Chemsitry Unit 1 and 2 definitions

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  • Created by: Endocrine
  • Created on: 29-03-15 23:11
Acid
A species that is a proton donor
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Activation energy
The minimum energy required to start a reaction by the breaking of bonds
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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 reaction
A reaction in which a reactant is added to an unsaturated molecule to make a saturated molecule
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Adsorption
The process that occurs when a gas, liquid or solute is held to the surface of a solid (or ore rarely, a liquid)
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Alicyclic hydrocarbon
A hydrocarbon with carbon atoms joined together in a ring structure
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Aliphatic hydrocarbon
A hydrocarbon with carbon atoms joined together in straight or branched chains
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Alkali
A type of base that dissolves in water, forming hydroxide ion, OH-(aq)
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Alkane
A member of the homologous series with the general formula CnH2n+2
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Alkyl group
An alkane with a hydrogen atom removed, e.g. CH3, C2H5; alkyl groups are often shown as R
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Amount of substance
The quantity whose unit is the mole. Chemists use this as a means of counting atoms.
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Anhydrous
Containing no water molecules
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Anion
A negatively charged ion
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Atom economy
Molecular mass of desired product x 100 Sum of molecular masses of all products
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Atomic orbital
A region within an atom that can hold up to 2 electrons, with opposite spin
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Atomic (proton) number
The number of protons in the nucleus of an atom
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Average bond enthalpy
The average enthalpy change that takes place when breaking by homiletic fission 1 mole of a given type of bond in the molecules of a gaseous substance
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Avogadro constant NA
The number of atoms per mole of the C-12 isotope (6.02 x 10 23 mol -1)
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Base
A species that is a proton acceptor
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Biodegradable material
A substance that is broken down naturally in the environment by living organisms
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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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Bond enthalpy
The enthalpy change that takes place when breaking by homolytic fission1 mole of a given bond in the molecules of a gaseous process
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Carbanion
An organic ion in which a carbon atom has a negative charge
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Carbocation
An organic ion in which a carbon atom has a positive charge
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Catalyst
A substance that increases the rate of a reaction without being used up itself in the process
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Cation
A positively charged ion
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Cis-trans isomerism
A special type of E/Z isomerism in which there is a non-hydrogen group and hydrogen on each C of a C=C double bond: the cis-isomer (Z) has H atoms on each carbon on same side; the trans-isomer (E) has H atoms on each carbon on different sides
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Compound
A substance formed from 2 or more chemically bonded elements in a fixed ratio, usually shown by a chemical formula
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Concentration
The amount of solute (mol) per 1 dm3 (1000cm3) of solution
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Covalent bond
A bond formed by a shared pair of electrons
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Cracking
The breaking down of along-chain saturated hydrocarbons to form a mixture of shorter-chained alkanes and alkenes
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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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Dative covalent (or coordinate) bond
A covalent bond where the shared pair of electrons has only been supplied by one of the bonding atoms
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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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Delocalised electrons
Electrons that are shared between more than 2 atoms
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Displacement reaction
A reaction in which a more reactive element displaces a less reactive one from an aqueous solution of the latter's ions
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Displayed formula
A formula showing the relative positioning of all the atoms in a molecule and the bonds between them
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Disproportionation
The oxidation and reduction of the same element in a redox reaction
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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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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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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 of a covalent bond
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Electron shielding
Repulsion between electrons in different ring shells. It reduces the net attractive force from the positive nucleus on the outer shell electrons.
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Electrophile
An atom (or group of atoms) that is attracted to an electron-rich cents or atom, where it accepts a pair of electrons to form a new covalent bond
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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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Elimination reaction
The removal of a molecule from a saturated molecule to make an unsaturated molecule
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Empirical formula
The simplest whole number ratio 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 that of the reactants, resulting in heat being taken in from the surroundings (delta H +ve)
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Enthalpy (H)
The heat content stored in a chemical system
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(Standard) Enthalpy change of combustion
The enthalpy change that takes place when 1 mole of substance reacts completely with oxygen under standard conditions, all reactants and products being in their standard state
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(Standard) Enthalpy change of formation
The enthalpy change that takes place when 1 mole of substance in its standard state is formed from its constituent elements in their standard state, under standard conditions
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(Standard) 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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Enthalpy cycle
A diagram showing alternative routes between reactants and products that allows the indirect determination of an enthalpy change from other known enthalpy changes using Hess' law
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Enthalpy profile diagram
A diagram for a reaction to compare the enthalpy of the reactants with that of the products
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Esterification
The reaction of an alcohol with a carboxylic acid to produce an ester and water
