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manometer | Chemistry | 1 | An instrument used to measure pressure invented by Evangelista Torricelli in 1643. |
masking agent | Chemistry | 1 | A reagent used in a chemical analysis which reacts with one or more other chemical species that may interfere in the analysis. |
mass | Chemistry | 1 | A property of physical matter that is a measure of its resistance to acceleration when a net force is applied. The SI unit for mass is the kilogram (kg). |
mass number | Chemistry | 1 | The total number of protons and neutrons (together known as nucleons) within the nucleus of an atom. It determines the atomic mass of the atom. Mass number varies between different isotopes of the same chemical element, and is often included either after the element's name (as in carbon-12) or as a superscript to the left of the element's symbol (as in 12C) to identify a specific isotope. |
a | Chemistry | 1 | The total number of protons and neutrons (together known as nucleons) within the nucleus of an atom. It determines the atomic mass of the atom. Mass number varies between different isotopes of the same chemical element, and is often included either after the element's name (as in carbon-12) or as a superscript to the left of the element's symbol (as in 12C) to identify a specific isotope. |
mass spectrometry | Chemistry | 1 | An analytical technique measuring the characteristics of individual molecules by converting them to ions. |
ms | Chemistry | 1 | An analytical technique that measures the mass-to-charge ratio of ions in a chemical sample by bombarding the sample with electrons to the point of ionization and then separating the charged fragments by subjecting them to an electric or magnetic field, typically in order to determine the elemental or isotopic signatures of an unknown substance, the masses of its constituent particles, and/or the identities or structures of the molecules within it. The results are presented as a mass spectrum, a plot of the intensity of ion signals as a function of the mass-to-charge ratio. |
matter | Chemistry | 1 | Any substance that has mass and takes up space by having volume. |
metal | Chemistry | 1 | Any chemical element which is a good conductor of both electricity and heat and which readily forms cations and ionic bonds with non-metals. |
melting | Chemistry | 1 | The phase transition of a substance from a solid to a liquid. |
melting point | Chemistry | 1 | The temperature at which a substance changes state from a solid to a liquid. It depends on pressure and is usually specified for a given substance under standard conditions. The melting point of a substance is identical to its freezing point. |
mercaptan | Chemistry | 1 | See thiol. |
mercapto | Chemistry | 1 | See thiol. |
metalloid | Chemistry | 1 | An element that exhibits some properties of metals and non-metals. These elements tend to be semiconductors (e.g. silicon). |
metamer | Chemistry | 1 | See isomer. |
metathesis | Chemistry | 1 | A class of chemical reaction involving the exchange of elements or functional groups between two or more compounds, as described by the general equation A X + B Y → A Y + B X {\textstyle \mathrm {{AX}+{BY}} \rightarrow \mathrm {{AY}+{BX}} } . Examples include alkane metathesis, alkyne metathesis, olefin metathesis, and salt metathesis reaction. See also double displacement. |
methyl | Chemistry | 1 | The alkyl functional group derived from methane, consisting of one carbon atom bonded to three hydrogen atoms, with the chemical formula CH3. It is the simplest hydrocarbon and occurs as a substituent in numerous organic compounds, though it may also exist independently as an ion or radical. In IUPAC nomenclature, the presence of a methyl substituent is indicated with the prefix methyl in the name of the compound, or with the abbreviation Me in chemical formulae; e.g. methyl alcohol (methanol) is often written with the formula CH3OH or MeOH. |
methylene blue | Chemistry | 1 | A heterocyclic aromatic compound with the molecular formula C16H18N3SCl. |
microcentrifuge tube | Chemistry | 1 | A small plastic, sealable container that is used to store small volumes of liquid, generally less than 2 milliliters. |
mineral | Chemistry | 1 | A solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form. |
miscibility | Chemistry | 1 | The tendency or capability of two or more substances to blend uniformly when combined (most commonly liquids, though the concept is also applicable to solids and gases), i.e. to dissolve in each other, forming a homogeneous mixture that exists in a single phase, without separation of phases, regardless of the proportions of each substance. Substances that do not mix uniformly in all proportions are said to be immiscible. |
mixture | Chemistry | 1 | 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 either substance into new substances). |
moiety | Chemistry | 1 | Any named characteristic group, branch, or other part of a large molecule that may be identified within other kinds of molecules as well. Functional groups are typically smaller and more generic than moieties, whereas substituents and side chains may often be classified as moieties and vice versa. |
