Water sample analysis: pH
Lesson details
Learning outcome
I can the describe how to test the pH of different water samples and suggest why they may differ in terms of dissolved substances.
Key learning points
- The pH of water samples can be determined using appropriate methods and/or instruments e.g pH meter.
- pH data can be analysed to assess if water contains impurities.
- Different substances dissolve in different types of water.
- The substances that dissolve in different waters can affect the water's acidity or alkalinity (i.e. its pH).
- 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.
Teacher tip
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.
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
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.What is the pH range of strong acids?
Q2.What is the pH of pure water?
Q3.What is the pH range of weak bases (alkalines)?
Q4.Which of the following is a common laboratory apparatus used to measure pH accurately?
Q5.What type of water might contain dissolved chlorine, affecting its pH?
Q6.What does it mean if a substance has dissolved in water?
Assessment exit quiz
6 Questions
Q1.Which method is used to measure pH and requires calibration?
Q2.What does a pH of 7 in water indicate?
Q3.Why is it important to measure the pH of water samples?
Q4.Which of the following substances dissolves in both groundwater and seawater?
Q5.What can cause the pH of rainwater to be slightly acidic?
Q6.What does a low pH value in water indicate?
To help you plan your 10 chemistry lesson on: Water sample analysis: pH, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your 10 chemistry lesson on: Water sample analysis: pH, download all teaching resources for free and adapt to suit your pupils' needs.
The starter quiz will activate and check your pupils' prior knowledge, with versions available both with and without answers in PDF format.
We use learning cycles to break down learning into key concepts or ideas linked to the learning outcome. Each learning cycle features explanations with checks for understanding and practice tasks with feedback. All of this is found in our slide decks, ready for you to download and edit. The practice tasks are also available as printable worksheets and some lessons have additional materials with extra material you might need for teaching the lesson.
The assessment exit quiz will test your pupils' understanding of the key learning points.
Our video is a tool for planning, showing how other teachers might teach the lesson, offering helpful tips, modelled explanations and inspiration for your own delivery in the classroom. Plus, you can set it as homework or revision for pupils and keep their learning on track by sharing an online pupil version of this lesson.
Explore more key stage 4 chemistry lessons from the Separating substances unit, dive into the full secondary chemistry curriculum, or learn more about lesson planning.