Purity & Separating Mixtures Flashcards
what does pure substance mean in chemistry
pure substances are substances that contain only one element or compound
whats the boiling point for mixtures like
it ranges
how do you work out the level of purity of a substance
the closer your values of your experiment are to those in the data book, the purer a sample is
give examples of pure substances
1) Water
2) Copper sulfate
3) Glucose
4) Oxygen gas
whats the special technique used to separate mixtures of liquids
Distillation
what does simple distillation do
separates 2 liquids with different boiling points. the vapour passes through a condenser where the vapour turns back into a liquid
what happens in fractional distillation
The mixture is slowly heated until the liquid with the lowest boiling point boils and then condenses.
Then we increase temperature slowly to collect (boil then condense) the other fractions.
Name the 5 main methods of separating mixtures:
1) Crystallisation
2) Filtration
3) Chromatography
4) Simple distillation
5) Fractional distillation
what happens in Chromatography
—- Separates solutions with a number of different solutes (solids) in the solvent (liquid).
Place a drop of the solution to be separated near the bottom of a piece of chromatography paper.
Dip the very bottom of the paper into a suitable solvent.
The solvent (liquid) moves up the paper and carries the solutes (solids) in the solution with it.
Different solutes (solids) move at different speeds, so they separate on the paper.
Crystallisation
what happens in crystallisation
—— Separates solutions into their constituent (different) parts:
dissolved solids (solutes) and liquids (solvents).
Heat the mixture so that the solvent evaporates.
Eventually, crystals of the solute (dissolved solids) will form.
We can collect the solvent (liquid) by condensing it as it evaporates.