molal concentration | Chemistry | 1 | A measure of the concentration of a solute in a solution in terms of the amount of solute per unit mass of solvent. Molality is typically expressed in units of moles per kilogram (mol/kg); a solution with a concentration of exactly 1 mol/kg is sometimes said to be 1 molal. Contrast molarity. |
molar concentration | Chemistry | 1 | A measure of the concentration of a chemical species, especially of a solute in a solution, in terms of the amount of the species per unit volume of solution. Molarity is typically expressed in units of moles per litre (mol/L); a solution with a concentration of exactly 1 mol/L is commonly said to be 1 molar, abbreviated 1 M. Contrast molality. |
molar mass | Chemistry | 1 | For a given chemical compound, the mass of a sample of that compound divided by the amount of compound in the sample, usually expressed in grams per mole (g/mol). As a bulk property, molar mass is an average of the masses of many instances of the compound, each of which may vary slightly due to the presence of isotopes of the compound's constituent atoms; it is commonly derived from the compound's molecular weight, which itself is a sum of the standard atomic weights of the constituent atoms, and is therefore a function of the relative abundance of the isotopes as they occur naturally on Earth. Molar mass allows easy conversion between mass and number of moles when considering bulk quantities of a substance. |
molarity | Chemistry | 1 | See molar concentration. |
mole | Chemistry | 1 | A unit (symbol: mol) used to measure the amount of a substance in terms of the absolute number of particles or entities composing the substance. By definition, one mole of any substance contains exactly the Avogadro number (i.e. 6.022×1023) of particles or entities. |
mol | Chemistry | 1 | A unit (symbol: mol) used to measure the amount of a substance in terms of the absolute number of particles or entities composing the substance. By definition, one mole of any substance contains exactly the Avogadro number (i.e. 6.022×1023) of particles or entities. |
molecular orbital | Chemistry | 1 | Any region in which one or more electrons may be found in a molecule (as opposed to that within an individual atom). |
mo | Chemistry | 1 | Any region in which one or more electrons may be found in a molecule (as opposed to that within an individual atom). |
molecule | Chemistry | 1 | A number of atoms that are chemically bonded together and collectively electrically neutral. |
monatomic | Chemistry | 1 | Having only one atom, as opposed to a molecule composed of more than one. Virtually all elements are monatomic in the gas phase at sufficiently high temperatures. Contrast diatomic and polyatomic. |
neat | Chemistry | 1 | Conditions with a liquid reagent or gas performed with no added solvent or cosolvent. |
neutron | Chemistry | 1 | A type of subatomic particle that is electrically neutral, having no net charge. |
noble gas | Chemistry | 1 | 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 with valence electrons in their naturally occurring states, giving them very low or negligible chemical reactivity. |
non-metal | Chemistry | 1 | A chemical element that forms acidic oxides and is a poor conductor of heat and electricity (e.g. sulfur). |
nonpolar compound | Chemistry | 1 | A compound consisting of covalent molecules with no permanent dipole moment. Contrast polar compound. |
nuclear | Chemistry | 1 | Of or pertaining to the atomic nucleus. |
nuclear chemistry | Chemistry | 1 | The branch of chemistry that studies the various processes and properties relevant to atomic nuclei, including radioactivity. |
nuclear magnetic resonance spectroscopy | Chemistry | 1 | A technique that exploits the magnetic properties of certain atomic nuclei, useful for identifying unknown compounds. Nuclear magnetic resonance is often abbreviated NMR. |
nucleon | Chemistry | 1 | Either a proton or a neutron, considered in its role as a component of an atomic nucleus. |
nucleophile | Chemistry | 1 | Any atom or molecule which can donate an electron pair to another atom or molecule. All molecules or ions with a free pair of electrons or at least one pi bond can act as nucleophiles, by which they are attracted to electron-deficient regions of other species; a chemical reaction involving a nucleophile donating an electron pair to an electrophile may be referred to as nucleophilic attack. Because they donate electrons, nucleophiles are Lewis bases by definition. |
nucleus | Chemistry | 1 | The centre of an atom, made up of neutrons and protons and possessing a net positive electric charge. |
nuclide | Chemistry | 1 | 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 | Chemistry | 1 | A measure of the concentration of countable objects (atoms, molecules, etc.) in space, expressed as the number per unit volume. |
octet rule | Chemistry | 1 | 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. |
olefin | Chemistry | 1 | A trivial (non-IUPAC) name for any alkene. |
orbital | Chemistry | 1 | Any region of an atom or molecule in which one or more electrons can be found. The term may refer to either an atomic orbital or a molecular orbital. |
organic acid | Chemistry | 1 | Any organic compound with acidic properties. Contrast organic base. |
organic base | Chemistry | 1 | Any organic compound with basic properties. Contrast organic acid. |
