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The Chemistry of Life
pH scale
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Acids, Bases & pH
1 water molecule in 550 million naturally dissociates into a Hydrogen Ion and a Hydroxide Ion
Hydrogen Ion Hydroxide Ion
Acid Base
H2O  H+ + OH-
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The pH Scale
Indicates the concentration of H+ ions
Ranges from 0 – 14
pH of 7 is neutral (equal parts H and OH)
pH 0 up to 6.9  acid … H+ released
pH above 7.1 to 14 base OH- released
Each pH unit represents a factor of 10X change in concentration
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Acids
High in H+ ions
Lower number of OH- ions
0-6.9
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5. Characteristics of acids
Taste sour
Corrodes metal
Turns litmus indicator red
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Bases
High in OH-ions
Lower in number of H+ ions pH
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7. Characteristics of bases
Tastes bitter
Feels slippery
Turns litmus blue
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8. Strength of acid and base
The closer the pH is to neutral the weaker it is.
The further away the pH is from neutral the stronger it is
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Buffers
Weak acids or bases that react with strong acids or bases
Made by the body
Prevent sharp, sudden changes in pH (keep pH neutral)
Weak Acid
Weak Base
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Acid or Base?
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