2. Review Definition of Acid and Bases Acid – a substance that donates an H + Base – a substance that accepts an H + Link to H+ transfer

3. Link to phet PH

4. Neutral, Acidic, Basic solutions [H + ] = [OH - ] [H + ] > [OH - ] [H + ] < [OH - ] H + H + OH - OH - OH - OH - OH - OH - OH - H + H + H + H + H + OH - OH - OH - OH - OH - H + H + H + H + H + H + H + H + OH - OH -

5. Logarithmic Scale In water, values of [H + ] and [OH - ] typically range from 1 x 10 -1 M to 1 x 10 -14 M. ( A range of 100 trillion!) The relative concentrations can be more conveniently expressed using a logarithmic scale, in which each pH unit represents factor of 10 difference in H + ion concentration.

6. Concept of a Logarithmic Scale – What is the pattern in the #’s between [H + ] and pH value?

7. Logarithms The log (base 10) is defined as: log 10 n = n Logarithmic functions can be used to solve problems of the form 10 n = A. Example #1: 10 n = 100 Log 10 n = log 100 n = 2 Example #2: Log 10 3 = 3 Log 10 -4 = -4

8. pH = - log [H + ] [H + ] pH 1 x 10 -1 pH= - log (1 x 10 -1 ) = - (-1) = 1 1 x 10 -2

9. pH = - log [H + ] [H + ] pH 1 x 10 -1 pH= - log (1 x 10 -1 ) = - (-1) = 1 1 x 10 -2 2

10. Link to phet PH

12. Importance of pH pH effects the type of reactions that occur in water and how fast they occur. Example: Your blood is buffered, meaning it is maintained over a very narrow range. If the pH becomes too acidic or neutral, proteins called enzymes that catalyze all of the chemical reactions in your body will unfold and you will die. Link to denaturation animation

13. Importance of pH – drinking water In Colorado, the safety of the drinking water in many mountains towns is greatly effected by the pH of the water. For example, in Leadville, an old mining town, if the water is too acidic it will increase the concentration of toxic, heavy metals such as lead and silver ions. If the pH is more basic (high [OH-]), then the heavy metals will precipitate out of the water (Unit 3: hydroxide salts are not soluble).