Acids, Bases, and pH Acids • • • • • Release H+ ions – so are called proton donors Contain H as the first element in the formula Taste sour Conduct electricity Corrosive – will steadily eat away at a substance • Causes changes in an indicator Bases • • • • • • Releases hydroxyl (OH)- ions – proton acceptor Contains (OH)- as the last set of elements Bitter taste, slippery feel Conducts electricity Corrosive Causes changes in an indicator Indicators • Changes color in the presence of certain substances • Examples – pH paper – Litmus paper (red or blue) – Phenolphthalein Litmus • In an acid, litmus paper will appear pink, in a base, it will appear blue pH Paper • Has a variety of colors indicating specific pH ranges for the material. From dark red for acids to dark blue for bases. Acid or Base Strength • The more likely a compound is to release H+ or (OH)- ions, the stronger it is. • Even if a very strong acid or base (HCl or NaOH) is diluted with water, so it becomes less dangerous, it is still a strong substance. Concentration • The word concentration is a bit like the word crowded. Low concentration High concentration Dilute vs Concentrate Concentrate Low concentration High concentration Dilute pH Scale • • • • Measures concentration of H+ ions. pH<7 - acidic pH>7 - basic pH = 7 - neutral Title, Purpose, Materials, and Safety Title – Acid activity Purpose – To gain experience determining the pH of various substances using litmus paper and pH paper. Materials – ph Paper, Litmus Paper, forceps Safety – 1. Do NOT touch substances in beakers 2. You must wear goggles Procedure 1. Gather Materials 2. You will be assigned to one station, using the forceps, dip a piece of red litmus paper into the substance at that station. Record color. 3. Repeat with blue litmus. 4. Switch stations when told. 5. One of the stations will involve pH paper, make sure you do not use the litmus paper at that station. Substance Orange Juice NaCl + H2O Distilled H2O Vinegar Drano Sugar + H2O Aspirin + H2O Tea Lemon Juice Ammonia Baking Soda + H2O H2O2 Maalox Red Litmus Color Blue Litmus Color Acid or Base?