Indicators and pH scale

• Indicator

  Substance that changes colour when added to acidic or alkaline solutions
• Universal indicator

  Indicator most commonly used in the laboratory
• pH scale

  Scale used to measure acidity and alkalinity
• pH scale categories

  • Acidic
  • Alkaline
  • Neutral
• Solutions with pH less than 7 are acidic
• Solutions with pH of 7 are neutral
• Solutions with pH greater than 7 are alkaline
• Universal indicator

  Mixture of a variety of other indicators, can be used to measure approximate pH of a solution
• A more accurate pH value can be obtained using a pH probe
• When an acid is neutralised, it forms a salt