New
New
Year 10
AQA
Higher

Water sample analysis: pH

I can the describe how to test the pH of different water samples and suggest why they may differ in terms of dissolved substances.

New
New
Year 10
AQA
Higher

Water sample analysis: pH

I can the describe how to test the pH of different water samples and suggest why they may differ in terms of dissolved substances.

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Lesson details

Key learning points

  1. The pH of water samples can be determined using appropriate methods and/or instruments e.g pH meter.
  2. pH data can be analysed to assess if water contains impurities.
  3. Different substances dissolve in different types of water.
  4. The substances that dissolve in different waters can affect the water's acidity or alkalinity (i.e. its pH).
  5. Pure water is necessary for laboratory tests; it must be neutral (i.e. pH 7).

Keywords

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

  • Dissolve - When a substance's particles separate and spread throughout the particles of a solvent resulting in it no longer being seen.

  • PH - A number that shows the alkalinity or acidity of a solution.

Common misconception

All water samples are neutral (i.e. pH of 7).

The acidity / alkalinity of water samples is affected by the dissolved substances in each sample.

Extend the practical to include different mineral waters; using a pH meter, compare the 'ingredients' list (mineral content) of each and see if these impact the pH of the waters.
Teacher tip

Equipment

Samples of 'pure', 'sea', 'rain' and 'ground' water; dropping pipettes; universal indicator paper and reference chart.

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 pH range of strong acids?
Correct answer: 0 to 3
7 to 10
10.1 to 14
Q2.
What is the pH of pure water?
0
Correct answer: 7
14
Q3.
What is the pH range of weak bases (alkalines)?
0 to 6.9
Correct answer: 7.1 to 10
10.1 to 14
Q4.
Which of the following is a common laboratory apparatus used to measure pH accurately?
Beaker
Bunsen burner
Universal indicator
Correct answer: pH meter
Q5.
What type of water might contain dissolved chlorine, affecting its pH?
Distilled water
Pure water
Correct answer: Tap water
Q6.
What does it mean if a substance has dissolved in water?
It changes colour.
Correct answer: Its particles separate and spread throughout the water.
It turns into a gas.

6 Questions

Q1.
Which method is used to measure pH and requires calibration?
Correct answer: pH meter
pH paper
Universal indicator solution
Q2.
What does a pH of 7 in water indicate?
The water is acidic.
The water is alkaline.
Correct answer: The water is neutral.
Q3.
Why is it important to measure the pH of water samples?
Correct answer: To assess water quality and identify impurities.
To change the water's colour.
To make the water taste better.
Q4.
Which of the following substances dissolves in both groundwater and seawater?
Sand
Correct answer: Salts
Oil
Correct answer: Minerals
Q5.
What can cause the pH of rainwater to be slightly acidic?
Correct answer: Dissolved gases
Dissolved salt
Pure water
Q6.
What does a low pH value in water indicate?
Correct answer: The presence of acidic substances.
The water is alkaline.
The water is pure.