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

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

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

A solvent is a liquid into which a solute dissolves.

Crystallisation

Combined science

Separating mixtures (including formulations)

Solutions

Filtration

Chromatography: paper

Interpreting chromatograms

Chromatography: separating a mixture of inks

Distillation: simple distillation

Distillation: separating a mixture of inks

Distillation: fractional distillation

Potable water

Wastewater treatment

Water sample analysis: pH

Water sample analysis: dissolved solids

Water sample analysis: distillation

In the Making Salts unit, pupils will build on their understanding of separation techniques to learn about the process of making salts and writing balanced chemical equations.

In the Separation Techniques unit, pupils learned about various methods for separating mixtures, including filtration, evaporation, distillation, and chromatography.

This unit explores purification techniques, including filtration, crystallisation, and distillation. It explains formulations, uses chromatographic methods to identify pure and impure substances, and interprets chromatograms with Rf values. The emphasis is on accurate measurements.

Separating substances

Depiction or discussion of sensitive content

Physical activity and equipment requiring safe use

A solution that can dissolve more solute.

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.

The solute evaporates leaving the solvent.

The solvent dissolves more solute to form crystals.

Solid crystals form by removing the solvent.

The temperature of the solution decreases.

True or false? If a substance is soluble in one solvent, it is soluble in all solvents.

Boiling occurs at the boiling point, evaporation happens below this temperature.

Boiling forms crystals, evaporation does not.

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.

Which of these are true statements about the differences between boiling and evaporation?

In a crystallisation process, the loss of the {{}} leads to crystal formation.

Which process happens when a solid can be observed to 'disappear' in a liquid to make a solution?

When a process is able to go backwards, or be "undone", it is said to be ...

When a solid cannot dissolve in a liquid.

The mixture formed when a solid dissolves in a liquid.

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?

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.

Solid sugar would start to form as it is less soluble at a lower temperature.

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?

When a solution is left to evaporate, the solute left behind can form ...

Crystallisation

Lesson outcome

Content guidance