Change in pH: practical
Lesson details
Learning outcome
I can investigate the change in pH on adding base to a fixed volume of acid.
Key learning points
- When powdered hydroxide/oxide (base) is added to an acidic solution there is an increase in pH.
- pH changes quickly around the neutralisation point.
- Indicators, such as Universal Indicator paper, can be used to collect quantitative data on pH.
- pH can be plotted on a graph to find the quantity of base required to neutralise an acid.
Keywords
PH - A measure of the hydrogen ion (H⁺) concentration in a solution.
Neutralisation - A chemical reaction between an acid and base to produce a neutral solution of a metal salt and water.
Base - A substance that neutralises an acid to form a salt and water.
Quantitative - Refers to a measurement of quantity. A numerical value.
Common misconception
All added calcium hydroxide dissolves completely, and the pH readings are accurate without consistent mixing.
Calcium hydroxide has low solubility in water, so not all of it dissolves readily. Consistent mixing ensures uniform pH readings. Without proper mixing, pH readings can be inaccurate, leading to incorrect conclusions about the neutralisation point.
Teacher tip
Emphasise consistent mixing and accurate measurements. Encourage pupils to stir thoroughly after each addition of calcium hydroxide for uniformity. Use a pH meter for precision and record data systematically to understand the importance of accuracy in experiments.
Equipment
UI paper, white tiles, dilute HCl, measuring cylinders, beakers, glass rods, top-pan balance, weighing boats, spatulas, calcium hydroxide powder, graph paper, rulers, UI pH scales.
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 happens to the pH when a base is added to an acidic solution?
Q2.What is the purpose of Universal Indicator paper?
Q3.What does plotting pH changes on a graph help determine?
Q4.Why is accurate data collection important?
Q5.What is observed when pH changes around the neutralisation point?
Q6.What does a colour change on the Universal Indicator paper indicate?
Assessment exit quiz
6 Questions
Q1.Match each of the following key terms to the correct definitions.
a measure of hydrogen ion concentration
a reaction between an acid and a base
increases pH when added to an acid
data represented as numerical values
responsible for acidity in a solution
Q2.What happens to the pH of a basic solution when an acid is added?
Q3.What is neutralisation?
Q4.How does pH change near the neutralisation point?
Q5.What can be determined by plotting pH on a graph during neutralisation?
Q6.Which of the following is an example of a base?
To help you plan your 10 combined science lesson on: Change in pH: practical, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your 10 combined science lesson on: Change in pH: practical, 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 combined science lessons from the Making salts unit, dive into the full secondary combined science curriculum, or learn more about lesson planning.