Chemistry Regents Practice Test 2025 – Complete Prep Resource

Acids are defined primarily by their ability to donate protons (H⁺ ions) in a solution. This is a fundamental characteristic that fits the Brønsted-Lowry definition of acids and bases, where acids are proton donors and bases are proton acceptors. When an acid dissolves in water, it disassociates to release H⁺ ions, which can then interact with other substances in the solution, leading to the characteristic properties of acids, such as a sour taste and the ability to react with bases.

This understanding is crucial for predicting how acids will behave in chemical reactions and their interactions with various substances in aqueous environments. The other characteristics mentioned, such as the ability to conduct electricity, are true for both acids and bases due to their capacity to produce ions in solution, but they do not specifically define what an acid is. Similarly, while acids typically have low pH values, this is a result of their behavior in solution rather than a defining characteristic. Being able to donate protons is what fundamentally categorizes a substance as an acid.