methods of separating + purifying substances ×× distillation

Question 1

Describe how to carry out, and explain what happens in, simple distillation

Answer 1

Simple distillation is a method for separating the solvent from a solution. When the solution is heated, the water evaporates. It is then cooled and condensed into a separate container. The salt does not evaporate and so it stays behind

Question 2

Distinguish between simple distillation and fractional distillation.

Answer 2

Fractional distillation is the process for separating the mixture into its parts. Simple distillation is the process in which two liquids with a different boiling point can be separated. Fractional distillation can separate the mixture, which has boiling points close to each other.

Question 3

Identify when fractional distillation should be used to separate a mixture

Answer 3

Fractional distillation is a method for separating a liquid from a mixture of two or more liquids. … This method works because the liquids in the mixture have different boiling points. When the mixture is heated, one liquid evaporates before the other.

Question 4

Describe how to carry out fractional distillation

Answer 4

Fractional distillation separates a mixture into a number of different parts, called fractions. A tall fractionating column is fitted above the mixture, with several condensers coming off at different heights. The column is hot at the bottom and cool at the top.

Question 5

Explain how the products of fractional distillation are linked to the boiling points of the components

Answer 5

Fractional distillation works because the different liquids have different boiling points. When the mixture is heated: vapours rise through a column which is hot at the bottom, and cold at the top. vapours condense when they reach a part of the column that is below the temperature of their boiling point.

Question 6

Explain what precautions are needed to reduce risk in a distillation experiment.

Answer 6

Possible precautions include:

• using less hazardous substances.
• wearing eye protection, protective gloves or other protective clothing.
• choosing different apparatus or a different method.