The following are the typical questions that you'll find in many of the past papers. Each question also comes along with the generic answer that the examiners are looking for, so if you learn these definitions then you should be able to answer these questions pretty easily when they come up. If you think that I've missed out any important questions/answers or you'd like to correct any mistakes then feel free to mention them in the comments and I'll make adjustments as soon as possible.
Typical structure: Question (Marks Available): Answer.
NB: Underlined words/phrases are the key terms needed to get the marks. Different points are highlighted in different colours.
NB: Underlined words/phrases are the key terms needed to get the marks. Different points are highlighted in different colours.
AQA AS CHEMISTRY REVISION NOTES 1: SIMPLE DEFINITIONS
Relative atomic mass (2):
(Average/mean mass of one atom of an element) ÷ (1/12
mass of one atom of 12C) OR
(Average/mean mass of atoms of an element) ÷ (1/12
mass of one atom of 12C) OR
(Average/mean mass of atoms of an element x12) ÷ (mass of one atom of 12C) OR
(Average mass of one mole of atoms) ÷ (mass of one atom of 12C) OR
(Weighted average mass of all the isotopes) ÷ (mass of one atom of 12C) OR
Average mass of an atom/isotope (compared to C-12) on a scale in which C-12 has a mass of 12.
Mass number (of an isotope) (1):
Total number of protons and neutrons in the nucleus of an atom.
Electronegativity (2):
Power of an atom/nucleus to withdraw/attract electrons/electron density/a pair of electrons in a covalent bond.
Structural isomers (2):
Compounds that have the same molecular formula but a different structural/displayed/skeletal formula.
Rate of reaction (1):
Change in concentration (of a substance/reactant/product) in unit time/given time OR
Amount of substance used up/formed in unit time/given time.
Activation energy (1):
Minimum energy required for a reaction to start OR
Minimum energy for a successful/effective collision.
Le Chatelier's Principle (1):
If a factor is changed that affects an equilibrium, then the position of the equilibrium will shift/move so as to oppose/counteract the change OR
When a system/reaction in equilibrium is disturbed, the position of equilibrium shifts/moves in a direction which tends to reduce the disturbance.
What is a catalyst (1):
A substance that speeds up the reaction/alters the rate but is chemically unchanged at the end/not used up.
How does a catalyst work (2):
Catalyst provides an alternate route/pathway/different mechanism that has a lower activation energy.
Hess' Law (1):
Mass number (of an isotope) (1):
Total number of protons and neutrons in the nucleus of an atom.
Electronegativity (2):
Power of an atom/nucleus to withdraw/attract electrons/electron density/a pair of electrons in a covalent bond.
Structural isomers (2):
Compounds that have the same molecular formula but a different structural/displayed/skeletal formula.
Rate of reaction (1):
Change in concentration (of a substance/reactant/product) in unit time/given time OR
Amount of substance used up/formed in unit time/given time.
Activation energy (1):
Minimum energy required for a reaction to start OR
Minimum energy for a successful/effective collision.
Le Chatelier's Principle (1):
If a factor is changed that affects an equilibrium, then the position of the equilibrium will shift/move so as to oppose/counteract the change OR
When a system/reaction in equilibrium is disturbed, the position of equilibrium shifts/moves in a direction which tends to reduce the disturbance.
What is a catalyst (1):
A substance that speeds up the reaction/alters the rate but is chemically unchanged at the end/not used up.
How does a catalyst work (2):
Catalyst provides an alternate route/pathway/different mechanism that has a lower activation energy.
Hess' Law (1):
The enthalpy change/heat (energy) change (at constant pressure) is independent of the route/path taken.
Carbon neutral (1):
An activity that has no net/overall carbon emissions to the atmosphere/air OR
An activity that has no net/overall greenhouse gas emissions to the atmosphere/air OR
There is no change in the total amount of carbon dioxide/carbon/greenhouse gases present in the atmosphere/air.
Mean bond enthalpy (2):
Enthalpy/heat (energy) change/required/needed to break/dissociate a covalent bond. Average/mean over different molecules/compounds/substances.
Hydration (1):
Addition of water to a molecule/compound.
Enthalpy change (1):
Heat energy change at constant pressure.
Standard enthalpy of combustion (3):
The enthalpy change when 1 mol of a compound/substance/alcohol is burned completely in oxygen OR is burned in an excess of oxygen with all reactants and products in their standard states OR with all reactants and products in their normal states under standard conditions.
Standard enthalpy of formation (3):
The enthalpy/heat change at constant pressure when 1 mol of a compound/substance/product is formed from its elements with all reactants and products in their standard states OR with all reactants and products in their normal states under standard conditions.
Empirical formula (1):
Lowest number/ratio of atoms of an element.
I think this covers most of the simple definitions which you can easily learn to gain a few extra marks. Comment if there are any more that you think should be added to the list.
AKBIT-HOE, 22:47 15/05/2015
Carbon neutral (1):
An activity that has no net/overall carbon emissions to the atmosphere/air OR
An activity that has no net/overall greenhouse gas emissions to the atmosphere/air OR
There is no change in the total amount of carbon dioxide/carbon/greenhouse gases present in the atmosphere/air.
Mean bond enthalpy (2):
Enthalpy/heat (energy) change/required/needed to break/dissociate a covalent bond. Average/mean over different molecules/compounds/substances.
Hydration (1):
Addition of water to a molecule/compound.
Enthalpy change (1):
Heat energy change at constant pressure.
Standard enthalpy of combustion (3):
The enthalpy change when 1 mol of a compound/substance/alcohol is burned completely in oxygen OR is burned in an excess of oxygen with all reactants and products in their standard states OR with all reactants and products in their normal states under standard conditions.
Standard enthalpy of formation (3):
The enthalpy/heat change at constant pressure when 1 mol of a compound/substance/product is formed from its elements with all reactants and products in their standard states OR with all reactants and products in their normal states under standard conditions.
Empirical formula (1):
Lowest number/ratio of atoms of an element.
I think this covers most of the simple definitions which you can easily learn to gain a few extra marks. Comment if there are any more that you think should be added to the list.
AKBIT-HOE, 22:47 15/05/2015
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