JonyC/ScienceGlossary · Datasets at Hugging Face

term stringlengths 1 63 ⌀	category stringclasses 15 values	label int64 0 1	definition stringlengths 5 3.18k ⌀
amphipathic	Chemistry	1	(of a molecule) Composed of both hydrophilic and hydrophobic groups; e.g. wetting agents and membrane lipids.
amphoteric	Chemistry	1	(of a chemical species) Tending to behave both as an acid and as a base, depending upon the medium in which the species is situated; e.g. sulfuric acid (H2SO4) is a strong acid in water but behaves more like a base in superacids.
amyl	Chemistry	1	A common non-systematic name for a pentyl group.
analyte	Chemistry	1	The specific substance or chemical constituent that is of interest in a chemical analysis.
analytical chemistry	Chemistry	1	The branch of chemistry which studies and makes use of instruments and methods to separate, quantify, and identify chemical substances, both by classical wet chemistry techniques such as precipitation, extraction, distillation, and observational analysis, and by modern instrumental techniques such as chromatography, spectroscopy, and electrochemistry.
ångström	Chemistry	1	A non-SI, metric unit of length equal to 10−10 metre, i.e. 1⁄10000000000 of a metre or 0.1 nanometre. The angstrom is commonly used in the natural sciences to express microscopic or atomic-scale distances, including the sizes of atomic nuclei, wavelengths of electromagnetic radiation, and lengths of chemical bonds (e.g. the covalent radius of a chlorine atom averages about 1 angstrom).
å	Chemistry	1	A non-SI, metric unit of length equal to 10−10 metre, i.e. 1⁄10000000000 of a metre or 0.1 nanometre. The angstrom is commonly used in the natural sciences to express microscopic or atomic-scale distances, including the sizes of atomic nuclei, wavelengths of electromagnetic radiation, and lengths of chemical bonds (e.g. the covalent radius of a chlorine atom averages about 1 angstrom).
anhydrous	Chemistry	1	Having or containing no water molecules, referring especially to water of hydration. Because many processes in chemistry are impeded in the presence of water, it is often of critical importance that water-free reagents and techniques are used. Anhydrous compounds tend to gradually absorb water from the atmosphere. Contrast hydrous.
anion	Chemistry	1	A negatively charged ion; i.e. an atom or molecule with a net negative electric charge caused by an excess of electrons compared to protons.
annulation	Chemistry	1	The formation of a cyclic compound or ring structure from one or several acyclic precursors; or a reaction involving the addition of a ring structure to another molecule via two new bonds.
anode	Chemistry	1	1. An electrode through which the conventional electric current (the flow of positive charges) enters into a polarized electrical circuit.
anomer	Chemistry	1	Either of a pair of cyclic hemiacetal or hemiketal saccharides that are epimers of each other, differing at only one carbon stereocenter, specifically the carbon that bears the aldehyde or ketone functional group in the compound's acyclic, open-chain configuration, known as the anomeric carbon.
aprotic	Chemistry	1	(of a chemical species) Not protic; i.e. not capable of acting as a proton donor or readily yielding of protons (H+) in solution.
aqua regia	Chemistry	1	A liquid mixture of nitric acid (HNO3) and hydrochloric acid (HCl), optimally in a molar ratio of 1:3, so named by historical alchemists because it is capable of dissolving the noble metals gold and platinum.
aquation	Chemistry	1	The process by which water molecules solvate or form coordination complexes with ions.
aqueous solution	Chemistry	1	A solution in which the solvent is water. It is denoted in chemical equations by appending (aq) to a chemical formula.
aromaticity	Chemistry	1	A chemical property of conjugated rings of atoms, such as benzene, which results in unusually high stability. Such rings are said to be aromatic.
arrhenius acid	Chemistry	1	Any substance that, when dissolved in water, increases the concentration of H+ ions, or, more correctly, of hydronium ions (H3O+), in the resulting aqueous solution. The definition is similar to that of a Brønsted–Lowry acid. Contrast Arrhenius base.
arrhenius base	Chemistry	1	Any substance that, when dissolved in water, increases the concentration of OH− ions, or, alternatively, decreases the concentration of hydronium ions (H3O+), in the resulting aqueous solution. The definition is similar to that of a Brønsted–Lowry base. Contrast Arrhenius acid.
aryl	Chemistry	1	Any functional group or substituent derived from an aromatic ring, such as phenyl or naphthyl. The symbol Ar is often used as a placeholder for a generic aryl group in structural diagrams.
atmolysis	Chemistry	1	The separation of a mixture of gases by exploiting their different rates of diffusion, usually by allowing the gases to diffuse through the walls of a porous partition or membrane.
atom	Chemistry	1	A chemical element in its smallest form, made up of protons and neutrons within the nucleus and electrons circling the nucleus.
atomic mass	Chemistry	1	The average mass of all isotopes of an element, taking their natural relative proportions into account. For example, chlorine has two main isotopes –37Cl and35Cl. In naturally occurring chlorine, 75% is35Cl and 25% is37Cl. Therefore, the weighted average (atomic mass) is 35.5.
