Cork insulation; a complete illustrated textbook on cork insulation ...

72 CORK INSULATION
crease by its becoming cooler, heat, in a word, being con-
sidered as kinetic energy of molecular motion.
The molecular theory of heat goes one step farther and holds
that heat is in part the kinetic energy of molecular motion,
as just elaborated, and in remaining part the potential energy
of molecular arrangement. The molecular theory ef heat permits
a readier grasp of the facts concerning heat than seems
otherwise possible, and for that reason is today generally
accepted.
32.
—
Temperature.—It is a mere matter of observation that
if .several spoonfuls of ice water are added to a cup of hot
cofifee, the entire contents of the cup quickly become cooler,
the heat flowing from the hot cofTee to the cold water until a
quiescent state, in which there is no tendency to further
change of any kind, known as thermal equilihrmm, is established
between them. If the same cup is then allowed to stand in a
closed room, without outside interference or disturbance of
any kind, the heat will flow from the coffee to the cup to the
table to the air of the room until all substances in the room
settle to a state of thermal equilibrium ; and when a number
of bodies have settled to such a common state of thermal
equilibrium they are said to have the same temperature.
The transfer of heat is alv/ays from the body of higher
temperature to the one of lower temperature until those tem-
peratures are exactly the same, or until thermal equilibrium
is established between them. Temperature may be thought of
as the thermal condition of a body, or the measure of the degree
of hotness; but it must not be confused with quantity of heat.
A cup of coffee may be at exactly the same temperature as the
water in a l,0(X)-gallon hot water tank, yet the tank contains a
vastly greater quantity of heat than the cup, owing to the vastly
greater quantity of liquid held by the tank.
When a substance is hot its temperature is said to be
high, and when cold its temperature is said to be low.
33. Dissipation of Energy.—Every actual case of motion
is attended by friction and/or collision on the part of the moving
body, and that part of its energy not employed in doing
work is thus dissipated. This dissipation of energy is always
accompanied by the generation of heat, or, stated another way,