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Glossary of Chemistry Terms
beginning with letter H
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hafnium Tweet Definition of hafnium Like Definition of hafnium on Facebook
noun
  1. a metallic chemical element (symbol Hf) with an atomic number of 72.
hahnium Tweet Definition of hahnium Like Definition of hahnium on Facebook
noun
  1. original name of the transuranic element dubnium
halide Tweet Definition of halide Like Definition of halide on Facebook
noun
  1. (chemistry) A salt of any halogen acid.
Potassium iodide is a .
halocarbon Tweet Definition of halocarbon Like Definition of halocarbon on Facebook
noun
  1. (chemistry) any compound formally derived from a hydrocarbon by replacing at least one hydrogen atom with a halogen, but especially by replacing all hydrogen atoms with halogen(s)
halogen Tweet Definition of halogen Like Definition of halogen on Facebook
noun
  1. (chemistry) Any element of group 7, i.e. fluorine, chlorine, bromine, iodine and astatine, which form a salt by direct union with a metal.
halogenate Tweet Definition of halogenate Like Definition of halogenate on Facebook
verb (halogenates, halogenating, halogenated, halogenated)
  1. (context, chemistry, transitive) To treat with, or react with, a halogen or a hydrohalic acid.
hard Tweet Definition of hard Like Definition of hard on Facebook
adjective
  1. Resistant to pressure.
  2. Requiring a lot of effort to do or understand
a hard problem
  1. Demanding a lot of effort to endure.
a hard life
  1. (context, of a person) , severe, harsh, unfriendly, brutal.
  2. Unquestionable.
hard evidence
  1. Of drink, strong.
  2. Of water, high in dissolved calcium compounds.
  3. (context, slang, vulgar) Sexually aroused.
  4. (bodybuilding) Having muscles that are tightened as a result of intense, regular exercise.
adverb (harder, hardest)
  1. With much strength or energy
hardness Tweet Definition of hardness Like Definition of hardness on Facebook
noun
  1. The quality of being hard.
  2. An instance of this quality; hardship.
hard water Tweet Definition of hard water Like Definition of hard water on Facebook
noun
  1. (chemistry) water with a high concentration of dissolved minerals, especially calcium, making it difficult to lather with soap
HDPE Tweet Definition of HDPE Like Definition of HDPE on Facebook
initialism
  1. High Density Polyethylene category:Initialisms
HE Tweet Definition of HE Like Definition of HE on Facebook
abbreviation
  1. His Excellency, Her Excellency
  2. His Eminence
  3. high explosive
  4. Higher Education
  5. Health Education
heavy Tweet Definition of heavy Like Definition of heavy on Facebook
noun (pl2=heavies)
  1. A villain or bad guy; the one responsible for evil or aggressive acts.
With his wrinkled, uneven face, the actor always seemed to play the in films.
  1. (slang) A doorman, bouncer
A fight started outside the bar then the heavies came out and stopped it.
adjective (heavier, heaviest)
  1. (context, of a physical object) Having great weight.
  2. (context, of a topic) serious, Serious, somber.
  3. (context, UK, slang) Good.
This film is .
  1. (context, of a rate of flow) high, High, great.
  2. (context, UK, slang) Armed.
Come , or not at all.
  1. (context, Music terminology) louder, more distorted
''Metal is heavier than swing.
heavy hydrogen Tweet Definition of heavy hydrogen Like Definition of heavy hydrogen on Facebook
noun (uncountable)
  1. Another name for deuterium.
helium Tweet Definition of helium Like Definition of helium on Facebook
noun
  1. A colorless and inert gas, and the second lightest chemical element (symbol He) with an atomic number of 2 and atomic weight of 4.002602.
hemiacetal Tweet Definition of hemiacetal Like Definition of hemiacetal on Facebook
noun
  1. (chemistry) any of a class of compounds of general formula R2C(OH)OR' (where R' is not H)
hemicellulose Tweet Definition of hemicellulose Like Definition of hemicellulose on Facebook
noun
  1. (chemistry) a mixture of several plant polysaccharides, of smaller molecular weight than cellulose, that are soluble in dilute alkali; they are involved in the manufacture of paper, and are used in the production of furfural and ethanol
heptad Tweet Definition of heptad Like Definition of heptad on Facebook
noun
  1. a group of seven things
heptane Tweet Definition of heptane Like Definition of heptane on Facebook
noun
  1. (organic compound) Any of the nine isomers of the saturated aliphatic hydrocarbon C7H16, obtained from petroleum, especially n-heptane (CH3(CH2)5CH3)
hetero Tweet Definition of hetero Like Definition of hetero on Facebook
noun
  1. (informal) A heterosexual person.
