acids and bases

Acid:chemical substance whose aqueous solutions are characterized by a sour taste, the ability to turn blue litmus red, and the ability to react with bases and certain metals (like calcium) to form salts. Aqueous solutions ofacidshave a pH of less than 7

Base:substances that, in aqueous solution, are slippery to the touch, taste bitter, change the color of indicators (e.g., turn red litmus paper blue), react with acids to form salts, and promote certain chemical reactions (basecatalysis).