Separating a soluble solid from a liquid
Lesson details
Learning outcome
I can explain how dissolving can be reversed to separate a soluble solid from a liquid.
Key learning points
- Evaporation can remove solvent from a solution, leading to the production of a saturated solution.
- Crystallisation reforms a solute as crystals from a saturated solution following a change in conditions.
- Solvents evaporate into the air around you during the process of crystallisation.
- Larger crystals form when the solvent evaporates more slowly.
- Heating a solution makes the solvent evaporate more quickly.
Keywords
Solute - A solute is a substance that has dissolved into a solvent.
Solvent - A solvent is a liquid into which a solute dissolves.
Evaporation - Occurs when a substance's particles are in the liquid state at its surface with enough energy to change to the gas state and mix with air.
Crystallisation - A process that forms solid crystals from a saturated solution by evaporating the solvent.
Crystal - A crystal is a solid whose particles are arranged in a highly ordered, repeating pattern.
Common misconception
Pupils sometimes use the terms evaporation and boiling interchangeably, but they are not the same.
Boiling: a liquid substance is heated & gas bubbles form. Evaporation: same, BUT only on the surface of the liquid & the gas mixes with air.
Teacher tip
Try contextualising crystallisation by looking at its process and results in nature (Cueva de los Cristales, Mexico) and art (Roger Hiorns, 'Seizure').
Content guidance
Risk assessment required - equipment
Supervision
Adult supervision required
Licence
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.What process happens when a solid can be observed to 'disappear' in a liquid to make a solution?
Q2.When a process is able to go backwards, or be "undone", it is said to be .
Q3.Match the word to the definition.
When a solid can dissolve in a liquid
When a solid cannot dissolve in a liquid
The mixture formed when a solid dissolves in a liquid
When no more solid can dissolve
Q4.Put the following changes of state for ice/water in order starting from the one that requires the lowest temperature to the one that requires the highest temperature.
Q5.A volume of salt solution containing 0.5 g of salt was placed in a beaker and left for 2 weeks on the windowsill, after which only crystals of salt remained. How much salt would be present?
Q6.Sugar was added to water at 60℃ until no more sugar could dissolve. The solution was left to cool. What would you expect to see and why?
Assessment exit quiz
6 Questions
Q1.What is a solute?
Q2.Dissolving is a process as solute can be added to the solvent and the solvent can then be evaporated to recover the solute.
Q3.Which definition best describes evaporation?
Q4.What happens to the size of crystals formed during crystallisation if the solvent evaporates slowly?
Q5.What is the name of the process that forms solid crystals from a saturated solution by evaporating the solvent?
Q6.Solvents evaporate into the air during crystallisation. How does heating affect this process?
To help you plan your 7 science lesson on: Separating a soluble solid from a liquid, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your 7 science lesson on: Separating a soluble solid from a liquid, 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.