This document discusses acids and bases. It defines acids as substances that release hydrogen ions (H+) in water, and bases as substances that release hydroxide ions (OH-). Strong acids completely dissociate in water, releasing many H+ ions, while weak acids only partially dissociate. Acids have characteristics like sour taste and reacting with metals and carbonates to produce gas. Bases have characteristics like bitter taste and feeling slippery. The strength of acids and bases is measured on the pH scale, with values below 7 indicating acids and above 7 indicating bases.