atomic mass unit	Chemistry	1	See dalton.
atomic number	Chemistry	1	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.
z	Chemistry	1	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.
atomic orbital	Chemistry	1	Any region in which one or more electrons may be found in an individual atom (as opposed to that within a molecule).
atomic weight	Chemistry	1	See relative atomic mass.
atomicity	Chemistry	1	The total number of atoms present in a single molecule of a given substance; e.g. ozone (O3) has an atomicity of 3, while benzene (C6H6) has an atomicity of 12.
autoignition temperature	Chemistry	1	The lowest temperature at which a given substance will spontaneously ignite in a normal atmosphere without an external source of ignition such as a flame or spark, i.e. when the ambient temperature is sufficiently high to provide the activation energy needed for combustion. Substances which spontaneously ignite at naturally occurring temperatures are termed pyrophoric. Compare ignition temperature.
avogadro constant	Chemistry	1	The ratio of the number of discrete constituent particles (such as molecules, atoms, or ions) to the amount of a substance, defined as exactly 6.02214076×1023 mol−1.
na	Chemistry	1	The ratio of the number of discrete constituent particles (such as molecules, atoms, or ions) to the amount of a substance, defined as exactly 6.02214076×1023 mol−1.
avogadro number	Chemistry	1	The number of discrete constituent particles in one mole of a substance, defined as exactly 6.02214076×1023. This dimensionless number differs from the Avogadro constant in that it has no unit.
azeotrope	Chemistry	1	A mixture of liquids whose chemical composition is unchanged by distillation.
backbone	Chemistry	1	The primary or most structurally significant portion of a molecule with respect to its other parts, functional groups, moieties, or substituents; or, in the case of a polymer, that linear chain of atoms to which all other chains, long or short or both, may be regarded as being pendant or as side chains. Where two or more chains might equally be considered the backbone, the one which permits the simplest representation of the molecule in chemical formulae and nomenclature is considered the backbone.
barometer	Chemistry	1	A device used to measure atmospheric pressure.
base	Chemistry	1	A substance that accepts a proton and has a pH above 7.0. A common example is sodium hydroxide (NaOH).
base anhydride	Chemistry	1	An oxide of a group I or II metal element.
beaker	Chemistry	1	A cylindrical vessel or container with a flat bottom, most commonly a type of glassware, widely used in laboratories for a variety of purposes, such as preparing, holding, containing, collecting, or volumetrically measuring chemicals, samples, or solutions, or as a chamber in which a chemical reaction occurs. Beakers are distinguished from flasks by having straight rather than sloping sides; most beakers also have a small spout in the rim to aid pouring.
biochemistry	Chemistry	1	The study of the chemistry of biological systems and organisms.
bohr model	Chemistry	1	A model of the general structure of the atom proposed by Niels Bohr and Ernest Rutherford in 1913, featuring a small, dense nucleus of positively charged particles surrounded by orbiting electrons, which are attracted to the nucleus by electrostatic forces. This interpretation replaced several earlier hypotheses and quickly became the prevailing standard model for depicting atomic structure.
boiling	Chemistry	1	A more rapid, highly energetic form of vaporization, in which a substance undergoes a phase transition from liquid to gas, as contrasted with the much slower process of vaporization. Boiling occurs when a liquid is heated to its boiling point, above which the liquid's internal vapor pressure exceeds the pressure exerted upon it by the surrounding atmosphere, causing the gaseous phase to rapidly and often violently separate from the liquid phase.
boiling flask	Chemistry	1	A type of flask, usually made of glass, with a large round body, long neck, and flat bottom, designed especially for heating, boiling, and distilling liquids and to make swirling easy. See also round-bottom flask.
boiling point	Chemistry	1	The temperature at which a substance changes state from a liquid to a gas (or vapor). It depends on pressure and is usually specified for a given substance under standard conditions.
boiling-point elevation	Chemistry	1	The process by which a substance's boiling point is elevated by adding another substance.
bond	Chemistry	1	Any persistent attraction between atoms, ions, or molecules that enables the formation of chemical compounds. Bonds are created as a result of a wide variety of electrochemical forces, whose strengths can vary considerably; they are broken when these forces are overcome by other forces. The types, strengths, and quantities of bonds holding together chemical substances dictate the structure and bulk properties of matter.
boyle's law	Chemistry	1	For a given mass of gas at constant temperature, the volume varies inversely with the pressure.
bridge	Chemistry	1	A chemical bond between valence electrons, or an atom or unbranched chain of atoms connecting two different parts of the same molecule; i.e. an intramolecular bond linking different moieties or functional groups.
