Da. Sometimes equated with the technically distinct and obsolete atomic mass unit and abbreviated amu.
unit cell The smallest repeating unit of a
unit factor statements used in converting between units.
vacuum flask An insulating storage vessel that can greatly lengthen the time over which its contents remain warmer or cooler than the vessel's ambient environment. Also called a
Dewar flask or thermos.
valence electron Any of the outermost
electrons of an atom, which are located in electron shells.
valence bond theory A theory explaining the chemical bonding within molecules by discussing
valencies, the number of chemical bonds formed by an atom.
valency The combining capacity of an element.
van der Waals force One of the forces (attraction/repulsion) between molecules.
van 't Hoff factor The ratio of moles of particles in solution to moles of solute dissolved.
vapor When a substance is below the critical temperature while in the gas phase.
vapor pressure The pressure of vapor over a liquid at equilibrium.
phase transition of a substance from a liquid to a gas. Also called boiling.
viscosity A measure of the resistance of a
liquid to flow.
volt A unit that measures the electrical potential transferred. One volt (V) is defined as and equivalent to one
Joule of work per coulomb.
voltmeter An instrument that measures electrical
volume The quantity of
three-dimensional space enclosed by a closed surface, or the space that a substance (solid, liquid, gas, or plasma) or shape occupies or contains. The SI unit for volume is the cubic metre (m 3).
volumetric analysis See
polar inorganic compound with the chemical formula H 2O that is a tasteless, odorless, and generally colorless liquid at standard temperature and pressure, though it also occurs naturally as a solid and a gas at the Earth's surface. It is the most abundant substance on Earth and therefore an integral component of virtually all chemical and biological systems. Water is often described as the "universal solvent" for its inherent ability to dissolve many substances.
wave function a function describing the electron's position in a three-dimensional space.
work the amount of force over distance and is in terms of
X-ray A form of ionizing, electromagnetic radiation between
gamma and UV rays in the electromagnetic spectrum.
X-ray diffraction a method for establishing structures of
crystalline solids using single wavelength X-rays and looking at diffraction pattern.
X-ray photoelectron spectroscopy A
spectroscopic technique used to measure the composition of a material.
yield The quantifiable amount of
product produced during a chemical reaction.
zone melting A way to remove impurities from an element by melting it and slowly travel down an ingot (cast).
zwitterion A chemical compound whose net charge is zero and hence is electrically neutral. But there are some positive and negative charges in it, due to the formal charge, owing to the partial charges of its constituent atoms.
zinc A metallic
chemical element with atomic number 30 and symbol Zn.
See also [ edit ]
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