KS3 Red Cabbage Indicator lesson: editable PowerPoint with a natural indicator practical, pH, acids and alkalis, evaluation tasks and answers.

Can a vegetable identify a mystery liquid? Help students make and use red cabbage indicator, interpret colour changes and evaluate how confidently their results identify acidic, neutral and alkaline solutions.

This 34-slide editable PowerPoint is designed for mixed-ability KS3 classes, particularly Year 7, within the Exploring Science 7E: Acids and Alkalis topic. Includes suggested 60-minute pacing.

What’s included?

• Four-question retrieval starter with answers, revisiting hazards, safe working and indicators.
• Mystery-liquid hook to encourage prediction and discussion.
• pH scale recap and explanations of indicators.
• Litmus prediction questions with answers.
• The science of red cabbage pigments, introducing anthocyanins and their response to pH.
• Practical instructions for extracting the indicator and testing acidic, neutral and alkaline samples.
• Equipment and safety guidance, with teacher handling of hot water.
• Results-table template and expected observations.
• A mini-whiteboard hinge check before practical work.
• Misconception task, distinguishing an indicator colour change from an unsupported conclusion about the sample.
• Comparison of litmus, methyl orange and phenolphthalein, with answers.
• Claim–evidence–reasoning evaluation task, supported by a writing frame and model response.
• Unknown-sample challenge, asking students to classify a liquid and suggest a second test.
• Six marks of exam-style questions with a mark scheme.
• Extension discussion exploring why groups might record different colours for the same sample.
• Careers links, exit questions with answers, and teacher/technician preparation notes.

Support and challenge

Short instructions, partner discussion and sentence starters support learners who need guidance. Extension tasks ask students to explain limitations, improve their methods and compare colour tests with pH probes.

Students learn that cabbage indicator has its own colour range: acids typically produce pink/red, neutral samples purple/violet, and alkalis blue/green. Exact shades depend on the sample and extract.

Classroom use

Suitable after an introductory acids-and-alkalis lesson. Develops prediction, observation, fair testing and evidence-based evaluation, including why colour alone cannot reliably identify an exact pH.

Format: one editable PowerPoint. Activities, recording table, model responses and assessment answers are included within the slides.

Equipment: red cabbage, water, beakers, sieve/filter, pipettes, spotting tiles, goggles and teacher-approved test solutions such as vinegar or citric acid, water and bicarbonate solution. Follow school practical guidance and risk assessments.