Which of the following statements about acids is true?

The statement that acids form hydrogen ions in solution is accurate and aligns with the fundamental definition of acids in chemistry. When an acid is dissolved in water, it dissociates to release hydrogen ions (H⁺). This increase in hydrogen ion concentration is what characterizes an acidic solution, leading to a pH level that is typically below 7.

In contrast, the characteristics of the other statements highlight why they do not define acids correctly. Acids do not release hydroxide ions; rather, that behavior is specifically associated with bases. The pH of acids is generally less than 7, not greater, as a pH greater than 7 indicates a basic or alkaline solution. Finally, while many acids can exist as liquids, they can also be found in gaseous or solid states, meaning it is not accurate to say that acids are always liquid.