organic chemistry | Chemistry | 1 | The study of the compounds of carbon, excluding the oxides of carbon and the inorganic metal compounds known as bicarbonates, carbonates and cyanides. |
organic compound | Chemistry | 1 | Any chemical compound that contains one or more carbon atoms. Contrast inorganic compound. |
organosulfur compound | Chemistry | 1 | Any chemical compound which contains both carbon and sulfur atoms. |
osmosis | Chemistry | 1 | The spontaneous net movement or diffusion of molecules of a solvent (e.g. water) through a selectively permeable membrane separating two solutions with different concentrations of dissolved solutes, in the direction that tends to equalize the solute concentrations on the two sides, i.e. from the more dilute solution to the more concentrated solution, or, equivalently, from a region of high water potential to a region of low water potential. Because the solute is unable to cross the membrane, the tendency towards equilibration compels the solvent to cross the membrane instead. This continues until an equilibrium is reached, where neither side of the membrane is more or less concentrated than the other. |
other metal | Chemistry | 1 | Any of the metallic elements in the p-block, which are 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 | Chemistry | 1 | Any chemical process involving the removal of electrons from an element or compound. |
oxidation state | Chemistry | 1 | 1. The degree of oxidation of an individual atom in a chemical compound, measured as the decrease in the number of electrons relative to the atom's naturally occurring elemental state. |
oxidizing agent | Chemistry | 1 | 1. A chemical species that gains or accepts one or more electrons from another species, called the reducing agent, in a redox reaction, thereby causing the oxidation of the other species and in turn being itself reduced. The oxidizing agent's oxidation state decreases, while the reducing agent's increases. |
oxoacid | Chemistry | 1 | 1. Any acid having oxygen in the acidic group. |
paired electron | Chemistry | 1 | One of two electrons that together form a valence bond between two atoms. Contrast unpaired electron. |
paraffin | Chemistry | 1 | 1. A trivial (non-IUPAC) name for any alkane. |
passivation | Chemistry | 1 | The process of coating a substance with a thin layer of a protective material, often a metal oxide, to create a shield against corrosion or other chemical reactions with the environment, thereby rendering the coated substance "passive" or less susceptible to undesirable reactions. |
passivity | Chemistry | 1 | A state of chemical inactivity, especially of a metal that is relatively resistant to corrosion due to natural or induced loss of chemical reactivity (as with passivation). See also inert. |
pendant group | Chemistry | 1 | An offshoot or side chain of the backbone of a polymeric molecule, especially one which is itself neither oligomeric or polymeric. |
pentabasic | Chemistry | 1 | (of a chemical compound) Having five hydrogen atoms which may be replaced by metals or bases. |
pentoxide | Chemistry | 1 | Any binary compound containing five atoms of oxygen, e.g. iodine pentoxide (I2O5). |
pentyl | Chemistry | 1 | An alkyl functional group containing five carbon atoms, with the generic chemical formula –C5H11. It is the substituent form of the alkane pentane. |
per- | Chemistry | 1 | A prefix in IUPAC chemical nomenclature meaning complete, exhaustive, or extreme, as in a completely substituted hydrocarbon; or indicating the presence of a peroxy group. |
peracid | Chemistry | 1 | An acid containing an acidic peroxy group (–O–O–); e.g. periodic acid. |
period | Chemistry | 1 | A horizontal row of the periodic table of the elements and the elements that share it. Contrast group. |
periodic table of the elements | Chemistry | 1 | 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. |
peroxide | Chemistry | 1 | 1. A class of compounds which contain a peroxy group, having the generic structural formula R–O–O–R, where R is any element or functional group; e.g. hydrogen peroxide (empirically H2O2, structurally H–O–O–H). |
peroxy | Chemistry | 1 | A functional group consisting of two oxygen atoms directly connected to each other by a single bond and each also connected to one other atom. Peroxides have the general structural formula –O–O–. |
ph | Chemistry | 1 | A measure of the acidity or alkalinity of a substance, based on a scale of 0 to 14. Acidic solutions have pH values less than 7, whereas alkaline solutions have pH values greater than 7. |
phase | Chemistry | 1 | A region of space throughout which all physical properties of a substance are essentially uniform, or a region of material that is chemically uniform, physically distinct, and often mechanically separable. The term phase may have several different uses in chemistry contexts; colloquially, it is often used interchangeably with state of matter, but many distinct phases may exist within a single state of matter. |
phase diagram | Chemistry | 1 | A graphical representation of the equilibrium relationships between thermodynamically distinct phases of a chemical compound, mixture, or solution, indicating the physical conditions (e.g. temperature and pressure) under which various phases (e.g. solid, liquid, and vapor) occur or coexist. |
