1. Acids, Bases, & pH
TSW differentiate between acids and bases, and explain the importance of pH to organisms

2. Acids
Substances that increase the number of Hydrogen ions (H+) in solution

3. Bases
Substances that increase the number of Hydroxide ions (OH-) in solution
Substances that reduce the number H+ ions in a solution

4. pH Scale Used to measure the degree of acidity of a substance
Ranges from 0-14
pH = 7 is neutral
pH < 7 is acidic
pH > 7 is basic

5. pH of Common Substances

6. Good to know… The pH scale is a measure of H+ ions in solution
A low pH corresponds to a high concentration of H+ ions
A high pH corresponds to a low concentration of H+ ions

7. pH Scale (cont.) pH scale is logarithmic
A change of one pH number actually represents a TENFOLD change in [H+]
Example: pH 3 is 10x more acidic than pH 4
pH 3 is 100x more acidic than pH 5

8. Buffers
A weak acid or base that can react with strong acids or bases to help prevent sharp, sudden changes in pH

9. Why are buffers important?
Accept H+ ions when they are in excess
Donate H+ ions when they have been depleted
Many biological reactions produce acids and bases, therefore the presence of buffers helps to keep the pH at a constant level
Help maintain homeostasis