METHODS OF SEPARATING MIXTURES

There are different methods used to separate mixtures based on the type of substances involved.

1. Filtration

Used for: Separating an insoluble solid from a liquid (e.g. sand from water).

How it works:
The mixture is poured through a filter paper.
The liquid passes through (called filtrate), while the solid stays on the paper (called residue).

Procedure:

• Fold filter paper and place it in a funnel.

• Place a beaker under the funnel.

• Pour the mixture into the funnel.

• Collect the filtrate and discard or examine the residue.

2. Decantation

Used for:

• Separating immiscible liquids (do not mix) like oil and water.

• Separating a solid that has settled at the bottom of a liquid.

How it works:
One layer is slowly poured off into another container.

Procedure:

• Let the mixture settle.

• Carefully pour off the top layer (liquid) into a new container.

• Leave the solid or other liquid behind.

3. Evaporation

Used for:
Getting back a soluble solid from a solution (e.g. salt from saltwater).

How it works:
The liquid evaporates on heating and leaves the solid behind.

Procedure:

• Pour the solution into an evaporating dish.

• Heat gently using a Bunsen burner or sunlight.

• Allow the solvent to evaporate.

• Collect the solid that remains.

4. Simple Distillation

Used for: Separating a solvent from a solution (e.g. pure water from salty water).

How it works:
The solvent boils, turns into vapour, then is cooled and collected. The solute remains behind.

Procedure:

• Heat the solution in a round-bottom flask.

• Vapour passes through a condenser where it is cooled.

• The pure solvent is collected in another container.

5. Fractional Distillation

Used for:
Separating miscible liquids with different boiling points (e.g. ethanol and water).

How it works:
Liquids boil at different temperatures. The one with the lowest boiling point evaporates first and is collected first.

Procedure:

• Heat the mixture in a flask connected to a fractionating column.

• Vapours rise and condense depending on their boiling points.

• Collect different liquids at different temperatures.

6. Chromatography

Used for:
Separating mixtures of coloured substances (e.g. inks, dyes, plant pigments).

How it works:
Substances in the mixture move at different speeds in a solvent along the paper.

Procedure:

• Draw a pencil line near the bottom of chromatography paper.

• Place a drop of the mixture on the line.

• Dip the bottom of the paper in a solvent (e.g. water).

• Let the solvent travel up the paper.

• Different substances will form coloured spots.

• Mark the solvent front (the highest point reached by the solvent).

7. Magnetism

Used for:
Separating magnetic materials from non-magnetic ones (e.g. iron from sand).

How it works:
A magnet attracts only magnetic materials like iron, nickel, and cobalt.

Procedure:

• Pass a magnet over the mixture.

• Magnetic substances stick to the magnet.

• Non-magnetic ones remain behind.