What neutralisation is
You know that antacid tablets, which are basic, ease the discomfort of acidity in the stomach. Why do they work?
Look again at hydrochloric acid reacting with sodium hydroxide:
HCl (aq) + NaOH (aq) → NaCl (aq) + H2O (l)
The water forms when H+ ions from the acid join OH- ions from the base. The same reaction happens in every acid–base reaction:
H+ (aq) + OH- (aq) → H2O (l)
Neutralisation
Neutralisation is H+ ions released by an acid combining with OH- ions released by a base to form water molecules.
When an acid and a base neutralise each other, the acidic properties and the basic properties both disappear.