Separate various mixtures using appropriate techniques. Examine the various by-products of separation.
Investigate the advantages and disadvantages of fracking as a means of extracting natural gas.
We know that a mixture is formed when two or more substances are physically mixed together.
One of the characteristics of mixtures is that they can often be easily separated. Separation can be done in a number of ways:
1. Filtration is used to separate insoluble solids from liquids. Filtration involves using a material that allows only the liquid to pass through but not the solid.
An example of filtration is separating sand (the insoluble solid) from water (the liquid) using filter paper.
Filtration test z
Fig. 11.4.1 Filtration
Plan, design, carry out and write up an investigation to determine which material is the most effective at filtering: a paper towel, a cleaning cloth, photocopying paper, nylon, cotton or a coffee filter.
1. What precautions would you need to take to ensure this is a fair test?
2. Present your findings as a results table and a suitable graph.
3. Evaporation is used to separate a liquid and a soluble solid.
The solvent is evaporated and the solute is left behind in the evaporating dish.
An example of a mixture that can be separated by evaporation is salt and water.
196 196 z
Evaporating dish
Solution Gauze
Fig. 11.4.3 Evaporation
Heat z
Fig. 11.4.2 Chromatography
Solvent vapour
Filter paper
2. Chromatography is used to separate mixtures of substances that are in solution.
Solids
retained by filter paper
The different substances are carried up a piece of chromatography paper by the solvent at different rates.
An example of a mixture that can be separated by chromatography is inks in a marker.
