physics is essentially the study of heat, temperature,
and heat transfer. As we shall see—particularly when
we look at the Second Law of Thermodynamics—these
concepts have a far broader range of application than you may at
first imagine. All of these concepts are closely related to thermal
energy, which is one of the most important forms
of energy. In almost every energy transformation, some thermal energy
is produced in the form of heat. To take an example that by now
should be familiar, friction produces heat. Rub your hands briskly
together and you’ll feel heat produced by friction.
When you slide a book along a table, the book will not
remain in motion, as Newton’s First Law would lead us to expect,
because friction between the book and the table causes the book
to slow down and stop. As the velocity of the book decreases, so
does its kinetic energy, but this decrease is not a startling violation
of the law of conservation of energy. Rather, the kinetic energy
of the book is slowly transformed into thermal energy. Because friction
acts over a relatively large distance, neither the table nor the
book will be noticeably warmer. However, if you were somehow able
to measure the heat produced through friction, you would find that
the total heat produced in bringing the book to a stop is equal to
the book’s initial kinetic energy.
Technically speaking, thermal energy is the energy associated
with the random vibration and movement of molecules. All matter
consists of trillions of trillions of tiny molecules, none of which
are entirely still. The degree to which they move determines the amount
of thermal energy in an object.
While thermal energy comes into play in a wide range of
phenomena, SAT II Physics will focus primarily on the sorts of things
you might associate with words like heat and temperature.
We’ll learn how heat is transferred from one body to another, how
temperature and heat are related, and how these concepts affect
solids, liquids, gases, and the phase changes between the three.