The pH Scale

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The pH Scale.

click link to see scale

http://staff.jccc.net/pdecell/chemistry/phscale.html

The concentration of hydrogen ions in a solution is very important

for living things. This is because, since the hydrogen ions are

positively charged they alter the charge environment of other

molecules in solution. By putting different forces on the molecules,

the molecules change shape from their normal shape. This is

particularly important for proteins in solution because the shape of

a protein is related to its function.

The concentration of hydrogen ions is commonly expressed in terms of

the pH scale. Low pH corresponds to high hydrogen ion concentration

and vice versa. A substance that when added to water increases the

concentration of hydrogen ions(lowers the pH) is called an acid. A

substance that reduces the concentration of hydrogen ions(raises the

pH) is called a base. Finally some substances enable solutions to

resist pH changes when an acid or base is added. Such substances are

called buffers. Buffers are very important in helping organisms

maintain a relatively constant pH.

Study the pH chart given below carefully. Note that each decrease in

pH by one pH unit means a tenfold increase in the concentration of

hydrogen ions.

pgd: revised 06/20/02