OCR Chemistry a Level Y2 Glossary | Chemical Bond

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Glossary with all chemistry words
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   Year 2 Glossary OCR Chemistry A GlossaryA acid  a species that releases H+ ions in aqueous solution. acid dissociation constant K  a  the equilibrium constant that shows the extent of dissociation of a weak acid. For a weak acid HA(aq), K  a  = − + [H(aq)][A(aq)][HA(aq)] . acid–base pair   a pair of two species that transform into each other b !ain or lossof a proton. activation energy  the minimum ener! required to start a reaction b the breakin! of bonds. actual yield  the amount of product obtained from a reaction. addition polymerisation  formation of a er lon! molecular chain, b repeated addition reactions of man unsaturated alkene molecules (monomers). addition reaction  a reaction in which a reactant is added to an unsaturated molecule to make a one saturated molecule. adsorption  the process that occurs when a !as or liquid or solute is held to the surface of a solid. alicyclic  containin! carbon atoms #oined to!ether in a rin! that is not aromatic. aliphatic  containin! carbon atoms #oined to!ether in strai!ht or branched chains. alkali a tpe of base that dissol es in water formin! hdroxide ions, $H  % (aq) ions. alkanes  the hdrocarbon homolo!ous series with sin!le carbon&to&carbon bonds and the !eneral formula'  n H n+ . alkenes  the hdrocarbon homolo!ous series with at one double carbon&to&carbon bonds and the !eneral formula'  n H n . alkyl group  a side chain formed b remo in! a hdro!en atom remo ed from an alkane parent chain, for example, H*, H an alkl !roup is often shown as -. alkynes  the hdrocarbon homolo!ous series with one triple carbon&to&carbon bonds and the !eneral formula'  n H n% . amount of substance  the quantit whose unit of the mole, used as a means of countin! an species such as atoms, ions and molecules. anhydrous  containin! no water molecules. anion  a ne!ati el char!ed ion with more electrons than protons. aromatic  containin! one or more benene rin!s. / $xford 0ni ersit 1ress 234www.oxfordsecondar.co.uk5acknowled!ements 6his resource sheet ma ha e been chan!ed from the ori!inal   Year 2 Glossary OCR Chemistry A atom economy  (sum of molar masses of desired products)5(sum of molar massesof all products) 783229. atomic (proton) number   the number of protons in the nucleus of an atom. atomic orbital  a re!ion around the nucleus that can hold up to two electrons, withopposite spins. average bond enthalpy  the a era!e enthalp chan!e that takes place when breakin! b homoltic fission 3   mol of a !i en tpe of bond in the molecules of a !aseous species. Avogadro constant N  A  the number of atoms per mole of the carbon&3 isotope. (4.2 : 32 *   mol  %3 ). B base  a compound that neutralises an acid to form a salt. binary compound  a compound containin! two elements onl. bond angle  the an!le between two bonds at an atom. bond dissociation enthalpy  the enthalp chan!e that takes place when breakin!b homoltic fission 3   mol of a !i en bond in the molecules of a !aseous species. bonded pair   a pair of electrons shared between two atoms to make a co alent bond. Brønsted–o!ry acid  a species that is a proton, H + , donor. Brønsted–o!ry base  a species that is a proton, H + , acceptor. buffer solution  a sstem that minimises pH chan!es on addition of small amounts of an acid or a base. C carbocation  an ion that contains a positi el char!ed carbon atom. catalyst  a substance that increases the rate of a chemical reaction without bein! used up in the process a catalst pro ide an alternati e route for the reaction withlower acti ation ener!. cation  a positi el char!ed ion with fewer electrons than protons. chain reaction  a reaction in which the propa!ation steps release new radicals that continue the reaction. chemical shift δ   a scale, in ppm, that compares the frequenc of an ;<- absorption with the frequenc of the reference 6< at δ   = 2   ppm. chiral carbon  a carbon atom attached to four different atoms or !roups of atoms. / $xford 0ni ersit 1ress 234www.oxfordsecondar.co.uk5acknowled!ements 6his resource sheet ma ha e been chan!ed from the ori!inal   Year 2 Glossary OCR Chemistry A chromatogram  a isible record showin! the result of separation of the components of a mixture b chromato!raph. cis–trans  isomerism  