bridgehead	Chemistry	1	Either of the two tertiary atoms which by bonding to each other form an intramolecular bridge.
brønsted–lowry acid	Chemistry	1	Any chemical species that readily donates a proton.
brønsted–lowry base	Chemistry	1	Any chemical species that readily accepts a proton.
buffered solution	Chemistry	1	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.
bumping	Chemistry	1	A phenomenon in which a homogeneous liquid raised to its boiling point becomes superheated and, upon nucleation, rapidly boils to the gas phase, resulting in a violent expulsion of the liquid from the container; in extreme cases, the container itself may shatter. Frequent stirring, the use of an appropriate container, and the use of boiling chips can help prevent bumping.
bung	Chemistry	1	A cylindrical or conical plug or closure used to seal a container such as a bottle, tube, flask, or barrel.
burette	Chemistry	1	Glassware used to dispense specific amounts of liquid when precision is necessary (e.g. during titrations and resource-dependent reactions).
butyl	Chemistry	1	The alkyl functional group derived from either of the two isomers of butane, with the generic chemical formula –C4H9. It may occur as a substituent in organic compounds or exist independently as an ion or radical. In IUPAC nomenclature, the presence of a butyl substituent is indicated with the prefix butyl in the name of the compound, or with the abbreviation Bu in chemical formulae; e.g. butyl alcohol (butanol), which may occur in any of five different isomeric forms depending on the arrangement of the four carbon atoms, is often written with the generic formula CH4CH9OH or BuOH.
calorific value	Chemistry	1	A measure of the heat per unit mass produced by complete combustion of a given substance, usually expressed in megajoules per kilogram (MJ/kg) or in kilojoules per gram (kJ/g).
calorimeter	Chemistry	1	Any of various devices used to measure thermal properties (i.e. heat), such as calorific values or heats of chemical reactions.
calx	Chemistry	1	A metal oxide formed by heating an ore in air.
carbanion	Chemistry	1	Any organic ion with a negative charge on a carbon atom, i.e. an ion of the general formula R3C−. Carbanions are frequently intermediate species in certain organic reactions. Contrast carbocation.
carbide	Chemistry	1	A class of interstitial compounds composed of carbon bonded to a particular metal (usually a large-radius transition metal) in a densely packed crystal lattice, where the carbon atoms occupy interstices between the metal atoms; e.g. tungsten carbide (WC).
carbonization	Chemistry	1	1. The conversion of organic compounds, such as those found in biological organisms, into other forms of carbon or carbonic residues by heating or burning, or during fossilization.
carbonyl	Chemistry	1	1. A functional group composed of a carbon atom double-bonded to an oxygen atom, with the formula C = O {\ce {C=O}}} . Carbonyl groups are common to many classes of organic compounds and are also a part of many larger functional groups.
carboxylic acid	Chemistry	1	A class of organic acids and a functional group consisting of a carboxyl group attached to a substituent group. Carboxylic acids have the general formula R − COOH {\ce {R-COOH}}} (also written as R − CO 2 H {\ce {R-CO2H}}} ), where R {\ce {R}}} can be an alkyl, alkenyl, aryl, or any other carbon-containing substituent.
cas registry number	Chemistry	1	A unique numerical identifier assigned by the Chemical Abstracts Service (CAS) to every chemical substance described in the open scientific literature, including more than 182 million organic and inorganic compounds, minerals, isotopes, alloys, polymers, and mixtures, as well as so-called "UVCBs" (substances of unknown or variable composition, complex reaction products, or biological origin). CAS numbers are an internationally recognized standard used by scientists, industries, and regulatory bodies.
cas rn	Chemistry	1	A unique numerical identifier assigned by the Chemical Abstracts Service (CAS) to every chemical substance described in the open scientific literature, including more than 182 million organic and inorganic compounds, minerals, isotopes, alloys, polymers, and mixtures, as well as so-called "UVCBs" (substances of unknown or variable composition, complex reaction products, or biological origin). CAS numbers are an internationally recognized standard used by scientists, industries, and regulatory bodies.
catalyst	Chemistry	1	A substance that increases the rate of a chemical reaction but is not permanently changed by that reaction. In living organisms enzymes are catalysts.
cathode	Chemistry	1	An 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. Contrast anode.
cation	Chemistry	1	An ion with more protons than electrons, giving it a positive charge. For example, positively charged metal ions like Na+and Ca2+are cations.
cell potential	Chemistry	1	The force in a galvanic cell that pulls electrons through a reducing agent to an oxidizing agent.
centrifugation	Chemistry	1	A laboratory technique which involves the application of centrifugal force to separate particles from a solution according to their size, shape, and density. Larger and/or denser substances migrate away from the axis of a centrifuge, while smaller and/or less dense substances migrate towards the axis.
