Lesson Plan

• Describe the relationship between hydrogen‑ion concentration, pH and the colour change on universal indicator paper.
• Explain how to identify acidic, neutral or alkaline solutions using the colour‑pH chart.
• Apply the testing procedure to compare three solutions and record estimated pH values.
• Interpret the observed colours to classify the relative strength of each solution.

• Universal indicator paper strips
• Three clean test tubes (labelled Acid, Neutral, Base)
• Prepared acid, neutral (water) and base solutions
• Colour‑pH reference chart
• Pipettes or droppers
• Safety goggles and lab aprons
• Lab notebooks / worksheets

Begin with a quick question: “What everyday products show us they are acidic or alkaline?” Connect this to prior knowledge of the pH scale. Explain that today’s success criteria are to predict solution type from colour and to record accurate pH estimates.

1. Do‑now (5'): Short quiz on pH values and colour associations.
2. Mini‑lecture (10'): Review hydrogen‑ion concentration, the logarithmic pH formula, and the universal indicator colour chart.
3. Teacher demonstration (10'): Show the step‑by‑step procedure with three labelled test tubes.
4. Hands‑on activity (15'): Students label their own tubes, dip fresh indicator strips, observe colours, and record results.
5. Guided analysis (10'): Match observed colours to the chart, estimate pH, and classify each solution.
6. Check for understanding (5'): Exit ticket – write one sentence explaining how colour indicates acidity or alkalinity.

Recap the link between colour, pH and hydrogen‑ion concentration, highlighting common pitfalls such as re‑using strips or inconsistent lighting. Collect exit tickets and assign a worksheet where students calculate pH from given [H⁺] values and predict indicator colours for new solutions.