Plant Dyes - Colour Magic!
Like cars, plants have
The dye in the petals of some types of
flower can change colour showing, or indicating, how healthy the plant
We can crush the petals to get the
dye out and use this dye to show (indicate) if a liquid is an acid or
- Grind a cup of darkly coloured petals (violet pansies
are good) in a shallow dish with a little water. The back of a spoon
can be used.
- Pour the dye/juice into a clean jar leaving the
lumpy bits behind in the dish
- Store the dye in the fridge if you want to use it for
a few days.
||Try any darkly coloured petals or
juice from vegetables and fruit. Beetroot juice, red cabbage,
blueberrires and even a strong cup of tea works. Don't get the
indicator dye on your clothes or furniture!
Take careful note of the colour of
your indicator. This is the colour when it is neutral
Pour a little of your indicator dye
into glass and add a few drops of vinegar. Did it change colour? If so,
this is the colour for something that is an acid
Do the same again with another clean
glass and add a little automatic dishwashing powder. Did it change
colour? If so, this is the colour for something that is an alkali
Now lets have some more fun!
PREDICT: Ask your
students "What will happen when I add a few drops of lemon juice to a
fresh sample of my plant indicator? Will it change to show it is an
acid, an alkali or is it neutral?"
OBSERVE: Watch what
happens when your test liquid is added and well mixed.
EXPLAIN: What does this
show us? (seniors might like to consider carrying out a titration to
determine the Vitamin C content of lemon juice)
Try water, milk, lemon juice, Coca
Cola, and rainwater. You can write down what you found out and try
other liquids - but check with an adult first if its OK! Always wash
out any kitchen glassware properly afterwards.
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