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Exothermic reaction
A reaction in which the enthalpy of the products is smaller than the enthalpy of the reactants, resulting in heat loss to the surroundings (delta H -ve)
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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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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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Functional group
The part of an organic molecule responsible for chemical reactions
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General formula
The simplest algebraic formula of a member of a homologous series e.g. for alkanes CnH2n+2
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Giant covalent lattice
A 3-dimensional structure of atoms bonded together by strong covalent bonds
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Giant ionic lattice
A 3-dimensional structure of oppositely charged ions, held together by strong ionic bonds
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Giant metallic lattice
A 3-dimensional structure of positive ions and delocalised electrons, bonded together by strong metallic bond
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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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Group
A vertical column in the Periodic Table. Elements in a group have similar chemical properties and their atoms have the number of outer-shell electrons
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Hess' Law
If a reaction can take place by more than 1 route and the initial and final conditions are the same, the total enthalpy change is the same for each route
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Heterogeneous catalysis
A reaction in which the catalyst has different physical state from the reactants (frequently, reactants are gases and catalyst is solid)
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Heterolytic fission
The breaking of a covalent bond with both of the bonded electrons going to 1 of the atoms, forming cation (+ve) and anion (-ve)
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Homogeneous catalysis
A reaction in which the catalyst and reactants are in the same physical state (usually aqueous or gaseous)
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Homologous series
A series of organic compounds with the same organic function group, but with each successive member differing by CH2
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Hydrated
Cystalline, and containing water molecules
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Hydrocarbon
An organic compound containing hydrogen and carbon only
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Hydrogen bond
A strong dipole-dipoleattrsction between an electron-deficient hydrogen atom on one molecule and a lone pair of electrons on a highly electronegative atom of a different molecule
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Hydrolysis
A reaction with water or aqueous hydroxide ions that breaks a chemical
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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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Intermolecular force
An attractive force between neighbouring molecules. Intermolecular forces can be van der Waals forces, permanent dipole-dipole forces or hydrogen bonds
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Ion
A +ely or -vely charged atom or (covalently bonded) group of atoms (a molecular ion)
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Ionic bond
The electrostatic attraction between oppositely charged ions
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Ionic pair
An outer shell pair of electrons not involved in the chemical bonding
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(First) ionisation energy
The energy required to remove 1 electron from each atom in 1 mole of gaseous atoms to from 1 mole of gaseous 1+ ions
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(Second) ionisation energy
The energy required to remove 1 electron from each atom in 1 mole of gaseous atoms to from 1 mole of gaseous 2+ ions
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(Successive) ionisation energy
A measure of the energy required to remove each electron in turn
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Isotopes
Atoms of the same element with different numbers of neutrons and different masses
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le Chatelier's principle
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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Limiting reagent
The substance in a chemical reaction that runs out first
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Lone pair
An outer shell of electrons that is not involved in chemical bonding
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Mass (nucleon) number
The number of particles (protons and neutrons) in the nucleus
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Mechanism
A sequence of steps showing the path taken by electrons in a reaction
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Metallic bond
The electrostatic attraction between +ve metal ions and delocalised electrons
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Molar mass, M
The mass per mole of a substance (expressed in g mol^-1)
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Molar volume
The volume per mole of a gas (expressed in dm^3 mol ^-1). At room temperature, and pressure the molar volume is approximately 24.0 dm^3 mol^-1
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Mole
The amount of any substance containing as many particles as there are in exactly 12g of the C12 isotope
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Molecular formula
The number of atoms of each element in a molecule
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Molecular ion, M+
The positive ion formed in mass spectrometry when a molecule loses an electron
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Molecule
A small group of atoms held together by covalent bonds
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Monomer
A small molecule that combines with many other monomers to form a polymer
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Nomenclature
A system of naming compounds
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Nucleophile
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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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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Oxidation
Loss of electrons or an increase in oxidation number
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Oxidation umber
A measure of the 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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Oxidising agent
A reagent that oxidises (takes electrons from) another species
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Percentage yield
actual amount (mol) of product / theoretical amount (mol) of product x 100
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Period
A horizontal row of elements in the Periodic Table. Elements show trends in properties across a period
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Periodicity
A regular periodic variation of properties for elements with atomic number and position in the periodic table
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Permanent dipole
A small charge difference across a bond resulting from a difference in the 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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Permanent dipole force
A weak attractive force between permanent dipoles in neighbouring polar molecules
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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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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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Polymer
