OCR A level Chemistry Definitions Flashcards

5985499093	Activation Energy	The minimum energy required to start a reaction by breaking bonds in the reactants	0
5985500643	Addition Polymer	A very long molecular chain formed by repeated addition reactions of many unsaturated alkene molecules	1
5985502772	Addition Reaction	A reaction in which a reactant is added to an unsaturated molecule to make a saturated molecule	2
5985508911	Acid Dissociation Constant	Ka= [H+(aq)][A-(aq)]/[HA(aq)]	3
5985521899	Aliphatic Hydrocarbon	A hydrocarbon where carbon atoms are joined together in straight or branched chains	4
5985523014	Alkali	A base that dissolves in water forming OH- ions	5
5985523698	Alkanes	The homologous series with general formula CnH2n+2	6
5985526779	Alkylammonium salt	A compound where the hydrogen's on an ammonium ion have been substituted by alkyl chains	7
5985529325	Alkylation	Addition of hydrocarbon chains to an organic compound	8
5985530837	Alkyl group	An alkane with a hydrogen atom removed e.g. CH3, C2H5	9
5985531784	Amide	A compound with a functional group made of an alcyl group, which is directly attached to an amine	10
5985534940	Amphoteric chemicals	Chemicals that can react with both acids and bases	11
5985536116	Anion	A negatively charged ion	12
5985536447	Anhydrous	A substance that contains no water molecules	13
5985537573	Arrhenius plot	A graph of lnK = lnA - Ea/R x 1/T	14
5985539967	Atomic Orbital	A region of space where you will likely find electrons. Each orbital can hold 2 electrons, with opposite spins	15
5985542285	Atomic number	The number of protons in the nucleus of an atom	16
5985543119	Average bond enthalpy	The mean energy needed for 1 mole of a given type of gaseous bonds to undergo homolytic fission	17
5985546058	Avogadro constant	The number of atoms per mole of the carbon-12 isotope (6.02x10^23)	18
5985547609	Base	A chemical that will react with an acid	19
5985549732	Benzene	A naturally occurring aromatic compound, which is very stable planar ring structure with delocalized electrons	20
5985555220	Benzene Derivative	A benzene ring that has undergone a substitution reaction	21
5985556612	Boltzman Distribution	The distribution of energies of molecules at a particular temperature	22
5985558192	Bronsted-Lowry acid	A proton donor	23
5985560735	Bronsted- Lowry base	A proton acceptor	24
5985563428	Buffer solution	A mixture that minimizes pH changes on addition of small amounts of acid or base	25
5985565290	Carbocation	An organic ion in which a carbon atom has a positive charge	26
5985567250	Catalyst	A substance that increases the rate of a reaction by providing an alternative route to start the reaction with lower activation energy, without being used up in the process	27
5985570176	Cation	A positively charged ion	28
5985570820	Chemical Shift	The scale that compares the frequency of NMR absorption with the frequency of the reference peak of TMS	29
5985572300	Chiral Carbon	A carbon with 4 different groups attached to it	30
5985574255	Chromatogram	A visible record showing the result of separation of the components of a mixture by chromatography	31
5985578364	Cis-trans isomerism	A type of E/Z isomerism where each carbon of the C=C double bond carries the same atom or group	32
5985583185	Complex ion	A transition metal ion bonded to one or more ligands by dative covalent bonds	33
5985595561	Condensation polymer	The chemical reaction to form a long chain molecule by elimination of a small molecule e.g. water	34
5985597581	Conjugate acid-base pair	Two species that transform into each other by the gain or loss of a proton	35
5985599889	Coordination number	The total number of dative covalent bonds formed between a central metal ion and its ligands	36
5985601396	Covalent bond	A bond formed by a shared pair of electrons between nuclei	37
5985602886	Curly arrow	A symbol used in reaction mechanisms to show the movement of an electron pair	38
5985604550	Dative covalent bond	A bond formed by a shared pair of electrons that has been provided by one of the bonding atoms only (AKA coordinate bond)	39
5985606899	Degradable polymer	A polymer that breaks down into smaller fragments when exposed to light, heat or moisture	40
5985609085	Delocalised electrons	Electrons that are shared between more than 2 atoms	41
5985611060	Deuterium	An isotope of hydrogen and does not produce a signal in proton NMR	42
5985612771	Directing effect	How a functional group attached directly to an aromatic ring affects which carbon atoms are more likely to undergo substitution	43
