OCR Chemistry A F322 Definitions (All)

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  • Created by: Cherry
  • Created on: 03-06-13 10:39
Hydrocarbon
A compound of hydrogen and carbon only.
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Saturated Hydrocarbon
A hydrocarbon with single bonds only.
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Unsaturated Hydrocarbon
A hydrocarbon containing carbon-to-carbon multiple bonds.
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Aliphatic Hydrocarbon
A hydrocarbon with carbon atoms joined together in straight or branched chains.
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Alicyclic Hydrocarbon
A hydrocarbon with carbon atoms joined together in a ring structure.
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Functional Group
The part of the organic molecule responsible for its chemical reactions.
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Homologous Series
A series of organic compounds with the same functional group but with each successive member differing by CH2.
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Alkanes
The homologous series with the general formula CnH2n+2.
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Nomenclature
A system of naming compounds.
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Alkyl Group
An alkane with a hydrogen atom removed e.g. CH3 - often shown as 'R'.
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General Formula
The simplest algebraic formula of a member of a homologous series.
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Displayed Formula
Shows the relative positioning of all the atoms in a molecule and the bonds between them.
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Structural Formula
The minimal detail for the arrangement of atoms in a molecule.
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Skeletal Formula
The simplified organic formula, with hydrogen atoms removed from alkyl chains, leaving just a carbon skeleton and associated functional groups.
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Structural Isomers
Molecules with the same molecular formula but with different structural arrangements of atoms.
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Stereoisomers
Compounds with the same structural formula, but with a different arrangement of atoms in space.
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E/Z Isomerism
A type of stereoisomerism in which different groups attached to each carbon of a C=C double bond may be arranged differently in space because of the restricted rotation of the C=C bond.
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cis-trans Isomerism
Special type of E/Z isomerism - there is a non-hydrogen group and hydrogen on each C of a C=C double bond. Cis (Z) isomer has the H atoms on each carbon on the same side; the trans (E) isomer has the H atoms on each carbon on different sides.
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Homolytic Fission
The breaking of a covalent bond, with one of the bonded electrons going to each atom, forming two radicals.
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Heterolytic Fission
The breaking of a covalent bond with both of the bonded electrons going to one of the atoms, forming a cation (+) and an anion (-).
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Radical
A species with an unpaired electron.
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Nucleophile (AS definition)
Electron pair donor.
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Electrophile (AS definition)
Electron pair acceptor.
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Addition Reaction
A reaction in which a reactant is added to an unsaturated molecule to make a saturated molecule. ( 2 reactants ------ 1 product)
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Substitution Reaction
A reaction in which an atom or group of atoms is replaced with a different atom or group of atoms. (2 reactants ------ 2 products)
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Elimination Reaction
The removal of a molecule from a saturated molecule to make an unsaturated molecule. (1 reactant ------ 2 products)
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Fractional Distillation
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
The breaking down of long-chained saturated hydrocarbons to form a mixture of shorter-chained alkanes and alkenes.
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Isomerisation
A process whereby straight-chained alkanes are converted into branched alkanes.
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Reforming
A process whereby aliphatic hydrocarbons are converted into cyclic or aromatic hydrocarbons (hydrogen gas is also produced).
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Catalyst
A substance that increases the rate of a chemical reaction, by lowering the activation energy required, by providing an alternative route for the reaction, without being used up in the process.
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Radical Substitution
A type of substitution reaction in which a radical replaces a different atom or group of atoms.
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Mechanism
A sequence of steps showing the path taken by electrons in a reaction.
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Initiation
The first step in a radical substitution, in which the free radicals are generated by UV radiation.
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Propagation
The two repeated steps in radical substitution that build up the products in a chain reaction.
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Termination
The step at the end of a radical substitution when two radicals combine to form a molecule.
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Pi-bond
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
A type of addition 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 covalent bond.
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Carbocation
An organic ion in which a carbon atom has a positive charge.
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Curly Arrow
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
A long molecular chain built up from monomer units.
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Monomer
A small molecule that combines with many other monomers to form a polymer.
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Addition Polymerisation
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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Addition Polymer
A very long molecular chain formed by repeated addition reactions of many unsaturated alkene molecules (monomers).
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Repeat Unit
A specific arrangement of atoms that occurs in the structure over and over again. Repeat units are included in brackets, outside of which is the symbol n.
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Biodegradable Material
A substance that is broken down naturally in the environment by living organisms.
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Volatility