centrifuge	Chemistry	1	A device used to separate substances based on size, shape, and density by centrifugation, or the rotation of vessels containing the substances around a centred axis at extremely high velocities.
charge number	Chemistry	1	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	Chemistry	1	A classical gas law which states that when the pressure on a sample of a dry gas is held constant, the Kelvin temperature is directly proportional to its volume.
chelation	Chemistry	1	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	Chemistry	1	See chemical species and chemical compound.
chemical bond	Chemistry	1	See bond.
chemical composition	Chemistry	1	The identity and relative number of the elements that make up a chemical compound, which can often be expressed with a chemical formula.
chemical compound	Chemistry	1	See compound.
chemical decomposition	Chemistry	1	The breakdown of a single particle or entity (such as a molecule or reactive intermediate) into two or more fragments, or a chemical reaction in which two or more products are formed from a single reactant. Contrast chemical synthesis.
chemical element	Chemistry	1	See element.
chemical formula	Chemistry	1	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	Chemistry	1	A law of nature relevant to chemistry, such as the law of conservation of mass.
chemical process	Chemistry	1	1. Any method or means of changing one or more chemicals or chemical compounds in any way, either naturally or artificially, spontaneously or by the actions of external forces.
chemical reaction	Chemistry	1	A process in which one or more substances are changed into different substances.
chemical species	Chemistry	1	A chemical substance or ensemble of substances composed of chemically identical molecular entities which can explore the same set of molecular energy levels on a characteristic or delineated time scale.
chemical substance	Chemistry	1	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.
chemical synthesis	Chemistry	1	The artificial execution of one or more chemical reactions in order to obtain one or more products. In modern laboratory contexts, specific chemical syntheses are both reliable and reproducible.
chemistry	Chemistry	1	The scientific discipline that studies chemical substances, compounds, and molecules composed of atoms of various chemical elements, as well as their compositions, structures, properties, behaviors, and the changes they undergo during reactions with other substances.
chirality	Chemistry	1	A property of asymmetry in which a molecule or ion is distinguishable from its mirror image such that it cannot be superposed upon it by any combination of geometric rotations, translations, or some conformational changes. Such a molecule or ion is said to be chiral, and exists in two forms, known as enantiomers, which are stereoisomers of each other; these forms are distinguished as either "right-handed" or "left-handed" by their absolute configuration or some other criterion. Several different types of asymmetry can give rise to chirality, most commonly when molecules possess stereogenic elements such as one or more stereocenters (central chirality), a stereogenic axis (axial chirality), or a stereogenic plane (planar chirality); additionally, the inherent curvature of a molecule can cause it to possess inherent chirality.
chromometer	Chemistry	1	See colorimeter.
cohesion	Chemistry	1	The tendency of similar particles or surfaces to cling to one another as a result of intermolecular forces. Contrast adhesion.
colligative property	Chemistry	1	Any property of a solution 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. Examples include osmotic pressure, freezing-point depression, and boiling-point elevation.
colloid	Chemistry	1	A mixture in which microscopic insoluble particles are suspended within and evenly dispersed throughout another substance, usually a liquid but sometimes inclusive of aerosols and gels. Thus a colloid contains a dispersed phase and a continuous phase. Many milks are colloids.
color standard	Chemistry	1	A liquid solution of known chemical composition and concentration, and hence of known and standardized color, used as a reference in the optical analysis of samples of unknown strength.
color test	Chemistry	1	The quantitative analysis of a substance by comparing the intensity of the color produced when the substance is exposed to a reagent with a standard color produced similarly in a solution of known strength.
colorimeter	Chemistry	1	Any instrument used for color measurement based on optical comparison with standard colors, particularly a device used in colorimetry that measures the absorbance of specific wavelengths of light by a given solution in order to determine the concentration of a known solute in the solution, by application of the principle that solute concentration is directly proportional to absorbance.
combustion	Chemistry	1	A chemical reaction that involves the process of burning.
complex	Chemistry	1	A molecular entity formed by loose association between two or more component molecular entities (ionic or uncharged), or the corresponding chemical species. The bonding between the components is normally weaker than in a covalent bond. See also coordination complex.
compound	Chemistry	1	A pure substance made up of two or more different elements chemically combined.

