Acids, Bases and Indicators: Introduction

40 lessons, pages 361–400.

  1. Acids in Everyday Life — Sour tastes, vinegar, citrus fruits and other familiar acids
  2. Bases and Alkalis Around Us — Soap, baking soda, antacids and bitter, slippery substances
  3. Acids, Bases and Neutral Substances — Sorting everyday materials into three groups
  4. Why We Never Taste or Touch to Test — Safe ways to identify acids and bases
  5. What Is an Indicator? — Substances that change colour with acids and bases
  6. Litmus: Origin and Forms — Lichen dye, litmus solution and litmus paper
  7. Using Blue and Red Litmus Paper — Reading colour changes to classify a solution
  8. Interpreting Litmus Results — Why a neutral solution leaves both papers unchanged
  9. Limits of Litmus — Litmus shows acid or base but not how strong
  10. Natural Indicators: An Overview — Plant pigments that respond to acids and bases
  11. Red Cabbage Indicator — Anthocyanins and a rainbow of colours
  12. Turmeric as an Indicator — Yellow in acids, reddish-brown in bases
  13. China Rose and Flower Petal Indicators — Hibiscus and other petals as colour-change tests
  14. Beetroot, Tea and Berry Indicators — Kitchen pigments that shift colour
  15. Why Plant Pigments Change Colour — How molecular structure changes with acidity
  16. Olfactory Indicators — Onion, vanilla and clove oil: smell-based detection
  17. Synthetic Indicators: Phenolphthalein — Colourless in acid, pink in alkali
  18. Synthetic Indicators: Methyl Orange — Red in acid, yellow in alkali
  19. Comparing Natural and Synthetic Indicators — Sharpness, reliability, cost and availability
  20. Universal Indicator and Its Colour Chart — A mixture of indicators giving many colours
  21. Introducing the pH Scale — Numbers from 0 to 14 describing acidity
  22. Strongly and Weakly Acidic Substances — Placing everyday substances on the pH scale
  23. What Makes a Substance Acidic? — Hydrogen ions in water, introduced simply
  24. What Makes a Substance Alkaline? — Hydroxide ions and soluble bases
  25. Common Laboratory Acids and Bases — Names, formulas and hazard symbols
  26. Handling Acids and Alkalis Safely — Corrosive and irritant hazards, dilution and eye protection
  27. Neutralisation: An Introduction — Acids and bases cancelling each other's properties
  28. Watching Neutralisation with an Indicator — Following the colour change to the neutral point
  29. Products of Neutralisation: Salt and Water — The general word equation
  30. Word Equations for Neutralisation — Naming the salt from the acid and the base
  31. Neutralisation Releases Heat — An exothermic change detected by temperature rise
  32. Neutralisation in the Body: Antacids — Treating excess stomach acid
  33. Insect Stings and Nettle Stings — Soothing stings using neutralisation ideas
  34. Neutralisation and Soil — Liming acidic soils and treating alkaline soils
  35. Tooth Decay and Toothpaste — Mouth acids, enamel and alkaline toothpaste
  36. Treating Factory Waste and Acid Rain — Neutralising effluents and acidified lakes
  37. Acids and Bases as Chemical Changes — Linking neutralisation to signs of chemical change
  38. Designing an Indicator Investigation — Fair tests, variables and recording colour results
  39. Common Mistakes with Acids, Bases and Indicators — Correcting frequent misunderstandings
  40. Acids, Bases and Indicators: Unit Review — Indicators, litmus, pH and neutralisation drawn together