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Science · Grades 5–8

Mixtures and choosing a separation method

Particle size, magnetism, solubility and boiling behaviour can help separate mixtures.

Make a worksheet

Understand the idea

Use differences in properties

Particle size, magnetism, solubility and boiling behaviour can help separate mixtures.

Dissolving is not disappearance

A dissolved substance remains present in the solution.

Keep examples theoretical

Do not taste unknown materials or heat substances without suitable supervision.

Worked examples

Which method can separate insoluble sand from water?

A suitable filter retains the solid particles.

filtration

Which mixture could a magnet help separate?

Iron is attracted by an ordinary magnet; sand is not.

iron filings mixed with dry sand

Try it yourself

  1. Why does filtering salt water through ordinary filter paper not remove dissolved salt?

  2. Which process can leave dissolved salt behind as water leaves a solution?

    1. evaporation
    2. sieving large stones
    3. freezing every substance instantly
    4. magnetic attraction

  3. A mixture differs from a pure compound because its components

    1. must all be solids
    2. must always be visible
    3. are combined physically and need not have a fixed ratio
    4. always form a new element

  4. Choose a method to separate gravel from fine dry sand and explain the property used.

Answers and marking notes

Answers and marking notes
  1. Dissolved ions pass through the paper with the water; they are not large suspended particles.

    Credit the difference between dissolved and suspended material.

  2. evaporation

    The water can leave as vapour while nonvolatile salt remains.

  3. are combined physically and need not have a fixed ratio

    Mixtures can have variable composition.

  4. Use a sieve with suitable openings; the particles have different sizes.

    Credit an appropriate size-based method.

Further reading and review references

These are reference links, not copied exercises, institutional endorsement or proof of independent review.

Preview material · independent educational review required. Grade bands are approximate, not official curriculum alignment.