amphipathic

Chemistry

1

(of a molecule) Composed of both hydrophilic and hydrophobic groups; e.g. wetting agents and membrane lipids.

amphoteric

Chemistry

1

(of a chemical species) Tending to behave both as an acid and as a base, depending upon the medium in which the species is situated; e.g. sulfuric acid (H2SO4) is a strong acid in water but behaves more like a base in superacids.

amyl

Chemistry

1

A common non-systematic name for a pentyl group.

analyte

Chemistry

1

The specific substance or chemical constituent that is of interest in a chemical analysis.

analytical chemistry

Chemistry

1

The branch of chemistry which studies and makes use of instruments and methods to separate, quantify, and identify chemical substances, both by classical wet chemistry techniques such as precipitation, extraction, distillation, and observational analysis, and by modern instrumental techniques such as chromatography, spectroscopy, and electrochemistry.

ångström

Chemistry

1

A non-SI, metric unit of length equal to 10−10 metre, i.e. 1⁄10000000000 of a metre or 0.1 nanometre. The angstrom is commonly used in the natural sciences to express microscopic or atomic-scale distances, including the sizes of atomic nuclei, wavelengths of electromagnetic radiation, and lengths of chemical bonds (e.g. the covalent radius of a chlorine atom averages about 1 angstrom).

å

Chemistry

1

A non-SI, metric unit of length equal to 10−10 metre, i.e. 1⁄10000000000 of a metre or 0.1 nanometre. The angstrom is commonly used in the natural sciences to express microscopic or atomic-scale distances, including the sizes of atomic nuclei, wavelengths of electromagnetic radiation, and lengths of chemical bonds (e.g. the covalent radius of a chlorine atom averages about 1 angstrom).

anhydrous

Chemistry

1

Having or containing no water molecules, referring especially to water of hydration. Because many processes in chemistry are impeded in the presence of water, it is often of critical importance that water-free reagents and techniques are used. Anhydrous compounds tend to gradually absorb water from the atmosphere. Contrast hydrous.

anion

Chemistry

1

A negatively charged ion; i.e. an atom or molecule with a net negative electric charge caused by an excess of electrons compared to protons.

annulation

Chemistry

1

The formation of a cyclic compound or ring structure from one or several acyclic precursors; or a reaction involving the addition of a ring structure to another molecule via two new bonds.

anode

Chemistry

1

1. An electrode through which the conventional electric current (the flow of positive charges) enters into a polarized electrical circuit.

anomer

Chemistry

1

Either of a pair of cyclic hemiacetal or hemiketal saccharides that are epimers of each other, differing at only one carbon stereocenter, specifically the carbon that bears the aldehyde or ketone functional group in the compound's acyclic, open-chain configuration, known as the anomeric carbon.

aprotic

Chemistry

1

(of a chemical species) Not protic; i.e. not capable of acting as a proton donor or readily yielding of protons (H+) in solution.

aqua regia

Chemistry

1

A liquid mixture of nitric acid (HNO3) and hydrochloric acid (HCl), optimally in a molar ratio of 1:3, so named by historical alchemists because it is capable of dissolving the noble metals gold and platinum.

aquation

Chemistry

1

The process by which water molecules solvate or form coordination complexes with ions.

aqueous solution

Chemistry

1

A solution in which the solvent is water. It is denoted in chemical equations by appending (aq) to a chemical formula.

aromaticity

Chemistry

1

A chemical property of conjugated rings of atoms, such as benzene, which results in unusually high stability. Such rings are said to be aromatic.

arrhenius acid

Chemistry

1

Any substance that, when dissolved in water, increases the concentration of H+ ions, or, more correctly, of hydronium ions (H3O+), in the resulting aqueous solution. The definition is similar to that of a Brønsted–Lowry acid. Contrast Arrhenius base.

arrhenius base

Chemistry

1

Any substance that, when dissolved in water, increases the concentration of OH− ions, or, alternatively, decreases the concentration of hydronium ions (H3O+), in the resulting aqueous solution. The definition is similar to that of a Brønsted–Lowry base. Contrast Arrhenius acid.

aryl

Chemistry

1

Any functional group or substituent derived from an aromatic ring, such as phenyl or naphthyl. The symbol Ar is often used as a placeholder for a generic aryl group in structural diagrams.

atmolysis

Chemistry

1

The separation of a mixture of gases by exploiting their different rates of diffusion, usually by allowing the gases to diffuse through the walls of a porous partition or membrane.

atom

Chemistry

1

A chemical element in its smallest form, made up of protons and neutrons within the nucleus and electrons circling the nucleus.

