Final answer:
Substances that release hydrogen ions in solution are called acids, with strong acids ionizing completely and weak acids only partially. The Arrhenius, Brønsted-Lowry, and Lewis theories provide different perspectives for identifying and understanding acids and bases.
Step-by-step explanation:
Substances that release hydrogen ions when they are dissolved in water are called acids. According to the Arrhenius definition, an acid is a substance that ionizes in aqueous solution to produce hydrogen ions (H+), which are capable of participating in chemical reactions. Some acids like hydrochloric acid (HCl) are strong and ionize completely, releasing all their hydrogen ions into the solution, while others like acetic acid in vinegar are weaker and do not ionize fully.
The other theories that define acids and bases include the Brønsted-Lowry definition, which sees acids as proton donors, and the Lewis theory, which defines acids as electron pair acceptors. These definitions encompass a broader range of substances and allow for a more thorough understanding of acid-base chemistry.