5985615033	Displayed formula	A formula which shows the relative positions of atoms and the bonds between them	44
5985616754	Disproportionation	The oxidation and reduction of the same element in a redox reaction	45
5985617336	Distillation	A technique used to separate miscible liquids or solutions	46
5985618793	Dynamic Equilibrium	The equilibrium that exists in a closed system when the rate of the forward reaction is equal to the rate of the reverse reaction and all the chemicals have their concentrations maintained	47
5985621208	Electron configuration	The arrangement of electrons in an atom or ion	48
5985624812	Electrophile	An electron pair acceptor	49
5985626796	Electrophilic substitution	A substitution reaction where an electrophile is attracted to an electron rich atom or part of a molecule and a new covalent bond is formed by the electrophile accepting a pair of electrons	50
5985631186	Elimination reaction	An organic chemical reaction in which one reactant forms 2 products, usually a small molecule is released	51
5985633423	Empirical formula	The simplest whole number ratio of atoms of each element present in a compound	52
5985635139	Enantiomer	An optical isomer	53
5985635480	Endothermic	A reaction in which the enthalpy of products is greater than the enthalpy of reactants, so heat is taken in from the surroundings (positive delta H)	54
5985639860	End point	The point in a titration at which there are equal concentrations of the weak acid and conjugate base forms of the indicator	55
5985641896	Enthalpy cycle	A diagram showing alternative routes between reactants and products	56
5985644508	Enthalpy profile diagram	A diagram of a reaction that allows you to compare the enthalpy of the reactants with the enthalpy of the products	57
5985646823	Enthalpy, H	The heat content that is stored in a chemical system	58
5985648019	Entropy, S	A measure of disorder in a system	59
5985649161	Equivalence point	The point in a titration at which the volume of one solution has reacted exactly with the volume of the second solution. This matches the stoichiometry of the reaction taking place	60
5985661898	Equivalent carbon atoms	Carbon atoms bonded to the same atoms that therefore experience the same magnetic field in the NMR	61
5985667182	Equivalent protons	Hydrogen atoms bonded to the same atoms that therefore experience the same magnetic field in the NMR	62
5985754472	Esterification	The chemical reaction which forms an ester	63
5985757057	Exothermic	A reaction in which the enthalpy of the products is smaller than the enthalpy of the reactants, so heat is lost (negative delta H)	64
5985767082	E/Z isomerism	A type of stereoisomerism that is caused by the restriction of rotation around the double bond. 2 different groups are attached to each carbon atom of the C=C bond	65
5985775585	First electron affinity	The enthalpy change when 1 mole of gaseous 1- ions are formed from gaseous atoms	66
5985778298	First ionization energy	The energy change when 1 mole of electrons is removed from 1 mole of gaseous atoms to from 1 mole of gaseous 1+ ions	67
5985781479	Free energy change, delta G	Delta G= delta H-T x delta S. The reaction can take place when delta G<0	68
5985785159	Friedel Crafts reaction	A substitution reaction where hydrogen is exchanged for an alkyl or alcyl chain. They allow electrophilic substitution to occur on an aromatic ring	69
5985787284	Functional group	A group of atoms that is responsible for the characteristic chemical reactions of a compound	70
5985788227	General formula	The simplest algebraic formula for a homologous series	71
5985789545	Geometric/stereo isomers	Molecules that have the same structural formula but a different arrangement in space	72
5985792165	Giant ionic lattice	3D structure of atoms that are all bonded together by strong covalent bonds	73
5985793938	Giant metallic lattice	3D structure of positive ions and delocalized electrons, bonded together by strong metallic bonds	74
5985795192	Half-life	The time taken for the concentration of a reactant to reduce by half	75
5985796485	Hess' Law	States that the enthalpy change in a chemical reaction is independent of the route it takes	76
5985797962	Heterogeneous equilibrium	An equilibrium in which species making up the reactants and products are in different physical states	77
5985799593	Homogenous equilibrium	An equilibrium in which all species making up the reactants and products are the same physical state	78
