A complete summarised group of documents complete for GCSE Chemistry AQA 9-1. To make these Summaries I used 3 sources: The CGP revision guide, My GCSE Science Videos and Free science lessons videos. I achieved a 9 in GCSE AQA Triple Chemistry.
Pure because the change of state
is at the same temperature
C8 Chemical ANALysis
haha
Purity and Formulations
Pure substance: single element or compound not mixed with any other
substance
O2, H2O, NaCl Impure because the change of
state is at different
To test if a substance is pure, check whether it boils/ melts at a specific temperature (puretemperatures
water
boils at 100C)
Impure substances boil over a range of temperatures
Formulation: mixture that has been designed as a useful product
Medicines, lotions, fuels, paints, fertilisers, food, cleaning agents
etc.
Quantity of each component is carefully measured so it has
desired properties
Paper Chromatography
Chromatography
Physical process, doesn’t involve chemicals and no new substances made
Allows substance separation based on solubility
Stationary phase: the paper used for chromatography because it doesn’t move (liquid/ gas)
Mobile phase: solvent because it does move (solid)
What happens
1. Substances constantly move between move between mobile/ stationary phase (equilibrium
formed)
2. Each chemical in the mixture is attracted to the
stationary phase (to a certain extent)
3. Chemicals that are strongly attracted won’t
move very far/ chemicals that are weakly
attracted move further up the paper as the
solvent moves up the paper.
4. Pure chemicals produce a single spot in all
solvents, impure ones separate into different
spots
RF Values
Retention Factor: THE RATIO OF THE DISTANCE MOVED BY THE SUBASTANCE COMAPRED TO THE
DISTANCE MOVED BY THE SOLVENT
1. Measure the distance travelled by the solvent (draw 2
lines where it stops and starts)
2. Measure the distance travelled by each of the substances
3. Use the formula
Rf values should always stay the same if you repeat the experiment
Each substance should have a different RF value in different solvents
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