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Separating mixtures: getting clean water and salt from muddy salt water

By OtisamLMS · 21 Oct 2026

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Subject
Science · JHS
Year
JHS 2
Week
Term 1 · Week 5
Lessons
3 × 60 min
Class size
45
Strand
Diversity of matter
Sub-strand
Materials: mixtures and separation
Content standard
Learners choose and use suitable methods to separate mixtures and relate them to everyday activities.
Key words
mixturefiltrateresiduesolutesolventevaporationfiltration

Learning indicators

  • Describe filtration and evaporation
  • Choose a separation method based on the properties of the parts of a mixture
  • Link separation methods to local activities such as salt winning

Core competencies

  • Critical thinking and problem solving
  • Collaboration
  • Personal development (safety awareness)

Resources

  • Muddy salt water in labelled bottles
  • Funnels and filter paper (or a clean cloth)
  • Evaporating dishes or tin lids, a small burner or charcoal stove, tongs

Lesson flow

  1. 1Starter

    Show the muddy salt water and ask: how could we get drinkable-looking water and dry salt back out of this? Groups list as many ideas as they can in two minutes.

  2. 2Main activities

    1. Discuss the ideas and sort them: which deal with the mud, which deal with the salt? 2. Groups filter the mixture and describe the residue and the filtrate. Is the filtrate clean? Taste test is not allowed; explain why. 3. The teacher heats a small amount of filtrate in a dish until the water evaporates. Learners observe from a safe distance and record what is left. 4. Groups draw a flow chart of the two steps with labels. 5. Link to salt winning along the coast: which step does the sun do for the salt makers?

  3. 3Reflection

    Learners explain to a partner why filtering alone could not remove the salt.

Assessment

Label a filtration diagram; choose and justify a method for sand and water, salt and water, and iron filings and sand.

Differentiation

Support: give the flow chart with blank boxes to fill. Extension: suggest how to get the water back as well as the salt (lead towards distillation).

Homework

Find one way mixtures are separated at home (sieving flour, winnowing rice) and name the property that makes it work.

Teacher notes

Only the teacher handles the heat source. Keep a bucket of sand nearby.
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