As Level Chemistry Key Words Edexcel

Front 1

Accuracy

Back 1

A measure of how close values are to the accepted or correct value

Front 2

Activation energy, Ea

Back 2

The minimum energy that colliding particles must possess for a reaction to occur

Front 3

Actual yield

Back 3

The actual mass obtained in a reaction

Front 4

Addition reaction

Back 4

A reaction in which two molecules combine to form one molecule

Front 5

Aldehyde

Back 5

A homologous series of organic compounds formed by the partial oxidation of primary alcohols

Front 6

Atom economy

Back 6

The molar mass of the desired product divided by the sum of the molar masses of all the products, expressed as a percentage

Front 7

Atomic number (Z)

Back 7

The number of protons in the nucleus of an atom of an element

Front 8

Avogadro constant

Back 8

The number of atoms of 12C in exactly 12g of 12C

Front 9

Avogadro's law

Back 9

States that equal volumes of gases under the same conditions of temperature and pressure contain the same numbers of molecules

Front 10

Base peak

Back 10

Indicates the peak with the greatest abundance on a mass spectrum for an element

Front 11

Basic oxides

Back 11

Oxides of metals that react with water to form metal hydroxides, and with acids to form salts and water

Front 12

Bioalcohols

Back 12

Fuels made from plant matter, often using enzymes or bacteria

Front 13

Biodegradable

Back 13

A polymer that can be broken down by microbes

Front 14

Biodiesel

Back 14

A fuel made from vegetable oils obtained from plants

Front 15

Biofuels

Back 15

Fuels obtained from living matter that has died recently

Front 16

Blocks

Back 16

The four divisions of the Periodic Table

Front 17

Bond enthalpy

Back 17

The enthalpy change when one mole of a bond in the gaseous state is broken

Front 18

Bond length

Back 18

The distance between nuclei of the two atoms that are covalently bonded together

Front 19

Carbocation

Back 19

A positive ion in which the charge is shown on a carbon atom

Front 20

Carboxylic acids

Back 20

A homologous series of organic compounds formed by the complete oxidation of primary alcohols

Front 21

Catalyst

Back 21

A substance that increases the rate of a chemical reaction but is chemically unchanged at the end of the reaction

Front 22

Coefficient

Back 22

The numbers written in front of species when balancing an equation

Front 23

Complete combustion

Back 23

Occurs when all the atoms in a fuel are fully oxidised

Front 24

Concordant titres

Back 24

Titres whose values are close together (within 0.20cm3 of each other)

Front 25

Cracking

Back 25

The breakdown of molecules into shorter ones by heating with a catalyst

Front 26

Curly arrows

Back 26

Arrows that represent the movement of electron pairs in a mechanism

Front 27

Dehydration

Back 27

A reaction that results in the removal of the hydroxyl group in an alcohol molecule, together with a hydrogen atom from an adjacent carbon atom, forming a C=C double bond

Front 28

Delocalised electrons

Back 28

Electrons that are not associated with any single atom or any single covalent bond

Front 29

Diol

Back 29

A compound containing two OH (alcohol) groups

Front 30

Dipole

Back 30

A molecule with two charges of equal magnitude but opposite signs separated by a small distance

Front 31

Discrete (simple) molecule

Back 31

An electrically neutral group of two or more atoms held together by chemical bonds

Front 32

Displacement reaction

Back 32

A reaction in which one element replaces another element in a compound

Front 33

Displayed (full structural) formula

Back 33

Shows each bonding pair as a line drawn between the two atoms involved

Front 34

Displayed formula

Back 34

Shows every atom and every bond

Front 35

Disproportionation

Back 35

The simultaneous oxidation and reduction of an element in a single reaction

Front 36

Distillation with addition

Back 36

Heating a reaction mixture, but adding another liquid and distilling off the product as it forms

Front 37

Electronegativity

Back 37

The ability of an atom to attract a bonding pair of electrons in a covalent bond

Front 38

Electronic configuration

Back 38

Shows the number of electrons in each sub-level in each energy level of the atom

Front 39

Electron-releasing

Back 39

A group that pushes electrons towards the atom it is joined to

Front 40

Electrophile

Back 40

A species that is attracted to a region of high electron density

Front 41

Electrophilic addition

Back 41

A reaction in which two molecules form one molecule and the attacking molecule is an electrophile

