WJEC Chemistry: Unit 2- Definitions

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Exothermic
Releases energy to its surroundings
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Endothermic
Takes in energy from its surroundings
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Enthalpy
The heat content of a system at constant pressure
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Hess's Law
The total enthalpy change for a reaction is independent of the route taken
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Homogenous Catalyst
A catalyst in the same phase as the reactants
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Heterogenous Catalyst
A catalyst in a different phase from the reactants
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Carbon Neutrality
When a chemical process leads to no net production of CO2
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Functional Group
The atom/group of atoms that gives a compound its characteristic properties
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Homologous Series
A series of compounds with the same functional group
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Structural Isomer
A compound with the same molecular formula but different structural formulae
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E-Z Isomerism
Isomerism in alkenes due to the restricted rotation about its double bond
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Complete Combustion
Combustion that occurs with excess oxygen
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Halogenation
A reaction with any halogen
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Initiation
The reaction that starts the halogenation process
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Propagation
The reaction by which the process continues
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Termination
The reaction that ends the halogenation process
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Homolytic Bond Fission
When a bond is broken and each of the bonded atoms receives one of the bonded electrons
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Heterolytic Bond Fission
When a bond is broken and one of the bonded atoms receives both the bonded electrons
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Radical
A species with an unpaired electron
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Reaction Mechanism
A diagram showing the stages of a reaction
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Substitution Reaction
A reaction in which one atom/group is replaced by another atom/group
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Addition Reaction
A reaction in which reagants combine to give one product
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Electrophile
An electron-deficient species that can accept a lone pair of electrons
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Nucleophile
A species with a lone pair of electrons that can be donated to an electron deficient species
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Polymerisation
The joining of a very large number of monomer molecules to make a large polymer molecule
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Halogenoalkane
An alkane in which one or more hydrogen atoms have been replaced by a halogen
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Reflux
A continuous process of evaporation and condensation
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Hydrolysis
A reaction with water to produce a new product
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Elimination Reaction
A reaction that involves the loss of a small molecule to produce a double bond
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CFCs
Halogenoalkanes containing both chlorine and fluorine atoms
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HFCs
Halogenoalkanes containing fluorine as the only halogen
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Fermentation
An enzyme-catalysed reaction that converts sugars to ethanol
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Classification of Alcohols
Classification into primary, secondary and tertiary alcohols according to their structure
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Molecular Ion
The positive ion formed in a mass spectrometer from the whole molecule
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Fragmentation
Splitting of molecules in a mass spectrometer into smaller parts
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Chemical Shift
A measure in ppm from the standard of the energy of a particular absorption type
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Environment
The nature of the surrounding atoms/groups in a molecule
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Wavenumber
A measure of energy absorbed used in IR spectra (cm-1)
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Characteristic Absorption
When the wavenumber range at which a particular bond absorbs radiation
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Other cards in this set

Card 2

Front

Takes in energy from its surroundings

Back

Endothermic

Card 3

Front

The heat content of a system at constant pressure

Back

Preview of the back of card 3

Card 4

Front

The total enthalpy change for a reaction is independent of the route taken

Back

Preview of the back of card 4

Card 5

Front

A catalyst in the same phase as the reactants

Back

Preview of the back of card 5
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