|Red litmus paper changes to blue|
If a red litmus paper does not change its colour after touching a substance, it can mean two things:
i) The substances could be neutral.
ii) The substances could be acidic.
As such, we need to test the substances with a blue litmus paper. If the blue litmus paper does not change its colour, then the substances is neutral.
- Bases that dissolve in water are called alkalis.
- Copper oxide is not an alkali because it does not dissolve in water, but sodium hydroxideis an alkali because it does dissolve in water.
- Alkaline solutions have a pH of more than 7.
- The stronger the alkali, the higher the pH number.
- Alkalis turn red litmus paper blue.
- They turn universal indicator dark blue or purple if they are strong, and blue-green if they are weak.