Lesson 1 Making red cabbage indicator

Cards (16)

  • An acid has a pH less than 7
  • An alkali has a pH over 7
  • A pH of 7 is neutral
  • Method for obtaining red cabbage indicator
     
    1. Tear the red cabbage leaf into small pieces
    2. Put the red cabbage into the mortar with some sand and grind it with a pestle
    3. Put the red cabbage into a beaker and about 100cm cubed of water and heat
    4. Filter the mixture and collect the filtrate. Save it for testing
    5. Put a small amount of a chemical in a clean test tube, Add a few drops of the red cabbage indicator
  • What colour does the red cabbage indicator become after testing Sodium hydroxide (NaOH)?
    yellow (pH 14)
  • What colour does the red cabbage indicator become after testing ammonia (NH3)
    green (pH 11-12)
  • What colour does the red cabbage indicator become after testing tap water (H2O)
    blue (pH 7)
  • What colour does the red cabbage indicator become after testing Ethanoic acid (CH3COOH)
    pink (pH 3)
  • What colour does the red cabbage indicator become after testing Hydrochloric acid (HCL)
    red (pH 1)
  • What colour does the red cabbage indicator become after testing Sodium carbonate (NA2CO3)
    green (pH 10-11 )
  • What is meant by the word extraction?
    The action of removing something
  • Why was the crushed cabbage heated with water?
    The indicator is soluble in water and dissolves better in hot water.
  • Name the method used to separate the leaves from the solution of the indicator. 
    Filtration
  • What colour would you expect the red cabbage indicator to become in aqueous potassium hydroxide which has a pH of 13? 
    Yellow/green
  • What colour would you expect the red cabbage indicator to become in aqueous nitric acid which has a pH of 1? 
    red
  • If a solution turned the red cabbage indicator yellow, what effect would it have on Universal Indicator?
    It would turn purple.