Chemistry Edexcel Definitions

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Thermal decomposition
the breaking up of a substance into more than one product by heating it.
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spectator ions
they are ions which take no part in the reaction
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acids
donate hydrogen ions, protons
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bases
accept hydrogen ions
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relative formula mass
is the sum of the relative atomic masses of all the atoms in its formula
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molar mass
the mass of one mole of a chemical in comparison with 1/12 of carbon-12
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enthalpy change
is the overall energy exchanged with the surroundings when a change happens at constant pressure and the final temperature os the same as the starting temperature.
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specific heat capacity
is the energy needed to raise the temperature of 1g of a material by 1K
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Enthalpy change of reaction
is the energy transferred when the molar quantities of reactants as stated in the equation react under standard conditions
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enthalpy change of neutralisation
is the enthalpy change when the amounts of acid and alkali in the equation for the reaction neutralise each other under standard conditions.
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enthalpy change of combustion
the enthalpy change when one mole of a compound is completely burned in excess oxygen under standard conditions.
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enthalpy change of formation
is the enthalpy change when one mole of a compound is formed from its elements under standard conditions.
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enthalpy change of atomisation
the enthalpy change when an element is converted into one mole of free gaseous atoms. e.g 1/2 Cl2 (g) ----> Cl (g)
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Hess' law
says that the enthalpy changein converting reactants to products is the same regardless of the route taken
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Bond (dissociation) enthalpy
the amount of energy required to break one mole of gaseous bonds.
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Isotopes
are atoms of the same element with the same atomic number but different mass numbers/
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realtive isotopic mass
is the mass of one atom of an isotope realtive to the mass of one atom of carbon-12, for which the relative mass is defined as exactly 12
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first ionisation energy
the amount of energy required to remove completely an electron from one mole of gaseous atoms to form one mole of gaseous +1 ions.
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Metallic bonding
is the strong attraction between the lattice of positive metal ions and a 'sea' of delocalised electrons
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electrolysis
is the decomposition of a compound by electricity - the compound is usually decomposed into its constituent elements.
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Electrolyte
is the compound which has been electrolysed.
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Electron Affinity
the change per mole when an electron is added to a gaseous atom to form a gaseous anion. e.g Cl (g) + e- -----> Cl - (g)
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lattice enthalpy
the amount of energy released when one mole of a solid ionic lattice is formed from its ions in the gaseous state. e.g Na+ (g) + Cl- (g) -----> NaCl (s)
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Polarisation
is the distortion of the electron cloud in a molecule or ion by a nearby charge.
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dative covalent bond
is a bond in which two atome share a pair of electrons which is donated by one of the atoms.
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a functional group
is the group of atoms which gives an organic compound its characteristic properties.
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nucleophiles
have a lone pair of electrons and attack positive ions or positive centres in molecules.
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electrophiles
attack negative ions or negative centres in a molecule.
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allotropes
arfe different forms of the same element in the same physical state.
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composite
combines 2 or more materials to create a new material which had the desirable properties of both its constituents.
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electronegativity
is a measure of the ability of an atom to pull a shared pair of electrons in a covakent bond towards itself.
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polarisability
is an indication to the extent of which the electron charge in a molecule can be distorted by a nearby electric charge.
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Miscible
are liquids which can mix with each other
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dynamic equilibrium
the forwards and backwards reactions are equal, at a molecular level there is continuous movement.
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anthropogenic effects
are changes brought about by human activities
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anthropogenic effects
are changes brought about by human activities
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Other cards in this set

Card 2

Front

they are ions which take no part in the reaction

Back

spectator ions

Card 3

Front

donate hydrogen ions, protons

Back

Preview of the back of card 3

Card 4

Front

accept hydrogen ions

Back

Preview of the back of card 4

Card 5

Front

is the sum of the relative atomic masses of all the atoms in its formula

Back

Preview of the back of card 5
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