Cut the blue papers into small squares. If you add a little bit of vinegar instead of the water, you will end up with red litmus. Now you can go around the house testing things to see if they are acids or alkalis. If you put a piece of blue litmus paper into an acid it will turn red. If you put a piece of red litmus paper into an alkali it will turn blue.
Indicators change colour at different pH values.
Litmus changes at pH 7 but Phenolphthalein changes from pink to colourless at pH 9. Red Yellow Bromophenol Blue 4.0 Yellow Blue Do NOT try to memorise this table. You have probably used Universal Indicator Papers or Universal Indicator Solution. These have a mixture of indicators so that they have a whole range of colours. I hope that you will be able to remember most of the facts on this page, but you must memorise the definition of indicators.