Front 42

Elimination

Back 42

A reaction in which a molecule loses atoms attached to adjacent carbon atoms, forming a C=C double bond

Front 43

Empirical formula

Back 43

The numbers of each atom in a compound in the simplest whole-number ratio

Front 44

End point

Back 44

The point at which the indicator in a titration just changes colour. Ideally, the end point should coincide with the equivalence point

Front 45

Endothermic

Back 45

Heat energy is transferred from the surroundings to the system

Front 46

Equivalence point

Back 46

The point at which there are exactly the right amounts of substances to complete the reaction

Front 47

Error

Back 47

The difference between an experimental value and the accepted or correct value

Front 48

Ethanolic

Back 48

A solution in which ethanol is the solvent

Front 49

Exothermic

Back 49

Heat energy is transferred from the system to the surroundings

Front 50

Feedstock

Back 50

Converting polymer waste into chemicals that can be used to make new polymers

Front 51

First ionisation energy

Back 51

The energy required to remove an electron from each atom in one mole of atoms of an element in the gaseous state

Front 52

Fractional distillation

Back 52

The process used to separate a liquid mixture into fractions by boiling and condensing

Front 53

Fragmentation

Back 53

Occurs when the molecular ion breaks into smaller pieces

Front 54

Functional group

Back 54

An atom or group of atoms in a molecule that is responsible for its chemical reactions

Front 55

Geometric isomers

Back 55

Compounds containing a C=C bond with atoms of groups attached at different positions

Front 56

Groups

Back 56

Vertical columns in the Periodic Table

Front 57

Halogenation

Back 57

The addition of a halogen

Front 58

Heating under reflux

Back 58

Involves heating a reaction mixture with a condenser fitted vertically

Front 59

Hess's Law

Back 59

States that the enthalpy change of a reaction is independent of the path taken in converting reactants into products, provided the initial and final conditions are the same in each case

Front 60

Heterogeneous catalyst

Back 60

A catalyst that is in a different phase to that of the reactants

Front 61

Heterolytic fission

Back 61

The breaking of a covalent bond so that both bonding electrons are taken by one atom

Front 62

Homogeneous system

Back 62

A system where at least two different phases are present

Front 63

Homologous series

Back 63

A family of compounds with the same functional group, which differ in formula by CH2 from the next member

Front 64

Homolytic fission

Back 64

The breaking of a covalent bond where each of the bonding electrons leaves with one species, forming a radical

Front 65

Hund's rule

Back 65

States that electrons will occupy the orbitals singly before pairing takes place

Front 66

Hydrates

Back 66

Compounds containing water of crystallisation represented by formulae such as CuSO4.5H2O

Front 67

Hydration

Back 67

The addition of water (or steam)

Front 68

Hydrocarbon

Back 68

A compound that contains only carbon hydrogen atoms

Front 69

Hydrogen bond

Back 69

An intermolecular interaction (in which there is some evidence of bond formation) between a hydrogen atom of a molecule (or molecular fragment) bonded to an atom which is more electronegative than hydrogen and another atom in the same or a different molecule

Front 70

Hydrogenation

Back 70

The addition of hydrogen

Front 71

Hydrolysis

Back 71

A reaction in which water or hydroxide ions replace an atom in a molecule with an -OH group

Front 72

Incinerator

Back 72

Converts polymer waste into energy

Front 73

Incomplete combustion

Back 73

Occurs when some of the atoms in a fuel are not fully oxidised

Front 74

Infrared radiation

Back 74

The part of the electromagnetic spectrum with frequencies below that of red light

Front 75

Initiation

Back 75

The step that involves the formation of radicals, usually as a result of bond breaking caused by ultraviolet radiation in homolytic fission

Front 76

Intensity

Back 76

The amount of infrared radiation absorbed

Front 77

Isotopes

Back 77

Atoms of the same element with different masses

Front 78

Ketones

Back 78

A homologous series of organic compounds formed by oxidation of secondary alcohols

Front 79

Locant

Back 79

A number used to indicate which carbon atom in the chain an atom or group is attached to

