lesson
Separate by a useful difference
1 · Learn
Sieving can separate pieces with different sizes using holes that let smaller pieces through. Filtering can separate an insoluble solid from a liquid when the solid is trapped by the filter.
A paper filter does not normally remove dissolved salt from water because the dissolved material travels through with the liquid. Choose the method for the mixture, not just the equipment you have.
2 · Worked example
For sand and water, suitable filtration can retain the sand. For salt solution, the filtrate still contains dissolved salt.
3 · Your turn
Would ordinary filter paper recover dissolved salt from its water solution? What mixture could it help separate?
Check your answer
No. It could help separate an insoluble solid such as sand from water.
4 · Apply your learning
Plan how to separate a safe model mixture in stages. Explain the property used by each stage before watching an adult-approved demonstration.
Adult guidance and safety
Filtered classroom water is not drinking water. No tasting, dirty environmental samples or sharp particles.
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Check a calculation · Year 5 onward
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