OCR F322 Heineman

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Empirical Formula
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The simplest whole number ratio of atoms of each element present in a compound
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Molecular Formula
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The actual number of atoms of each element in a molecule
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General Formula
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The simplest algebraic formula of a member of a homologous series. For example, the general formula of the alkanes is CnH2n+2
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Structural Formula
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Shows the minimal detail for the arrangement of atoms in a molecule
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Displayed Formula
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Shows the relative positioning of all the atoms in a molecule and the bonds between them
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Skeletal Formula
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A simplified organic formula, with hydrogen atoms removed from alkyl chains, leaving just a carbon skeleton and associated functional groups
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Homologous Series
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A series of organic compounds with the same functional group but with each successive member differing by CH2
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Functional Group
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The part of the organic molecule responsible for its chemical reactions
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Structural Isomers
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Molecules with the same molecular formula but with different structural arrangements of atoms
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Stereoisomers
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Compounds with the same structural formula, but with a different arrangement of the atoms in space
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E/Z Isomerism
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An example of stereoisomerism, in terms of restricted rotation about a double bond and the requirement for two different groups to be attached to each carbon atom of the C=C group
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Cis-Trans Isomerism
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A special type of E/Z isomerism in which two of the substituent groups are the same
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Hydrocarbons
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Organic compounds that contain carbon and hydrogen only
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Saturated Hydrocarbon
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A hydrocarbon with single bonds only
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Unsaturated Hydrocarbon
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A hydrocarbon containing carbon-to-carbon multiple bonds
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Aliphatic Hydrocarbon
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A hydrocarbon with carbon atoms joined together in straight or branched chains
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Alicyclic Hydrocarbon
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A hydrocarbon with carbon atoms joined together in a ring structure
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Alkanes
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The homologous series with the general formula: CnH2n+2
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Nomenclature
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A system of naming compounds
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Alkyl Group
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An alkane with a hydrogen atom removed, e.g. CH3, C2H5; Aany alkyl group is often shown as R
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Homolytic Fission
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The breaking of a covalent bond, with each of the bonded electrons going to each atom, forming two radicals.
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Radical
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A species with an unpaired electron.
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Heterolytic Fission
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The breaking of a covalent bond with both of the bonded electrons going to one of the atoms, forming a cation (+ ion) and an anion (- ion)
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Nucleophile
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An atom (or group of atoms) that is attracted to an electron-deficient centre or atom, where it donates a pair of electrons to form a new covalent bond
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Electrophile
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An atom (or group of atoms) that is attracted to an electron rich centre or atom, where it accepts a pair of electrons to form a new covalent bond
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Addition Reaction
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A reaction in which a reactant is added to an unsaturated molecule to make a saturated molecule
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Substitution Reaction
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A reaction in which an atom or group of atoms is replaced with a different atom or group of atoms

In a substitution reaction:
2 reactants —> 2 products

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Elimination Reaction
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Refers to the removal of a molecule from a saturated molecule to make an unsaturated molecule

In an elimination reaction:
1 reactant —> 2 products

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Fractional Distillation
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The separation of the components in a liquid mixture into fractions which differ in boiling point (and hence chemical composition) by means of distillation, typically using a fractionating column
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Cracking
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Refers to the breaking down of long-chained saturated hydrocarbons to form a mixture of shorter-chained alkanes and alkenes
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Catalyst
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A substance that increases the rate of a chemical reaction without being used up in the process
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Radical Substitution
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A type of substitution reaction in which a radical replaces a different atom or group of atoms
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Mechanism
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A sequence of steps showing the path taken by electrons in a reaction
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Initiation
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The first step in a radical substitution in which the free radicals are generated by Ultraviolet Radiation
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Propagation
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The two repeated steps in radical substitution that build up the products in a chain reaction
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Termination
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The step at the end of a radical substitution when two radicals combine to form a molecule
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Pi-bond (? bond)
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The reactive part of a double bond formed above and below the plane of the bonded atoms by sideways overlap of p-orbitals
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Electrophilic addition
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A type of addition reaction in which an electrophile is attracted to an electron deficient centre or atom, where it accepts a pair of electrons to form a new covalent bond
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Carbocation
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An organic ion in which a carbon atom has a positive charge
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Curly Arrow
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A symbol used in reaction mechanisms to show the movement of an electron pair in the breaking or formation of a covalent bond
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Polymer
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A long molecular chain built up from monomer units
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Monomer
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A small molecule that combines with many other monomers to form a polymer
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Addition polymerisation
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The process in which unsaturated alkene molecules (monomers) add on to a growing polymer chain one at a time to form a very long saturated molecular chain (the addition polymer)
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Atom Economy
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{Molecular Mass of the desired products/ Sum of molecular masses of all products} X 100
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Activation Energy
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The minimum energy required to start a reaction by the breaking of bonds
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Standard Conditions
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A pressure of 100 kPa (1 atmosphere), a stated temperature, usually 298K (25C), and a concentration of 1 mol dm^-3 (for reactions with aqueous solutions)
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Enthalpy change of reaction
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The enthalpy change that accompanies a reaction in the molar quantities expressed in a chemical equation under standard conditions, all reactants and products being in their standard states
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Enthalpy change of Formation
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The enthalpy change that takes place when one mole of a compound in its standard state is formed from its constituent elements in their standard states under standard conditions
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Enthalpy change of combustion
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The enthalpy change that takes place when one mole of a substance reacts completely with oxygen under standard conditions, all reactants and products being in their standard states
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Exothermic reaction
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A reaction in which the enthalpy of the products is smaller than the enthalpy of the reactants, resulting in heat loss to the surroundings (?H -ve)
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Endothermic reaction
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A reaction in which the enthalpy of the products is greater than the enthalpy of the reactants, resulting in heat being taken in from the surroundings (?H +ve)
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Average bond enthalpy
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The average enthalpy change that takes place when breaking by homolytic fission 1 mol of a give type of bond in the molecules of a gaseous species
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le Chatelier’s principle
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When a system in dynamic equilibrium is subjected to a change, the position of equilibrium will shift to minimise the change

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