Here's why:

* Acids release hydrogen ions (H+) in solution.

* Bases release hydroxide ions (OH-) in solution.

* When they mix, the hydrogen ions and hydroxide ions react to form water (H2O). This reaction is highly exothermic (releases heat).

* The remaining ions in solution form a salt.

Example:

* HCl (strong acid) + NaOH (strong base) → NaCl (salt) + H2O (water)

The reaction results in a neutral solution because the strong acid and strong base have neutralized each other.