On Food and Cooking

by the dissolved particles, which interfere
with the water molecules as they change phase
from liquid to gas or liquid to solid. In the
case of the boiling point, the solution contains
sugar molecules or salt ions that also absorb
heat energy, but cannot themselves turn into a
gas. So at water’s normal boiling point, there
is a smaller proportion of molecules with
enough energy to escape from the liquid and
form a bubble of vapor, and the cook has to
add more energy than usual in order to get
those bubbles to form. The boiling point and
freezing point rise and fall predictably as the
concentration of dissolved sugar or salt
increases, a fact that is handy for making both
sugar candies and ice creams.
It’s true that adding salt to water raises its
boiling point, and so speeds cooking.
However, it takes one ounce of salt in a quart
of water — around the salinity of the ocean —
to raise the boiling point a negligible 1ºF. A
Denverite who wanted to boil water at the