CC2 Purifying substances Flashcards
What is an insoluble substance?
a substance that is’nt dissolveable
What is a soluble substance?
soluable is a substance that can be dissolved
What is a solvent?
A liquid used to dissolve a solute
What is a solution?
a mixtured formed by a solute dissolving in a solvent
What is a solute?
A solid that is dissolved
How can chromatography show the difference between pure and impure substances?
Pure ones will only make one dot, impure substances will make more
How is the Rf value calculated?
distance moved by spot/distance moved by solvent
What does a substance’s Rf value depend on?
How soluble it is in the solvent
In chromatography, why must the substances be placed on a pencil line?
Pencil will not dissolve in the solvent
In chromatography why must the solvent height be lower than the pencil line?
So that the substances do not dissolve into the solvent off the paper
In chromatography, what would cause an ink not to produce any pattern?
If the ink was not soluble in water
In chromatography, what could you change if an ink did not produce any pattern?
change the solvent to one the ink is soluble in i.e. ethanol instead of water
How is the melting point of a pure substance different from that of an impure substance?
Pure substance has one specific melting point. Impure substance has a melting range.
What is simple distillation used to separate?
A single liquid from a mixture
What is fractional distillation used to separate?
Multiple liquids of different boiling points
What is filtration used to separate?
An insoluble solid from a liquid
What is crystallisation?
Forming crystals of a soluble solid from a solution.
What is potable water?
Drinking water
What are the stages used to make water potable.
Sedimentation, filtration and chlorination
How can sea water be made potable?
By distillation
What is a pure substance?
A substance made of one type of atom or molecule only.
How would you separate water from salt water?
Simple distillation
How would you separate salt from salt water?
Crystallisation
Why must chemical analysis be done with pure water?
Because dissolved salts in non pure water would give false positive results.