a special tpe of E  5 Z   isomerism in which there are two non&hdro!en !roups and two hdro!en atoms around the = double bond' the cis  isomer ( Z   isomer) has H atoms on each carbon on the same side the trans  isomer ( E   isomer) has H atoms on each carbon on different sides. closed system  a sstem isolated from its surroundin!s. collision theory  two reactin! particles must collide for a reaction to occur, and must be in the correct orientation and ha e sufficient ener! to o ercome the acti ation ener! of the reaction. comple ion  a transition metal ion bonded to li!ands b coordinate bonds (dati e co alent bonds). concentration  the amount of solute, in moles, dissol ed in 3   dm *  (3222   cm * ) of solution. condensation   reaction  a reaction in which two small molecules react to!ether to form a lar!er molecule with elimination of a small molecule such as water. con#ugate acid  a species that releases a proton to form a con#u!ate base. con#ugate base  a species that accepts a proton to form a con#u!ate acid. coordinate bond  a shared pair of electrons in which the bonded pair has been pro ided b one of the bondin! atoms onl also called a dati e co alent bond. coordination number   the total number of coordinate bonds formed between a central metal ion and li!ands. covalent bond  the stron! electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms. D dative covalent  a shared pair of electrons in which the bonded pair has been pro ided b one of the bondin! atoms onl also called a coordinate bond. dehydration  an elimination reaction in which water is remo ed from a saturated molecule to make an unsaturated molecule. delocalised electrons  electrons that are shared between more than two atoms. desorption  release of an adsorbed substance from a surface. dipole  a separation in electrical char!e so that one atom of a polar co alent bond,or one end of a polar molecule, has a small positi e char!e >+ and the other has asmall ne!ati e char!e >%. / $xford 0ni ersit 1ress 234www.oxfordsecondar.co.uk5acknowled!ements 6his resource sheet ma ha e been chan!ed from the ori!inal   Year 2 Glossary OCR Chemistry A displacement reaction  a reaction in which a more reacti e element displaces a less reacti e element from an aqueous solution of its ions. displayed formula  a formula showin! the relati e positionin! of all the atoms in a molecule and the bonds between them. disproportionation  a redox reaction in which the same element is both oxidised and reduced. dynamic e$uilibrium  the equilibrium that exists in a closed sstem when the rate of the forward reaction is equal to the rate of the re erse reaction and concentrations do not chan!e. E E   % Z   isomerism  a tpe of stereoisomerism in which different !roups attached to each carbon of a = double bond ma be arran!ed differentl in space because of the restricted rotation of the = bond. electron configuration  a shorthand representation that shows how electrons occup sub&shells in an atom. electronegativity  a measure of the attraction of a bonded atom for the pair of electrons in a co alent bond. electrophile  an atom (or !roup of atoms) which is attracted to an electron&rich centre or atom, where it accepts a pair of electrons to form a new co alent bond. electrophilic addition  an addition reaction in which the first step is attack b an electrophile on a re!ion of hi!h electron densit. electrophilic substitution  a tpe of substitution reaction in which an electrophile is attracted to an electron&rich centre or atom, where it accepts a pair of electrons to form a new co alent bond. elimination reaction  the remo al of a molecule from a saturated molecule to make an unsaturated molecule. empirical formula  the formula that shows the simplest whole&number ratio of atoms of each element present in a compound. enantiomers  stereoisomers that are nonsuperimposable mirror ima!es of each other also called optical isomers. end point  the point in a titration where the indicator chan!es colour the end point indicates when the reaction is #ust complete. endothermic reaction  a reaction in which the enthalp of the products is !reater than the enthalp of the reactants, resultin! in heat bein! taken in from the / $xford 0ni ersit 1ress 234www.oxfordsecondar.co.uk5acknowled!ements 6his resource sheet ma ha e been chan!ed from the ori!inal
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