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How can you use a cabbage to tell if something is
Try this and see:
What you need:
- Red cabbage
- Chopping board
- Large bowl
- Wooden spoon
- Measuring jug
- Clear plastic cups
- Kitchen items to test. You can use whatever you like, but good
items to start with are lemon juice, ketchup, soap, vinegar, fizzy
drinks and bicarbonate of soda.
- Take half a cabbage.
- Chop the cabbage into small pieces.
- Put the cabbage pieces in the bowl and add about 250ml of
- Mash the cabbage up using a wooden spoon.
- When you see a bright purple liquid in the bottom of the bowl,
sieve the liquid into a measuring jug.
- Pour about 1cm of liquid into several different cups - each cup
will be used to test a different kitchen item.
- Leave one of the cups as your 'control'. This will remind you
what the original colour was and you can compare the colour changes
- Now you can test your kitchen items! Start with something that
you think is acidic - how about vinegar or lemon juice?
- Then try something basic - also known as alkaline - try
bicarbonate of soda.
What else can you test in your kitchen?
What colours did you see?
When the cabbage juice goes red, it means the kitchen item is
acidic. When the cabbage juice goes blue, it means
the substance is alkaline. If the colour
doesn't change it means the substance is
Which item was the most acidic? Which item was the most
alkaline? Were any of the items neutral?
Why does the cabbage change colour?
Red cabbage contains a pigment called flavin,
which gives the cabbage its colour.
Acids and bases affect the number of hydrogen ions in a
solution. There are more hydrogen ions in an acidic solution and
fewer hydrogen ions in a basic - alkaline - solution. Bases produce
hydroxide ions, which neutralise the hydrogen ions. The ratio of
hydrogen ions to hydroxide ions determines how acidic a solution
The colour of flavin - the pigment in cabbage - depends on the
ratio of hydrogen ions to hydroxide ions. At high concentrations of
hydrogen ions, flavin is a red-pink colour. At low concentrations
of hydrogen ions, the flavin pigment breaks up and turns a blueish