Two water molecules

one water molecule Hydrogen ion Hydroxide ion

H 2 O  H + + OH -

pH scale

ACIDS

Acids Strong Acids have a pH of 1- 3 Strong Acids have a pH of 1- 3 Strong acids produce lots of H + ions Strong acids produce lots of H + ions

Bases

Bases Strong Bases 11 to 14 Strong Bases have a pH of 11 to 14 lots of OH - ions Contain lots of OH - ions and fewer H+ ions

The pH Scale Review

Buffers A substance that eliminates large sudden changes in pH. Buffers help organisms maintain the pH of body fluids within the narrow range necessary for life. – Are combinations of H + acceptors and donors forms in a solution of weak acids or bases – Work by accepting H + from solutions when they are in excess and by donating H + when they have been depleted.

Why do we care about pH?

Biological pH  The pH of our stomachs are around 1-2, so that foods can be broken down  The optimal pH for healthy skin and scalp is around 5 slightly acidic for resistance to infection and diseases  Soaps and shampoos are basic and thus can cause drying of the skin and scalp  When you see a “pH-balanced” shampoo or soap, the manufacturer has lowered the pH so its closer to normal skin pH  Most organisms have an internal pH of

Acid Precipitation Rain, snow or fog with more strongly acidic than pH of 5.6 West Virginia has recorded 1.5 pH East Tennessee reported 4.2 in 2000 Occurs when sulfur oxides and nitrogen oxides react with water in the atmosphere – Lowers pH of soil which affects mineral solubility – decline of forests – Lower pH of lakes and ponds – In the Western Adirondack Mountains, there are lakes with a pH <5 that have no fish.

Acid Precipitation