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Year 10
AQA
Higher

Crystallisation

I can explain the process of crystallisation and how it is used to separate substances.

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New
New
Year 10
AQA
Higher

Crystallisation

I can explain the process of crystallisation and how it is used to separate substances.

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Share activities with pupils
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Lesson details

Key learning points

  1. Crystallisation is a technique that is used to separate a soluble solute from a solution.
  2. Crystallisation involves the formation of a saturated solution and temperature differences.
  3. Crystallisation results in the loss of the solvent to the surroundings.

Keywords

  • Saturated solution - A saturated solution is one in which no more solute can dissolve in the solvent at a given temperature.

  • Crystallisation - Crystallisation is a process that forms solid crystals from a saturated solution by continued removal of the solvent (e.g. evaporation).

  • Soluble - When a substance dissolves in a liquid, it is described as soluble in that liquid.

  • Solvent - A solvent is a liquid into which a solute dissolves.

Common misconception

Pupils sometimes use the terms evaporation and boiling interchangeably, but they are not the same.

Boiling: a liquid substance is heated and gas bubbles form. Evaporation: same, BUT only on the surface of the liquid, no bubbles form and the gas mixes with air.

Contextualise crystallisation by looking at its process and results in nature (Cueva de los Cristales, Mexico) and art (Roger Hiorns, 'Seizure').
Teacher tip

Content guidance

  • Depiction or discussion of sensitive content
  • Risk assessment required - equipment

Supervision

Adult supervision required

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Lesson video

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Starter quiz

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6 Questions

Q1.
Which process happens when a solid can be observed to 'disappear' in a liquid to make a solution?
boiling
condensing
melting
Correct answer: dissolving
evaporating
Q2.
When a process is able to go backwards, or be "undone", it is said to be ...
Correct Answer: reversible, reversible., Reversible., Reversible
Q3.
Match the word to the definition.
Correct Answer:Soluble,When a solid can dissolve in a liquid.

When a solid can dissolve in a liquid.

Correct Answer:Insoluble,When a solid cannot dissolve in a liquid.

When a solid cannot dissolve in a liquid.

Correct Answer:Solution,The mixture formed when a solid dissolves in a liquid.

The mixture formed when a solid dissolves in a liquid.

Correct Answer:Saturated,When no more solid can dissolve.

When no more solid can dissolve.

Q4.
A volume of salt solution containing 0.50 g of salt was placed in a beaker and left for two weeks on the window sill, after which only crystals of salt remained. How much salt would be present?
0.00 g
0.25 g
0.40 g
Correct answer: 0.50 g
Q5.
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?
No change as the sugar would still be dissolved.
No change as temperature does not affect the solubility of the sugar.
Solid sugar would start to form as the water would evaporate.
Correct answer: Solid sugar would start to form as it is less soluble at a lower temperature.
Q6.
When a solution is left to evaporate, the solute left behind can form ...
Correct Answer: crystals, crystal, crystals.

Exit quiz

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6 Questions

Q1.
What is a saturated solution?
A solution that can dissolve more solute.
Correct answer: A solution where no more solute can dissolve.
A solution that has evaporated completely.
A solution mixed with an insoluble solid.
A solution that changes colour with more solute.
Q2.
What happens during crystallisation?
The solute evaporates leaving the solvent.
The solvent dissolves more solute to form crystals.
Correct answer: Solid crystals form by removing the solvent.
The temperature of the solution decreases.
The solvent turns into a solid.
Q3.
What does the term 'soluble' mean?
Changes the colour of a solvent.
Correct answer: Dissolves in a liquid.
Increases the temperature of a solution.
Forms a gas when mixed with a liquid.
Q4.
True or false? If a substance is soluble in one solvent, it is soluble in all solvents.
True
Correct answer: False
Q5.
Which of these are true statements about the differences between boiling and evaporation?
Correct answer: Boiling occurs at the boiling point, evaporation happens below this temperature.
Boiling forms crystals, evaporation does not.
Correct answer: Boiling happens throughout the liquid, evaporation occurs only on the surface.
Evaporation produces bubbles of gas, boiling does not.
Evaporation results in crystal formation, boiling does not.
Q6.
In a crystallisation process, the loss of the leads to crystal formation.
Correct Answer: solvent