The ease that a liquid turns into a gas. Volatility increases as boiling point decreases.
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Reflux
The continual boiling and condensing of a reaction mixture to ensure that the reaction takes place without the contents of the flask boiling dry.
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Esterification
The reaction of an alcohol with a carboxylic acid to produce an ester and water.
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Dehydration
An elimination reaction in which water is removed from a saturated molecule to make an unsaturated molecule.
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Hydrolysis
A reaction with water or aqueous hydroxide ions that breaks a chemical compound into two compounds.
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Nucleophilic Substitution
A type of substitution reaction in which a nucleophile 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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% Yield
Actual amount, in mol, of product / Theoretical amount, in mol, of product x 100
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Limiting Reagent
The substance in a chemical reaction that runs out first.
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Atom Economy
Molecular mass of the desired product
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Limiting Reagent
The substance in a chemical reaction that runs out first.
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Atom Economy
Molecular mass of the desired product / Sum of molecular masses of all products x 100
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Molecular ion, M+
The positive ion formed in mass spectrometry when a molecule loses an electron.
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Fragmentation
The process in mass spectrometry that causes a positive ion to split into pieces, one of which is a positive fragment ion.
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Enthalpy,H
The heat content that is stored in a chemical system.
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Exothermic
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
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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Enthalpy Profile Diagram
A diagram for a reaction to compare the enthalpy of the reactants with the enthalpy of the products.
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Activation Energy
The minimum energy required to start a reaction by the breaking of bonds.
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Standard Conditions
A pressure of 100 kPa (1 atmosphere), a stated temperature, usually 298 K (25 °C), and a concentration of 1 mol dm–3 (for reactions with aqueous solutions).
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Standard State
The physical state of a substance under the standard conditions of 100 kPa (1 atmosphere) and 298 K (25 °C).
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(standard) Enthalpy Change of Reaction, ∆Hrө
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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(standard) Enthalpy Change of Combustion, ∆Hcө
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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(standard) Enthalpy Change of Formation, ∆Hfө
The enthalpy change that takes place when one mole of a compound is formed from its constituent elements in their standard states under standard conditions.
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Specific Heat Capacity, c
The energy required to raise the temperature of 1 g of a substance by 1 °C.
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Bond Enthalpy
The enthalpy change that takes place when breaking by homolytic fission 1 mol of a given bond in the molecules of a gaseous species.
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Average Bond Enthalpy
The average enthalpy change that takes place when breaking by homolytic fission 1 mol of a given type of bond in the molecules of a gaseous species.
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Hess' Law
States that, If a reaction can take place by more than one route and the initial and final conditions are the same, the total enthalpy change is the same for each route.
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Enthalpy Cycle
A diagram showing alternative routes between reactants and products which allows the indirect determination of an enthalpy change from other known enthalpy changes using Hess’ law.
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Rate of Reaction
The change in concentration of a reactant or product in a given time.
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Heterogeneous Catalysis
A reaction in which the catalyst has a different physical state from the reactants; frequently, reactants are gases whilst the catalyst is a solid.
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Homogeneous Catalysis
A reaction in which the catalyst and reactants are in the same physical state, which is most frequently the aqueous or gaseous state.
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Boltzmann Distribution
The distribution of energies of molecules at a particular temperature, usually shown as a graph.
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le Chatelier's Principle
States that, 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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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.
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Greenhouse Effect
The process in which the absorption and subsequent emission of infrared radiation by atmospheric gases warms the lower atmosphere and the planet’s surface.
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Troposphere
The lowest layer of the Earth’s atmosphere, extending from the Earth’s surface up to about 7 km (above the poles) and to about 20 km (above the tropics).
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Stratosphere
The second layer of the Earth’s atmosphere, containing the ‘ozone layer’, about 10 km to 50 km above the Earth’s surface.
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Adsorption
The process that occurs when a gas, liquid or solute is held to the surface of a solid or, more rarely, a liquid.
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Fuel
A substance that is burned to produce heat
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Biofuel
A fuel produced from plant or animal waste.
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Other cards in this set

Card 2

Front

A hydrocarbon with single bonds only.

Back

Saturated Hydrocarbon

Card 3

Front

A hydrocarbon containing carbon-to-carbon multiple bonds.

Back

Preview of the back of card 3

Card 4

Front

A hydrocarbon with carbon atoms joined together in straight or branched chains.

Back

Preview of the back of card 4

Card 5

Front

A hydrocarbon with carbon atoms joined together in a ring structure.

Back

Preview of the back of card 5
View more cards

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