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Criteria of Purity
a) Describe paper chromatography and interpret chromatograms
b) Describe how chromatography techniques can be applied to colourless substances.
c) Identify substances and test their purity by melting point and boiling point determination and by paper chromatography.
d)Explain the importance of purity in substances in everyday life. Eg. in foodstuffs and drugs.
can be used to identify very tiny amounts of substances
ensure that the spots are above the solvent; and the solvent just touches the tip of the paper
Start line drawn with pencil
(a) pigments from plants; (b) dyes from ink;
(c) amino acids from proteins for analysis.
- substance with no other substances mixed with them
No two substances have the same pair of melting and boiling pts. Hence melting and boiling pts. can be used to identify a substance.
Produces only one spot
Produces more than one spot
Can be differentiated by
Has sharp melting/boiling point
Melts/boils over a range of temperatures