AQA GCSE CHEMISTRY: CHEMICAL ANALYSIS
QUESTIONS WITH CORRECT ANSWERS 2026
What is a 'pure' substance, in chemistry? - CORRECT ANSWER --
a pure substance is a single element or compound, not mixed with another substance
What 2 pieces of data can we use to determine if a substance is pure, why? - CORRECT ANSWER --
pure elements and compounds MELT and BOIL at specific temperatures => MELTING POINT and BOILIN
G POINT data can be used to distinguish pure substances from mixtures
From a heating graph, how can we know if a substance is pure? - CORRECT ANSWER --
if the melting point and boiling point lines are straigh and horizontal
- and if these temperatures match the real temperatures from the internet
From a heating graph, how can we know that a substance isimpure? - CORRECT ANSWER --
if the melting point and boiling point are not straight and completely horizontal
(the substance melts and boils over a range of temperatures)
- more than one value for the melting/boiling point)
In everyday language, what is a 'pure' susbtance? - CORRECT ANSWER --
a pure substance in this context can mean anything that has had nothing added to it, so it is unadultera
ted and in its natural state, eg. pure milk
What is a formulation? - CORRECT ANSWER --
a complex mixture that has been designed as a useful product
How are formulations made? - CORRECT ANSWER --
formulations are made by mixing the components in carefully measured quantities to ensure that the p
roductBhas the required properties
Give 7 examples of formulations. - CORRECT ANSWER -- fuels
- cleaning agents
- paints
, - medicines
- alloys
- fertilisers
- foods
Why is chromatography used? - CORRECT ANSWER --
chromatography can be used to separate mixtures and give information to help identify substances
- paper chromatography allows us to separate substances based on their different SOLUBILITIES
What is the method for any general paper chromatography experiment? - CORRECT ANSWER -
1) Take a piece of special chromatography paper.
2) Draw a horizontal pencil line 2cm up.
3) Put a dot of the first colour on the pencil line and other dots along the line for any other colours (spa
ce them out).
4) Place the bottom of the paper in a solvent (a liquid that will dissolve substances) (not above the penc
il line).
What is the stationary phase in chromatography?
What is the mobile phase in chromatography? - CORRECT ANSWER --
the stationary phase is the paper because it does not move
- the mobile phase is the solvent because it does move
How can we identify a pure substance from an impure substance after carrying out paper chromatograp
hy? - CORRECT ANSWER -- a pure chemical will produce a single spot in ALL solvents
- an impure substance may separate into different spots DEPENDING on the solvent
How does paper chromatography work? - CORRECT ANSWER --
each chemical in the mixture will be attracted to the stationary phase to a different extent (chemicals t
hat are weakly attracted will move further up the paper)
QUESTIONS WITH CORRECT ANSWERS 2026
What is a 'pure' substance, in chemistry? - CORRECT ANSWER --
a pure substance is a single element or compound, not mixed with another substance
What 2 pieces of data can we use to determine if a substance is pure, why? - CORRECT ANSWER --
pure elements and compounds MELT and BOIL at specific temperatures => MELTING POINT and BOILIN
G POINT data can be used to distinguish pure substances from mixtures
From a heating graph, how can we know if a substance is pure? - CORRECT ANSWER --
if the melting point and boiling point lines are straigh and horizontal
- and if these temperatures match the real temperatures from the internet
From a heating graph, how can we know that a substance isimpure? - CORRECT ANSWER --
if the melting point and boiling point are not straight and completely horizontal
(the substance melts and boils over a range of temperatures)
- more than one value for the melting/boiling point)
In everyday language, what is a 'pure' susbtance? - CORRECT ANSWER --
a pure substance in this context can mean anything that has had nothing added to it, so it is unadultera
ted and in its natural state, eg. pure milk
What is a formulation? - CORRECT ANSWER --
a complex mixture that has been designed as a useful product
How are formulations made? - CORRECT ANSWER --
formulations are made by mixing the components in carefully measured quantities to ensure that the p
roductBhas the required properties
Give 7 examples of formulations. - CORRECT ANSWER -- fuels
- cleaning agents
- paints
, - medicines
- alloys
- fertilisers
- foods
Why is chromatography used? - CORRECT ANSWER --
chromatography can be used to separate mixtures and give information to help identify substances
- paper chromatography allows us to separate substances based on their different SOLUBILITIES
What is the method for any general paper chromatography experiment? - CORRECT ANSWER -
1) Take a piece of special chromatography paper.
2) Draw a horizontal pencil line 2cm up.
3) Put a dot of the first colour on the pencil line and other dots along the line for any other colours (spa
ce them out).
4) Place the bottom of the paper in a solvent (a liquid that will dissolve substances) (not above the penc
il line).
What is the stationary phase in chromatography?
What is the mobile phase in chromatography? - CORRECT ANSWER --
the stationary phase is the paper because it does not move
- the mobile phase is the solvent because it does move
How can we identify a pure substance from an impure substance after carrying out paper chromatograp
hy? - CORRECT ANSWER -- a pure chemical will produce a single spot in ALL solvents
- an impure substance may separate into different spots DEPENDING on the solvent
How does paper chromatography work? - CORRECT ANSWER --
each chemical in the mixture will be attracted to the stationary phase to a different extent (chemicals t
hat are weakly attracted will move further up the paper)