heteroaromatic Tweet Definition of heteroaromatic Like Definition of heteroaromatic on Facebook
adjective
  1. (chemistry) having the characteristics of an aromatic compound whilst having at least one non-carbon atom in the ring
heteroatom Tweet Definition of heteroatom Like Definition of heteroatom on Facebook
noun
  1. (chemistry) any atom in a heterocyclic ring (or other structure normally built of carbon atoms) that is not a carbon atom
heterocyclic Tweet Definition of heterocyclic Like Definition of heterocyclic on Facebook
adjective
  1. (organic chemistry) Of a cyclic compound that contains one or more atoms other than carbon in at least one of its rings.
heterogeneous Tweet Definition of heterogeneous Like Definition of heterogeneous on Facebook
adjective
  1. diverse, Diverse in kind or nature; composed of diverse parts.
  2. (mathematics) incommensurable, Incommensurable because of different kinds.
  3. (physics): Having more than one phase (solid, liquid, gas) present in a system or process.
  4. (chemistry): Visibly consisting of different components.
  5. (information technology): A network comprising different types of computers, potentially with vastly differing memory sizes, processing power and even basic underlying architecture. Alternatively, a data resource with multiple types of formats.
heteropolar Tweet Definition of heteropolar Like Definition of heteropolar on Facebook
adjective
  1. Of an electric generator that produces alternating current
  2. (chemistry) Formed by ions of opposite charge
hexabasic Tweet Definition of hexabasic Like Definition of hexabasic on Facebook
adjective
  1. (chemistry) (of an acid) containing six replaceable hydrogen atoms
  2. (chemistry) (of a salt) having six atoms of a univalent metal
hexafluoride Tweet Definition of hexafluoride Like Definition of hexafluoride on Facebook
noun
  1. (chemistry) any fluoride containing six fluorine atoms in each molecule
hexane Tweet Definition of hexane Like Definition of hexane on Facebook
noun
  1. (organic compound) Any of five isomeric aliphatic hydrocarbons, C6H14. They are colorless, volatile liquids.
hexavalent Tweet Definition of hexavalent Like Definition of hexavalent on Facebook
adjective
  1. (chemistry) having a valence of 6
hexose Tweet Definition of hexose Like Definition of hexose on Facebook
noun
  1. (carbohydrate) A sugar or saccharide containing six carbon atoms.
Glucose is a common
hf Tweet Definition of hf Like Definition of hf on Facebook
abbreviation
  1. (Internet) have fun
ho Tweet Definition of ho Like Definition of ho on Facebook
noun (hoes)
  1. (context, pejorative, slang) A woman who engages in prostitution.
holmium Tweet Definition of holmium Like Definition of holmium on Facebook
noun
  1. a metallic chemical element (symbol Ho) with an atomic number of 67.
homocyclic Tweet Definition of homocyclic Like Definition of homocyclic on Facebook
adjective
  1. (chemistry) describing a cyclic system in which all the atoms of the ring are of the same element
homologous Tweet Definition of homologous Like Definition of homologous on Facebook
adjective
  1. Showing a degree of correspondence or similarity such that it suggests a common origin.
  1. (biology) corresponding to a similar structure in another life form with a common evolutionary origin e.g. flippers and hands
  2. (chemistry) belonging to a series of aliphatic organic compounds that differ only by the addition of a CH2 group
  3. (genetics) having the same morphology as another chromosome
    1. homologous blood donation
hydracid Tweet Definition of hydracid Like Definition of hydracid on Facebook
noun
  1. (chemistry) An acid that does not contain any oxygen as opposed to an oxyacid; they are all binary compounds of hydrogen and a halogen or pseudohalogen.
hydrargyrum Tweet Definition of hydrargyrum Like Definition of hydrargyrum on Facebook
noun
  1. (chemistry) (medicine) The element mercury.
hydrate Tweet Definition of hydrate Like Definition of hydrate on Facebook
noun
  1. (chemistry) A solid compound containing or linked to water molecules.
  2. (context, inorganic compound, rare) water, Water.
verb (hydrat, ing)
  1. (transitive) To take up, consume or become linked to water.
A lotion can the skin.
hydrated Tweet Definition of hydrated Like Definition of hydrated on Facebook
adjective
  1. (chemistry) Chemical combinated with water, H2O, in its molecular form.
We took the powdered milk and it until it was drinkable.
hydrazine Tweet Definition of hydrazine Like Definition of hydrazine on Facebook
noun
  1. (context, inorganic compound, uncountable) A corrosive, fuming liquid, NH2-NH2, used as a rocket fuel.