5985801240	Homologous series	A series of organic compounds that have the same functional group with successive members differing by CH2	79
5985804805	Hydrolysis	A chemical reaction where water is a reactant in a decomposition reaction	80
5985806885	Intermediate	A species formed in one step of a multi-step reaction that is used up in a subsequent step, and is not seen in the overall equation	81
5985808508	Ionic bonding	The electrostatic attraction between oppositely charged ions	82
5985810063	Kw	[H+(aq)][OH-(aq)]. At 25c Kw=1.00x10^-14	83
5985812166	Isoelectric point	The pH value at which the amino acid exists as a zwitterion	84
5985813370	Lattice enthalpy	The enthalpy change when one mole of an ionic lattice is formed from its gaseous ions under standard conditions	85
5985817670	Le Chatelier's principle	States that when a system in dynamic equilibrium is subjected to change, the position of equilibrium will shift to minimize the change	86
5985819453	Lewis acid	An electron pair acceptor	87
5985819854	Ligand	A molecule or ion that can donate a pair of electrons to the transition metal ion to form a coordinate bond	88
5985824476	Ligand substitution	A reaction in which one ligand in a complex ion is replaced by another ligand	89
5985825332	Lone pair	An outer shell pair of electrons that is not involved in chemical bonding	90
5985827169	Mass number	The number of protons and neutrons in a nucleus	91
5985828573	Mobile phase	The phase that moves in chromatography	92
5985830562	Moles	n= MxMr	93
5985833197	Mole fraction	A measure of how much of a given substance is present in a reaction mixture	94
5985844971	Molecular formula	Shows the numbers and type of the atoms of each element in a compound	95
6012876754	Molecular ion	The positive ion formed in mass spectrometry when a molecule loses an electron	96
6012878065	Monomers	Small molecules used to make polymers	97
6012879224	Neutralisation	A chemical reaction in which an acid and a base react together to produce a salt and water	98
6012880920	Nitrile	An organic chemical with a -CN group	99
6012881766	Nucleophile	A species that contains a lone pair of electrons or a negative charge and is attracted to positive areas of a molecule	100
6012884003	Optical isomers	Molecules that are non-superimposable mirror images of each other. They have the same chemical properties but interact with polarized light differently	101
6012886743	Order	With respect to a reactant, the order is the power to which the concentration of the reactant is raised in the rate equation	102
6012888825	Overall order	The sum of the individual orders	103
6012889905	Oxidation	Loss of electrons, or an increase in oxidation number	104
6012890923	Oxidation number	A measure of the number of electrons that an atom uses to bond with atoms of another element	105
6012892159	Oxidising agent	The species that is reduced in a reaction and causes another species to be oxidised	106
6012893953	Partial pressure	The pressure an individual gaseous substance would exert if it occupied a whole reaction vessel on its own	107
6012895095	Phase	A physically distinctive form of a substance	108
6012896038	Phenols	A class of aromatic compounds where a hydroxyl group is directly attached to the aromatic ring	109
6012897327	pH	-log[H+(aq)]	110
6012898528	Pi bond	The sideways overlap of adjacent p-orbitals above and below the bonding C atoms	111
6012899550	Polar molecule	A molecule with an overall dipole, having taken into account any dipoles across bonds	112
6012901731	Polymer	A macromolecule made from small repeating monomers	113
6012902844	Precipitation reaction	A formation of a solid from a solution during a chemical reaction	114
6012904414	Qualitative analysis	An observable change and does not involve observations using numerical values	115
6012905583	Rate constant, k	The constant that links the rate of reaction with the concentrations of reactants raised to the powers of their orders in the rate equation	116
6012907604	Rate determining step	The slowest step in the reaction mechanism of a multi-step reaction	117
6012909257	Rate equation	rate= k[A]^m[B]^n	118
6012910501	Rate of reaction	The change in concentration of a reactant or product per unit time	119
6012912172	Reaction mechanism	A series of steps that make up the overall reaction or a model with steps to explain and predict a chemical reaction	120
6012914151	Recyrstallisation	A method for purifying organic compounds	121
6012914701	Redox reaction	A reaction in which both reduction and oxidation take place	122
