OCR A Level Chemistry
2026 | Comprehensive
Study Guide, Practice
Questions, Answers,
Practicals & Exam Review |
Complete Ethics Study
Guide
Updated 2026 Questions and Answers
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Rationales
Included
, acid A species that is a proton donor.
activation energy The minimum amount of kinetic energy that particles need to have in order to react
when they collide
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 on to 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.
alicyclic hydrocarbon A hydrocarbon with carbon atoms joined together in a ring structure.
aliphatic hydrocarbon A hydrocarbon with carbon atoms joined together in straight or branched chains.
alkali A type of base that dissolves 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, e.g. CH3, C2H5; alkyl groups are often
shown as 'R'.
amount of substance The quantity whose unit of the mole. Chemists use 'amount of substance' as a
means of counting atoms.
anhydrous A substance that contains no water molecules.
anion A negatively charged ion.
atom economy atom economy = molecular mass of the desired product ×100 sum of molecular
masses of all products
2026 | Comprehensive
Study Guide, Practice
Questions, Answers,
Practicals & Exam Review |
Complete Ethics Study
Guide
Updated 2026 Questions and Answers
100% Verified Exam Prep and Comprehensive
Rationales
Included
, acid A species that is a proton donor.
activation energy The minimum amount of kinetic energy that particles need to have in order to react
when they collide
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 on to 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.
alicyclic hydrocarbon A hydrocarbon with carbon atoms joined together in a ring structure.
aliphatic hydrocarbon A hydrocarbon with carbon atoms joined together in straight or branched chains.
alkali A type of base that dissolves 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, e.g. CH3, C2H5; alkyl groups are often
shown as 'R'.
amount of substance The quantity whose unit of the mole. Chemists use 'amount of substance' as a
means of counting atoms.
anhydrous A substance that contains no water molecules.
anion A negatively charged ion.
atom economy atom economy = molecular mass of the desired product ×100 sum of molecular
masses of all products
