DEFINITIONS

Question 1

Activation Energy

Answer 1

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

Question 2

Addition polymer

Answer 2

a very long molecular chain, formed by repeated addition reactions of many unsaturated alkene molecules (monomers)

Question 3

Addition Polymerisation

Answer 3

the process in which unsaturated alkene molecule (monomers) add on to a growing polymer chain one at a time to form a very long saturated molecular chain (the addition polymer)

Question 4

Addition reaction

Answer 4

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

Question 5

Alicyclic hydrocarbon

Answer 5

a hydrocarbon with carbon atoms joined together in a ring structure

Question 6

Aliphatic hydrocarbon

Answer 6

a hydrocarbon with carbon atoms joined together in straight or branched chains

Question 7

Alkyl group

Answer 7

an alkane with a hydrogen atom removed, e.g. CH3, C2H5; alkyl groups are often shown as R

Question 8

Anhydrous

Answer 8

a substance containing no water molecules

Question 9

Atom economy

Answer 9

(molecular mass of the desired product/ sum of molecular masses of all products) x100

Question 10

Average bond enthalpy

Answer 10

the average enthalpy change that takes place when breaking by homolytic fission 1 mol of a given type of bond in the molecules of a gaseous species

Question 11

Bond enthalpy

Answer 11

the enthalpy change that takes place when breaking by homolytic fission 1 mole of a given bond in the molecules of a gaseous species

Question 12

Catalyst

Answer 12

A substance that increases the rate of reaction by lowering the activation energy

Question 13

Cis-trans isomerism

Answer 13

a special type of E/Z isomerism in which there is a non-hydrogen group and a hydrogen on each C of a C=C double bond: the cis isomer (Z isomer) has the H atoms on each carbon on the same side; the Trans isomer has the H atoms on opposite sides

Question 14

Compound

Answer 14

a substance formed from two or more chemically bonded elements in a fixed ratio, usually shown by a chemical formula

Question 15

Covalent bond

Answer 15

a bond formed by a shared pair of electrons

Question 16

Cracking

Answer 16

the breaking down of long-chained saturated hydrocarbons to form a mixture of shorter-chained alkanes and alkenes

Question 17

Dative covalent bond

Answer 17

a shared pair of electrons which has been provided by one of the bonding atoms only; also called a coordinate bond

Question 18

Dehydration

Answer 18

an elimination reaction in which water is removed from a saturated molecule to make an unsaturated molecule

Question 19

Delocalised electrons

Answer 19

electrons that are shared between more than two atoms

Question 20

Displacement reaction

Answer 20

a reaction in which a more reactive element displaces a less reactive element from an aqueous solution of the latter’s ions

Question 21

Displayed formula

Answer 21

a formula showing the relative positioning of all the atoms in a molecule and the bonds between them

Question 22

Disproportionation

Answer 22

the oxidation and reduction of the same element in a redox reaction

Question 23

Dynamic equilibrium

Answer 23

the equilibrium that exists in a closed system when the rate of the forward reaction is equal to the rate of the reverse reaction