New
New
Year 10
AQA
Higher

Water sample analysis: distillation

I can use distillation to purify water samples and analyse the distillate to test its purity.

New
New
Year 10
AQA
Higher

Water sample analysis: distillation

I can use distillation to purify water samples and analyse the distillate to test its purity.

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Lesson details

Key learning points

  1. Distillation can be used to purify water samples.
  2. Boiling point data can be analysed to assess the purity of water samples.
  3. The more impurities present in a sample, the larger the temperature range over which the water will boil.
  4. Pure water boils at 100°C.

Keywords

  • Impurity - A chemical that is found in a material in very small amounts, but can change the material's properties.

  • Pure - A single element or compound that is not mixed with any other substance.

  • Sample - A smaller portion of a larger quantity of a substance.

  • Distillation - A separation technique that uses boiling and condensation to remove and isolate a liquid component of a mixture.

  • Distillate - The liquid that is condensed from the gas state during distillation.

Common misconception

All water samples boil at 100°C.

If a water sample is impure, the boiling point of water increases. The greater the amount of impurities in a water sample, the larger the temperature range over which it boils.

Ensure the end of the delivery tube is kept out of the distillate to avoid 'suck back' and loss of distillate. Include ice in the 'beaker water bath' to improve condensation. Consider extending the practical by including rain water / mineral water samples.
Teacher tip

Equipment

Quickfit apparatus (or conical flask, test tube, delivery tube, ice, beaker, tripod, gauze), thermometer, Bunsen Burner, heatproof mat, sample of 'sea water'.

Content guidance

  • 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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6 Questions

Q1.
What is the main principle behind the separation of mixtures in distillation?
Correct answer: Differences in boiling points
Differences in melting points
Differences in solubility
Q2.
Why can't filtration separate soluble substances from liquids?
Filtration is only for gases
Filtration is too slow
Correct answer: Soluble substances pass through the filter
Q3.
What does a change in the boiling point of a liquid indicate?
Change in temperature
Improper measurement
Correct answer: Presence of impurities
Q4.
What does filtration separate?
Gases from liquids
Correct answer: Insoluble substances from liquids
Soluble substances
Q5.
What is condensation?
Correct answer: The change of state from gas to liquid
The change of state from liquid to gas
The change of state from solid to gas
Q6.
How can boiling point data be used?
Correct answer: To assess the purity of water samples
To measure the volume of liquids
To separate insoluble substances

6 Questions

Q1.
What process would produce pure water from potable water containing dissolved solids?
Filtration
Evaporation
Correct answer: Distillation
Chlorination
Q2.
What does a boiling point range of 98°C to 102°C suggest about the water sample?
Correct answer: The sample contains impurities
The sample is improperly measured
The sample is pure
Q3.
What is indicated by a boiling point of 100°C?
Impure water
Incorrect measurement
Correct answer: Pure water
Q4.
What is the purpose of the condenser in the distillation apparatus?
To heat the mixture
To heat the vapour
Correct answer: To cool and condense the vapour back into a liquid
Q5.
Why is it important to collect the distillate in a clean container?
Correct answer: To avoid contamination of the distillate
To ensure the distillate evaporates again
To measure the volume accurately
Q6.
How can you determine the effectiveness of distillation from boiling point data?
Check the colour of the distillate
Correct answer: Compare the boiling points before and after distillation
Measure the volume of the distillate