Water Education - Water and Health

Testing pH with Purple Cabbage

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Yeah that’s right, there’s a way to indicate pH levels at home with the use of purple cabbage. First, let us briefly go over a little about acidic or alkaline properties. Liquids all around us have either of these properties. For example, apple juice, oranges, coffee and milk are all acidic liquids. Baking soda, soapy water and bleach are all alkaline liquids. Acids have a low pH with anything less than 7 and alkaline solutions have a high pH with anything above a 7. If the solution has an equal amount of acidic and alkaline molecules, pH is considered neutral. The pH of pure water is 7 and the normal range of surface water is between 6.5 and 8.5.

The cabbage contains a natural pH indicator that changes colors according to the acidity of the solution. In this experiment, we will use the juice from red cabbage as a pH indicator to test common household liquids and determine their pH levels. You will mix cabbage juice with different household liquids and see a color change produced by a pigment called flavin in red cabbage. Through this color change, you will be able to successfully identify the approximate pH of the household liquid. pH scale runs from 0.0 to 14.0 and is the measurement of a liquids level of acidity or alkalinity. Please refer to the chart below to match the pH numbers with the color change. Now, let us begin our experiment!

What you will need:

  • A head of red cabbage
  • Coffee Filters
  • A funnel or coffee filter basket
  • Knife
  • Boiling Water
  • Strainer
  • Cups
  • Solutions you wish to test (Baking soda, lemon juice, vinegar, etc.)
  • Pitcher or Beaker
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