Definitions Flashcards
Acid
A species that is a proton donor
Activation Energy
The minimum energy required to start a reaction by the breaking of bonds
Addition Polymer
A very long molecular chain formed by repeated addition reactions of many unsaturated alkene molecules (monomers)
Addition Polymerisation
The process in which unsaturated alkene molecules (monomers) add onto a growing polymer chain one at a time to form a very long saturated molecular chain (the addition polymer).
Addition Reaction
A reaction in which a reactant is added to an unsaturated molecule to make a saturated molecule.
Adsorption
The process that occurs when a gas, liquid or solute is held to the surface of a solid or, more rarely, a liquid.
1st Ionisation Energy
The energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous ions with a single positive (1+) charge
2nd Ionisation Energy
The energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous ions with a doublepositive (2+) charge
Alicyclic hydrocarbon
A hydrocarbon with carbon atoms joined together in a ring structure
Aliphatic Hydrocarbon
A hydrocarbon with carbon atoms joined together in a straight or branched chains
Alkali
A type of base that dissoves in water forming hydroxide ions OH- (aq) ions
Alkanes
The homologous series with the general formula CnH2n+2
Alkyl group
An alkane with a hydrogen atom removed eg. CH3, C2H5. Alkyl groups are often shown as ‘R’
Amount of Substance
Quantity whose unit is the mole. Chemists use the “amount of substance” as a means of counting atoms
Anhydrous
A substance that contains no water molecules
Anion
Negatively charged ion
Atom Economy
Atomic Orbital
A region of space in which up to two electrons can be found with opposite spins
Atomic (proton) number
The number of protons in the nucleus of the atom. The same as the number of electrons surrounding a neutrally charged atom of the element.
Average bond enthalpy
The average enthalpy change that takes place when breaking by homolytic fission 1 mole of a given type of bond in the molecules of a gaseous species
Avogadro Constant NA
The number of atoms per mole of the carbon-12 isotope (6.02 x10^23)
Base
A species that is proton acceptor
Biodegradable material
A substance that is broken down naturally in the environment by living organisms
Bolzmann Distribution
The distribution of energies of molecules at a particular temperature, usually shown as a graph.
Bond enthalpy
The enthalpy change that takes place when breaking by homolytic fission 1 mole of a given bond in the molecule of a gaseous species
Carbanion
An organic ion in which a carbon atom has a negative charge
Carbocation
An organic ion in which a carbon atom has a positive charge (Br2 mechanism)
Catalyst
A substance that increases the rate of a chemical reaction without being used up in the process.
Cation
A positively charged ion
Cis-trans isomerism
A special type of E/Z isomerism in which there is a non-hydrogen group and a hydrogen atom on each C of a C=C double bond. Cis –> H atoms are on the same side (like the Z) Trans –> H atoms are on different sides (like the E)
Compound
A substance formed from two or more chemically bonded elements in a fixed ratio, usually shown by a chemical formula
Concentration
The amount of solute, in mole, per 1 dm^3 (1000cm^3) of solution
Covalent Bond
A bond formed by a shared pair of electrons
Cracking
The breaking down of long-chained saturated hydrocarbons to form a mixture of shorter-chained alkanes and alkenes.
Curly Arrow
A symbol used in reaction mechanisms to show the movement of a pair of electrons in the breaking or formation of a covalent bond
Dative Covalent Bond / Co-ordinate bond
A shared pair of electrons which has been provided by one of the bonding atoms only.
Dehydration
An elimination reaction in which water is removed from a saturated molecule to make an unsaturated molecule
Delocalised electrons
Electrons that are shared between more than two atoms esp. found in metallic bonds
Displacement reactions
A reaction in which a more reactive element displaces a less reactive element from an aqueous solution of the latter’s ions
Displayed formula
A formula showing the relative positioning of all the atoms in a molecule and the bonds between them
Disproportionation
A special type of redox in which the same species is simultaneously oxidised and reduced at the same time.
Dynamic equilibrium
The equilibrium that exists in a closed system when the rate of the forward reaction is equal to the rate of the backwards reaction
E/Z isomerism
A type of stereoisomerism in which different groups attached to each carbon of the C=C double bond may be arranged differently in space because of restricted rotation of the C=C double bond.
Electron configuration
The arrangement of electrons in an atom
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
Electronegativity
The measure of the attraction of a bonded atoms for the pair of electrons in a covalent bond
Electrophile
An atom (or group of atoms) that is attracted to an electron-rich centre where it accepts a pair of electrons to form a new covalent bond
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
Elimination reaction
The removal of a molecule from a saturated molecule to make an unsaturated molecule
Empirical formula
The simplest whole number ratio of atoms of each element present in a compound
Endothermic Enthalpy Profile Diagram
Endothermic reaction
A reaction in which the enthalpy of products is greater than the enthalpy of the reactants, resulting in heat being taken in from the surrounding (ΔH = +ve)
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
Enthalpy Formula
-q/mol
Enthalpy profile diagram
A diagram for a reaction to compare the enthalpy of the reactants with the enthalpy of the products
Enthalpy, H
The heat content that is stored in a chemical system
Esterification
The reaction of an alcohol with a carboxylic acid to produce an ester and water
Ethene and Bromine Mechanism
Exothermic reaction
A reaction in which the enthalpy of the products is smaller than the enthalpy of the reactants, resulting in a heat loss to the surroundings (ΔH = -ve)
Exothermic Enthalpy Profile Diagram
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 (evaporation and condensation) by use of a fractionating column
Fragmentation
The process in mass spectrometry that causes a positive ion to split into pieces, one of which is a positive fragment ion