Acids are substances that, when dissolved in water, produce hydrogen ions (H⁺). According to the Arrhenius definition, an acid is a compound that increases the concentration of H⁺ ions in solution. In simpler terms, acids have a sour taste – think citric acid in lemons or acetic acid in vinegar. In general, the smaller and more highly charged the cation, the more acidic will it be; the acidity of the alkali metals and of ions like Ag + (aq) is negligible, but for more highly-charged ions such as Mg 2+, Pb 2+ and Al 3+, the effect is quite noticeable. Acids are substances that produce hydrogen ions (H⁺) when dissolved in water. They have a sour taste, but they should never be tasted in the laboratory because they can be harmful. Acids are substances with a pH less than 7, characterized by the ability to donate protons (H+) in water. Common sources of acids include hydrochloric acid, sulfuric acid, and organic acids like citric and acetic acid. Acidic solutions turn blue litmus paper red and typically taste sour. Other acids are weak electrolytes that exist primarily in a non-ionized form when dissolved in water. Acids have a sour taste. Lemons, vinegar, and sour candies all contain acids. Acids change the color of certain acid-base indicates. Two common indicators are litmus and phenolphthalein. Examples of acids include the inorganic substances known as the mineral acids—sulfuric, nitric, hydrochloric, and phosphoric acids—and the organic compounds belonging to the carboxylic acid, sulfonic acid, and phenol groups. Substances that tend to be acidic generally have a high concentration of hydrogen ions (H⁺) and a pH lower than 7. Common examples include beverages (like coffee and fruit juices), cleaning products, and digestive juices. Substances that tend to be acidic include citrus fruits (e.g. lemons, Oranges), vinegar, carbonated drinks, and acidic solutions like hydrochloric acid. These substances typically have a low pH. Coffee, tea, juice, soda, and wine are all acidic. Black coffee typically falls between pH 4.5 and 5, while sodas often land closer to pH 2.5 to 3.5 because of added phosphoric acid or citric acid. Wine ranges from about pH 3 to 4, depending on the grape and fermentation process. In chemistry, an acid is classified as a substance with distinctive properties. An acidic substance is sour-tasting; reacts with litmus paper, bases and metals; conducts electricity; and has a pH of less than 7.