Key Terms

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Activation Energy
The minimum energy required to start a reaction by the breaking of bonds.
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Alkanes
The homologous series with the general formula: CnH2n+2
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Amount of Substance
The quantity whose unit of the mole. Chemists use "amount of substance" as a means of counting atoms.
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Anion
A negatively charged ion.
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Anhydrous
A substance that contains no water molecules.
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Atomic Orbital
A region within an atom that can hold up to two electrons, with opposite spins.
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Avogadro Constant
The number of atoms per mole of the carbon-12 isotope (6.02 X 10^23 mol^-1)
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Bond Enthalpy
The enthalpy change that takes place when breaking a given bond in the molecules of a gaserous species.
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Catalyst
A substance that increases the rate of a chemcial reaction without being used up in the process.
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Compound
A substance formed from two or more chemically bonded elements in a fixed ratio, usually shown by a chemical formula.
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Covalent Bond
A bond formed by a shared pair of electrons.
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Dative Covalent
A shared pair of electrons which have been proided by one of the bonding atoms only: also called a coordinate bond.
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Electron Configuration
The arrangement of electrons in an atom.
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Electronegativity
A measure of the attraction of a bonded atom for the pair of electrons in a covalent bond.
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Electron Shielding
The repulsion between electrons in different inner shells. Shielding reduces the net attractive force from the positive nucleus on the outer-shell electrons.
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Emprical Formula
The simplest whole-number ratio of atoms of each element present in a compound.
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Endothermic Reaction
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.
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Enthalpy
The heat content that is stored inaa chemcial system.
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Enthalpy change of combustion
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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Enthalpy change of formation
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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Enthalpy change of reaction
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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Exothermic Reaction
A reaction in which the enthalpy of the products is smaller than enthalpy of the reactants, resulting in heat loss of the surroundings.
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Hess' Law
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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Heterogenous 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 physicla state, which is most frequently the aqueous or gaseous state.
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Intermolecular Force
An attractive force bewteen neighbouring molecules. Intermolecular forces can be London Forces (induced dipole-diople forces), permanent dipole-dipole forces or hydogen bonds.
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Lone Pair
An outer shell pair of electrons that is not involved in chemcial bonding.
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Oxidation
Loss of electrons or an increase in oxidation number.
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Oxidation Number
A measure of the number of electrons that an atom uses to bond with atoms of another element. Oxidation numbers are derived from a set of rules.
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Permanent Dipole
A small charge difference across a bond resulting from a difference in electronegativities of the bonded atoms.
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Permanent dipole-dipole force
An attractive force between permanent dipoles in neighbouring polar molecules.
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Polar covalent bond
A bond with a permanent dipole.
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Polar Molecule
A molecule with an overall dipole, taking into account any dipoles across bonds.
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Rate of Reaction
The change in concentration of reactant or a prouct in a given time.
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Relative Atomic Mass
The weighted mean mass of an atom of an atom of an element compared with one-twelfth of the mass of an atom of carbon-12.
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Relative Formula Mass
The weighted mean mass of a formula unit compared with one-twelfth of the mass of an atom of carbon-12.
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Relative Isotopic Mass
The mass of an atom of an isotope compared with one-twelfth of the mass of an atom of carbon.
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Relative Molecular Mass
The weighted mean mass of a molecule compared with one-twelfth of the mass of an atom of carbon-12.
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Specific Heat Capactity
The energy required to raise the temperature of 1g of a substance by 1 degrees.
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Standard Conditions
A pressure of 100 kPa, a temperature usually 298 K (25 degrees) and concentration of 1 mol dm ^-3.
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Standard Solutions
A solution of known concentration. Standard soultions are normally used in titrations to determine unknown information about another substance.
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London Forces
Very weak attractive forces between induced dipoles in neighbouring molecules.
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Other cards in this set

Card 2

Front

The homologous series with the general formula: CnH2n+2

Back

Alkanes

Card 3

Front

The quantity whose unit of the mole. Chemists use "amount of substance" as a means of counting atoms.

Back

Preview of the back of card 3

Card 4

Front

A negatively charged ion.

Back

Preview of the back of card 4

Card 5

Front

A substance that contains no water molecules.

Back

Preview of the back of card 5
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