The functional group in carboxylic acids is -COOH. When a carboxylic acid dissolves in water, a small fraction of its molecules split up to release hydrogen ions, so the solution has typical acidic properties. Because only a few molecules split, carboxylic acids are weak acids.
A solution of a carboxylic acid has a pH below 7. It turns universal indicator orange or red, though not as strongly red as a strong acid of the same concentration.
It reacts with reactive metals to give a salt and hydrogen gas, for example ethanoic acid and magnesium make magnesium ethanoate and hydrogen. It reacts with carbonates to give a salt, water and carbon dioxide. It also reacts with an alkali such as sodium hydroxide in a neutralisation reaction, making a salt and water. Salts of ethanoic acid are called ethanoates.