SC2 Flashcards
methods of separating and purifying substances
what is a filter?
a filter can be used to separate some mixtures. they let liquids through but trap bigger pieces etc/
what is a hazard during crystallisation and how can it be prevented?
hot crystals spitting out when the solution is being heated. this can be prevented using eye wear .
what is chromatography/ what does it help do?
chromatography can be used to find out which coloured compounds a mixture contains
what is paper chromatography?
paper chromatography is simpler technique, that works because some compounds dissolve better in a solvent than others. when a solvent moves along a strip of paper, it carries the different substances, in the mixture at different speeds, so they are separated.
what are the difference between more and less soluble substances?
more soluble substances are carried up faster than less soluble ones, so they separate out
what is the definition of soluble?
able to dissolve in water, able to be dissolved to form a solution
what is the Rf value?
the Rf is the distance the compound has risen, divided by the distance the solvent has risen. For example, pink spots have moved up 4 cm and the solvent has moved 10cm, the Rf would be 4/10, which equals 0.4
what is paper chromatography usually used for?
it can be used to:
1. distinguish between pure and impure substances
2. identify substances by comparing the pattern on the chromatography with the patterns formed by known substances
3. identify substances by calculating their Rf values