Front 80

Mass concentration

Back 80

The mass (in g) of the solute divided by the volume of the solution

Front 81

Mass number

Back 81

The sum of the number of protons and the number of neutrons in the nucleus of that atom

Front 82

Mean bond enthalpy

Back 82

The enthalpy change when one mole of a bond, averaged out over many different molecules, is broken

Front 83

Measurement uncertainty

Back 83

The potential error involved when using a piece of apparatus to make a measurement

Front 84

Mechanism

Back 84

The sequence of steps in an overall reaction. Each step shows what happens to the electrons involved in bond breaking or bond formation

Front 85

Meniscus

Back 85

The curving of the upper surface in a liquid in a container. The lowest (horizontal) part of the meniscus should be read

Front 86

Metallic bonding

Back 86

The electrostatic force of attraction between the nuclei of metal cations and delicalised electrons

Front 87

Molar concentration

Back 87

The amount (in mol) of the solute divided by the volume of the solution

Front 88

Molar mass

Back 88

The mass per mole of a substance. It has the symbol M and the units gmol-1

Front 89

Molar volume

Back 89

The volume occupied by 1mol of any gas

Front 90

Mole

Back 90

The amount of substance that contains the same number of particles as the number of carbon atoms in exactly 12g of the carbon-12 isotope

Front 91

Molecular formula

Back 91

The actual number of atoms of each element in a molecule

Front 92

Molecular ion peak

Back 92

The peak with the highest m/z ratio in the mass spectrum, the M peak

Front 93

Monomers

Back 93

The small molecules that combine together to form a polymer

Front 94

Multiple bond

Back 94

Two or more covalent bonds between two atoms

Front 95

Nitrile

Back 95

Organic compound containing C-CN group

Front 96

Non-renewable

Back 96

Energy sources that are not being replenished, except over geological timescales

Front 97

Nucleophile

Back 97

A species that donates a lone pair of electrons to form a covalent bond with an electron-deficient atom

Front 98

Nucleophilic substitution

Back 98

A reaction in which an attacking nucleophile replaces an existing atom or group in a molecule

Front 99

Orbital

Back 99

A region within an atom that can hold up to two electrons with opposite spins

Front 100

Oxidation

Back 100

The loss of electrons

Front 101

Oxidation number

Back 101

The charge that an ion has or the charge that it would have if the species were fully ionic

Front 102

Oxidised

Back 102

An element is oxidised when its oxidation number increases

Front 103

Oxidising agent

Back 103

A species (atom, molecule or ion) that oxidises another species by removing one or more electrons. When an oxidising agent reacts it gains electrons and is, therefore, reduced

Front 104

The Pauli Exclusion Principle

Back 104

States that two electrons cannot occupy the same orbital unless they have opposite spins. Electron spin is usually shown by the use of upward and downward arrows

Front 105

Percentage uncertainty

Back 105

The actual measurement uncertainty multiplied by 100 and divided by the value recorded

Front 106

Percentage yield

Back 106

100 x the actual yield divided by the theoretical yield

Front 107

Periodicity

Back 107

A regularly repeating pattern of atomic, physical and chemical properties with increasing atomic number

Front 108

Periods

Back 108

The horizontal rows in the Periodic Table

Front 109

Pi bonds

Back 109

Covalent bonds formed when electron orbitals overlap sideways

Front 110

Polar covalent bond

Back 110

A type of covalent bond between two atoms where the bonding electrons are unequally distributed. Because of this, one atom carries a slight negative charge and the other a slight positive charge

Front 111

Precipitation reaction

Back 111

A reaction in which an insoluble solid is formed from the reaction between two soluble reactants

Front 112

Precision

Back 112

A measure of how close values are to each other

Front 113

Prefix

Back 113

A set of letters written at the beginning of a name

Front 114

Primary amines

Back 114

Compounds containing the C-NH2 group

Front 115

Primary standards

Back 115

Substances used to make a standard solution by weighing

Front 116

Propagation

Back 116

Two steps in homolytic fission that, when repeated many times, convert the starting materials into the products of a reaction

