|blue litmus paper changes to red|
If a blue litmus paper does not change its colour after touching a substance, it can be means two thing:
i) The substance could be neutral
ii) The substance could be alkaline.
As such, we need to test the substance with a red litmus paper. If the red litmus paper does not change its colour, then the substance is neutral.
- substances with a pH of less than 7 are acids
- the stronger the acid, the lower the pH number
- acids turn blue litmus paper red
- they turn universal indicator red if they are strong, and orange or yellow if they are weak.