Meassuring pH using red cabbage as indicator
In this little eksperiment we show how to use red cabbage as an indicator for change sin pH
Materials:
Red cabbage
water
a strong acid
a strong alcaline
heat proof glass
some test tubes
a heat source
safety glasses, lab coat and gloves
Method.
Cut the red cabbage in slices and boil it in about 250 ml of water for 5 minutes
let it cool and then gently pour about 50 ml into a new beaker or a test tube
add some cold water
Observe the colour
Use safety glasses, gloves and lab coat when using corosive agents.
Add about 1 ml of an acid.
Note the colour change
Add about 2 ml of an alkaline
Note colour change
You can also add more acid to change the colour back again
What happens?
Red cabbage juice changes color when you add acid or alkaline because it contains a pigment called anthocyanin. Anthocyanins are pH-sensitive and can act as natural indicators.
When pH is low, the colour is red
When pH is high, the colour will change to green and later to yellow if pH is really high
How to expand the experiment:
Try testing with other indicators (pH paper, universal indicator or other indicators)
Can we use a more accurate way of adding small amounts of acid or alkaline?
What will be a good indicator for sea water and why?
Find all the material here
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