Separating Mixtures Definitions Flashcards
Filtration
Separates an insoluble solid from a solution/liquid. The residue remains on the filter paper and the filtrate runs through the filter paper.
Simple Distillation
Separates the solvent from a solution. It can also be used to determine the boiling point of a substance. For example, pure water can be obtained from seawater by distillation.
Fractional Distillation
(A fractionating column is added to the distillation apparatus.)
Separates mixtures of miscible liquids (e.g. ethanol and water), because they have different boiling points. The substance with the lowest boiling point is collected as the first distillate.
Separating Funnel
Separates immiscible liquids (e.g. oil and water). The liquid with the greatest density separates out as the lower layer is run off using the tap.
Centrifuge
Separates solid or liquid particles of different densities by spinning the sample. Used to separate precipitates from a solution - the solution can be decanted from above the precipitate after centrifuging the sample.
Used in laboratories e.g. in hospitals to separate the components of blood.
Magnetism
Iron, steel (an alloy of iron), nickel and cobalt are all attracted to magnets due to their magnetic properties. They are used to select and move scrap iron for recycling.
Crystallisation
Used to remove small quantities of an impurity from a solid, if the two substances have different solubilities.
- The impure sample is dissolved in a minimum volume of hot solvent (or excess solvent can be removed from a solution by partial evaporation).
- As the solution slowly cools, the saturated substance crystallises out, leaving behind the far more dilute impurity in the solution.
- The mixture is then filtered and the crystals washed with a small amount of cold solvent.
- The crystals can be dried between two filter papers or placed in a warm oven below 100 degrees celsius.
Paper Chromatography
Paper chromatography separates mixtures of solids e.g. dyes. Each substance has a different solubility in the solvent used and therefore the substances in the mixture will travel different distances up a piece of chromatography paper with the solvent.
Residue
The insoluble solid that remains after filtration.
Sublimation
Sublimation separates a mixture of solids, one of which sublimes. On cooling, the gas of the subliming solid changes back to a solid. By heating the mixture, the solid that sublimes can stick to the cold surface of the overturned filter funnel and therefore be collected.
Evaporation
The solution is heated either directly over a Bunsen flame, if the solvent is not flammable, or on a water bath, if the solvent is flammable. The solvent evaporates, leaving the solid behind.
Decanting
The denser solid settles to the bottom of the beaker and the liquid can be fully poured away.
Flotation
This is used to separate lower density solids from higher density solids by scooping the less dense solid off the surface of the liquid (which has to be added to the mixture) while leaving the higher density solid in the liquid.
Sieving
A sieve is used to separate larger particles from smaller ones in a mixture. The larger particles stay behind on the sieve because they are too big to pass through. The smaller particles are able to get through the holes in the sieve e.g. pebbles and sand, tea leaves in tea.
Filtrate
The liquid resulting from the filtering process
