Separating Mixtures (Separation of solid-liquid mixtures (Chromatography…
Separation of solid-liquid mixtures
It is used to separate an insoluble solid from a liquid
Eg:Filtration can be used to separate cloak powder from water
A filter paper is used to filter an insoluble solid from a liquid
A filter paper has very tiny pores.Only the particles with size smaller than the pores can pass through the pores.The insoluble solids have larger particle sizes they are trapped on the filter paper.
The features of filtration
Small liquid particles can pass through pores
Large solid particles trapped on filter paper
In filtration, the insoluble solid that remains on the filter paper is called the residue.The liquid that passes through the filter paper is called the filtrate
A metrod to separate a dissolved solid from a solution by heating the solution to dryness
Only used for
Heat stable substances
will not decompose upon strong heating
Dried salt crystals are obtained in the evaporating dish
Solution in the evaporating dish is heated until the solvent has dried up completely.
Application of evaporation in our daily lives
Evaporation of sweat cools our body down and thus helps our body to maintain a constant body temperature during hot days
Common salt is obtained through evaporation of seawater
How to analyse a chromatogram
A single spot
Sample X is a pure substance as it is made up of one component only.
2 or more spots
Sample X is a mixture.In this chromatogram , it shows that it is made up of three components.
Too much Sample X is placed on the starting line.
To improve the result, a small and concentrated sample should be placed by using fine capillary tubes.
This would ensure that the dyes are clearly separated in distinct lines or spots.
Sample remains on the starting lines.
Sample X does not dissolve in the solvent.
A change in the solvent is required.
Different distance travelled.
Components M and N have different solubility in the same solvent .
Component M is more soluble in the solvent, so it travels faster and covers a greater distance.
Complete matching of spots in the same solvent.
Samples X and Y are identical.
Partial matching of spots in the same solvent.
Sample X and Y are not identical.
Samples X and Y contain two identical components
A sample which is made up of other samples.
Sample X contains two components and one component of sample Z.
Hence, sample X is made by the combinations of samples Y and Z.
Application of chromatography in our daily lives
To identify the contents of a mixture
To test the purity of a substance
Only a small amount of sample is required
Gives a fast and an accurate analysis of a sample
Able to separate complex mixtures such as food dye
Components in the sample
It is useful to separate and identify small amounts of substances that are dissolved in a solvent, such as dyes in coloured ink.
small amount of concentrated sample
placed on the starting line of a chromatographic paper
The chromatographic paper is placed inside a beaker containing a solvent.
The solvent is below the starting line.
As the solvent moves up the paper
it separates the sample into its respective components.
The chromatographic paper is removed.
before the solvent reaches the edge of the other end of the paper.
Application of simple distilation in our daily lives
When the hot saturated solution is cooled,The cooled solution cannot hold as much solute as when it was hot
Solutes have a high solubility in hot water than cold water
Eg:The amount of copper[II]sulfate dissolved in 80 degrees Celsius is higher than that in 30 degrees Celsius of the same amount of water
The excess amount of solute in a cooled solution will become undissolved and forms crystals
Application of crystalisation in our daily lives
production of silicon
The main component of most semiconductor devices.Eg:radio, computers, telephones
Eg:Table sugar is obtained from sugar beet or sugar cane
The salt solution is filtered to remove any solid impurities
The filtrate is heated to remove most of the solvent until the solution becomes saturated.A saturated solution enables the crystals to form easily
The saturated solution is left to cool gradually to allow the formation of large-size crystals
The crystals are filtered and washed with little cold distilled water to remove impurities.They are then dried between filter paper
It is a method to separate a soluble solid from its solution which is not heat-stable.The soluble solid that is not heat-stable decomposes on strong heating.
The need for separating mixtures
Mixtures consists of 2 or more substances which are mixed without chemically bonded together
The purity of substances is important in our daily lives
Mixtures can be separated easily into pure substances by purification techniques.These techniques are physical methods
The four national taps
Separation of solid-solid mixtures
What is it?
A strong electromagnet is used to salvage scrap iron and steel from other junk materials
To separate magnetic ores from none-magnetic ores
To remove iron splinters from patient's eyes
What is it?
Separation of liquid-liquid mixtures