phase transition | Chemistry | 1 | 1. A transformation of a chemical substance between solid, liquid, and gaseous states of matter and, in rare cases, plasma. |
phenyl | Chemistry | 1 | A functional group consisting of a cyclic ring of six carbon atoms with the chemical formula –C6H5. It is the substituent form of the cycloalkane benzene. |
photon | Chemistry | 1 | A carrier of electromagnetic radiation of all wavelengths (such as gamma rays and radio waves). |
physical chemistry | Chemistry | 1 | The branch of chemistry that studies chemical systems in terms of the principles, practices, and concepts of physics, such as motion, energy, force, time, thermodynamics, chemical equilibrium, and statistical mechanics, among others. In contrast to chemical physics, physical chemistry is predominantly (though not entirely) a macroscopic science that studies the physical and chemical interactions of bulk quantities of matter. |
pipette | Chemistry | 1 | A laboratory tool commonly used in chemistry, biology, and medicine to transfer and dispense a precisely measured volume of liquid. |
plasma | Chemistry | 1 | 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. |
pnictogen | Chemistry | 1 | Any of the chemical elements belonging to Group (V) of the periodic table: nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb), bismuth (Bi), and moscovium (Ms). These elements are united by their common pentavalency; i.e. in their non-ionized states, atoms of these elements all have exactly five valence electrons in their outermost electron shell, three short of a complete octet. |
polyatomic | Chemistry | 1 | Composed of two or more atoms, of the same or different elements. Contrast monatomic and diatomic. |
polyatomic ion | Chemistry | 1 | A molecule composed of two or more covalently bonded atoms which collectively bear a net electric charge and therefore act as an ion. |
polymerization | Chemistry | 1 | The chemical bonding of two or more individual monomer molecules to form a polymer chain or network; or any reaction that produces such a bonding. |
potential energy | Chemistry | 1 | The stored energy in a body or in a system due to its position in a force field or due to its configuration. |
precipitant | Chemistry | 1 | A chemical compound or reagent that causes a chemical reaction resulting in the formation of a solid precipitate when added to a solution. |
precipitate | Chemistry | 1 | 1. (n.) A solid substance that separates from a liquid solution or diffuses out of a solid alloy during the process of precipitation. |
precipitation | Chemistry | 1 | The process of producing a separable solid phase within a liquid medium, e.g. by transforming the dissolved solute of a supersaturated solution into an insoluble solid; or the diffusion of a distinct solid phase out of a solid alloy. A reagent that causes such a reaction is called the precipitant, and the separable solid itself is the precipitate. More generally, the term may refer to the formation of any new condensed phase by changing the physical properties of a system (e.g. water vapor condensing into liquid water droplets). |
precision | Chemistry | 1 | How close the results of multiple experimental trials or observations are to each other. Compare accuracy. |
pressure | Chemistry | 1 | The force applied perpendicular to the surface of an object per unit area. The SI unit for pressure is the pascal (Pa), though many other units of pressure are also commonly used in chemistry. |
primary | Chemistry | 1 | The simplest, most commonly known, or canonical form of a chemical compound with multiple similar or isomeric forms. For example, in a primary alcohol, the carbon is bonded to a single substituent group (R1CH2OH), whereas a secondary alcohol is doubly substituted (R1R2CHOH) and a tertiary alcohol is triply substituted (R1R2R3COH). |
propyl | Chemistry | 1 | The alkyl functional group derived from either of the two isomers of propane, with the generic chemical formula –C3H7. It may occur as a substituent in organic compounds or exist independently as an ion or radical. In IUPAC nomenclature, the presence of a propyl substituent is indicated with the prefix propyl in the name of the compound, or with the abbreviation Pr in chemical formulae; e.g. propyl alcohol (propanol) may occur in either of two isomeric forms, either the linear 1-propanol or n-propanol, written CH3CH2CH2OH, or the branched 2-propanol or isopropyl alcohol, written (CH3)2CHOH, and both forms may be written with the generic formula PrOH. A third, non-isomeric, cyclic form known as cyclopropyl is also sometimes considered a propyl group. |
protic | Chemistry | 1 | (of a chemical species) Capable of acting as a proton donor; readily generating or yielding free protons (H+) in solution. Protic species may therefore be considered strongly or weakly acidic in the sense of a Brønsted–Lowry acid. |
proton | Chemistry | 1 | A subatomic particle with a positive electric charge that is found in the nucleus of an atom. Often denoted with the symbol H+. |
protonation | Chemistry | 1 | The addition of a proton (H+) to an atom, molecule, or ion. |
pure substance | Chemistry | 1 | See chemical substance. |
pyrolysis | Chemistry | 1 | The thermal decomposition of materials at elevated temperatures in an inert atmosphere such as a vacuum gas. |
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