Key Definitions

Question 1

ISOTOPES

Answer 1

Atoms of the same element with different numbers of neutrons and different masses

Question 2

ATOMIC NUMBER

Answer 2

Number of protons and electrons in an atom

Question 3

MASS NUMBER

Answer 3

Total number of protons and neutrons in the nucleus of an atom

Question 4

IONS

Answer 4

Particles of an element with different numbers of electrons and protons that also have a charge

Question 5

RELATIVE ATOMIC MASS

Answer 5

The average mass of an atom compared to 1/12 of the carbon 12 atom

Question 6

RELATIVE ISOTOPIC MASS

Answer 6

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

Question 7

MOLE

Answer 7

A mole is the amount of a substance that contains as many particles as there are atoms in 12g of carbon

Question 8

MOLAR MASS

Answer 8

The mass of 1 mole is equal to the relative molecular mass and is written in g/mol

Question 9

AVOGADRO’S CONSTANT

Answer 9

The total number of atoms in 1 mole. There are 6.02x10^23

Question 10

MOLECULAR FORMULA

Answer 10

The actual number of atoms of each element in a compound

Question 11

EMPIRICAL FORMULA

Answer 11

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

Question 12

RELATIVE MOLECULAR/FORMULA MASS

Answer 12

The total atomic masses of each element added together. Relative molecular is used for simple molecules. Relative formula is used for giant structures like ionic

Question 13

STOICHIOMETRY

Answer 13

The ratio of an amount in moles in an equation

Question 14

PERCENTAGE YIELD

Answer 14

The amount of substance that is made compared to the theoretical amount of substance.

Question 15

LIMITING REAGENT

Answer 15

If a reactant is not in excess, it will be used up first, therefore it is the limiting reagent, this is normally the one with bigger amount of moles.

Question 16

ATOM ECONOMY

Answer 16

How well an atom is used up, a perfect atom economy is 100%

Question 17

STRONG ACID

Answer 17

When dissolved in water it releases all of its H+ protons and fully dissociates

Question 18

WEAK ACID

Answer 18

Only releases a small amount of H+ ions when dissolved in water and partially dissociates.

Question 19

BASE

Answer 19

Metal oxide, metal hydroxide or ammonia

Proton acceptor

Question 20

ALKALI

Answer 20

Base that releases OH- ions when dissolved in water

Question 21

SALT

Answer 21

Product of a neutralisation reaction where its H+ protons are replaced by a metal or ammonium ion.

Question 22

ORBITAL

Answer 22

a region of space where it is most likely to find an electron. It is in an electron cloud that can only hold 2 electrons at a time

Question 23

IONIC BOND

Answer 23

the electrostatic attraction between a postive and negative ion to form an ionic compound

Question 24

COVALENT BOND

Answer 24

the strong electrostatic attraction between a shared pair of electrons and the nucei of the bonded atoms

Question 25

DATIVE COVALENT BOND

Answer 25

covalent bond where the electrons are shared from one of the atoms that usually existed as a lone pair.

Question 26

ELECTRONEGATIVITY

Answer 26

The ability for an atom in a covalent bond to attract the shared pair of electrons towards itself.

Question 27

POLAR

Answer 27

In order for a molelcule to be polar, there must be differences in electronegativity between the two bonded atoms. One of the atoms will attract the pair of electrons towards itself and introduce a dipole. A polar molecule will have positive and negative regions in the molecule which is a permanent dipole

Question 28

LONDON FORCES

Answer 28

These are induced dipole-dipople interactions that occur in all compounds when the electron moves around, it will create an instantaneous dipole which will introduce a dipole in the neighbouring molecules.

Question 29

PERMANENT DIPOLE

Answer 29

These are the dipoles of a polar bond that will be there permanently because of the difference in electronegativity

Question 30

HYDROGEN BONDS

Answer 30

This is the electrostatic attraction between the lone pair of electrons on a partially negative atom on one molecule and an electron deficient partially positive hydrogen on another molecule.

Question 31

FIRST IONISATION ENERGY

Answer 31

This is the energy taken to remove one mole of electrons from one mole of gaseous atoms to make one mole of gaseous 1+ ions

Question 32

SECOND IONISATION ENERGY

Answer 32

This is the amount of energy needed to remove an electron from one mole of gaseous 1+ ions of an element to make one mole of 2+ ions

Question 33

METALLIC BONDING

Answer 33

The electrostatic attraction between a metal cation and a negative delocalised electron that make up the metals structure.

Question 34

GIANT COVALENT LATTICE

Answer 34

This is a giant structure that has covalent bonds on all sides bonding them together. It's usually carbon that makes up the lattice and can exist in many forms such as diamond, graphite or graphene.

Question 35

ENTHALPY CHANGE

Answer 35

How the heat energy has changed and you normally do products - reaction enthalpy to work it out

Question 36

LAW OF CONSERVATION OF ENERGY

Answer 36

It states energy cannot be created or removed, it can only be transferred between systems

Question 37

EXOTHERMIC

Answer 37

When more energy is transferred from the system to the surroundings, so the enthalpy is negative. This is when you form bonds

Question 38

ENDOTHERMIC

Answer 38

This is when energy is transferred from the surroundings to the system so the enthalpy change is positive and this happens when bonds are formed.

Question 39

ACTIVATION ENERGY

Answer 39

This is the minimum amount of energy needed for a reaction to take place which breaks the bonds of the reactants so they can start reacting

Question 40

ENTHALPY CHANGE OF REACTION

Answer 40

This is the enthalpy change when reactants as seen in the reaction equation in their standard states react under standard conditions to form products in their standard states

Question 41

ENTHALPY CHANGE OF FORMATION

Answer 41

The enthalpy change when 1 mol of product is formed in its standard states when it's elements react in their standard states under standard conditions

Question 42

ENTHALPY CHANGE OF COMBUSTION

Answer 42

The enthalpy change when 1 mol of a substance reacts completely with oxygen in their standard states under standard conditions to form products in their standard states.

Question 43

ENTHALPY CHANGE OF NEUTRALISATION

Answer 43

Enthalpy change when one mole of water is formed after an acid and a base react together in standard conditions, all reactants and products are in standard states.

Question 44

SPECIFIC HEAT CAPACITY

Answer 44

The amount of energy required to raise 1g of a substance by 1K

Question 45

AVERAGE BOND ENTHALPY

Answer 45

The amount of energy required to break 1 mol of a specific bond in a gaseous molecule.

Question 46

HESS' LAW

Answer 46

States that a reaction can take place in two alternate reaction pathways as long and as long as the start and finishing conditions are the same, the average bond enthalpies will be the same.

Question 47

COLLISION THEORY

Answer 47

It states that in order for a successfull reaction to take place, two reacting particles must collide successfully at the correct orientation

Question 48

HOMOGENOUS CATALYST

Answer 48

This is a catalyst that has the same states as the reactants and will react to form an intermediate. E.g. esters use H2SO4 as a catalyst

Question 49

HETEROGENOUS CATALYST

Answer 49

This is a catalyst that has different physical states than the reactants in the reaction. They will absorb the reactants, catalyse them then desorb them.

Question 50

DYNAMIC EQUILIBRIUM

Answer 50

To be in dynamic equilibrium, the forward reaction has to be the same rate as the reverse reaction and the concentration of reactants and products don't change.

Question 51

LE CHATELIERS PRINCIPLE

Answer 51

He stated that when a system in equilibrium undergoes a change, the equilibrium will shift and readjust to minimise that change.