  2. (context, organic chemistry, countable) Any member of the class of organic compounds formally derived from it.
hydrazone Tweet Definition of hydrazone Like Definition of hydrazone on Facebook
noun
  1. (chemistry) any compound, of general formula R2C=NNR2, formally derived from an aldehyde or ketone by replacing the carbonyl group with =NNH2 or derivative
hydric Tweet Definition of hydric Like Definition of hydric on Facebook
adjective
  1. Characterized by, or requiring moisture
  2. (chemistry) Of, or relating to hydrogen
hydride Tweet Definition of hydride Like Definition of hydride on Facebook
noun
  1. (chemistry) a compound of hydrogen with a more electropositive element
hydriodic acid Tweet Definition of hydriodic acid Like Definition of hydriodic acid on Facebook
noun
  1. (chemistry) a solution of hydrogen iodide, HI, in water; it is a strong acid and reducing agent
hydrobromic Tweet Definition of hydrobromic Like Definition of hydrobromic on Facebook
adjective
  1. (chemistry) Composed of hydrogen and bromine
hydrobromic acid Tweet Definition of hydrobromic acid Like Definition of hydrobromic acid on Facebook
noun
  1. (inorganic compound) A solution of hydrogen bromide, HBr, in water; it is a strong acid, used in the production of bromine compounds.
hydrocarbon Tweet Definition of hydrocarbon Like Definition of hydrocarbon on Facebook
noun
  1. (organic chemistry) A compound consisting primarily of carbon and hydrogen atoms.
hydrochloric Tweet Definition of hydrochloric Like Definition of hydrochloric on Facebook
adjective
  1. (chemistry) Of or relating to hydrochloric acid.
hydrochloric acid Tweet Definition of hydrochloric acid Like Definition of hydrochloric acid on Facebook
noun
  1. (chemical compound) A strong acid made by dissolving the gas, hydrogen chloride, in water. It reacts with alkalis, bases and many metals to form chlorides; it has many industrial applications'
hydrochloride Tweet Definition of hydrochloride Like Definition of hydrochloride on Facebook
noun
  1. (chemistry) A compound of hydrochloric acid with an organic base such as an amine
hydrocyanic acid Tweet Definition of hydrocyanic acid Like Definition of hydrocyanic acid on Facebook
noun (or prussic acid)
  1. (chemistry) a solution of hydrogen cyanide, HCN, in water; a weak poisonous acid, used as a fumigant
hydrodesulfurization Tweet Definition of hydrodesulfurization Like Definition of hydrodesulfurization on Facebook
noun
  1. (chemistry) a process for lowering the sulfur content of petroleum and similar products by catalytic hydrogenation, sulfur compounds being converted to hydrogen sulfide
hydrofluoric Tweet Definition of hydrofluoric Like Definition of hydrofluoric on Facebook
adjective
  1. (chemistry) Containing hydrogen and fluorine.
hydrofluoric acid Tweet Definition of hydrofluoric acid Like Definition of hydrofluoric acid on Facebook
noun
  1. (chemistry) A solution of hydrogen fluoride, HF, in water; it is a weak but very corrosive acid, used in the production of fluorine compounds, and in metallurgy.
hydroformylation Tweet Definition of hydroformylation Like Definition of hydroformylation on Facebook
noun
  1. (chemistry) the reaction of an olefin with carbon monoxide and hydrogen to form an aldehyde
hydrogen Tweet Definition of hydrogen Like Definition of hydrogen on Facebook
noun
  1. The lightest chemical element (symbol H) with an atomic number of 1 and atomic weight of 1.00794.
  2. Molecular hydrogen (H2), a colourless, odourless and flammable gas at room temperature.
hydrogen bond Tweet Definition of hydrogen bond Like Definition of hydrogen bond on Facebook
noun
  1. (chemistry) a weak bond in which a hydrogen atom in one molecule is attracted to an electronegative atom (usually nitrogen or oxygen) in the same or different molecule
hydrogen bromide Tweet Definition of hydrogen bromide Like Definition of hydrogen bromide on Facebook
noun
  1. (inorganic compound) A colourless gas having an irritating smell; it has the molecular formula HBr, and dissolves in water to form hydrobromic acid; it has many industrial applications including the production of barbiturates and synthetic hormones.
hydrogen chloride Tweet Definition of hydrogen chloride Like Definition of hydrogen chloride on Facebook
noun
  1. (inorganic compound) An inorganic compound with the formula HCl. Forms hydrochloric acid when dissolved in water.