atomic mass

Chemistry

1

The average mass of all isotopes of an element, taking their natural relative proportions into account. For example, chlorine has two main isotopes –37Cl and35Cl. In naturally occurring chlorine, 75% is35Cl and 25% is37Cl. Therefore, the weighted average (atomic mass) is 35.5.

atomic mass unit

Chemistry

1

See dalton.

atomic number

Chemistry

1

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.

z

Chemistry

1

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.

atomic orbital

Chemistry

1

Any region in which one or more electrons may be found in an individual atom (as opposed to that within a molecule).

atomic weight

Chemistry

1

See relative atomic mass.

atomicity

Chemistry

1

The total number of atoms present in a single molecule of a given substance; e.g. ozone (O3) has an atomicity of 3, while benzene (C6H6) has an atomicity of 12.

autoignition temperature

Chemistry

1

The lowest temperature at which a given substance will spontaneously ignite in a normal atmosphere without an external source of ignition such as a flame or spark, i.e. when the ambient temperature is sufficiently high to provide the activation energy needed for combustion. Substances which spontaneously ignite at naturally occurring temperatures are termed pyrophoric. Compare ignition temperature.

avogadro constant

Chemistry

1

The ratio of the number of discrete constituent particles (such as molecules, atoms, or ions) to the amount of a substance, defined as exactly 6.02214076×1023 mol−1.

na

Chemistry

1

The ratio of the number of discrete constituent particles (such as molecules, atoms, or ions) to the amount of a substance, defined as exactly 6.02214076×1023 mol−1.

avogadro number

Chemistry

1

The number of discrete constituent particles in one mole of a substance, defined as exactly 6.02214076×1023. This dimensionless number differs from the Avogadro constant in that it has no unit.

azeotrope

Chemistry

1

A mixture of liquids whose chemical composition is unchanged by distillation.

backbone

Chemistry

1

The primary or most structurally significant portion of a molecule with respect to its other parts, functional groups, moieties, or substituents; or, in the case of a polymer, that linear chain of atoms to which all other chains, long or short or both, may be regarded as being pendant or as side chains. Where two or more chains might equally be considered the backbone, the one which permits the simplest representation of the molecule in chemical formulae and nomenclature is considered the backbone.

barometer

Chemistry

1

A device used to measure atmospheric pressure.

base

Chemistry

1

A substance that accepts a proton and has a pH above 7.0. A common example is sodium hydroxide (NaOH).

base anhydride

Chemistry

1

An oxide of a group I or II metal element.

beaker

Chemistry

1

A cylindrical vessel or container with a flat bottom, most commonly a type of glassware, widely used in laboratories for a variety of purposes, such as preparing, holding, containing, collecting, or volumetrically measuring chemicals, samples, or solutions, or as a chamber in which a chemical reaction occurs. Beakers are distinguished from flasks by having straight rather than sloping sides; most beakers also have a small spout in the rim to aid pouring.

biochemistry

Chemistry

1

The study of the chemistry of biological systems and organisms.

bohr model

Chemistry

1

A model of the general structure of the atom proposed by Niels Bohr and Ernest Rutherford in 1913, featuring a small, dense nucleus of positively charged particles surrounded by orbiting electrons, which are attracted to the nucleus by electrostatic forces. This interpretation replaced several earlier hypotheses and quickly became the prevailing standard model for depicting atomic structure.

boiling

Chemistry

1

A more rapid, highly energetic form of vaporization, in which a substance undergoes a phase transition from liquid to gas, as contrasted with the much slower process of vaporization. Boiling occurs when a liquid is heated to its boiling point, above which the liquid's internal vapor pressure exceeds the pressure exerted upon it by the surrounding atmosphere, causing the gaseous phase to rapidly and often violently separate from the liquid phase.

boiling flask

Chemistry

1

A type of flask, usually made of glass, with a large round body, long neck, and flat bottom, designed especially for heating, boiling, and distilling liquids and to make swirling easy. See also round-bottom flask.

boiling point

Chemistry

1

The temperature at which a substance changes state from a liquid to a gas (or vapor). It depends on pressure and is usually specified for a given substance under standard conditions.

boiling-point elevation

Chemistry

1

The process by which a substance's boiling point is elevated by adding another substance.

bond

Chemistry

1

Any persistent attraction between atoms, ions, or molecules that enables the formation of chemical compounds. Bonds are created as a result of a wide variety of electrochemical forces, whose strengths can vary considerably; they are broken when these forces are overcome by other forces. The types, strengths, and quantities of bonds holding together chemical substances dictate the structure and bulk properties of matter.

