BODY-REGULATING FOOD: WATER

LESSON VII


WATER AND BEVERAGES (A)

EXPERIMENT 6: THE DISSOLVING POWER OF WATER.--Put 1/2 teaspoonful of salt
in a test tube, half fill it with water. Cover the mouth of the test tube
with the thumb, then shake the tube. Do the contents become clear? Set the
tube aside for a few minutes. Does the salt separate from the water?

When a solid substance, by mixing with water, disappears in the water and
does not separate on standing, the solid substance is _dissolved_.
The salt was therefore dissolved in cold water, or it may be said that
salt is _soluble_ in cold water, or that water is a _solvent_ of
salt.

SOLUTION AND DIGESTION.--The change of foods in the body from insoluble to
a soluble form is one step in digestion. Foods are dissolved in the
digestive juices of the mouth, stomach, and intestines. Some foods such as
salt and certain sugars are readily dissolved. Other foods have to undergo
changes before they will dissolve. Corn-starch, for example, does not
dissolve in cold water. It must be changed into sugar (which is easily
dissolved) in the process of digestion. Dissolving then is an important
step in the process of digesting.

USE OF WATER IN THE BODY.--A person might live for a number of weeks
without eating food, but he could live only a few days without drinking
water. Water has many uses in the body.