Final answer:
Acids have a sour taste, react with certain metals to produce hydrogen gas, and change the color of acid-base indicators such as turning blue litmus red. They are defined by the Arrhenius theory as substances that ionize to produce hydrogen ions, the Brønsted-Lowry theory as proton donors, and the Lewis theory as electron pair acceptors.
Step-by-step explanation:
How to Recognize an Acid
Acids can be recognized by a few different properties. One characteristic is the sour taste that acids possess; examples include lemons, vinegar, and sour candies. Additionally, acids also react with active metals, such as those above hydrogen in the activity series, to yield hydrogen gas. Furthermore, acids change the color of certain acid-base indicators: they turn blue litmus paper red and make phenolphthalein colorless.
From a theoretical standpoint, according to the Arrhenius definition, an acid is a substance that ionizes in aqueous solution to produce hydrogen (H⁰) ions. The Brønsted-Lowry definition extends this concept by defining an acid as a substance that donates protons (H+), and the Lewis theory describes acids as electron pair acceptors.