hydrogen cyanide Tweet Definition of hydrogen cyanide Like Definition of hydrogen cyanide on Facebook
noun
  1. (chemistry) A colourless, very poisonous, volatile liquid, HCN, used in the production of dyes, plastics and fumigants; it dissolves in water to form hydrocyanic acid and reacts with bases to form cyanides, and with some organic compounds to form nitriles.
hydrogen fluoride Tweet Definition of hydrogen fluoride Like Definition of hydrogen fluoride on Facebook
noun
  1. (chemistry) a colourless fuming liquid or gas, having a molecular formula of HF; it dissolves in water to form hydrofluoric acid and has many industrial uses including the production of teflon and the refining of uranium; it corrodes skin, flesh and bone, and any skin contact must be avoided
hydrogen iodide Tweet Definition of hydrogen iodide Like Definition of hydrogen iodide on Facebook
noun
  1. (chemistry) a colourless gas with molecular formula HI, having a suffocating smell; it forms hydriodic acid when dissolved in water
hydrogen ion Tweet Definition of hydrogen ion Like Definition of hydrogen ion on Facebook
noun
  1. (chemistry) a proton combined with one or more water molecules; usually written H3O+ and called the hydronium ion though is best considered as H9O4+ but is often written H+(aq) for simplicity
hydrogenolysis Tweet Definition of hydrogenolysis Like Definition of hydrogenolysis on Facebook
noun
  1. (chemistry) the cleavage of a molecule, especially that of a carbon-carbon bond, with the addition of hydrogen atoms to the fragments
hydrogenous Tweet Definition of hydrogenous Like Definition of hydrogenous on Facebook
adjective
  1. of, related to, or containing hydrogen
hydrogen peroxide Tweet Definition of hydrogen peroxide Like Definition of hydrogen peroxide on Facebook
noun
  1. (chemical compound) A colourless liquid, H2O2, soluble in water, used as a mild antiseptic, bleaching agent (especially for bleaching hair), oxidizing agent and chemical reagent.
hydrogen sulfide Tweet Definition of hydrogen sulfide Like Definition of hydrogen sulfide on Facebook
noun
  1. (chemical compound) A toxic gas, H2S, smelling like rotten eggs and used in analytical chemistry and industry.
hydrolysis Tweet Definition of hydrolysis Like Definition of hydrolysis on Facebook
noun
  1. a chemical process of decomposition involving the splitting of a bond and the addition of the hydrogen cation and the hydroxide anion of water
hydrolyze Tweet Definition of hydrolyze Like Definition of hydrolyze on Facebook
verb (hydrolyz, ing) (transitive and intransitive)
  1. (chemistry) to undergo, or to subject something to hydrolysis
hydroperoxide Tweet Definition of hydroperoxide Like Definition of hydroperoxide on Facebook
noun
  1. (chemistry) any mono-substituted derivative of hydrogen peroxide - ROOH
hydrophilic Tweet Definition of hydrophilic Like Definition of hydrophilic on Facebook
adjective
  1. (physics),(chemistry) having an affinity for water; able to absorb, or be wetted by water
hydrophobic Tweet Definition of hydrophobic Like Definition of hydrophobic on Facebook
adjective
  1. (physics),(chemistry) lacking an affinity for water; unable to absorb, or be wetted by water
    1. of, or having hydrophobia (rabies)
hydroquinone Tweet Definition of hydroquinone Like Definition of hydroquinone on Facebook
noun
  1. (organic compound) The diphenol para-dihydroxy benzene, used as a mild reducing agent in photographic developing; isomeric with catechol and resorcinol.
hydrosulfide Tweet Definition of hydrosulfide Like Definition of hydrosulfide on Facebook
noun
  1. (chemistry) any compound formally derived from hydrogen sulfide by replacing one hydrogen atom with a metal or other radical; a thiol or mercaptan
  2. (chemistry) the HS- anion
hydrosulfite Tweet Definition of hydrosulfite Like Definition of hydrosulfite on Facebook
noun
  1. (chemistry) dithionite
hydrous Tweet Definition of hydrous Like Definition of hydrous on Facebook
adjective
  1. (chemistry) containing combined water; hydrated
hydroxide Tweet Definition of hydroxide Like Definition of hydroxide on Facebook
noun
  1. (chemistry) An univalent anion (OH-1) based on the hydroxyl functional group.
  2. Any substance containing such an anion.
hydroxy acid Tweet Definition of hydroxy acid Like Definition of hydroxy acid on Facebook
noun