A fraction is a component of a mixture that has been separated by fractional distillation.

Fractional distillation is a method used to separate miscible fluids (liquids or gases) with different boiling points into individual components (fractions).

Fluids that dissolve in another fluid are described as miscible in that fluid.

The temperature at which a substance changes between a liquid state and a gas state is known as its boiling point.

A fractionating column is a piece of apparatus within which a temperature gradient develops.  It is used during fractional distillation.

Distillation: fractional distillation

Combined science

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.

Separating substances

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liquids and/or gases which can dissolve in each other

{{}} are produced by fractional distillation. They may be pure, i.e. contain one component, or a mixture containing multiple components with similar boiling points.

to mix multiple fluids together with different boiling points

to separate multiple fluids with different boiling points

What is the purpose of fractional distillation?

separate two miscible liquids with very different boiling points.

to separate multiple miscible fluids with a range of boiling points.

to create a temperature gradient to separate fluids into fractions.

pure substances, or mixtures with similar boiling points.

Match the following statements to make complete sentences related to distillation:

A mixture of liquid fractions; X (b.p. 40 - 100°C), Y (b.p. 120 - 160°C) and Z (b.p. 180 - 200°C) was heated quickly to 150°C. What would be found in the distillate?

miscible fluid mixture is heated and starts to boil forming a vapour

the vapour passes up the fractionating column, heating the bottom

most substances cool as they rise up the column and drip back down

lower boiling point substances pass as gases into the condenser

these gases are cooled in the condenser back into the liquid state

the condensed liquid is collected as the distillate fraction

Match the letter with the correct statement concerning the steps occurring during fractional distillation.

A mixture is a substance which is made up from more than one element and/or compound which are ... 

{{}} is the process by which a gas is cooled into a liquid. 

of more than one element and/or compound.

Match the following statements to make complete sentences about pure substances and mixtures.

The component with lowest boiling point boils.

Simple distillation can be used to separate solutions. Order the following processes that occur during simple distillation.

In the diagram below, give the letters in order for where forces between the particles are overcome or where they are being reformed.

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Distillation: fractional distillation

Lesson outcome

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