Density is a measurement of mass per unit volume; how tightly packed a substance's particles are in a particular space.

The boiling point of a substance is the temperature at which it changes from a liquid state to a gas state.

Liquids that are not soluble in another liquid are described as immiscible in that liquid.

Liquids that dissolve in another liquid are described as miscible in that liquid.

Decanting is a process of pouring off the top layer in a mixture of immiscible liquids, or a liquid and insoluble solid.

Separating liquids

Science

Separating an insoluble solid from a liquid

Separating a soluble solid from a liquid

Separating pure salt from dirty rock salt

Simple distillation

Distillation: practical

Chromatography

In the Understanding Chemical Reactions unit, pupils will build on their understanding of physical changes to learn how atoms rearrange to form new substances during chemical reactions (chemical changes).

In the key stage 2 Properties, changes and separating materials unit, pupils learnt about mixtures, including solutions, and separation techniques including filtering and evaporation.

This unit covers techniques for separating mixtures, including filtration, evaporation, distillation, and chromatography, as well as identifying pure substances. Conduct experiments safely, record observations, evaluate methods, and suggest improvements.

Separation techniques

Physical activity and equipment requiring safe use

What is the main purpose of using a 'separating funnel' in the lab?

True or false? Decanting is effective for separating liquids with similar densities. 

If two liquids can mix completely together to form one layer, they are said to be ...

True or false? A separating funnel can be used to separate two liquids that are miscible.

Liquids that are not soluble in another liquid.

Process of pouring off the top layer in a mixture of liquids

A mixture comprised of a solute dissolved in a solvent.

Match the keywords with their correct definition.

Heating, as the liquids have different boiling points.

Which of the following techniques should be used to separate miscible liquids?

True or false? Solids that do not dissolve in a liquid are called insoluble.

What is the process of changing a liquid into a vapour (gas) called?

True or false? When a solution is heated, the solvent evaporates more slowly. 

Which properties below would be helpful in separating a mixture of substances?

True or false? All liquids have the same boiling point of 100℃.

In a mixture of two liquids with very different densities, the less dense liquid will ...

Separating liquids

Lesson outcome

Content guidance