LAWS OF THERMODYNAMICS
"There is a game, you can’t win, you can’t break even and you can’t even get out of the game."
—Allen Ginsberg
We, like all living beings, are open systems, that is, we exchange matter and energy with our environment. For example, you take in chemical energy in the form of food and do work on your surroundings by moving, talking, walking, and breathing.
All the energy exchanges that occur within us, like your many metabolic reactions, and between us and our environment, can be described by the same laws of physics, as energy exchanges between hot and cold objects or gas molecules or whatever.
"The laws of thermodynamics are a set of laws on which thermodynamics is based. Specifically, these are four laws that are universally valid when applied to systems that fall within the constraints implicit in each. Therefore, the deep impression which classical thermodynamics made on me. It is the only physical theory of universal content, which I am convinced, that within the framework of applicability of its basic concepts will never be overthrown."
—Albert Einstein
The three laws of thermodynamics are:
FIRST LAW OF THERMODYNAMICS
The First Law of Thermodynamics, also known as Law of Conservation of Energy, states that energy cannot be created or destroyed in an isolated system.
When energy passes, as work, as heat, or with matter, into or out from a system, the system’s internal energy changes following the law of conservation of energy. Equivalently, perpetual motion machines of the first kind (machines that produce work with no energy input) are impossible.
SECOND LAW OF THERMODYNAMICS
The Second Law of Thermodynamics states that the entropy of any isolated system always increases. Understanding entropy as the thermodynamic magnitude that indicates the degree of molecular disorder of a system.
"Entropy is the price of structure."
—Ilya Prigogine
In a natural thermodynamic process, the sum of the entropies of the interacting thermodynamic systems increases. Equivalently, perpetual motion machines of the second kind, machines that spontaneously convert thermal energy into mechanical work, are impossible.
"Nothing in life is certain except death, taxes, and the second law of thermodynamics."
—Seth Lloyd
The second law of thermodynamics is a re-expression of the principle of minimum energy, according to which material systems tend to evolve in the sense in which their potential energy decreases.
"A ball rolls down an inclined plane until it finds the lowest position, which is the one with the lowest energy; A compressed spring expands to achieve a condition of minimum deformation and, therefore, of minimum accumulated energy, and a chemical reaction evolves towards states of lower energy content. If your theory is found to be against the Second Law of Thermodynamics, I give you no hope; there is nothing for it but to collapse in deepest humiliation."
—Arthur Eddington
A closed system is a system which is connected to another, and cannot exchange matter (i.e., particles), but other forms of energy (e.g., heat), with the other system. In contrast, an isolated system is a system that cannot exchange either energy nor matter outside the boundaries of the system. For isolated systems (and fixed external parameters), the second law states that the entropy will increase to a maximum value at equilibrium. If rather than an isolated system we have a closed system, where entropy (rather than the energy) remains constant, it follows from the first and second laws of thermodynamics that energy of this closed system will drop to a minimum value at equilibrium, transferring its energy to the other system.
To restate:
- The maximum entropy principle: For a closed system with fixed internal energy (i.e., an isolated system), the entropy is maximized at equilibrium.
- The minimum energy principle: For a closed system with fixed entropy, the total energy is minimized at equilibrium.
"It is a remarkable fact that the second law of thermodynamics has played in the history of science a fundamental role far beyond its original scope. Suffice it to mention Boltzmann’s work on kinetic theory, Planck’s discovery of quantum theory or Einstein’s theory of spontaneous emission, which were all based on the second law of thermodynamics."
—Ilya Prigogine
Second Law of Thermodynamics examples:
- AWS: The fastest, easiest, and cheapest to use cloud storage.
- Amazon Retail: The fastest, easiest, and cheapest way to buy non- vertically integrated products.
- Alexa: The fastest, and easiest way to get information and manage the world around you (Alexa skills).
"The increase of disorder or entropy is what distinguishes the past from the future, giving a direction to time."
—Stephen Hawking
Entropy is a measure of the disorder in a system. All systems gain entropy over time, so the Second Law of Thermodynamics says that the total entropy of both a system and its surroundings will never decrease.
Understanding entropy:
The extent to which physical changes and chemical reactions proceed is controlled by accompanying changes in energy and entropy. A thermodynamic quantity representing the unavailability of a system’s thermal energy for conversion into mechanical work is often interpreted as the degree of disorder or randomness in the system.
A lack of order or predictability; gradual decline into disorder.
"I think you should always bear in mind that entropy is not on your side."
—Elon Musk
Reactions occur when the disorder of the universe (or more simply, the reacting system and its surroundings) is increased. This is the case for exothermic reactions: heat transferred to the surroundings increases its entropy or disorder. The majority of reactions that occur under ordinary conditions are exothermic because the heat released to the surroundings causes a large increase in the disorder or entropy of the surroundings; this is usually larger than any entropy decrease that might be occurring in the system. But we can have endothermic reactions if the increase in disorder within the system is greater than the decrease in the disorder of the surroundings owing to heat transferred from the surroundings to the system. This is basically all there is to understanding the role of thermodynamics in reaction chemistry: a reaction will go if the total entropy of the system and its surroundings increases.
Waste energy is associated with all processes. This waste can be reduced, but it can never be eliminated. Anyone who says otherwise is trying to con you.
THIRD LAW OF THERMODYNAMICS
The Third Law of Thermodynamics states that the entropy of a system approaches a constant value as the temperature approaches absolute zero.
Except for non-crystalline solids (glasses), the entropy of a system at absolute zero is typically close to zero.
The third law is rarely applicable to our day-to-day lives and governs the dynamics of objects at the lowest known temperatures. It defines what is called a perfect crystal, whose atoms are glued in their positions. The perfect crystal thus possesses absolutely no entropy, which is only achievable at the absolute temperature.
The concept of entropy has also been popular in some theories defining the continuous flow of time objectively, such as the linear increase in the entropy of the Universe.
ZEROTH LAW OF THERMODYNAMICS
Beside the above, there is conventionally added a Zeroth Law, which defines thermal equilibrium.
If two systems are each in thermal equilibrium with a third system, they are in thermal equilibrium with each other. This law helps define the concept of temperature.
THEOREM
The theorem is given as a restatement of the consequences of the zeroth, first, second, and third laws of thermodynamics, regarding the usable energy of a closed system:
- There is a game. (consequence of zeroth law of thermodynamics)
- You can’t win. (consequence of first law of thermodynamics)
- You can’t break even. (consequence of second law of thermodynamics)
- You can’t even get out of the game. (consequence of third law of thermodynamics)
It is sometimes stated as a general adage without specific reference to the laws of thermodynamics.
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