Acids usually exhibit a sour taste, an ability to change litmus paper from blue to red, react with bases to yield a salt with water, and react with some metals to produce hydrogen gas. Examples of common household acids are lemon juice, vinegar and citric acid.
While weak acids only add a sour taste to food, strong acids are corrosive and can burn through many substances. Since acids and bases, when combined, form a salt and water, acids can neutralize bases in a neutralization reaction. The resulting salt is made with an anion of the acid and a cation of the base. The hydrogen ion of acid combined with the hydroxide ion from the base forms the water.
A substance is determined to be acidic by placing its molecules in water. If it releases a hydrogen ion when it breaks down, it is considered to be acidic. If the substance releases a hydroxide ion, it is considered to be basic.