For those who are into natural products and DIY (Do-It-Yourself) kind of activities, a simple Science project may just be up your alley. Known as ‘Red Cabbage Chemistry’, this experiment allows one to have his or her own pH indicator. In other words, one can test the acidity or alkalinity of just about any liquid or substance simply by using the juice of a vegetable as accessible as red cabbage. But be warned – you might want to peg your nose as the cabbage juice emits a foul smell!
A group of Year 10 Chemistry students of R.E.A.L International School (RIS), Suria Campus, Cheras discovered this to their amazement when they turned red cabbage into an acid and base indicator. This easy-to-do procedure involved peeling the cabbage leaves, blending them, straining the liquid to separate the juice from the cabbage chunks, and finally using the juice as the indicator.
The students came prepared with 18 different household solutions to test on. By adding a little of each solution into different glass containers (each filled with red cabbage juice), the juice changed colours ranging from red and pink to purple and bluish green. These colours indicate how acidic or alkaline a particular household solution is.
So, how does this happen? Red cabbage contains a water-soluble pigment called ‘flavin’ (a type of anthocyanin) that changes colour when mixed with an acid or base. This pigment molecule is also found in apple skins, plums, poppies, cornflowers, and grapes. Very acidic solutions (with a pH level of less than 7) will turn the juice red, neutral solutions would result in a purplish colour, while basic or alkaline solutions (with a pH level of more than 7) would appear greenish-yellow.
The RIS students were thrilled with their findings and definitely learnt more about the common, everyday items that they use at home. This practical learning approach is synonymous with R.E.A.L Schools’ active learning philosophy, in which students learn best by seeking answers on their own (or by doing), and asking ‘WHY’ to everything.