Class 6 Science: Separation of Substances

Separating a mixture is a decision problem: identify the differences between the materials, then choose a method that uses one difference effectively.

What to understand

Describe the central idea in your own words.
Use a model, observation or relationship to explain a changed example.
Notice and correct the likely misconception in the worked reasoning.

Choose a method by property

Handpicking works when pieces are large and visibly different. Sieving uses particle size. Filtration uses an insoluble solid that is trapped while a liquid passes through. Evaporation removes a solvent when the dissolved solid is the useful remainder.

A method may need more than one stage. Muddy salt water could be allowed to settle, filtered to remove fine soil, and evaporated if recovering salt is required.

Worked reasoning: For sand and water, filtration is sensible because sand does not dissolve. For salt and water, filtration will not separate the dissolved salt; evaporation is the relevant next step. The question is not “which method do I remember?” but “what property differs?”

Try, explain and check

Scenario

Design a two-step method for separating iron filings, sand and water.

Show a reasoning prompt

State the evidence, relationship or model that supports your answer, then check whether the units and direction make sense.

Check

Which component is recovered at each stage?

Show a reasoning prompt

State the evidence, relationship or model that supports your answer, then check whether the units and direction make sense.

Misconception

A clear liquid is not necessarily pure; dissolved material may be invisible.

Show a reasoning prompt

State the evidence, relationship or model that supports your answer, then check whether the units and direction make sense.

Next step

Write a three-sentence revision summary, then continue to the related resource. For extra practice, visit the resource library and choose a worksheet that matches the skill you need.

About this resource
Prepared as part of the BIS Quiz learning resource. It is supplementary study material; use your teacher's instructions and prescribed materials when they differ. Report a factual error or unclear explanation.