Separating mixtures is a familiar component of many school science curricula. Demonstrations are usually straightforward yet engaging ways to introduce separation techniques. First ask the pupils for suggestions on how to achieve the separations. Tease out answers with pertinent questions where necessary. This will engage the pupils even more and make the lessons more educationally worthwhile.
- Skill level:
- Moderately Easy
Things you need
- Filter paper
- Evaporating basin
- Iron filings
Separate sand and water using filtration. Explain that sand is an insoluble substance. In other words, it doesn't dissolve like similar substances such as salt. Part-fill a flask with water and add sand. Stir the mixture to demonstrate that sand doesn't dissolve. Let pupils stir the mixture too. Place a circular piece of filter paper in a funnel and place the funnel into another flask. Pour the water and sand mixture over the filter. The water goes through while the sand remains, separating the mixture.
Separate salt and water by evaporation. Explain that salt is a soluble substance, which means it dissolves in water. Part-fill an evaporating basin with water and add salt. Stir the mixture to demonstrate the salt dissolves. Let pupils stir the mixture too. Place the evaporating basin on a tripod. Light and place a burner below the tripod to apply heat to the mixture. The water will evaporate, leaving the salt behind.
Separate iron filings from sand by magnetism. Explain that sand and iron filings are solids. Mix small amounts of the two solids together. Pass the magnet through the mixture and it will attract the iron filings and leave the sand behind. Clean the iron filings from the magnet. Continue the process until all the iron filings have been separated from the sand.
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