boyle's law

Chemistry

1

For a given mass of gas at constant temperature, the volume varies inversely with the pressure.

bridge

Chemistry

1

A chemical bond between valence electrons, or an atom or unbranched chain of atoms connecting two different parts of the same molecule; i.e. an intramolecular bond linking different moieties or functional groups.

bridgehead

Chemistry

1

Either of the two tertiary atoms which by bonding to each other form an intramolecular bridge.

brønsted–lowry acid

Chemistry

1

Any chemical species that readily donates a proton.

brønsted–lowry base

Chemistry

1

Any chemical species that readily accepts a proton.

buffered solution

Chemistry

1

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.

bumping

Chemistry

1

A phenomenon in which a homogeneous liquid raised to its boiling point becomes superheated and, upon nucleation, rapidly boils to the gas phase, resulting in a violent expulsion of the liquid from the container; in extreme cases, the container itself may shatter. Frequent stirring, the use of an appropriate container, and the use of boiling chips can help prevent bumping.

bung

Chemistry

1

A cylindrical or conical plug or closure used to seal a container such as a bottle, tube, flask, or barrel.

burette

Chemistry

1

Glassware used to dispense specific amounts of liquid when precision is necessary (e.g. during titrations and resource-dependent reactions).

butyl

Chemistry

1

The alkyl functional group derived from either of the two isomers of butane, with the generic chemical formula –C4H9. It may occur as a substituent in organic compounds or exist independently as an ion or radical. In IUPAC nomenclature, the presence of a butyl substituent is indicated with the prefix butyl in the name of the compound, or with the abbreviation Bu in chemical formulae; e.g. butyl alcohol (butanol), which may occur in any of five different isomeric forms depending on the arrangement of the four carbon atoms, is often written with the generic formula CH4CH9OH or BuOH.

calorific value

Chemistry

1

A measure of the heat per unit mass produced by complete combustion of a given substance, usually expressed in megajoules per kilogram (MJ/kg) or in kilojoules per gram (kJ/g).

calorimeter

Chemistry

1

Any of various devices used to measure thermal properties (i.e. heat), such as calorific values or heats of chemical reactions.

calx

Chemistry

1

A metal oxide formed by heating an ore in air.

carbanion

Chemistry

1

Any organic ion with a negative charge on a carbon atom, i.e. an ion of the general formula R3C−. Carbanions are frequently intermediate species in certain organic reactions. Contrast carbocation.

carbide

Chemistry

1

A class of interstitial compounds composed of carbon bonded to a particular metal (usually a large-radius transition metal) in a densely packed crystal lattice, where the carbon atoms occupy interstices between the metal atoms; e.g. tungsten carbide (WC).

carbonization

Chemistry

1

1. The conversion of organic compounds, such as those found in biological organisms, into other forms of carbon or carbonic residues by heating or burning, or during fossilization.

carbonyl

Chemistry

1

1. A functional group composed of a carbon atom double-bonded to an oxygen atom, with the formula C = O {\ce {C=O}}} . Carbonyl groups are common to many classes of organic compounds and are also a part of many larger functional groups.

carboxylic acid

Chemistry

1

A class of organic acids and a functional group consisting of a carboxyl group attached to a substituent group. Carboxylic acids have the general formula R − COOH {\ce {R-COOH}}} (also written as R − CO 2 H {\ce {R-CO2H}}} ), where R {\ce {R}}} can be an alkyl, alkenyl, aryl, or any other carbon-containing substituent.

cas registry number

Chemistry

1

A unique numerical identifier assigned by the Chemical Abstracts Service (CAS) to every chemical substance described in the open scientific literature, including more than 182 million organic and inorganic compounds, minerals, isotopes, alloys, polymers, and mixtures, as well as so-called "UVCBs" (substances of unknown or variable composition, complex reaction products, or biological origin). CAS numbers are an internationally recognized standard used by scientists, industries, and regulatory bodies.

cas rn

Chemistry

1

A unique numerical identifier assigned by the Chemical Abstracts Service (CAS) to every chemical substance described in the open scientific literature, including more than 182 million organic and inorganic compounds, minerals, isotopes, alloys, polymers, and mixtures, as well as so-called "UVCBs" (substances of unknown or variable composition, complex reaction products, or biological origin). CAS numbers are an internationally recognized standard used by scientists, industries, and regulatory bodies.

catalyst

Chemistry

1

A substance that increases the rate of a chemical reaction but is not permanently changed by that reaction. In living organisms enzymes are catalysts.

cathode

Chemistry

1

An 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. Contrast anode.

cation

Chemistry

1

An ion with more protons than electrons, giving it a positive charge. For example, positively charged metal ions like Na+and Ca2+are cations.

