LAWS
OF THERMODYNAMICS
I. INTRODUCTION
A. Energy
1. The total quantity of energy available in the
universe is constant.
2. The system is that part of the universe
that we have under study and with whose properties we are concerned at that
movement.
3. The surroundings are the rest of the
universe we are not studying at this time.
B.
Thermodynamics
1. Chemical thermodynamics is a study of
the energy transformations that occur in the system and any transfer of energy
that may occur between the system and the surroundings.
2. Fundamental laws which apply to all
systems:
a. Systems tend to attain a state of minimum
potential energy.
b. Systems tend toward a state of maximum
disorder.
(1) A system tends to become less orderly because there are
so many more ways to
be disorderly than to be
orderly.
(2) The probability for a system to become more disorderly or
more random is
greater than for it to
become more orderly.
(3) In a practical sense, thermodynamics is concerned with
the amount of energy in
the form of work which can
be obtained from a system when some of its energy
is transformed into heat
energy and transferred to the surroundings.
II. LAWS OF THERMODYNAMICS
A. First Law
1. Usually
called the "Law of Conservation of Energy."
2.
"The total amount of energy in the universe is constant."
B. Second Law
1. "In
any spontaneous change the entropy of the universe increases."
2. The randomness, or the amount of disorder, of
a system can be measured quantitatively and is referred to as the entropy (S)
of the system.
C. Third Law
1. "The entropy of any pure, perfect
crystalline substance at absolute zero (0°K) is equal to zero."
2. This means for this substance, at this
temperature, there is no disorder.
3. For an impure substance, all molecular motion
has also stopped, but the impurity can be distributed in different ways, giving
rise to disorder.