Testing pH Indicators

This experiment investigates how different pH indicators change color across the acidic, neutral, and basic ranges.

1. Prepare a series of solutions with different pH values, ranging from strongly acidic to strongly basic.
2. Select several pH indicators to test. Examples include litmus, universal indicator, phenolphthalein, methyl orange, bromothymol blue, and natural extracts such as red cabbage juice.
3. Place small samples of each pH solution into test tubes or wells in a spotting tile.
4. Add a few drops of an indicator to each solution and record the color observed.
5. Repeat the process with the other indicators to compare results.
6. Summarize findings in a table showing pH values and corresponding indicator colors.

Chemistry Lesson | pH Indicator | Acid & Base Experiment | Science for Kids - Big Bang Academy Kids:

• Test natural indicators from foods such as beetroot, turmeric, blueberries, or hibiscus tea.
• Compare the sensitivity of synthetic versus natural indicators across different pH ranges.
• Use a digital pH probe to measure exact pH values and compare them to the indicator results.

• Wear safety goggles and gloves to protect against spills.
• Handle acids and bases with care; even dilute solutions can irritate skin and eyes.
• Avoid tasting or touching any chemicals or indicator solutions.
• Dispose of all solutions safely, flushing dilute samples down the sink with plenty of water.

• Why do different indicators show different colors at the same pH? (Because each indicator has its own unique transition range where its molecular structure changes.)
• How could using multiple indicators improve the accuracy of identifying a solution’s pH? (By covering overlapping pH ranges, giving a clearer estimate.)
• Why might natural indicators be less precise than laboratory-prepared indicators? (Natural extracts often contain mixtures of compounds, making the color changes less sharp.)
• What practical uses are there for pH indicators outside the classroom? (They are used in soil testing, swimming pool maintenance, medical diagnostics, and industrial processes.)