Lesson 1 Making red cabbage indicator

• 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.