South Bend news-times. (South Bend, Ind.) 1913-1938, 1916-11-18
Why a Gold Bottle
Breaks WhenTake
Into a Warm Room
BY Garrett p. serviss.


Kindly explain the following
phenomenon: Ar empty milk bottle
after being removed from an ice
box containing a ten cent piece of
ice. was placed on a tray near a
sink. In a short time afterward
the bottle cracked with a loud re-
port. The temperature of the room
was about IS degrees Fahrenheit.
d. J. p.
The simple incident that you de-
scribe is one Of the peepholes into
the mysteries of nature through
which few ever have the curiosity to
gaze attentively, although il is the
wonderland of SC ence that they
might see.
Milk bottles are made Of cheap.
imperfectly annealed glass, whose
molecules are frequently in a state
of tension which makes them La
bic TO lose their hold upon one an
other and fly apart whenever a
little extra force is applied.
Such a force is supplied if the
thick walls Of the bottle are strongly
and suddenly heated on one side
while they are at a low temperature
on the other side. In your case the
bottle having been thoroughly re-
frigerated, was, when removed from
the icebox. very cold both within
and without. It's mean temperature
was probably near the freezing point
of water, so that or being removed
into a room where the temperature
was IS degrees. the glass was sud
denly brought into contact with air
forty or more degrees warmer than
itself.
The cover praba0ly being on, the
warm air did not enter the bottle.
so that the heating was applied 10
the exterior alone. The consequence
was a rapid expansion of the outer
layer of the glass while the interior
remained in the relatively contracted
state induced by the cold, and the
strain thus produced in the texture
of the glass resulted in a crack
Even if the cover of the bottle was
removed, so that the warm air could
enter. the thickness of the glass
would be likely to cause cracking,
since cold glass is a poor conductor
of heat as we'll as of electricity, and
the exterior layers would warm up
so much faster than the deeper ones
that a severe strain would be pro-
duced between them.
If we were content to leave the
explanation here we should not have
made much philosophical advance
in our little study Of milk bottles.
We ought 10 go on and see how heat
is able 10 produce a strain in the in
terror of a piece of glass sufficient to
crack it asunder. why does heat ex-
pand a solid to which ii is applied?
Because what we call heat is simply
a vibratory motion of the molecules
or ultimate particles, OF which every
body consists
Moleculo. are not atoms, but are
made w f atoms. and it is by its
molecuies not by its atoms, that
every Ostance is Disseminated
from other substances. \ molecuIe
has been defined as the smallest
quantity Of a substance which can
exhibit the properties by which that
substance is identified. In q solid
the molecules are held together by a
force called molecular attraction,
which is eXerted over extremely
short distances. and if the molecules
are removed beyond such distances
they cease to attract one another
and the solid falls apart.
At the same time. all the mole
cules, even in a solid body, are in "a
state of continual vibration, and this
vibration may manifest itself TO our
senses as heat. The greater the vi
bratory agitation of the molecules
the intenser the heat. only when
substance has sunk 10 the absolute
zero of temperature is there no mo-
lecular vibration.