While there are different ways to define acids and bases, the most common way to distinguish them chemically is by looking at their formula and how they react in solution:

Acids:

* General formula: Usually start with H (hydrogen), followed by a non-metal or a polyatomic ion.

* In solution: They release hydrogen ions (H+) when dissolved in water, making the solution more acidic.

* Examples: HCl (hydrochloric acid), HNO3 (nitric acid), H2SO4 (sulfuric acid), CH3COOH (acetic acid)

Bases:

* General formula: Usually contain a metal or ammonia (NH3).

* In solution: They release hydroxide ions (OH-) when dissolved in water, making the solution more alkaline (basic).

* Examples: NaOH (sodium hydroxide), KOH (potassium hydroxide), Ca(OH)2 (calcium hydroxide), NH3 (ammonia)

Important Notes:

* Not all compounds starting with H are acids: For example, H2O (water) is neutral.

* Not all compounds containing OH are bases: For example, CH3OH (methanol) is not a base.

* There are also Brønsted-Lowry and Lewis acid-base theories: These theories focus on the ability to donate or accept protons or electron pairs, respectively, which can expand the definition beyond just H+ and OH-.

In summary, while the general formula can be a helpful indicator, the defining characteristic of acids is the release of H+ ions, while bases release OH- ions when dissolved in water.