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Separating sand and salt

Description

In this experiment students separate a mixture of sand and salt. This illustrates the fundamental meaning of separating an insoluble material from one which is soluble.

Credits

:
This is an experiment from the Practical Chemistry project, developed by the Nuffield Foundation and the Royal Society of Chemistry.
separating-sand-and-salt



Apparatus Chemicals

Eye protection

Beaker (250 cm3)

Glass stirring rod

Filter funnel

Filter paper

Conical flask (250 cm3)

Evaporating basin

Bunsen burner

Heat resistant mat

Tripod

Gauze

Mixture of sand and sodium chloride (salt), about 6 or 7 g per group of students (Note 1)

Refer to Health & Safety and Technical notes section below for additional information.

 







In this experiment students separate a mixture of sand and salt. This illustrates the fundamental meaning of separating an insoluble material from one which is soluble.

ADDITIONAL INFORMATION

This is a resource from the Practical Chemistry project, developed by the Nuffield Foundation and the Royal Society of Chemistry. This collection of over 200 practical activities demonstrates a wide range of chemical concepts and processes. Each activity contains comprehensive information for teachers and technicians, including full technical notes and step-by-step procedures. Practical Chemistry activities accompany Practical Physics and Practical Biology .

If you teach primary science, click the headings below to find out how to use this resource:

Skill development

Children will develop their working scientifically skills by:

  • Drawing conclusions and raising further questions that could be investigated, based on their data and observations.
  • Using appropriate scientific language and ideas to explain, evaluate and communicate their methods and findings.

Learning outcomes

Children will:

  • Observe that some materials will dissolve in liquid to form a solution.
  • Describe how to recover a substance from a solution.
  • Use knowledge of solids, liquids and gases to decide how mixtures might be separated, including through filtering, sieving and evaporating.
  • Demonstrate that dissolving, mixing and changes of state are reversible changes.

Concepts supported

Children will learn:

  • That there are various techniques that can be used to separate different mixtures.
  • That dissolving is a reversible reaction.
  • That not all solids are soluble.
  • That the rate of dissolving can be affected by various factors.
  • That melting and dissolving are not the same process.

Suggested activity use

This activity can be used as a whole-class investigation, with children working in small groups or pairs to look at how to separate the salt and sand. This could provide a stimulus for further investigations looking at how to separate other mixtures of solids, either of different particle sizes or by solubility. 

Practical considerations

Primary schools often don’t have Bunsen burners, so viable alternatives need to be sourced. Similarly, it may be difficult to source the equipment needed to evaporate water to recover the dissolved salt. Head stands and tea lights can work well as possible alternatives.

When carrying out this activity do be aware that some insoluble solids are able to form suspensions. This is where the particles appear to have dissolved, when in fact they have been spread out throughout the liquid. A good indicator that a suspension has formed is that the liquid will go cloudy or the particles can be heard scraping as the mixture is stirred.

The layout of this activity is very prescriptive as the procedure is set out on a step by step basis. An open challenge activity, with children working in small groups and devising their own methods, would extend the children’s thinking. Different groups’ suggestions could be compared and evaluated as a class.