kb/data/en.wikipedia.org/wiki/Glossary_of_chemistry_terms-8.md

title	chunk	source	category	tags	date_saved	instance
Glossary of chemistry terms	9/20	https://en.wikipedia.org/wiki/Glossary_of_chemistry_terms	reference	science, encyclopedia	2026-05-05T07:59:20.572989+00:00	kb-cron

environmental chemistry

enzyme A biological protein catalyst that speeds up a chemical reaction.

epimer

Eppendorf tube A generalized and trademarked name used to refer to a microcentrifuge tube.

equation of state

equilibrium 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 in a reacting system have stopped changing in time.

equimolar Having an equal number of moles, or solutions of equal molar concentration.

Erlenmeyer flask

ester A class of organic and inorganic compounds derived from the reaction of an acid with an alcohol, in which at least one hydroxyl group (–OH) is replaced by an alkoxy group (–O–). Esters have the general formula RCO2R′, where R and R' represent any alkyl or aryl group.

ether A class of organic compounds and a functional group containing an oxygen atom connected to two alkyl or aryl groups, which may be the same or different. Ethers have the general formula R–O–R′, where R and R′ represent the alkyl or aryl groups.

ethyl The alkyl functional group derived from ethane, consisting of two carbon atoms covalently bonded to each other and fully saturated with bonds to hydrogen atoms, with the chemical formula –CH2CH3. It is a common substituent in numerous organic compounds, though it may also exist independently as an ion or radical. In IUPAC nomenclature, the presence of an ethyl substituent may be indicated with the prefix ethyl in the name of the compound, or with the abbreviation Et in chemical formulae; e.g. ethyl alcohol (ethanol), which is often written with the formula CH3CH2OH or EtOH.

eutectic mixture A solid solution consisting of two or more substances which collectively have the lowest melting point of any possible mixture of these components.

evaporation

exothermic process

extensive property A physical quantity whose value is proportional to the size of the system it describes or to the quantity of matter in the system. Examples include mass, volume, enthalpy, and entropy. Contrast intensive property.

extraction

1. A separation process in which a component is separated from its mixture by selective solubility. See also partition.
2. The separation of a component analyte from a matrix.

extrinsic property

== F ==

family See group.

Faraday constant (F) A unit of electric charge widely used in electrochemistry equal to the negative of the molar charge (electric charge per mole) of electrons. It is equal to approximately 96,500 coulombs per mole (F = 96485.33212... C/mol).

Faraday's laws of electrolysis A set of two laws pertaining to electrolysis which hold that: a) the mass of a substance altered at an electrode during electrolysis is directly proportional to the quantity of electricity transferred at that electrode; and b) the mass of an elemental material altered at an electrode is directly proportional to the element's equivalent weight.

f-block

Fick's laws of diffusion

filtration Any physical, biological, or chemical operation that separates large particles (often solid matter) from smaller particles (often a fluid) by passing the mixture through a complex lattice structure through which only particles of a sufficiently small size can pass, called a filter. The fluid and small particles which successfully pass through the filter are called the filtrate.

fire point The lowest temperature at which the vapors above a volatile material will continue to burn for at least five seconds after ignition by an open flame of standard dimension. The fire point should not be confused with the flash point, a slightly lower temperature at which a substance will ignite briefly but at which vapor is not produced at a rate sufficient for sustained combustion.

first-order reaction

flash point The lowest temperature at which the vapors above a volatile material will ignite if given an ignition source. At the flash point, the application of an open flame causes only a momentary "flash" rather than sustained combustion, for which the ambient temperature is still too low. The flash point should not be confused with the fire point, which occurs at a slightly higher temperature, nor with the kindling point, which is higher still.

flask A vessel or container, most commonly a type of glassware, widely used in laboratories for a variety of purposes, such as preparing, holding, containing, collecting, and volumetrically measuring chemicals, samples, or solutions, or as a chamber in which a chemical reaction occurs. Flasks come in a number of shapes and sizes but are typically characterized by a relatively wide lower body which tapers into one or more narrower tubular sections with an opening at the top.

flocculation The process by which the dispersed particles in a colloid come out of suspension to aggregate into larger clumps known as floc or flake, either spontaneously or due to the addition of a clarifying agent. The term is often used to refer to a reversible aggregation in which the forces holding the particles together are weak and the colloid can be re-dispersed by agitation.

Florence flask See boiling flask.

formal charge (FC) The electric charge assigned to an atom in a molecule, assuming that all electrons in all bonds are shared equally between atoms, regardless of each atom's relative electronegativity. The formal charge of any atom that is part of a molecule can be calculated by the equation

    F
    C
    =
    V
    −
    N
    −
    
      
        B
        2
      
    
     
  

{\displaystyle FC=V-N-{\frac {B}{2}}\ }

, where

    V
  

{\displaystyle V}

is the number of valence electrons of the neutral atom in its ground state;

    N
  

{\displaystyle N}

is the number of valence electrons of the atom which are not participating in bonds in the molecule; and

    B
  

{\displaystyle B}

is the number of electrons shared in bonds with other atoms in the molecule.

formula weight (FW) A synonym for molar mass and molecular weight, frequently used for non-molecular compounds such as ionic salts.

fraction