A long molecular chain built up from monomeric units
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Precipitation reaction
The formation of a solid from a solution during a chemical reaction. Precipitates are often formed when 2 aqueous solutions are mixed together
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Principal quantum number
n, a number representing the relative overall energy of each orbit, which increases with distance from the nucleus. The sets of orbitals with the same n value are referred to as electron shells or energy levels.
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Propagation
The 2 repeated steps in radical substitution that builds up the products in a chain reaction
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Radical
A species with an unpaired electron
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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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Rate of reaction
The change in concentration of a reactant or a product in a given time
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Redox reaction
A reaction in which both reduction and oxidation take place
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Reducing agent
A reagent that reduces (adds electrons to) another species
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Reduction
Gain of electrons or a decrease in oxidation number
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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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Relative atomic mass
The weighted mean mass of an atom of an element compared with one-twelfth of the mass of an atom of C-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 C-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 C-12
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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 C-12
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Repeat unit
A specific arrangement of atoms that occurs in the structure over and over again. They are included in brackets, outside of which is the symbol n
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Salt
A chemical compound formed from an acid, when a H+ ion from the acid has been replaced by a metal ion or another +ve ion (e.g. ammonium, NH4+)
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Saturated hydrocarbon
A hydrocarbon with single bonds only
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Shell
A group of atomic orbitals with the same principal quantum number, n. Also known as a main energy level
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Simple molecular lattice
A 3-dimensional structure of molecules, bonded together by weak intermolecular forces
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Skeletal formula
A simplified organic formula, with H atoms removed from alkyl chains leaving just a carbon skeleton and associated functional groups
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Species
Any type of particle that takes part in a chemical reaction
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Specific heat capacity, c
The energy required to raise the temperature of 1g of substance by 1 degree C
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Spectator ions
Ions that are present but do not take part in a chemical reaction
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Standard conditions
A pressure of 100kPa (1 atm), a stated temperature, usually 298 K (25 deg C), and a concentration of 1 mole dm^-3 (for reactions with aqueous solutions)
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Standard solution
A solution of known concentration. Normally used in titrations to determine unknown information about another substance
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Standard state
The physical state of a substance under the standard conditions of 100 kPA and 298 K (25 deg C)
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Stereoisomers
Compounds with the same structural formula but a different arrangement of the atoms in space
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Stoichiometry
The molar relationship between the relative quantities of substances taking part in a reaction
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Stratosphere
The second layer of the Earth's atmosphere, containing the ozone layer, about 10 - 50 km above the Earth's surface
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Structural formula
A formula showing the minimal details for the arrangement of atoms in a molecule
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Structural isomers
Molecules with the same structural formula but different structural arrangements of atoms
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Sub-shell
A group of the same type of atomic orbitals (s,p,d or f) within a shell
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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
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Termination
The step at the end of a radical substitution when 2 radicals combine to form a molecule
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Thermal decomposition
The breaking up of a chemical substance with heat into at least 2 chemical substances
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Troposphere
The lowest layer of the Earth's atmosphere, extending from the Earth's surface unto about 7 km (above the poles) and upto about 20 km (above the tropics)
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Unsaturated hydrocarbon
A hydrocarbon containing carbon-to-carbon multiple bonds
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van der Waals' forces
Very weak attractive forces between induced dipoles in neighbouring molecules
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Volatility
The ease with which a liquid turns into a gas. It increases as boiling point decreases
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Water of crystallisation
Water molecules that form an essential part of the crystalline structure of a compound
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Unit 1 (Atoms, bonds and groups) Module I: Atoms and reactions
Unit 1 Module I: Atoms and reactions
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Unit 1 (Atoms, bonds and groups) Module 2: Electrons, bonding and structure
Unit 1 Module 2: Electrons, bonding and structure
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Unit 1 (Atoms, bonds and groups) Module 3: The Periodic Table
Unit 1 Module 3: The Periodic Table
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Unit 2 (Chains, energy and resources) Module 1: Basic concepts and hydrocarbons
Unit 2 (Chains, energy and resources) Module 1: Basic concepts and hydrocarbons
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Unit 2 (Chains, energy and resources) Module 2: Alcohols, halogenoalkanes and analysis
Unit 2 (Chains, energy and resources) Module 2: Alcohols, halogenoalkanes and analysis
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Unit 2 (Chains, energy and resources) Module 3: Energy
Unit 2 (Chains, energy and resources) Module 3: Energy
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Unit 2 (Chains, energy and resources) Module 4: Resources
Unit 2 (Chains, energy and resources) Module 4: Resources
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Other cards in this set

Card 2

Front

The minimum energy required to start a reaction by the breaking of bonds

Back

Activation energy

Card 3

Front

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)

Back

Preview of the back of card 3

Card 4

Front

A reaction in which a reactant is added to an unsaturated molecule to make a saturated molecule

Back

Preview of the back of card 4

Card 5

Front

The process that occurs when a gas, liquid or solute is held to the surface of a solid (or ore rarely, a liquid)

Back

Preview of the back of card 5
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