1. Acids & Bases pH Scale

2. pH scale – measures how acidic or basic a solution is pH scale goes from 1 – 14 (acidic to basic) pH of 7 = neutral pH < 7 is acidic pH > 7 is basic (basic = alkaline)

3. Water Dissociation What exactly does the pH scale measure? A molecule of water can dissociate (break apart) to make one hydrogen ion and one hydroxide ion H 2 O  H + + OH -

4. Water Dissociation Why is water dissociation important? The amount of H + or OH - in a solution makes it either acidic or basic More H +  more acidic More OH -  more basic (alkaline) pH measures hydrogen ion concentration [H + ]

5. Examples

6. pH Scale The pH scale is logarithmic one unit change = 10x change in concentration of hydrogen ion A solution with pH of 6 is 10x more acidic than water (pH=7). A solution with pH of 5 is 100x more acidic than water.

7. Acids & Bases ACIDSBASES pH pH < 7pH > 7 Taste SourBitter Feel Not slipperySlippery Litmus indicator color RedBlue

8. Importance Strong acids & bases can harm living tissue Need to balance pH in environment to maintain an “optimal pH” What feature of life is this? Homeostasis!

9. Buffers Buffers help maintain a pH level They bond with H + or OH - ions in the solution If a buffer bonds with H + ions, what happens to the pH? If a buffer bonds with OH - ions, what happens to the pH? The pH increases. Solution becomes more basic. The pH decreases. Solution becomes more acidic.

10. Neutralization Reactions Chemical reaction in which acid & base react to form a salt Water can be formed also HCl + NaOH  NaCl + H2O acid base salt water

11. pH in Life pH range for human body is ~ 6.1 – 7.0 Slightly acidic to prevent bacterial/fungal growth pH of stomach can vary from 1-2 to 4-5 Stomach acid has pH of 1-2