1.  The pH scale measures the acidity of a substance.  p = potential  H = Hydrogen ions (H + ) in a water solution  What is an ion? ______________________________________ An atom that has lost or gained an electron

2.  As the percentage of H + ions increase in a solution, the acidity increases.  Acid = a compound that forms H + ions in solution with water.  Example: CO 2 + H 2 O  H 2 CO 3 (carbonic acid) Carbonic acid then dissociates into H 2 CO 3  H + + HCO 3 -  The release of H + lowers the pH of the solution.

3.  As the percentage of OH - ions increase in a solution, it becomes more base.  Base = a compound that forms OH - ions in solution with water.  Example: NH 3 + H 2 O  NH 4 + OH - The release of OH - increases the pH of the solution.

4.  The scale measures from 0 – 14.  Strong acids range from 1-3.

5.  Strong bases range from 11-14.  The scale is logarithmic.  This means each pH value below 7 is ten times more acidic than the next higher value.

6.  How much more acidic is pH 4 than pH 5? _______  How does the acidity of pH 6 compare to pH 4?_____________________ __  Freshwater fish thrive at pH 7. They die at pH 4. How much more acidic is pH 4 than pH 7? __________ 10 times 1/100 or.01 times the acidity 1000 times

7.  Stomach acid (hydrochloric acid) has a pH of <2.0  Pure water has a pH of 7.0

9.  MOST cells in the Human Body require a pH of 6.5-7.5.  If the pH is higher or lower than this, chemical reactions cannot occur.  Extremely high or low pH values generally result in complete loss of activity for most enzymes.

10.  However, each enzyme has a different “optimum” pH. This depends on where it is found in the body. Enzyme pH Optimum Lipase (pancreas)Lipase (pancreas)8.0 Lipase (stomach)*4.0 - 5.0 Lipase (castor oil)4.7 PepsinPepsin*1.5 - 1.6 TrypsinTrypsin7.8 - 8.7 UreaseUrease7.0 Invertase**4.5 MaltaseMaltase6.1 - 6.8 Amylase (pancreas)Amylase (pancreas)6.7 - 7.0 Amylase (malt)Amylase (malt)**4.6 - 5.2 CatalaseCatalase7.0 * Stomach **Intestines

12.  Rainwater in the northeast has become acidic from the mixture of water with air pollutants.  When acid rain falls, the pH of ponds and lakes in the northeast decreases.  This has a direct effect on aquatic life.

13.  Read and or discuss article from USGS (United States Geological Survey) on Acids, Bases and pH