Acids and alkalis are two kinds of chemical, measured on the pH scale from 0 to 14.
pH less than 7 is acidic; pH 7 is neutral (like pure water); pH greater than 7 is alkaline. Indicators such as litmus show which is which: acids turn litmus red, alkalis turn it blue. An acid and an alkali react in neutralisation.
Remember
- pH < 7 acid · pH 7 neutral · pH > 7 alkali.
- Acid + alkali → neutralisation.