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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 (0K) 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.