Separating pure salt from dirty rock salt
Lesson details
Learning outcome
I can suggest how to combine separation techniques in order to separate pure salt from a sample of rock salt.
Key learning points
- The properties of the substances in a mixture help to determine the technique best suited to separate them.
- When mixtures contain more than two components, multiple techniques may be needed to separate them.
- Creating a solution of an existing mixture can allow a specific technique to be used for separation.
- Separating salt from rock salt requires: making a solution, filtration, and crystallisation.
Keywords
Separation technique - A process or method used to isolate a substance from a mixture, usually to obtain a pure sample of it.
Property - A property is a feature or characteristic of a substance that can be used to classify it, or describe how it behaves.
Soluble - When a substance dissolves in a liquid it is described as soluble in that liquid.
Insoluble - An insoluble substance is one that will not dissolve in a particular solvent.
Common misconception
Filtration alone can separate salt from rock salt - idea that only one technique is needed.
Highlight that each separation technique (so far) creates two products; one of them may still be a mixture that requires further separation.
Teacher tip
If you don't have rock salt, create a mixture of salt & sand. For added fun, add a few anti-bumping granules to act as 'jewels' and challenge pupils to further separate the jewels too.
Content guidance
Risk assessment required - equipment
Supervision
Adult supervision required
Licence
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.True or false? If a substance is described as 'soluble', then it means it can be dissolved in a solvent.
Q2.Which of the following can filtration be used for in the context of separating mixtures?
Q3.Which of the following properties is not a physical property?
Q4.Which property is most important when choosing a solvent to dissolve a substance?
Q5.Substances that do not dissolve in a liquid are described as ...
Q6.True or false? Crystallisation is a process that only occurs at high temperatures.
Assessment exit quiz
6 Questions
Q1.Put the following steps in the correct order to separate salt from rock salt.
Q2.The process of producing solid crystals by evaporating the solvent from a saturated solution is called ...
Q3.When a substance dissolves in a liquid it is described as in that liquid.
Q4.Which of these statements best describes the purpose of creating a solution in the separation process of pure salt from rock salt?
Q5.True or false? Sand, being insoluble in water, can be completely removed from rock salt using crystallisation.
Q6.When dissolving salt into water, the solution will reach a point where no more salt can be dissolved at a given temperature. When no more solute can be dissolved we have made a solution.
To help you plan your 7 science lesson on: Separating pure salt from dirty rock salt, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your 7 science lesson on: Separating pure salt from dirty rock salt, download all teaching resources for free and adapt to suit your pupils' needs.
The starter quiz will activate and check your pupils' prior knowledge, with versions available both with and without answers in PDF format.
We use learning cycles to break down learning into key concepts or ideas linked to the learning outcome. Each learning cycle features explanations with checks for understanding and practice tasks with feedback. All of this is found in our slide decks, ready for you to download and edit. The practice tasks are also available as printable worksheets and some lessons have additional materials with extra material you might need for teaching the lesson.
The assessment exit quiz will test your pupils' understanding of the key learning points.
Our video is a tool for planning, showing how other teachers might teach the lesson, offering helpful tips, modelled explanations and inspiration for your own delivery in the classroom. Plus, you can set it as homework or revision for pupils and keep their learning on track by sharing an online pupil version of this lesson.
Explore more key stage 3 science lessons from the Separation techniques unit, dive into the full secondary science curriculum, or learn more about lesson planning.