Discover how an everyday spice with unusual properties can help you explore science with your children at home. Commonly used in Asian and Middle-Eastern cuisine, turmeric is also one of a number of naturally occurring substances that can act as an indicator, changing colour in response to acidity conditions. Learn how to easily make your own indicator paper from turmeric and use it to test acidic and basic (alkaline) foods and other household substances.
- Skill level:
Things you need
- Turmeric powder
- Methylated spirits (denatured alcohol)
- Plastic cups
- Toilet paper
- Disposable plates
Mix together about two heaped teaspoons of turmeric powder and about three centimetres depth methylated spirits in a disposable plastic cup. Stir the mixture well, and allow the powder to settle. The liquid should now be coloured, and it is this liquid that can act as an indicator.
Place a sheet of toilet paper on a disposable plate and carefully pour the yellow indicator liquid onto the toilet paper. You only need to add enough liquid to moisten the paper. Allow the paper to dry.
Cut the dyed toilet paper into strips. These will act as your indicator paper strips and can be used to test a variety of household acids and bases.
Make a basic or alkaline solution by mixing a teaspoon of bicarbonate of soda with a little water. Determine what colour the paper turns in the presence of an alkali by placing a dried strip of the paper on a paper plate and adding a drop of the bicarbonate of soda mixture.
Add a few drops of lemon juice to the same strip of paper to reverse the colour change. Turmeric indicator turns dark red in the presence of an alkali, but remains yellow in the presence of an acidic or neutral solution.
Use further strips of the indicator to look for other household substances that are alkaline. Any alkaline substance turns the paper red. Acidic substances will not change the colour of the paper, but can be used to reverse the colour change of a strip that has already been used to test for an alkali.
Tips and warnings
- Try making indicators using other substances to test for acids. Red cabbage water is a good example of a substance which changes colour in both acidic and alkaline conditions.
- Methylated spirits is a poisonous substance and should be handled with care. Do not use food preparation utensils or surfaces for this experiment. Turmeric can stain and any spills should be washed immediately.
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