Topic 4

Question 1

Addition

Answer 1

Joining two or more molecules together to form a larger molecule. Hydration is the addition of a H 2 O molecule. Halogenation involves the addition of a halogen. Hydrogenation is the addition of H. Electrophilic addition describes all the above examples.

Question 2

Alkane

Answer 2

A homologous series of saturated hydrocarbons with the general formula C n H 2n+2.

Question 3

Alkane fuel

Answer 3

Alkanes are good fuels as they are considered to burn cleanly, they undergo combustion in excess oxygen to produce only carbon dioxide and water.

Question 4

Bond breaking

Answer 4

When a bond breaks, energy is absorbed making it an endothermic process.

Question 5

Carbon neutrality (fuels)

Answer 5

A fuel is described as carbon neutral if the production and use of the fuel has no net increase on the amount of carbon dioxide in the atmosphere.

Question 6

Catalyst

Answer 6

A substance which speeds up the rate of a reaction by providing an alternative reaction pathway with a lower activation energy. They are not used up. Enzymes are biological catalysts.

Question 7

Chain isomers

Answer 7

Structural isomers that have carbon backbones of differing lengths. These occur due to the branching in the carbon chain.

Question 8

Combustion of alkanes

Answer 8

The burning of alkanes to release energy. During combustion, the carbon and hydrogen in the fuels are oxidised. Alkanes can undergo complete or incomplete combustion. Water and carbon dioxide are the only products of complete combustion, whereas carbon monoxide and carbon particulates can be produced in incomplete combustion.

Question 9

Cracking

Answer 9

The process of breaking long chain alkanes into smaller, more useful hydrocarbons. Helps to convert low demand hydrocarbons into more highly demanded ones.

Question 10

Crude oil

Answer 10

A finite resource found in rocks. It is the remains of an ancient biomass consisting mainly of plankton that was buried in mud. Most of the compounds in crude oil are hydrocarbons.

Question 11

Cycloalkane

Answer 11

Saturated hydrocarbons that contain a cyclic ring. They only contain single bonds and have a general formula of C n H 2n, which is different to alkanes.

Question 12

Electrophile

Answer 12

Electron pair acceptor in an organic mechanism. Attracted to areas with a lot of electrons/high negative charge.

Question 13

Fractional distillation

Answer 13

A distillation process that utilises a fractionating column (packed with glass beads that provide a surface for the vapour to condense and evaporate again). The mixture of liquids is vaporised and then the gases enter the fractionating column, where they condense at different fractions due to their different boiling points.

Question 14

Free radical substitution

Answer 14

A photochemical reaction between halogens and alkanes to form halogenoalkanes. The reaction requires UV light and involves three stages: initiation, propagation and termination. Initiation creates a radical species. Propagation involves a series of chain reactions where free radicals bond to molecules to form new free radicals. Termination involves the reaction of free radicals with other free radicals to form new molecules.

Question 15

Functional group

Answer 15

A group of atoms responsible for the characteristic reactions of a particular compound.

Question 16

Functional group isomers

Answer 16

Structural isomers that contain different functional groups. This means they belong to different homologous series.

Question 17

Hazard

Answer 17

A property of a chemical that could cause damage to the user.

Question 18

Heterolytic (bond breaking)

Answer 18

The type of bond breaking in which both the electrons from the bond move together to one of the bonding atoms. This leads to the formation of a cation and an anion.

Question 19

Homologous series

Answer 19

Series of organic compounds with the same functional group and general formula. Consecutive members of a series differ by -CH 2.

Question 20

Homolytic (bond breaking)

Answer 20

The type of bond breaking in which the electrons from the bond move separately, one goes to each of the atoms of the bonding pair. This leads to the formation of radicals.

Question 21

Hydrocarbon

Answer 21

A compound consisting of hydrogen and carbon atoms only.

Question 22

Organic molecules

Answer 22

Molecules which contain carbon and hydrogen atoms and often also include additional elements like oxygen and nitrogen.

Question 23

Oxidation

Answer 23

Loss of electron(s), increase in oxidation number.

Question 24

Pollutant

Answer 24

A chemical substance that can damage parts of the environment, like the air, land, or water.

Question 25

Polymerisation

Answer 25

Joining together lots of short chain molecules (monomers) to form a giant long chain molecule (a polymer).

Question 26

Position isomer

Answer 26

Structural isomers that differ in their position of one or more functional groups. The carbon backbone of the molecules are the same.

Question 27

Radical

Answer 27

A species with an unpaired electron. Represented in mechanisms by a single dot, e.g. Cl•.

Question 28

Reduction

Answer 28

Gain in electron(s), decrease in oxidation number.

Question 29

Risk

Answer 29

A possible effect a hazard may have on a user. Control measures are used to restrict the risk.

Question 30

Risk assessment

Answer 30

A process of evaluating all the risks that might be involved when undertaking a specific task or activity.

Question 31

Substitution reaction

Answer 31

A reaction in which one atom/group of atoms is replaced by another atom/group of atoms.

Question 32

Structural isomers

Answer 32

Compounds which have the same molecular formula but a different structural formula. Structural isomers include chain isomers, functional group isomers and position isomers.

Question 33

Synthesis

Answer 33

Combining different elements and compounds to build new molecules.

Question 34

Termination

Answer 34

The final steps in a radical substitution mechanism in which two radicals react together to form a species that only contains paired electrons.

Question 35

Thermal decomposition

Answer 35

A reaction in which a chemical substance is broken down by heating.

Question 36

Toxicity

Answer 36

A measure of how poisonous a chemical substance is.