Various techniques are utilized to separate different types of mixtures based on their physical properties. Evaporation is effective for isolating soluble solids from liquids, provided the solids do not decompose upon heating.
Dry the crystals between two pieces of filter papers.
Filter to obtain the crystals.
Allow the heated solution to cool and crystals are formed gradually.
A saturated solution is obtained.
Gently heat the solution until most of the water is evaporated.
The liquid with the higher density will sink to the bottom of the seperating funnel and can be removed by turning on the tap.
Seperating liquids that are not miscible
To seperate these liquids, we use a seperating funnel.
Example: oil and water
If two liquids cannot mix together, they are known as liquids that are immiscible.
Seperating liquids that are miscible
If two liquids can mix together, they are known as liquids that are miscible
Vapour of the liquid with higher boiling point condense along the fractionating column and re-enter the flask where the liquids are being boiled.
During the process of fractional distillation, the mixture of liquids boils and may distil together
Boiling chip must be present to smoothen the boiling process.
Liquid with the lower boiling point will be collected.
The liquids are able to be seperated as they have different boiling points.
Fractional distillation is used to seperate the liquids.
How does chromatography work?
Substances that are oure have only one spot while the substances that are not pure have more than one spot.
Due to the different rates of moving through the paper, the various dyes seperate out from one another.
The one that is less soluble moves the slowest may reach only the middle of the paper.
The one that is more soluble moves the fastest reaches the edge of the paper first.
As it continues to move, the different substances in the dye move along with it but at different speed.
When it reaches the spot of the dye, it dissolves the substances in the dye.
The solvent in the test-tube moves up the paper.
Example of solvent: water, ethanol.
For paper chromatography to work, the dye must be soluble in the solvent.
Seperating techniques
Paper Chromatography
Example: Different coloured dyes in black ink, seperate dyes in food colouring , drugs in urine
Paper chromatography is used to seperate coloured components in a mixture.
Magnetic attraction
Example of substances with magnetic properties: Iron, steel, nickel, cobalt.
A magnet can be used to seperate magnetic substance from non-magnetic substance.
Simple distillation
Example:To obtain water from saltwater,seawater.
Used to obtain liquid from solution.
Evaporation
Example for solids that decompose: Sugar ; Copper(II) sulfate.
This method can only be used for solids that do not decompose when heated.
To obtain the solid, the solution is evaporated to dryness and the solid is recovered.
Used to seperate soluble solids from liquids.
Crystallisation
Example: sugar from water; copper sulfate from water.
Used to seperate soluble solids that decompose when heated from liquids.
Filtration
The substance that passes through is called the filtrate.
The solid trapped by the filter paper is called the residue.
A filter paper is used to seperate the insoluble solids from the liquids. The filter paper contains small pores that allows liquid and soluble solids to pass through but not the insoluble solids.
