Recently
there have been some comments on Facebook and elsewhere explaining why hot
water freezes more rapidly than cold water. Since hot water does not freeze
more rapidly than cold water, these comments allow us to think about the nature
of heat, and the use of a scientific theory.
Heat and
temperature are related but different phenomena. Heat refers to the quantity of
energy of a particular kind in a lump of matter of a particular size.
Temperature talks about the distribution of heat in a lump of matter regardless
of size. That is, a large cup of coffee may have the same temperature as a
small cup of coffee, but the large cup has more heat than the small one.
In my high
school physics class, our teacher explained that the amount of heat generated
by an engine was a constant – regardless of where the heat went. One of the
students asked, “Then how come drag racers put wide tires on the back? Wouldn’t
the heat be the same whether the tires were large or small?” The class was
stumped for a moment. The answer is that since the amount of heat is the same,
distributing it through a broad tire would cause less of a rise in temperature
than distributing it through a small tire. Since the total amount of heat was
the same, putting it into a larger volume of matter would cause less of a
temperature change – the bigger tire wouldn’t melt.
The same
argument applies to the freezing phenomenon. The classic conundrum states that
if you put a cup of hot water next to a cup of cold water in a freezer, they
both freeze at the same time. This means that the hot water froze faster than
the cold water.
This is an
example of a flawed theory. A scientific theory offers an explanation of an
observed phenomenon that can be disproved. In the case of the freezing water,
the idea that the hot water freezes more quickly can be disproved simply by
placing the hot water in the freezer, and seeing how long it takes to freeze;
then putting the cold water in the freezer, and seeing how long it takes to
freeze. While the hot water is cooling, at some point it will have the same
temperature as the cold water. From that point, the question is how rapidly
will two identical amounts of water, at the same temperature, take to freeze. The
water’s history doesn’t matter. When the hot water and the cold water are in
the same freezer, the hot water warms up the cold water while the freezer
removes heat from all its contents.
A theory
that cannot be disproved is not a scientific theory. The theory of evolution,
like the theory of gravity, explains an observed set of phenomena and allows
for predictions that can be either validated or disproved. Dismissing “a mere
theory” because it is only a theory is fine. Dismissing a scientific theory as
“a mere theory” is thoughtless.