of steam increases the dough’s expansion, or
oven spring, and produces a lighter loaf.
Water and Acidity: The pH Scale
Acids and Bases Despite the fact that the
molecular formula for water is H 2 O, even
absolutely pure water contains other
combinations of oxygen and hydrogen.
Chemical bonds are continually being formed
and broken in matter, and water is no
exception. It tends to “dissociate” to a slight
extent, with a hydrogen occasionally breaking
off from one molecule and rebonding to a
nearby intact water molecule. This leaves one
negatively charged OH combination, and a
positively charged H 3 O. Under normal
conditions, a very small number of molecules
exist in the dissociated state, something on the
order of two ten-millionths of a percent. This
is a small number but a significant one,
because the presence of relatively mobile