Definitions

Question 1

Atomic Number

Answer 1

Number of protons in the nucleus of an atom

Question 2

Mass Number

Answer 2

Total number of protons and neutrons

Question 3

Isotopes

Answer 3

Atoms with the same number of protons but different numbers of neutrons

Question 4

Relative atomic mass

Answer 4

weighted average mass of an atom compared to 1/12th of the mass of a C-12 atom

Question 5

Relative isotopic mass

Answer 5

weighted average mass of an atom of a particular isotope compared to 1/12th of the mass of a C-12 atom

Question 6

Relative molecular mass

Answer 6

weighted average mass of a molecule compared to 1/12th of the mass of a C-12 atom

Question 7

First Ionisation Energy

Answer 7

energy required to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions

Question 8

Second Ionisation Energy

Answer 8

Energy required to remove one electron from each ion in one mole of gaseous 1+ ions to form one mole of gaseous 2+ ions

Question 9

Avogadro’s number

Answer 9

the number of atoms in 12 g of C-12

Question 10

Empirical Formula

Answer 10

the simplest whole number ratio of the atoms of each element in a compound

Question 11

Molecular formula

Answer 11

the number of atoms of each element in one molecule of a substance

Question 12

ionic bond

Answer 12

an electrostatic force of attraction between oppositely charged ions

Question 13

covalent bond

Answer 13

a shared pair of electron held in place by the attraction to the nuclei either side

Question 14

Dative covalent bond

Answer 14

a shared pair of electrons where both electrons come from the same atom

Question 15

Metallic bond

Answer 15

an electrostatic force of attraction between a cation and a sea of declocalised electrons

Question 16

Electronegativity

Answer 16

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

Question 17

Polar bond

Answer 17

the unequal sharing of electrons in a covalent bond causing a partial positive and partial negative charge on the atoms either side

Question 18

s-block element

Answer 18

element with its highest energy electron in an s sub-shell

Question 19

p-block element

Answer 19

element with its highest energy electron in a p sub-shell

Question 20

d-block element

Answer 20

element with its highest energy electron in a d sub-shell

Question 21

homologous series

Answer 21

series of compounds with the same functional group each differing by a CH2 group from each other

Question 22

Isomers

Answer 22

molecules with the same molecular formula but a different arrangement of atoms

Question 23

Structural Isomers

Answer 23

Same molecular formula but different structural formula

Question 24

Chain isomers

Answer 24

same molecular formula but a different arrangement of C atoms in the C skeleton

Question 25

Positional isomers

Answer 25

same molecular formula but the functional group is in a different position

Question 26

Functional group isomers

Answer 26

Same molecular formula but a different functional group

Question 27

Functional group

Answer 27

an atom or group of atoms which give the specific physical and chemical properties to the molecule

Question 28

Enthalpy Change

Answer 28

change in heat energy under constant pressure

Question 29

Standard conditions

Answer 29

100 kPa and 298 K (25 oC)

Question 30

Exothermic reaction

Answer 30

a reaction that gives out energy to the surroundings

Question 31

Endothermic reaction

Answer 31

a reaction that takes in energy from the surroundings

Question 32

Standard enthalpy of formation

Answer 32

enthalpy change when one mole of a compound is formed from its constituent elements under standard conditions. All substances are in their standard states.

Question 33

Standard enthalpy of combustion

Answer 33

enthalpy change when one mole of a substance undergoes complete combustion in excess oxygen. All substances are in their standard states.

Question 34

Hess's Law

Answer 34

enthalpy change of a reaction is independent of the route taken and depends only on the initial reactants and final products

Question 35

Mean bond enthalpy

Answer 35

Enthalpy change when 1 mole of gaseous covalent bonds are broken averaged over a series of different compounds.

Question 36

Activation energy

Answer 36

minimum energy required for a reaction to be successful. (It is the energy required to break bonds)

Question 37

Rate of reaction

Answer 37

change in concentration of a reactant or product per second

Question 38

catalyst

Answer 38

substance that speeds up the rate of a reaction without being used up

Question 39

How catalysts work

Answer 39

by providing an alternative reaction pathway with lower activation energy

Question 40

Dynamic Equilibrium

Answer 40

reaction in which both the forward and reverse reaction happen at the same rate so the concentration of reactants and products remain constant

Question 41

Le Chatelier's Principle

Answer 41

if a change of conditions is imposed on a system at equilibrium, the system will act to oppose the change

Question 42

Oxidation

Answer 42

Loss of electrons. (Can also be gain of O, loss of H or increase in ox number)

Question 43

Reduction

Answer 43

Gain of electrons. (Can also be loss of O, gain of H or decrease in ox number)

Question 44

Oxidising agent

Answer 44

electron acceptor (the substance being reduced)

Question 45

Reducing agent

Answer 45

electron donor (the substance being oxidised)

Question 46

Stereoisomers

Answer 46

same molecular formula but a different arrangement of atoms in 3D space

Question 47

Redox reaction

Answer 47

reaction in which both oxidation and reduction occur

Question 48

Geometrical isomers

Answer 48

same molecular formula but a different spatial arrangement of atoms around a double bond

Question 49

Addition reaction

Answer 49

Reaction in which two or more molecules combine to form a single larger molecule

Question 50

Substitution reaction

Answer 50

reaction where one functional group is replace by another

Question 51

Elimination reaction

Answer 51

loss of a small molecule from a larger molecule to form an unsaturated compound

Question 52

Electrophile

Answer 52

electron pair acceptor

Question 53

Nucleophile

Answer 53

electron pair donor

Question 54

Free Radical

Answer 54

species with an unpaired electron

Question 55

Homolytic Fission

Answer 55

Breaking of a covalent bond so one electron goes to each atom forming free radicals

Question 56

Heterolytic Fission

Answer 56

Breaking of a covalent bond so both electrons go to one atom forming a cation and anion

Question 57

Hydration

Answer 57

addition of water to a species

Question 58

Hydrolysis

Answer 58

Use of water to break bonds

Question 59

Unsaturated

Answer 59

Organic compound containing a C=C double bond

Question 60

Saturated

Answer 60

Organic compound with only C-C single bonds

Question 61

Addition polymerisation

Answer 61

Combination of a large number of monomers to form a single chain

Question 62

Biofuel

Answer 62

Fuel produced from renewable biological resources.