11. Forme of Matter as Affscted by Chemical Causes. —
Though many, of the changes in the form of matter are un-
attended by any chemical action, there are also many others
whi<3h are produced by chemical caus^es. One of the most
striking examples of this we have in water. This liquid is
;comp6sed wholly of two gases chemically united. As a
large volume of steam condensed forms but a little water,
so the bulk of the gases required to form a small amount of
water. is very great. So, too, there must be great conden-
sation when the three gases of which nitric acid is composed
nnite to form that liquid. On the other hand, in some chem-
ical combinations there are great expansions of matter.
When any solid, for example, enters into the composition
of a gas, it must be expanded into a very large volume.
Thus when the solid, carbon, unites with the gas, oxygen,



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18 CHSMISTItY.
