Science experiments for children – Measure the pH with red cabbage. Cut the red cabbage into thin slices, put into a pot, covering it with water, bring to a boil and boil for 30 minutes. Once cooled, strain the liquid: you will get your red cabbage juice, which will be blue-violet.
http://www.funsci.com/
With younger children this juice is the ideal ingredient for making magic potions (just get pipettes or syringe without a needle and a few glasses, various liquids such as lemon juice, vinegar, water and baking soda, beer, liquid soap, Coke, etc. …)
http://www.minieco.co.uk/
The red cabbage juice has the characteristic of changing color in contact with substances that have different pH: you will have a very intense pink with acidic substances and a beautiful green with basic substances. You can get up to yellow.
With older children you can be made of pH indicator paper. It is sufficient to prepare many white cards, immerse them in the juice of red cabbage for 30 minutes, then dry them.
The juice of red cabbage deteriorates fairly quickly, but if you hold the cards in a closed plastic bag will store them for several months.
With these cards you can realize a chromatic scale as that of the maps of Tornasole. Chromatic scales can also be realized by using glass containers or tubes:
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Science experiments for children – Measure the pH with red cabbage
Other links
http://chemistry.about.com/od/
http://www.mr-damon.com/experiments/6svt/ph_cabbage.htm
http://www.soapqueen.com/bath-and-body-tutorials/tips-and-tricks/test-ph-red-cabbage/
http://www.hometrainingtools.com/a/acids-bases-red-cabbage-ph-paper