6012916554	Reducing agent	The species that is oxidized in a reaction and causes another species to be reduced	123
6012917640	Reduction	Gain of electrons, or a decrease in oxidation number	124
6012927656	Reflux	A technique to stop reaction mixtures boiling dry	125
6012928755	Relative molecular mass	The weighted men mass of a molecule of a compound compared with one-twelfth of the mass of an atom of carbon 12	126
6012931048	Repeat unit	The arrangement of atoms that occurs many times in a polymer	127
6012931904	Retention time	The time taken for a component to travel from the inlet to the detector in a gas chromatograph	128
6012933701	Retro-synthesis	Where the synthetic route is designed by looking at the target molecule and working backwards	129
6012934566	Rf value	A comparison between how far a component has moved compared to the solvent in TLC	130
6012937062	Salt	Any chemical compound formed from an acid when an H+ ion from the acid has been replaced by a metal ion or another positive ion, often a metal or ammonium ion, NH4+	131
6012940765	Saturated hydrocarbon	A hydrocarbon with single bonds only	132
6012941793	Second electron affinity	The enthalpy change when 1 mole of gaseous 2- ions forms from 1 mole of gaseous 1- ions	133
6012943042	Second ionization energy	The energy change when 1 mole of gaseous 2+ ions forms from 1 mole of gaseous 1+ ions	134
6012947483	Shell	A group of atomic orbitals with the same principal quantum number	135
6012949453	Skeletal formula	A simplified structural formula drawn by removing hydrogen atoms from alkyl chains	136
6012951749	Spectator ions	Ions that are present but that play no part in a chemical reaction	137
6012952526	Spin-spin coupling	The interaction between spin states of non-equivalent nuclei that results in a group of peaks in an NMR spectrum	138
6012955160	Standard conditions	100kPa, 298K	139
6012957013	Standard electrode potential of a half cell	The e.m.f. of half a cell compared with a standard hydrogen half cell, measured at 298K with solution concentrations of 1 moldm-3 and 100kPa	140
6012960578	Standard enthalpy change of atomisation	The enthalpy change when 1 mole of gaseous atoms is formed from its element in its standard state	141
6012962622	Standard enthalpy change of formation	The enthalpy change when 1 mole of a compound is formed from it elements	142
6012964746	Standard enthalpy change of hydration	The enthalpy change when 1 mole of gaseous ions is dissolved in water	143
6012966309	Standard enthalpy change of solution	The enthalpy change when one mole of a solute is completely dissolved in water under standard conditions	144
6012967768	Standard entropy	The entropy content of one mole of a substance under standard conditions	145
6012969149	Standard entropy change of reaction	The entropy change when a reaction in the molar quantities expressed in a chemical equation happens under standard conditions, with all reactants and products being in their standard states	146
6012973020	Stationary phase	The phase that does not move in chromatography	147
6012976176	Stereoisomers	Species with the same structural formula but with a different arrangement of atoms in space	148
6012977175	Stoichiometry	The molar relationship between the relative quantities of substances taking part in a reaction	149
6012982358	Strong acid	An acid that completely dissociates in solution	150
6012985211	Structural isomers	Compounds with the same molecular formula but different structural formula	151
6012986874	Sub-shell	A group of the same type of atomic orbitals within a shell	152
6012988453	Substitution reaction	When an atom or group of atoms is replaced by a different atom or group of atoms	153
6012990233	Synthetic route	A series of reactions that can be used to change a starting chemical into a target molecule	154
6012992318	TMS	An internal standard for both carbon and proton NMR	155
6013000387	Transition metal	A d-block element that has an incomplete d-sub shell as a stable ion	156
6013002723	Unsaturated hydrocarbon	A hydrocarbon containing multiple carbon carbon double bonds	157
6013004536	Van der Waals force	Intermolecular bonding that includes permanent dipole-dipole bonding and induced dipole-dipole interactions	158
6013007700	Water of Crystallisation	Water molecules that form an essential part of the crystalline structure of a compound	159
6013009211	Weak acid	An acid that partially dissociates in solution	160
6013010229	Zwitterion	An internal salt, with no charge, formed by the donation of a proton from a carboxylic acid group to an amine group in an amino acid	161