Activity

Fruit and vegetable indicator dyes

Summary
Crush blue, red and purple-coloured fruits and vegetables. Add acid or base to find which ones have pigments that change colour with acid-base.
Science content
Biology: Features, Adaptations of Living Things (K, 1, 3, 7)
Chemistry: Chemical Changes (2, 7)
Materials
  • red, blue and purple fruits and vegetables. Red cabbage and radish skin work really well. blueberries and grapes are OK.
  • sharp knife
  • mortar and pestle
  • water
  • vinegar in a dropper bottle
  • 1 tspn baking soda in 1 cup water, in a dropper bottle
  • paint tray or white ice cube tray
Procedure

Peel/chop fruits and veggies, to collect small pieces of coloured material.
Add to the mortar and pestle with very little water and crush to make a concentrated coloured liquid.
Pour a little of the coloured liquid into wells of the tray.
Add drops of acid and base to change the colour (or not - results are very variable).

Notes

isas tried apple, peach, radish skins, blueberry skins, red onion.
Seymour tried red chard stems and beetroot. Red chard slightly changed colour, beetroot did not.

Grades taught
Gr 4
Gr 5
Gr 6
Gr 7
Teaching site
ingridscience afterschool
Seymour Elementary