Since these
combinations are weaker than those of the water molecules, energy is
required to bring about the change. But when hydrogen burns in the
oxygen, the change is from a weaker to a stronger combination. The
stored-up energy is then given up or becomes active.
71 In the evaporation of water, the energy of the sun is stored with
reference to the force of gravity. In evaporating, water rises as a
gas, or vapor, above the earth's surface, but on condensing into a
liquid, it falls as rain. It then finds its way through streams back
to the ocean. All water above the sea level is in such a position
that gravity can act on it to cause motion, and it possesses, on
this account, potential or stored-up energy. It is because of this
energy that rapids and waterfalls are such important sources of
power.
72 Energy, like matter, can neither be created nor destroyed. It can,
however, be transferred from one body to another and transformed
from one form to another form. Whenever work is done, energy is
transferred from the body doing the work, to the body upon which the
work is done. During this process there may, or may not, be a
transformation of energy.
Pages:
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593