Front 117

Quantum shell

Back 117

The energy level of an electron

Front 118

Radical

Back 118

A species that contains an unpaired electron

Front 119

Random errors

Back 119

Errors caused by unpredictable variations in conditions

Front 120

Recycling

Back 120

Involves converting polymer waste into other materials

Front 121

Redox reaction

Back 121

A reaction that involves both reduction and oxidation

Front 122

Reduced

Back 122

An element is reduced when its oxidation number decreases

Front 123

Reducing agent

Back 123

A species that reduced another species by adding one or more electrons. When a reducing agent reacts it loses electrons and is, therefore, oxidised

Front 124

Reduction

Back 124

The gain of electrons

Front 125

Reforming

Back 125

The conversion of straight-chain hydrocarbons into branched-chain and cyclic hydrocarbons

Front 126

Relative atomic mass (Ar)

Back 126

The weighted mean (average) mass of an atom of an element compared to 1/12 the mass of an atom of carbon-12

Front 127

Relative isotopic mass

Back 127

The mass of an individual atom of an isotope relative to 1/12 the mass of an atom of carbon-12

Front 128

Renewable

Back 128

Energy sources that can be continuously replaced

Front 129

Repeat unit

Back 129

The set of atoms that are joined together in large numbers to produce the polymer structure of a polymer

Front 130

Restricted rotation

Back 130

The fixed position of atoms or groups attached to a C=C double bond

Front 131

Saturated

Back 131

A compound containing only single bonds

Front 132

Second ionisation energy

Back 132

The energy required to remove an electron from each singly charged positive ion in one mole of positive ions of an element in the gaseous state

Front 133

Sigma bonds

Back 133

Covalent bonds formed when electron orbitals overlap axially (end on)

Front 134

Simple distillation

Back 134

Used to separate liquids with very different boiling temperatures

Front 135

Skeletal formula

Back 135

All the bonds between carbon atoms

Front 136

Solute

Back 136

A substance that is dissolved

Front 137

Solution

Back 137

A solute dissolved in a solution

Front 138

Solvent

Back 138

A substance that dissolves a solute

Front 139

Solvent extraction

Back 139

Used to separate a liquid from a mixture by causing it to move from the mixture to the solvent

Front 140

Spectator ions

Back 140

The ions in an ionic compound that do not take part in a reaction

Front 141

Standard enthalpy change of combustion

Back 141

The enthalpy change measured at 100kPa and a stated temperature, usually 298K, when one mole of a substance is completely burned in oxygen

Front 142

Standard enthalpy change of formation

Back 142

The enthalpy change measured at 100kPa and a stated temperature, usually 298K, when one mole of a substance is formed from its elements in their standard states

Front 143

Standard enthalpy change of neutralisation

Back 143

The enthalpy change measured at 100kPa and a stated temperature, usually 298K, when one mole of water is produced by the neutralisation of an acid with an alkali

Front 144

Standard enthalpy change of reaction

Back 144

The enthalpy change measured at 100kPa and a stated temperature, usually 298K, when the number of moles of substances in the equation as written react

Front 145

Standard solution

Back 145

A solution whose concentration is accurately known

Front 146

Stereoisomers

Back 146

Compounds with the same structural formula (and the same molecular formula), but with atoms or groups arranged differently in three dimensions

Front 147

Stretching

Back 147

Occurs when a bond absorbs infrared radiation and uses it to alter the length of the bond

Front 148

Structural formula

Back 148

Shows (unambiguously) how the atoms are joined together

Front 149

Structural isomers

Back 149

Compounds witht he same molecular formula but with different structural formulae

Front 150

Substitution reaction

Back 150

One in which an atom or group is replaced by another atom or group

Front 151

Suffix

Back 151

A set of letters written at the end of a name

Front 152

Systematic errors

Back 152

Errors that are constant or predictable, usually because of the apparatus used

Front 153

Termination

Back 153

The step in homolytic fission involving a molecule from two radicals

Front 154

Thermal stability

Back 154

A measure of the extent to which a compound decomposes when heated

Front 155

Titre

Back 155

The volume added from the burette during a titration

Front 156

Transmittance

Back 156

Value in an infrared spectrum represents the amount of radiation absorbed at a particular wavenumber

Front 157

Unsaturated

Back 157

A compound containing one or more multiple bonds

Front 158

Wavenumber

Back 158

The frequency of infrared radiation absorbed by a particular bond in a molecule