cell potential

Chemistry

1

The force in a galvanic cell that pulls electrons through a reducing agent to an oxidizing agent.

centrifugation

Chemistry

1

A laboratory technique which involves the application of centrifugal force to separate particles from a solution according to their size, shape, and density. Larger and/or denser substances migrate away from the axis of a centrifuge, while smaller and/or less dense substances migrate towards the axis.

centrifuge

Chemistry

1

A device used to separate substances based on size, shape, and density by centrifugation, or the rotation of vessels containing the substances around a centred axis at extremely high velocities.

charge number

Chemistry

1

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

Chemistry

1

A classical gas law which states that when the pressure on a sample of a dry gas is held constant, the Kelvin temperature is directly proportional to its volume.

chelation

Chemistry

1

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

Chemistry

1

See chemical species and chemical compound.

chemical bond

Chemistry

1

See bond.

chemical composition

Chemistry

1

The identity and relative number of the elements that make up a chemical compound, which can often be expressed with a chemical formula.

chemical compound

Chemistry

1

See compound.

chemical decomposition

Chemistry

1

The breakdown of a single particle or entity (such as a molecule or reactive intermediate) into two or more fragments, or a chemical reaction in which two or more products are formed from a single reactant. Contrast chemical synthesis.

chemical element

Chemistry

1

See element.

chemical formula

Chemistry

1

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

Chemistry

1

A law of nature relevant to chemistry, such as the law of conservation of mass.

chemical process

Chemistry

1

1. Any method or means of changing one or more chemicals or chemical compounds in any way, either naturally or artificially, spontaneously or by the actions of external forces.

chemical reaction

Chemistry

1

A process in which one or more substances are changed into different substances.

chemical species

Chemistry

1

A chemical substance or ensemble of substances composed of chemically identical molecular entities which can explore the same set of molecular energy levels on a characteristic or delineated time scale.

chemical substance

Chemistry

1

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.

chemical synthesis

Chemistry

1

The artificial execution of one or more chemical reactions in order to obtain one or more products. In modern laboratory contexts, specific chemical syntheses are both reliable and reproducible.

chemistry

Chemistry

1

The scientific discipline that studies chemical substances, compounds, and molecules composed of atoms of various chemical elements, as well as their compositions, structures, properties, behaviors, and the changes they undergo during reactions with other substances.

chirality

Chemistry

1

A property of asymmetry in which a molecule or ion is distinguishable from its mirror image such that it cannot be superposed upon it by any combination of geometric rotations, translations, or some conformational changes. Such a molecule or ion is said to be chiral, and exists in two forms, known as enantiomers, which are stereoisomers of each other; these forms are distinguished as either "right-handed" or "left-handed" by their absolute configuration or some other criterion. Several different types of asymmetry can give rise to chirality, most commonly when molecules possess stereogenic elements such as one or more stereocenters (central chirality), a stereogenic axis (axial chirality), or a stereogenic plane (planar chirality); additionally, the inherent curvature of a molecule can cause it to possess inherent chirality.

chromometer

Chemistry

1

See colorimeter.

cohesion

Chemistry

1

The tendency of similar particles or surfaces to cling to one another as a result of intermolecular forces. Contrast adhesion.

colligative property

Chemistry

1

Any property of a solution 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. Examples include osmotic pressure, freezing-point depression, and boiling-point elevation.

colloid

Chemistry

1

A mixture in which microscopic insoluble particles are suspended within and evenly dispersed throughout another substance, usually a liquid but sometimes inclusive of aerosols and gels. Thus a colloid contains a dispersed phase and a continuous phase. Many milks are colloids.

color standard

Chemistry

1

A liquid solution of known chemical composition and concentration, and hence of known and standardized color, used as a reference in the optical analysis of samples of unknown strength.

color test

Chemistry

1

The quantitative analysis of a substance by comparing the intensity of the color produced when the substance is exposed to a reagent with a standard color produced similarly in a solution of known strength.

colorimeter

Chemistry

1

Any instrument used for color measurement based on optical comparison with standard colors, particularly a device used in colorimetry that measures the absorbance of specific wavelengths of light by a given solution in order to determine the concentration of a known solute in the solution, by application of the principle that solute concentration is directly proportional to absorbance.

combustion

Chemistry

1

A chemical reaction that involves the process of burning.

complex

Chemistry

1

A molecular entity formed by loose association between two or more component molecular entities (ionic or uncharged), or the corresponding chemical species. The bonding between the components is normally weaker than in a covalent bond. See also coordination complex.

compound

Chemistry

1

A pure substance made up of two or more different elements chemically combined.